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Kelian |
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Kalimantan, Indonesia |
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Au
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Super Porphyry Cu and Au
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The Kelian gold deposit is located in East Kalimantan, Indonesia, approximately 5 km south of the equator.
Kelian is Indonesia's largest gold-only deposit containing >200 t Au. It is classified as a carbonate-base metal enriched epithermal gold system (Corbett and Leach, 1998).
Kelian is exposed within a structural window of Eocene felsic volcaniclastic rocks and intruded by Miocene andesitic stocks surrounded by Eocene to Miocene terrestrial and marine sediments of the Kutai Basin which dominate the regional geology.
A complex series of mineralised and unmineralised breccias, which include tectonic, hydrothermal, phreatomagmatic and phreatic breccias (diatreme breccias) cross-cut the lithologies of the window, and have been subsequently intruded by late-stage felsic plugs.
Plio-Pleistocene basaltic dykes cross-cut all Eocene to Miocene rocks.
Contemporaneous basaltic lava and associated mafic pyroclastic and volcaniclastic rocks overlie a Plio-Pleistocene erosional surface.
Felsic volcaniclastic sediments, andesitic stocks, carbonaceous sedimentary rocks and a variety of hydrothermal, phreatic and phreatomagmatic breccias host the mineralisation. The phreatomagmatic breccias and associated igneous rocks post-date early stage alteration and mineralisation, and pre-date main stage precious and base-metal mineralisation.
Four stages of overlapping alteration and mineralisation have been recognised at Kelian as follows (van Leeuwen et al., 1990):
Stage I). Chlorite + carbonate + sericite + pyrite ± quartz in the cores of the larger andesite bodies.
Stage IIa). Localised fracturing and sericite ± quartz deposition. This was followed by Stage IIb which comprises a major period of polyphase fracturing and hydrothermal brecciation with associated boiling of hot (290 to 300° C), dilute and CO2 -rich fluids and the development of replacement/vein alteration composed of adularia + sericite +quartz + pyrite with subordinate As-Ag and possibly some Au. Deeper in the system, a quartz-sericite-carbonate assemblage formed without adularia.
Stage III). Renewed magmatic activity released volatiles into the hydrothermal system producing hot (300 to 330°: C), relatively saline, CO2 -rich brines, and extensive fracturing and hydrothermal brecciation. This was accompanied by boiling and the deposition of various carbonates, ± quartz ± sericite and gold-base metal mineralisation with a complex zonation of carbonate minerals.
Stage IV). A late, widespread influx of relatively cool (<200$deg; C), low pH (<3 to 4), CO2 -rich steam heated fluids formed a kaolinite + Fe/Mn carbonate + pyrite ± hematite ± cinnabar assemblage in the top and marginbs of the deposit.
Subsequent uplift of more than 900 m and erosion took place during the middle- to late Miocene with basaltic volcanism in the Plio-Pleistocene. A further cycle of erosion, beginning in the Pleistocene removed most of the younger volcanic cover to expose the deposit.
The pre-mining geological resource in 1989 amounted to >75 Mt @ 1.8 g/t Au.
The most recent source geological information used to prepare this decription was dated: 1999.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Davies A G S, Cooke D R and Gemmell J B 1999 - Characteristics, timing and formation of diatreme breccias and the Kelian gold deposit, East Kalimantan, Indonesia: in Pacrim 99, International Congress on Earth Science, Exploration and Mining Around the Pacific Rim, Proc. Pacrim 99 Conference, Bali, Indonesia AusIMM, Melbourne pp 81-90
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Davies A G S, Cooke D R, Gemmell J B and Simpson K A, 2008 - Diatreme Breccias at the Kelian Gold Mine, Kalimantan, Indonesia: Precursors to Epithermal Gold Mineralization: in Econ. Geol. v103 pp 689-716
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Davies A G S, Cooke D R, Gemmell J B, van Leeuwen T, Cesare P and Hartshorn G, 2008 - Hydrothermal Breccias and Veins at the Kelian Gold Mine, Kalimantan, Indonesia: Genesis of a Large Epithermal Gold Deposit: in Econ. Geol. v103 pp 717-757
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Setiabudi B T, Campbell I H, Martin C E and Allen C M, 2007 - Platinum Group Element Geochemistry of Andesite Intrusions of the Kelian Region, East Kalimantan, Indonesia: Implications of Gold Depletion in the Intrusions Associated with the Kelian Gold Deposit : in Econ. Geol. v102 pp 95-108
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van Leeuwen T M, Leach T, Hawke A A, Hawke M 1990 - The Kelian disseminated gold deposit, East Kalimantan, Indonesia: in J. of Geochemical Exploration v35 pp 1-61 =61 pages (copied 2 onto one)
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White, N.C., Leake, M.J., McCaughey, S.N. andd Parris, B.W., 1995 - Epithermal gold deposits of the southwest Pacific: in J. of Geochemical Exploration v.54, pp. 87-136.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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