Te and Se mineralogy of the high-sulfidation Kochbulak and Kairagach epithermal gold telluride deposits (Kurama Ridge, Middle Tien Shan, Uzbekistan). Mineralogy and Petrology 87: 187-207 (original) (raw)
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Mineralogy and Petrology, 2006
The Late Paleozoic Kochbulak and Kairagach deposits are located on the northern slope of the Kurama Ridge, Middle Tien Shan, in the same volcanic structure and the same ore-forming system. Au–Ag–Cu–Bi–Te–Se mineralization is confined to veins and dissemination zones accompanied by quartz-sericite wall-rock alteration. The tellurides, calaverite, altaite, hessite, and tetradymite are widespread at both deposits; at Kairagach selenides and sulfoselenides of Bi and Pb are common, while at Kochbulak Bi and Pb telluroselenides and sulfotelluroselenides are typical. The paragenetic sequence of telluride assemblages are similar for both deposits and change from calaverite + altaite + native Au to sylvanite + Bi tellurides + native Te, Bi tellurides + native Au, and, finally, to Au + Ag tellurides with time. These mineralogical changes are accompanied by an increase in the Ag content of native gold that correlates with a decrease in temperature, fTe2 and fO2 and an increase in pH.
Geology of Ore Deposits, 2003, V. 45(3), p. 171–200.
The Late Paleozoic Kairagach epithermal gold deposit belongs to the high-sulfidation (acid–sulfate) type. It is located at the northern slope of the Kuramin Ridge in the central Tien Shan, 3.5 km northwest of the Kochbulak deposit, being confined to the volcanic andesite–dacite sequence (C2–3) composing the northeastern segment of the Karatash caldera. Volcanogenic sequences are intruded by subvolcanic dacite–porphyry and diorite–porphyry intrusions, as well as granodiorite–porphyry and porphyritic diabase dikes of the northeastern strike. The gold–sulfide–selenide–telluride mineralization of the Diabazovaya zone, which encloses the main gold resources, associates with these dikes. Unlike typical epithermal deposits of the high-sulfidation type with Au–Cu geochemical specialization of ores, the Kairagach deposit is characterized by distinct Au–Sn–Bi–Se–Te mineralization, which includes over 80 ore minerals, including new and rare ones. This paper discusses data on the geological structure of the deposit, ore geochemistry, variations in chemical composition, mode of occurrence and parageneses of native elements (Au, Ag, Te, Sn, Bi); sulfides of Fe, Cu, Pb, Zn, and Ag; fahlores of the tetrahedrite–tennantite–annivite–goldfieldite series; bismuthinite–aikinite, junoite, and pavonite sulfosalts; Cu and Fe sulfostannate; various Au, Ag, Pb, Fe, Hg, Bi, and Sb tellurides and Bi sulfoselenides; and Fe and Sn oxides. The chemical composition of ordinary, high-grade, and bonanza ores and the vertical and lateral (including hidden) mineralization zoning, as well as the succession of mineral parageneses, P–T parameters, composition of mineral-forming fluids, and main factors and mechanisms responsible for the formation of goldproductive mineral associations, are considered. The variations in the S, C, O, and H compositions of ore minerals are used to define probable sources of water and ore components in ore-forming fluids. The results of thermodynamic modeling of probable gold occurrence and transportation in the mineral-forming solution are also discussed.
Russian Geology and Geophysics, 2007
The structure and petrologic composition of new gold-ore provinces in southeastern East Sayan (Tissa-Sarkhoi cluster) are considered. Several morphogenetic types of gold mineralization have been established: quartz veins with beresitization zones, veinlet-disseminated ores in granitoids, and listwaenitization and sulfidation zones in effusions of the Sarkhoi Group and intrusive rocks of the Late Riphean Khorin-Gol complex. According to geochronological dates and some mineralogical and geochemical features, the gold mineralization is close in age to these Precambrian island-arc complexes. Parageneses of two stages of ore formation have been recognized: early high-temperature (250-460 °C) gold-pyrite and late low-temperature (110-280 °C) gold-telluride. The latter mineralization is widespread and is represented by tellurides of Au, Ag, Pb, Bi, and Ni -petzite, calaverite, hessite, tellurobismuthite, altaite, and melonite. Native gold associated with these tellurides is characterized by a fineness of 750-900‰. The intimate temporal and spatial relationships of the gold mineralization with island-arc volcanoplutonic complexes and the wide occurrence of its veinlet-disseminated type suggest that this is porphyry gold mineralization related to the Late Riphean-Vendian island-arc magmatism.
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2005
We describe two epithermal telluride-selenide bearing Au-Ag deposits: Prasolovskoe and Ozernovskoe, both located within the Kuril-Kamchatka volcano-plutonic belt. Several rare and unknown Te and Se minerals were found at both deposits. At the Prasolovskoe deposit, various Te-Se minerals, including an unnamed Te3Se4 phase are widespread, while at the Ozernovskoe deposit selenides and sulfoselenides are typical. Te-Se mineralization at both deposits was formed in a rather narrow temperature interval (250200C); the composition of mineral assemblages was determined by activities of S2, O2, Te, and Se in the system. At early stages of ore-forming process, fluids were characterized by high aS2. With temperature decrease, aS2 also decreased, resulting in aTe2 increase, and, later aSe2 increase. That caused at first an abundant sulfides precipitation, then the formation of tellurides, followed by the crystallization of selenotellurides, and, finally, selenides.
Types of Tellurium Mineralization of Gold Deposits of the Aldan Shield (Southern Yakutia, Russia)
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Complex study and comparative analysis were carried out for two gold deposits, Vodorazdel'noe and Ondol'toi, localized among carbonate and siliceous-carbonate rocks of the Il'chir Formation in southeastern East Sayan. The Vodorazdel'noe deposit is of gold-quartz-sulfide type; it formed at 275-300 °C with the participation of highly concentrated chloride fluids and bears low-fineness gold associated with quartz-sulfide mineralization. In sulfur isotope composition (δ 34 S) the deposit ores are similar to sulfides of hydrothermal structures of slow-spreading ridges. The Ondol'toi deposit is formed by low-sulfide carbonate breccias and hematitized jasperoids. This deposit is localized in the frontal zone of a large thrust and bears gold-sulfide mineralization (fine-grained sulfides and submicron gold in siliceous-carbonate rocks and jasperoids). It is characterized by the presence of brecciated rocks and high contents of Hg, Sb, Ba, and Fe both in ores and in the host rocks. The established geologic, mineralogical, and geochemical features of the deposit permit it to be assigned to the Carlin type.
2000
We describe two epithermal telluride-selenide bearing Au-Ag deposits: Prasolovskoe and Ozernovskoe, both located within the Kuril-Kamchatka volcano-plutonic belt. Several rare and unknown Te and Se minerals were found at both deposits. At the Prasolovskoe deposit, various Te-Se minerals, including an unnamed Te3Se4 phase are widespread, while at the Ozernovskoe deposit selenides and sulfoselenides are typical. Te-Se mineralization at both deposits
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