Nrri Digital Logs TR 2003 21 PDF

EXPLORATION DRILL HOLE LITHOLOGY,
GEOLOGIC UNIT, COPPER-NICKEL ASSAY,

AND LOCATION DATABASE FOR THE
KEWEENAWAN DULUTH COMPLEX,
NORTHEASTERN MINNESOTA
Richard Patelke
with assistance from Mark J. Severson,

Steven A. Hauck, Lawrence M. Zanko, Stephen Monson Geerts,
and Dean M. Peterson
October 2003
Technical Report
NRRI/TR-2003/21
Funded by the Permanent University Trust Fund
Project No. 783-1048, 5601214
Natural Resources Research Institute

University of Minnesota Duluth
5013 Miller Trunk Highway
Duluth, MN 55811-1442
SUMMARY
This report and database compiles virtually all publically available drill hole location data, lithological
logging data, copper-nickel assay data, and rock quality data for about 2,145 exploration drill holes
in and near the Keweenawan Duluth Complex in northeastern Minnesota. This database covers about
1,779,600 feet of drilling over about 70,000 lithological, and about 70,000 separate assay intervals.
All of this drilling is in St. Louis, Lake, and Cook counties.
The digital data are presented in an industry standard (Gemcom for Windows) exploration and mine
modeling software format, as well as spreadsheet and comma-delimited files for use in other
programs. This format can be adapted for use in a GIS program such as ArcView.
The purpose of this report is to make these data available to mineral exploration companies in a
format almost immediately usable by them.
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TABLE OF CONTENTS
SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
INTRODUCTION AND BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
PURPOSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Assumptions and Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
DISCLAIMERS AND DATA ISSUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
USER ASSUMPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Metadata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Company Logging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Absent Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
FUNDING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
DATA FORMATS, DATA TABLE LISTING, AND SHORT EXPLANATIONS . . . . . . . . . 10

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Data Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Data File Sizing, Splitting, and Naming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Drill Hole Numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Data Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Drill Hole Coordinate and Location Comments . . . . . . . . . . . . . . . . . . . . . . . . . 13
DATA TABLES-SHORT DESCRIPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Common Elements in All Data Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Desurveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Column Order in Data Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
HEADER Table-Short Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
HEAD-F-T Interval Table For Header Data-Short Description . . . . . . . . . . . . . 17
SURVEY Table-Interval Table-Short Description . . . . . . . . . . . . . . . . . . . . . . 18
LITHO Interval Table-Short Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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ASSAY Interval Table-Short Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
RQD Interval Table-Short Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
PGE-ETC Interval Table-Short Description . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
APPENDICES 1 THROUGH 8 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
FILE NAMES AND CONTENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
DATA ENTRY AND RECONCILIATION DETAILS . . . . . . . . . . . . . . . . . . . . . . . . 32
APPENDIX 1: HEADER TABLE FORMAT AND EXPANDED DESCRIPTION FOR

GEMCOM DATABASE (GCDBDC.MDB) AND SPREADSHEET FILES
(HEADER.XLS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
HEADER TABLE INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
DRILL HOLE NUMBERING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
DRILL HOLE LOCATION BY X, Y, AND Z COORDINATES . . . . . . . . . . . 35
DRILL HOLE DEPTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
DRILL HOLE ORIENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
DRILL HOLE LOCATION BY PUBLIC LAND SURVEY (PLS),
COUNTY, AND QUAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
GEOLOGIST(S), CROSS-SECTIONS, GRIDS, and DATE . . . . . . . . . . . . . . 39
OVERBURDEN THICKNESS AND FOOTWALL DEPTH . . . . . . . . . . . . . . 41
METADATA AND RECORD KEEPING ENTRIES . . . . . . . . . . . . . . . . . . . . 42
INTRUSION AND DEPOSITS REVIEWS . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Introduction to Intrusions and Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
INTRUSION DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
DEPOSIT DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
DULUTH LAYERED SERIES (DLS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Duluth, Fish Lake, and Twig Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
BOULDER LAKE INTRUSION (BLI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Boulder Lake South (Grid V ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Boulder Lake Central (Grids VI and VII) . . . . . . . . . . . . . . . . . . . . . . . 48
Boulder Lake North (Grid IV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Grid VIII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
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WESTERN MARGIN INTRUSION (WMI) . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Boulder Creek (Grid I) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Marshall Trail (A.K.A. Section 34) . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Harris Lake Drill Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
CV Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Cloquet Valley North . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Linwood Lake Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Whiteface Reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Otto Lake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
DULUTH COMPLEX ANORTHOSITIC SERIES (AS) . . . . . . . . . . . . . . . . . 51
Bear Lake Inclusion Drill holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Thomson Lake (Grid X) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
PARTRIDGE RIVER INTRUSION (PRI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Water Hen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Skibo-South (Grid II) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Skibo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Section 22 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Allen Exploration Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Wyman Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Wetlegs and Wetlegs West . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Section 17 OUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Longear OUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Longnose OUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Dunka Road (NorthMet) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Babbitt (MinnAMAX or Mesaba) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
VIRGINIA FORMATION DRILL HOLES . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
SOUTH KAWISHIWI INTRUSION (SKI) . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Serpentine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Dunka Pit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Birch Lake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Little Lake Road (Birch Lake North) . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Maturi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
South Filson Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Spruce Road . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Highway 1 Corridor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
BALD EAGLE INTRUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
MISCELLANEOUS INTRUSIONS–GUNFLINT CORRIDOR . . . . . . . . . . . . 62
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MISCELLANEOUS INTRUSION–INTERIOR DULUTH COMPLEX . . . . . . 63
Greenwood Lake Intrusion (GLI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Osier Lake Intrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
BEAVER BAY COMPLEX AND NORTH SHORE VOLCANIC GROUP . . . 63
Milepost 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Sonju Lake Intrusion (SLI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Cloquet Lake Layered Series (CLLS) . . . . . . . . . . . . . . . . . . . . . . . . . . 64
APPENDIX 2: SURVEY TABLE FORMAT AND EXPANDED DESCRIPTION FOR

GEMCOM DATABASE AND SPREADSHEET FILES (SURVEY.XLS) . . . . . . . . . 65
SURVEY TABLE INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
SURVEY DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
APPENDIX 3: LITHO (LITHOLOGY) TABLE FORMAT AND EXPANDED

DESCRIPTION FOR GEMCOM DATABASE AND SPREADSHEET FILES (EAST-
LITH.XLS & WEST-LITH.XLS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
LITHO TABLE INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
LITHO (LITHOLOGY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
ROCKTYPE-LOGGED ROCKTYPE BY ABBREVIATION CODE . . . . . . . 70
Modifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Rock Names Not Covered By The Modified Phinney Diagram . . . . . . . 73
Massive Sulfide (MS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Semi-Massive Sulfide (SMS) . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Granophyre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Massive Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Semi Massive Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Norite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
OUI (Oxide-bearing Ultramafic Intrusion) . . . . . . . . . . . . . . . . . 75
Hornfels (H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Footwall Cordieritic Metasediments . . . . . . . . . . . . . . . . . . . . . . 76
Disrupted Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Recrystallized Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Graphitic Argillite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Bedded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Virginia Formation undivided . . . . . . . . . . . . . . . . . . . . . . . . . . 76
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MG and V SILL (Virginia Sill) . . . . . . . . . . . . . . . . . . . . . . . . . 76
Biwabik Iron Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Mixed Duluth Complex (MX***) . . . . . . . . . . . . . . . . . . . . . . . 78
Logging Differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
EXP-RTYPE-logged rocktype-full name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
CON-RTYPE-EXAMPLE OF CONSOLIDATION OF ROCKTYPE . . . . . . . 78
UNIT-CROSS-SECTION (MAP) UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Footwall rocks units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Hanging wall rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
DISTANCE TO FOOTWALL MEASUREMENTS . . . . . . . . . . . . . . . . . . . . . 81
APPENDIX 4: ASSAY (COPPER-NICKEL ASSAYS) TABLE FORMAT AND EXPANDED

DESCRIPTION FOR GEMCOM DATABASE AND SPREADSHEET FILES (EAST-
CUNI.XLS & WEST-CUNI.XLS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
ASSAYS INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
COPPER-NICKEL ASSAY DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
APPENDIX 5: RQD (ROCK QUALITY DESIGNATOR) TABLE FORMAT AND

EXPANDED DESCRIPTION FOR GEMCOM DATABASE AND SPREADSHEET
FILES (RQD.XLS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
RQD INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
APPENDIX 6: PGE, WHOLE ROCK, AND TRACE ELEMENT DATA FOR DULUTH
COMPLEX DRILL CORE SAMPLES (TAKEN FROM SEVERSON AND HAUCK,
2003) TABLE FORMAT AND EXPANDED DESCRIPTION FOR GEMCOM
DATABASE AND SPREADSHEET FILES (PGE-ETC.XLS) . . . . . . . . . . . . . . . . . . 87
PGE DATA INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Assays PGE and Others Table-Short description . . . . . . . . . . . . . . . . . . . . . . . . 88
APPENDIX 7: DULUTH COMPLEX DRILL HOLE NUMBERING GENERALITIES . . . . 90

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Drill Hole Numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
APPENDIX 8: USEFUL CONTACT INFORMATION FOR DULUTH COMPLEX MINING

AND EXPLORATION ISSUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
For general data issues, and geologic questions . . . . . . . . . . . . . . . . . . . . . . . . . 95
For initial mineral leasing information questions . . . . . . . . . . . . . . . . . . . . . . . . 95
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For general tax questions related to Minnesota mining . . . . . . . . . . . . . . . . . . . 95
For information about economic development issues in northern Minnesota . . . 96
For regional geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
Trade groups related to exploration and mining in Minnesota . . . . . . . . . . . . . . 96
For exploration and mining permitting and environmental review information . . 97
Drilling regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
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LIST OF TABLES
Table 1. Listing of deposit areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 2. General format of common fields in interval data tables. . . . . . . . . . . . . . . . . . . . . . . 14
Table 3. Format of Header Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 4. Format of Survey Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 5. Format of Lithology Data Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 6. Format of Assay Data Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Table 7. Format of RQD Data Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 8. Format of PGE-ETC Data Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 9. Repeat listing of deposit areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
viii
LIST OF FIGURES
Figure 1. Schematic of data layout and table relationships in Gemcom database . . . . . . . . . . . 10

Figure 2. Generalized map of Duluth Complex, complete caption on next page. . . . . . . . . . . . . 45
Figure 3. Modified Phinney (1972) diagram for rock unit classification . . . . . . . . . . . . . . . . . 71
CD-ROM WITH DATABASE, PDF FILE OF THIS REPORT

AND ALL DATA FILES ARE IN BACK POCKET
ix
INTRODUCTION AND BACKGROUND
INTRODUCTION
This report centers on a digital compilation of all drill core logging done in the Duluth Complex
(Complex) by the Natural Resources Research Institute of the University of Minnesota Duluth
(NRRI), as well as company logging for drill holes that NRRI geologists have not logged (about
2,145 drill holes total). Drill holes not logged include many drill holes with no core available. For
drill holes with no core and/or sparse documentation, we included what we do know as a place
keeping record within the database. This lithologic data is presented with publically available
location, copper-nickel-sulfur assay, and downhole survey data for these drill holes in a
comprehensive industry standard database format (Gemcom for Windows database and as separate
Microsoft Excel and comma-delimited files for each database table; see CD-ROM in back pocket and
detailed descriptions in Appendices 1 though 6). The total drill hole count varies depending on how
one treats wedges and “placeholder data” inserted for drill holes with little documentation.
This database and report assumes familiarity with Duluth Complex geology and geography on the part
of the user. The data was entered as we would enter it for our own use in Excel, Gemcom, or other
geologic modeling programs.
This report can be considered to be a continuation of a portion of Minnesota Geological Survey

(MGS) Report of Investigations 58, “Geology and Mineral Potential of the Duluth Complex and
Associated Rocks” (Miller et al., 2002), which includes a GIS-based compilation geologic map of the
Duluth Complex. That map is available as a separate publication (MGS Miscellaneous Map 119,
Miller et al., 2001). Much of that mapping is based on the same data as listed in this database.
Report of Investigations 58 (RI-58) with its associated GIS database is available from the Minnesota
Geological Survey on-line at http://www.geo.umn.edu/mgs/.
PURPOSE
Introduction
The purpose of this project was the digital compilation of drill hole-based lithological data for the
Duluth Complex. The original intent was to only record drill holes that NRRI had logged. The
project was expanded to include all available Duluth Complex drilling records and Beaver Bay
Complex drill holes (about 2,145 drill holes). It became apparent early on in the process that the final
product would be much more useful if these data were tied to existing available location and assay
data. The majority of time on this project was spent on the lithology and location data, with the only
time spent on the assays being the reformatting of previous work.
The intention of this database is to give easy access to Duluth Complex drill hole-derived lithological
data, as well as a basic set of copper-nickel-sulfur assay data, for regional exploration purposes. For
the most part this drilling is localized in a series of moderate-sized to world class- size copper-nickel
(plus PGE) deposits and smaller massive-oxide deposits (deposit is used in this report with no
1
economic connotation). While some of the larger deposits are currently under lease (Dunka
Road/NorthMet, Babbitt/MinnAMAX/Mesaba, Birch Lake, Maturi Road, Spruce Road, and South
Filson Creek), no major publically reported new work has been done to move these projects from
exploration to development. These data reflect that much ground is available for exploration and
development.
Assumptions and Goals
The final purpose is then to compile a database that:
1) can be used in mine modeling or GIS software with little or no modification;
2) can be used in spreadsheet format for certain analyses;
3) can be expanded or filled in with more refined (or new) information with ease, and without
having to modify any other original data in the package;
4) makes these data easily available to as many interested parties as possible;
5) ties all of the NRRI work together in a way that work on the Complex can go forward
without ever recreating this dataset;
6) keeps the interpretive (lithological and map unit) data separate from the assay and location
data;
7) assumes the user has the skill to break out whatever subsets of data they need;
8) accounts for the entire length of the drill hole, i.e., there are generally no breaks in the data
format, though there may be breaks in the data itself (unsampled or undescribed intervals are
all listed as such);
9) reasonably cross-references with the data in Miller et al. (2002);
10) contains at least a minimal record for every known drill hole in the Complex. Note that
there may be some drill holes omitted from this dataset if the drilling was done prior to the
Minnesota Department of Natural Resources (MDNR) data submission requirements, and
thus, have no public record whatsoever. We think that this is only a marginal possibility.
There are also about 500 Minnesota Department of Transportation geotechnical drill holes
located in St. Louis, Lake, and Cook counties. These are rotary and/or core drill holes with
sample or records stored at the MDNR in Hibbing. Some of these geotechnical drill holes
may penetrate the Duluth Complex, North Shore Volcanic Group, or Beaver Bay Complex.
We have not assessed any data about these geotechnical drill holes and no further reference
is made to them in this report or dataset. The user should see the MDNR drill core library
index for more information;
2
11) assumes a familiarity of the user with the geology of the Duluth Complex (and associated
units), the terminology of rock types and map (cross-section) units, and general geography
of the drilling data. In such a large dataset there are a large number of drill core intervals that
don’t neatly fit the classification schemes of the majority, as there are always exceptions to
the rule. The user needs to be able to recognize these exceptions in filtering and manipulating
the data. This database and report is not the venue to describe the geology of these units in
depth nor solve the many geologic problems yet to be addressed in the Complex. See the
short listing of available reports on the Complex in the User Assumptions section below.
The familiarity issue matters because the dataset will allow the user to find such things, as for
instance, all drill holes that intersect the Giants Range batholith rocks or massive-oxide
intervals in the Complex. Overall however, these are very small percentages of the total
drilling intercept, and the data as formatted here will not be much use in examining these
smaller percentage units, because the more subtle differences in these unique units are not
covered in this dataset. Once again, the user needs to use their familiarity to go to the original
logs and probably to the core itself to answer specific questions.
At the same time, the availability of these data will trivialize the effort needed to answer
certain questions, such as: what percentage of the drill core has been sampled for copper-
nickel analysis, the percentage of norite within four hundred feet of the basal contact, the
locations of the highest copper-nickel values in the Duluth Complex, and numerous other
questions.
3
DISCLAIMERS AND DATA ISSUES
USER ASSUMPTIONS
There are some critically important overriding assumptions that must be recognized in using this data:
1) The user must have familiarity with Duluth Complex geology and geography, and is
assumed to have read or have access to:
Minnesota Geological Survey Report of Investigations 58 (RI-58) by Miller,

Severson, Hauck, Green, Chandler, Peterson, and Wahl, 2002, for the most recent
overview of the geology and mineral potential of the Duluth Complex (Miller et al.,
2002). The database in this report could be integrated into the GIS database included
in the MGS report, and much of the intrusion description referenced here also comes
from that report. This is the most current published document available for the entire
Duluth Complex and Beaver Bay Complex and contains extensive references for
Keweenawan and Midcontinent Rift geology;
Mark Severson’s 1995 report on the South Complex area, from the Mesabi Range to
Duluth (Severson, 1995). The drilling area descriptions for the western edge of the
Complex in this report were derived from that document;
Reports on the general igneous stratigraphy of the Partridge River intrusion by

Severson and Hauck (1990, 1997);
Babbitt (MinnAMAX or Mesaba) area reports by Severson et al. (1994, 1996);

Severson and Barnes (1991); Patelke (1994), which includes assay data and an
inventory of drill hole specific data for Babbitt and Serpentine deposits; geologic maps
by Severson and Miller (1999), and Miller, Severson, and Foose (2002). Some of
these reports have extensive cross-sections included, and all contain geologic
descriptions;
Steve Geerts’ reports and thesis on the Dunka Road (NorthMet) deposit (Geerts,
Barnes, and Hauck, 1990; Geerts, 1991, 1994). These reports include numerous
cross-sections and are the best publicly available work on the Dunka Road
(NorthMet) deposit;
Severson’s South Kawishiwi intrusion report (1994), especially for the cross-sections;
The Zanko, Severson, and Ripley (Zanko et al., 1994), report on the Serpentine
deposit, for cross-sections and relations of the Grano Fault to mineralization;
Dean Peterson’s “Project 317" done for the MDNR in 1997, maps much of the
copper-nickel assay chemistry across the Complex, and his recent reports for the
NRRI refine these concepts and data presentation (Peterson, 1997, 2002);
4
Morton and Hauck (1987) summary report on PGEs in the Complex;
Severson and Hauck (in prep., 2003) review of PGE mineralization in the Complex,
with some newer assays;
Hauck, et al. (In prep.) For petrography of the Birch Lake deposit;
and, Hauck et al. (1997), a Geological Society of America review paper with
extensive references.
There are a great number of other reports and papers on the Duluth Complex. Steve
Hauck of the NRRI has developed a searchable, keyworded, bibliography of
Midcontinent Rift geology. This bibliography is constantly being updated, and Mr.
Hauck’s contact information is in Appendix 8;
2) The digital data are not substitutes for the original logs, nor should they substitute for
future logging. We did not throw out the original logs and would use them first ourselves in
re-examining an area;
3) The NRRI lithologic drill logs used here to develop the database are somewhat narrative,
intended mostly to assist us in the drawing of cross-sections at scales from one inch equals
two hundred feet to one inch equals fifty feet. The coding here (described later in the
database format section and Appendix 3) is at best less informative than the complete logs as
they were written and generally represents the consolidated information one would see on
cross-section. In other words, the data in the digital files are an interpretation of an
interpretation;
4) These data were formatted on the premise that the users would be very familiar with either
a drill hole-based modeling and database program, i.e., Gemcom, MedSystem, DataMine; or
in the case of using these data in spreadsheet format, Microsoft Excel filters and subtotal
tools;
5) There is a large amount of data here, but it would be incorrect to assume that these data
represent the overall geology, lithology, or assay geochemistry of the entire Duluth Complex.
At best, these data should be used as representing the geology in and near the deposits and
exploration areas as listed. The majority of the Complex has not been mapped in detail nor
drilled, and most of the drilling is in areas of visible copper-nickel or massive-oxide
mineralization;
6) Lastly, as discussed in Miller et al. (2002), the MGS and USGS sponsored the collection
and compilation of statewide aeromagnetic data in the 1980s (Chandler, 2001). These data
have since become an integral part of any regional geologic work on the Complex. The
digital data (and paper maps for some areas) are available from the MGS. The MDNR Lands
and Mineral Division has reformatted the aeromagnetic data for GIS use. Those doing
exploration studies in northeastern Minnesota should seek out and use these data. Contact
information for both agencies is in Appendix 8.
5
Metadata
There is limited formal metadata in this report or in the database. The reporting does not try to
document every data source because virtually every record listed in these data files is in the paper files
at the NRRI or the MDNR. The lithology and map unit data are generally from our own logging and
the compilation of cross-sections, mostly published. Nearly everything else comes from copies of
original company logs, assay sheets, driller reports, composite sheets, short memos, and reports, etc.
We have used our best geologic judgment when faced with conflicting information in the paper files.
Probably much less than 1% of the information herein is not on file at NRRI or MDNR. Currently,
the work involved in documenting and inventorying all items in the NRRI and MDNR paper files isn’t
justified in terms of improving the final database product or of our understanding of the Duluth
Complex.
A second reason to limit the included metadata is that some of the data in this project is pieced
together from earlier digital compilations (notably the assays and parts of the header file data). It
must be assumed that the original work was conscientious. Also, much of the data used here results
from applying some judgement (learned from familiarity with the paper copies of the data) in deciding
which part of conflicting or multiple data to use for a particular interval or drill hole.
Should a situation arise (as it has in the past) where better documentation of the data source is
required, the staff geologists at the NRRI and MDNR are more than willing to help with detailing
documentation for specific areas of the Complex. Contact information for these individuals and
organizations is listed in Appendix 8.
Company Logging
Where we utilized company logging information, we tried to minimize our interpretation of their rock
naming conventions to those that were clear, usually based on our knowledge from surrounding drill
holes or familiarity with the company scheme. Rock units (geologic cross-section or map units as
opposed to rock type) from company logs have seldom been used. We either fit units to our naming
scheme where very obvious or classed these units as “mixed”, as with “MXDC” for undivided Duluth
Complex, “MXPRI” for undivided Partridge River intrusion, “MXSKI” for undivided South
Kawishiwi intrusion, etc. This approach is legitimate, as much of the current subdivision of igneous
rock units in the drilled areas of the Duluth Complex has been defined over the past fifteen years by
NRRI geologists or from MGS mapping projects.
Absent Data
The data entry and data reconciliation for this project took over 2,000 hours. Therefore, time
constraints mean that much of the drill hole interval-related data that could be in these data files is
not. These data could be added later by an interested user. These data are mostly items that would
require other sets of intervals, in that they overlap the rock type, unit, and assay data intervals listed
here. These absent interval data include such items as: alteration, i.e., saussurization, uralitization,
serpentinization, chloritization; chlorine drops (what type and any record of what mineral they are
growing on); grain size (except for pegmatitic); mineralogy (no mineral percentages are directly
recorded here); magnetism (either relative or measured with a susceptibility meter); sulfide mineral
6
percentage estimate; sulfide mineralogy type (though this can be roughly estimated from the Cu:S
ratio); sulfide occurrence (generally disseminated unless noted as massive or semi-massive, but with
a wide range of variation); split core versus whole core remaining (which would allow for a further
check for missing assay records); and structural features such as: contact relationships, joint
orientations, and notation of the often ubiquitous serpentine and uralite veining.
However, the lithological intervals, location, survey, and assay data assembled in this database should
need no other major work at the deposit scale. Future attention can be given to adding the
components listed above, should science or economics indicate that digitizing that data will improve
our knowledge of the Duluth Complex or assist in the development of a mineral deposit.
In the future, it would be very useful to compile the available land and minerals ownership
information into this database, especially the ownership and leasing history. The history would be
useful in that there may have been work completed on some of these properties that is not publically
available. For instance, there is very little compiled geophysical information for the Duluth Complex
in the public domain relative to the amount of work that has probably been done over time. Land
owners may have records for geophysics, drilling, or sampling that the original exploration companies
did not submit to the public record.
FUNDING
This project was funded under the PUTF (Permanent University Trust Fund) program of the
University of Minnesota. This research money is generated from mining revenues and is granted in
keeping with the NRRI mission of encouraging economic development in northeastern Minnesota,
in this case by providing a dataset useful for regional mineral exploration by private companies.
ACKNOWLEDGMENTS
There is virtually nothing original in this work. This project would not have been possible (nor
necessary) without the large amounts of Duluth Complex drill core logging work done since 1988
by Mark Severson, Steve Hauck, Steve Monson-Geerts, Larry Zanko, and the lesser amounts of
logging done by James Strommer, Mary Jo Kuhns, John Heine, Jim Miller, Steve Hovis, and Richard
Patelke. Also, much of the logging and assay information for drill holes without existing drill core
was taken from company files (mostly supplied by INCO) and originally organized and/or digitized
by Dean Peterson for MDNR “Project 317" (Peterson, 1997). Many other geologists in the region
have worked on these drill holes for other agencies or companies, and their work is not quoted here,
but has been a valuable contribution to the model upon which the NRRI logging is based. The main
repository of these other records is the drill core library at the Minnesota Department of Natural
Resources-Lands and Minerals Division, Hibbing, Minnesota.
The assay work presented here has been reformatted, but was actually collected and digitized
sporadically over the last fifteen years for various reports, with much coming from Geerts (1991),
Patelke (1994), and Zanko et al. (1994). Peterson (1997) included all of the above data and filled in
most of the remainder of the South Complex area assay data and South Kawishiwi intrusion assay
7
data. This report adds in some minor scattered data, clarifies the unsampled intervals, and removes
the duplicates and overlapping intervals from previous work. Mark Severson is owed thanks for
assembling the reference files of paper copies for virtually all of the assays, which are on file at the
NRRI.
Mark Severson, recently with Jim Miller, has done the majority of the detailed surface mapping that
ties the drill holes along the basal contact at the western and northern margins of the Complex
together in a coherent geological framework. Much of Seversons work builds on work done by Bill
Bonnichsen (1971) for the Minnesota Geological Survey.
The Minnesota Department of Natural Resources must be thanked for having the presence of mind
and securing the resources to retain much of this core and the associated records. They have also
allowed easy access to core and working space for the NRRI geologists. Specifically the NRRI staff
would like to thank: Al Dzuck for his years of friendly service in the core buildings; as well as Rick
Ruhanen, Barry Frey, Dave Dahl, Marty Vadis, Daryl (Ricco) Riihiluoma, Mike Ellet, Doug Rosnau,
Tom Anderson, Mike Lubotina, Jim Sellner, Matt Oberhelman, Al Klaysmat, and the late Henk
Dahlberg.
NRRI also needs to thank all individuals and companies who have helped out over the years: John
McGoran, Don Gentry, Leah Mach, and Chris Matson of Fleck Resources (now PolyMet Mining);
Jeff Clark, Al Samis, Terry Hodson, and Jerry Zeig of Cominco (now Teck Cominco); Ernest
Lehmann, Leon Gladden, William Rowell, John Beck, and Ted Dematties of Lehmann Exploration
Management and its various joint venture partners; William Ulland of American Shield Company;
R.C. Bell and Andy Bite of INCO; Doug Hunter of Wallbridge Mining; Harrison Mattson of
Arimetco International; Dennis Hendricks and the late Cedric Iverson of United States Steel Corp.;
Dave Meineke of Meriden Engineering; Dan England and Richard Buchheit of Eveleth Fee Office;
Rhude and Fryberger; Pete Pastika, Jay Mackie, and Doug Halvorson of North Shore Mining; Stuart
Behling of the United States Forest Service; and the geologists of the Minnesota Geological Survey.
The many other companies who left the Duluth Complex exploration scene before NRRI was
involved in this work, but whose data we are now using, with much thanks, include: AMAX, Bear
Creek, Cleveland Cliffs, Duval, Exxon, Hanna Mining, Kennecott, W.S. Moore, New Jersey Zinc,
NICOR, Nerco, Newmont, Phelps Dodge, Resource Exploration, and others.
The author also extends many thanks to: Mark Severson, Dean Peterson, Larry Zanko, Steve Hauck,
and Steve Monson-Geerts of the NRRI for the huge amount of uncompensated time they have put
into disscussions about how to make this a usable product.
The author of this report is solely responsible for all errors in fact or in judgement during the
transcription of the lithological logs and other data to the digital format. Future use of this database
will show some errors and misinterpretations. Please inform NRRI staff when these errors are found.
As always, the mistakes are easiest to find by using the product.
8
RECOMMENDATIONS
This report draws no conclusions. However, it is important to realize that this is not all of the
available data about these drill holes. Future work should include:
1) entering all data to a common format as the data are developed, not later;
2) an assessment of the written logs to see if there is enough alteration data recorded to justify
the effort in transcribing the data to digital format;
3) logging (and re-logging) of the drill holes NRRI has not logged yet, which would fill in
much of the missing data;
4) reformatting the data as given here to function in ArcView, which would allow a better tie-
in with the surface mapping data;
5) entering all available whole rock and trace element data into this database;
6) re-inventorying and checking the paper files at MDNR and NRRI to make both sets are
complete, and to consolidate all data about each hole at both locations;
7) inventory and record the available thin section and polished section data, which can easily
be tied into this database by footage;
8) recheck all the assay data from the original sheets, and document these checks;
9) digitize the property ownership;
10) digitize all the geophysical work that has been done on the Complex to a common format.
11) recognizing that in all modern geologic work the expectation is that the data will
eventually be placed into a Geographic Information System and that this needs to be
accounted for in planning and executing projects.
9
DATA FORMATS, DATA TABLE LISTING, AND SHORT EXPLANATIONS
INTRODUCTION
This section contains short tables that are summary listings of all the data file formats used in either
the Gemcom relational database (GCDBDC.MDB) or the Microsoft Excel spreadsheet and comma-
delimited files (*.XLS and *.CSV) that form the core of this report. The same data, though not
necessarily in the same column order within each of the tables, is in all files or tables with the same
name.
The user should open these data files for a quick examination before reading these explanations.
Figure 1. Schematic of data layout and table relationships in Gemcom database.
Data Layout
Figure 1 is a schematic outline of the Gemcom database and its included tables. The HEADER table
contains a single record for each drill hole, with fields covering data about the drill hole in its entirety,
such as location, depth, County, USGS quadrangle map, logging geologist, etc. The other tables
generally contain multiple records for each drill hole. The SURVEY table contains the down hole
survey data for each hole in “interval” or “from-to” format. Holes with no down hole surveys are
treated as a single interval and are given their collar orientation for their entire length. The
LITHOLOGY, ASSAY, PGE, and RQD tables are “interval” or “from-to” tables for their respective
data types. The Gemcom program (and other mine modeling and exploration programs) uses the
collar location data in the header file and the down hole survey data from the survey file to locate
these down hole intervals in three-dimensional space for display or analysis.
The database table HEAD-F-T is the HEADER table converted to a “from-to” format to facilitate
transferring data from the HEADER to the SURVEY, LITHOLOGY, ASSAY, PGE, and RQD
10
tables in Gemcom. In this file, every drill hole is treated as a single interval, where “from” equals “0"
(zero) and the total depth is given as the “to” value for the entire drill hole as a single interval.
Note that the Gemcom data are in a Microsoft Access (*.MDB) database format, as this is the main
core of Gemcom. However, Gemcom does not publish table relationships for their product;
therefore, relationships would have to be defined to use this database file in Microsoft Access as a
stand-alone application.
Gemcom also includes “special value” columns in its database that are hidden from the user in
Gemcom, but are visible in Microsoft Access. The “special value” columns control which data is
included in compositing and other functions, as well as how data is displayed in Gemcom, i.e., how
the “NS” used for “not sampled” is seen on the screen. The “special value” columns have been
removed from the Excel spreadsheet and comma-delimited files.
Note that GEMCOM only allows 10 characters in a column name, and that convention has been
adhered to in this listing. Other applications may allow longer names.
Data File Sizing, Splitting, and Naming
Each Gemcom table is included as a separate Excel spreadsheet (*.XLS) and comma-delimited
(*.CSV) file. Column headings were left in the Excel (*.XLS and *.CSV) files. Depending on their
final use, they may need to be removed. Because Excel has a line limit of about 64,000 lines, and
there are more than 64,000 entries for each of lithology and assays, the LITHOLOGY and ASSAY
tables have been broken into a west and an east file for the *.XLS and *.CSV formats. The header
file contains a reference to this under the heading “XLSFILE”.
The west and east file distinction was based on the listed intrusion for the drill hole. This division is
shown below in Table 1. The record of this east-west division is carried in all data files, even though
only the ASSAY and LITHOLOGY files are actually split.
Table 1. Listing of deposit areas showing to which, east or west, assay and lithology file the drill holes were assigned.
This convention is recorded in all data files on a drill hole by drill hole basis, even though other data files were not
split.
West Lithology and Assay Files East Lithology and Assay Files
Boulder Lake intrusion (BLI) Bald Eagle intrusion (BEI)
Duluth Complex Felsic Undivided Brule Lake intrusion
Diabase Undivided Cloquet Lake Layered Series of Beaver Bay Complex

(CLLS of BBC)
Duluth Layered Series (DLS), Houghtaling Creek Troctolite of Beaver Bay Complex (HCT
Layered Series at Duluth of Miller et al., 2002 of BBC)
Duluth Complex Anorthositic Undivided Logan Sill
Partridge River intrusion (PRI) North Shore Volcanic Group (NSVG)
11
Table 1 (continued)
Virginia Formation at Margin of Partridge River intrusion Osier Lake

(VF at margin)
Virginia Formation-Biwabik Iron Formation (VF-BIF) Poplar Lake intrusion
Western Margin intrusion (WMI) South Kawishiwi intrusion (SKI)
Tuscarora intrusion
Unknown and Unnamed
Virginia Formation-Biwabik Iron Formation (VF-BIF) at

Serpentine
Drill Hole Numbering
There have been changes in drill hole numbering to ease computer sorting:
1) For series of drill holes such as at Babbitt/Serpentine (B1- series holes) or Water Hen (SL-
series holes) where there are more than nine drill hole numbers assigned, leading zeros have
been added to the numeric portion of the drill hole number. For instance, drill hole B1-1 is
now B1-001, B1-32 is now B1-032, and SL-1 is now SL-01. This notation will conflict with
the MDNR drill core library index, the numbers on core boxes at MDNR and at other
locations, and previous NRRI work as well as parts of Miller et al. (2002), but this change
seemed the best way to deal with this large number of drill holes. This renumbering has not
caused any duplication of drill hole numbers;
2) All drill hole numbers given here are in upper case. Some holes, such as the “Du” series
(by Duval) have always been labeled with upper and lower case. The mixed case can cause
difficulties in some sorting operations;
3) All of the holes drilled by MDNR have had “-MDNR” added as a suffix because two of
them had ambiguous names that conflicted with other drill holes.
Data Comments
There are no commas in the data. All characters are upper case. Only the “from”, “to”, “interval
length”, other footage or length columns, and assay value columns are intended as numeric data. In
Microsoft Excel it can be a problem to keep numbers intended as text to remain in text format when
copied or moved from column to column or transferred from one file to another or one program to
another. The best solution may be to use the comma-delimited (*.CSV) files and import the data to
ones own formatting needs.
Drill Hole Coordinate and Location Comments
The Gemcom database system allows only one location coordinate for each drill hole. The Minnesota
State Plane North NAD27 (North American Datum 1927) coordinate system, in feet, was used for
location points in Gemcom. The NAD83 (North American Datum 1983) Minnesota State Plane
12
North coordinate, in feet, is also given. The UTM Zone 15 coordinate, in meters, is included in
NAD27 and NAD83 format. The choice to use the 1927 coordinate system in feet as the basic unit
of measure was driven by:
1) downhole units are in feet;
2) not all USGS maps are updated to the 1983 datum. The use of NAD27 in feet may make
cross-referencing easier;
3) GIS systems and computer programs such as “Corpscon for Windows” allow conversion
to the users preferred coordinate systems whereas Gemcom is not very flexible in this regard.
Drill hole locations are as good as they can be, but probably vary in their accuracy. The
Babbitt/Serpentine, Dunka Road (NorthMet), some of Maturi, some of Spruce Road, and South
Filson Creek area drill hole locations are based on recent (last ten-fifteen years) conventional and GPS
surveying of some or all of the collars and a recalculation of grid locations of unsurveyed holes from
those surveyed locations. Most of the INCO drill hole locations came straight from data supplied by
them to Dean Peterson and/or Mark Severson. In most other areas, locations are based on plotting
the company grid to a 1:24,000 USGS topographic map, plotting the drill holes based on grid
coordinates given on original logs (i.e., 3422N, 1286E) or scaled off of the available maps, and then
determining the UTM coordinate. For different deposits this has been done manually, in AutoCAD,
or in ArcView.
Note that the digital data on CD-ROM includes an ArcView shapefile containing drill hole locations
and other data where there is only one record per drill hole. The shapefile is based on the HEADER
table and file. The shapefile uses NAD83 UTM as its location coordinate and can supercede or
supplement the file supplied with Miller et al. (2002) as a way to quickly bring some updated
information into that ArcView project.
DATA TABLES-SHORT DESCRIPTIONS
Common Elements in All Data Tables
Short descriptions of the individual data table contents (for Tables 3 through 8 and associated text)
for the database are given in Table 2. Appendices 1 through 6 provide the same information in an
expanded form that details most of the discussion items related to each table or record type, such as
data source and quality, intrusion and deposit descriptions, or rock naming conventions.
With the exception of the header table, all tables are in “from-to” interval format with minimum
common elements for each interval as follows:
13
Table 2. General format of common fields in interval data tables.
DDH: drill hole number
FROM: start of interval relative to collar in feet
TO: end of interval relative to collar in feet
INTERVAL: interval length in feet along core
DSURVFROM[X]: desurveyed easting (interval “from” easting in NAD27 state plane feet)
DSURVFROM[Y]: desurveyed northing (interval “from” northing in NAD27 state plane feet)
DSURVFROM[Z]: desurveyed elevation (interval “from” elevation in feet above sea level)
DSURVTO[X]: desurveyed easting (interval “to” easting in NAD27 state plane feet)
DSURVTO[Y]: desurveyed northing (interval “to” northing in NAD27 state plane feet)
DSURVTO[Z]: desurveyed elevation (interval “to” elevation in feet above sea level)
XLSFILE: Whether lithology or assay data is in east or west Excel and comma-delimited files, given for each data type,
regardless of whether or not the data files were split
Desurveying
All of the down hole interval tables include “desurveyed” data for the individual intervals. This is a
Gemcom generated value where Gemcom calculates the true geographic location (NAD27) of each
data point (in this case the “from” and “to” points in the interval tables) relative to sea level. This
calculation is based on the collar location data in the header table and any downhole survey data in
the database. Drill holes with no down hole survey data available have been given the collar
orientation (dip and azimuth) for their entire length in the survey interval table and therefore also in
this calculation.
Column Order in Data Tables
Note that the column order may not be the same in all similar tables, nor be in the order given in these
descriptions. Also note that when the GCDBDC.MDB file is loaded as a blank project into Gemcom,
the column display order will be sorted alphabetically, left to right.
HEADER Table-Short Description
This table contains the drill hole location information, length, dip angle, azimuth, deposit name, and
other information that can be applied to the drill hole in its entirety.
The HEADER data are repeated in the HEAD-F-T table, which, with the addition of a “from” column
(always 0 ft.), and using the total drill hole depth as a “to” value, in interval format, allows all of the
HEADER data to be applied to the intervals in other data tables through the cross-table transfer
feature in Gemcom.
14
Table 3. Format of Header Table-see Appendix 1 for expanded explanation.
EASTSP27: easting NAD27 state plane feet
NORTHSP27: northing NAD27 state plane feet
COLLAR-EL: collar elevation in feet above sea level
TOTALDEPTH: total depth in feet
DIP: collar dip, measured from horizontal, 0/ = horizontal, -90/ = vertical
AZIMUTH: collar azimuth relative to true north
EASTUTM27 easting NAD27 UTM meters
NORTHUTM27: northing NAD27 UTM meters
EASTUTM83 easting NAD83 UTM meters
COL-EL-MET: collar elevation in meters above sea level
TOTDEPMETR: total depth in meters
DEPOSIT: deposit area
INTRUSION: which intrusion drill hole is located in
QUAD: USGS 7.5 minute quadrangle
TOWNSHIP: Public Land Survey Township
RANGE: Public Land Survey Range
SECTION: Public Land Survey Section
FORTY: partial list of forty acre subdivision
COUNTY: St. Louis, Lake, or Cook County
GEOLOGIST: geologist responsible for the logging or company that supplied data
DATE-DRILL: Date drilling finished
GRIDEAST: Grid east on original company grid
GRIDNORTH: Grid north on original company grid
GRIDCOMP: Company responsible for original grid
OVBTHICK: overburden thickness
FWDEPTH: depth to footwall (i.e., basal contact)
LESSEE: best available information for which company drilled this hole
VERT-ANG: vertical or angled at collar
INITIAL?: initial hole or wedge
SUR-UNDG: hole drilled from surface or underground drift
NRRI-XSECT: NRRI cross-section which shows this drill hole
15
Table 3 (continued)
COMP-XSECT: Company cross-section on which this drill hole should plot-listed only for
Dunka Road (NorthMet) and Babbitt/Serpentine (Mesaba). These cross-sections are not
necessarily available.
BEST-REF: best first reference for report about area containing drill hole, not intended to be a
definitive listing
HEAD-COMM: Comments related to data in the header file for this drill hole
SURV-COMM: Comments related to data in the survey file for this drill hole
LITH-COMM: Comments related to data in the lithology file for this drill hole
ASSAY-COMM: Comments related to data in the assay file for this drill hole
SOURCEFILE: NRRI record keeping entry
XLSFILE: The lithology and assay tables needed to be split to stay within the 64,000 line limit
of Microsoft Excel, this shows which file set this drill hole is in, either “EAST” or “WEST”,
*.XLS and *.CSV. This data is carried in all interval tables, even though not all files are split.
16
HEAD-F-T Interval Table For Header Data-Short Description
This table repeats the information found in the HEADER table, but in a “from-to” interval format
where the entire drill hole is treated as a single interval (“from” equals “0 “ (zero) and “to” equals
total depth in feet). In Gemcom this table is useful for cross-table transfer of data from one set of
intervals to another. This table is needed because Gemcom does not allow transfer from the
HEADER table to interval data tables. One would use this to, for instance, translate information from
the header file (for instance logging year, quadrangle map, or intrusion) to the individual intervals in
the ASSAY or LITHOLOGY interval tables. Remember that for angled holes, the locations in this
file refer to collar location, not downhole locations.
No format description is given here or in the expanded table format descriptions provided in the
appendices as the format and data contained in the HEAD-F-T table is the same as for the main
HEADER table.
17
SURVEY Table-Interval Table-Short Description
This table lists the downhole survey data available for each drill hole. In this database we have
included the extensive downhole dip and azimuth surveying at Babbitt / Serpentine in “from-to”
format. The majority of the holes at other areas do not have downhole azimuth testing, and may have
used a simple acid test for dip measurement. In the latter case, we make assumptions about the
compass direction the hole deviated towards. The assumption is that all holes turned northwest (into
the basal contact). Usually this will be grid north for an individual deposit area. This is generally how
companies have plotted these drill holes, though this is an item that must be reviewed when using
these data for site specific rather than regional work.
The survey data are used in modeling programs to establish the three-dimensional location of the
other data for analysis and display. This format accounts for the entire drill hole length, i.e., all
intervals, measured or not, are listed in the file. The sum of the intervals equals the length of the drill
hole.
Those drill holes with no downhole work done (or recorded here) are assigned the collar dip and
azimuth for the length of the drill hole. Some modeling programs will require that the survey data
be in this separate file, even if there is no change in the data downhole.
Dip is given as a negative value for holes from the surface. Note that some underground drill holes
in the Local Boy portion of the Babbitt deposit and a few holes in the drift at Maturi were drilled
upwards from the drifts and therefore have a positive dip.
Table 4. Format of Survey Table-see Appendix 2 for expanded explanation.

INTERVAL: interval length in feet
DIP: Dip of interval, -90/ equals straight down
AZIMUTH: azimuth of interval clockwise from true north, for vertical holes azimuth equals 0/
XLSFILE: The lithology and assay tables needed to be split to stay within the 64,000 record limit of Microsoft Excel. This
entry shows which file set the drill hole is in, either “EAST” or “WEST”, *.XLS and *.CSV for lithology and assays . The
survey data is all in one table or file, i.e., it is not split.
18
LITHO Interval Table-Short Description
This table contains the lithological data for each hole in “from-to” interval format. This table covers
the NRRI logging, filled in on a hole by hole basis with company data for holes either unavailable for
logging or not logged by NRRI. This format accounts for the entire drill hole length, i.e., all intervals,
logged or not, are listed in the file. The sum of the intervals equals the length of the drill hole. See
Appendix 3 for complete explanation.
Table 5. Format of Lithology Data Table-see Appendix 3 for expanded explanation.

INTERVAL: interval length in feet along the drill hole
ROCKTYPE: logged rocktype by abbreviation
EXP-RTYPE: logged rocktype-full expanded name
CON-RTYPE: example of consolidation of rocktype names–reduces the number of rocktype names
UNIT: cross-section (map) unit
NRRI–XSECT: NRRI cross-section showing this drill hole, as in header file
COMP-XSECT: company cross-section this hole would be on, listed only for Babbitt and Dunka Road
FW-MARKER: marks interval as overburden, Complex, or footwall
FW-FROM: interval “from” measuring upward or downward from drill hole footwall penetration point, in feet
FW-TO: interval “to” measuring upward or downward from drill hole footwall penetration point, in feet
GEOLOGIST: geologist responsible for logging, as in header file
DEPOSIT: which deposit, as in header file
column shows which table or file set this drill hole is in, either “EAST” or “WEST”, *.XLS and *.CSV files.
19
ASSAY Interval Table-Short Description
Essentially, all of the original assay work in the Duluth Complex is on copper-nickel sulfides. In a
few cases, the emphasis was on massive-oxides in the Oxide-bearing Ultramafic Intrusions (OUIs at
Longear, Longnose, Section 17, Section 22, etc.). Those oxides and related elements are not
included here. Also, United States Steel almost always assayed for iron, which is included here for
the Dunka Road (NorthMet) area, and INCO and others often assayed for cobalt, which is not
included here due to data entry time constraints. Not all companies assayed all intervals for sulfur.
These are generally the assays done at the time of original drilling and sampling, and usually represent
the greatest number of samples done for a particular drill hole. The format here covers the entire hole
from collar to total depth, with a “NS” marker for intervals not sampled in the original work. Not
all elements were equally sampled for each interval or equally by each company. This format
accounts for the entire drill hole length, i.e., all intervals, sampled or not, are listed in the file. The
sum of the interval lengths equals the length of the drill hole.
Numerous duplicates and overlapping intervals (about 1,500 total) were removed from the previous
compilations used to develop this data file. This subtraction is done by Gemcom when loading the
data. The duplicates were, therefore, not retained in a separate file.
Table 6. Format of Assay Data Table-see Appendix 4 for expanded explanation.

INTERVAL: interval length in feet along the drill hole
COPPER: copper in percent
NICKEL: nickel in percent
SULFUR: sulfur in percent
CU+NI: copper plus nickel in percent
CU/NI: copper/nickel ratio
CU/S: copper/sulfur ratio
DEPOSIT: which deposit, from header file
XLSFILE: the lithology and assay tables needed to be split to stay within the 64,000 record limit of Microsoft Excel. This
format this shows which file set this drill hole is in, either “EAST” or “WEST”, *.XLS and *.CSV files.
20
RQD Interval Table-Short Description
This is the Rock Quality Designation (RQD) data calculated by AMAX for the Babbitt and Serpentine
deposits. There is no publicly available data on these rock properties for any other exploration area
in the Duluth Complex. It is unknown, but doubtful, if this work has been done elsewhere. Contact
NRRI or the MDNR for information from the AMAX files about the calculation of the AMAX RQD
numbers.
This format accounts for the entire drill hole length, i.e., all intervals, sampled or not, are listed in the
file. The sum of the intervals equals the length of the drill hole.
Table 7. Format of RQD Data Table-see Appendix 5 for expanded explanation.

INTERVAL: interval length along core in feet
RQD: RQD value as calculated by AMAX. Higher number equals more natural fractures for indicated interval
21
PGE-ETC Interval Table-Short Description
In general, except for in the Birch Lake area, all publically available PGE and precious metal assaying
done in the Duluth Complex was done after the original Cu-Ni sampling. Sometimes this sampling
was on the original pulps, sometimes on composite pulps, and sometimes on fresh core. Morton and
Hauck (1987) summarized the publically available assaying up to that point in time and added some
new analyses. The data in this database table are taken from Severson and Hauck (in prep., 2003)
and represents all publically available data. It is important to stress that there may be other
proprietary data for Dunka Road/NorthMet (PolyMet), Babbitt/Serpentine (Teck Cominco), Birch
Lake (Lehmann), and Maturi (Wallbridge and INCO) areas, as well as other locations.
Besides PGE data, this table includes some major, minor, and trace element analysis data. Reference
should be made to Severson and Hauck (in prep., 2003) for information on the quality and source of
individual samples. The final data tables in Severson and Hauck (in prep., 2003) will be far more
complete and record more elements. The data here are a sub-set of the data in their report.
The format here does not account for the entire length of the drill hole, only including intervals that
were sampled. About 1,000 duplicate and overlapping intervals have been removed from this dataset
during the loading process. There is no record here of which intervals are duplicated or were
overlapping. The dataset in Severson and Hauck (in prep., 2003) is far more complete.
Table 8. Format of PGE-ETC Data Table-see Appendix 6 for expanded explanation.

INT-AS-TXT: “from-to” for interval as single text entry
LENGTH: length along core of sample interval
INTRUSION: which intrusion drill hole is in
UNIT: rock unit, from Severson and Hauck (in prep., 2003)
ROCKTYPE: rock type, from Severson and Hauck (in prep., 2003)
DEPOSIT: deposit drill hole is in
AU-PPB: gold in parts per billion-as recorded in original data
PT-PPB: platinum in parts per billion-as recorded in original data
PD-PPB: palladium in parts per billion-as recorded in original data
CU-PPM: copper in parts per million-as recorded in original data
NI-PPM: nickel in parts per million-as recorded in original data
S%: sulfur in percent-as recorded in original data
CO-PPM: cobalt in parts per million-as recorded in original data
ZN-PPM: zinc in parts per million-as recorded in original data
22
Table 8 (continued)
AG-PPM: silver in parts per million-as recorded in original data
AU-PPM: gold in parts per million-as recorded in original data
AS-PPM: arsenic in parts per million-as recorded in original data
CR-PPM: chromium in parts per million metal-as recorded in original data
TIO2%: titanium as percent oxide as reported in original data
TI%: titanium as percent, metal as reported in original data
MGO%: magnesium as percent oxide as reported in original data
MG%: magnesium percent metal as reported in original data
CR2O3%: chromium as percent metal as reported in original data
CL-PPM: chlorine in parts per million-as recorded in original data
MO-PPM: molybdenum in parts per million-as recorded in original data
V-PPM: vanadium in parts per million-as recorded in original data
CU/PD: copper:palladium ratio
CU%: copper percent, calculated from ppm data
NI%: nickel percent, calculated from ppm data
REFERENCE: data source, see Severson and Hauck (in prep., 2003) for details on sample selection
column shows which file set this drill hole is in, either “EAST” or “WEST”, *.XLS and *.CSV files. This file is not split.
23
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24
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25
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26
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27
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p., 30 plates.
Severson, M.J., and Zanko, L.M., 1996, Geologic map of the Dunka Road deposit, Duluth Complex,
Duluth, Confidential Technical Report (for Argosy-Fleck Resources), NRRI/TR-96/05, 26
p., 5 plates.
Severson, M.J, and Hauck, S.A., 1997, Igneous stratigraphy and mineralization in the basal portion
of the Partridge River intrusion, Duluth Complex, Allen Quadrangle, Minnesota: Natural
Resources Research Institute, University of Minnesota Duluth, Technical Report, NRRI/TR-
97/19, 102 p., 4 plates, 1 diskette.
Severson, M.J., and Hauck, S.A., 1998, Field Trip Guide: Minnesota Exploration Conference ‘98,
Biwabik, Minnesota, p. 1-12.
Severson, M.J., and Miller, J.D. Jr., 1999, Bedrock geologic map of Allen Quadrangle: Minnesota
Geological Survey, Miscellaneous Map M-91, 1:24,000.
Severson, M.J., and Hauck, S.A., in prep., 2003, Platinum-group elements (PGEs) and platinum-
group minerals (PGMs) in the Duluth Complex: Natural Resources Research Institute,
University of Minnesota Duluth, Technical Report, NRRI/TR-03-XX.
Severson, M.J., and Zanko, L.M., in prep., The Babbitt copper-nickel deposit, Part D: Geology and
mineralization of the Local Boy massive sulfide area : Natural Resources Research Institute,
University of Minnesota Duluth, Technical Report.
Strommer, J., Morton, P., Hauck, S.A., and Barnes, R.J., 1990, Geology and mineralization of a
cyclic layered series, Water Hen intrusion, St. Louis County, Minnesota: Natural Resources
Research Institute, University of Minnesota Duluth, Technical Report, NRRI\GMIN-TR-89-
17, 29 p., 12 plates.
28
Venzke, E.A., in prep, The geology and petrogenesis of the Greenwood Lake area, Lake County,
Minnesota: Unpublished M.S. Thesis, University of Minnesota Duluth, 166 p.
Weiblen, P.W., and Morey, G.B., 1980, A summary of the stratigraphy, petrology and structure of
the Duluth Complex: American Journal of Science, v. 280, p. 88-133.
Zanko, L.M., Severson, M.J., and Ripley, E.M., 1994, Geology and mineralization of the Serpentine
copper-nickel deposit, Duluth Complex, Minnesota: Natural Resources Research Institute,
University of Minnesota Duluth, Technical Report, NRRI/TR-93/52, 90 p.
29
APPENDICES 1 THROUGH 8 INTRODUCTION
30
APPENDICES 1 THROUGH 8 INTRODUCTION
INTRODUCTION
There are eight written appendices. Most of these (1 through 6) address the contents of the data files
forming the core of this report. One (Appendix 7) addresses some generalities about the relation
between the various drill hole numbering schemes, grid names, and deposit areas; and one (Appendix
8) is a listing of potentially useful contacts related to exploration and mining in Minnesota.
FILE NAMES AND CONTENTS
Refer to Figure 1 for the schematic database layout. The CD-ROM enclosed with this report
contains the following files (XLS are Microsoft Excel files, CSV are comma-delimited files):
NRRI-DIGITAL-LOGS.PDF: Adobe “portable document format” version of this report.
GCDBDC.MDB: Master database in Microsoft Access format, intended for use in Gemcom
for Windows. Not specifically described in an appendix, see Appendices 1 through 6 and
descriptions for individual tables within this database.
HEADER.XLS & HEADER.CSV: Header data (one record per hole, data such as: location,
year, orientation, etc.). See Appendix 1 for explanation.
MDDHHEAD.SHP, MDDHHEAD.DBF, MDDHHEAD.SBN, MDDHHEAD.SBX,

MDDHHEAD.SHX: Header table, with NAD83 UTM drill hole location in meters as the
location coordinate (as opposed to the 1927 state plane feet coordinate used in this report),
intended for use in ArcView. This could be used to supercede or supplement the drill hole
location file supplied with the ArcView data in Minnesota Geological Survey Report of
Investigations 58, “Geology and Mineral Potential of the Duluth Complex and related Rocks
of Northeastern Minnesota”, (Miller et al., 2002). The drill hole locations vary somewhat
from those in RI-58, and this file contains more data than the drill hole location file in RI-58.
There is some unique data in the file supplied with RI-58 not in this file, and some data in this
file not in that supplied with RI-58. See Appendix 1 for the column explanations.
DEPOSITS.SHP, DEPOSITS.DBF, DEPOSITS.SHX: An ArcView polygon dataset showing

the deposit areas of the Duluth Complex. Created by drawing closed lines around most
groups of drill holes named in this report. Not intended to be a detailed map of deposit
geometry, but useful for posting deposit data labels to maps. In NAD83 UTM datum, which
is contrary to the bulk of the data in this report, which uses 1927 state plane feet for the
location coordinate.
HEAD-F-T.XLS & HEAD-F-T.CSV: Header data (one record per hole, data such as:
location, year, orientation, etc.) in “from-to” format. See Appendix 1.
SURVEY.XLS & SURVEY.CSV: Downhole survey data for each drill hole. See Appendix
2 for explanation.
31
EAST-LITHO.XLS & EAST-LITHO.CSV: Downhole lithology data for (approximately) the
east half of the Duluth Complex. See Appendix 3 for explanation.
WEST-LITHO.XLS & WEST-LITHO.CSV: Downhole lithology data for (approximately)

the west half of the Duluth Complex. See Appendix 3 for explanation.
EAST-ASSAY.XLS & EAST-ASSAY.CSV: Downhole Cu-Ni-S assay data for

(approximately) the east half of the Duluth Complex. See Appendix 4 for explanation.
WEST-ASSAY.XLS & WEST-ASSAY.CSV: Downhole Cu-Ni-S assay data for

(approximately) the west half of the Duluth Complex. See Appendix 4 for explanation.
RQD.XLS & RQD.CSV: “Rock Quality Designator” data for Babbitt and Serpentine
deposits. See Appendix 5 for explanation.
PGE-MJS.XLS & PGE-MJS.CSV: PGE data taken from Severson and Hauck (in prep.,
2003). See Appendix 6 and their paper.
DATA ENTRY AND RECONCILIATION DETAILS
All original data entry and calculation (interval lengths, ratios) for this project was done in Microsoft
Excel. Some data were reformatted from older Lotus 123 (*.WK1) and Quattro Pro (*.WB1) files.
The Excel files were then saved in *.CSV format and loaded to the GCDBDC.MDB file using
Gemcom for Windows (version 4.02). This was the oldest version of Gemcom available to us. It was
used on the assumption that the older the data file format the more programs that would be able to
read it. Gemcoms’ excellent error checking and validity checking routines were used, corrections
were made over various iterations of reloading data to fix items such as making sure that the length
for a particular hole was the same in all files referencing that hole, or that there were no overlapping
or missing intervals. Once finally corrected and rectified, each data table was exported to Microsoft
Excel format out of the database, using Microsoft Access. The error checked tables were then
reformatted in Excel to the comma delimited (*.CSV) files. These comma delimited files were then
loaded to a blank project in Gemcom to create the “clean” and final copy of the database referenced
here. Consequently, these files should be carrying no coding from earlier iterations of calculation or
any other specific program formatting.
In the following appendices, column headings in the specific data files are given as “HEADING:”,
i.e., all caps, followed by a colon.
32
APPENDIX 1
HEADER TABLE FORMAT AND EXPANDED DESCRIPTION FOR GEMCOM

DATABASE (GCDBDC.MDB) AND SPREADSHEET FILES (HEADER.XLS,
HEADER.CSV)
33
APPENDIX 1: HEADER TABLE FORMAT AND EXPANDED DESCRIPTION FOR
GEMCOM DATABASE AND SPREADSHEET FILES
HEADER TABLE INTRODUCTION
Following is the expanded description of the HEADER file contents for the database. The column
order in this description is not the same as that in the database table or spreadsheet files. Columns
have been grouped by data type. In particular, note that the DEPOSIT: and INTRUSION: listings
have been moved to the end of this appendix because of the length of those two discussions.
DRILL HOLE NUMBERING
DDH: drill hole number: The drill hole number used here is the original company number with
few exceptions. All characters are now in upper case letters. See Appendix 7 for some
unreferenced generalities about drill hole numbering versus deposit area or grid name.
There have been a few small changes here in drill hole numbering to ease computer sorting:
1) For series of drill holes such as at Babbitt/Serpentine (B1- series holes) or Water
Hen (SL- series holes) where there are more than nine drill hole numbers assigned,
leading zeros have been added to the numeric portion of the name. For instance B1-1
is now B1-001, B1-32 is now B1-032, and SL-1 is now SL-01. This re-numbering
will conflict with the MDNR drill core library index, the numbers on core boxes at
MDNR and at other locations, and previous NRRI work as well as parts of Miller et
al. (2002). This minor change in numbering seemed the best way to deal with the
large number of drill holes, and this renumbering has not caused any duplication of
drill hole numbers;
2) All drill hole numbers given here are in upper case. Some holes, such as the “Du”
series (by Duval) have always been labeled with upper and lower case. This case
difference can cause difficulties in some computer sorting operations and is avoided
in this dataset;
3) The holes drilled by MDNR have had “-MDNR” added as a suffix because two of
them had ambiguous names that could conflict with other drill holes.
Some drill holes in the Complex have more than one number in the paper records. Notably
some of the first eleven “NM” series (Newmont) drill holes in the Dunka Pit area have been
re-labeled as “E” series drill holes. The GF series drill holes (sometimes labeled as ON series
drill holes in paper files) in the Gunflint area were re-entered (and re-numbered) by second
or third companies after their initial drilling. Some USS Corp. drill holes that penetrate both
the Duluth Complex and the Biwabik Iron Formation have a hole number for each of those
portions. Sometimes these multiple numbers are clear in the paper records, sometimes they
34
are not, and are discovered by accident when trying to reconcile data discrepancies. These
alternate numbers (where known) are shown in parentheses.
Also, note that many of these drill hole numbers may be repeated in other geologic terranes
of Minnesota, and when requesting information, it is best to also know the coordinate or
public land survey location point for any particular drill hole.
DRILL HOLE LOCATION BY X, Y, AND Z COORDINATES

Drill hole easting and northing in NAD27, Minnesota State plane north feet

Drill hole easting and northing in NAD83, Minnesota State plane north feet
EASTUTM27: easting NAD27 UTM meters

Drill hole easting and northing in NAD27, UTM zone 15
EASTUTM83: easting NAD83 UTM meters

Drill hole easting and northing in NAD83, UTM zone 15
Drill hole locations are fairly reliable, and the locations are internally consistent to one
another. However, as with many items, it is recommended that one understand how various
drill hole locations were derived before starting detailed work in an area. Collar locations
were derived from: recalculation of surveyed grid and drill hole data for Babbitt and
Serpentine; some recent (since ~1990) survey and recalculation of the grid work by NRRI for
Dunka Road, South Filson Creek, Maturi, and Spruce Road; for other areas, by plotting the
company grids and/or drill hole locations on 1:24,000 (or better) maps and scaling the state
plane or UTM coordinate from that map.
All conversions between coordinate systems were done by the “Corpscon for Windows”
program available from the United States Army Corps of Engineers.
Locations used in this database should supercede those in Miller et al. (2002), as the ability
to check drill hole location in cross-section has lead to some corrections. Drill hole geology
generally fits the expected location of the collar and basal contact where examined in cross-
section, indicating no readily recognizable gross errors in drill hole location.
Locations for Birch Lake holes drilled after 1995 and the drill holes by PolyMet at Dunka
Road (NorthMet) were estimated from the abandonment reports turned in to the Minnesota
Department of Health.
35
The choice to use state plane feet in NAD27 was driven by three items:
1) there are still many USGS maps in circulation without any UTM grid, and much
of the original work was done prior to NAD83;
2) virtually every reference to measurement in the original data is in feet;
3) Gemcom does not allow different coordinate systems for the vertical (downhole)
measurements and the horizontal measurements.
The UTM location data and the few downhole measurements given in meters are to allow a
quick insertion of some of these data into a GIS system, e.g., ArcView. The header file is
included as an ArcView “shapefile” in NAD83 on the CD-ROM. However, to fully use this
dataset in a metric system of measure will require reformatting of every data table.
We chose to not include the exact source for each data point both in this report and in the
database. From information at NRRI or MDNR one could recreate these locations to
demonstrate their accuracy if need be. Please contact NRRI or MDNR for any location data
point that needs further documentation.
The level of accuracy/precision shown for the hole locations, to the second decimal point, is
not realistic, but is retained so that locations won’t “creep” one unit or less if rounded and
then reprocessed or converted again between coordinate systems. The spreadsheet and
comma-delimited files have had their precision cut to one or two decimal points for all
footage measurements, however, Gemcom (and sometimes Excel) has a tendency to show up
to ten or twelve numbers to the right of the decimal point that round to the correct value, but
do not represent the values as entered or calculated.
COLLAR-EL: collar elevation in feet above sea level

COL-EL-MET: collar elevation in meters above sea level
Collar elevations were derived from the same process as described above for the drill hole
locations. Many drill holes had very reliable elevations in the original data. Elevations on
1:24,000 maps were estimated for the locations where no elevation was given in the original
data. Most of the USGS base maps used are 10 foot contour interval. As with the location
data, the collar elevations have been checked in cross-section and appear reasonable.
The metric collar elevation was derived by dividing the footage by 3.2808 to arrive at meters.
DRILL HOLE DEPTH
TOTALDEPTH: total depth in feet

TOTDEPMETR: total depth in meters
36
Total depth is length from collar along the drill hole to the toe of the hole. Total depth
numbers were taken from the original company data wherever possible. Discrepancies
between the company data and what was recorded in the logging were resolved on a case by
case basis depending on available data. The comment column in the database reflects that
some drill holes (such as at Mile Post 7 and others) had no depth recorded, in those cases we
used a placeholder value, such as 100 feet, which may be much more than the true length.
These placeholder values are needed in Gemcom (and probably other software) because a drill
hole cannot have a length of “0". Generally this will not be a data quality issue because these
are drill holes with little or no documentation otherwise.
The metric total depth value was derived by dividing the footage by 3.2808 to arrive at
meters.
Gemcom refers to total depth as “length”.
For drill holes from the underground work at Babbitt and Maturi, total depth is length from
the collar to the end of hole. For wedge holes, total length equals depth from surface along
the drill hole, not from the wedge point. Note that the wedge holes at Birch Lake were
treated differently than other wedged holes. See discussion about this in the survey data table
explanation.
For some holes, such as the RMC series holes drilled by Reserve Mining Company and a few
USS holes at Dunka Road (NorthMet) the total depth (and the listed geology) stops just into
the Biwabik Iron Formation. At the Babbitt (Mesaba) Deposit, Reserve Mining drilled
through the Duluth Complex to reach the iron-formation below, and Bear Creek Mining
assayed the Duluth Complex portion of the drill hole. The data for the rest of the drill hole
(the iron-formation portion) was not available to NRRI. At Dunka Road (NorthMet) the
iron-formation core from drilling below the Duluth Complex was passed on to the Minntac
mine, often with a different drill hole number, such as USS drill hole 25403, which is also
recorded as 26089. Two different data sources give this hole as being in slightly different
locations, but with all downhole data being the same. This is an excellent example of why we
feel these data should not be used without some familiarity with the Duluth Complex and the
exploration history of the region.
DRILL HOLE ORIENTATION
DIP: collar dip, measured from horizontal, 0/ = horizontal, -90/ = vertical

AZIMUTH: collar azimuth clockwise relative to true north
Dip and azimuth values in the header file refer only to the recorded collar orientations. There
may or may not be further downhole measurements (see survey table). Collar dip data was
taken from original logs. Dip is recorded as a negative value from the horizontal.
Azimuth data was taken from the original logs or original grid maps, if available. Azimuth
is recorded as clockwise from true north. As with many other parts of the data in this
37
database, we have used these azimuth values for various projects over the years and find these
to be reasonable numbers. However, it is not always completely clear on logs whether or not
the northing refers to true north or grid north. In the larger datasets, it seems there are
always a few drill holes with some notational uncertainty in this regard. We used our
judgement on a case by case basis.
VERT-ANG: vertical or angled at collar
Was this hole drilled vertical or at an angle? If the collar angle was anything but -90/, it is
listed in this column as an angled hole.
INITIAL?: initial hole or wedge
Was this hole drilled as an original hole, or as a wedge off of the original? Wedge holes have
their own geometry issues in various drill hole plotting programs, and not all wedges in this
database were treated in exactly the same way.
For wedged drill holes at Babbitt and Serpentine, the portion in the database above the wedge
is the same location data as for the original drill hole. The lithology and assays for this upper
portion are listed as not logged or not sampled for the wedge hole.
Other wedged holes, such as Birch Lake, where the true geometry has not been released to
public domain, do not follow this convention. There the wedges are given as a separate hole
with a location for each successive wedge one meter east and one meter north of the original
hole or previous wedge. The main effect of this adjustment is to make sure the holes plot in
cross-section or plan view. At Birch Lake there may be many wedges off of each drill hole.
SUR-UNDG: drilled from surface or underground drift?
Was this hole drilled from the surface or from underground? At Babbitt about 220 holes and
at Maturi about 13 holes were drilled from drifts in the deposits. This column is to allow one
to separate these, as they may represent different sampling populations than the other drilling,
primarily due to their close proximity to one another.
DRILL HOLE LOCATION BY PUBLIC LAND SURVEY (PLS), COUNTY, AND QUAD
COUNTY:
All drilling in this report is in St. Louis, Lake, or Cook Counties in northeastern Minnesota.
QUAD:
This is the USGS 7.5 minute topographic quadrangle map where the drill collar plots. Data
taken from NRRI files, MGS files, and inspection of drill hole locations using the GIS
database included in Miller et al. (2002).
38
TOWNSHIP: Public Land Survey Township
RANGE: Public Land Survey Range
SECTION: Public Land Survey Section
FORTY: partial list of forty acre subdivision
The public land survey location data were taken from the original logs, NRRI plots of drill
hole locations, and inspection of drill hole locations using the GIS database included in Miller
et al. (2002). Because land and mineral ownership issues can be complex, and because
ground surveys may give different results than paper plots of drill hole locations, these should
be used only as a guide. Property specific assumptions about land and mineral rights should
not be based solely on this PLS data.
There are three drill holes that fall in PLS Range East, in eastern Cook County, all others fall
in Range West. All Township values are North. The forty acre subdivision given here are
those readily available during data compilation. We did not estimate any new forty acre
subdivision locations.
GEOLOGIST(S), CROSS-SECTIONS, GRIDS, and DATE
GEOLOGIST:
This column lists the geologist responsible for the log used here. There are other (company
and other geologist) logs for almost all drill holes that NRRI has logged. For drill holes we
have not logged, we used any available company logging.
MJS: Mark J. Severson of NRRI, all deposits
MJS-FW: Mark J. Severson logged footwall portion of hole, rest of data for drill hole
assembled from surrounding holes and original company logging. Severson did all of
the footwall logging or re-logging at Babbitt, Serpentine, Dunka Road, and Dunka
Pit, even where not specifically noted as such
SAH: Steven A. Hauck of NRRI, mostly Babbitt, but some work on all deposits
LMZ: Lawrence M. Zanko of NRRI, Babbitt and Birch Lake and Serpentine deposits
SDG: Steven D. Monson-Geerts of NRRI, Dunka Road deposit only
RLP: Richard L. Patelke of NRRI, Babbitt and Dunka Road deposits
JJH: John J. Heine of NRRI, Babbitt only
STROMMER: James Strommer of NRRI, Water Hen only
KUHNS: Mary Jo Kuhns of NRRI, South Filson Creek only
39
JSO: John S. Owens of Hanna Mining Company
SJM: Sarah Jane Mills
INCO (with modifiers): Data supplied by INCO, usually digital
Lehmann Abandonment Report: Drill hole abandonment reports turned in to

Minnesota Department of Health
PolyMet Abandonment Report: Drill hole abandonment reports turned in to

LTV Data: Data from LTV Steel Mining Company (now Cliffs-Erie Mining Company
LLC) collected by Dean Peterson and Mark Severson. Originally digitized by Dean
Peterson.
NL: Not logged
NL Rotary: Not logged because only chips are available
Venzke: Edward Venzke thesis (in prep.)
Placeholder data: “Made up” values to keep spot open in database for this drill hole
The Minnesota Geological Survey, Newmont, Exxon, Bear Creek, AMAX, Humble,
USBM, MDNR, New Jersey Zinc, Lehmann Exploration Management, Wallbridge
Mining, USS, and Reserve Mining Company all contributed logs to the drill data files
at NRRI and MDNR that are referenced here.
NRRI-SECT:
This is the NRRI cross-section that the geologic unit data for this drill hole was taken from.
Multiple sections were used for some holes, and in some cases drill holes off of section were
estimated from surrounding sections.
COMP-SECT:
This is the company cross-section for this drill hole based on company grid coordinates. This
was calculated only for Dunka Road (NorthMet) and Babbitt (Mesaba) where NRRI has done
cross-sections through the entire deposit and allows us to make comparisons between our
sections and the company data. We have never found geologic sections for these deposits,
though grade sections do exist. This comment is not intended to imply that these company
geologic sections are available for inspection at any archive we know of.
40
GRIDEAST:
This is the grid easting reported by the company. This is a case where we entered what data
we already had, but did not search the archives for more information.
GRIDNORTH:
This is the grid northing reported by the company. This is a case where we entered what data
we already had, but did not search the archives for more information.
GRIDCOMP:
This is the grid designation or name assigned by the company. This is a case where we
entered what data we already had, but did not search the archives for more information.
DATE:
Date drilled, taken from the data file for the GIS database in Miller et al. (2002).
OVERBURDEN THICKNESS AND FOOTWALL DEPTH

OVBTHICK:
Overburden thickness (depth to ledge) is taken directly from the lithology files used in this
report. We have assumed that if there is no core at the top of the hole that interval must have
been overburden, and if there is rock, it is in place. This could be wrong for two reasons:
1) the drillers may have passed thru weathered ledge before beginning coring, as we
saw evidence for in the 1995-1996 Arimetco test Pit at hole B1-411 in the Babbitt
deposit (Patelke, unpublished observation); and at areas such as Water Hen, where
deep saprolite was encountered over an OUI. Saprolitic intervals may have been
drilled in some holes and not clearly recorded. (Deep saprolites are generally not
reported in this region, due to removal by glaciation);
2) at the 2001 Cominco test pit at hole B1-321 in the Babbitt deposit there were very
large boulders in the drift, in some cases boulders similar to the ledge bedrock may
have been cored as being in place (Severson, unpublished observation).
This depth to ledge value is along the drill hole, and is not corrected for angled drill holes.
FWDEPTH: depth to footwall
This is the distance along the core to the footwall contact (basal contact). This is usually the
intercept point for the Virginia Formation (VF), the Biwabik Iron Formation (BIF), or the
Giants Range batholith (GRB). There may be Keweenawan intrusive rocks below this point.
The definition of this intercept point has usually been placed in a location that makes best
41
sense in cross-sectional view where ambiguities arise, such as at the western end of the
Babbitt deposit or in the Wetlegs area where there is “overhanging” Virginia Formation.
Some holes, those entirely in the Virginia Formation or Biwabik Iron Formation, will show
footwall at the ledge. These are non-Duluth Complex holes included for stratigraphic control.
METADATA AND RECORD KEEPING ENTRIES

LESSEE:
This information is from the logs and our general knowledge. Interconnected joint ventures
between mining companies are the rule, not the exception, and these data reflects our best
judgement as to what company was responsible for drilling this hole. This has not been
completely checked with all available data and should be used only as a guide. No research
into the true responsibility for drilling is implied here.
BEST-REF:
Best first reference for report about area containing drill hole
Miller et al. (2002) and the references within are by far the best references on the Duluth
Complex as a whole. The references here are those related most to these deposit areas. This
is not intended to be a complete list.
HEAD-COMM:
Comments about this hole related to the header file data, if any
SURV-COMM:
Comments about this hole related to survey data, if any
LITH-COMM:
Comments about this hole related to the lithology data, if any
ASSAY-COMM:
Comments about this hole related to the assay data, if any
SOURCEFILE:
Record keeping for data entry at NRRI
42
XLSFILE:
Are these data in the EAST-LITH.XLS, EAST-CUNI.XLS, WEST-LITH.XLS, or WEST-

CUNI.XLS files (and their *.CSV comma-delimited equivalents)? The lithology and copper-
nickel assay files are too long for MS Excel. They were split into the above named east and
west files. The west and east distinction was based on listed intrusion for the drill hole. This
division is shown on Table 9 below. These data are carried in all data files, even though only
the ASSAY and LITHO files are split.
Table 9. Repeat listing of deposit areas showing to which (east or west) assay and lithology file drill holes
were assigned. This convention is recorded in all files on a drill hole by drill hole basis, even though other data
files were not split. Intrusion names in parentheses are those used in database, otherwise full name was used.
West Lithology and Assay Files East Lithology and Assay Files
Boulder Lake intrusion (BLI) Bald Eagle intrusion (BEI)
Duluth Complex Felsic Undivided Brule Lake intrusion
Diabase Undivided Crocodile Lake intrusion
Duluth Layered Series (DLS) Cloquet Lake Layered Series of Beaver Bay Complex
Layered Series at Duluth of Miller at al., 2002 (CLLS of BBC)
Duluth Complex Anorthositic Undivided Greenwood Lake intrusion (GLI)
Partridge River intrusion (PRI) Houghtaling Creek Troctolite of Beaver Bay Complex (HCT
of BBC)
Virginia Formation at Margin of Partridge River intrusion Logan Sill

(VF at margin)
Virginia Formation-Biwabik Iron Formation (VF-BIF) North Shore Volcanic Group (NSVG)
Western Margin intrusion (WMI) Osier Lake intrusion
Poplar Lake intrusion
South Kawishiwi intrusion (SKI)
Sonju Lake intrusion (SLI)
Tuscarora intrusion
Unknown or Unnamed
Virginia Formation-Biwabik Iron Formation (VF-BIF) at

Serpentine
43
INTRUSION AND DEPOSITS REVIEWS
Introduction to Intrusions and Deposits
INTRUSION DEFINITION:
This database reports drill holes in fifteen named intrusions of the Duluth Complex and
associated rocks, and some areas without formal or informal intrusion names (see Figure 2
for generalized Duluth Complex map). The named intrusions at the edge of the Complex
proper are, starting in Duluth and following the basal contact around the Complex
counterclockwise: Duluth Layered Series (DLS), Boulder Lake intrusion (BLI), Western
Margin intrusion (WMI), Partridge River intrusion (PRI), South Kawishiwi intrusion (SKI),
and the Bald Eagle intrusion (BEI). Intrusions in the interior of the Complex include: Duluth
Complex Anorthositic Undivided, the Greenwood Lake intrusion (GLI), Osier Lake intrusion,
Diabase Undivided, and Duluth Complex Felsic Undivided.
In the Finland-Silver Bay area, this drilling also includes some rocks of the Beaver Bay
Complex (BBC): the Cloquet Lake layered series (CLLS) and the Sonju Lake intrusion (SLI).
Associated with the BBC for purposes of this database are rocks of the North Shore Volcanic
Group (NSVG, see Miller et al., 2002, for description).
In the Gunflint area, the intrusions are now classed as separate intrusions from the Duluth
Complex (Miller et al., 2002): the Poplar Lake intrusion (PLI, formerly known as “Nathans
Layered Series”), Crocodile Lake intrusion (CLI), Brule Lake intrusion, Tuscarora intrusion,
and the Logan Sills, which are early Keweenawan sills intruding the Rove Formation and
Gunflint Iron Formation (GIF; Figure 2 and parts of the text, as well as many of the files at
NRRI, group all of these holes as being in the “Gunflint Corridor”).
Detailed descriptions of these intrusions are far beyond the scope of this paper. The current
best reference is Miller et al. (2002) and the references within.
DEPOSIT DEFINITION:
A “deposit” for the purpose of this study is geologically distinct, by: grade, rock type,
predominant map unit, or intrusion; and is defined by a cluster of drill holes generally drilled
for a common purpose (i.e., to test a geophysical feature or translate geology downward from
outcrop) or done as a single project. There is no economic judgement or connotation
intended by the use of the terms deposit, project, prospect, or ore.
The intrusions and deposits within them described here are arranged starting from southwest,
near Duluth (see Figure 2), along the basal contact of the Duluth Complex north to the
Mesabi Iron Range, then following the basal contact as it turns northeast near Wyman Creek.
Drilling does not extend northeast past the Spruce Road area because of restrictions
associated with the Boundary Waters Canoe Area Wilderness (BWCAW). Drill holes or
44
45
Figure 2. Generalized map of Duluth Complex , complete caption on next page.

Figure 2. Generalized map of Duluth Complex showing intrusion names and deposit areas as named in this
report. Taken after Chandler (Figure 3.1) in Miller et al. (2002). Intrusion and/or formation abbreviations
are as shown in following list. Those units listed as not mentioned in report have no recorded exploration
drilling. Most deposit areas mentioned in text are shown on map in italics.
BBC-Beaver Bay Complex

BEI-Bald Eagle intrusion
BIF-Biwabik Iron Formation (Paleoproterozoic)
BH-Brule Lake and Hovland gabbros (Brule Lake intrusion)
BLI-Boulder Lake intrusion
BRD-Beaver River diabase (not mentioned in this report)
CLG-Crocodile Lake gabbro
CLLS-Cloquet Lake layered series of BBC
DLS-Layered Series at Duluth
EG-Ely Greenstone (Archean) (not mentioned in this report)
EPB-Ely’s Peak Basalts (not mentioned in this report)
GIF-Gunflint Iron Formation (Paleoproterozoic)
GLI-Greenwood Lake intrusion
GPD-Grand Portage dikes (not mentioned in this report)
GPH-Grand Portage basalts and Hovland lavas (not mentioned in this report)
GRB-Giants Range batholith (Archean)
HCT-Houghtaling Creek troctolite (not mentioned in this report)
LI-Logan intrusions
LP-Leveaux porphyry (not mentioned in this report)
PLI-Poplar Lake intrusion
PRD-Pigeon River diabase (not mentioned in this report)
PRI-Partridge River intrusion
RF-Rove Formation (Paleoproterozoic)
SCG-Silver Creek gabbro (not mentioned in this report)
SKI-South Kawishiwi intrusion
SLB-Schroeder-Lutsen basalts (not mentioned in this report)
SLG-Sawmill Lake gabbro (not mentioned in this report)
SLI-Sonju Lake intrusion
TF-Thomson Formation (Paleoproterozoic)
TI-Tuscarora intrusion
VF-Virginia Formation (Paleoproterozoic)
VGC-Vermilion Granitic Complex (Archean)
WMI-Western Margin intrusion
46
deposit areas that are not classified into the named intrusions and those drilled some distance
away from the basal contact are listed last.
DULUTH LAYERED SERIES (DLS)
The Duluth Layered Series (DLS; Layered Series at Duluth of Miller et al., 2002)
includes all exposures of the Complex in the Duluth area and continuing to the area
north of Duluth near Island Lake. This area also includes extensive outcrop of North
Shore Volcanic Group (NSVG) volcanic and sedimentary rock, as well as diabase sills
and dikes. Footwall rocks to the Complex in this area are either localized patches of
NSVG basalts or the Thomson Formation (Paleoproterozoic metasedimentary rocks
considered equivalent to the Virginia Formation).
There is minimal recovered drilling in this area, represented by a few core holes drilled
by MDNR, scattered geotechnical drilling (not reported here), and data from water
well drilling. There is extensive outcrop control in this area. The DLS is described
in detail in Miller et al. (2002).
Duluth, Fish Lake, and Twig Holes
The seven holes in the Duluth Layered Series includes the two “Fish Lake holes”,
drilled on Island Lake by the MDNR (data summarized in MDNR Report 251,
Dahlberg, et al., 1987; Severson, 1995; and Sassani, 1992), two holes in the Twig
area drilled by MDNR, two water wells in Duluth, and a hole drilled jointly by
Minnesota Power & Light and the MDNR.
No extensive publically available exploration work has been done on this intrusion,
but Millers outcrop traverse geochemical sampling has shown horizons prospective
for PGE mineralization (Miller et al., 2002).
BOULDER LAKE INTRUSION (BLI)
The Boulder Lake intrusion extends from the Island Lake-Boulder Lake area north
of Duluth to a point about sixteen miles north-northeast, and then hooks east and
back south to a point about fifteen ground miles from Island Lake. Five drilling areas
are outlined in this intrusion. They are: Boulder Lake South (Grid V), Boulder Lake
Central (Grids VI and VII), Boulder Lake North (Grid IV), and Grid VIII. These are
all grids defined by Phelps Dodge Corporation. The short area descriptions below are
summarized from Severson (1995), which has more complete description and cross-
sections for these localities.
47
Boulder Lake South (Grid V )
Three core holes were drilled by the Phelps Dodge Corporation in what they referred
to as Grid V. These holes intersect an OUI that intrudes both troctolitic-gabbroic
rocks and an inclusion of basalt. This grid is located on land between Island Lake and
Boulder Lake.
Boulder Lake Central (Grids VI and VII)
Near the southwestern portion of the Boulder Lake Reservoir, Phelps Dodge Corp.
drilled 10 core holes in what they referred to as Grids VI and VII. Within Boulder
Lake Central there are no recognized correlative igneous units. Rather, each hole
intersects a completely different package of rocks that bear no similarities to nearby
drill hole rock types. Footwall rocks are intersected in the bottom of only one drill
hole (VII-7).
Several thin OUI intervals are present in two drill holes in the Boulder Lake Central
area and may represent apophyses off of a much larger body.
Boulder Lake North (Grid IV)
A total of 12 core holes are available in the Boulder Lake North area, referred to as
the Grid IV area by Phelps Dodge Corporation (1970 - 9 holes) and by ASARCO
(1968 - 3 holes). No footwall rocks are encountered in any of the drill holes at
Boulder Lake North. This grid is located on the shore of the northernmost part of
Boulder Lake.
Late pods and lenses of OUI are present in 7 of the 12 holes at Boulder Lake North.
The OUIs vary from single thick intervals (or thick pods) to abundant thin intervals.
Grid VIII
Two holes were drilled by Phelps Dodge Corporation on their Grid VIII. These holes
intersect moderately magnetic, oxide-bearing troctolitic and gabbroic rocks that
correspond to a north-northeast-trending aeromagnetic high. This grid is located
about one-half mile east of County Highway 4, three miles north of the intersection
of County Highway 4 and Three Lakes Road.
WESTERN MARGIN INTRUSION (WMI)
The Western Margin intrusion (WMI) extends from about four miles north of Boulder
Lake for thirty miles north-south and extends about six miles eastward from the basal
contact. It includes eight exploration areas: Boulder Creek (Grid I), Marshall Trail
(also known as Section 34 by USS), Harris Lake, Cloquet Valley (CV holes), Cloquet
Valley North, Otto Lake, Linwood Lake, and Whiteface Reservoir.
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As with the previous two intrusions, the WMI is described in Miller et al. (2002), and
there is detailed geologic description and cross-sections of the drilling areas in
Severson (1995). These descriptions are generalized from Severson.
Boulder Creek (Grid I)
In 1969, Phelps Dodge Corporation drilled 12 core holes in an area they referred to
as Grid I. Units intersected in these holes consist of heterogeneous troctolitic rocks,
troctolitic to gabbroic rocks with a well developed plagioclase lamination, and a
disjointed, stratabound OUI. No footwall rocks are present in these holes. The linear
distribution of the OUI at Boulder Creek may be related to an inferred north-trending
fault zone. The Boulder Creek grid is near the southern tip of the WMI about two
miles west of County Highway 4.
Marshall Trail (A.K.A. Section 34)
U. S. Steel Corporation (USS) drilled six core holes into a magnetic high in the
Section 34 area. Three of the holes intersect an Oxide-bearing Ultramafic Intrusion
(OUI) that is present throughout the entire length of the holes. The remaining three
holes intersect numerous apophyses of OUI that alternate with anorthositic host
rocks. This area is along St. Louis County Highway 4, just south of the “Kelsey
Brimson Road”, where the Marshall Trail intersects St. Louis County Highway 4.
Harris Lake Drill Holes
U. S. Steel Corporation leased state lands in the vicinity of Harris Lake (about 8 miles
southwest from Fairbanks) on the basis of a coincident magnetic high and strong
airborne electromagnetic (EM) anomaly. After conducting geophysical surveys in the
area, they drilled three vertical holes in 1967-68. Because the holes intersected mainly
serpentinized ultramafic rocks with no visible sulfide mineralization, USS dropped the
state leases. Shortly after this period, Phelps Dodge Corp. leased the same lands and
subsequently drilled two inclined holes into the same magnetic-EM conductor in
1971. These holes are located approximately 2.5 miles east of the basal contact
subcrop. No footwall rocks are present in the holes.
CV Holes
The two “CV” drill holes (Cloquet Valley?) were drilled by Exxon in 1974. CV-1 is
about four and a half miles south-southeast of Whiteface Reservoir, and CV-2 is
about three miles southeast from the reservoir.
Cloquet Valley North
A single drill hole at Cloquet Valley North was drilled by W.S. Moore two miles east
of Linwood Lake and about one-half mile west of County Highway 4.
49
Linwood Lake Drilling
This area is along the east shore area of Linwood Lake, west of the “Camp 26 Truck
Road”. Four core holes are available for the Linwood Lake area and include: 26012
-drilled by U. S. Steel Corporation; CL-1 - drilled by W.S. Moore Co.; SL-1A-
MDNR and SL-1B-MDNR - both drilled by the MDNR. All of the holes are collared
in rocks of the Duluth Complex. Several outcrops of the Virginia Formation are also
present in the Linwood Lake area. These outcrops show a progressive increase in the
amount of deformation and metamorphism towards the basal contact of the Complex.
Both drill hole and outcrop data suggest that the basal contact of the Complex in the
area is near vertical at the surface. This condition is indicated by:
1) bedding planes in the Virginia Formation that become progressively steeper

and more north-trending closer to the contact; and,
2) drill hole SL-1B-MDNR, located approximately 700 feet eastward from the
contact, does not intersect the Virginia Formation at a total drilled depth of
1,008 feet.
Unfortunately, there are no correlative stratigraphic units in the Linwood Lake area
based on the information from these four holes. Several thin OUI horizons, varying
from 1 to 4 feet thick with 15%-30% oxides, are present in portions of 26012 and
CL-1. Drill hole SL-1B-MDNR intersects numerous sedimentary hornfels inclusions
and noritic rocks at many intervals - it is presumed to be very close to a steeply
dipping basal contact. Sl-1A-MDNR was drilled a few feet from SL-1B-MDNR and
abandoned at about 190 feet.
Nearby outcrops of the Virginia Formation are characterized by interbedded argillite

and graywacke (Bouma B and/or D with minor C). The rock types are very similar
to the rocks intersected in drill holes to the immediate north in the Whiteface
Reservoir area. What makes these outcrops unique is that they record a progressive
increase in the amount of deformation, metamorphism, and partial melting toward the
contact with the Complex.
Outcrops in the northern part of the area consist of gently southward dipping
sediments that show a gradual increase in the amount of dip toward the contact.
Outcrops farthest away from the contact display normal dips of 5°-10° to the south;
whereas, outcrops that are closest to the contact show an increase in dip to about 40°-
50° (locally 60°-75°) to the east beneath the Complex. Also at this locale, the
sedimentary rocks contain thin wisps of leucocratic partial melts that parallel the
bedding plane trend.
Outcrops in the southern part of the area exhibit north-trending bedding-planes that
are highly deformed and recrystallized adjacent to the Complex. Consistent dips of
80°-90° toward the east are present within the deformed rock. Rock types can be
divided into two categories - the DISRUPTED unit and the RXTAL unit of the
50
Virginia Formation. Both of these footwall units have been noted elsewhere (and are
described later in this report) along the margin of the Duluth Complex, e.g. at the
Babbitt (Mesaba), Dunka Road (NorthMet), and Water Hen deposits.
Whiteface Reservoir
This area is near the intersection of the “Camp 26 Truck Road” and St. Louis County
Highway 16, north-northeast of the Linwood Lake exploration area. Four core holes
were drilled into rocks of the Duluth Complex in the Whiteface Reservoir area by
United States Steel Corporation (USS). An additional two holes were drilled into
geophysical conductors within the Virginia Formation to the west of the Complex by
AMAX (drill hole BC-80-1) and by W.S. Moore Co. (drill hole CL-3). The drilling
was not detailed enough to provide any information on the attitude of the basal
contact in the Whiteface Reservoir area.
Otto Lake
One hole was drilled at Otto Lake by Lehmann Exploration Management in 1983.
This is a short (209 feet) hole and has not been logged by NRRI. The targeting
reason for this hole is unknown. Otto Lake is located about 4 miles south-southeast
of Fairbanks, about 3-4 miles northeast of the Harris Lake exploration area.
DULUTH COMPLEX ANORTHOSITIC SERIES (AS)
The Anorthositic Series drill holes are within large (and not necessarily contiguous)
areas of undivided anorthositic rocks (see Miller et al., 2002) not necessarily related
to one another. This group includes drill holes in the area of the Bear Lake inclusion,
the single drill hole at Thomsom Lake (Grid X), plus holes in the area of the Brimson
quadrangle further to the east, and the Mt. Weber quadrangle to the north of Two
Harbors.
Bear Lake Inclusion Drill holes
Numerous outcrops are present to the west of Bear Lake in the southeastern corner
of T.55N., R.13W. This area is about eight ground miles due east of the Section 34
(Marshall Tail) area drilled by USS. This area is associated with a 2,500 gamma
aeromagnetic anomaly that was drilled by the MDNR in 1984 (drill hole BL-1-
MDNR, Sellner et al., 1985, east side of Cloquet River, near campground). At least
two major rock types are present that include an inclusion of magnetic basalt that
overlies and is in sharp contact with a package of oxide-bearing gabbroic rocks.
Outcrop data suggest that both the inclusion and the gabbroic rocks dip about 10°-20°
toward the southeast. Drill hole BL-1-MDNR gives a minimum thickness for the
inclusion of 563 feet (the hole was collared and terminated in magnetic basalt).
51
Even though the basaltic rocks lack obvious volcanic features, the unit is believed to
be an inclusion of magnetic basalt derived from the Keweenawan hanging-wall
material. Sharp contacts, of 15° to the east, with the underlying gabbroic rocks are
observed in two close-spaced outcrop areas. Similar material, also referred to as
magnetic basalt, is present elsewhere in the Duluth Complex: 1) within portions of the
Colvin Creek Body described by Patelke (1996); 2) associated with an anorthositic
inclusion within the Highway One Corridor of the South Kawishiwi intrusion (where
it is referred to as the "INCL" unit, Severson, 1994); and 3) in a drill hole (IS-1-
MDNR; Sellner et al., 1985) near Isabella, Minnesota (J. Miller, pers. comm., to M.
Severson, 1994).
One hole was drilled in this area by Franconia Minerals in 2002 (FCV-02-1). Only the
location and length data are known for this hole from abandonment reports. No core
has been submitted to the MDNR. The hole appears to test the west margin of the
inclusion.
Thomson Lake (Grid X)
One hole was drilled by Phelps Dodge Corporation in an area they termed Grid X.
The hole (X-1) was drilled to test a sinuous, north-trending magnetic anomaly. Rocks
encountered in the hole consist of troctolitic rocks with a thick dunite layer. No
footwall rock types are present in the inclined (-45°) 613 foot deep hole. This hole
was skeletonized with little sample remaining. Severson (1995) placed this
exploration area in the Boulder Lake intrusion.
PARTRIDGE RIVER INTRUSION (PRI)
Moving northward from the Western Margin intrusion (WMI) we pass into the
Partridge River intrusion (PRI). The Partridge River intrusion is arguably the most
studied portion of the Duluth Complex, at least in drill core (~1,000 drill holes). It
is host to the Babbitt Deposit (formerly known as MinnAMAX and now under
development by Teck Cominco as the Mesaba deposit), the Dunka Road deposit (now
called NorthMet by PolyMet Mining), plus smaller projects at the Allen area, Wetlegs,
and Wyman Creek areas. Lesser prospects are found at Skibo Road and Skibo South.
Besides the above copper-nickel projects, there are ilmenite-rich “Oxide Ultramafic
Intrusions” (OUIs) with possible economic potential at Longear, Longnose, Section
17, Section 22, Skibo, and Water Hen.
The database subdivides a few of these into smaller sets of holes, generally based on
how NRRI has grouped them on maps or for our own internal studies. These include
“Babbitt Underground” for the drilling at the Local Boy massive sulfide deposit,
“Longear/Longnose” for a hole between the two, “Skibo Road” for a single hole,
“Wetlegs West” for about six holes, “Wetlegs-Siphon” fault area for one hole, and
there is some question for holes near Wyman Creek as to whether they should be
included as part of the Wyman Creek deposit.
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Also, because the Babbitt B-1 (Bear Creek) grid crosses from the Partridge River
intrusion into the South Kawishiwi intrusion, covering the Babbitt and Serpentine
deposits, we split the areas associated with that grid into five areas: “Babbitt” (holes
in the Partridge River intrusion portion of the main Babbitt deposit); “Babbitt
Underground” for the Local Boy area (on the B-1 grid, but with 5 digit numbers);
“Babbitt Valley” for drill holes on the B-1 grid, collared in the South Kawishiwi
intrusion and located in the area between the main Babbitt deposit and the Peter
Mitchell taconite pit of NorthShore Mining Company; “Babbitt/Serpentine” for widely
spaced drill holes on the eastern third of the B-1 grid, collared in the South Kawishiwi
intrusion, but not clearly a part of either the Babbitt or Serpentine deposits; and lastly
the “Serpentine” deposit proper. There are a few drill holes drilled by companies
other than Bear Creek or AMAX listed as being within the Babbitt deposit.
Rocks of the PRI consist of varied troctolitic and gabbroic rock types that have been
subdivided into eight igneous stratigraphic units, plus some cross-cutting OUIs and
other units. These igneous rocks overlie Virginia Formation, and where the Virginia
Formation was removed during intrusion and assimilation, the Biwabik Iron
Formation. Nowhere in the PRI is the footwall (basal) contact with Archean granitic
rocks, as it is to the northeast in the South Kawishiwi intrusion. The PRI units have
been described in detail by Severson and Hauck (1990), and there is further
description and references in Miller et al. (2002).
Water Hen
Since the late 1950s, 37 holes have been put down into the Water Hen deposit by
various companies. Water Hen is east of St. Louis County Highway 130, two miles
north of St. Louis County Highway 16 and about eight miles due south from Hoyt
Lakes. Most of these drill holes intersect an OUI body within troctolitic rocks, and
only four holes intersect the footwall Virginia Formation contact. This drilling mainly
targeted the oxide mineral potential of the deposit. While Water Hen is in the PRI,
it exhibits little of the “stratigraphy” typical of the majority of the PRI. The troctolitic
host rocks may be correlative with Unit 5 of the PRI (Severson, 1995).
The Water Hen area has been studied extensively, including work by: Mainwaring
(1975), Mainwaring and Naldrett (1977), Dahlberg et al., (1987), and Strommer et
al. (1990). See Severson (1995) for detailed discussion and references for the Water
Hen area.
Skibo-South (Grid II)
A total of seven drill holes are present in the Skibo-South area, or the Grid II area,
as referred to by the Phelps Dodge Corporation. One hole is collared in the Virginia
Formation (II-2), one hole intersects a thick OUI body (SR-1), and the remaining five
holes intersect weakly-mineralized troctolitic rocks. The nature of the basal contact
of the Complex at Skibo-South is unknown as only one hole encountered footwall
53
rocks (Severson, 1995). This area is about six miles south-southeast from Hoyt
Lakes.
Skibo
Twenty holes were drilled into an OUI body in the Skibo area, about four miles south-
southeast from Hoyt Lakes. INCO drilled 18 of the holes during 1956-57 and 1969;
none of the core for these holes remains for examination. Drill hole DDH-3 was
drilled by an unknown company (INCO?) and only skeletonized core remains for this
hole (core stored at the MDNR). United States Steel Corporation drilled hole 27016
in 1982. This single USS hole represents the only complete core available for the
Skibo area (Severson, 1995).
Section 22
Core from six holes is available for the Section 22 area. This area is about three miles
southeast from Hoyt Lakes. One hole is collared in the Virginia Formation, and the
remaining holes are collared in the Duluth Complex; presumably in Unit 1 of the PRI.
Three of these holes also intersect OUI rocks that are present over both thick and thin
intervals. Drill hole data suggest that the basal contact is not as steep as at the Allen
area to the north (Severson, 1995).
Allen Exploration Area
The Allen area is located immediately south of the Wyman Creek deposit, and due
east of Hoyt Lakes. This area was drilled by Bear Creek Mining Company (1958-
1960) and Exxon Minerals Company (1976-1979). The holes encounter troctolitic
rocks that are roughly correlative with units of the Partridge River Troctolite Zone
(PRTZ in MGS RI-58 and Map 119, Miller et al., 2001, 2002 ) that are present to the
north in the Wyman Creek deposit. Many of the PRI marker beds that are clearly
present at Wyman Creek begin to "lose their identity" to the south toward the Allen
area, and correlation of units becomes progressively more difficult in a southerly
direction. The mapped contact of the Complex with the Virginia Formation in the
Allen area is based on the distribution of rock types intersected in the collars of drill
holes (Severson, 1995).
It is important to note that the Wyman Creek/Allen area marks a dramatic change in
the trend of the western contact of the Complex. In this area, the contact exhibits a
rapid change from a northeasterly trend at Wyman Creek to a nearly north-south trend
in the Allen area. Drill hole data at this inflection point indicate that the attitude of
the basal contact beneath the Complex steepens from a 15°-25° dip (to the southeast)
at Wyman Creek, to 60° or more (to the east) in the Allen area (Severson, 1988).
Because the configuration of the basal contact is almost cliff-like in the Allen area, the
entire section of troctolitic rocks intersected in drill holes is in close contact with
footwall rocks and is probably contaminated via assimilation of the country rocks.
54
Thus, correlation of igneous units is hampered by a thick package of contaminated
and heterogeneous rocks in close contact with the footwall (Severson, 1995).
Wyman Creek
The Wyman Creek area includes about 35 drill holes, most by U.S. Steel, with a few
each by Bear Creek and Exxon. Most of these drill holes penetrate Virginia
Formation footwall, with a few being collared in the Virginia Formation.
Note that in addition to the drill holes in this database, NRRI holds some drill core
from the former LTV Steel Mining Company mine, about one to one and a half miles
north of the Wyman Creek area. This core is from the upper parts of iron-ore mining
development drill holes, and penetrates the base of the Virginia Formation into the
upper marble unit of the iron-formation (the A submember). This core represents
some of the better preserved Virginia Formation core available (it is usually disposed
of by the iron mines) and is relatively unmetamorphosed argillite, and carbonaceous
argillite, with thin limestone / chert units. Sulfide content is up to 5% of the rock in
the carbonaceous argillite, generally nearer the base, and is marcasite dominated.
These rocks may be the unmetamorphosed equivalent of the “bedded pyrrhotite unit”
commonly seen where the Virginia Formation is metamorphosed by the Partridge
River intrusion.
The data that NRRI has for this core, along with LTV drill logs for some drill holes,
is on file at NRRI and is available for use. It was not put into this database due to
time constraints for correcting locations and other data.
Wetlegs and Wetlegs West
The data for Wetlegs and Wetlegs West includes forty eight drill holes, sixteen by
INCO (with no core remaining), eighteen by Bear Creek, and twelve by Exxon. The
rocks of the Complex intersected in holes at Wetlegs consist of the Partridge River
Troctolite Series (PRTS-Severson and Hauck, 1990), or, as it has been more recently
called, the Partridge River Troctolite Zone (PRTZ; Miller et al., 2002).
Section 17 OUI
This is one of three OUIs (Oxide Ultramafic Intrusions) lying along a trend in the PRI.
It is located due east of the Wetlegs area. There is one INCO hole and six USS drill
holes in this area. All but one are angled holes, none penetrate footwall, and the bulk
of the footage is in OUI rocks.
Longear OUI
This OUI is located directly south of the Wetlegs area, and three holes were drilled
by American Shield in the 1970s and 1980s to evaluate the potential for massive
oxides, particularly as an ilmenite feedstock for synthetic rutile processes.
55
Longnose OUI
This is an OUI located a few miles south and west of the OUI at Longear, besides
drilling here by American Shield in joint venture with NICOR, bulk samples have been
taken from this body with the aim of metallurgical testing for suitability as an ilmenite
feedstock for synthetic rutile production. Some of this massive oxide material is
stockpiled at the Coleraine Minerals Research Laboratory of the NRRI.
Dunka Road (NorthMet)
Dunka Road (NorthMet) is a United States Steel (USS) property drilled out in the
1960s and early 1970s (114 drill holes, plus a few by other companies). Currently
(2003), it is under lease by USS to PolyMet Mining of Vancouver, British Columbia.
PolyMet’s precursor company, Fleck Resources, resampled virtually all of the pulps
from the original sampling. They re-ran copper, nickel, and sulfur, as well as a suite
of PGEs. PolyMet has also drilled another ninety holes in the deposit, some reverse
circulation and some diamond core. The material from this drilling formed a bulk
sample for metallurgical testing as well as providing confirmation of the historical
drilling by USS.
PolyMet’s published plan is to mine the deposit as a copper-nickel deposit with credits
from PGEs, gold, cobalt, and other metals. Processing will be by a proprietary
hydometallurgical method known as PlatSol.
Geerts et al., 1990, Geerts, 1991, and 1994, completed the most recent and
comprehensive public studies on the deposit. The location, depth, and geology for
the USS drilling at Dunka Road in this database come from Geerts. Three
confidential reports by the NRRI have been done recently, but no information from
them is included in this dataset.
PolyMet has released no detailed data on their drilling. The location and downhole
data in the database for the PolyMet drill holes comes from abandonment reports
turned in to the Minnesota Department of Health. Older press releases by the
company have some assay composite values.
Babbitt (MinnAMAX or Mesaba)
Like the Dunka Road project, the Babbitt deposit has a long history of interest.
Ownership is a mix of state lands and lands controlled by the Longyear Mesaba Trust.
The Babbitt deposit is located between the Dunka Road and the Peter Mitchell Mine
of NorthShore Mining, east of the Dunka Road (NorthMet) deposit and about eight
miles due south from the town of Babbitt.
Bear Creek was responsible for about 208 surface drill holes at Babbitt. AMAX
drilled about 224 surface holes, sunk a 1,700 foot deep shaft, and drilled 230 holes
56
from underground drifts (3,800 feet of drift) at the Local Boy massive sulfide. This
total includes thirty surface holes at Serpentine in the South Kawishiwi intrusion and
twelve holes between Babbitt and Serpentine proper on the same grid. The database
shows 473 surface drill holes in the Babbitt/Serpentine area, some are wedges on the
original drilling, some are iron-formation drill holes from Reserve Mining
(NorthShore Mining) included here for stratigraphic control, and some were drilled
by companies other than Bear Creek or AMAX.
None of the lithological data for the underground drill holes at Babbitt (the Local Boy
drilling) has been included in this database. The logging has been done for virtually
all holes, but the final report is not published (Severson and Zanko, in prep.). The
data are publically available, but are not yet digital. The original assays for the
underground work are included here in digital format. NRRI and MDNR files also
have about 500 records for rib sampling in the drifts. These rib sample data are digital
in Patelke (1994).
Currently (2003), the Babbitt (now Mesaba) deposit is undergoing pre-feasibility

study by Teck Cominco as a potential copper-nickel mine, with credits for PGEs,
gold, cobalt, and other metals deferred to the future when processing technology
catches up with mineralogy. This deposit (and probably all Partridge River copper-
nickel deposits) has a difficult mineralogy where much of the copper metal is in
cubanite, a copper-iron sulfide similar to chalcopyrite, but with only about 25%
copper instead of the 35% copper of chalcopyrite. The sulfide concentrate may not
be amenable to pyrometalurgical smelting, especially in regards to recovery of any
nickel metal.
Besides Miller et al. (2002), the most recent public works on the Babbitt deposit are
the three reports completed by the NRRI in the mid-1990s for Arimetco International
during their evaluation of the deposit. Arimetco never completed their evaluation and
went bankrupt in 1999. These reports include: Part “A” (Patelke, 1994) a digital
compilation of assay data, drill hole location data, and drill hole location map. Also
included is an index of other work conducted on these drill holes, such as theses,
polished section inventory for NRRI, metadata, if whole rock geochemistry samples
have been taken, etc. Part “B” of these reports (Severson et al., 1994) covers the
geology of the deposit in plan view with five plates detailing various geologic
horizons. Part “C” of this series (Severson et al., 1996) includes more plan view
maps, and twenty five detailed cross-sections at one inch equals two hundred feet.
Part “D”, as yet unpublished (Severson and Zanko, in prep), details the geology of the
Local Boy massive sulfide with numerous cross-sections at one inch equals fifty feet
(see comment above about this geology data being absent from the database). Hauck
and Severson (2000) published the precious metals data for the Local Boy area
collected for Arimetco in the mid 1990s.
57
VIRGINIA FORMATION DRILL HOLES
The database contains a number of scattered drill holes that do not penetrate the
Duluth Complex. They collar in and pass through either Virginia Formation (VF)
and/or the Biwabik Iron Formation (BIF). They are included here for two purposes.
First, the Virginia Formation drill holes along the western margin of the Complex,
referenced in Severson’s South Complex report (Severson, 1995) help define the
limits of the Complex, as well as demonstrating that bedding angles in the Virginia are
steepening to the south. Future work in this area may better define the nature of the
basal contact of the Complex through this area. These drill holes will be useful in that
study. These drill holes are shown on cross-section in the Severson (1995) report.
Secondly, the Virginia Formation and Biwabik Iron Formation drill holes along the
northwest margin of the Complex, from Wyman Creek to the Dunka Pit deposit, help
to define the location of the basal contact and its geometry in that area.
Also see the reference to the LTV Virginia Formation and iron-formation drill holes
in the Wyman Creek area description.
SOUTH KAWISHIWI INTRUSION (SKI)
Northeast of the Partridge River intrusion is the South Kawishiwi intrusion (SKI).
This intrusion extends along the basal contact from the Serpentine deposit and Dunka
Pit iron mine area, of LTV Steel Mining Company, and east just into the Boundary
Waters Canoe Area Wilderness (BWCAW) south of the Kawishiwi River, east of
Minnesota Highway 1.
The South Kawishiwi is heavily drilled, with almost 800 drill holes and wedges, but
unfortunately much of this core is gone or unavailable. About 290 INCO drill holes
and about 165 LTV Steel Mining Company (Erie Mining at the time of drilling) drill
holes have no core remaining, and about 70 drill holes and wedges are part of the
ongoing Birch Lake exploration program and are not available to the public. Many
of the other drill cores are lost or incomplete.
Work in the South Kawishiwi intrusion is made more complicated by a more complex
geology than that of the Partridge River intrusion. At Babbitt and Dunka Road, as
well as throughout most of the Partridge River intrusion, the tabular stratigraphic
format of wide, but thin, major (map or cross-section) units works well in describing
the igneous stratigraphy. This is especially true in the footwall area. In general, units
in the Partridge River intrusion do not seem to repeat. However, in the South
Kawishiwi intrusion the drill hole data must be put on cross-section and examined in
context to fully make sense, as there are discontinuous horizons, many isolated
textural and mineralogical changes, vertical repetition of many units, more inclusions
of uncertain origin, more interfingering of rock types and map units, and less of an
overriding and relatively clear igneous stratigraphy. The South Kawishiwi is made up
of many sub-intrusions or sub-pulses, as is the PRI, but the localized nature of the
58
drilling, combined with the absence of most of the core makes understanding the
intrusion in the neat terms of the PRI problematic.
Serpentine
The Serpentine area is classed as both part of the Babbitt deposit and as a separate
deposit. The drill hole numbering at Serpentine is continuous and intermixed with
Babbitt, as both were drilled by Bear Creek/AMAX on the same grid, at the same
time.
The Serpentine drilling was done to target a magnetic high or electromagnetic

conductor associated with a massive sulfide at the basal contact. This massive sulfide
is mostly pyrrhotite. Overall, the Serpentine deposit has average copper-nickel values
slightly lower than the Babbitt deposit (Zanko et al., 1994). The massive sulfide of
the Serpentine deposit (or very similar material) crops out at the south margin of the
Peter Mitchell taconite mine of Cliffs NorthShore Mining.
Zanko et al. (1994) and Severson (1994) describe this area in the most detail, with
Miller et al. (2002) providing the most recent background information on the South
Kawishiwi intrusion.
Dunka Pit
Drilling at Dunka Pit iron mine includes drilling by Erie Mining Company (LTV Steel
Mining Company) for taconite of the Biwabik Iron Formation beneath the Duluth
Complex, and drilling by Newmont, Bear Creek, Duval, and Exxon for definition of
the copper-nickel material above the iron-formation.
Much of the LTV core is lost, and the best records were notebooks of drill data kept
at LTV, which is now closed. Presumably Cleveland Cliffs Incorporated kept these
data after their 2002 purchase of LTV Steel Mining Company after the LTV
bankruptcy.
A large amount of sulfide-bearing Duluth Complex material was moved to mine the
iron ore at the Dunka Pit. This material is stockpiled on the south side of the Dunka
Pit iron mine area.
Birch Lake
Birch Lake is an ongoing exploration and development project managed by Lehmann

Exploration Management for the Beaver Bay Joint Venture. The primary target here
is a deep zone or zones of higher grade platinum group minerals with associated
copper-nickel-cobalt values.
As an ongoing project, much of the data developed since 1995 for Birch Lake is held
confidential by the company. For this database, we used data from drill hole
59
abandonment reports for the holes drilled since 1995. For the most part, the Birch
Lake data is primarily included as “placeholder” data to remind geologists that work
is ongoing there, and once project development is further along, more data may be
forthcoming from the company.
Drilling on this property includes seven holes by Duval (with core available) and
seventy-three holes and wedges by Lehmann Exploration Management.
The Birch Lake area straddles the county line between St. Louis and Lake counties.
It is located on the southern shore of Birch Lake in the Bob Bay area, two or three
miles east of the Dunka Pit iron mine and exploration area.
See the survey table discussion section for comments about the treatment of the many
wedge holes at Birch Lake with no publically available orientation data.
Little Lake Road (Birch Lake North)
The Little Lake Road area (Birch Lake North by Peterson, 2001) could also be
classed as a part of the Birch Lake area. The area parallels the north side of Birch
Lake, west of Minnesota State Highway 1. The drilling here (fifteen holes) is older
work by INCO and Bear Creek, with two holes in 1990 by Lehmann. Peterson et al.
(2001 and in prep.) have collected some surface samples and refined the geologic map
for the area, which is a small area of Duluth Complex at the corner of a USGS
quadrangle sheet covering mostly Archean granitic rocks.
Maturi
Maturi (also historically listed as Maturi Road) lies on the south side of Birch Lake
and the Kawishiwi River, west of Minnesota Highway 1, and is a deep mineralized
zone below an extensive thickness of homogenous troctolitic rocks. Virtually all
previous work in this area was by INCO (43 holes), who still control the federal
leases. There are a few Hanna Mining and Duval drill holes (10 holes), and
Wallbridge Mining put down one hole in 2000 to twin an INCO hole.
The geology of this area is covered in Severson (1994) and Miller et al. (2002).
Peterson (2002) has done some re-definition of ore zones based on mineralization
styles related to the above mentioned homogenous troctolitic rocks.
The database includes “Maturi Underground” for twelve holes INCO drilled from a
drift, and a single hole for “Maturi Extension” to the south. We did not completely
succeed in reconciling the number of underground drill holes for which we have
records with the available drift map. MDNR or INCO may have better maps.
60
South Filson Creek
South Filson Creek area is a mineralized zone relatively high up in the Complex.
There is no evident relation to the footwall rocks, which is not the case for most
Duluth Complex sulfide deposits. The deposit is located south of the Spruce Road
deposit on Forest Road 181 (Spruce Road), east of Minnesota State Highway 1. This
is a property originally drilled by Hanna in the 1960s with one drill hole by Duval
(about 28 drill holes total). An NRRI report was done on this area in 1990 (Kuhns
et al.). This report was done before any South Kawishiwi intrusion igneous
stratigraphy had been outlined, so no unit definitions were given. Most likely all of
the South Filson Creek deposit is in the “AT&T” unit of the SKI (Severson, pers.
comm., 2003).
The 1990 NRRI report indicted some PGE potential. The deposit is currently under
lease to Encampment Resources of Jelm, Wyoming. William Cronk at the University
of Minnesota Duluth (UMD) began a masters thesis on this area in the early 1990s.
It was not finished, but some of his work may be on file at UMD.
Spruce Road
Spruce Road (also east of Highway 1 along the south side of the Kawishiwi River) is
another large INCO project. Along with Maturi, it was one of the two they intended
to develop in the 1970s.
There are over 200 drill holes in the Spruce Road area, but almost no core available.
Most of this drilling was by INCO with a few drill holes by Bear Creek and the United
States Bureau of Mines (USBM). The three USBM holes are among the first copper-
nickel exploration holes drilled into the Complex in 1953.
The database groups these holes into Spruce Road, Spruce Road East, Spruce Road
West, and Spruce Road Southwest. These area names have no meaning outside of
how NRRI has classed these drill holes at various times for various projects.
Highway 1 Corridor
The Highway 1 Corridor is a Severson (1994) term for a group of deep holes along
Highway 1 to the south of the South Kawishiwi River. These are the deepest holes
in the Complex. The seven holes average about 4,300 feet in depth, with the deepest
being 5,225 feet deep. This is a mix of drilling by Newmont and Duval. The holes
intersect a thick package of anorthositic rocks, presumably a large raft of earlier
Anorthositic Series, that overlies a thin zone of SKI copper-nickel mineralization near
the basal contact. Peterson (2002) refers to part of this area as the “Maturi
Extension”, and the raft as a large anorthositic “pillar”.
61
BALD EAGLE INTRUSION
There are about ten drill holes scattered throughout the Bald Eagle intrusion (BEI).
The exploration areas in the Bald Eagle intrusion include Slate Lake East, Tomahawk
Trail, and Fools Lake. These are not well defined prospective areas, but simply names
taken from drilling areas. The BEI is located to the south and east of the South
Kawishiwi intrusion, and to the north of the Greenwood Lake intrusion. Note that
drill hole NE-2-MDNR may collar in the Greenwood Lake intrusion or a raft of
Greenwood Lake intrusion rock in the Bald Eagle intrusion. See Miller et al. (2002)
for more description and references.
MISCELLANEOUS INTRUSIONS–GUNFLINT CORRIDOR
The Gunflint Corridor drilling penetrates the Poplar Lake intrusion (PLI), Tuscarora
intrusion, Brule Lake intrusion, Crocodile Lake intrusion (CLI), and the Logan Sills.
This area lies along the Gunflint Trail, Cook County Highway 12, which connects
Grand Marais to Saganaga Lake on the Minnesota-Ontario border. This is not a
single group of drill holes, but many holes over a fairly wide area. All drill holes in
Cook County are broadly defined as being in this group. Part of the reason for
defining this as the Gunflint Corridor is the difficulty in access from the west. These
areas are best accessed from the east along the Gunflint Trail.
The information given in the database for the Gunflint Corridor drill holes is based on
historic logs, and the “quick scan” logging of drill holes by Severson in preparing data
for the Duluth Complex mapping project (Miller et al., 2002). Because fully
describing these holes would require further logging and probably an attempt at a
definition of an igneous stratigraphy for this relatively unstudied area, these
descriptions are much abridged and abbreviated. The main purpose of the data given
here is to define general rock types to align with any assays we find for these drill
holes in the future and to show that some Duluth Complex (or other Keweenawan
intrusive) rock has been drilled in this area. As with all of the deposit areas, interested
parties should consult the records held at the NRRI and the MDNR prior to doing any
projects in the area.
The drill hole locations for the Gunflint Corridor holes have been problematic. The
drill hole locations here are roughly those in Miller et al. (2002), and represent what
we think are valid locations, but much of the written and unwritten record of work in
this area has been lost over the last few years as older geologists have retired or
moved on to other projects outside of Minnesota. Most of this company work was
done before the current MDNR requirements for exploration data submission were
in place. There is a possibility that there is much more iron-formation or massive-
oxide (ilmenite) related exploration data for this area, but it has not been found.
62
MISCELLANEOUS INTRUSION–INTERIOR DULUTH COMPLEX
Greenwood Lake Intrusion (GLI)
This Duluth Complex drilling was done by the Minnesota Geological Survey to define
geology in an area of very poor exposure. These drill holes are “touchdown holes”
where the core drilling generally only penetrates about 10 feet of the ledge.
These holes were drilled along the LTV railroad grade to the west of Lake County
Highway 2, north of Two Harbors.
The data source for these holes is Miller (in prep.), where there is a more complete
description and some whole rock analyses.
Osier Lake Intrusion
The Osier Lake intrusion (defined by magnetic signature) has two drill holes, one by
the MDNR (NR-1-MDNR), and one by the MGS (CDC-14B). Miller et al. (2002),
suggests that this may a feeder zone for a now eroded intrusion that was higher up in
the Complex. The area is near Isabella in central Lake County.
BEAVER BAY COMPLEX AND NORTH SHORE VOLCANIC GROUP
Milepost 7
The Milepost 7 drill holes, at the NorthShore Mining (Reserve Mining Company)
tailings basin near Silver Bay, were located by Miller et al. (2002) for the 2002 Duluth
Complex compilation project. A comprehensive listing of the total depths for these
ninety five drill holes, as well as any detailed logging, are not available. The drill holes
were given an artificial and arbitrary depth to ledge of 50 ft. and a total depth of 100
ft. The collar elevation was arbitrarily set to 1,200 feet above sea level. These drill
holes are listed here to maintain consistency with the data in Miller et al. (2002).
There is probably not any core available for these drill holes, and the area (private
property) is now under tailings from the iron ore concentrating plant at Silver Bay.
Dr. John C. Green of the University of Minnesota Duluth produced a report for the
Minnesota Geological Survey in 1982 titled: “Geology of the Milepost 7 Area, Lake
County, Minnesota.” This report, and the modifications made to the regional geology
in Miller et al. (2002) would give the best picture of the geology of that area. NRRI
has draft copies of some of Green’s cross-sections used in his report, but they do not
appear to be a complete set. The drill holes pass through glacial till and lake clays,
and penetrate units of the North Shore Volcanic Group (NSVG) and undivided
hypabyssal rocks of the Beaver Bay Complex (BBC). Some whole rock assays are
reported in Green (1982), but no metals assays are known to exist.
63
Green’s report references at least five reports written on drilling in the area during the
preparation of the Environmental Impact Statement (EIS) for the Reserve Mining
tailings pond project. These reports are by Klohn Leonoff Consultants (now Klohn
Crippen?). Further information on this drilling could possibly be obtained from Cliffs
NorthShore Mining of Silver Bay (successor company to Reserve Mining), the
Minnesota Pollution Control Agency (if such EIS background records are kept), or
Klohn Crippen, if they still have these data, and are allowed to release it.
Sonju Lake Intrusion (SLI)
The Sonju Lake intrusion of the Beaver Bay Complex (in the Finland area) has been
drilled by the MGS (two holes) for scientific purposes (to discriminate a potential
PGE-bearing horizon related to closed magma chamber crystallization processes) and
by Lehmann Exploration (six holes) to further test this theory. The MDNR also
drilled one hole in this area. The PGE-enriched horizon is found in drilling where
predicted by outcrop mineral chemistry. The drilling and assay data are not sufficient
to define a specific deposit area yet.
Miller (1999) discusses the logic of this exploration approach. Currently (2003),
Greg Joslin of the University of Minnesota Duluth Geology Department is working
on a masters thesis on these drill holes.
Cloquet Lake Layered Series (CLLS)
The Cloquet Lake layered series (CLLS) of the Beaver Bay Complex covers an area
about 15 miles north-south and 10 miles east-west with Lake County Highway 2 on
its west, Lake County Highway 15 (Forest Highway 11) cutting across the middle
third, and Lake County Highway 4/Minnesota Highway 1 on the east. Outcrop is
poor, and the intrusion is mainly defined by a pronounced circular aeromagnetic
signature (Miller et al., 2002). Drilling here includes ten MGS “touchdown holes”
(Meints et al., 1993), three holes with no record (related to the Milepost 7 drilling),
and four holes by Lehmann Exploration Management in the 1980s.
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APPENDIX 2
SURVEY TABLE FORMAT AND EXPANDED DESCRIPTION FOR GEMCOM

DATABASE (GCDBDC.MDB) AND SPREADSHEET FILES (SURVEY.XLS,
SURVEY.CSV)
65
APPENDIX 2: SURVEY TABLE FORMAT AND EXPANDED DESCRIPTION FOR
SURVEY TABLE INTRODUCTION
This table lists the downhole survey data available for each drill hole. In this database we have
included the extensive downhole dip and azimuth surveying at Babbitt / Serpentine in “from-to”
interval format. The majority of the other holes do not have downhole azimuth testing, and use
simpler acid tests. In these cases, we need to make assumptions about which compass direction the
hole deviated towards to use this data. We assume that all holes turned northwest (into the basal
contact). This assumption is in line with those made by most of the exploration companies.
The Babbitt / Serpentine data was taken from Patelke (1994), most of the other drill holes with acid
tests were taken and reformatted (recalculated from “mid-point” of interval to “from-to” for interval)
from Peterson (1997). Those drill holes with no downhole work done (or recorded here) are given
the collar dip and azimuth for the length of the drill hole. Some modeling programs will require that
the survey data be in this separate file, even if there is no change in the data downhole.
Dip is given as a negative value for holes from the surface. Note that some drill holes in the Local
Boy (underground) portion of the Babbitt deposit and a few holes at Maturi underground were drilled
upwards from the drifts, and therefore have a positive dip.
SURVEY DATA
The format for the survey table is:

INTERVAL: interval length along core in feet
DIP: Dip of survey interval, -90/ equals straight down
AZIMUTH: azimuth of survey interval clockwise from true north, for vertical holes the
azimuth equals 0/
SURV-TYPE: Type of survey, see Patelke (1994) for further description of the Babbitt and
Serpentine surveys. In other cases this is a rough estimate of type of survey based on easily
available data.
DSURVFROM[X]: desurveyed easting-interval “from” easting in NAD27 state plane feet
DSURVFROM[Y]: desurveyed northing-interval “from” northing in NAD27 state plane feet
DSURVFROM[Z]: desurveyed elevation-interval “from” elevation in feet above sea level
DSURVTO[X]: desurveyed easting-interval “to” easting in NAD27 state plane feet
DSURVTO[Y]: desurveyed northing-interval “to” northing in NAD27 state plane feet
DSURVTO[Z]: desurveyed elevation-interval “to” elevation in feet above sea level
XLSFILE: The lithology and assay tables needed to be split to stay within the 64,000 record
limit of Microsoft Excel. This shows which file set this drill hole is in, either “EAST” or
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“WEST”, *.XLS and *.CSV. This designation is carried for each data type, even though only
the lithology and assay files were split.
This format accounts for the entire drill hole length, i.e., all intervals, measured or not, are listed in
the file. The sum of the intervals equals the length of the drill hole.
67
APPENDIX 3
LITHO (LITHOLOGY) TABLE FORMAT AND EXPANDED DESCRIPTION FOR

GEMCOM DATABASE (GCDBDC.MDB) AND SPREADSHEET FILES (EAST-
LITH.XLS, WEST-LITH.XLS, EAST-LITH.CSV, AND WEST-LITH.CSV)
68
APPENDIX 3: LITHOLOGY TABLE FORMAT AND EXPANDED DESCRIPTION FOR
LITHO TABLE INTRODUCTION
This is the lithological data for each hole in “from-to” interval format. This information covers the
NRRI logging, filled in on a hole by hole basis with company data for holes either unavailable or not
yet logged by NRRI.
LITHO (LITHOLOGY)
The format is:

INTERVAL: interval length in feet measured along core
ROCKTYPE: logged rocktype by abbreviation
EXP-RTYPE: logged rocktype-full name
CON-RTYPE: example of consolidation of rocktype
UNIT: cross-section (map) unit
NRRI–XSECT: NRRI cross-section showing this drill hole
COMP-XSECT: which original company cross-section this hole would be on, done only for
Babbitt and Dunka Road
FW-FROM: interval “from” going up from drill hole from footwall penetration point, in feet
FW-TO: interval “to” going up from drill hole from footwall penetration point, in feet
GEOLOGIST: geologist responsible for logging, as in header file
DEPOSIT: which deposit, as in header file
limit of Microsoft Excel. This shows which file set this drill hole is in, either “EAST” or
This format accounts for the entire drill hole length, i.e., all intervals, logged or not, are listed in the
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Explanation:
The entries in this table not self-evident after inspection of the other table descriptions are the
following: ROCKTYPE:, EXP-RTYPE:, CON-RTYPE:, UNIT:, FW-MARKER:, FW-FROM:, and
FW-TO:. The expanded descriptions are below, first the four lithology related intervals
(ROCKTYPE:, EXP-RTYPE:, CON-RTYPE:, and UNIT:), followed by the footwall marker and
distance discussion (FW-MARKER:, FW-FROM:, and FW-TO:).
ROCKTYPE-LOGGED ROCKTYPE BY ABBREVIATION CODE
The rock naming and unit designation conventions are where a familiarity with the previous
work on the Complex becomes most important. Miller et al. (2002), the references therein,
and NRRI reports listed in the introduction are the best possible explanations of this
terminology. The rock type explanations here are very cursory at best. Mark Severson
assisted in the outline of rock types and units described here.
The lithology coding for rocktype and unit in these data files is not perfect. Time did not
permit the entering of every detail recorded in the logging. Because the purpose here is to
make these data available for deposit-wide or regional evaluation, we wanted to make
comparisons of rocktype versus assay value a relatively simple process, as well as using our
“map unit” (or “cross-section unit”) as a way of grouping the rocktype intervals together into
presumably related packages. We wanted these rocktype names to be meaningful when
viewing computer generated cross-sections at a reasonable scale on screen, in programs such
as Gemcom, MedSystem, DataMine, etc. There is an overriding assumption here that these
data will be used by someone familiar with one of these or similar programs, and/or be well
versed in sorting and the use of filters in Excel or other spreadsheets. The concept followed
in rock naming was to simplify, on the assumption that too many modifiers of rock names
would make meaningful sorting or display all but impossible.
In the NRRI logging, we have generally used a modification of the Phinney (1972) system
(Fig. 3). Names for mafic rocks are based on the visually estimated modal percentages of
plagioclase, olivine, and augite. We have also added some definitions to our rock naming
convention to accommodate the needs of logging. These are not necessarily the naming
conventions we would use for detailed petrological study or more formal publication. Below
is some explanation of these logging codes. For a rigorous discussion on how Duluth
Complex rock types and units should be formally named see Miller et al. (2002).
The database is predicated on the user using the rocktype designation and cross-section unit
designation in tandem to filter data. In other words, it is possible to sort data by rocktype,
by unit, or by both.
The rocktype name (and modifier) is based on the shortest possible name that describes that
interval. Rather than redescribing every possible rock name code in the database, we have
added a column in the lithology table with the rock code expanded to its full name.
70
Figure 3. Modified Phinney (1972) diagram for rock unit classification on left side. Right side shows how
units were consolidated in the database as an example of simplifying the data.
In the data file we present the rock types for the interval as we recorded them, as well as an
example version of how these rock types can be condensed down to a manageable number
(somewhat less than 2,000). We also placed rocktype names and modifiers in an order with
the name first, followed by the modifier. A white granophyre vein is listed as “vein
granophyre white”, a massive oxide interval is listed as “oxide massive”, and a heterogeneous
augite troctolite is listed as “AGT HET”, which expands to “heterogeneous augite troctolite”.
Hopefully, this will lead to easier sorting for users.
Hyphenated rock names for intervals, such as “AGT-T” (augite troctolite-troctolite) or “MT-
ORT” (melatroctolite-olivine rich troctolite) can be read as either “and” or “to” because the
judgement used here was to make each lithologic interval homogenous, i.e., what would the
mineralogy or chemistry of the interval show if tested as a single sample. The lithology
intervals for logged drill holes average about fifteen feet. Therefore, each one represents a
tiny part of the total.
For each interval we recorded the rocktype as given on the log. Here are two examples of
how this looks:
1) The data file will show an interval, for example, as “AGT” (augite troctolite),
“OG” (olivine gabbro), “H CORD” (cordieritic hornfels), or “VF MASSIVE”
(massive Virginia Formation). These single rocktype intervals are fairly
straightforward. Considering that the Phinney (1972) diagram shows 17 individual
rock types, and considering a variety of hanging wall and footwall rocks, plus
71
combinations of rock types, one might guess there would be between 50 and 100 rock
types in the data file. In reality, there are over 2,000 different abbreviations recorded
after much simplifying.
A problem in this simplifying of rock type is that a hyphenated interval recorded as

“AGT-OG” (augite troctolite-olivine gabbro) carries no record of whether this means:
a) augite troctolite and olivine gabbro in equal amounts;
b) augite troctolite with lesser olivine gabbro, a gradation from one part of the
interval to another;
c) a mineralogy that falls between augite troctolite and olivine gabbro on the
Phinney diagram, let alone how these rock types (and their textures) are mixed
or intermingled over this interval.
2) Another example is the “AT-T” (anorthositic troctolite-troctolite) . This could be:
a) a mineralogical range of AT to T (anorthositic troctolite to troctolite);
b) mixed thin intervals of AT and T (anorthositic troctolite and troctolite);
c) AT grading to T (anorthositic troctolite grading to troctolite).
Various geologists have used various schemes, with logging done for different
purposes. This situation makes trying to offer more definitive definition of a term
such as AT-T difficult. There are at least five references for AT-T in our logging,
these are: (AT)T, AT-T, AT/T, AT & T, and AT-(T). This coding is simpler to
understand on the logs themselves, where they can be read in complete context.
For intervals that span across entire fields (i.e., skip fields) on the modified Phinney triangular
diagram, such as “AT-MT” (anorthositic troctolite-melatroctolite) the usual case is that both
distinct rock types were present in the interval.
For intervals recorded with more than two very distinct rocktypes, we usually tried to
consolidate this to two names. Also, in some cases we used “W/” such as “NOR W/H” for
norite with sedimentary hornfels or “NOR W/H BASALT” for norite with basalt inclusion(s).
In sum, the view taken here is this: in the Duluth Complex (especially in the area where the
majority of the drilling is recorded) the rocks are heterogeneous cumulate rocks as a rule.
The logged lithological intervals in the database average about 15 feet. Any individual
interval represents a very tiny increment of the total drilling. It would be best to read the
interval descriptions in the data file as representing a data point on the Phinney diagram,
which is essentially what their chemical or mineralogical analysis would show. For more
detailed studies, either don’t use the mixed rock types, or refer back to the original logs and
re-code the lithology to meet your needs. In other words, we intend this data to be used en
72
masse where a large number of intervals ought to average out to a limited number of simple
names.
Modifiers
We have tried to limit the number of modifiers to these rock names. The main ones are:
a) “HET” for heterogenous, where there are rapid and inconsistent changes in modal
percentage and/or grain size over very short distances. It is common to see packages
of rock where no one description fits at any given point in an interval, even over very
short intervals;
b) “HOMO” for homogenous, where the rocks are marked by very consistent modal
percentages and/or grain size;
c) “PEG” is used both as a modifier and a rocktype, meaning very coarse-grained.

Generally, but not always, it is assumed to be an irregular, patchy phenomenon, and
it is usually gabbroic;
d) “MOTT” for mottled, which is a characteristic mottling caused by poikiolitic

olivine, especially in Unit 3 of the Partridge River intrusion (Unit III of Severson and
Hauck, 1990), but present elsewhere.
Some less used, but present, modifiers include: graphite or graphitic for graphite-bearing
intervals, ural (uralitized, i.e., pyroxene replaced by amphibole), serp (the olivine is
serpentinized), and fluxion for plagioclase lamination.
Rock Names Not Covered By The Modified Phinney Diagram
Massive Sulfide (MS): where the logging geologist described an interval as massive
sulfide (greater than 75% sulfide) we noted it as such. MS PO means massive sulfide
pyrrhotite, MS CP means massive sulfide chalcopyrite and/or cubanite.
Semi-Massive Sulfide (SMS): where the logging geologist described an interval as

semi-massive sulfide (50-75% sulfide) we noted it as such. SMS PO means semi-
massive sulfide pyrrhotite. SMS CP means semi-massive sulfide chalcopyrite and/or
cubanite.
Granophyre: refers to cross-cutting veins of felsic rock. These rocks are

volumetrically unimportant. These veins are common and while they are most
common in areas around fault systems, their presence alone has not proved to be
diagnostic of proximity to a structure. Contacts are usually sharp. There are also
ubiquitous saussurite patches that superficially appear to be granitic veins, generally
these have gradational contacts with the surrounding rocks and contain some relict
plagioclase.
73
Large amounts of ubiquitous patchy granophyre and felsic material generated by
partial melting and seen in the footwall Virginia Formation are minimally recorded
here. Almost any of the “recrystallized” (RXTAL) or “disrupted” (DISRUPT)
Virginia Formation intervals will contain some evidence of partial melting.
The veining in the SKI may consist of the “usual” Duluth Complex granophyric
veining, as well as a large amount of “backveining” nearer the base of the intrusion.
This “backveining” is remelted Giants Range granite and has not been clearly
discriminated in this database from the Complex differentiates. This is mostly due to
lack of available core. Much of the geology notation for the SKI came directly from
INCO logging and we have no way to correlate much of their detailed work with our
own.
Faults: We have included “fault”, “breccia”, and “fault/breccia” as a rock type in this
database where the logging geologist clearly felt an interval was a fault. This notation
does not include strongly serpentinized zones (generally not noted in this database)
nor zones intruded by granophyric rocks, and therefore represents a minimum starting
point for correlating fault geometry from drill hole to drill hole.
For a number of reasons, faulting is problematic in these deposits:
a) the majority of drill holes are vertical and therefore might miss the expected
half-graben normal faults;
b) the rocks can be non-descript over very long intervals;
c) large scale marker units (like Unit 3 in the PRI) are rare;
d) if there is offset it may be accommodated in the serpentinized ultramafic

zones, but there is not good enough control on the continuity of specific
ultramafic horizon to always use them as markers;
e) this lack of specific markers and the generally wide drill hole spacing helps
prevent developing these correlations;
f) cross-sections drawn with and without faults can both work and be
consistent with the dips seen in bedding of the iron-formation;
g) the lack of surface exposure means that there are few faults mapped at the
surface that can be checked against drill data;
h) and the geophysical response of any of these faults is not distinct enough
to use for mapping at less than 1:24,000 scale (J. Miller, pers. comm. 2003).
The RQD data for Babbitt, which might be expected to define some more broken up
zones of rock, generally shows no quickly evident pattern to the 3-D geometry of
74
more fractured rock. These data may be worthy of some detailed evaluation in this
regard.
Massive Oxide: is listed as “oxide massive”. This is usually ilmenite greater than
magnetite. No other oxides are generally noted in the logs. Note that other oxides
have been seen in thin and polished section, i.e., chromium magnetite, chromium
titanomagnetite, chromite, hercynite, pleonaste, and others.
Semi Massive Oxide: listed as “oxide semi-massive”.
Norite (and noritic rocks and orthopyroxenites): Noritic rocks with plagioclase-
orthopyroxene +/- augite +/- olivine rocks are very common in the Duluth Complex,
especially in areas where there has been digestion of disaggregated footwall rocks.
These norites are probably not of a strictly igneous origin as seen in other layered
intrusions, but rather are related to magmatic contamination through assimilation of
pre-existing footwall rocks.
OUI (Oxide-bearing Ultramafic Intrusion): OUI is a class of cross-cutting oxide-

bearing ultramafic rocks. OUI is used here as both a rocktype for the apparently
discontinuous, but distinct, intervals of these rocktypes seen throughout the Duluth
Complex; and as a unit name for large OUI bodies such as at Water Hen, Section 17,
Section 22, Section 34, Longnose, Longear, and smaller bodies along the southern
margin of the Babbitt Deposit.
Hornfels (H): is meant to encompass all inclusions that are not intrusive rock. These
generally break down into four classes: Biwabik Iron Formation (H BIF),
metamorphosed subunits of the Virginia Formation (H CORD, H DISRUPT, H
RXTAL, etc.), hanging wall basaltic rocks (H BASALT, and some “CC” for Colvin
Creek-type magnetic basalt inclusions), and some inclusions of Archean granitic and
mafic rocks.
Scattered throughout the Duluth Complex are cognate inclusions of intrusive rock,
for instance, anorthosite inclusions in troctolitic intervals. These have not been noted
as inclusions in this database.
Where footwall rocks are detached from the footwall (inclusions moved into the
Complex by dilation or floating), these rock names are preceded with an “H” for
hornfels, such as “H CS” for hornfelsed calc-silicate or “H CORD” for cordieritic
hornfels. Where these footwall rocks are thought to be in place, they are preceded
with the map unit designator, such as “VF CORD” for cordieritic Virginia Formation,
or “VF CS” for a calc-silicate horizon in the Virginia Formation. Therefore, a
hornfelsed cordieritic Virginia Formation inclusion in Unit 1 of the Partridge River
intrusion would be read as: “H CORD” in Unit 1; a Biwabik Iron Formation inclusion
would be shown as “H BIF”; and basalt inclusions as “H BASALT”.
75
Footwall Cordieritic Metasediments: (VF CORD in place or H CORD when they
are present as inclusions). Directly beneath the basal contact of the PRI,
metasediments of the Virginia Formation are generally cordierite-rich and display a
bluish-gray color in drill core. Original bedding planes are preserved in some
instances, but for the most part, the bedding planes have been obliterated by contact
metamorphism.
Disrupted Unit (VF DISRUPT in place or H DISRUPT when present as inclusion) -

well-bedded argillites of the Virginia Formation are commonly transformed into a
highly deformed rock, or a metatexite (Sawyer, 1999), in close proximity to the
Duluth Complex. Textures that characterize this rock are bedding planes that are
extremely chaotic and random in orientation due to pervasive micro-folding, micro-
faulting, and micro-brecciation. Superimposed on this chaotic pattern are abundant
partial melt zones that are also chaotic and micro-folded. The overall texture of the
DISRUPT unit appears to be a result of a combination of partial melting (in response
to emplacement of the Duluth Complex) and intense pervasive structural deformation
(also related to emplacement of the Complex).
Recrystallized Unit (VF RXTAL in place or H RXTAL when present as inclusion) -

the RXTAL Unit is a higher-grade metamorphic equivalent of the DISRUPT Unit.
However, in the RXTAL’s case, the rock was heated enough to generate 20%-30%
pervasive partial melts that enabled the rock to literally flow (pers. com. to Severson,
Ed Sawyer, 1998) in response to stresses applied during emplacement of the Duluth
Complex. All bedding planes are completely obliterated in the RXTAL Unit, and
what remains is a recrystallized rock that contains medium-grained biotite flakes that
are arranged in a decussate manner. Floating within this recrystallized matrix are
blocks/boudins of more structurally competent siltstone and calc-silicate (originally
limey layers).
Graphitic Argillite (usually VF GRAPHITIC in place or H GRAPHITIC when

present as inclusion) - hornfelsed carbonaceous argillite is preserved as graphitic
argillite in close proximity to the Duluth Complex. This rock commonly contains up
to 5% disseminated pyrrhotite. Whenever the pyrrhotite is concentrated in laminae
(generally < 2mm thick), the rock is referred to as the Bedded Pyrrhotite Unit (BDD
PO Unit).
Bedded (VF BDD in place or H BDD when present as inclusion) generally non-
descript, but bedded Virginia Formation or hornfels inclusions.
Virginia Formation undivided - (VF in place or H when present as inclusion) -

generally non-descript, but without bedding noted on log, Virginia Formation or
hornfels inclusions.
MG and V SILL (Virginia Sill) -The bottom-most, but discontinuous, portion of

the Virginia Formation is referred to as the Massive Gray Unit (MG Unit). Originally,
this unit was thought to represent massive-bedded graywackes of the Virginia
76
Formation; however, work at the Babbitt (Mesaba) Cu-Ni deposit (Severson, 1991;
Severson et al., 1996; Hauck et al., 1997; Park et al., 1999) indicated that the MG
Unit is a fine-grained equivalent (chilled?) of a sill with high Cr contents (>800 ppm).
In some cases, the center of this Cr-rich Sill (Hauck et al., 1997) is easily recognized
due to a coarse to medium-grained texture with olivine and/or hornblende (the coarser
portion is listed here as V SILL for Virginia Sill). However, in most cases the
presence of the sill is indicated by much finer-grained material, referred to as the MG
Unit, which is extremely difficult to tell apart from the hornfelsed Virginia Formation.
The age of the Cr-rich Sill/MG Unit is inferred to be early Keweenawan, but a much
older age (1.8 Ga?) is also possible. The intrusion of this sill may be responsible for
some metamorphism in the Virginia Formation, thus forming a thin “armored or
refractory” horizon of previously metamorphosed rock that resisted assimilation
during the intrusion of the Duluth Complex.
Biwabik Iron Formation - Beneath the Virginia Formation and the MG Unit is the
Paleoproterozoic (1.8 Ga) Biwabik Iron Formation (BIF). The BIF is about 400 feet
thick and has been subdivided into 22 submembers (A through V) by Gundersen and
Schwartz (1962). The upper-most four submembers of the BIF are easily recognized
and noted in the NRRI logging as follows:
Submember A - well-bedded white chert and marble; chert and marble are
present in varying proportions.
The BIF Sill unit in the BIF generally occurs at this level.
Submember B - irregularly-bedded white chert and diopside with local thin

marble interbeds, generally non-magnetic.
Submember C - magnetic, thin-bedded, slaty iron-formation with chert,

magnetite, fayalite, and ferrohypersthene.
There also Logan-type(?) sills in the C submember. See Miller et al. (2002).
Submember D - magnetic, thin-bedded to wavy-bedded, cherty iron-

formation.
When reviewing the NRRI cross-sections against the rock naming given by INCO, it
seems that much of what they described in their logging as hornfels or metasediment
is probably inclusions of iron-formation. Where Severson has interpreted INCO logs
in relation to surrounding holes logged by NRRI, we see the U3 unit often
overlapping with INCO’s “hornfels” units. See the Maturi Stratigraphic Line in
Severson (1994) for examples.
Also note that much of the unit definition of the sills below the Complex is based on
post-logging interpretation during cross-section development. Any study of these sills
77
needs to look beyond the limited data included here. The data here locate the sills,
but as with many other items, the sills should be a study in themselves.
Mixed Duluth Complex (MX***) - For drill holes either not logged by NRRI or
with no clear (and reliable) company records, we have used the rock type “MXDC”
for “mixed Duluth Complex”, usually as MXPRI for Mixed Partridge River intrusion,
MXSKI for mixed South Kawishiwi intrusion, MXBLI for mixed Boulder Lake
intrusion, etc. We used this for both rock names and unit types.
In many cases the rocktype MX*** will be shown as being within an assigned cross-
section unit. This unit definition is usually derived from surrounding drill holes.
Logging Differences
The question may arise that because of differences in logging by individual geologists over
time, and the many geologists who have contributed to this work: are these different drill logs
the same population? Yes, while definitions may vary between NRRI geologists, the dataset
is as internally consistent as could be expected for work done over fifteen years.
Our comparisons of logs done by different NRRI geologists on the same holes, which include
both scattered holes and 15,000 ft. to 30,000 ft. re-logging programs by different geologists
at Dunka Road (NorthMet) and Babbitt (Mesaba) show a fair level of consistency. Rock
names may be shifted by one classification on the Phinney (1972) chart (see Figure 3), but
there is little wholesale disagreement between the NRRI geologists on rock naming.
We do observe that in the past many company geologists have probably overused the term
“gabbro” in the Complex in their logging. These are rocks that the NRRI (and probably
MDNR and MGS) geologists would have called troctolite, augite troctolite, olivine gabbro,
gabbro, anorthositic troctolite, anorthositic gabbro, and olivine-rich troctolite. This naming
is not due to ignorance on their part, but that their concern was with mineralization, and they
often labeled all intrusive rock (particularly non-mineralized intervals) that was not clearly
anorthositic nor ultramafic as “gabbro”. It is quite possible that in terms of studying the
mineralized rocks (and the distribution of mineralization) this level of lithological definition
may be all that is needed.
EXP-RTYPE-logged rocktype-full name
This is simply the rock naming described above expanded to its full name, with some change in
modifier order. Inspection of this field in the database should be self-explanatory.
CON-RTYPE-EXAMPLE OF CONSOLIDATION OF ROCKTYPE
This column is an example of how one can consolidate the rocktypes to a smaller dataset, in this case
for example, mostly by merging adjoining fields on the Phinney diagram and removing the specific
78
unit for rocks of the Virginia Formation and Biwabik Iron Formation. Inspection of the database will
make it clear which rocktypes have been reduced to which name in this list. See Figure 3 for
examples of how this naming scheme correlates with the original Phinney (1972) plot.
The Duluth Complex rocktypes have been reduced to:
Anorthositic
Troctolitic
Gabbroic
Noritic
Ultramafics
OUI
Vein
Fault/Breccia
Massive Graphite
Massive Chlorite
Massive Serpentine
Massive Oxide
Massive Sulfide
Hybrid
Pegs-Misc
The other (non-Duluth Complex) rocktypes are reduced to:
OVB
Dike
Sill
Basaltic Hornfels
Sedimentary Hornfels
Virginia Formation
Biwabik Iron Formation
Archean
Other (all other intervals)
UNIT-CROSS-SECTION (MAP) UNIT
This is the cross-section unit taken from the NRRI logging. For the most part the logging done by
NRRI has been plotted on cross-sections and correlated with the geology in nearby drill holes. The
unit data presented here is from those cross-sections or notations on the logs. Where the hole was
not plotted on a cross-section, we either filled in the unit data from surrounding holes in areas where
we have some confidence in the continuity of the geology, or used the MX*** notation to
discriminate the unit as a part of a larger intrusion. This MX*** naming convention is very prevalent
in the South Kawishiwi intrusion (MXSKI) where we have little confidence in the continuity of
geologic description in areas where there is logging data for rocktype (mostly from INCO), but no
core available to log.
79
The rock types and map units are presented as is if they were read off a moderately detailed cross-
section, on the order of one inch equals fifty feet to one inch equals two hundred feet. This scale
implies that to make the best sense of these data one should refer to the cross-sections from various
reports that are listed for each hole, or look at nearby sections when a drill hole is not on a published
cross-section.
The level of confidence in this unit assignment is directly related to the density of drilling in a
particular area, and the amount of study we have made of that area. At Babbitt (Mesaba), Dunka
Road (NorthMet), and the other Partridge River intrusion deposits, the igneous stratigraphy is fairly
well-defined, and we are confident about the map units. In the South Complex area (between Duluth
and Wyman Creek) the drilling density is less, and the confidence level is less. In the South Complex
area, we generally find clusters of drill holes defining a local stratigraphy within an overlying (and not
necessarily clear) framework.
In the South Kawishiwi intrusion (Serpentine, Dunka Pit, Birch Lake, Maturi, Spruce Road, South
Filson Creek, and the Highway One Corridor) we again find clusters of drill holes each defining a
local stratigraphy mixed within an overlying continuity from one deposit to the next, but not
necessarily carrying across the entire intrusion.
The NRRI geologists recognize that the igneous stratigraphy is both “imposed” and natural, and is
subject to changing interpretations. This report is not the venue to reconcile all possible solutions
for the “stratigraphy” within these areas.
The only unit designations unique to this database, i.e., not found on published cross-sections, are
some subdivisions of Unit 1 of the Partridge River intrusion. These are based only on the examination
of the logs, and have not been field checked in any sense. These include: 1S1 (“Sub 1"), and 1NZ
(“norite zone”) which is the basal portion of Unit 1 that shows possible strong contamination from
the underlying footwall rocks, i.e., norite, olivine gabbro, and/or a high percentage of hornfels
inclusions. 1NZ is used at Dunka Road, and 1S1 is used at Babbitt and in the rest of the PRI drill
holes. This zone does not extend upwards to the uppermost hornfels occurrence, but is limited to a
continuous zone or rind of contaminated rocks of varying thickness adjacent to the basal contact.
The 1S1 or 1NZ subdivision is not found in every drill hole. The other new subdivisions interpreted
from the logs are 1UM1 and 1UM2, quasi-continuous(?) zones containing ultramafic horizons in Unit
1 at Babbitt. These ultramafic zones have not been field checked, but may correlate with ultramafic
zones in Unit 1 mapped by Geerts (1991, 1994) at Dunka Road (NorthMet).
Footwall rocks units:

The various footwall rocks to the Complex include Virginia Formation (VF) deep water
sedimentary rocks, Biwabik Iron Formation (BIF) banded iron-formation, Pokegama
Quartzite (PQ) near shore sandstones, and the Giants Range batholith Archean rocks (GRB)
which are mostly diorite/monzodiorite, quartz monzonite, and which often have inclusions of
schistose rocks and Knife Lake Group metasedimentary rocks. There are some Keweenawan
basalts that are (or appear to be) in contact with Virginia Formation or near to cordieritic
metasedimentary rocks. Regionally, the Keweenawan basalts are hanging wall to the Duluth
Complex, but locally they can also be classed as footwall units.
80
Hanging wall rocks:
These are Keweenawan basalts. Except for the basalts on top of anorthositic rocks seen in
drill holes of the Highway One Corridor, these are mostly blocks detached from the roof, i.e.,
nowhere else besides Highway One is the roof of the intrusion seen intact in drill hole. These
contact metamorphosed basalts include two broad classes of rock:
1) magnetic basalts with the assemblage plagioclase-augite-magnetite-ilmenite,

generally with a gabbroic to gabbroic anorthosite mineralogy (Colvin Creek type
rocks; Patelke, 1996);
2) non-magnetic basalts with the assemblage plagioclase-orthopyroxene with only

minor oxides, generally a noritic mineralogy (Moose Mountain hornfels, Severson and
Hauck, 1990). Both types may contain some olivine. (Patelke, 1996).
These rocks are usually classed as either H BASALT, or in the special case of
inclusions of strongly magnetic, augite-bearing, metavolcanics similar to the Colvin
Creek Body (Patelke, 1996) classed as “CC”.
The Virginia Formation, the Biwabik Iron Formation, and the Giants Range batholith descriptions
in these data files are somewhat generalized. The footages given are as shown on the logs, but much
of the comment about bedding, foliation, partial melt horizons, mineralogy, etc. has been lost in the
simplifying. Some sill horizons may also be absent from these data files. These units under the
Complex are a study in themselves, and have usually been secondary to our purposes when logging
these drill holes.
DISTANCE TO FOOTWALL MEASUREMENTS

FW-FROM: lithology interval “from” going up drill hole from footwall penetration point, in feet
FW-TO: lithology interval “to” going up drill hole from footwall penetration point, in feet
“From” and “to” relative to footwall, are the interval “from” and “to” distances upward (positive
values) and downward (negative values) from the footwall intercept for drill holes that actually
intercepted the basal contact (also estimated in a few rare cases), whether into Virginia Formation,
Biwabik Iron Formation, or Giants Range batholith granitic rocks; these columns record the interval
distance above (positive values) or below (negative values) from the contact. Using cross-table
transfer in Gemcom one could then assign distance along the hole to the assays or other data for
analysis, i.e., average distance for massive oxide horizons from basal contact, or build composite
tables relative to footwall intercept point.
81
APPENDIX 4
ASSAY (COPPER-NICKEL ASSAYS) TABLE FORMAT AND EXPANDED

DESCRIPTION FOR GEMCOM DATABASE (GCDBDC.MDB) AND SPREADSHEET
FILES (EAST-CUNI.XLS, WEST-CUNI.XLS, EAST-CUNI.CSV, AND WEST-
CUNI.CSV)
82
APPENDIX 4: ASSAY TABLE FORMAT AND EXPANDED DESCRIPTION FOR
ASSAYS INTRODUCTION
Essentially, all of the original assay work in the Duluth Complex is on copper-nickel sulfides. In a
few cases, the emphasis was on massive oxides in the Oxide-bearing Ultramafic Intrusions (Longear,
Longnose, etc.) and the assays for those oxides and other elements are not included here. Also,
United States Steel almost always assayed for iron (also not included here except for Dunka Road),
and INCO and others often assayed for cobalt (not included here). Not all companies assayed for
sulfur.
The values listed in these tables and spreadsheets are generally the assays done at the time of original
drilling and sampling, and usually represent the greatest number of samples done for a particular drill
hole. The format here covers the entire hole top to bottom, with a “NS” marker for intervals not
sampled in the original work. Not all elements were equally sampled for each interval or equally by
each company.
While this data file contains a huge majority of the copper-nickel-sulfur assays available for the
Duluth Complex, it does not contain every known assay. This table was mostly compiled from pre-
existing digital data (Geerts et al., 1990; Patelke 1994; Zanko et al., 1994; and Peterson 1997) with
minimal new data entry. Drill hole lengths were checked and the intervals that were not sampled were
inserted into the data file with a “NS” value. All overlapping and duplicate assays were removed.
Some of the duplicate data is in archive at NRRI in files not included in this report. The data as
reported here are sufficient for regional work, but should absolutely be revisited for property specific
projects.
COPPER-NICKEL ASSAY DATA
The format is:

INTERVAL: interval length in feet along the core
COPPER: copper in percent
NICKEL: nickel in percent
SULFUR: sulfur in percent
CU+NI: copper plus nickel in percent
CU/NI: copper/nickel ratio
CU/S: copper/sulfur ratio
DEPOSIT: which deposit
83
limit of Microsoft Excel, this shows which file set this drill hole is in, either “EAST” or
DATASOURCE: These data were mostly taken and reformatted from Geerts et al. (1990),
Patelke (1994), and Peterson (1997). Minimal data were entered to fill in this table. The
reformatting involved checking all drill hole lengths to match the total depth recorded in the
header file, and intervals with no samples were filled in with “NS”. Duplicate samples and
overlapping samples (usually from different sources) were removed and mostly set aside in
digital format. There are about 1,500 such intervals from a variety of sources. Previous data
entry work was not checked for completeness nor correctness. Peterson’s (1997) data as
received were formatted to the third decimal place; the other data were not. All values were
reset to two decimal places. The data Peterson used for the INCO drill holes mostly came
directly from INCO. NRRI (and MDNR) have the paper data for this assay work on file.
Because the overall purpose of this project was to digitize the lithological logging, not the assay
work, these data represents a minimum of the assay data available. However, it is believed that this
constitutes the great majority of the available assay data. As with many other items, contact the
NRRI geologists if getting every last assay record for an area becomes critical.
This format accounts for the entire drill hole length, i.e., all intervals, sampled or not, are listed in the
84
APPENDIX 5
RQD (ROCK QUALITY DESIGNATOR) TABLE FORMAT AND EXPANDED

DESCRIPTION FOR GEMCOM DATABASE (GCDBDC.MDB) AND SPREADSHEET
FILES (RQD.XLS AND RQD.CSV)
85
APPENDIX 5: RQD TABLE FORMAT AND EXPANDED DESCRIPTION FOR GEMCOM
DATABASE AND SPREADSHEET FILES
RQD INTRODUCTION
This is the RQD (Rock Quality Designation) data calculated by AMAX for the Babbitt and Serpentine
deposits. There are no known public data on these rock properties available for any other exploration
areas in the Duluth Complex. It is unknown if this work has been done elsewhere.
The calculation of RQD values for the Babbitt and Serpentine deposits is explained in an AMAX
inter-office memo dated February 4th, 1976, on file at NRRI and MDNR. In short, RQD is a recovery
percentage and rock strength value calculated from length and number of core pieces, number of
natural fractures, and amount of core actually recovered over the measured interval (Patelke, 1994).
Contact NRRI or the MDNR for information about the AMAX memo detailing the calculation of the
RQD values.
The format is:

INTERVAL: interval length along core, in feet
RQD: RQD value as calculated by AMAX. Higher number equals more natural fractures.
86
APPENDIX 6
PGE, WHOLE ROCK, AND TRACE ELEMENT DATA FOR DULUTH COMPLEX
DRILL CORE SAMPLES (TAKEN FROM SEVERSON AND HAUCK, 2003)
TABLE FORMAT AND EXPANDED DESCRIPTION FOR GEMCOM DATABASE
(GCDBDC.MDB) AND SPREADSHEET FILES (PGE-ETC.XLS AND PGE-ETC.CSV)
87
APPENDIX 6: PGE, WHOLE ROCK, AND TRACE ELEMENT DATA FOR DULUTH
COMPLEX DRILL CORE SAMPLES (TAKEN FROM SEVERSON AND HAUCK, 2003)
TABLE FORMAT AND EXPANDED DESCRIPTION FOR GEMCOM DATABASE AND
SPREADSHEET FILES
PGE DATA INTRODUCTION
These data are taken from the Severson and Hauck (2003) report and compilation of PGE and other
data for the Duluth Complex. This text is a repeat of the text from the earlier section in this report.
Assays PGE and Others Table-Short description

In general, except for in the Birch Lake area, all publically available PGE and precious metal assaying
done in the Duluth Complex was done after the original Cu-Ni sampling. Sometimes this was on the
same pulps, sometimes on composites, and sometimes on fresh core. Morton and Hauck (1987)
summarized the assaying up to that point in time and added some new analyses. The data in this table
is taken from Severson and Hauck (2003) and represents all publically available data on file at MDNR
and NRRI. It is important to stress that there may be other proprietary data for Dunka
Road/NorthMet (PolyMet), Babbitt/Serpentine (Teck Cominco), Birch Lake (Lehmann), and Maturi
(Wallbridge and INCO) areas, as well as other locations.
Besides PGE data, this table includes some major, minor, and trace element analytical data.
Reference should be made to Severson and Hauck (2003) for information on the quality and source
of individual samples.
The format here does not account for the entire length of the drill hole, only including intervals that
were sampled. About 1,000 duplicate and overlapping intervals have been removed from this dataset.
The dataset in Severson and Hauck (2003) is far more complete.

INT-AS-TXT: “from-to” for interval as single text entry
LENGTH: length along core of sample interval
INTRUSION: which intrusion drill hole is in
UNIT: rock unit, from Severson and Hauck (2003)
ROCKTYPE: rock type, from Severson and Hauck (2003)
DEPOSIT: deposit drill hole is in
AU-PPB: gold in parts per billion-as recorded in original data
PT-PPB: platinum in parts per billion-as recorded in original data
PD-PPB: palladium in parts per billion-as recorded in original data
CU-PPM: copper in parts per million-as recorded in original data
NI-PPM: nickel in parts per million-as recorded in original data
S%: sulfur in percent-as recorded in original data
CO-PPM: cobalt in parts per million-as recorded in original data
ZN-PPM: zinc in parts per million-as recorded in original data
88
AG-PPM: silver in parts per million-as recorded in original data
AU-PPM: gold in parts per million-as recorded in original data
AS-PPM: arsenic in parts per million-as recorded in original data
CR-PPM: chromium in parts per million metal-as recorded in original data
TIO2%: titanium as percent oxide as reported in original data
TI%: titanium as percent, metal as reported in original data
MGO%: magnesium as percent oxide as reported in original data
MG%: magnesium percent metal as reported in original data
CR2O3%: chromium as percent metal as reported in original data
CL-PPM: chlorine in parts per million-as recorded in original data
MO-PPM: molybdenum in parts per million-as recorded in original data
V-PPM: vanadium in parts per million-as recorded in original data
CU/PD: copper:palladium ratio
CU%: copper percent, calculated from ppm data
NI%: nickel percent, calculated from ppm data
REFERENCE: data source, see Severson (in prep) for details on sample selection
XLSFILE: The lithology and assay tables needed to be split to stay within the 64,000 limit
of Microsoft Excel, this shows which file set this drill hole is in, either “EAST” or “WEST”,
*.XLS and *.CSV files. This file is not split.
89
APPENDIX 7
DULUTH COMPLEX DRILL HOLE NUMBERING GENERALITIES
90
APPENDIX 7: DULUTH COMPLEX DRILL HOLE NUMBERING GENERALITIES
INTRODUCTION
Of the approximately 2,145 drill holes in this database (the number varies depending on how one
treats drifts, wedges, and other “odd” holes):
1,014 are in the Partridge River intrusion.
780 are in the South Kawishiwi intrusion.
71 are along the west edge of the Complex from Duluth to the Iron Range.
27 are in the Greenwood Lake intrusion and are mostly “touchdown” holes.
About 95 holes associated with the NorthShore Mining tailings basin are in the NSVG or
BBC and have no reliable logging records.
About 65 are in the various intrusions along the Gunflint Corridor.
The other 200 or so drill holes are scattered through the Central Duluth Complex, or are in
Anorthositic Series rocks, the Bald Eagle intrusion, the Osier Lake intrusion, felsic rocks,
diabase, Virginia Formation, or are unclassified. Over 90% of the “legitimate” exploration
drilling (logged core holes with some metals assaying) is within two and one-half ground
miles (4 km.) of the basal contact of the Duluth Complex. Grid spacing in the deposit areas
is generally wide (>800 ft.) with large sparsely drilled (unexplored) areas available between
deposit areas and in the interior of the Complex.
Drill Hole Numbering
This listing gives the generalized assignment of drill hole numbering by companies and agencies that
have done drilling in the Duluth Complex. This listing is not complete. There are numerous other
small groups of drill holes, but these are the main groups. Note that there is no hole numbering
duplication in the Duluth Complex, but that some of these numbers may be duplicated elsewhere in
Minnesota. See the database itself for better definition of these localities. We include our guess on
what the acronyms represent for a few areas.
1) Holes and grids designated with a Roman Numeral are usually Phelps Dodge drill holes
in the South Complex (Iron Range to Duluth) area. There are a number of these grids. Many
of these have also been given area names in various NRRI reports. These are generally in the
Boulder Lake intrusion (BLI),Western Margin intrusion (WMI), and Partridge River intrusion
(PRI).
91
Grid I is also labeled as Boulder Creek in the WMI.
Grid II is also labeled as Skibo South in the PRI.
Grid IV is also labeled as Boulder Lake North in the BLI.
Grid V is also labeled as Boulder Lake South in the BLI.
Grids VI and VII are also labeled as Boulder Lake Central in the BLI.
Grid VIII in the BLI has not been renamed.
Grid X in the Duluth Complex Anorthositic Series is also labeled as Thomson Lake.
2) CV (Cloquet Valley?) drill holes are in the South Complex (Iron Range to Duluth) area
in the WMI.
3) LE series are at Longear in the PRI.
4) LN series are at Longnose in the PRI.
5) SL (St. Louis?) series and CN (Copper-Nickel? or Cloquet North?) series holes are at the
Water Hen area in the Partridge River intrusion (PRI).
6) A series (A-3, A-4) are Allen grid(s) drill holes drilled by Bear Creek in the PRI.
7) W series holes are at Wetlegs and Wyman Creek holes by Exxon in the PRI
8) 26000 series holes are, in the majority, USS holes at Dunka Road, but include drill holes
in the South Complex (Iron Range to Duluth) area. Mostly in the PRI.
9) 99-XXX and 00-XXX followed by a B or C are PolyMet holes at Dunka Road

(NorthMet) in the PRI.
10) 10000 to 10219 series are drill holes underground at the Local Boy part of the Babbitt
Deposit.
11) B1- series holes are mostly Babbitt and Serpentine by Bear Creek and AMAX, in the PRI
and the western edge of the South Kawishiwi intrusion (SKI).
12) B2- series are Dunka Pit holes by Bear Creek in the SKI.
13) BL and C series are Birch Lake hole in the SKI (except for BL-1-MDNR near Bear
Lake).
14) E (also NM) series holes are Erie mining holes at Dunka Pit, renumbered by USBM, in
the SKI.
15) DU are Duval holes, mostly in the Dunka Pit and Birch Lake area of the SKI.
16) 8000 series are mostly Erie Mining (LTV) drilling at Dunka Pit in the SKI.
92
17) NM series holes 1 through 6 are Newmont holes, mostly in the Highway 1 Corridor in
the SKI.
18) NM series holes 12 through 63 are Newmont holes at Dunka Pit in the SKI.
19) 11500 series are INCO drill holes, mostly in the South Kawishiwi intrusion (Maturi and
Spruce Road) with a few in the Partridge River intrusion.
20) 13600 series are INCO holes mostly in the Partridge River intrusion with a few in the
South Kawishiwi intrusion.
21) 32700 series are INCO drill holes in the South Kawishiwi intrusion (Maturi and Spruce
Road).
22) 34800 are INCO holes, mostly at Spruce Road in the SKI.
23) AD (AD = Adams?, land originally owned or controlled by Robert Adams) series are
Bear Creek holes just west of Spruce Road in the SKI.
24) 40900 series are INCO drill holes mostly at Spruce Road, but also scattered throughout
the South Kawishiwi intrusion and the Partridge River intrusion.
25) KA- and KAF are Bear Creek holes at Little Lake Road (KA=Kangas Bay Quad?) in the
SKI.
26) K series are mostly South Filson Creek drilling by Hanna Mining. Those not at South
Filson Creek are all in the South Kawishiwi intrusion.
27) CDC drill holes are MGS drill holes in the Central Duluth Complex.
28) GLI drill holes are MGS holes in the Greenwood Lake Intrusion.
29) SL0- and SNA series are holes in the Sonju Lake area.
30) STP series are holes north of the NorthShore Mining tailings basin in the Cloquet Lake
layered series.
31) 1000 series are drill holes at the Reserve Mining Company (NorthShore Mining) tailings
basin north of Silver Bay, in the NSVG and BBC.
32) BW series drill holes are the “Blankenberg-Whiteside” holes in the Gunflint Corridor.
33) G and GF series holes are in the Gunflint Corridor.
34) LI and LL (Long Lake?) are holes in the Gunflint Corridor.
35) ON (Oglebay Norton) are holes in the Gunflint Corridor.
93
APPENDIX 8
USEFUL CONTACT INFORMATION FOR DULUTH COMPLEX MINING AND

EXPLORATION ISSUES
94
APPENDIX 8: USEFUL CONTACT INFORMATION FOR DULUTH COMPLEX MINING
AND EXPLORATION ISSUES
CONTACTS
For general data issues, and geologic questions:

At NRRI:
Steve Hauck, Mark Severson, Larry Zanko, Richard Patelke, and Dean Peterson at:
Natural Resources Research Institute

University of Minnesota Duluth
Duluth MN 55811-1442
218-720-4294
At MDNR:
Marty Vadis, Dave Dahl, Rick Ruhananen, Al Dzuck at:
Minnesota Department of Natural Resources

Lands and Mineral Division
1525 Third Ave. East
Hibbing MN 55746-1461
218-262-6767
For initial mineral leasing information questions:

State lands:
Kathy Lewis
Lands and Mineral Division
500 Lafayette Road
St. Paul MN 55155
651-296-4807
For Federal lands:

Stu Behling-Geologist (ex-Bear Creek geologist)
United States Forest Service
Commonwealth Avenue
Duluth MN 55808
218-626-4300
For general tax questions related to Minnesota mining:

Tom Schmucker
Minnesota Department of Revenue
Eveleth MN 55734
218-744-7420
95
For information about economic development issues in northern Minnesota:
Brian Hiti
Iron Range Resources and Rehabilitation Agency
PO Box 441
1006 Highway 53 South
Eveleth MN 55734-0441
218-744-7400
John Chell-Director
Arrowhead Regional Development Commission
221 West First Street
Duluth MN 55802
218-722-5545
For regional geology:

Dr. James D. Miller Jr.
Minnesota Geological Survey
c/o Natural Resources Research Institute
Duluth MN 55802
218-720-4294
and:
Minnesota Geological Survey

2642 University Avenue
St. Paul MN
651-627-4780
Trade groups related to exploration and mining in Minnesota:
Minnesota Exploration Association (MExA)

Suite 622, Plymouth Building
12 South 6th Street
Minneapolis MN 55402-1506
612-338-5584
Frank Ongaro
Iron Mining Association of Minnesota
505 Lonsdale Building
302 West Superior Street
Duluth MN 55802
218-722-7724
96
For exploration and mining permitting and environmental review information:
Ann Foss
Minnesota Pollution Control Agency (MPCA)
520 Lafayette Road
St. Paul MN 55155-4194
651-296-7512
Rebecca Wooden
500 Lafayette Road
St. Paul MN 55155
Drilling regulation
Also note that Minnesota Department of Health governs drilling operations on areas outside of
permitted mine properties (test pits are governed by MDNR and MPCA if large enough):

Well Management Unit
P.O. Box 64975
St. Paul MN 55164-0975
1-651-215-0812
97

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EXPLORATION DRILL HOLE LITHOLOGY,

GEOLOGIC UNIT, COPPER-NICKEL ASSAY,

with assistance from Mark J. Severson,

Funded by the Permanent University Trust Fund

Project No. 783-1048, 5601214

Natural Resources Research Institute

LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

INTRODUCTION AND BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

DATA FORMATS, DATA TABLE LISTING, AND SHORT EXPLANATIONS . . . . . . . . . 10

APPENDICES 1 THROUGH 8 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

APPENDIX 1: HEADER TABLE FORMAT AND EXPANDED DESCRIPTION FOR

APPENDIX 2: SURVEY TABLE FORMAT AND EXPANDED DESCRIPTION FOR

APPENDIX 3: LITHO (LITHOLOGY) TABLE FORMAT AND EXPANDED

APPENDIX 4: ASSAY (COPPER-NICKEL ASSAYS) TABLE FORMAT AND EXPANDED

APPENDIX 5: RQD (ROCK QUALITY DESIGNATOR) TABLE FORMAT AND

APPENDIX 7: DULUTH COMPLEX DRILL HOLE NUMBERING GENERALITIES . . . . 90

APPENDIX 8: USEFUL CONTACT INFORMATION FOR DULUTH COMPLEX MINING

Table 1. Listing of deposit areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 1. Schematic of data layout and table relationships in Gemcom database . . . . . . . . . . . 10

CD-ROM WITH DATABASE, PDF FILE OF THIS REPORT

This report can be considered to be a continuation of a portion of Minnesota Geological Survey

Assumptions and Goals

The final purpose is then to compile a database that:

1) can be used in mine modeling or GIS software with little or no modification;

2) can be used in spreadsheet format for certain analyses;

4) makes these data easily available to as many interested parties as possible;

9) reasonably cross-references with the data in Miller et al. (2002);

Minnesota Geological Survey Report of Investigations 58 (RI-58) by Miller,

Reports on the general igneous stratigraphy of the Partridge River intrusion by

Babbitt (MinnAMAX or Mesaba) area reports by Severson et al. (1994, 1996);

9) digitize the property ownership;

Figure 1. Schematic of data layout and table relationships in Gemcom database.

Data File Sizing, Splitting, and Naming

Duluth Complex Felsic Undivided Brule Lake intrusion

Diabase Undivided Cloquet Lake Layered Series of Beaver Bay Complex

Duluth Complex Anorthositic Undivided Logan Sill

Partridge River intrusion (PRI) North Shore Volcanic Group (NSVG)

Virginia Formation at Margin of Partridge River intrusion Osier Lake

Virginia Formation-Biwabik Iron Formation (VF-BIF) Poplar Lake intrusion

Western Margin intrusion (WMI) South Kawishiwi intrusion (SKI)

Unknown and Unnamed

Virginia Formation-Biwabik Iron Formation (VF-BIF) at

Drill Hole Numbering

Drill Hole Coordinate and Location Comments

1) downhole units are in feet;

DATA TABLES-SHORT DESCRIPTIONS

Common Elements in All Data Tables

FROM: start of interval relative to collar in feet

TO: end of interval relative to collar in feet

INTERVAL: interval length in feet along core

Column Order in Data Tables

HEADER Table-Short Description

Table 4. Format of Survey Table-see Appendix 2 for expanded explanation.

FROM: start of interval relative to collar in feet

TO: end of interval relative to collar in feet

INTERVAL: interval length in feet

DIP: Dip of interval, -90/ equals straight down

Table 5. Format of Lithology Data Table-see Appendix 3 for expanded explanation.