Mineral Associations Research Articles

Characterisation of Fault-Related Mn-Fe Striae on the Timpa Della Manca Fault (Mercure Basin, Southern Apennines, Italy)

The Quaternary Mercure basin is a complex fault structure located in the Pollino region of the southern Apennines (Italy). A persistent seismic gap makes the Mercure basin structure one of Italy’s highest seismic risk zones. The southernmost termination of the Mercure basin is the Timpa della Manca fault. The fault’s mirror is characterised by distinctive, lineated, black-coloured striae decorating a cataclasite made of carbonate clasts. These black-coloured striae consist of a mixture of Mn phases, including hollandite, todorokite, birnessite, and orientite, which are associated with goethite and hematite along with minor amounts of phyllosilicates (chlorite, muscovite), quartz, and sursassite. This mineral association and their phase stability suggest that hydrothermal circulating fluids may have mobilised and re-precipitated low-temperature Mn hydrous phases within the shear zone, leaving remnants of higher-temperature minerals. Oceanic crust remnant blocks within the Frido Unit appear to be the most likely source of the Mn. The uniqueness of the Mn striae on the Timpa della Manca fault offers intriguing insights into fluid circulation within the Mercure basin tectonic system, with potential implications for the seismotectonic characteristics of the Pollino region.

Unusual mineralization in basaltic andesite of submarine volcano Esmeralda (Mariana Island Arc)

The results of studies of a basaltic andesite sample complicated by a mineralized crack and voids, with a crack and gas voids filled with secondary mineralization dredged on the Esmeralda underwater volcano, are presented. A detailed comparative study of the mineral composition of the substance lining the crack, the space around the crack, and the part of basaltic andesite unaffected by secondary changes made it possible for the first time for the underwater Esmeralda volcano to establish the presence of an association of minerals that is not characteristic of unaltered volcanic rocks. In the intracrack space and adjacent zones of basaltic andesite, wide ranges of plagioclase composition were determined, isomorphism in the Fe-Ca-pyroxene series was studied, REE oxides, hydroxides and fluorohydroxides were studied, and variability in the composition of minerals in the magnetite-hematite series was shown. It is assumed that tectonic movements led to the emergence of permeable zones in the previously formed basaltic andesites through which new portions of the melt leaked. In a limited space, high fluid gas saturation, temperature and pressure made it possible to extract metal compounds from the melt and host rocks.

Associations of minerals concentrates of gold in the Kukulkinja creek basin (Okhotsk region of Khabarovsk territory)

Associations of minerals concentrates of gold in the Kukulkinja creek basin (Okhotsk region of Khabarovsk territory)

Salinity increases under sea level rise strengthens the chemical protection of SOC in subtropical tidal marshes

The rise in sea levels due to global warming could significantly impact the soil organic carbon (SOC) pool in coastal tidal marshes by altering soil salinity and flooding conditions. However, the effects of these factors on SOC protection in coastal tidal marshes are not fully understood. In this study, we employed a space-for-time approach to investigate the variations in soil active carbon components and mineral-associated organic carbon under different salinity gradients (freshwater and brackish) and flooding frequencies (high and low tidal flats).The soil organic carbon (SOC) and easily oxidizable organic carbon (EOC) contents at the low-flooding frequency sites were higher than those at the high-flooding frequency sites. The dissolved organic carbon (DOC) content was higher at the high-salinity sites compared to the low-salinity sites, while the soil microbial biomass carbon (MBC) content was higher at the low-salinity sites than at the high-salinity sites. The EOC/SOC and DOC/SOC ratios were greater at the high-salinity sites than at the low-salinity sites, whereas the MBC/SOC ratios were higher at the low-salinity sites than at the high-salinity sites. Iron (Fe) and aluminum (Al) mineral-associated organic carbon [Fe(Al)-OC] and calcium-associated organic carbon (Ca-OC) contents were higher at the high-salinity sites compared to the low-salinity sites, and at the low-flooding frequency sites compared to the high-flooding frequency sites.Meanwhile, Fe(Al)-OC was the dominant fraction among mineral-associated organic carbon at all sites. The dominant phyla of bacterial community included Proteobacteria (49.31 %–66.36 %), Firmicutes (2.67 %–28.44 %), Chloroflexi (3.81 %–9.54 %), and Acidobacteria (4.28 %–7.02 %). In addition, Desulfobacca, a sulfate-reducing bacterium, promoted the formation of mineral-associated organic carbon.Random forest analysis showed that SOC and DOC were key factors in promoting mineral-associated organic carbon formation. Partial least squares path modeling (PLS-PM) indicated that sea level rise affects DOC content by altering soil physicochemical properties, promoting the formation of mineral-associated organic carbon.In summary, while soil organic carbon activity increases, the chemical association of minerals with organic carbon is becoming increasingly crucial for the protection of organic carbon under rising salinity conditions driven by sea level rise.

Wildcat strikes, the Industrial Workers of the World, and dual unionism: labor insurgencies in Pennsylvania’s anthracite region, 1900–1939

ABSTRACT The anthracite mineworkers of Northeastern Pennsylvania fomented a series of insurgencies during the first three decades of the twentieth century. This study focuses on their activism in the northern-most of three ‘hard coal’ fields, located around the cities of Wilkes-Barre and Scranton. Following several failed unionization attempts between 1848 and 1895, the United Mine Workers of America (UMAW) entered anthracite in the mid-1890s, organized the workforce, and called a successful strike in 1902. However, the discontent continued prompting the Industrial Workers of the World to enter the field in 1907. Drawing mainly on immigrant support, especially from the Italians, the ‘Wobblies’ suffered defeat in the Strikes of 1916 and left the area. The grassroots rebellions nevertheless persisted undere the Cmmunist-inspired National Miners Union between 1928 and 1931, the United Anthracite Miners of Pennsylvania between 1933 and 1934, and the Progressive Miners Association in 1939. The rear-guard actions ended during the post-World War II years and the decline of the industry. Through it all, the workers, who were originally British and German but by 1900 mainly Eastern and Southern Europeans, were motivated by grievances agaisnt the coal companies and the UMWA, and sustained by a deep well of family, community, and religous solidarity.

Combined study of Au-bearing arsenopyrite of orogenic gold deposits (NE Asia): High resolution 3D X-ray computed tomography, LA-ICP-MS, EMPA data

The distribution of gold in small acicular arsenopyrite of a pyrite-arsenopyrite association from Suzdal (Eastern Kazakhstan), Olympiada (Yenisei Ridge, Russia) and large pseudorhombic arsenopyrite crystals from Bazovskoe (Yakutia, Russia) orogenic-type deposits were investigated. On orogenic gold deposits in NE Asia, occurring mainly in black shales, two productive stages of ore deposition are distinguished, which correspond to two morphological varieties of arsenopyrite. At the early stage, fine-grained acicular-prismatic arsenopyrite with invisible gold was deposited; at the late stage, tabular arsenopyrite in association with free visible gold was formed. The samples of gold-bearing arsenopyrite were analyzed using Scanning Electron Microscopy, Electron Microprobe Analyses, Atomic Absorption and Laser Ablation Inductively Coupled Plasma Mass Spectrometry in combination with High Resolution 3D X-ray Computed Tomography (HRXCT). HRXCT does not destroy the studied mineral during the investigation. That technique permits to do an estimation of the amount of gold inclusions in minerals or host rocks and draw reasonable conclusions about the gold content of the ores, to study in detail the distribution patterns of metal inclusions (associated with certain minerals, cracks, crystal growth faces, etc.) and to determine the form of the gold. It can be used to understanding of the genesis of productive mineral associations, and to developing optimal technological schemes for gold extraction

40Ar/39Ar Dating of Hydrothermal Processes in Large Gold Deposits of the Kochkar Anticlinorium (South Urals, Russia)

The age restrictions for productive mineral associations of the two largest gold deposits of the Southern Urals—Svetlinsk and Kochkar, which are located in the East Uralian megazone—are discussed. The 40Ar/39Ar dating method was performed for the first time for potassium-containing hydrothermal minerals (micas and amphiboles) from the ore veins and ore-host alteration, as well as from marbles. The age estimates obtained are in the range of 290–276 Ma; the weighted average value for the Svetlinsk deposit is 276 ± 2 Ma; for the Kochkar field, 284 ± 2 Ma. It is supposed that the studied mineral assemblages of the Svetlinsk and Kochkar deposits were formed in the beginning of the postcollision stage corresponding to the tectonic relaxation regime. Age of hydrothermal mineral formation in the gold fields of the Kochkar anticlinorium are consistent with the time of post-tectonic plutonic activity, which was expressed in the Middle–Southern Urals in large-scale granitization (~300 Ma). The ore-bearing alteration of a femic profile (of the same age for two deposits), which are most likely basificates, are near-synchronous with the granitization.

Arsenopyrite from the Low-sulphidation Sedefche Au-Ag deposit, Eastern Rhodopes: Mineral Association and Gold Potential

The Sedefche Au-Ag deposit is located in the eastern Rhodopes, Bulgaria and is part of the Zvezdel-Pcheloyad ore field. The deposit is of low-sulphidation epithermal type, hosted in Oligocene highly silicificated intermediate volcanic tuffs, which lie above shallow marine sediments of organogenic limestones. The orebody has stratiform shape partly outcroping onto the surface. The ore mineralization is represented by small crystals and fine grained aggregates of sulphides (mainly pyrite, arsenopyrite, marcasite, chalcopyrite, galena, sphalerite) and associated sulphosalts (tetrahedrite, pyrargyrite, freibergite, and miargyrite) within matrix of quartz, formed in several stages of deposition. Gold in the deposit is detected in significant amounts in bulk ore samples, while native gold (a single < 1 μm gold nugget) and gold-bearing phases were sporadically discovered. The form of gold presence in the deposit is nevertheless debatable. Using combined SEM-EDS, EPMA and LA-ICP-MS approach, the highest concentrations of gold have been established in the arsenopyrite – the gold content there is up to hundredfold higher than in other ore minerals being potential concentrators of gold such as pyrite, marcasite and chalcopyrite. The presence of gold in arsenopyrite predominantly as nanoparticles, irregularly disseminated in the crystals as clusters of inclusions is suggested.

ПЕРВЫЕ СВЕДЕНИЯ О МЕДНОЙ МИНЕРАЛИЗАЦИИ РУДОПРОЯВЛЕНИЯ ШАРОМСКОЕ, ЦЕНТРАЛЬНАЯ КАМЧАТКА

The report provides new data on the mineralogy of the ores of the Sharomskoye copper ore occurrence, the Kirganik-Sharom ore zone in Central Kamchatka. Copper ores are confined to the central part of the submeridional massif of subalkaline metasomatites. Mineralization is disseminated, less often vein-disseminated in nature.The studied ore samples, collected during field works in 2023, are represented by silicified metasomatites with developed sulfide mineralization. Among the vein and accessory minerals are quartz, chlorite, barite and apatite. Ore minerals are represented by magnetite, chalcopyrite and bornite. Hematite and malachite are the most common supergene minerals, while cuprite and hydroxides of Fe and Cu are less common. The established chalcopyrite-bornite mineral association of the Sharomskoye ore occurrence is considered typical of other copper mineral prospects in central Kamchatka and is characteristic of porphyry copper deposits.

Geochemical and mineralogical assessment of environmentally sensitive elements in Neyveli lignite deposits, Cauvery Basin, India.

This research work presents an examination of the concentrations and modes of occurrence of environmentally sensitive elements within lignite deposits, located in Neyveli, within the Cauvery Basin of India. Coal is one of the most complex geologically formed materials, consisting of organic and inorganic matter. The inorganic mineral matter including thecrystalline minerals, non-crystalline mineraloids, and elements with non-mineral associations. These lignite samples underwent complete analysis encompassing macroscopic, microscopic and geochemical assessments. The analysis reveals that the total mineral matter (MM) content, comprising significant proportions of sulphides, carbonate and argillaceous components. Geochemical characterization further elucidates the lignite's properties, with proximate analysis yielding values such as ash, volatile matter and fixed carbon and the Ultimate components analysis reveals the carbon, hydrogen, nitrogen, sulphur and oxygen. Inorganic mineral matters play a significant role in coal utilization, and also such modes of occurrence of elements provide useful geochemical information on coal formation and coal-bearing basin evolution. In this paper, we assess the associations of elements and minerals, as well as the associations of selected elements including environmentally-sensitive (e.g., S, As, U, and Hg), and some major elements (e.g., Ca, Mg, Fe, Al, and Ti) that have largely occurred in non-mineral forms in these low-rank coals. And also, comparative analysis is conducted between the concentrations of elements within the lignite samples and the values reported for World Clarke Brown Coals (WCBC). Particularly, some of these elements exhibit significantly high environmental sensitivity, demanding careful consideration in lignite extraction and utilization practices.

Analysis of Spatial Association of Mineralization and Faults Through Fry and Fractal Modelling in Anarak Metallogenic Zone, Iran

Analysis of Spatial Association of Mineralization and Faults Through Fry and Fractal Modelling in Anarak Metallogenic Zone, Iran

Assessment of the age and conditions of metamorphism of high-pressure blastolites of the Gonzhinsky block of the Argun superterrane of the eastern part of the Central Asian folded belt

As a result of petrographic and thermobaric studies, 4 mineral associations were identified in the blastolite: relict, main, association corresponding to biotitisation and association of retrograde changes. The relict association probably represented eclogites The main mineral association corresponds to apoeclogite zoisite amphibolites. Determination of the P-T parameters of the formation of this association showed an interval of P = 13.0–15.0 kbar and T = 580-670 °C. At the same time, if we take the most ferruginous outer rim of amphibole-1 for calculations, then the P-T parameters shift to a higher temperature region of P = 13.0–17.0 kbar and T = 660-780 °C. The association corresponding to the imposed biotitisation is well structurally expressed. The lines of monomineral equilibria of the biotite association constructed from various combinations of garnet, biotite and plagioclase compositions showed good convergence in the local region corresponding to the interval P = 12.5-13.2 kbar and T = 810-830 °C. The last association of retrograde changes includes low-alumina amphibole-2.The association corresponding to the imposed biotitisation.ше is well structurally expressed. The last association of retrograde changes includes low-alumina amphibole-2. Based on the obtained isotopic data, a mineral Sm-Nd isochron was constructed for the rock, garnet and two amphiboles. The age of the isochron is 171 ± 3 million years, the latter is interpreted as the time of formation of the main mineral association and corresponds to its crystallization at the peak of metamorphism.

Evaluation of alteration in the geothermal province west of Cappadocia, Türkiye: Mineralogical, petrographical, geochemical, and remote sensing data

Abstract This study determines the mineralogical, petrographical, and geochemical properties of the rocks outcropping in geothermal areas west of the Cappadocia geothermal region. These areas include Ziga, Narlıgöl, Belisırma, Ilısu, and Sivrihisar. The study reveals their hydrothermal alteration characteristics. Also, the study aims to determine the zones of hydrothermal alterations using remote sensing. Rock samples from geothermal areas were performed using optical microscopy, X-ray diffraction (XRD), scanning electron microscopy, X-ray fluorescence spectroscopy, and inductively coupled plasma–mass spectrometry techniques for the determination of mineralogical assemblages and major, trace and REE's analyses. Rock samples, determined as ignimbrites and tuff, exhibit intensive alterations. XRD analysis determined the association of alteration minerals. The dominant clay minerals were kaolinite, montmorillonite, and illite. The analyses and mineral associations are compatible with argillic, mid-argillic alteration, and silicification zones. Alteration zones were identified by classifying the ASTER satellite images of kaolinite, illite, and montmorillonite using the CROSTA technique. The alteration zones observed in this study are close to existing geothermal areas. In addition, different regions with these alterations have been identified within the study area and are expected to be a valuable reference for future geothermal exploration.

Terrestrial input and biological processes drive varying mineral/organic matrix-related mercury sequestration and deposition in the East Siberian Arctic Shelf

Thawing Arctic permafrost is releasing massive amounts of terrestrial mercury (Hg) into the Arctic shelf, which is expected to form a Hg sink in sediments. Here we analyzed the coupling roles of terrestrial input and biological processes in varying mineral/organic matrix-related Hg sequestration and deposition on the East Siberian Arctic shelf (ESAS), using Pearson and partial correlation analysis. Results show that the occurrence of Hg in the Laptev Sea under the Lena River-dominated input exhibits strong correlations with the organic carbon (OC) content and sediment specific surface area. This indicates that the prolonged riverine loading processes facilitate Hg sequestration by organic/mineral matrices and these land-derived mineral-OC-Hg complexes remain stable during cross-shelf transportation. By contrast, the comparative samples with coastal erosion-dominated Hg input in the western East Siberian Sea shows limited Hg complexation, primarily due to the absence of regulation by riverine processes and/or the high sedimentation rates. The correlations between Hg and OC source proxies (δ13C and lignin) indicate that these matrix-free Hg could be more readily sequestrated by the marine OC, which facilitates its deposition via the biological pump. While unexpectedly low Hg abundance in the Chukchi Sea may indicate that the effective biological scavenging of Hg sequestration could be constrained by insufficient terrestrial Hg input. Our findings of the matrix-related Hg sequestration by mineral and/or OC association in this study may shed light on the biogeochemical cycle of Hg in the Arctic aquatic regime, which could reduce the methylmercury formation in water column, and the methylation within sediments needs further exploration.

Base-metal exploration by using remote sensing, geological, geophysical, and geochemical datasets with clues from ancient mining: A comprehensive review on Aravalli-Delhi Fold Belt, Rajasthan, India

Base metal deposits are present in different continents with evidences of their mining activities during ancient times as mentioned in the historical literature. Aravalli – Delhi Fold Belt (ADFB) in Rajasthan, India is having numerous base metal prospects where ancient mining signages are recorded. Modern-day mining has commenced taking clues from these evidences. Present-day techniques such as remote sensing, geological mapping, geophysical survey, geochemical survey, and exploration/drilling are utilized for the identification of surficial ancient mining features and identification of the mineralized zones. These techniques utilize their unique criteria to get an idea of the mineral association. The integration of all the unique characteristics of modern techniques with the help of weighted overlay analysis, fuzzy logic, multi-criteria overlay analysis, etc. helps to identify the mineral potential zones from the ancient working sites. Their integrated results provide the surficial as well as sub-surficial information of the region that gives a better revelation about the region and helps in decision-making towards the mineralization status of the region. World-over surficial ancient features have been recorded in exploratory sites for base metals, and the case histories where integrated techniques were used for mineral exploration are discussed. Zawar – Dungarpur belt also has the potential for base metals therefore, the boolean approach, weighted overlay, and multi-criteria overlay analysis were performed using remote sensing, structural, and geochemical datasets. The integrated results showed that the head zone and southern broader part near Keekawat have the potential for base metals.

Re-examination of vesbine in vanadate-rich sublimate-related associations of Vesuvius (Italy): Mineralogical features and origin

Abstract A set of 23 vesbine-bearing samples from Vesuvius volcano (Italy), preserved in the collection of the Royal Mineralogical Museum of Naples, University Federico II (RMMN), have been investigated to identify the mineral assemblages and their mode of formation. In the late 19th century, fumarole-related yellow patinas coating some historical lavas from Vesuvius were believed by Scacchi to contain a new element, vesbium, similar to vanadium in a mineral he called vesbine. Subsequent studies rejected vesbium and showed that vesbine was a poorly defined mixture of copper vanadates and halides. The vesbine samples studied here consist of yellowish to yellow-green-blue encrustations on Vesuvius lavas and have been analyzed by combined optical microscopy, SEM-EDS, XRPD, FTIR, and TEM-HRTEM-EDS. Results reveal complex mineral associations, including vanadates, halides, carbonates, oxides, silicates, tungstates/molybdates, and sulfates. The vanadates correspond to mottramite, volborthite, and vanadinite; subordinate amounts of descloizite were detected by XRPD and FTIR investigations. Several additional non-essential elements have been detected in the vanadates, including Mn, Zn, and As. The occurrence of wulfenite- and stolzite-rich phases indicates the presence of Mo and W, along with Pb, in the mineralizing fluids. Mn-rich phases, commonly in mixtures with silicates and vanadates, were also observed. These minerals are formed by a combination of different processes, including rock-fluid interactions, gas-water interactions, and alteration/oxidation of primary fumarolic minerals. Temperatures for the depositions of the vanadates-bearing assemblages are interpreted to be in the range of 100 to 400 °C.

The Yadovitaya fumarole, Tolbachik volcano: A comprehensive mineralogical and geochemical study and driving factors for mineral diversity

Active volcanic fumaroles are one of the most spectacular natural objects in terms of mineral diversity. The Great Tolbachik Fissure Eruption (GTFE) (Kamchatka) fumaroles are renowned for its exceptional number of mineral species. The total number of minerals that have been reliably identified from this particular locality exceeds 400, which is approximately 6.5 % of all known minerals to date. In this study, we employ a comprehensive approach (bulk chemistry, microprobe analysis, powder X-ray diffraction, HR X-ray computed tomography, and 34S, 18O, and 65Cu isotope measurements) to study the distribution of primary exhalation and secondary mineral assemblages and to reveal the driving factors responsible for the unique mineral diversity in the Yadovitaya fumarole. High oxygen fugacity, the interaction of minerals with atmospheric oxygen and water from seasonal precipitation (leading to abundant hydrated mineral associations), temperature conditions controlling the spatial distribution of mineral-forming components, gas-rock interactions, and basaltic scoria morphology perfect for the crystallization of various minerals are some of the factors revealed. The combination of these factors caused a stepwise mineralization resulting in 12 zones of the Yadovitaya fumarole with characteristic mineral assemblages. The described mineralogy of the Yadovitaya fumarole demonstrates a consistent spatial evolution of fumarolic mineral assemblages that vary in complexity, chemistry, and interaction patterns with the surrounding environment. The examination of mineralogical and geochemical data yields novel insights into the active volcanic systems that are associated with the formation of distinct oxidation-type fumaroles.

Karlleuite Ca2MnO4 – a first mineral with the Ruddlesden-Popper type structure from Bellerberg volcano, Germany

AbstractKarlleuite, ideally Ca2MnO4, is a newly approved accessory mineral found in the xenolith sample within the basaltic lava from the Caspar quarry, Bellerberg volcano, Eifel, Germany. It usually occurs as thin tabular/plate crystals, which range from 40 to 80 μm in diameter, and is associated with other members of the perovskite supergroup such as srebrodolskite, brownmillerite, sharyginite, perovskite, and lakargiite distributed within rock-forming minerals represented by reinhardbraunsite, fluorellestadite, fluorapatite, larnite, gehlenite, and several hydrated Ca aluminosilicates. Karlleuite crystals are brown with sub-metallic lustre, a light brown streak, and a good cleavage along (001). It is non-fluorescent, brittle and has an uneven fracture, a Mohs hardness of 3.5 and calculated density Dx = 3.79 g/cm3. The empirical formula of the holotype karlleuite calculated based on O = 4 atoms per formula is (Ca1.97Ce3+0.06)2.03(Mn4 + 0.39Ti0.36Fe3+0.19Al0.09)1.03O4, which shows that it is a multicomponent phase characterised by various substituents at the octahedral site. Karlleuite is tetragonal I4/mmm (no. 139), with a = 3.7683(2) Å, c = 11.9893(8) Å, V = 170.254(17) Å3, and Z = 2. The calculated strongest lines in the X-ray powder diffraction pattern are [d in Å (I) hkl]: 5.995 (43), 2.742 (100), 2.665 (91), 2.023 (25), 1.998 (28), 1.884 (61), 1.553 (38), 1.371 (24). The new mineral is the first natural phase which exhibits a first order of Ruddlesden-Popper type structure, which indicates a modular nature and consists of Ca(Mn, Ti, Fe, Al)O3 perovskite layers, packed between CaO rock-salt layers arranged along the c-axis. Raman spectroscopy supports the interpretation of the chemical and structural data. Mineral association, structural data, as well as the study of the synthetic Ca-Mn-O system suggest that karlleuite could form under high-temperature conditions, above 1000˚C.

The origin and mineralization processes of the Dulenggou copper-cobalt deposit in the East Kunlun orogenic belt, western China

The East Kunlun region in western China stands out as an important polymetallic metallogenic belt hosting economically significant Au, Cu, Fe, Pb, Zn, Sn, Co, Ni and Cr resources. Within this belt lies the Dulenggou deposit, a notable Cu-Co deposit. Three cobalt minerals (cobaltine, siegenite, and glaucodot) and four nickel minerals (ullmannite, gerdorffite, violarite, and millerite) coexisting with chalcopyrite and pyrite were identified in the Dulenggou deposit. The mineralization of Co and Ni primarily occurs in the form of sulfarsenides (cobaltine and gersdorffite) rather than sulfides (siegenite and ullmannite). Sulfides are commonly associated with chalcopyrite, whereas sulfarsenides coexist with chalcopyrite occasionally within the host rocks. The presence of organic-rich surrounding sedimentary rocks reduces oxygen fugacity, and the increase in arsenic content may influence the paragenetic association of minerals. The sequence of mineral formation is Py0 (host rocks) → PyI + Ccp + Co-Ni minerals (the major mineralization stage) → PyII. The mineralization age of the Dulenggou deposit has been determined by in situ U–Pb dating of hydrothermal monazite in closely association with chalcopyrite and Co–Ni minerals, yielding an age of 467 ± 17 Ma. The δ34S values of sulfides (pyrite and chalcopyrite) from ores and host rocks range widely from 1.9 ‰ to 22.1 ‰. From Py0 to PyI to PyII to chalcopyrite, the δ34S values change from 17.6 ‰ to 22.1 ‰, from 9.1 ‰ to 14.6 ‰, from 1.9 ‰ to 7.7 ‰, and from 9.6 ‰ to 13.4 ‰, respectively. The positive δ34S values suggest that the primary sulfur source possibly originated from seawater and/or the host rocks. Based on the geological and geochemical characteristics, the Dulenggou copper-cobalt deposit is identified as a syngenetic sea floor sedimentary exhalative deposit.

Mantle-plume model for the Zun-Kholba orogenic gold deposit (Eastern Sayan, Russia): results of mineralogical, Rb-Sr and <sup>40</sup>Ar-<sup>39</sup>Ar geochronological and Pb-Pb isotopic studies

The large Zun-Kholba deposit, belonging to a numerous group of orogenic-type gold deposits, is in the Eastern Sayan (Russia) – a segment of the Altai-Sayan fold system of the Central Asian Orogenic Belt. The paper discusses the results of mineralogical, geochemical, geochronological and Pb-isotopic studies of gold mineralization, the purpose of which was to verify the genetic model of the deposit. Mineralogical and geochemical data obtained for ore bodies located between hypsometric levels from 1290 to 2090 m indicate a complex distribution of mineral associations at the deposit. There is no vertical and horizontal zonation in the distribution of mineral associations, in the chemical composition of the main ore minerals, as well as in the content of impurity elements in them. In dating ore-forming processes at the Zun-Kholba deposit, a comprehensive approach based on the study of K-Ar and Rb-Sr isotope systems of metasomatites was applied. The combination of Rb-Sr and 40Ar-39Ar methods allowed us to determine that the age of gold mineralization is 411 ± 2 Ma, while the age of the superimposed event, which is associated with redistribution of ore, as well as disturbance of the Rb-Sr and K-Ar isotopic systems of metasomatites, is about 380 Ma. Pb-Pb isotopic study of ore mineralization at the deposit and host Precambrian rocks allowed to prove the leading contribution of the latter in ore lead supply to the mineral-forming system. The model of formation of the Zun-Kholba orogenic gold deposit assumes a genetic relationship between ore-forming processes and intraplate alkaline mafic magmatism due to the impact of the plume in the Early Devonian time on the lithosphere of the Tuva-Mongolian terrane.