The paper shows the genetic diversity of the structure and mineral composition of the ores of the Gorevsky Pb-Zn deposit, reveals the main signs of synchronous deposition of ore matter from near-bottom ore-bearing solutions associated with sedimentation processes in the sedimentary basin, considers textural and structural features and mineral associations of ores accompanying various metamorphism processes and postmagmatic processes. A model of the initially primary sedimentary-diagenetic origin of the ores of the Gorevsky Pb-Zn deposit under the conditions of catagenesis and the important role of the processes of redistribution and redeposition of the ore substance by interstitial solutions of the primary ore material is detailed. The study is based on the method of detailed study of the textural and structural features of ores in polished and polished samples. microstructural and mineral features and composition of ore and non-metallic minerals using modern methods of studying the substance. The bulk of the ores of the Gorevsky deposit demonstrate the textural and structural features of synsedimentary deposits, which are simultaneous with the host carbonaceous-micaceous-siliceous-carbonate rocks and retain these main structural features both at the macro and micro levels. The results obtained are compared and analyzed in comparison with other polymetallic deposits in Russia and in other regions of the world

We present new age constraints for igneous rocks and ore-metasomatic formations of the gold deposits in the Akzhal-Boko-Ashalin ore zone. In terms of their ore formation, these deposits correspond mainly to the orogenic type, which generally reflects specific metallogeny of the West Kalba gold-bearing belt in East Kazakhstan. Gold-quartz veins and mineralized zones of the gold-sulphide formation are confined to fractures feathering regional NW-striking and sublatitudinal faults. Their common features include the following: gold-bearing veinlet-disseminated pyrite-arsenopyrite ores that are localized in carbonaceous-sandy-schist and turbidite strata of different ages; structural-tectonic control of mineralization, numerous dikes of medium-basic compositions in ore-control zones; and the presence of post-orogenic heterochronous granite-granodiorite rocks, although their relation to gold-ore mineralization is not obvious. Igneous rocks of the study area have similar ages in a narrow range from 309.1±4.1 to 298.7±3.2 Ma, which is generally consistent with the previously determined age of granitoid massifs of gold-ore fields in East Kazakhstan. A younger age (292.9±1.3 to 296.7±1.6 Ma) is estimated for felsic rocks of the dyke complex. For the ore mineralization, the 40Ar/39Ar dating of sericite from near-ore metasomatites yields two age intervals, 300.4±3.4 Ma and 279.8±4.3 Ma. A gap between of the ages of the ore mineralization and the igneous rocks is almost 20 Ma, which may indicate that the processes of ore formation in the ore field continued in an impulse-like pattern for at least 20 Ma. Nevertheless, this confirms a relationship between the hydrothermal activity in the study area and the formation and evolution of silicic igneous rocks of the given age interval, which belong to the Kunush complex, according to previous studies. This interpretation is supported by reconstructed tectonic paleostress fields, showing that directions of the main normal stress axes changed during the ore mineralization stage, which is why the ore bodies significantly differ in their orientations. The above-mentioned data are the first age constraints for the study area. Additional age determinations are needed to further improve understanding of the chronology of ore-forming processes. Actually, all the features characterizing the gold mineralization of the Akzhal, Ashalin and Dauba ore fields, including the data on lithology, stratigraphy, structural tectonics, magmatism, isotope geochronology, mineralogy and geochemistry, can be used as criteria when searching for similar ore fields in East Kazakhstan.

—The Kultuminskoe deposit is located within the Gazimur metallogenic zone in eastern Transbaikalia. Mineralization is associated with the Middle–Upper Jurassic Kultuma pluton composed of subalkaline rock series ranging from quartz monzonites and quartz syenites to granites and of monzodiorite dikes. Dikes of Late Jurassic age are composed of subalkaline gabbro. Analysis of fractionation trends of major and trace elements suggests that the monzonitoids prevailed in the Kultuma pluton and the dike complex formed through the differentiation of subalkaline basaltic melt from an enriched mantle source. The formation of the gold–copper–iron–skarn and medium-temperature veinlet-disseminated polysulfide and epithermal Ag–Te–Bi mineralization as well as iron–magnesia and silica–alkaline meta-somatites was a long multistage process during the general evolution of the ore-magmatic system.

The supergene Au in weathering crusts of both the Suzdal and Raygorodok deposits is characterized by enhanced fineness, grain size, crystallinity, and the appearance of botryoidal aggregates of crystals. In the weathering crust of the Suzdal deposit, the exogenous Au is associated primarily with scorodite and carbonates; for Raygorodok, with chalcocite, bornite, hydrocarbonates and Cu hydrosulfates. The difference in the mineral associations of supergene Au at the deposits is determined by the occurrence of various mineral concentrators of Au in the primary endogenous substrate: arsenopyrite and pyrite at the Suzdal deposit and chalcopyrite with pyrite at the Raygorodok deposit. Due to the much greater mobility of Ag in the supergene zone, the weathering crusts are likely to contain submicron microinclusions of Ag minerals beyond the zones of Au concentration.

The Raigorodok stockwork gold-sulfide-quartz deposit is located in the contact zone of a monzogabbro-diorite intrusion belonging to the Stepnyak complex (442 Ma). Two main ore formation stages have been established: early, with disseminated gold-bearing pyrite-chalcopyrite mineralization related to skarn, propylite, and K-feldspar formation, and late, with productive mineralization. The late stage was accompanied by the formation of beresite, sericite, and quartz and comprised two substages: (1) quartz-gold-pyrite-chalcopyrite mineralization and (2) quartz-carbonate-gold-polysulfide mineralization. The 40Ar/39Ar ages of beresites and sericites are 422.9 +/- 4.3 Ma and 416.7 +/- 4.3 Ma, respectively, which is 19-22 Myr younger than the age of the host intrusion. The deposit ores formed stepwise, at temperatures of 112-335 degrees C and fluid salinity of 0.7-21.2 wt.% NaCl equiv. Sulfur for skarns, propylites, beresites, and ores might have been provided by a deep magma chamber, and the carbonaceous shales of the Vendian Sharyk Formation might have been the source of gold. The isotope and geochemical data and the results of fluid inclusion study suggest that Raigorodok is an intrusion-related deposit. At the same time, the deposit has a number of signs of porphyry-epithermal ore-magmatic systems. (C) 2018, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

Accessory zircon from the polyphase Raygorodok stock (Northern Kazakhstan) has been dated by local U–Pb analysis (SIMS and LA-ICP-MS). This Au-bearing intrusion has been dated to 442–447 Ma, suggesting its emplacement at the very end of the Ordovician and Early Silurian, allowing the stock’s correlation with the Stepnyak Complex of small intrusions. Thus, control of small intrusions of the Stepnyak type over gold mineralization has been corroborated permitting their use as a regional prospecting characteristic.

The Zhaima gold–sulfide deposit is located in the northwestern part of the West Kalba gold belt in eastern Kazakhstan. The mineralization is hosted in Lower Carboniferous volcanic and carbonate rocks formed under conditions of marginal-sea and island-arc volcanic activity. The paper considers the mineralogy and geochemistry of primary gold–sulfide ore and Au-bearing weathering crusts. Au-bearing arsenopyrite–pyrite mineralization formed during only one productive stage. Disseminated, stringer–disseminated, and massive rocks are enriched in Ti, Cr, V, Cu, and Ni, which correspond to the mafic profile of basement. The main ores minerals are represented by finely acicular arsenopyrite containing Au (up to few tens of ppm) and cubic and pentagonal dodecahedral pyrite with sporadic submicroscopic inclusions of native gold. The sulfur isotopic composition of sulfides is close to that of the meteoritic standard (δ34S =–0.2 to +0.2). The 40Ar/39Ar age of three sericite samples from ore veinlets corresponds to the Early Permian: 279 ± 3.3, 275.6 ± 2.9, and 272.2 ± 2.9 Ma. The mantle source of sulfur, ore geochemistry, and spatial compatibility of mineralization with basic dikes allow us to speak about the existence of deep fluid–magmatic systems apparently conjugate with the Tarim plume.

Обь-Зайсанская складчатая зона представляет собой фрагмент единой окраинно-континентальной структуры Сибирского континента, сложенной палеозойскими (преимущественно черносланцевыми) комплексами пород и характеризующейся однотипным магматизмом и общим набором рудных формаций. Вместе с тем, имеющиеся различия и определяют геологическую и металлогеническую специфику Иртышско-Зайсанского и Колывань-Томского фрагментов единой складчатой зоны. На месторождениях Западно-Калбинского и Колывань-Томского золотоносных поясов основная вкрапленная золото-сульфидная минерализация, контролируемая зонами динамометаморфизма и рассланцевания углеродисто-терригенно-карбонатных пород, формировалась в условиях тектонического сжатия в длительно развивающихся блоковых структурах. Сурьмяная минерализация характеризуется брекчиевыми текстурами и жильной морфологией тел, отражающими тектонический режим растяжения. На ряде месторождений (Жерек, Мираж, Дальнее) Sb-минерализация пространственно обособлена от золото-сульфидных руд, занимая секущее положение по отношению к основным рудоконтролирующим структурам. На других месторождениях антимонитовая минерализация совмещена с вкрапленными золото-сульфидными рудами c образованием микропарагенезисов Sb-содержащих минералов с Ni, Co, Au, Pb и Fe (месторождения Алимбет, Жанан, Легостаевское, Семилуженское, Каменское). В золото-сульфидных рудах месторождений прямой корреляционной связи между Au и Sb не устанавливается. В собственно антимонитовых жилах свободное золото при микроскопических исследованиях и на сканирующем электронном микроскопе не обнаруживается. По данным же атомно-абсорбционного и рентгеноспектрального анализов, в антимоните отмечается присутствие “невидимого” золота на уровне первых (до десятков) г/т. Повышенная золотоносность золото-сульфидных руд с наложенной сурьмяной минерализацией (месторождения Суздальское, Жанан, Легостаевское) связывается с процессами их регенерации и переотложения. Микроструктурные наблюдения, изотопно-геохронологические характеристики, минеральные парагенезисы и результаты изучения газово-жидких включений на золоторудных месторождениях Обь-Зайсанской зоны позволяют рассматривать сурьмяную минерализацию в рамках золото-полисульфидного этапа, который отделен от раннего продуктивного этапа формирования вкрапленных золотосодержащих пирит-арсенопиритовых руд временным интервалом в 30 млн лет. Cледует говорить о стадии антимонитовой минерализации, отделенной от собственно золото-полисульфидной минерализации внутриминерализационными тектоническим подвижками и временем в 7 млн лет. Установлены два основных этапа рудообразования: раннепермский (282–270 млн лет) и раннетриасовый (250–240 млн лет), которые могут быть связаны с эпохами мощнейшего внутриплитного магматизма, приведшими к формированию Таримской (280 млн лет) и Сибирской (250 млн лет) крупных магматических провинций. Эти глобальные геологические события, как правило, связывают с влиянием Таримского и Сибирского мантийных плюмов.

The Ob-Zaisan folded zone is a fragment of a single structure composed of Paleozoic sedimentary and volcanogenic rocks (mainly black shale), which was formed at the margin of the Siberian continent and features a common set of magmatic complexes and mineral systems. However, there are some differences that determine the specific geological and metallogenic features of the Irtysh-Zaisan and Kolyvan-Tomsk fragments of the Ob-Zaisan folded zone. In the gold deposits of the West Kalba and Kolyvan-Tomsk auriferous belt, the main gold-sulfide mineralization is controlled by zones of shearing and dynamic metamorphism in carbonaceous carbonate-terrigenous rocks. This type of mineralization was formed in tectonic blocks in a compressional setting. Antimony mineralization is characterized by brecciated textures and the vein-like morphology of ore bodies, reflecting extensional tectonics. At some deposits (Zherek, Mirazh, Dalny), Sb mineralization is spatially separated from the main gold-sulfide ores and shows cross-cutting relations to the principal ore-controlling structures. In other gold deposits, stibnite is spatially associated with disseminated gold-sulfide ores and forms mineral assemblages with Ni, Co, Au, Pb, and Fe (Alimbet, Zhanan, Legostaevskoe, Semiluzhenskoe, and Kamenskoe deposits). This study reveals no direct correlation between Au and Sb in gold-sulfide ores of these deposits. SEM analysis indicated the absence of free gold in stibnite veins. However, atomic absorption and electron microprobe analysis indicated the presence of “invisible gold” from a few ppm to several tens of ppm in the stibnite. High gold contents in the gold-sulfide ores overprinted by antimony mineralization (Suzdalskoe, Zhanan, and Legostaevskoe deposits) can be explained by the processes of regeneration and redeposition. The results of microstructural observations, isotope geochronology, studies of mineral assemblages and fluid inclusions in the ores from gold deposits of the Ob-Zaisan folded zone suggest that antimony mineralization was formed at gold-polysulfide stage, which was separated from the early ore pyrite-arsenopyrite stage by a 30 Ma time gap. It can be assumed that the essentially stibnite mineralization was formed at a separate stage and was separated from the gold-polysulfide mineralization by a 7 Ma interval of tectonic activity. Our Ar-Ar data on sericite from ore samples, combined with U-Pb data on zircons from igneous rocks and previous data from the literature show that there were two major stages of ore formation: the Early Permian (282-270 Ma) and the Early Triassic (250-240 Ma). Most researchers suggest that these stages of mineralization can be related to the epochs of intraplate magmatism that led to the formation of the Tarim (280 Ma) and Siberian (250 Ma) large igneous provinces. These global geological events are generally connected with the influence of Tarim and Siberian mantle plumes.

Acta Geologica Sinica - English EditionVolume 88, Issue s2 p. 773-774 Meeting Abstracts Antimony Mineralization at the Gold Deposits of the Ob-Zaysan Folded Zone (Southern Siberia and Western Kazakhstan). E.A. Naumov, Corresponding Author E.A. Naumov Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, 630090 Novosibirsk, Russia Novosibirsk State University, ul. Pirogova 2, 630090 Novosibirsk, RussiaCorresponding author. E-mail: naumov@igm.nsc.ruSearch for more papers by this authorYu. A. Kalinin, Yu. A. Kalinin Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, 630090 Novosibirsk, Russia Novosibirsk State University, ul. Pirogova 2, 630090 Novosibirsk, RussiaSearch for more papers by this authorK.R. Kovalev, K.R. Kovalev Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, 630090 Novosibirsk, RussiaSearch for more papers by this authorA.I. Antropova, A.I. Antropova Novosibirsk State University, ul. Pirogova 2, 630090 Novosibirsk, RussiaSearch for more papers by this author E.A. Naumov, Corresponding Author E.A. Naumov Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, 630090 Novosibirsk, Russia Novosibirsk State University, ul. Pirogova 2, 630090 Novosibirsk, RussiaCorresponding author. E-mail: naumov@igm.nsc.ruSearch for more papers by this authorYu. A. Kalinin, Yu. A. Kalinin Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, 630090 Novosibirsk, Russia Novosibirsk State University, ul. Pirogova 2, 630090 Novosibirsk, RussiaSearch for more papers by this authorK.R. Kovalev, K.R. Kovalev Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, 630090 Novosibirsk, RussiaSearch for more papers by this authorA.I. Antropova, A.I. Antropova Novosibirsk State University, ul. Pirogova 2, 630090 Novosibirsk, RussiaSearch for more papers by this author First published: 29 December 2014 https://doi.org/10.1111/1755-6724.12375_47Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume88, Issues2Special Issue: Meeting Abstracts: The 14th Quadrennial International Association on the Genesis of Ore Deposits Symposium. August 19–22, 2014, Kunming, ChinaDecember 2014Pages 773-774 RelatedInformation

Siberia is one of the largest in Russia in terms of production and reserves of gold. Large gold deposits, including the world-class ones, are localized here among the Precambrian metamorphic rocks. They belong to two different age types. The first vein gold-quartz type includes a number of deposits with average gold reserves (Eldorado, Ayakhta, Vasilevskoye and others), the largest of them is the Sovetskoye deposit. Ores are represented by low-sulfide quartz veins, vein zones and stockworks with pyrite, arsenopyrite and coarse gold. The second Au-As (± Sb) type is represented by voluminous deposits of disseminated ores of pyrite-arsenopyrite composition with a fine-grained gold in black shales. It includes such unique deposits as Olympiada and Blagodatnoye, as well as a number of large and medium-scale deposits such as Veduga, Poputninskoye, Titimukhta, Bogolyubovskoye, Panimbinskoye, and many others. A specific feature of this type deposits is the spatial coincidence of gold and antimony mineralization of different ages. The latter occurs at all deposits of this type and has commercial importance at the Olympiada and Uderey deposits. The most important and yet unsolved genetic problems of these deposits is determination of their age and relation to magmatism. The recent literature data (Sazonov et al, 2007; Vernikovsky et al, 2006, 2008; Nozhkin et al, 2008, 2011; Vrublevsky et al, 2011, etc.) and our results on the dating of rocks and gold mineralization (U-Pb, Ar-Ar and Re-Os methods) provide a new approach in solving these problems. The age of gold-quartz mineralization of the Sovetskoye deposit established by the newly formed sericite from the quartz-sericite-arsenopyrire (gold-arsenopyrite mineral assemblage) veinlet with native gold intersecting the early metamorphic quartz vein is 820.3 ± 8.2 Ma. The younger recovered high-grade coarse gold in pyrite-muscovite veins intersecting altered shales with arsenopyrite also occur at this deposit. The Ar-Ar age of muscovite from these veins is 775.8 ± 8.1 Ma. The similar age of the early quartz-sericite-arsenopyrite veins with native gold was also established at the Veduga gold deposit (805 ± 6.3 Ma). Based on the available published isotopicgeochronological data and the authors' dating (U-Pb, ArAr, and Re-Os methods) of rocks and ore mineral assemblages from the Olimpiada deposit, we propose the following chronology of Neoproterozoic metamorphic, magmatic, and ore-forming processes: 1) granitoids of the Teya complex: 976 ± 4.7 Ma (UPb); 2) granites of the Tyradinsky intrusion with which rare metal Mo-W mineralization is associated: 894.1 ± 4.7 Ma (U-Pb); 3) regional metamorphism and formation of associated pyrite-pyrrhotite mineral association: > 800-775 Ma (Likhanov et al, 2011, 2013); 4) intrusion of granitoids of the Ayakhta complex, contact metamorphism and associated pyrite-pyrrhotite mineralization: 760-750 Ma (Vernikovsky et al 2006, 2008); 5) mineral assemblages of gold mineralization: goldarsenopyrite, gold-polysulfide and berthierite antimonite, the time span of which is in the interval of 750-650 Ma; The time of formation of gold-arsenopyrite mineralization of the main stage (parageneses with acicular and elongated-prismatic arsenopyrite) have been established using Re-Os dating of the acicular arsenopyrite by isochron is 689 ± 28 Ma (Fig. 1) and close age (Ar-Ar) have the newly formed associating muscovite, which is compatible with the age of alkaline mafic rocks of the Borisenko А.S., Sazonov А.М., Nevolko P.A., Naumov Е.А., Tessalina S., Kovalev К.R. and Sukhorukov V.P., 2014. Gold Deposits of the Yenisei Ridge (Russia) and Age of Its Formation. Acta Geologica Sinica (English Edition), 88(supp. 2): 686-687.

In Eastern Kazakhstan, Sb mineralization is the most widespread in the Irtysh and Bakyrchik ore districts of the West Kalba gold-bearing belt. It is spatially related to disseminated gold-sulfide ores at some deposits and is structurally and spatially isolated at others. Disseminated gold-sulfide mineralization is localized in Carboniferous carbonaceous-terrigenous carbonate rocks. It is marked off by zones of dynamic metamorphism and foliation and is characterized by the ribbon-like-lenticular morphology of ore deposits. Later Sb (predominantly, quartz-antimonite) mineralization is formed in an extension setting as brecciated/veined ores. In combination with gold-sulfide ores, Sb mineralization is more diverse. For example, microparageneses with berthierite, native Sb, aurostibite, ullmannite, jamesonite, and tetrahedrite coexist with pocket-vein quartz-carbonate-antimonite mineralization in the gold-sulfide ores of the Suzdal'skoe deposit. Also, Sb-containing minerals such as arsenopyrite and pyrite are observed. Two temperature regimes of mineralization are established here: 418-300 degrees C for gold-polysulfide mineralization and 280-200 degrees C for later Sb mineralization. The isotopic composition of antimonite sulfur at the Suzdal'skoe, Zherek, Zhanan, Bakyrchik, and Dal'ny I deposits shows close values within the interval delta S-34 of -3.8 to 2.5%, suggesting its great-depth origin. No visible gold is found in the antimonite of the quartz-antimonite veins, but atomic-absorption analysis reveals few ppm or more gold. Point X-ray analysis indicates the possible presence of the so-called "invisible" gold. Microstructural observations, temporal relationships of the parageneses, and studies of gas-liquid inclusions at the Suzdal'skoe deposit permit assigning Sb mineralization to the second productive gold-polysulfide stage of the ore deposition. The late antimonite stage of mineralization is separated from the gold-polysulfide stage by 7 Myr long intramineralization tectonic shifts. Gold-polysulfide mineralization (248.3 +/- 3.4 Ma) was synchronous with Triassic tectonomagmatic activity. (C) 2014, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

The Suzdal gold-sulfide deposit is situated in the northwestern part of the West Kalba gold belt in Eastern Kazakhstan and belongs to the genetic type of stringer-disseminated mineralized zones hosted in the Lower Carboniferous black-shale volcanic-carbonate-terrigenous sequences. Mineralization is controlled by the NE-trending Suzdal Fault. In the north, the deposit borders on the Early Triassic Semeytau volcanic-plutonic structure. Mineralization is superposed on the Late Paleozoic complex of metadolerite and quartz porphyry dikes. Ore deposition was a long-term process comprising four stages. The first stage was related to deposition of slightly auriferous pyrite syngenetic to host rocks. The second stage is characterized by formation of the first productive (with invisible gold) fine-acicular arsenopyrite mineralization accompanied by sericitization and localized in the tectonic zone. The stockwork ore with pocket-disseminated base-metal mineralization and free microscopic gold of the third stage is hosted in silicified rocks. The ore formation has been completed by quartz-stibnite veins superposed on all preceding types of mineralization. According to Ar/Ar dating of sericite, a chronological gap between the second and the third stages is estimated at 33 Ma. The deposit is an example of polygenetic and multistage mineralization.

We have revealed early productive disseminated pyrite-arsenopyrite mineralization with invisible gold in tectonic zones and late nest-veinlet gold-polysulfide mineralization with free gold in zones of silicified rocks at the Suzdal’ (Suzdal’skoe), Zherek, and Bol’shevik deposits in eastern Kazakhstan, localized within black shales. Two varieties of arsenopyrite differing in morphology, chemical composition, and gold contents have been established in them: acicular-prismatic and tabular. Gold was determined by a specially elaborated technique ensuring a detection limit of 30 ppm Au. Acicular-prismatic arsenopyrite is the main ore mineral of the early productive stage of mineralization; it has high gold contents (1400–5360 ppm) and a nonstoichiometric composition (S/As = 1.2) and is slightly depleted in Fe. The absence of correlation between the contents of the main arsenopyrite components and gold, and the strongly uneven distribution of gold among the mineral grains, and within a grain point to the presence of invisible gold, as elemental particles deposited together with arsenopyrite. Tabular arsenopyrite is abundant at the Suzdal’ deposit, where gold-polysulfide mineralization and argillization are widespread. It has low gold and high antimony contents and a stoichiometric composition. Visible gold usually grows over tabular arsenopyrite. The isotopic composition of sulfur of acicular-prismatic arsenopyrite and globular-crystalline pyrite, formed at the early mineralization stages, is characterized by δ34S = 0.0 to –3.3‰ and evidences a mantle source of sulfur with a partial borrowing of crustal sulfur. The tabular arsenopyrite and other sulfides of the second productive mineralization show a lighter isotopic composition of sulfur (δ34S = –7.7 to –10.2‰), which is due to sulfur fractionation under high oxygen fugacity at the late ore deposition stage. The coexistence of two sets of arsenopyrite of different morphologic varieties and compositions at the deposit points to a long ore deposition, the coexistence of mineralization formed at different stages, and the evolution of physicochemical parameters.

A comparative analysis of morphology and geochemistry was made for gold from the primary ores and weathering crust of the Suzdal' gold deposit, Eastern Kazakhstan. The deposit is localized in Carboniferous carbonaceous-terrigenous strata and is of gold-sulfide type. Study of gold from primary ores showed that it occurs mainly in two species: free and so-called invisible. Free gold is crystallomorphic segregations and irregular-shaped grains up to tens of microns in size; it occurs in intergrowths with sulfides, quartz, carbonate, and mica-chlorite aggregate. Most of gold particles have a fineness of 930-980%, with some grains showing wide variations in composition. Invisible gold ( probably chemically combined) is present in fine-acicular arsenopyrite and, less frequently, pyrite.Being transported to the weathering crust, all this gold served as a source for "neogenic" gold of diverse morphologic forms. We recognized crystalline ( isometric, prismatic, acicular, and tabular) particles and drusoid gold aggregates in the form of exotic intergrowths of crystallomorphic and sinter-shelly grains. The grains tend to coarsen from bottom to top of the weathering crust. Several generations of gold of different granulometric classes are observed. We have revealed seed and layer growth and dissolution structures in crystals of early generations overgrown with fine grains. All these gold varieties are associated with hypergene minerals. Most of this gold is of high fineness (on the average, 995%). The hypergene gold particles are chemically homogeneous high-grade, without rims.The results of studies suggest that the high-grade hypergene gold formed in the weathering crust as a result of the dissolution of invisible gold of sulfides and its local redistribution and deposition in oxidizing media. This is also evidenced from the tendency of gold to coarsen from bottom to top of the weathering crust. A distinctive feature of secondary gold is well-expressed crystals and their great diversity. (C) 2009, IGM, Siberian Branch of the RAS. Published by Elsevier B. V. All rights reserved.

The Suzdal gold deposit is located in the Western Kalba gold Ore belt, Eastern Kazakhstan. The mineralization is confined to the NE-trending tectonic zone that crosscuts Early Carboniferous carbonaceous Carbonate and terrigenous clastic rocks. The Suzdal ore system consists of a primary ore zone overlain by an Au-bearing weathering Crust, now mined out. The primary ore zone has a low sulfide content (0.5 to 15 vol.%) and contains both visible and invisible gold. Three main ore types and host rocks are recognized: I) sulfidized bedded carbonaceous sandstone and turbidite-facies siltstone; 2) partly silicified calcareous breccia and carbonaceous sedimentary rock with disseminated sulfides; and 3) strongly silicified brecciated rock. On the basis of the geological, mineralogical, and geochemical data we suggest that the Suzdal deposit was formed by multistage processes. All these processes were accompanied by redistribution of the earlier deposited sulfides and gold and the development of higher grade gold mineralization. Ar-40/Ar-39 dating of hydrothermal sericite yielded ages of 281.9 +/- 3.3 Ma and 248.3 +/- 3.4 Ma, bracketing the timing of the mineralization between the Early Carboniferous and Early Triassic.The Suzdal ore system has some similarities with Carlin-type mineralization, but differs from Carlin deposits by the presence of gold-bearing arsenopyrite and native gold, the low As-content in pyrite, absence of realgar and orpiment, and low contents of Hg and TI. (C) 2008 Elsevier B.V. All rights reserved.

The Suzdal gold-sulphide deposit, characterized by fine gold hosted in Carboniferous-aged carbonaceous-terrigeneous-carbonate lithologies, is located in the Kalba gold-bearing belt in the eastern Kazakhstan. Three types of mineralized rocks are distinguished: 1) sedimentary and melange calcareous breccias, 2) silicified tectonic breccias of sulphidized carbonaceous-terrigeneous rocks, and 3) sulphidized sandstones and carbonaceous siltstones. The first two types contain native gold. The third one contains invisible gold, which occurs preferentially in stellar-aggregated arsenopyrite and is chemically bonded.

The high gold potential of Cu-ore (Cu-skarn, porphyry Cu-Mo, and pyrite-polymetallic) deposits widespread in the Altai-Sayan folded area is shown. The ore formation processes at these deposits included multistage mineralization with the gradually decreasing temperature of ore-forming solutions. At the early high-temperature stages, mainly the profile ores (often, of zonal structure) of the deposits were produced. Their mineral composition is closely related to the composition of the corresponding ore-magmatic system and is regularly repeated in ore objects of different sizes and ages. At the final stages, low-temperature mineral assemblages formed, which often have a similar set of ore and vein minerals. A distinctive feature of these assemblages is the presence of Ag, Pb, and Au tellurides, Bi minerals, native bismuth, and Hg-containing minerals. Gold in the minerals is of varying fineness; the main trace elements in it are Ag and Hg. The low-temperature mineral assemblages are close to ores of epithermal deposits (including Carlin-type ones) developed in the same areas. These ores might be the products of the final-stage evolution of the ore-magmatic systems.