The distribution of trace elements in sulfdes from various ores of the Aktash magnetite-polymetallic deposit (Tajikistan) is studied using LA-ICP-MS method. Sulfdes partly replace banded magnetite ores. Each sulfde type exhibits specifc geochemical features. Galena from sulfde-magnetite ores contains the higher amount of elements of «high-temperature» association (Bi, Ag, Cu) than galena from pyroxene-sphalerite ores, which, in addition to Ag and Bi, also contains higher amount of elements of «medium-temperature» association (Se, Te, and Sb). Sphalerite from sulfde-magnetite and chlorite-pyrrhotite ores contains higher Fe, Cd and Mn amount than sphalerite from pyroxene-sphalerite ores, which is characterized by elevated Co and As contents. Pyrite is depleted in trace elements except for As, the content of which is maximum compared to other sulfdes. The Ag, Se, Bi, Zn, Cd and Ni contents of chalcopyrite from chlorite-pyrrhotite ores are higher than in chalcopyrite from sulfde-magnetite and pyroxene-sphalerite ores. Chalcopyrite from pyroxene-sphalerite ores is characterized by elevated Pb, As, Ge, Te and Sb contents. Relatively high Co, Ni and Se contents are determined in pyrrhotite. In addition to Fe, Cu, Zn, Pb and Au, which form minerals in all types of ores, we suggest by-product extraction of following elements from complex sulfde-magnetite, chlorite-pyrrhotite and pyroxene-sphalerite ores (the Bi, Ag, Se and Te contents of galena and Cd content of sphalerite are shown in brackets): Bi (19520–24650 ppm), Ag (7907–9650 ppm), Se (397–606 ppm) and Te (276– 436 ppm) from galena concentrate and Cd (8525–27670 ppm) from sphalerite concentrate.

The article reports on the presence of minerals of the crichtonite group (MCG) in ooids of mineralized volcaniclastic rocks of the Rudnogorskoe iron deposit (Eastern Siberia). The ooids are characterized by a concentric-zoned structure of detrital component, expressed in a sequential change of hematite-smectite core -> smectite-chlorite -> chlorite-garnet -> apatite-chlorite zones, which are rimmed by thin-layered magnetite. Rare crystalline MCG aggregates in ooids are found in the peripheral apatite-chlorite zone. Based on the chemical composition and Raman spectra, the MCG are identified as crichtonite and davidite-Ce. The following components are determined in the composition of crichtonite, wt.%: TiO2 63.73-70.69, FeO 18.03-23.58, SrO 2.24-4.03, CaO 2.22-4.10, MgO 0.33-1.02, Al2O3 up to 2.01, MnO up to 0.54 and Ce2O3 up to 1.88. Davidite-Ce typically occurs along the edges of crichtonite and contains, wt.%: TiO2 60.54-62.28, FeO 22.67-25.77, Ce2O3 3.18-5.0, La2O3 2.47-2.74 and SrO 0.58-0.64. The MCG also contain up to 4.69 wt.% UO2. Complex processes of breakdown of MCG and their replacement by anatase are accompanied by the formation of REE (anzaite-Ce) and U (uraninite) minerals and subsequent transformation of anatase to rutile. A sequence of mineral formation of the ooids indicates that the formation and growth of the MCG crystals is a result of lithification of accumulated Ti and trace elements during smectitization of basaltic clasts. Further processes of mineral transformation are associated with the transformation of crichtonite to simple Ti oxides and the precipitation of REE and U minerals. Titanite is a product of the final skarn stages of ore formation.

Research subject . The horizons of ferruginous sedimentary rocks in the massive sulfide deposits of the Urals. Aim . To estimate the Ti behavior upon halmyrolytic transformation and lithogenesis of calcareous hyaloclastites and carbonatesulfide-hyaloclastite sediments. Materials and methods . Microtextures of authigenic aggregates of Ti minerals (anatase, rutile, titanite) in jasperites and gossanites of various Urals massive sulfide deposits were studied. The minerals were identified using microscopic and electron microscopic methods, as well as electron back-scattered diffraction. Results . Upon partial halmyrolysis of calcareous hyaloclastites, Ti was removed with the formation of authigenic anatase rims around hematitized hyaloclasts. The full transformation of hyaloclastites to hematite-quartz jasperites resulted in decomposition of authigenic Ti minerals. Authigenic rutile and titanite formed in gossanites (hematite-quartz and hematite-chlorite products of submarine oxidation of calcareous sulfide-hyaloclastite sediments). The occurrence of abundant bacteriomorphic structures in corroded hyaloclasts indicates a significant role of bacteria in halmyrolysis. Conclusions . Titanium for the formation of Ti minerals in ferruginous sediments was sourced from hyaloclastites. The halmyrolysis of calcareous hyaloclastite sediments and related formation of jasperites occurred under alkaline conditions favorable for the transportation of Ti in the form of hydroxycarbonate complexes. The formation of rutile instead of anatase was associated with lower pH values (<5) due to oxidation of pyrite in sulfide-bearing hyaloclastite sediments. Titanite formed as a result of further alteration of Ti-bearing phases. Our results solve the fundamental problem of Ti mobility during halmyrolysis of hyaloclastites, which contradicts its commonly accepted immobility in hydrothermal processes.

This study concerns the transformed clastic ores (ore diagenites) of the Ishkinino Co-bearing massive sulfide deposit hosted by serpentinites of the Main Uralian Fault Zone. The structures and textures of ores are studied, the trace element (TE) contents of sulfides and oxides are determined using laser ablation inductively coupled plasma (LA-ICP-MS), and physicochemical modeling of diagenetic formation of accessory As minerals is conducted in the Selector program. The clastic ores are transformed gravelites with angular and rounded clasts of serpentinites, sulfides and chromite in psammitic matrix of the same mineral composition. No hydrothermal minerals remain in gravelites; they are replaced by crystalline pyrite-2, porous pyrite-3, anhedral pyrite-4, pyrrhotite, chalcopyrite, and magnetite. Chalcopyrite and magnetite replace all sulfides, sulfoarsenides, chromite, and gangue minerals. Chromite occurs as fragmented crystals or is included into serpentinite clasts. The matrix hosts euhedral cobaltite crystals with nickeline, gersdorffite, and native gold inclusions. Crystalline pyrite-2 is characterized by higher Mn, Co, Ni, Cu, and Zn contents. Porous pyrite-3 has higher Co, Cu, and Se contents. Anhedral pyrite-4 is enriched in most TEs in comparison with other sulfides and pyrite generations. Chalcopyrite is characterized by higher contents of Zn and Se. Pyrrhotite contains the highest Ni and higher Co contents. The main TEs in ores of the deposit (Co and Ni), as well as Cu, Zn, and Mn, are hosted not only in sulfides but also in oxides: chromite contains Zn and Ni and magnetite contains Mn and Cu. The Se contents of all sulfides are similar. Tellurium is mostly concentrated in pyrite-4. Comparative analysis with results of studies of other massive sulfide deposits shows that the serpentinite–sulfide gravelites of the Ishkinino deposit are intensely transformed during diagenesis that resulted in low TE contents in diagenetic sulfides. The diagenetic alteration of clastic ores led to the formation of authigenic cobaltite, gersdorffite, nickeline and native gold as a result of TE release from primary hydrothermal minerals. The thermodynamic modeling showed a possibility of formation of As-bearing minerals (in particular, nickeline) at temperatures of 200°C and below.

Halmyrolysis, as one of the global processes of alteration of seafloor hydrothermal sediments, needs to be recognized in terms of mineral and trace element evolution to elaborate new criteria for metallogenic and geoecological forecasts with respect to ocean exploration. The purpose of this paper is to explain trace elements’ behavior during the halmyrolysis of sulfide deposits. This task is resolved using an LA-ICP-MS analysis of iron oxyhydroxides (IOHs) on examples of oxidized pyrrhotite-rich diffusers of the ultramafic-hosted Pobeda-1 hydrothermal field (Mid-Atlantic Ridge). The IOHs formed after the sulfides were enriched in seawater-derived trace elements (Na, K, Mg, Ca, Sr, P, U, Mo, V, REE, Cr). Six trace element assemblages (TEAs) are statistically recognized for the IOHs. TEA-I (Cu, In, Sn, Bi, Se, Te) is inherited from chalcopyrite, isocubanine and bornite microinclusions. TEA-II is typical of Zn sulfides (Zn, Cd, Sb, Tl, Ag) interacted with seawater (Mg, U, Mo, Ni, Na, K) and hydrothermal fluid (Eu). TEA-III (Ca, Sr, Cu, Si, Se, P, As) reflects the inclusions of aragonite, opal, atacamite and possibly native selenium, while P and As occur as absorbed oxyanion groups on IOHs or Ca–Fe hydroxyphosphates. TEA-IV (Al, Ga, Ge, Tl, W, Ti ± Mn, Co, Ba) indicates the presence of minor clays, Co-rich Mn oxyhydroxides and barite. TEA-V with Pb and V is closely related to TEA-VI with REEs except for Eu. The halmyrolysis of sulfides includes two stages: (i) oxidation of S(II) of primary sulfides and the formation of supergene sulfides, which scavenge the redox-sensitive elements (e.g., U, Mo, Ni, Eu), and (ii) oxidation of Fe (II) to Fe (III) and absorption of most elements of TEAs III, IV, V and VI by IOHs.

The article describes magnetite–sulfide assemblages of minerals containing native gold and tellurides in the Pb–Zn–Fe ores of the Aktash skarn deposit in Western Karamazar (Tajikistan). Gold–silver–telluride mineralization is represented by products of a multistage ore process. It has been established that native gold is concentrated both in magnetite and in association with sulfide minerals. A decrease in the fineness of native gold from its early to late varieties was revealed: 725–905‰ in magnetite → 656–699‰ in pyrite-pyrrhotite ores → up to 290‰ in association with galena and bismuth-bearing minerals. The regular decrease in the fineness of native gold and paragenetic relationship with various bismuth minerals (native bismuth, bismuthite, aikinite, Ag–bearing aikinite, uytenbogaardtite, Ag–Au–Bi–S phases) reflect a decrease in temperature and sulfur fugacity of mineral-forming fluids. Tellurides are found in magnetite-chalcopyrite-pyrite-pyrrhotite ores and are represented by tsumoite, pilsenite, hessite and stützite. Electron backscatter diffraction (EBSD) patterns of tsumoite and pilsenite confirmed the predominant presence of tsumoite in the ores.

Diagenetically altered thin-layered sulfide ores from the Talgan volcanic-hosted massive sulfide deposit (South Urals) represent an intercalation of thin sulfide , hyaloclastite layers up to 3 and 0.5 cm thick. Their mineralogy and trace element, including rare earth elements (REE) , S, C and O isotopic geochemistry are considered in this work. They occur at the slopes of ore bodies and pinch outside them within hyaloclastites and their thickness increases towards the flanks of the ore bodies. The sulfide layers are mostly composed of authigenic pyrite, which forms zoned nodules, anhedral aggregates, euhedral crystals and pseudomorphs after pyrrhotite crystals. The pyrite nodules and anhedral aggregates host inclusions of authigenic chalcopyrite, sphalerite, galena, barite, cotunnite, native gold, stromeyerite, tellurobismutite and hessite. The trace element content of sulfide layers widely varies and depends on the amount of non-sulfide minerals (chlorite, illite, calcite, quartz, rutile, scheelite), which formed as a result of alteration of dacitic hyaloclastite components mixed with sulfide clasts. The sulfide layers are enriched in REEs (up to 561 ppm) due to the presence of REE-bearing minerals (bastnaesite, parisite, synchysite, galgenbergite, REE-bearing xenotime), which do not occur in massive sulfide ores. A narrow range of delta S-34 values of pyrite (1.41-3.27 %o) from sulfide layers is explained by equilibrium or kinetic dissolution-precipitation processes of redeposition of sulfide ore clasts during diagenetic processes. The delta 13C values of bulk samples of sulfide layers (-5.29 to -17.89 %o) indicate that the authigenic carbonates formed from pore fluids circulated in former organic-rich hyaloclastite layers. The delta O-18 values of the same samples (+4.00 to + 8.36 %o) are higher compared to seawater delta O-18 values due to diagenetic isotopic exchange between the hyaloclastitic components and pore fluids at elevated temperatures of burial process. The positive delta S-34-Mn, delta C-Mn, delta C-13-As, delta C-13-Sb, delta O-18-Mn and delta 18O-U correlations reflect organic matter con-sumption during the evolution of authigenic minerals. Data presented in this study helps to define the origin of diagenetically altered layered sulfide ores in volcanic-hosted massive sulfide deposits and are important for understanding diagenetic REE accumulations in sulfide-rich sediments of these deposits.

Symbioses between metazoans and microbes involved in sulfur cycling are integral to the ability of animals to thrive within deep-sea hydrothermal vent environments; the development of such interactions is regarded as a key adaptation in enabling animals to successfully colonize vents. Microbes often colonize the surfaces of vent animals and, remarkably, these associations can also be observed intricately preserved by pyrite in the fossil record of vent environments, stretching back to the lower Paleozoic (Ordovician-early Silurian). In non-vent environments, sulfur isotopes are often employed to investigate the metabolic strategies of both modern and fossil organisms, as certain metabolic pathways of microbes, notably sulfate reduction, can produce large sulfur isotope fractionations. However, the sulfur isotopes of vent fossils, both ancient and recently mineralized, have seldom been explored, and it is not known if the pyrite-preserved vent organisms might also preserve potential signatures of their metabolisms. Here, we use high-resolution secondary ion mass spectrometry (SIMS) to investigate the sulfur isotopes of pyrites from recently mineralized and Ordovician-early Silurian tubeworm fossils with associated microbial fossils. Our results demonstrate that pyrites containing microbial fossils consistently have significantly more negative δ34 S values compared with nearby non-fossiliferous pyrites, and thus represent the first indication that the presence of microbial sulfur-cycling communities active at the time of pyrite formation influenced the sulfur isotope signatures of pyrite at hydrothermal vents. The observed depletions in δ34 S are generally small in magnitude and are perhaps best explained by sulfur isotope fractionation through a combination of sulfur-cycling processes carried out by vent microbes. These results highlight the potential for using sulfur isotopes to explore biological functional relationships within fossil vent communities, and to enhance understanding of how microbial and animal life has co-evolved to colonize vents throughout geological time.

Актуальность. В последние годы, благодаря появлению масс-спектрометрии с индуктивно-связанной плазмой и лазерной абляцией, возрос интерес к изучению состава магнетита как индикатора условий формирования железорудных месторождений. Применение масс-спектрометрии с индуктивно-связанной плазмой и лазерной абляцией для изучения магнетита особенно актуально в Западном Карамазаре, где сохранились магнетитовые месторождения, несущие полиметаллическую минерализацию. Несмотря на то, что стадийность магнетитовых месторождений изучалась многими исследователями, предложенные модели их формирования остаются до сих пор дискуссионными. Для решения этой проблемы нами изучены текстурно-структурные особенности магнетитовых руд и состав элементов-примесей (на 32 элемента) выделенных разновидностей магнетита. Цель: получить новые минералого-геохимические данные по разновидностям магнетита для развития модели эволюции железных руд акташского типа. Объектами исследования являются восемь разновидностей магнетита сульфидно-магнетитовых рудных тел месторождения Акташ Кансайского рудного поля Западного Карамазара, расположенного в северной части Республики Таджикистан. Методы. Минеральный состав руд изучен в аншлифах с помощью оптического микроскопа Olympus BX51 с цифровой фотокамерой Olympus DP12. Диагностика минералов проводилась на растровом электронном микроскопе Tescan Vega 3 sbu (Институт минералогии ЮУ ФНЦ МиГ УрО РАН). Содержания элементов-примесей в магнетите определялись методом масс-спектрометрии с индуктивно-связанной плазмой и лазерной абляцией на масс-спектрометре Agilent 7700x с программным комплексом MassHunter и лазерным пробоотборником New Wave Research UP-213 (ИМин ЮУ ФНЦ МиГ УрО РАН). Для градуировки и расчета использовались международные стандарты: стекла USGS NIST-610 и USGS GSD-1g. Расчёт проводился в программе Iolite c использованием 56Fe в качестве внутреннего стандарта. Результаты. На месторождении Акташ магнетит представлен следующими морфогенетическими разновидностями: обломковидные (Mt-1h), дендритовидные (Mt-1d), нитчатые (волокнистые) (Mt-1f), радиально-лучистые (Mt-1r) и колломорфно-почковидные (Mt-1c) агрегаты магнетита-1, зональные субгедральные зерна магнетита-2 (Mt-2s), удлиненные пластинчатые кристаллы магнетита-3 («мушкетовит», Mt-3m) и незональные эвгедральные метакристаллы магнетита-4 (Mt-4e). Предполагается, что разновидности магнетита-1 образовались на стадиях гальмиролиза и диагенеза известковистых вулканогенно-осадочных отложений в зонах газовых просачиваний и бактериального хемосинтеза. Обломковидная и колломорфно-почковидная разновидности магнетита образовались по гиалокластам, дендритовидные, нитчатые и радиально-лучистые – по биоморфным структурам. Реликтовые включения алюмосиликатов и акцессорных минералов в апогиалокластитовом магнетите (Mt-1h) фиксируются по повышенным содержаниям Mg, Ti, Al, Zr, Cr и V относительно таковых в бактериморфном магнетите (Mt-1d, 1f, 1r) при близких количествах As. Для раннедиагенетических разновидностей магнетита-1 (Mt-1d, 1f, 1c, 1r) характерны повышенные содержания As, Sb, Mo и W при низких Al, Ti, V, Cr, Mn, Ni, Zn по сравнению с зональными субгедральными зернами магнетита-2s и эвгедральными кристаллами магнетита-4e. В стадию позднего диагенеза ранние агрегаты магнетита-1f, c, r обрастали зональными кристаллами магнетита-2s. Магнетит-2s характеризуется самыми низкими содержаниями As, Sb, Mo и W. Магнетит-3m, образовавшийся по кристаллам гематита, подобно гематиту, концентрирует W, Zn и Mo. Магнетит-4e, в состав которого изоморфно входят максимальные количества Ti, V, Cr, Mn, Zn, при минимальных содержаниях Mo, свидетельствует об образовании его при высоких температурах.

The chemistry of pyrite represents a potentially promising new frontier for the research and exploration of different types of ore deposits [...]

Hydrothermal vents are among the most fascinating environments that exist within the modern oceans, being home to highly productive communities of specially-adapted fauna, supported by chemical energy emanating from the Earth's subsurface. As hydrothermal vents have been a feature our planet since the Hadean, their history is intricately weaved into that of life on Earth. Despite an overall scant fossil record due to the improbabilities of preservation of vent deposits and organisms, recent fossil findings from ancient vent environments, accompanied by molecular data as well as fossils from ecologically-similar environments, have yielded invaluable new insights into the history of life at hydrothermal vents. Fossils from hydrothermal vents are among the earliest contenders for direct evidence of life on Earth, while a range of additional fossil finds indicate that vent habitats were readily exploited by microbes during the Precambrian. The first metazoans possibly appeared within vents during the Cambrian, and by the Ordovician-Silurian, hydrothermal vents in the deep ocean were colonised by mollusc, brachiopod and tubeworm taxa whose large abundances and sizes suggest these early animals were well-adapted to this setting. A transition in vent community composition occurred during the Mesozoic, as modern vent faunas began to occupy these environments and replace Paleozoic taxa. Molecular evidence indicates that many additional taxa radiated within vents during the Cenozoic, demonstrating that throughout Earth history, organisms were repeatedly able to overcome the challenges of adapting to the harsh conditions at vents to exploit their productivity. Targeting ancient vent deposits that have undergone low degrees of diagenetic or metamorphic change during mining-related exposure has great potential to provide further insights into the vent fossil record and fill existing gaps in knowledge.

The Garmab-e-Paein Cu-Ag volcanogenic massive sulfide (VMS) deposit occurs as stratiform and stratabound orebody within a specific stratigraphic horizon in a Late Cretaceous volcano-sedimentary sequence of the Sabzevar zone, northeast Iran. The host rocks to mineralization are andesitic-trachyandesitic volcanic and volcaniclastic rocks. Based on textural and mineralogical studies, the VMS mineralization is comprised of four ore facies: 1) vein-veinlets (stringer) containing chalcopyrite, pyrite and minor magnetite, 2) massive ore, dominated by pyrite and minor chalcopyrite, 3) bedded ore containing laminated pyrite, and 4) exhalite containing Fe-Mn oxide-hydroxides such as hematite, psilomelane and pyrolusite. Wall rock alteration styles are chloritic, minor silicic and secondary argillic. There is a distinct metal zonation in the massive sulfide orebody; Au, Pb, As, and Ag contents and the Cu/Zn ratio increase vertically from the stringer to the massive facies, but decrease laterally from the stringer to the bedded facies. Zinc and Mn increase from the stringer to the bedded ore facies. Sulfur isotope values for pyrite range from -1.7 to +5.1%o, with average +1.4%o. The delta 34S values of massive ore facies (-1.7 and +2.7%o) increase downward toward the stockwork (+2.2 to +4.3%o) and laterally outward toward the bedded (+5.1%o) zones. The near-zero sulfur isotope values indicate that most of the sulfur was derived from leaching of underlying host volcanic rocks by hydrothermal fluids circulating in the high temperature reaction zone. Extensive disseminations and vein-veinlets of native copper mineralization formed within the hanging wall Late Cretaceous volcanic rocks and younger Paleocene conglomerates. The native copper mineralization is accompanied by chlorite and zeolite alteration, and both formed after formation of the Garmab-e-Paein VMS deposit during diagenesis, burial metamorphism and uplift. The deposit is now potentially economic due to the native copper mineralization. Two generations of chlorite are observed in the deposit: Chl-I is accompanied pyrite and chalcopyrite, in the VMS mineralization system, and the second Chl-II occurs along with zeolite and native copper mineralization. The EPMA results show that Chl-I is more Fe-rich than Chl-II.

The Poshteh deposit is the first documented paleo-hydrothermal chimney-bearing volcanogenic massive sulfide (VMS) deposit in Iran. It occurs in the form of well-developed lensoid orebodies within the Eocene volcano-sedimentary sequence, and comprises of laminated, brecciated, banded, massive, and disseminated textures. The stratiform part of this deposit is approximately 500 m long and up to 20 m thick, and consists of massive to semi-massive sulfides and barites, some of which are banded, which are overlain by barite and siliceous exhalites. The stringer zone stratigraphically underlies the stratiform mineralization. Veins within the stringer zone are composed of quartz, barite, pyrite, galena, sphalerite, and chalcopyrite. Three thin layers of exhalative Mn–Fe-bearing chert overlies the sulfide–sulfate orebodies. Four types of fluid inclusions were recognized in barite and quartz encompassing monophase vapor, monophase liquid, two-phase liquid-rich inclusions, and two-phase vapor-rich fluid inclusions. The homogenization temperatures of fluid inclusions mainly vary between 86.2 and 241.9 °C, whereas their salinities focus on 0.99–21.23 wt.% NaCl equiv. The ore-forming fluids of the barite and quartz minerals are characterized by low-to-medium temperature and low-to-medium salinity. The δ 34 S values of barite associated with the stratiform and stringer barite orebody range from 8.37 to 21.83 ‰, indicating that the sulfur was derived from the seawater. The sulfur isotope values of sulfide (− 5.18 to 9.33 ‰) are similar to those of VMS deposits from other parts of the world. The δ 18 O data suggest that the ore-forming fluids of the Poshteh deposit were mainly derived from deep subseafloor circulation of seawater. The well-preserved chimneys typically contain distinct concentric outer and inner sulfide- and axial sulfate-rich zones. The outer zones of the chimneys contain mainly pyrite and chalcopyrite. The sulfides within the inner zone consist predominantly of sphalerite, argentite, and galena. The axial conduits are commonly dominated by barite and calcite. The sulfide-rich chimney zones are also characterized by significantly higher metal contents. The presence of paleo-hydrothermal vent chimneys in the Poshteh Kuroko-type deposit and their trace-element contents also provides significant data for understanding the physicochemical conditions of VMS mineralization.

Pyrite ores on the flanks of the Saum copper–zinc massive sulfide deposit are clastic sediments intensely transformed under conditions of acid diagenesis. Colusite in ores is confined to fine-grained pyrite clasts, which are rimmed by later small-crystalline pyrite aggregates. Colusite forms fine dissemination (1–3 µm) and large isometric grains (up to 50–100 µm), contains inclusions of sulvanite, and belongs to arsenocolusite in chemical compositions (wt %): 12.62–14.87 As, 0.19–0.64 Sb, 0.29–1.46 Sn, 3.05–3.23 V, and 1.51–3.20 Fe. The LA ICP MS analysis of fine-grained pyrite revealed minor Ga, Ge, In, and Se contents in composition of arsenocolusite, which are correlated with chemical elements of colusite according to isomorphous substitutions in its formula. Galena, tellurobismuthite, native gold, molybdenite, rutile, monazite, uraninite, and Ba-bearing muscovite are found in fine-grained pyrite in assemblage with colusite. Interaction of sulfide sediments with seawater led to their enrichment in seawater elements (V, Mo, and U) and the deposition of colusite in assemblage with molybdenite and uraninite from trace element-rich diagenetic fluids under their dehydration.

Relevance. The LA-ICP-MS analysis of sulfides is one of the promising directions in study of ore deposits. The understanding of mineralogical-geochemical evolution of sulfides allows interpretation of differentiation of components at stages of hydrothermal sedimentogenesis and further lithogenesis of massive sulfide deposits. This work is important for development of models of sulfide authigenesis. The main aim of the research is to compare mineralogical-geochemical features of chalcopyrite types to identify the evolution of sulfide ores from the Yubileynoe massive sulfide deposit (South Urals). Methods. The morphogenetic types of chalcopyrite were identified using ore-facial mapping in the open pit of the deposit. The mineralogical features of ores were studied under an Olympus BX51 optical microscope. The chemical composition of minerals was analyzed on a Tescan Vega 3 SBU scanning electron microscope equipped with an Oxford Instruments X-act energy dispersive analyzer. The trace element contents of chalcopyrite were determined using LA-ICP-MS on an Agilent 7700x mass spectrometer equipped with a New Wave Research UP-213 laser ablation device at the SU FRC MG UB RAS and University of Tasmania (Hobart, Australia). Results. Chalcopyrite was subdivided into two genetic types: hydrothermal and post-sedimentary. The hydrothermal type includes subhedral chalcopyrite from chalcopyrite-pyrite, chalcopyrite-pyrite-sphalerite, and sphalerite-pyrite-chalcopyrite smoker chimneys. The post-sedimentary type of pseudomorphic, interstitial, nodular, and veinlet (dynamometamorphic) chalcopyrite is typical of clastic ore. Each chalcopyrite type is characterized by various mineral assemblages and trace element contents, reflecting different formation conditions. Themorphology of chalcopyrite changes from spear-like and dendritic crystals to graphic and epitaxial intergrowths of chalcopyrite and sphalerite in a range from chalcopyrite-pyrite to mostly sphalerite smoker chimneys. The median contents of high-temperature (Se, Bi), medium-temperature (Te, Sb) and low-temperature (Tl) trace elements of hydrothermal chalcopyrite decrease in this range. The post-sedimentary chalcopyrite has the lower Sn contents and exhibits minor variations in Se contents. The median Mn, Co, Ni, Mo, As, Tl, Au, Ag, Bi, and Te contents decrease in a consecutive range of post-sedimentary chalcopyrite: pseudomorphic -> interstitial -> nodular -> veinlet.

The massive sulfide ores of the Pobeda hydrothermal fields are grouped into five main mineral microfacies: (1) isocubanite-pyrite, (2) pyrite-wurtzite-isocubanite, (3) pyrite with minor isocubanite and wurtzite-sphalerite microinclusions, (4) pyrite-rich with framboidal pyrite, and (5) marcasite-pyrite. This sequence reflects the transition from feeder zone facies to seafloor diffuser facies. Spongy, framboidal, and fine-grained pyrite varieties replaced pyrrhotite, greigite, and mackinawite “precursors”. The later coarse and fine banding oscillatory-zoned pyrite and marcasite crystals are overgrown or replaced by unzoned subhedral and euhedral pyrite. In the microfacies range, the amount of isocubanite, wurtzite, unzoned euhedral pyrite decreases versus an increasing portion of framboidal, fine-grained, and spongy pyrite and also marcasite and its colloform and radial varieties. The trace element characteristics of massive sulfides of Pobeda seafloor massive sulfide (SMS) deposit are subdivided into four associations: (1) high temperature—Cu, Se, Te, Bi, Co, and Ni; (2) mid temperature—Zn, As, Sb, and Sn; (3) low temperature—Pb, Sb, Ag, Bi, Au, Tl, and Mn; and (4) seawater—U, V, Mo, and Ni. The high contents of Cu, Co, Se, Bi, Te, and values of Co/Ni ratios decrease in the range from unzoned euhedral pyrite to oscillatory-zoned and framboidal pyrite, as well as to colloform and crystalline marcasite. The trend of Co/Ni values indicates a change from hydrothermal to hydrothermal-diagenetic crystallization of the pyrite. The concentrations of Zn, As, Sb, Pb, Ag, and Tl, as commonly observed in pyrite formed from mid- and low-temperature fluids, decline with increasing crystal size of pyrite and marcasite. Coarse oscillatory-zoned pyrite crystals contain elevated Mn compared to unzoned euhedral varieties. Framboidal pyrite hosts maximum concentrations of Mo, U, and V probably derived from ocean water mixed with hydrothermal fluids. In the Pobeda SMS deposit, the position of microfacies changes from the black smoker feeder zone at the base of the ore body, to seafloor marcasite-pyrite from diffuser fragments in sulfide breccias. We suggest that the temperatures of mineralization decreased in the same direction and determined the zonal character of deposit.

LA-ICPMS analysis of pyrite in ten gold deposits is used to determine the precise siting of invisible gold within pyrite, and thus the timing of gold introduction relative to the growth of pyrite and related orogenic events. A spectrum of invisible gold relationships in pyrite has been observed which suggests that, relative to orogenic pyrite growth, gold introduction in some deposits is early at the start of pyrite growth; in other deposits, it is late toward the end of pyrite growth and in a third case, it may be introduced at the intermediate stage of orogenic pyrite growth. In addition, we report a distinct chemical association of invisible gold in pyrite in the deposits studied. For example, in the Gold Quarry (Carlin type), Mt Olympus, Macraes and Konkera, the invisible gold is principally related to the arsenic content of pyrite. In contrast, in Kumtor and Geita Hill, the invisible gold is principally related to the tellurium content of pyrite. Other deposits (Golden Mile, Bendigo, Spanish Mountain, Witwatersrand Carbon Leader Reef (CLR)) exhibit both the Au-As and Au-Te association in pyrite. Some deposits of the Au-As association have late orogenic Au-As-rich rims on pyrite, which substantially increase the value of the ore. In contrast, deposits of the Au-Te association are not known to have Au-rich rims on pyrite but contain nano- to micro-inclusions of Au-Ag-(Pb-Bi) tellurides.

The formation of present-day seafloor sulfide deposits is accompanied by their continuous oxidation and crystallization of insoluble Fe oxyhydroxides, which absorb metals (including heavy metals) (Fallon et al., 2017). Due to the high sorption ability of Fe oxyhydroxides, it is suggested that the removal of metals during submarine oxidation into ambient seawater is insignificant (Fallon et al., 2017). Quantitative data on the redistribution of trace elements between primary sulfides and their oxidation products, however, are insufficient. Recently, we revealed the enrichment of trace elements in covellite with respect to primary sphalerite, chalcopyrite, and isocubanite (Melekestseva et al., 2017). In this study, we estimate the behavior of trace elements during submarine oxidation of sphalerite from smokers at the Irinovskoe hydrothermal field (Atlantic Ocean), which is intensely replaced by Fe oxyhydroxides. As a result, it is established that Fe oxyhydroxides are enriched in many trace elements with respect to sphalerite and the mode of their occurrence is identified.