Nothing Special   »   [go: up one dir, main page]
Scribd Logo
Upload

Welcome to Scribd!

  • 98 views

    Carbonate Petrography

    Uploaded by

    Mazigh Nmax
    This document provides an overview of carbonate petrography and the identification of carbonate minerals. It discusses the three main carbonate mineral groups: calcite, dolomite, and aragonite. Calcite and dolomite are the most volumetrically important carbonate minerals. The document outlines techniques for distinguishing calcite, aragonite, and dolomite using staining methods with alizarin red S and potassium ferricyanide solutions. These staining methods can identify the minerals by the colors they take on under microscope.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    Carbonate Petrography

    Uploaded by

    Mazigh Nmax
    98 views31 pages
    This document provides an overview of carbonate petrography and the identification of carbonate minerals. It discusses the three main carbonate mineral groups: calcite, dolomite, and aragonite. Calcite and dolomite are the most volumetrically important carbonate minerals. The document outlines techniques for distinguishing calcite, aragonite, and dolomite using staining methods with alizarin red S and potassium ferricyanide solutions. These staining methods can identify the minerals by the colors they take on under microscope.

    Original Description:

    petrography book

    Copyright

    © © All Rights Reserved

    Available Formats

    PDF, TXT or read online from Scribd

    Did you find this document useful?

    Is this content inappropriate?

    This document provides an overview of carbonate petrography and the identification of carbonate minerals. It discusses the three main carbonate mineral groups: calcite, dolomite, and aragonite. Calcite and dolomite are the most volumetrically important carbonate minerals. The document outlines techniques for distinguishing calcite, aragonite, and dolomite using staining methods with alizarin red S and potassium ferricyanide solutions. These staining methods can identify the minerals by the colors they take on under microscope.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    98 views31 pages

    Carbonate Petrography

    Uploaded by

    Mazigh Nmax
    This document provides an overview of carbonate petrography and the identification of carbonate minerals. It discusses the three main carbonate mineral groups: calcite, dolomite, and aragonite. Calcite and dolomite are the most volumetrically important carbonate minerals. The document outlines techniques for distinguishing calcite, aragonite, and dolomite using staining methods with alizarin red S and potassium ferricyanide solutions. These staining methods can identify the minerals by the colors they take on under microscope.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 31

    Carbonate Petrography

    GEO 431
    Lab (2
    (2)
    Mineralogy of Carbonate Sediments

    Prepared by:
    Mansour Al-Hashim
    Preview of Lab 1

    General classification of sedimentary rocks

    Simple classification of carbonate rocks

    Some facts about carbonate rocks

    Techniques for examining carbonate rocks


    Objectives of Lab 2
    Introduction to carbonate minerals
    Studying the main three carbonate groups
    Studying the three most important carbonate
    minerals in some details
    Distinguishing between calcite, aragonite, and
    dolomite under the microscope (staining)
    Carbonate Minerals
    Carbonate minerals contain the CO3 anion
    CO3 combines with cations (Ca, Mg, Fe, Mn, and Zn)
    to form most carbonate minerals
    The common carbonate minerals fall into three groups:
    1. Calcite group
    2. Dolomite group
    3. Aragonite group
    Calcite, dolomite, and aragonite are the only
    volumetrically important minerals in carbonate rocks
    Carbonate Minerals
    Calcite Group (Hexagonal)
    The most common minerals of this group are:
    1. Calcite CaCO3

    2. Magnesite MgCO3

    3. Siderite FeCO3

    4. Rhodochrosite MnCO3

    5. Smithsonite ZnCO3
    Calcite CaCO3
    Properties:
    Crystal system: hexagonal
    Cleavage: perfect rhombohedral
    Color: usually white/colorless in hand specimens and
    colourless in plane polarized light
    Moderate to high negative relief
    Calcite CaCO3
    Properties (continued):
    High--order interference colors, commonly white
    High
    Reacts strongly and readily with cold, dilute HCl
    Depending on the magnesium content, there are two
    types of calcite: low-
    low-Mg calcite and high-
    high-Mg calcite
    Dominant mineral of limestones in rocks older than the
    Tertiary
    Calcite under the microscope (PPL)
    Calcite under the microscope (XPL)
    Carbonate Minerals
    Aragonite Group (Orthorhombic)
    The most common minerals of this group are:
    1. Aragonite CaCO3

    2. Strontianite SrCO3

    3. Cerussite PbCO3
    Aragonite CaCO3
    Characteristics:
    Crystal system: orthorhombic
    Cleavage: lacks the rhombohedral cleavage
    Color: colorless, white, pale yellow, variously tinted in
    hand specimens and colourless in thin sections
    Relief changes with rotation
    Effervesces vigorously in cold, dilute HCl
    Aragonite CaCO3
    Characteristics (continued):
    High--order interference colors, commonly white
    High
    Alters readily to calcite and may be replaced by
    dolomite or other minerals
    Has a very low Mg content
    Important in Cenozoic-
    Cenozoic-age and modern carbonate
    rocks and sediments
    Fibrous (acicular or needle-like) crystals
    Acicular aragonite under the microscope

    From Scholle & Ulmer-Scholle (2003)


    Acicular aragonite under the microscope

    From Scholle & Ulmer-


    Ulmer-Scholle (2003
    (2003))
    Acicular aragonite under the microscope

    From Scholle & Ulmer-


    Ulmer-Scholle (2003
    (2003))
    Acicular aragonite under the microscope

    From Scholle & Ulmer-


    Ulmer-Scholle (2003
    (2003))
    Carbonate Minerals
    Dolomite Group (Hexagonal)
    The most common minerals of this group are:
    1. Dolomite CaMg(CO3)2

    2. Ankerite CaFe(CO3)2
    Dolomite CaMg(CO3)2
    Properties:
    Crystal system: hexagonal
    Cleavage: perfect rhombohedral
    Color: pink, white, gray, green, brown, black, or colorless
    Dolomite crystals are usually subhedral to euhedral, with
    planar boundaries.
    Best identified through staining, and by its rhombic, often
    zoned, crystals.
    Dolomite CaMg(CO3)2
    Properties (continued):
    Only reacts with hot HCl or if powdered
    Colourless in plane polarized light
    Relief changes with rotation
    High--order white or grey interference colors
    High
    Dominant mineral of dolomites
    Commonly forms euhedral rhombs
    Dolomite under the microscope

    From Scholle & Ulmer-


    Ulmer-Scholle (2003
    (2003))
    Dolomite under the microscope

    From Scholle & Ulmer-


    Ulmer-Scholle (2003
    (2003))
    Dolomite under the microscope

    From Scholle & Ulmer-


    Ulmer-Scholle (2003
    (2003))
    Dolomite under the microscope

    From Scholle & Ulmer-


    Ulmer-Scholle (2003
    (2003))
    Distinguishing between Carbonate
    Minerals
    Visual differentiation between carbonate minerals is
    fundamental to studies of carbonate petrography, correlation,
    and genesis.
    It is difficult to distinguish between calcite, aragonite, and
    dolomite in hand specimens and thin sections.
    There is difficulty because their physical characteristics are
    very similar.
    Identification of these minerals is aided by etching and
    staining techniques.
    Staining (1
    (1)
    Staining methods have been used in carbonate
    analysis since 1887 (Lemberg).
    Provides a rapid means of recognizing the
    textural and compositional differences in the
    rock.
    Provides a means of establishing the identity of
    the carbonate minerals under study.
    Staining (2
    (2 )
    Doesnt require sophisticated laboratory facilities
    Doesn
    and can be applied to cores and cuttings.
    For identification of carbonate minerals,
    alizarine red S and Harris' hematoxylin stains
    are recommended because they are fast,
    efficient, and dependable.
    Distinguishing between Calcite and
    Dolomite
    Step 1
    1) Etch with 1.5% HCl for 10 to 15 sec.
    2) Wash with distilled water
    Result:

    - Calcite and ferroan calcite show considerable


    etch
    - Dolomite and ferroan dolomite show negligible
    etch.
    Distinguishing between Calcite and
    Dolomite
    Step 2
    1) Dissolve 0.2 g Alizarin red S in 100 cc of 1.5%
    HCl acid (ARS)
    2) Dissolve 2 g potassium ferricyanide in 100 cc
    of 1.5% HCl acid (PF)
    3) Mix ARS with PF in the ratio ARS:PF = 3:2
    4) Stain for 30 to 45 sec.
    Distinguishing between Calcite and
    Dolomite
    Result of step 2:
    - Calcite is very pale pink to red

    - Ferroan calcite is very pale pink-


    pink-red and pale
    blue--dark blue
    blue

    - Dolomite takes no stain

    - Ferroan dolomite becomes deep turquoise


    Distinguishing between Calcite and
    Dolomite
    Step 3
    - Stain with ARS solution for 10 to 15 sec.

    Result:

    - Calcite and ferroan calcite become very pale


    pink-red
    - Dolomite and ferroan dolomite take no color

    (This method is after Dickson, 1965)


    The End

    You might also like