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Darasun, Teremkyn, Talatui |
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Zabaikalsky Kray, Russia |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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Darasun, Teremkyn and Talatui are neighbouring gold deposit, the largest of a group of similar occurrences that constitute the Darasun Gold Field of the Zabaikalsky Kray of the Eastern Transbaikal region in Russia, 60 km SSE of the city of Chita. They are quartz-carbonate gold vein deposits, located ~70 km southwest of the Mongolian-Okhotsk suture zone, generated by the closure of the Mongolian-Okhotsk Ocean at the end of the Mesozoic. Teremkyn is 5 km northwest of Darasun, and in the same granodiorite intrusive, while Talatui is 12 km northwest of Darasun.
Darasun was discovered in 1861 and produced 118 t of gold from underground operations and an additional 40 t from surface (gold placer) operations. Production
ceased in 1996 before being restarted with higher gold prices in 2003.
The Darasun goldfield is located within a tectonically complex block of Palaeozoic magmatic rocks. The oldest of these is the ultramafic and mafic rocks of the Early Palaeozoic Kruchinsky Complex, consisting mainly of pyroxene-hornblende, hornblende and olivine gabbros, and minor serpentinitic pyroxenites, plagioclase dunites, peridotites and anorthosites. These gabbroic rocks are intruded to the south and southeast by the Middle Palaeozoic Krestovsky Complex, consisting of diorites, quartz diorites, granodiorites, granites and aplites dated at 320 to 316 Ma. The Late Palaeozoic to Early Mesozoic leucogranites, granodiorites, syenites and granosyenites of the Olyokminsky Complex represent an extension to the northeast and southeast of the Krestovsky Complex. A Triassic subalkaline granodiorite, with minor biotite-amphibole-two feldspar diorite, granosyenite, granites, alaskite granite intrusion (234±8 Ma, biotite K-Ar age) forms the Amanansky Complex to the northwest of Darasun. The Middle Jurassic to Early Cretaceous Amudzhikan-Sretensky Complex is the youngest magmatic suite of the region. It includes subvolcanic and effusive high potassium rocks with a wide range of compositions, occurring as dykes and stocks of porphyritic diorites, granosyenite, syenite, and granite porphyries, plagioporphyry dykes, felsites, felsite porphyries, trachybasalts, trachy-andesites, latites, trachydacites, rhyodacites, quartz porphyries, and rhyolites. This latter suite occurs in spatially closey associated with the orebodies but is volumetrically small. Within the Darasun deposit, it forms a high K, calc-alkaline series, characterized by the occurrence of magnetite inclusions within plagioclase and biotite, and by anomalous enrichments in Ag, Au, Mo, and W.
Both the ore veins and subvolcanic rocks are located in the same brittle and ductile structures. The deposits are located within and around the porphyry stocks and associated apophyses and can be traced from hundreds of metres to kilometres downdip or along strike. At Darasun and Teremkyn, veins and ore shoots are found within a system of northeast to northwest trending faults with sharp walls and alteration haloes. At Talatui, the ore occur as northwest-trending ore shoots with transitional boundaries and spatially irregular, en echelon arranged alteration zones.
The Darasun deposit includes more than 250 steeply dipping gold-mineralised quartz-sulphide veins spatially related to a district-scale volcanic dome centred on a highly irregular, high K, calc-alkaline, latitic, granodiorite to plagiogranite porphyry intrusion of the Amudzhikan-Sretensky Complex. The intrusive is accompanied by explosive breccias and by northwest-trending dyke-like apophyses. The veins mostly strike NE and NW, emphasising larger fault zones intersecting in the deposit area, but are also complicated by post-mineralisation displacements, pinching and swelling. Some veins are localised in concentric and radial fractures in the volcanic dome. Ore is also associated with the explosive breccia and as disseminations. The host rocks are the Early Palaeozoic gabbroids and Middle to Early Paleozoic granitoids. Intense propylitic alteration predates ore formation, while intense tourmaline, chlorite, quartz-sericite-pyrite-carbonate alteration is coeval with ore deposition is observed close to the veins. The ore veins contain quartz and 40 to 60 vol.% sulphides. Major sulphide minerals are pyrite, arsenopyrite, chalcopyrite, sphalerite, tetrahedrite-tennantite, pyrrhotite and galena with minor stibnite, tetradymite and bournonite. Gold occurs in its native form with a fineness 890-900, and as Au tellurides closely associated with chalcopyrite, tetrahe-drite-tennantite and arsenopyrite. Four major mineralising stages are recognised: i). barren quartz- tourmaline stage; ii). quartz-pyrite-arsenopyrite stage; iii). major productive quartz-polysulphide stage; and iv). barren quartz-carbonate stage.
Vein lengths are up to 2 km along strike and 1.0 to 1.2 km along dip, with a width that varies from 5 to 20 cm. Ore shoots ranges from about 100 to 1000 m in length. Textures vary from fine to coarse grained and the crystals are predominantly euhedral. Massive, lenticular, lens-like, crust-like and brecciated veins were documented. Alteration has been dated at 165±7 Ma. Economic mineralisation averages ~15 g/t Au, accompanied by ~28 g/t Ag, ~0.44% Cu, 0.015 wt.% Bi and ~1.35 wt.% As.
The Teremkyn deposit consists of a series of gold-bearing tourmaline-quartz sulphide veins and zones of disseminated ore. Gold is visible in the orebodies and occurs as inclusions with volumetrically minor Ag, Cu, Bi, Pb, Zn, and Sb minerals. The host are Early Paleozoic gabbroids of the Kruchinsky Complex and the Late Paleozoic to Early Mesozoic granitoids of the Olyokminsky Complex. The deposit itself is localised at the intersection of a system of faults and the granodiorite porphyry of the Amudzhikan-Sretensky Complex. Gold is extremely irregularly distributed, but occurs within clearly defined ore shoots. The highest grades are in northeast-trending veins dipping 50°S, as well as in south- and northeast-trending veins dipping 10 to 30°S. Ore shoots occur in areas of pinch and swell, where vein density is the highest.
The veins carry quartz, tourmaline, pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, marcasite, pyrrhotite, native gold, electrum, bismuth minerals (native bismuth, bismuthine, aikinite, cosalite, matildite, and tetradymite), bournonite, lead sulphoantimonites, carbonate, chalcedony, zeolite, and fluorite. Massive quartz and rare molybdenite predate gold precipitation.
Three stages of vein formation are recognised at Teremkyn: (1) the formation of quartz-tourmaline-pyrite, followed by quartz-arsenopyrite assemblages; (2) the volumetrically most important stage corresponds to the generation of quartz-pyrite-chalcopyrite-native gold, quartz-chalcopyrite-sphalerite-galena-matildite-native gold, quartz-chalcopyrite-cubanite-pyrrhotite-native gold, and quartz-bournonite-tetradymite-joseite-pilsenite-galena-native bismuth-bismuthine-aikinite-cosalite-native gold-tetrahedrite-calcite assemblages; and (3) post-ore quartz-carbonate assemblage. Gold grains are mostly round in shape, up to 50 µm in size, and form together with quartz, chalcopyrite, sphalerite, galena, and bismuth minerals. Quartz-sericite-carbonate and chlorite-carbonate-talc hydrothermal alteration of the host rocks are coeval with the main stage of mineral precipitation and dated at 144±10 Ma.
The Talatui deposit is hosted by hydrothermally altered gabbro, gabbro-monzonite, gabbrodiorite, and diorite of the Early Kruchininsky Complex, which are in turn
cut by Middle Jurassic to Early Cretaceous dykes and stocklike intrusions of porphyritic diorite, granite porphyry, granodiorite porphyry, quartz porphyry and lamprophyres of the Amudzhikan-Sretensky Complex. The Kruchininsky Complex shares contacts with the Triassic Amanansky Complex, the Late Palaeozoic Olyokminsky Complex and the Middle Palaeozoic Krestovsky Complex to the northwest, northeast and south respectively.
The veins are arranged in an en echelon pattern, each with a zoned alteration assemblage of proximal adularia-chlorite-sericite-quartz-calcite; intermediate orthoclase-actinolite-phlogopite-pyrite-anhydrite-barite-quartz; and outer orthoclase-quartz-epidote-magnetite-rutile-phlogopite-tourmaline.
The orebodies trend northwest mostly as veins with subordinate lenticular zones and transitional contacts with the host rocks. Thickness varies from 0.25 to 20 m. Individual bosied may be traced for 2000 m along strike and for 200 to 500 m downdip. They are characterised by alternations of 4 to 20 m long pinches and 40 to 120 m long swells.
The average grade is 9.5 g/t Au with associated Ag (6.4 g/t), Cu (0.16 wt.%), W (0.084 wt.%), and Bi (0.014 wt.%). The major vein minerals are K-feldspar, magnetite, and quartz, which account for more than 50 vol.%. The sulphides are mainly by pyrite and chalcopyrite which constitute more than 15 vol.% of the vein, while epidote, chlorite, tourmaline and phlogopite are minor phases. Scheelite, sphalerite, titanite, hematite, goethite and hercynite are all trace vein phases, with galena, siegenite, matildite, pilsenite, hessite, wittichenite, anhydrite, barite, wolframite, and zircon (but also gypsum and pyrrhotite) as small inclusions within the sulphides. Replacement of magnetite after hematite (i.e., magnetite pseudomorph over platy hematite) is a typical ore texture. Gangue minerals include K feldspar, quartz, epidote, tourmaline, biotite, phlogopite, sericite, actinolite, tremolite, clinochlore, chalcedony and carbonates.
Current resources at the Darasun project are (Highland Gold Mining Limited, 2010)
Measured + Indicated Resources - 12.498 Mt @ 10.31 g/t Au;
Inferred Resources - 3.656 Mt @ 14.7 g/t Au;
The most recent source geological information used to prepare this decription was dated: 2010.
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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Lyubimtseva, N., Bortnikov, N., Borisovsky, S., Prokofiev, V. and Vikenteva, O., 2018 - Fahlore and Sphalerite from the Darasun Gold Deposit in the Eastern Transbaikal Region, Russia: I. Mineral Assemblages and Intergrowths, Chemical Composition, and Its Evolution: in Geology of Ore Deposits v.60, pp. 93-120.
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Prokofiev V Yu, Garofalo PS, Bortnikov NS, Kovalenker VA, Zorina LD, Grichuk DV and Selektor SL, 2010 - Fluid Inclusion Constraints on the Genesis of Gold in the Darasun District (Eastern Transbaikalia), Russia : in Econ. Geol. v105 pp. 395-416
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Seltmann, R., Soloviev, R., Shatov, V., Pirajno, F., Naumov, E. and Cherkasov, S., 2010 - Metallogeny of Siberia: tectonic, geologic and metallogenic settings of selected significant deposits: in Australian J. of Earth Sciences v.57, pp. 655-706.
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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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