Composition Of Sphalerite Research Articles

Metallogeny of the Sarsuk polymetallic Au deposit in the Ashele Basin, Altay Orogenic Belt, Xinjiang, NW China: Constraints from mineralogy, fluid inclusions, and He–Ar isotopes

The Sarsuk polymetallic Au deposit is located in the Devonian volcano-sedimentary Ashele Basin of the Altay Orogenic Belt (AOB), Xinjiang. Mineralization in the deposit is confined to an area of 400m long and 50–120m wide, and occurs as dense massive, banded, disseminated, stockwork, and veinlet ore structures. Exhalative sedimentary, subvolcanic hydrothermal, and supergene periods have been distinguished. Although syn-depositional ores can be found, the main orebodies from this period have been eroded. Thus, the orebodies being mined are hosted mainly in a rhyolite porphyry subvolcanic intrusion within the volcanic conduit of a hydrothermal system. Electron microprobe analysis of the main ore minerals indicates that pyrite is the main Au-bearing mineral. The Au occurs mainly as either inclusions or in fissures in the form of tellurides, and is closely associated with Ag. Zn/Fe ratios of sphalerite vary from 11.37 to 251.36, with an average of 96.65, and the formation temperatures of chlorites are 155–206°C, with an average of 175°C. The compositions of sphalerite and chlorite indicate that the main mineralization occurred in a low- to moderate-temperature environment. Homogenization temperatures of fluid inclusions from ores of the main mineralization stage vary generally from 130°C to 390°C, with peaks at 140°C, 190°C, and 310°C. Their corresponding salinities range from 3.0 to 10.0wt.% NaCl equivalent, with densities from 0.56 to 1.03g/cm3. The main mineralizing fluid of the deposit is characterized by high–low temperatures, moderate–low salinities, and moderate–low densities. The 3He/4He ratios of fluid inclusions in pyrite are 0.02 to 0.44 Ra, and the percentage of mantle-derived He ranges from 0.06% to 7.45%. 40Ar/36Ar ratios range from 319.6 to 458.5, and the percentage of 40Ar* varies from 7.53% to 35.55%. Both fluid characteristics and He and Ar isotope compositions suggest that the ore-forming fluids were a mixture of magmatic fluid and seawater. The CO2-rich fluids in the ores suggest that boiling occurred. The mixing of a high-temperature and high-pressure magmatic fluid with deeply circulating seawater caused a decrease in temperature, and phase separation in the ore-forming fluids. Thus, the precipitation of the most economically important ore materials was the result of this mixing process.

Mineralogy, chalcopyrite Re[sbnd]Os geochronology and sulfur isotope of the Hujiayu Cu deposit in the Zhongtiao Mountains, North China Craton: Implications for a Paleoproterozoic metamorphogenic copper mineralization

The Hujiayu Cu deposit, located in the Zhongtiao Mountains district of southern North China Craton, is hosted by graphite schist and dolomitic marble with disseminated to veinlet (stage I) and thick vein (stage II) mineralization. Stage I mineralization, characterized by stratabound, disseminated pyrite and chalcopyrite within the graphite schist host rock, formed at the syn-metamorphic stage. Graphite geothermometry showed that the host rock was subjected to an upper-greenschist to lower amphibolite metamorphism at a temperature range of 486 to 596°C, averaging of 546±35°C (1σ, n=19). Stage II mineralization, consisting of brecciated dolomitic thick veins cemented by quartz-sulfide assemblages, was a product of metamorphic hydrothermal activity. This thick vein was subdivided into an early hydrothermal dolomitic alteration composing of dolomitic breccia with some cobaltiferous pyrite (stage IIa) and a late siliceous-copper mineralization consisting of quartz-sulfide assemblages (stage IIb). A clausthalite–siegenite–sphalerite–chalcopyrite mineral assemblage was observed in stage IIb, constraining the sulfur fugacity and selenium fugacity within −18.7 to −11.7 and −21.7 to −14.7, respectively. It was inferred stage IIb was marked by a drop in sulfur fugacity and a substantial increase in selenium fugacity after the major chalcopyrite precipitation. Calculations based on the compositions of cobaliterous pyrite and sphalerite reveal that the mineral assemblage at stage IIa formed at an approximately temperature range of 400 to 300°C, whereas the minerals in stage IIb occurred at temperature of 256±9°C (1σ, n=7). Sulfides from stage I have δ34S value ranging from 10.1 to 22.2‰ with an average value of 16.9±3.4‰ (1σ, n=27), supporting the model that sulfides precipitated through thermochemical reduction of sulfate at sedimentary stage followed by metamorphic homogenization of δ34S isotopic signatures. Sulfides from the stage II have δ34S values in highly variable ranging from 3.4 to 19.2‰, indicating a rather complex source. Four chalcopyrite samples yielded a weighted model age of 1952±39Ma (1σ, MSWD=1.5), suggesting that the copper mineralization formed synchronously with regional metamorphism (1970–1850Ma) and hence a Paleoproterozoic metamorphogenic copper mineralization is implicated. Therefore, we envisaged disseminated-veinlet mineralization formed during a metamorphic peak and the major hydrothermal copper mineralization occurred during the retrograde cooling.

Zinc and lead isotope signatures of the Zhaxikang Pb[sbnd]Zn deposit, South Tibet: Implications for the source of the ore-forming metals

Stable Zn isotopes may be applied to trace the source of ore-forming metals in various types of PbZn deposits. To test this application, Zn and Pb isotope systematics for sulfides and associated basement rocks as well as FeMn carbonates (gangue) from the Zhaxikang PbZn deposit in South Tibet have been analyzed. The basement in this region includes metamorphosed mafic to felsic rocks (dolerite, quartz diorite, rhyolite porphyry, pyroclastics and porphyritic monzogranite). These rocks have similar δ66Zn values of 0.33 to 0.37‰, with an average value of 0.36±0.03‰ (2σ), except for the more evolved porphyritic monzogranite that has a heavier value of 0.49‰. FeMn carbonates are present as hydrothermal veins and were probably precipitated from magmatic fluids. They have an average δ66Zn value of 0.27±0.05‰, which is slightly lighter than the basement rocks, possibly representing δ66Zn isotopic compositions of the hydrothermal fluids. Sphalerite and galena have similar Zn isotopic compositions with δ66Zn ranging from 0.03 to 0.26‰ and 0.21 to 0.28‰, respectively. Considering the Zn isotope fractionation factor between sphalerite and fluids of −0.2‰ at ~300°C as reported in literature, hydrothermal fluids from which these sulfides precipitated will have δ66Zn values of ca. 0.39±0.10‰, which are consistent with the values of basement rocks and the FeMn carbonates. This similarity supports a magmatic-hydrothermal origin of the Zhaxikang PbZn deposit. Both Pb and S isotopes in these sphalerite and galena show large variations and are consistent with being derived from a mixture of basement and sedimentary rocks in various proportions. Zn isotopic compositions of the sulfides significantly extend the range of regional basement rocks, suggesting that sedimentary rocks (e.g., shales) are also a significant source of Zn. However, the Zn isotopic compositions of sphalerite and galena differ from those of marine carbonates and those of typical SEDEX-type deposits (e.g. Kelley et al., 2009), confirming a magmatic-hydrothermal model. Combined with regional geological observations and the age constraints of ~20Ma (Zheng et al., 2012, 2014), the results of our investigation indicate that the Zhaxikang PbZn deposit is most likely a magmatic-hydrothermal deposit.

Petrography, mineral chemistry, fluid inclusion microthermometry and Re–Os geochronology of the Küre volcanogenic massive sulfide deposit (Central Pontides, Northern Turkey)

The Re–Os isotopic system is applied for the first time to the sulfide ores and the overlying black-shales at the Küre volcanogenic massive sulfide deposit of the Central Pontides, Northern Turkey. The ore samples collected include predominantly pyrite, accompanied by chalcopyrite, sphalerite and other species. Massive ore is almost free of gangues, whereas the stockwork ore includes quartz and calcite gangue. The composition of sphalerite is similar to ancient and modern massive sulfide mineralizations globally. Microthermometric studies from quartz from the stockwork ore has shown two populations of two-phase fluid inclusions with vapor/liquid ratios between 4 to 28%, low to intermediate Th (161.5–317.0°C) and low salinities (0.9–5wt.% NaCl equiv.) which are mostly in good agreement with the ranges for volcanogenic massive sulfide mineralizations. These studies also suggest a H2O–CaCl2–KCl–MgCl2 ore-forming fluid system in a shallower subsurface near the seafloor vents. The Re–Os dating of the LLHR sulfides yield a nominal depositional age of upper Toarcian for the massive sulfide mineralization. Two largely different model ages obtained are attributed to other pyrite crystallization events prior to and postdating the main sulfide deposition. Some lower homogenization temperatures (<200°C) from the quartz of the stockwork may also similarly be related to the post-VMS events. It is concluded that a submarine volcanic extrusion episode has continued until upper Toarcian in the Küre Basin, when it has entered a stagnation period that allowed the discharge of hydrothermally circulated sulfide-laden fluids from the seafloor vents. This age data promotes the palaeotectonic models interpreting the Küre Basin as a Permian–early Jurassic marginal back-arc basin of the Devonian-Triassic Karakaya Ocean. The Re–Os data from the overlying black-shale provide a glimpse to the initial Os isotope ratio of the water column at the time of the sedimentation (0.45–0.46 for 180Ma). The lack of common Os from the sulfides does not let us to infer a source of Os and initial 187Os/188Os ratios from the black shale are not statistically robust to make a significant deduction. A further detailed study on the isotopic composition of the black shale strata may help us to make an apporach to the Os source(s) in the deposition environment of the Küre VMS deposit.

The multistage genesis of the giant Dongshengmiao Zn-Pb-Cu deposit in western Inner Mongolia, China: Syngenetic stratabound mineralization and metamorphic remobilization

The genesis of the giant Dongshengmiao in the northern margin of the North China Block has been debated since its discovery in the 1950s, because it shows geological and geochemical characteristics with both syngenetic and epigenetic signatures. It has geological settings and sulfur and lead isotopic compositions that are similar with typical SEDEX (sedimentary exhalative) deposit, while the Zn-Pb-Cu mineralization was controlled by shear deformation and metamorphism, showing similarities with orogenic-type deposits. In this contribution, both the syngenetic and epigenetic features of the Dongshengmiao are envisaged, and accounted for in the context of a genetic model with two metallogenic periods. Massive pyrite at the Dongshengmiao was mostly recrystallized during metamorphism, but fine-grained texture was locally preserved, indicating its syngenetic origin. On the contrary, all the Zn-Pb-Cu ores observed in this study show characteristics of epigenetic hydrothermal mineralization that controlled by metamorphism and accompanying shear deformation. The sulfur and lead isotopic compositions of sphalerite and galena indicate that they were in situ remobilized from a syngenetic stratabound source, and the oxygen and hydrogen isotopic ratios of ore-fluid indicate that the large-scale remobilization was assisted by metamorphic fluid. The thermodynamic modeling indicates that the ore-fluid during remobilization has a great potential of transporting Cu. This may account for the abnormally enriched Cu in the remobilized SEDEX deposit. The metamorphic fluid might strip Cu from the fluid source during devolatilization, and overprint it on the Zn-Pb orebodies during remobilization. A secondary flow-through modeling reveals that Zn- and Cu-sulfides would be preferentially redistributed in Fe-rich carbonates during remobilization, as a result of fluid-rock interaction. Conclusively, a multistage genetic model is proposed. During the development of the Proterozoic rift, stratabound Zn-Pb mineralization took place in a SEDEX ore-forming system. The syngenetic sulfides subsequently underwent a large-scale fluid-assisted remobilization during the early Cretaceous metamorphism and thrusting, forming the shear zone-controlled epigenetic orebodies. During the remobilization process, Cu was scavenged from the source of metamorphic fluid, and deposited accompanying remobilized Zn-Pb sulfides. Shear structures and Fe-rich carbonates are ideal sites for redistribution and re-deposition of remobilized sulfide.

Mineralogy, geochemistry and sulfur isotope characterization of Cerro de Maimón (Dominican Republic), San Fernando and Antonio (Cuba) lower Cretaceous VMS deposits: Formation during subduction initiation of the proto-Caribbean lithosphere within a fore-arc

The volcanic-arc Lower Cretaceous Maimón (Dominican Republic) and Los Pasos (Cuba) Formations, representative of the oldest magmatism recorded in the Caribbean island arc, host most of the known volcanogenic massive sulfide (VMS) deposits in the Greater Antilles. On the basis of new lithogeochemical data, basalts of the Maimón Formation are classified as fore arc basalts (FAB), boninites and less abundant low-Ti (LOTI) and normal island-arc tholeiites (IAT), and those of the Los Pasos Formation as LOTI and IAT. Felsic volcanics from the two formations are geochemically analogous and present mantle-type (M-type), boninitic and tholeiitic signatures, classifying as FIV-type, typical of post-Archaean VMS-bearing juvenile volcanic suites. This lithogeochemical data is indicative of formation in a fore-arc environment just after subduction initiation in association with initial extensional regimes and associated boninitic and tholeiitic melts that originated in the shallow mantle. Within this tectonic framework, rocks of the Los Pasos Formation and associated VMS deposits likely formed at a slightly later stage than those of the Maimón Formation.Primary syngenetic ore mineral assemblages from VMS deposits in the Cerro de Maimón (Maimón Formation), San Fernando and Antonio (Los Pasos Formation) are similar. They are composed mainly of pyrite in a matrix with variable proportions of chalcopyrite, sphalerite and tennantite. However, variable metamorphism and deformation have imprinted distinct deformation/recovery textures on the three deposits. Relict sedimentary-diagenetic sulfide growths are preserved only in Antonio ore in the form of local framboidal and colloform growths and microcrystallite textures. Spongy texture, dominant in the Antonio deposit and sparse in San Fernando ores, along with overgrowths of pyrite are interpreted as representative of syn-depositional hydrothermal replacement. Annealing texture among pyrite grains and rotated pyrite porphyroclasts with adjacent asymmetric pressure shadows, combined with cataclastic textures in Cerro de Maimón ore denote higher metamorphic grade and more intense deformation. Syn-metamorphic sulfide recovery/recrystallization led to the remobilization of trace elements and subsequent crystallization of discrete minerals (galena, tellurides, tetrahedrite, arsenopyrite/löllingite, Ag-sulfosalts and electrum).The chemical composition of sphalerite from the three deposits suggests ore formation in a sediment-starved environment. Estimated minimum venting fluid temperature calculated from the composition of sphalerites from stratiform mineralization in the three deposits is in the range of 242 to 302°C. Tennantite crystals from the three deposits returned low Sb and Ag contents, typical of VMS mineralization formed in juvenile intraoceanic island-arc settings. A broad trend towards Sb enrichment in stratiform ores in the San Fernando and Antonio deposits parallels lower concentration of Se and As and higher contents in the more incompatible Sb, Te and Bi in galena with respect to Cerro de Maimón. These nuances in ore geochemistry are in good agreement with the slightly more primitive setting of formation of VMS mineralization hosted in the Maimón Formation, as indicated by the lithogeochemistry of the volcanic host rocks.The sulfides from Cerro de Maimón display δ34S values of −1.3 to +3.0‰, whereas those from the San Fernando and Antonio deposits were in the range of −0.5 to +7.0‰ and of 0.0 to +5.8‰ respectively. The relatively narrow scatter of δ34S suggests homogeneous fluid sulfur composition and similar physico-chemical conditions during the ore forming processes, and is consistent with sulfide derived from the inorganic reduction of seawater and/or from a magmatic source.Although the three deposits are classified as non-auriferous, significant Au contents are described in Cerro de Maimón ore (to 7.6g/t) and in intermediate (to 1.44g/t) and upper (to 0.88g/t) mineralized zones of the San Fernando deposit. Gold, probably precipitated as invisible gold during exhalative mineralization, shows evidence for later metamorphism- and deformation-triggered remobilization and re-precipitation as subordinate electrum. Solid-state mechanical transfer was apparently the dominant upgrading mechanism in the Cerro de Maimón deposit whereas liquid-state chemical transfer would have governed the upgrading process in the San Fernando deposit.

High precision in-situ Pb isotopic analysis of sulfide minerals by femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry

An in-situ microanalysis of Pb isotopic compositions in sulfide minerals is carried out by using femtosecond laser-ablation multi-collector inductively coupled plasma mass spectrometry (fsLA-MC-ICP-MS). High-temperature-activated carbon was used to filter Hg contained in the carrier gas, which reduced the Hg background signal by 48% and also lowered the detection limit of the analysis. Fractionation and mass discrimination effects existing in the ICP-MS analytical processes were corrected using an internal reference Tl in conjunction with an external reference NIST SRM 610. The proposed method was used to analyze the Pb isotopic compositions of chalcopyrite, pyrite, and sphalerite from the Dulong Sn-Zn-In polymetallic ore district. The results showed that in this ore district, the sulfide minerals and different grains of the same sulfide mineral show a large variation in Pb content up to 1000-fold. The studied pyrites show relatively higher Pb contents and homogeneous Pb isotopic compositions, whereas the sphalerites have low Pb contents but most variable Pb isotopic compositions. It is suggested that the large variation of Pb isotopic composition may reflect a late hydrothermal superimposition on the primary sulfide formation. In addition, radiogenic Pb accumulated by radioactive decay of trace amounts of U over time in the host minerals may also be one of the causes for the large variation range of Pb content and Pb isotopic composition of those low-Pb sphalerites. Chalcopyrite and sphalerite grains with Pb content greater than 10 ppm presented a consistent Pb isotopic distribution, whereas all the sulfide grains with Pb content greater than 100 ppm had consistent Pb isotopic composition within 2s measurement uncertainties. The in-situ analysis of Pb isotopic composition agreed well with the results obtained by conventional chemical methods within 2s measurement uncertainties, indicating that the data obtained by fsLA-MC-ICP-MS are reliable. Additionally, this study indicates that the Pb isotopic composition could truthfully record the source of ore-forming minerals only for sulfide minerals with high Pb content. On the contrary, the Pb isotopic composition of low-Pb sulfide minerals may be affected by trace amounts of U in the host minerals that may lead to a highly radiogenic Pb isotope ratio. Alternatively, it is also possible that late fluid metasomatic overprinting may alter the Pb isotopic compositions.

Minor Elements in Layered Sphalerite as a Record of Fluid Origin, Mixing, and Crystallization in the Navan Zn-Pb Ore Deposit, Ireland

Research Article| September 01, 2014 Minor Elements in Layered Sphalerite as a Record of Fluid Origin, Mixing, and Crystallization in the Navan Zn-Pb Ore Deposit, Ireland* D. Gagnevin; D. Gagnevin 1Tullow Oil plc, Number 1, Central Park, Leopardstown, Dublin 18, Ireland Search for other works by this author on: GSW Google Scholar J. F. Menuge; J. F. Menuge † 2UCD School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland †Corresponding author: e-mail, j.f.menuge@ucd.ie Search for other works by this author on: GSW Google Scholar A. Kronz; A. Kronz 3Geowissenschaftliches Zentrum, Georg-August-Universität, D-37077 Göttingen, Germany Search for other works by this author on: GSW Google Scholar C. Barrie; C. Barrie 4Isoprime Ltd, Isoprime House, Earl Road, Cheadle Hulme, Cheadle SK8 6PT, United Kingdom Search for other works by this author on: GSW Google Scholar A. J. Boyce A. J. Boyce 5Scottish Universities Environmental Research Centre, East Kilbride, Glasgow G75 0QF, United Kingdom Search for other works by this author on: GSW Google Scholar Author and Article Information D. Gagnevin 1Tullow Oil plc, Number 1, Central Park, Leopardstown, Dublin 18, Ireland J. F. Menuge † 2UCD School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland A. Kronz 3Geowissenschaftliches Zentrum, Georg-August-Universität, D-37077 Göttingen, Germany C. Barrie 4Isoprime Ltd, Isoprime House, Earl Road, Cheadle Hulme, Cheadle SK8 6PT, United Kingdom A. J. Boyce 5Scottish Universities Environmental Research Centre, East Kilbride, Glasgow G75 0QF, United Kingdom †Corresponding author: e-mail, j.f.menuge@ucd.ie Publisher: Society of Economic Geologists Received: 20 Mar 2013 Accepted: 31 Oct 2013 First Online: 09 Mar 2017 Online ISSN: 1554-0774 Print ISSN: 0361-0128 © 2014 Society of Economic Geologists. Economic Geology (2014) 109 (6): 1513–1528. https://doi.org/10.2113/econgeo.109.6.1513 Article history Received: 20 Mar 2013 Accepted: 31 Oct 2013 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation D. Gagnevin, J. F. Menuge, A. Kronz, C. Barrie, A. J. Boyce; Minor Elements in Layered Sphalerite as a Record of Fluid Origin, Mixing, and Crystallization in the Navan Zn-Pb Ore Deposit, Ireland. Economic Geology 2014;; 109 (6): 1513–1528. doi: https://doi.org/10.2113/econgeo.109.6.1513 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract This study tests the utility of the minor to trace element composition of sphalerite to discriminate between possible sources of ore-forming fluids, and to constrain processes involved in ore genesis of the world-class Irish-type Navan Zn-Pb orebody, Ireland. Detailed petrography and electron microprobe microanalyses were performed on layered sphalerite previously analyzed for Zn, Fe, and S isotope compositions. Layered sphalerite displays a wide range of chemical composition at both sample and crystal scales. The color, style, and scale of layering show variations with chemical composition, but none of these correlations are consistent between samples. However, there are strong intersample correlations between chemical and S-Fe-Zn isotope compositions at the millimeter scale. Sphalerite precipitated from deep, hydrothermal fluids with 34S-enriched sulfide is enriched in Cd, Sb, Cu, and Ag, whereas Fe and As are enriched in sphalerite precipitated from shallow, bacteriogenic brines with isotopically light S. Significant chemical variations also occur at the micrometer scale in sphalerite regardless of its genetic affinity. These variations are interpreted as being due to variations in temperature, pH, and sulfur activity following the arrival at the site of deposition of pulses of hydrothermal fluids at specific stages of sphalerite growth. Therefore the chemistry of sphalerite, coupled with its texture, appears to be a powerful tool to elucidate fluid typing and ore genesis. The results support the hypothesis that layered sphalerite forms by rapid crystallization due to mixing of two fluids of contrasting physicochemical properties, a process required for the formation of Irish-type and some other hydrothermal deposits including, most notably, Mississippi Valley-type (MVT) deposits. The existence of layered sphalerite, coupled with its texture and chemical composition, may therefore provide useful insight for the mineral exploration industry in Ireland and elsewhere. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Effects of temperature, sulfur, and oxygen fugacity on the composition of sphalerite from submarine hydrothermal vents

Experimental studies have shown that temperature, pressure, sulfur fugacity (fS2), and oxygen fugacity (fO2) influence the Fe content of sphalerite. We present compositional in situ data on sphalerite from submarine volcanic-hosted massive sulfide (VHMS) ores of hydrothermal vents from different plate tectonic settings and with variable host-rock compositions. Sphalerite from sediment-hosted vents has systematically higher S contents and Fe/Zn ratios than those of the sediment-starved vents, reflecting an influence of fS2 and fO2 on Fe partitioning between fluid and sphalerite. The Fe/Zn ratios of sphalerite from sediment-starved vent systems apparently increase systematically with the fluid temperatures of the corresponding vents. We conclude that the composition of sphalerite can be used to (1) distinguish between sediment-hosted and sediment-starved hydrothermal processes, and (2) estimate minimum fluid temperatures of sphalerite precipitation from inactive sediment-starved hydrothermal vent sites and fossil VHMS deposits.

Zinc, sulfur and lead isotopic variations in carbonate-hosted Pb–Zn sulfide deposits, southwest China

The Sichuan–Yunnan–Guizhou Pb–Zn metallogenic province in the western Yangtze Block, southwest China, contains more than four hundred Pb–Zn deposits with more than 200milliontons of Pb–Zn ores at mean grades of 5wt.% Pb and 10wt.% Zn. These deposits are hosted in Sinian (Ediacaran) to Permian carbonate rocks and are structurally controlled by thrust fault–fold structures, and are spatially associated with the late Permian~260Ma Emeishan flood basalts. Two representative low temperature hydrothermal Pb–Zn sulfide deposits, the Tianqiao and Banbanqiao deposits in the southeastern part of the Sichuan–Yunnan–Guizhou Pb–Zn metallogenic province are selected for Zn–S–Pb isotopic analyses. Sphalerite from the Tianqiao deposit has δ66Zn values ranging from −0.26 to +0.58‰ relative to the JMC 3–0749L zinc isotope standard, whereas δ66Zn values of sphalerite from the Banbanqiao deposit range from +0.07 to +0.71‰. The zinc isotopic composition of sphalerite from both deposits increase from early to final mineralization stage. In addition, sphalerite from the center (near to bottom) part of the No. 1 ore body in the Tianqiao deposit has lower δ66Zn values (−0.01 to +0.43‰) than those (+0.11 to +0.57‰) in the periphery (near to top). Sinian to Permian sedimentary rocks and Permian Emeishan flood basalts, the potential zinc metal source rocks, have δ66Zn values range from −0.24 to +0.17‰ and from +0.32 to +0.44‰, respectively. The majority of the hydrothermal sphalerite has heavier zinc isotope than the country rocks, precluding the mixing of multiple zinc sources as the key factor controlling the spatial and temporal variations of zinc isotope. Therefore, the increased δ66Zn values from the early to late stage and from the center to top could be due to kinetic Raleigh fractionation. Sphalerite from the Tianqiao and Banbanqiao deposits has δ34S values ranging from +10.9 to +14.8‰ and from +3.9 to +9.0‰, respectively, lower than Cambrian to Permian marine sulfates (+15 to +35‰) and sulfate-bearing evaporates (+15 to +28‰) in the Devonian to Permian carbonate host rocks. Sulfur of the Pb–Zn ores from both deposits is interpreted as the result of thermal chemical sulfate reduction of evaporates in the sedimentary rocks, most likely the host rocks. Sphalerite from the Tianqiao deposit has Pb isotope similar to that of age-corrected Devonian to Permian carbonate host rocks, whereas sphalerite from the Banbanqiao deposit has Pb isotope similar to that of age-corrected underlying Precambrian basement rocks. Therefore, at least lead in the Tianqiao and Banbanqiao deposits was mainly originated from the host rocks and the underlying basements, respectively. Zn–S–Pb isotopic studies of sphalerite from both deposits indicate that sources of metals and sulfur in the hydrothermal fluid for the Tianqiao deposit are the Paleozoic carbonate host rocks, whereas for the Banbanqiao deposit the sources are the Precambrian basements and the Paleozoic carbonate host rocks, respectively.

Au–Ag–Te Mineralization of the Low‐Sulfidation Epithermal Aginskoe Deposit, Central Kamchatka, Russia

AbstractMineralogic studies of major ore minerals and fluid inclusion analysis in gangue quartz were carried out for the for the two largest veins, the Aginskoe and Surprise, in the Late Miocene Aginskoe Au–Ag–Te deposit in central Kamchatka, Russia. The veins consist of quartz–adularia–calcite gangue, which are hosted by Late Miocene andesitic and basaltic rocks of the Alnei Formation. The major ore minerals in these veins are native gold, altaite, petzite, hessite, calaverite, sphalerite, and chalcopyrite. Minor and trace minerals are pyrite, galena, and acanthine. Primary gold occurs as free grains, inclusions in sulfides, and constituent in tellurides. Secondary gold is present in form of native mustard gold that usually occur in Fe‐hydroxides and accumulates on the decomposed primary Au‐bearing tellurides such as calaverite, krennerite, and sylvanite. K–Ar dating on vein adularia yielded age of mineralization 7.1–6.9 Ma. Mineralization of the deposit is divided into barren massive quartz (stage I), Au–Ag–Te mineralization occurring in quartz‐adularia‐clays banded ore (Stage II), intensive brecciation (Stage III), post‐ore coarse amethyst (Stage IV), carbonate (Stage V), and supergene stages (Stage VI). In the supergene stage various secondary minerals, including rare bilibinskite, bogdanovite, bessmertnovite metallic alloys, secondary gold, and various oxides, formed under intensely oxidized conditions. Despite heavy oxidation of the ores in the deposit, Te and S fugacities are estimated as Stage II tellurides precipitated at the log f Te2 values −9 and at log fS2 −13 based on the chemical compositions of hypogene tellurides and sphalerite. Homogenization temperature of fluid inclusions in quartz broadly ranges from 200 to 300°C. Ore texture, fluid inclusions, gangue, and vein mineral assemblages indicate that the Aginskoe deposit is a low‐sulfidation (quartz–adularia–sericite) vein system.

Geology, geochemistry, and geochronology of the Dunde iron–zinc ore deposit in western Tianshan, China

The Dunde iron–zinc deposit (185Mt at 35% Fe), located in the Tianshan orogenic belt, Xinjiang, northwest China, is hosted in late Carboniferous volcanic–volcaniclastic rocks characterized by prograde skarn formation and retrograde alteration, but the ore lacks any clear spatial link with intrusive rocks. Four stages of skarn formation and ore development can be recognized: (1) a prograde skarn stage that formed grossularitic garnet (Gr39–80; Ad15–58) and diposidic pyroxene (Di63–97); (2) a retrograde skarn stage dominated by the formation of magnetite with minor epidote, ferropargasite, apatite, hematite, and trace amounts of titanite and spinel; (3) a sulfide stage dominated by the formation of arsenide (loellingite and arsenopyrite) and sulfide minerals (sphalerite, pyrrhotite, pyrite, chalcopyrite, and minor galena), calcite, and traces of quartz; and (4) a chlorite–calcite stage mainly characterized by the formation of chlorite, calcite, and traces of sericite. Exsolution of droplet-like and patchy chalcopyrite is developed within sphalerite of the sulfide stage, indicating an exsolution temperature of 350–400°C. As such, the crystallization temperature of early stage magnetite may have been >400°C. Abundant fluid inclusions occur in calcite, which include daughter-mineral-bearing H2O, H2O, and pure H2O inclusions. The H2O inclusions have a wide range of homogenization temperatures from 147°C to 367°C with salinities of 2.4–23.4wt.% NaCl equivalent. The daughter-mineral-bearing H2O inclusions have homogenization temperatures from 172°C to 347°C with salinities of 31.9–33.0wt.% NaCl equivalent. Using the chlorite geothermometer, the temperature of chlorite formation is constrained to be between 152°C and 222°C (average=194°C). Sulfur isotope compositions of pyrrhotite, sphalerite, pyrite, and loellingite have a narrow range of δ34S values from 3.8‰ to 8.1‰ (average δ34S=6.8‰), suggesting that the sulfur was magmatic-derived. Zircon LA–ICP-MS U–Pb dating of wall rock dacite yields a weighted mean 206Pb/238U age of 316.0±1.7Ma. Combined with previous dating results of magnetite-mineralized diorite stocks, diorite dikes, and garnet skarn, it can be inferred that the Dunde iron–zinc deposit formed in the late Carboniferous after 316Ma and is genetically related to deep dioritic intrusions. During the late Carboniferous, the tectonic setting of this region changed from subduction–collision to extension, accompanied by mantle-derived magma underplating in deep. After the formation of the iron–zinc ore deposit, the Dunde district was intruded by an early Permian K-feldspar granite that yields a zircon LA–ICP-MS U–Pb age of 295.75±0.71Ma.

The Basil Cu–Co deposit, Eastern Arunta Region, Northern Territory, Australia: A metamorphosed volcanic-hosted massive sulphide deposit

The Basil Cu–Co deposit, Harts Range, central Australia, is hosted by the Riddock Amphibolite, a sequence that has been metamorphosed at upper-amphibolite- to granulite-facies conditions at 480–460Ma (Larapinta Event), and subsequently reworked at amphibolite-facies conditions (450–300Ma). As a result, many of the primary mineralization textures and other features that could characterise ore genesis have been obliterated. However, preserved textures and mineral relationships in the mineralized zone, allow some constraints to be placed on the genetic history of the deposit using mineralogical, petrographic and geochemical studies of host rocks and sulphides.Results of this study permit at least two genetic models to be ruled out. Firstly, whole rock geochemistry and garnet compositions suggest that the deposit is not a skarn system. Secondly, the lack of any significant Ni-signature, and the presence of abundant zircons in the host amphibolite (indicating that not all host rocks are mafic in composition and/or magmatic in character), make an orthomagmatic Ni–Cu–(PGE) system unlikely. Alternatively, Basil is assigned to a volcanic-hosted massive sulphide (VHMS)-style of mineralization, formed on the seafloor, within basaltic and sedimentary host rocks, typical of deposits occurring in such settings. The lack of a recognisable hydrothermal alteration zone is consistent with either destruction of the alteration zone during metamorphism or detachment of the ore from alteration during later deformation.The occurrence of sulphide inclusions within garnet and amphibole indicates that the sulphides must be syn-metamorphic or earlier. Partitioning of trace elements between pyrite and co-existing pyrrhotite suggests that (re)crystallization occurred under equilibrium conditions. The composition of sphalerite coexisting with pyrite and pyrrhotite indicates crystallization at pressures of at least 10kbar, consistent with peak metamorphism during the Early Ordovician Larapinta Event. Zr-in-titanite geothermometry indicates peak temperatures of 730–745°C.

당두 연-아연 광상의 산출광물과 화학조성

The Dangdu Pb-Zn deposit is located at approximately 10 km south of Jecheon, Korea. Geology of Dangdu deposit area consists of Pre-cambrian metamorphic rocks, Ordovician sedimentary rocks, Jurassic and Cretaceous igneous rocks. The ore deposit is developed along the fracture trending in Ordovician limestone and is considered to be a skarn type ore deposit. The shape of ore bodies developed in the Dangdu ore deposit can be divided into lens-form(two ore bodies of -30 m level adit and one ore body of -63 m level adit) and pocket-form developed in -30 m level adit. Ore minerals observed in the ore deposits are magnetite, pyrrhotite, pyrite, chalcopyrite, sphalerite, galena, cosalite, marcasite, hessite, native Bi and bismuthinite. Chemical composition of sphalerite ranges FeS 14.14~18.08 mole%, CdS 0.44~0.70 mole%, MnS 0.52~1.13, 1.53~2.09 mole%. Galena contains a small amount of silver with an average of 0.54 wt.%. An average composition of cosalite is Ag 2.43 wt.%, Bi 44.36 wt.%, Pb 35.05 wt.% which results the chemical formula of cosalite as . Skarn minerals consist of epidote, garnet, pyroxene, tremolite, quartz and calcite. The zoning pattern of the ore deposit can be subdivided into epidote-clinopyroxene zone, epidote-clinopyroxene-chlorite zone and epidote-garnet-clinopyroxene zone from the central part of the ore body towards the wall rocks. The chemical composition of garnet shows an increasing trend of grossular from epidote-clinopyroxene zone to epidote-garnet-clinopyroxene zone. Clinopyroxene occurs as a solid solution of diopside and hedenbergite, and the ratio of johannsenite increases from epidote-clinopyroxene zone to epidote-clinopyroxene-chlorite and epidote-garnet-clinopyroxene zones. The mineralization of the ore deposit is considered to be one stage event which can be separated into early skarn mineralization stage, middle ore mineralization stage and late low temperature mineralization stage. The temperature estimation from the low temperature mineralization range from which is considered to be representing the temperature of late mineralization.

Source characteristics and fluid evolution of the Beiyingxigou Pb–Zn–Ag deposit, central North China Craton: An integrated stable isotope investigation

The Beiyingxigou quartz vein and alteration type Pb–Zn–Ag deposit forms part of the metallogenic region southwest of the Mapeng batholith in the Central North China Craton. The quartz vein-type polymetallic deposit is associated with intermediate-felsic intrusives emplaced with Mesoarchean metamorphic basement. The mineralization is dominantly controlled by N–S and NW–SE trending faults. We identify four distinct stages of mineralization associated with the hydrothermal activity: pyrite phyllic stage, quartz–pyrite stage, quartz–polymetallic sulfide stage, and quartz–carbonate stage. Among these, the first two stages and the quartz–polymetallic sulfide stage represent the early and main metallogenic stages, respectively. Here we present results from integrated stable isotope studies (S, Pb, He–Ar and H–O) to deduce the possible sources of the mineralizing fluids and metals. The δ34S values recorded in the sulfide minerals of the early and main metallogenic stages show ranges of +0.4‰ to +2.2‰, and −11.4‰ to −6.8‰, respectively. The data illustrate two distinct pulses of hydrothermal fluids with δ34S mean values of 1.1‰ and −8.7‰. The S isotopes of pyrite and galena, sphalerite from the early and main metallogenic stages suggest a mixed source from the Mesozoic magmatism and the Precambrian basement. We infer that the slow cooling magma at the main metallogenic stage led to a larger interaction with the country rocks and resultant contamination, as compared to the early–middle metallogenic stage. The lead isotopic composition of pyrite, galena and sphalerite from the early to main stages shows restricted ranges with 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 15.720–16.275, 15.068–15.140 and 38.688–41.316, respectively. The data are all characterized by lower crustal nature, suggesting the contribution of Pb from both the Mesozoic intrusions and the basement rocks in the region. The 3He/4He and 40Ar/36Ar ratios of fluid inclusions from the Beiyinxigou Pb–Zn–Ag deposit show a range of 0.01–0.23 Ra and 270.2–298.1, respectively. The 4He and 40Ar concentrations vary from 26.6 to 340.6 (10−7cm3STP/g) and 165.6 to 357.9 (10−7cm3STP/g), respectively, suggesting dominantly crustal contribution. The δ18OQ values of quartz and the δ18Dw values show ranges of 10.9‰ to 13.6‰ and −85.2‰ to −57.8‰, respectively. The calculated δ18OW values of the mineralizing fluids show a range of 3.7‰ to 7.5‰. Our data suggest that the hydrothermal fluids were a mixture of both magmatic and meteoric water. The results presented in this study link the Beiyinxigou Pb–Zn–Ag deposit to metallogeny associated with Mesozoic magmatism in the North China Craton.

Microfabrics and microchemistry of sulfide ores from the 640 FW-E level at the Al Amar gold mine, Saudi Arabia

In a VMS ore at Al Amar gold mine (level 640 FW-E), sulfide minerals are paragenetically ordered as follows: pyrite(I)–sphalerite–chalcopyrite–galena–pyrite(II), deformations vary from brittle to ductile deformation fabrics. Microscopically, the massive sulfides have pyrite porphyoblasts (up to ∼80%) that show evidence of creep dislocation as a result of low-temperature plastic deformation rather than brittle failure, whereas high-temperature annealment is completely lacking. Softer minerals such as chalcopyrite fill into fractures in pyrite as narrow slivers. Needle-shaped or lamellar morphology of chalcopyrite, together with the chemical composition of Fe-poor sphalerite (with maximum 0.99wt% Fe) suggest a combined replacement–coprecipitation mechanism of chalcopyrite disease formation rather than an exsolution texture. Greenschist facies metamorphism produces an ore with distinct chalcopyrite disease into a stratified ore with microbands of chalcopyrite and sphalerite. Ore microfabrics and uncommon occurrence of epithermal stringers suggest noticeable effect of the Najd tectonics in the studied level. The EMPA analyses indicate that all sulfide minerals in the VMS ore are auriferous and the Au contents are considerable (up to 0.94, 1.31, 0.16 and 1.20wt%; in sphalerite, chalcopyrite, galena and pyrite, respectively). Gold in pyrite is “invisible” whereas it occurs as submicroscopic inclusions in sphalerite, chalcopyrite and galena. The VMS ore of Al Amar deep horizons are characterized by the occurrence of “invisible gold”, Ag-free galena, Fe- and Ni-poor sphalerite, negligible hydrothermal alteration, plastic deformation of pyrite and non-exsolution origin of the chalcopyrite disease intergrowth which are together strong indicators of low-temperature (250–300°C).

Lead isotope geochemical characteristics of Pb-Zn-Cu deposits on the southwestern margin of Tarim, and their significance

The polymetallic (Pb, Zn, Cu, etc) ore belt on the southwestern margin of Tarim is one of the major regions with the greatest prospecting potential in Xinjiang. Reported in this paper are the lead isotope data for 66 sulfide samples (including 50 galena samples, 15 chalcopyrite samples and 1 pyrite sample) collected from such representative deposits as Tamu, Tiekelike, Kalangu, Abalieke, etc. in this ore belt. The Pb isotopic ratios of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb in the galena samples range from 17.931 to 18.176, 15.609 to 15.818 and 38.197 to 38.944, with the average values of 18.017, 15.684 and 38.462, respectively. Those in the chalcopyrite samples range from 17.926 to 18.144, 15.598 to 15.628 and 38.171 to 38.583, with the average values of 18.020, 15.606 and 38.262, respectively. The pyrite sample has the Pb isotopic ratios of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb to be 17.980, 15.604 and 38.145, respectively. In combination with the previous Pb isotope data for sulfides, it is found that there is only a slight variation in the Pb isotopic composition of galena, chalcopyrite, sphalerite and pyrite in the ore belt. However, there is some difference in Pb isotopic characteristics between galena and chalcopyrite, especially the Pb isotopic composition of galena shows an obvious linear correlation with some other relevant parameters (e.g. Δβ and Δγ). The comprehensive analysis suggested that lead in galena (maybe including sphalerite and pyrite) was derived principally from wall rocks and underlying basement, and that in chalcopyrite only originated from the basement. The single-stage model ages of these sulfides couldn’t indicate the time limit of metallogenesis (Pb, Zn, Cu, etc.), and the positive linear correlations for the Pb isotopic composition of galena are of no single-stage and two-stage Pb-Pb isochron significance. Furthermore, there are significant differences in Pb isotopic composition characteristics between the genetic type of deposits in this polymetallic ore belt and the Mississippi Valley type (MVT). In addition, the authors also pointed out that there is a phenomenon of differentiation (not paragenesis) for lead and copper elements during the process of metallogenesis in this ore belt.

Computer simulation in hydrothermal systems with allowance for nonideality of sphalerite and pyrrhotite

To enhance the computer simulation of hydrothermal processes using the HCh program package, an external ZnS_FeS module has been created on the basis of a nonideal asymmetric model of sphalerite solid solution. FeS and ZnS activity coefficients computed in line with this model within a temperature range 200–350°C lead to the decrease in FeS mole fraction (XFeS) in sphalerite by 3.0–1.5 times as compared with the ideal model. The calculated data on composition of sphalerite at the pyrite-pyrrhotite buffer with allowance for pyrrhotite nonideality are consistent with experimental results within the limits of 2% XFeS of its value (0.215). A nonlinear relationship logXFeS versus \(\left( {\log f_{S_2 } } \right)\). has been established, involving additional calculated data on equilibria of sphalerite with pyrite and magnetite, as well as pyrite and barite. With transition from pyrrhotite to magnetite and barite, a FeS mole fraction in sphalerite decreases to 0.1 and 0.006, respectively, because of increase in sulfur fugacity. The feasibility of using the calculation results based on the nonideal model of sphalerite for interpretation of natural data is exemplified in the Rainbow ore occurrence at the Mid-Atlantic Ridge (MAR). The computed pyrite-pyrrhotite and pyrite-cubanite-chalcopyrite buffer equilibria (XFeS = 0.215 and 0.10–0.12, respectively) are consistent with compositions of sphalerite in the pyrrhotite-cubanite-sphalerite and sphalerite ores (XFeS = 0.20–0.33 and 0.05–0.14, respectively).

Influence of nanosecond electromagnetic pulses on phase surface composition, electrochemical, sorption and flotation properties of chalcopyrite and sphalerite

The mechanism for the powerful nanosecond electromagnetic pulse (MNEMP) effect on the phase composition of new-formed chalcopyrite and sphalerite structures is studied by IR Fourier spectroscopy method. The authors establish the effect of the higher sorption activity of sulfide minerals subjected to the electromagnetic pulse treatment. The research data are confirmed by the experimental data on MNEMP effect on electrochemical and flotation properties of chalcopyrite and sphalerite.

Geology, ore facies and sulphur isotopes of the Koushk vent-proximal sedimentary-exhalative deposit, Posht-e-Badam Block, Central Iran

The Koushk zinc–lead deposit in the central part of the Zarigan–Chahmir basin, central Iran, is the largest of several sedimentary–exhalative (SEDEX) deposits in this basin, including the Chahmir, Zarigan, and Darreh-Dehu deposits. The host-rock sequence consists of carbonaceous, fine-grained black siltstone with interlayered rhyolitic tuffs. It corresponds to the upper part of the Lower Cambrian volcano-sedimentary sequence that was deposited on the Posht-e-Badam Block due to back-arc rifting of the continental margin of the Central Iranian Microcontinent. This block includes the late Neoproterozoic metamorphic basement of the Iran plate, overlain by rocks dating from the Early Cambrian to the Mesozoic. Based on ore body structure, mineralogy, and ore fabric, we recognize four different ore facies in the Koushk deposit: (1) a stockwork/feeder zone, consisting of a discordant mineralization of sulphides forming a stockwork of sulphide-bearing dolomite (quartz) veins cutting the footwall sedimentary rocks; (2) a massive ore/vent complex, consisting of massive replacement pyrite, galena, and sphalerite with minor arsenopyrite and chalcopyrite; (3) bedded ore, with laminated to disseminated pyrite, sphalerite, and galena; and (4) a distal facies, with minor disseminated and laminated pyrite, banded cherts, and disseminated barite. Carbonatization and sericitization are the main wall-rock alterations; alteration intensity increases towards the feeder zone. The δ34S composition of pyrite, sphalerite, and galena ranges from +6.5 to +36.7‰. The highest δ34S values correspond to bedded ore (+23.8 to +36.7‰) and the lowest to massive ore (+6.5 to + 17.8‰). The overall range of δ34S is remarkably higher than typical magmatic values, suggesting that sulphides formed from the reduction of seawater sulphate by bacteriogenic sulphate reduction in a closed or semi-closed system in the bedded ore, whereas thermochemical sulphate reduction likely played an important role in the feeder zone. Sulphur isotopes, along with sedimentological, textural, mineralogical, and geochemical evidences, suggest that this deposit should be classified as a vent-proximal SEDEX ore deposit.