2000 White GensisofMuruntau
2000 White GensisofMuruntau
2000 White GensisofMuruntau
net/publication/250276447
Setting of the giant Muruntau Gold Deposit: Implications for ore genesis
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Abstract: The Muruntau gold deposit is situated in the Kyzyl Kum Desert of Uzbekistan. It is currently
being mined in the world’s largest open pit gold mine with production believed to be of the order of two
million ounces per annum. The open pit measures about 3.5 by 2.5 km and extends to a depth of 350m. The
gold ore resource in the Muruntau deposit, including production, is about 170 million ounces of gold
(Anonymous, 1996). This paper presents a summary of the deposit geology and its regional geological
setting. Information used in this paper has been generated from observations made on two visits to the mine
and its environs, and a review of the Russian- and English-language literature.
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Wilde, A. 2000. Setting of the giant Muruntau Gold Deposit Journal of the Virtual Explorer - Volume 1
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Wilde, A. 2000. Setting of the giant Muruntau Gold Deposit Journal of the Virtual Explorer - Volume 1
2 (Savchuk et al., 1991). Savchuk et al. (1991) recognise Muruntau, Devonian and Carboniferous carbonate rocks
an older Bokalinsk Suite and younger Nuratinsk suite. are thrust over the top of the older basement rocks ( Fig.
The Bokalinsk Suite outcrops rarely and comprises only 3; Drew et al., 1996). The age of this thrusting is
5% of outcropping intrusions. The Nuratinsk Suite is therefore Carboniferous or younger. Drew et al., (1996)
predominantly composed of granite and granodiorite and consider that the contact between the Besopan 3 and 4 is
comprises 95% of exposed intrusions in the Kyzyl Kum marked by a Carboniferous shear zone, the Sangruntau-
region. It is spatially and probably temporally associated Tamdytau shear zone.
with tin mineralisation in the region. Granites of this A thrusting event at this time helps to explain the
suite intrude folded sedimentary rocks of the Basement change at the top of the Carboniferous (in the Karatau
and Cover Sequence 1. range) from shallow marine to terrestrial. The
Two intrusive bodies and dykes of several widespread intrusion of granitic intrusions also occurred
compositions are known in the vicinity of the Muruntau at this time, possibly in response to crustal thickening by
deposit. One of the intrusive bodies, the Sardarin Pluton, thrusting.
is 12 km south of the Muruntau deposit, but is apparently
not exposed. Its extent has been determined from drilling Permo-Triassic Deformation
and from interpretation of airborne magnetic data. The Alexeiev et al., (1997) have documented a major
other intrusive body, the Murunski Pluton, is composed Permo-Triassic deformation event in the Karatau Range,
of a medium-grained alaskite, and was intersected north of Muruntau (Fig. 1). This event is synchronous
beneath the deposit in an exploratory diamond drill hole with the major unconformity between Cover Sequences
at a depth of 4 km (Kostitsyn, 1996). Contact 1 and 2. The main manifestation of this event is the giant
metamorphism about the pluton is manifested as biotite Karatau Fault (Fig. 1) which has right-lateral
porphyroblasts and locally, as andalusite and cordierite displacement of 150 km and related steeply-plunging Z-
porphyroblasts (Kotov and Poritskaya, 1992; Drew et al., shaped folds (Alexeiev et al., 1997). A parallel structure
1996). Hornfels has been observed in the drill holes occurs about 50 km south of Muruntau (Fig. 1). Outcrops
beneath the Muruntau deposit. of the basement and Cover Sequence 1 throughout the
The Sardarin Pluton yielded a Rb-Sr isochron of 286 ± region are elongate in the direction of strike-slip faulting
1.8 million years and initial ratio of 0.7078 (Kostitsyn, (i.e. NW) as are the principal magnetic trends.
1996). The Murunski Pluton yields an identical isochron A second set of faults trends NE and ENE (Fig. 3). A
of 287 ± 1.8 million years (Permo Carboniferous) and fault of this orientation, the Muruntau-Daugyztau fault,
initial 87Rb/87Sr ratio of 0.716. is spatially and probably temporally associated with
mineralisation at Muruntau (Fig. 3). The age of this and
parallel structures is clearly Carboniferous or later.
Major deformation events
Figure 3 shows NE-trending anticlinal and synclinal
Caledonian (Silurian) Deformation axes paralleling, and probably related to, major strike-
The Basement is strongly folded and pelitic rocks have slip faults. These folds are open with a wavelength of
a well-developed axial planar cleavage. Isoclinal folds approximately 1 km and the axes plunge shallowly
with east-striking axial planes overturned to the north north-eastwards. Much of the gold at Muruntau is
have been described (e.g. Kotov and Poritskaya, 1992). located within the axial zone of the syncline.
Such isoclinal folding is interpreted to have occurred
prior to deposition of Cover Sequence 1, which exhibits Late Mesozoic and Tertiary Deformation
open folds with vertical axial planes. The east-west Localised open fold sets with an interpreted post-
trending fold visible west of Muruntau (Fig. 3) is Tertiary age are superimposed on the Hercynian
believed to be of Caledonian age. deformation. These folds occur in Tertiary exposures
Metamorphic grade of the Basement did not exceed about 50 km to the south-west of the Muruntau deposit.
greenschist facies over much of the region. Rb - Sr dating of A further 70 to 100 km of right-lateral movement
metamorphic micas has yielded a Caledonian (Early occurred along the Karatau fault during the late
Devonian) cooling age of 401 ± 11 million years (Kostitsyn, Mesozoic and early Tertiary (Alexeiev et al., 1997).
1996). This age is consistent with the unmetamorphosed
nature of unconformable Cover Sequence 1.
Muruntau gold deposit
Hercynian (Late Carboniferous) Deformation Geometry of the Mineralisation
There is evidence of a deformation event during the The geometry of the Muruntau deposit was controlled
Hercynian (late Carboniferous) in this region. North of by three main factors: presence of the carbonaceous and
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Wilde, A. 2000. Setting of the giant Muruntau Gold Deposit Journal of the Virtual Explorer - Volume 1
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Wilde, A. 2000. Setting of the giant Muruntau Gold Deposit Journal of the Virtual Explorer - Volume 1
Figure 3. Geology of part of the Tamdytau Mountains showing the setting of the Muruntau deposit, based on compilation of Soviet mapping by
Drew (1993).
Sericite and chlorite is limited in extent relative to the basin formation that spanned the Late Permian and Early
earlier alteration, being confined to narrow vein selvages Triassic. The event is marked by a profound change in
of a few millimetres extent (Kotov and Poritskaya, 1992) sedimentary depositional environments from a marine
and pervasive replacement of feldspar. carbonate shelf-type sedimentation in the Late
A ubiquitous alteration phase is pale-coloured dravitic Palaeozoic to non-marine terrigenous, saline to
tourmaline (Gilbert, 1995). Microprobe analysis reveals hypersaline depositional settings in the Jurassic and
that these dravites are rich in V (up to 2.7% V2O3), Mg Cretaceous characterized by the "red-beds" of Cover
and Na (Gilbert, 1996). Carbonaceous material is locally Sequence 2 (Syr Daria Basin). This change can be
abundant in the pit. Petrographic determinations on observed through much of Central Asia.
stockpiled ore samples reveal an average of 4% by Mineralisation was emplaced within the pre-existing
volume and locally as much as 50% (Schandl, 1997). metamorphic aureole of a buried Permo-Carboniferous
Marakushev and Khokhlov (1992) describe carbon felsic intrusive. Isotopic data indicate that mineralisation
"fronts" but the relationship between carbon "fronts" and occurred about 30 million years later than cooling of the
gold is not well understood at this time. intrusion below its Rb-Sr closure temperature (Kostitsyn,
1996). The intrusion and its metamorphic aureole
Age of the Hydrothermal System(s) probably controlled the subsequent development of the
One of the most controversial aspects of the Muruntau
orebody is its age. Alteration replaces and exploits a pre-
existing cleavage and also overprints contact
metamorphic andalusite and cordierite associated with
the buried alaskite pluton beneath the deposit (Kotov &
Poritskaya, 1992; Drew et al., 1996). These observations
strongly suggest that alteration was considerably later
than peak deformation, and post-dates the thermal event
accompanying the emplacement of the adjacent granite.
Kostitsyn (1993, 1996) provides three Rb-Sr
mineralisation ages: 257.6 ± 2.2, 230.2 ± 3.5 and 219.4 ±
4.2 million years (Permian to Triassic). All these ages are
significantly younger than the crystallisation age of the
Murunski intrusive, 4 km beneath the Muruntau deposit.
Genesis
Gold deposition is inferred to have occurred during a Figure 4. Modal mineralogy of 64 samples from Muruntau (Schandl,
major period of strike-slip movement and terrestrial 1997; I.P. Zarevich, unpub. data).
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Wilde, A. 2000. Setting of the giant Muruntau Gold Deposit Journal of the Virtual Explorer - Volume 1
ore-forming hydrothermal cell because of the Outcrop Analogs for Coeval Carbonate Reservoirs in the N.
permeability variation imposed on the host succession by Caspian Basin: "Carbonate Reservoir Systems", AAPG.
the intrusion and its metamorphic halo. The aureole and DREW, L.J., BERGER, B.W., KURBANOV N.K., 1993, Geology
the intrusive could have acted as a brittle and dilatant and Structural Evolution of the Muruntau Gold Deposit,
block, generating a more strongly fractured zone Kyzylkum Desert, Uzbekistan. Ore Geol. Reviews, 11, 175
containing more dilatant fractures than the adjacent more - 196.
ductile host-rocks. It is not clear however, if the intrusion DREW, L.J., 1993, Geologic Map of the Tamdy Mountains,
could have remained a source of a thermal anomaly Uzbekistan. USGS Misc. Investigation Map I-2386.
focussing a hydrothermal cell for over 50 million years GILBERT, D., 1995, Petrology and geochemistry of samples
after emplacement. from the Muruntau Gold Mine and Cosmanachi Silver
Mine, Uzbekistan. BHP Company Memo, 7401.
Acknowledgements GILBERT, D., 1996, Possible Exploration Significance of
Vanadiferous Dravite from the Muruntau Gold Mine
I would like to thank the following: Yuri Savchuk for sharing Uzbekistan. BHP Company Memo, 7414.
his vast knowledge of the Muruntau deposit and its KOTOV, N.V. & PORITSKAYA, L.G., 1992, The Muruntau Gold
surroundings, the Uzbek government for permission to visit the Deposit: Its Geologic Structure, Metasomatic Mineral
mine and BHP Minerals for permission to publish this paper. Associations and Origin. Int. Geol. Rec., 34/1,77-87.
The manuscript was much improved by comments from KOSTITSYN YU. A., 1993, Rb-Sr Isotopic Studies of the
Douglas Haynes and Noel White. Jim Mavrikios drafted the Muruntau Deposit: Isochrone [sic] Dating of the ore veins.
figures. Geokhimiya, 9, 1308-1318. (In Russian).
KOSTITSYN YU. A., 1996, Rb-Sr Isotopic Study of the Muruntau
References Deposit: Magmatism, Metamorphism and Mineralization.
Geochem. Intl., 34/12, 1009-1023.
ANONYMOUS, 1996, Investment Opportunities in Mining and LAPOINTE PH. A., RERNET-ROLLANDE M. C., ZHEMCHUZHNIKOV
Minerals in Uzbekistan: United States Trade & V. G., COOK. H. E., ZEMPOLICH. W. G. & LEHMANN P.J.,
Development Agency; 150 pp. 1997, Evaporite Collapse Breccia versus Karst Breccia:
ALEXEIEV D.V., COOK H. E., BUVTYSHKIN, V. M., Golub L. Y., The Late Devonian-Lower Carboniferous Da1atorlan Unit,
ZHAIMINA, V. YA., Dynamics Of Late Paleozoic Collisions Bolshoi Karatau Mountains, Southern Kazakhstan:
At The South-Western Margin Of The Kazakhstania "Carbonate Reservoir Systems", AAPG.
Paleocontinent: New Evidence From The Bolshoi Karatau MARAKUSHEV, A.A. & KHOKHLOV, V.A., 1992. A Petrological
Mountains (Northwestern Tien Shan). Dynamics Of Active model for the genesis of the Muruntau Goid Deposit. Int.
Margins And Collision Zones. European Union Of Geol. Rev., 34/1, 59-76.
Geologists Meeting SAVCHUK YU, S., MUKHIN, P,A. & MESHCHERYAKOVA, L.V.,
BURSHTEIN E., 1998, Oil, Gas and Metal Potential of the 1991, Late Palaeozoic Granitoid Magmatism and Kyzyl
Ferghana, Syr Darya and Amu Darya Basins in Middle Kum Ore formations from a Plate Tectonics Viewpoint.
Asia, Unpub. Report to BHP Minerals, Moscow State Geotectonics, 25/4, 326-339.
University. SCHANDL E., 1997, Report on Samples from Muruntau,
COOK H. E., ZHEMCHUZHNIKOV, V. G., ZEMPOLICH. W. G., Uzbekistan: Unpub. Report to BHP Minerals, 66 pp.
ZHAIMINA, V. YA., LEHMANN. P. J., LAPOINTK PH. A., USPENSKIY YE I. & ALESHIN, A.P., 1993. Patterns of Scheelite
BUVTYSHKIN, V. M., 1997, Devonian and Carboniferous Mineralisation in the Muruntau Gold Deposit, Uzbekistan.
Carbonate Platforms in the Karatau of S. Kazakhstan: Int. Geol. Rev., 35, pp. 1037-1051.