δ34S Values Of Sulfide Minerals Research Articles

Genesis of the Ulaan silver-lead–zinc deposit in Northeast Mongolia: Constraints from S and Pb isotopes, together with U-Pb and Rb-Sr geochronology

The Ulaan silver-lead–zinc deposit (hereinafter referred to as the Ulaan deposit) is identified as the largest silver-lead–zinc polymetallic deposit in Mongolia, with proved reserves including 2,240 tons of silver (Ag; average grade: 49 g/t), 440,000 tons of lead (Pb; average grade: 1.13 %), and 810,000 tons of zinc (Zn; average grade: 2.07 %). However, the genesis of this deposit remains unclear. The Ag-Pb-Zn ore bodies in the deposit, occurring as cylinders in shape within the Middle-Late Jurassic rhyolites, are governed by a concealed breccia pipe. The ore minerals include galena, sphalerite, and pyrite, followed by chalcopyrite, hematite, stibnite, and siderite. The primary alterations of the surrounding rocks include silicification, chloritization, kaolinization, argillization, carbonatization, and skarnization. The Rb-Sr dating of sulfide minerals and associated vein minerals in the ores yielded isochron ages varying in a range of 146 ± 3 Ma (n = 6, MSWD=1.3), suggesting mineralization during the Late Jurassic. The δ34S values of sulfide minerals in the ores range from 1.6 ‰ to 4.3 ‰, suggesting that the sulfur originated primarily from magmas or deep sources. The isotopic compositions of coexisting sphalerite-galena minerals in the deposit revealed mineralization temperature estimates ranging between 331 °C and 449 °C, indicating a medium- to high-temperature ore-forming conditions. The sulfide minerals exhibit 208Pb/204Pb ratios ranging from 38.138 to 38.301, 207Pb/204Pb ratios from 15.543 to 15.594, and 206Pb/204Pb ratios from 18.318 to 18.354, suggesting that ore-forming metals, represented by Pb, also originated primarily from mantle source. The zircon U-Pb dating of rhyolites in the ore-hosting strata and ore-controlling breccia pipes yielded ages of 160.6 ± 1.7 Ma (n = 24, MSWD=0.68) and 161.6 ± 1.6 Ma (n = 30, MSWD=0.89), respectively, indicating volcanic eruptions during the early Late Jurassic. These ore-hosting rhyolites exhibit characteristics of A-type rhyolites, suggesting that they were formed in an intracontinental extensional environment. These rhyolites share similar rare earth element (REE) distribution patterns with fluorite formed in the main mineralization stage, suggesting a genetic link between the mineralization and magmatic processes. This study proposes that the Ulaan deposit was a hydrothermal deposit formed in an extensional environment following the closure of the Mongol-Okhotsk Ocean, with ore-forming metals and hydrothermal fluids associated with volcanic rocks or magmatic-hydrothermal processes.

Barite Replacement as a Key Factor in the Genesis of Sediment-Hosted Zn-Pb±Ba and Barite-Sulfide Deposits: Ore Fluids and Isotope (S and Sr) Signatures from Sediment-Hosted Zn-Pb±Ba Deposits of Iran

Iran hosts more than 350 Precambrian to Cenozoic sediment-hosted Zn-Pb±Ba and barite-sulfide deposits, including shale-hosted massive sulfide (SHMS, also called SEDEX) and Irish-type and Mississippi Valley-type (MVT) mineralization, and barite is a common mineral in these deposits. In the SHMS deposits, barite is typically found as fine-grained disseminations in thin laminae. In these deposits, the sulfide laminae often occur as diagenetic replacements and as bands containing authigenic and diagenetic barite and pyrite framboids. In the Irish-type Zn-Pb-Ba and stratabound barite-sulfide deposits, barite exhibits various textures, including fine-grained disseminated barite, banded zebra textures, veins, and massive barite lenses. In some of the giant Irish-type deposits, as well as in the stratabound barite-sulfide mineralization, the main stratabound sulfide ore is developed within a barite envelope and is characterized by the replacement of barite and pyrite by chalcopyrite, galena, and sphalerite. In the MVT deposits, the formation of barite is often related to dolomitization, and sulfide mineralization involves the replacement of the dolomitized carbonate rocks, as well as associated barite. Fluid inclusion studies on the Irish-type deposits indicate that the temperatures and salinities of the sulfide-forming fluids are higher compared to those of the barite-forming fluids. Fluid inclusion analyses of coarse-grained barites from Irish and MVT deposits reveal their hydrothermal origin. The δ3⁴S values of sulfide minerals (pyrite, sphalerite, and galena) in Irish-type deposits exhibit a broad range of low values (mostly −28 to +5‰), primarily revealing a process of bacterial sulfate reduction (BSR). However, the textures (replacement, colloform, and banded) and more positive sulfur isotope values (+1 to +36‰) in the SHMS Zn-Pb deposits suggest that bacterial sulfate reduction (BSR) plays a less significant role. We suggest that thermochemical sulfate reduction (TSR) connected to the direct replacement of barite plays a more relevant role in providing sulfur for the sulfide mineralization in the SHMS, barite-sulfide, and MVT deposits. Based on the textual evidence, sulfur isotopic data, and fluid inclusion studies, barite has been identified as a key controller for the subsequent Zn-Pb mineralization by providing a suitable host and significant sulfur contribution in the sediment-hosted Zn-Pb and stratabound barite-sulfide deposits. This implies that diagenetic barite might be a precursor to all types of sediment-hosted Zn-Pb mineralization.

Geochemical and mineralogical features as indicators of sulfate-methane transition zones in shallow gas-bearing offshore sediments from Zhoushan

Subsurface shallow gas, primarily composed of biogenic methane (>95%), is highly-enriched in global offshore sediments. The redox conditions of methane-rich pore fluid play a crucial role in shaping the geochemical signatures associated with the anaerobic oxidation of methane (AOM) and vertical displacement of sulfate-methane transition zones (SMTZs) within deep sedimentary records. However, long-period, and continuous records of AOM and SMTZs in shallow gas-bearing offshore sediments are sparse. Here, we employed a comprehensive analyses of iron sulfide, elemental, and stable isotopies on a 63-m drilled sediment core (JC-1) from offshore Zhoushan. Four different layers U1–U4 were identified in 11.5–24 mbsf, 24−42 mbsf, 42−51 mbsf, and 51−63 mbsf, respectively, as revealed by the lithofacies and sedimentary structures. By comparing the pyrite contents, total sulfur to total organic carbon ratios, and δ34S-chromium-reducible sulfur values, the commonly seen organoclastic sulfate reduction occurred in U1 and U2, whereas significant AOM activities were found in U1 and U4. Further, the peaks of total sulfur to total organic carbon ratios, sulfur contents, and multiple positive δ34S-chromium-reducible sulfur values indicated the presence of AOM in SMTZs at 18.3, 52, and 59 mbsf. These intervals were featured by a sub-oxic or anoxic condition with strong methane seepages, evident from the scarcity of metals and the enrichment of Mo/Al and U/Al ratios. The presence of multiple SMTZs was consistent with the pore-water data of the adjacent YS4 and YS7 cores. In light of these findings, it is prudent to exercise caution when utilizing geochemical indicators, such as trace element proxies and the δ34S values of sulfide minerals, to comprehend the progression of fluctuating depositional settings in reaction to sea-level fluctuations and shallow gas reservoirs. This study provides a new perspective to better understand the evolution of unsteady depositional environments in response to sea-level changes and shallow gas reservoirs.

Sulfur isotopic systematics of hydrothermal precipitates in the Okinawa Trough: Implication for the effect of sediments and magmatic volatiles

The Okinawa Trough is a sediment-covered intra-continental back-arc basin with active hydrothermal activities. The sulfur isotopic systematics of the hydrothermal systems in the Okinawa Trough remain unclear owing to the complex sulfur reservoirs. To address these uncertainties, we conducted in situ S isotopic combined with whole-rock geochemical, Pb isotopic, and barite Sr isotopic analyses of typical hydrothermal precipitates from three hydrothermal fields with varying sediments thickness (Iheya North Knoll (INK) < Yonaguni Knoll IV (YK) < Noho) in the Okinawa Trough. The δ34S values of barite from INK (+16.4‰ to +19.6‰, median + 18.5‰) and YK (+16.2‰ to +22.2‰, median + 19.5‰) mostly indicate lower values than those obtained for seawater (~ +21‰), combined with the observation of high S and O fugacity (fO2–fS2) mineral assemblages (e.g., low-Fe sphalerite ± enargite ± tennantite ± chalcopyrite), and high Cu and Au contents of hydrothermal precipitates, consistent with the addition of magmatic volatile to these two fields. In contrast, the in situ δ34S values of sulfide minerals from INK (+5.6‰ to +10.4‰, median + 9.0‰) and YK (+3.5‰ to +5.5‰, median + 4.7‰) fields were all positive, inconsistent with the S isotopic characteristics of H2S formed from SO2 disproportionation. We conclude that a large proportion of thermochemical SO42− reduction-derived heavy sulfur likely obscure the characteristics of H2S sourced from disproportionation. This was likely resulting from (1) sediment controlled long-scale lateral hydrothermal circulation, (2) the existence of early precipitated anhydrite, and (3) high concentrations of H2 in the high-temperature reaction zone. The Noho field have low δ34S values (−0.2‰ to +5.3‰, median + 0.9‰) of sulfide minerals, combined with high sediment contributions reflected by high Pb isotopic ratios and low-fS2–fO2 mineral assemblages (e.g., high-Fe sphalerite ± pyrrhotite ± isocubanite), which indicates that the low δ34S value sulfur was derived from leaching of biogenic pyrite in thick sedimentary strata by hydrothermal fluid. Near surface, the high-temperature discharging hydrothermal fluids interacted with different thicknesses of sedimentary strata and leached different proportions of biogenetic pyrite, resulting in a negative correlation of sedimentary strata thickness and sulfide δ34S values of the Okinawa Trough hydrothermal fields.

Episodic Nature of Magmatic Ascent in a Dynamic Conduit System: Evidence From a Late Gabbroic Intrusion Associated with the Eagle Ni-Cu Sulfide Deposit in Northern Michigan, USA

Abstract New exploration studies have revealed a near-vertical, plug-like gabbroic intrusive body emplaced along the feeder conduit of the funnel-shaped Eagle East ultramafic intrusion in the Upper Peninsula of Michigan. U-Pb baddeleyite analysis on this gabbro yielded an age of 1103.4 ± 1.2 Ma. Although a sulfide-deficient gabbro is the principal rock unit, peripheral zones of the intrusion contain feldspathic pyroxenite and melagabbro with minor blebs of chalcopyrite and pyrrhotite. A small pocket-like body of peridotite with significant quantities of sulfide minerals occurs along the edge of the main gabbroic unit. The modes of occurrence of sulfide minerals in the pocket peridotite are similar to the larger Eagle East and Eagle intrusions nearby. The composition of olivine in the main gabbroic rock is Fo24–30, but olivine in pocket peridotite shows a composition of ~Fo74. The Ni-concentration in the olivine of the main gabbro unit is below 100 ppm, but in the Mg-rich olivine of the pocket peridotite, it is between 2,100 and 2,800 ppm. Although δ34S values of sulfide minerals in the pyroxenite rim and in the pocket peridotite range from –0.6 to 7.0‰, the average value is higher than those reported from sulfides in the Eagle East and Eagle intrusions. The origin of the gabbro unit could be explained by a closed-system crystallization of a fractionated late derivative of an original high-MgO magma, while the peridotite pocket is a xenolithic representative of the old peridotitic intrusion dislodged and entrained in a late magmatic pulse.

Genesis of the Erdaohe skarn Pb-Zn-Ag deposit in the Great Hinggan Range, NE China: Evidence from geology, fluid inclusions, and H–O–S isotope systematics

The large Erdaohe Pb-Zn-Ag deposit is an important and representative skarn deposit in the middle segment of the Great Hinggan Range. The Pb-Zn ore bodies are mainly hosted in and among different lithological layers of volcaniclastic and carbonate rocks. The Si–Ca interface with abrupt changes in rock chemical properties and the bedding detachment faults played important roles in controlling mineralization. The mineralization of the deposit can be divided into three stages: (1) pre-ore skarn stage (I); (2) syn-ore quartz–sulfide stage (II); and (3) post-ore quartz–carbonate stage (III). Here, we present a combined study of geology, fluid inclusions (FIs), laser Raman analysis and H–O–S isotopes to constrain the origin and evolution of ore-forming fluids and the source of ore-forming materials. Four types of FIs are identified in the Erdaohe deposit, including liquid-rich (L-type), vapor-rich (V-type), CO2 (C-type) and daughter mineral-bearing (S-type) FIs. The L-type, V-type, C-type and S-type FIs appear simultaneously in stages I and II, and their homogenization temperatures (Th) are similar, indicating that boiling of the ore-forming fluids occurred. From stages I to III, Th varies from 338 to 475 °C, 194 to 383 °C and 157 to 323 °C, with salinities ranging from 3.87 to 50.72 wt% NaCl equiv., 0.35 to 39.05 wt% NaCl equiv. and 0.18 to 6.88 wt% NaCl equiv., respectively. The main ore-forming fluid was a H2O–NaCl ± CO2 system. From stages I to III, the variations in δ18Ofluid range from −2.3 to 7.2‰, −8.8 to 1.0‰, and −13.6 to −3.8‰; the ranges of δD are −141 to −208‰, −133 to −161‰, and −126 to −142‰, respectively. H–O isotope studies reveal that the initial ore-forming fluid was mainly derived from magma and underwent intense degassing, followed by mixing with meteoric water. The δ34S values of sulfide minerals vary in a small range, are concentrated from 5.2 to 10.0‰, and are characteristic of deep-sourced magmatic sulfur. The high δ34S values in the Erdaohe deposit are probably the result of magmatic sulfur mixing with sulfur from the surrounding Duobaoshan Formation. The alteration style related to mineralization, combined with FIs, laser Raman analysis, and H–O–S isotopes, suggests that the Erdaohe Pb-Zn deposit is a typical skarn deposit associated with magmatic activity. The boiling of ore-forming fluids and mixing with meteoric water played crucial roles in ore precipitation.

Ore genesis of Qingyunshan Cu-Au deposit in the Dehua-Youxi area of Fujian Province, southeastern China: Constraints from U-Pb and Re-Os geochronology, fluid inclusions, and H-O-S-Pb isotope data

The Qingyunshan Cu-Au deposit, located in the Dehua-Youxi area (Fujian Province, southeastern China), is a vein-type deposit that occurs along fractured zones in the Late Jurassic volcanic-sedimentary rocks and Early Silurian intrusions. Three mineral paragenetic stages are identified, including the pyrite-quartz veins (stage I), polymetallic sulfide-quartz-calcite veins (stage II), and calcite (±siderite)-chalcedony-comb quartz veins (stage III). The stage II is the main mineralization stage, dominated by pyrite, chalcopyrite, and galena as well as two generations of Fe-poor sphalerite with average Fe content of 0.84 wt% in the early sub-stage and 0.31 wt% in the late sub-stage. Fluid inclusion studies indicate that the stage I has a temperature of 220–240 °C and salinity of 3.00–3.50 wt% NaCleq., whereas the stage II has lower temperature (140–160 °C), but similarly low salinity (2.50–3.00 wt% NaCleq.), suggesting it is an intermediate-low temperature epithermal deposit. Hydrogen and oxygen isotope data indicate the fluids of stage I has a δD value of −72.5 to −69.5‰ and δ18Ow value of −2.96 to −0.46‰, whereas the stage II fluids show similar or slightly higher δD value (−68.0 to −66.5‰), but significantly lower δ18Ow value from −6.96 to −6.26‰, which suggest meteoric water predominated in the ore-forming fluid and shows an increasing trend from stage I to II. The δ34S values of sulfide minerals are between −3.7 and −2.3‰, consistent with a major magmatic sulfur source. The lead isotope data show a relatively narrow range with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of 18.392–18.513, 15.642–15.758, and 38.497–39.043, respectively. These Pb-isotope data are similar to those of the Late Jurassic intrusions, but quite different from those of the surrounding rocks of Early Silurian quartz diorite. Pyrite from the ores yielded a Re-Os isochron age of 158.1 ± 9.3 Ma, which is similar to the zircon U-Pb age (162.0 ± 1.0 Ma) of the host dacite crystal tuff in the Nanyuan Formation. Therefore, we concluded that the Late Jurassic magmatic activity (ca. 160 Ma) has a genetic relation with formation of the Qingyunshan vein-type Cu-Au deposit, for which the ore metals were mainly derived from the magma, but ore-forming fluids evolved from a mixing of magmatic fluids and meteoric water with the later playing a major role in the main stage of ore formation.

Geological, fluid inclusion, and H–O–C–S–Pb isotopic constraints on the genesis of the Shuangqishan gold deposit, Fujian, China

The Shuangqishan Au deposit lies in the Dehua–Youxi–Yongtai Au metallogenic belt in central eastern Fujian Province, SE China. The orebodies are hosted mainly in the Neoproterozoic Dalingyan Formation. Based on the characteristics of mineralization, alteration mineral assemblages, fluid inclusions, and H–O–C–S–Pb isotopic data, the deposit is classified as a granitoid-related deposit. The primary metallic minerals are native gold, electrum, pyrite, chalcopyrite, galena, tellurbimuth, and tetradymite; the main gangue minerals are quartz, calcite, sericite, and illite. The main types of wall-rock alteration are silicification, pyritization, carbonatization, and sericitization. Fluid inclusions in quartz from auriferous polymetallic sulfide-bearing quartz veins from the main ore stage were studied. Two-phase liquid-rich (type I), CO2-rich (type II), and pure CO2 (type III) inclusions were identified. Their homogenization temperatures (196 °C–295 °C) and salinities (0.8–5.0 wt% NaCl equivalent) indicate that the ore-forming fluids of the Shuangqishan deposit were of a medium-temperature, low-salinity H2O–CO2–NaCl system. Gold deposition at Shuangqishan was likely caused by immiscibility of fluids. H isotopic compositions (δDH2O = −68.0‰ to −64.8‰) of inclusion water in quartz and O isotopic compositions (δ18OH2O = 3.8‰ to 6.3‰) of fiuid, which was calculated from δ18O of quartz, imply that ore-forming fluids were mainly of magmatic origin. C isotopic compositions (δ18CPDB = −15.7‰ to −5.7‰) of the fluid inclusions indicate that the CO2 in the ore-forming fluids was predominantly magma-derived, but was contaminated by organic carbon from the Neoproterozoic Dalingyan Formation. δ34S values of sulfide minerals have a narrow range of–2.7‰ to −0.9‰, suggesting that S was derived from a homogeneous magmatic source. Pb isotopic ratios of gold-bearing ores are similar to those of late Mesozoic granodiorite porphyry of the Xianyang pluton, indicating that the granodiorite porphyry was the source of Pb for the ores.

Geochronological, geochemical, and mineralogical characteristics of the Akechukesai-I mafic–ultramafic complex in the eastern Kunlun area of the northern Tibet Plateau, west China: Insights into ore potential

The recently discovered Akechukesai mafic–ultramafic complex is located in the East Kunlun Orogenic Belt, northern Tibet Plateau, China. Two mafic–ultramafic complexes (Akechukesai I and Ⅱ) intrude marble of the Cambrian–Ordovician Tanjianshan Group. Cu–Ni sulfide mineralization occurs in these complexes. Pyroxenite in the Akechukesai-I complex has an age of 422 ± 10 Ma(1σ), similar to that of the Xiarihamu and Shitoukengde Cu–Ni deposits of the East Kunlun area. The positive εHf(t) values (1.7–4.9) and SiO2, TiO2, and Al2O3 contents of clinopyroxene from pyroxenite suggest that the parental magma of the Akechukesai-I complex was derived from depleted mantle composed of garnet lherzolite and spinel lherzolite in varying proportions. Pyroxenite of the Akechukesai-I complex has (87Sr/86Sr)i ratios of 0.70993–0.71405, εNd(t) values of −1.97 to −6.64, (206Pb/204Pb)i ratios of 17.113–18.994, (207Pb/204Pb)i ratios of 15.548–15.673, and (208Pb/204Pb)i ratios of 37.066–38.650, which together indicate a depleted mantle source with 18–35 wt% upper-crustal contamination. δ34S values of sulfide minerals are 5‰–11.5‰ with S/Se ratios of ore-bearing pyroxenite being in the range 3738–15,501, both being higher than mantle values (−2‰ to +2‰ and 2850–4350, respectively) and indicating the addition of crustal S. The incorporation of primitive magma into the marble host during ascent caused a reduction in sulfide solubility owing to increased oxygen fugacity of the magma, leading to S saturation. These observations and the geodynamic setting indicate that the complex is a favorable environment for mineralization.

Genesis of the Huanggoushan Pb–Zn–Au polymetallic deposit in southern Jilin Province, NE China: Constraints from fluid inclusions and C–H–O–S–Pb isotope systematics

The Huanggoushan Pb–Zn–Au deposit is located in the central part of southern Jilin Province in northeastern portion of the North China Craton. It experienced two types of mineralization, namely, stratabound Pb–Zn mineralization placed close to interlayer fracture zones of banded marble and veined Au mineralization controlled by NNE‐trending brittle–ductile shear zones. The Pb–Zn mineralization is characterized by a low‐temperature and low‐salinity H2O–NaCl system of hydrothermal fluids that yielded δD and δ18OH2O values similar to those of meteoric water. The δ34S values of sulfide minerals in the Pb–Zn ores range from 14.8‰ to 17.1‰ with an average of 16.1‰, which reflects a sulfur origin in the seawater sulfate. The sulfur of Pb–Zn ores was most possibly transformed from that of sulfate S6+ into the sulfide S2− by bacteriogenic sulfate reduction processes. Lead isotopic compositions of sulfides separated from the Pb–Zn ores show 206Pb/204Pb ratios from 15.309 to 16.353, 207Pb/204Pb ratios from 15.321 to 15.485, and 208Pb/204Pb ratios from 34.883 to 35.550. By contrast, original medium‐high‐temperature hydrothermal fluids in stage I of the Au mineralization are represented by low‐salinity H2O–CO2–NaCl system with relatively higher δD and δ18OH2O values, which indicates that original ore‐forming fluids were possibly sourced from the Mesozoic magmatic fluids. The δ13C values of fluid inclusions in hydrothermal quartz from Au ores range from −9.6‰ to −2.4‰, most values of which are similar to those of magmas. The sulfides in Au ores have relatively lower δ34S values of 1.0‰ to 8.0‰ than those of sulfides in the Pb–Zn ores. The various δ34S values of sulfides from the Au ores, similar to those of sulfides from the Mesozoic magmatic hydrothermal Au deposits in Heilongjiang—Jilin region, reflect a magmatic sulfur origin. Lead isotopic compositions of sulfides from the Au ores have relatively higher ratios, with 206Pb/204Pb from 17.852 to 20.468, 207Pb/204Pb from 15.591 to 15.833, and 208Pb/204Pb from 37.051 to 38.899. Collectively, geology, fluid inclusions, and isotope geochemistry suggest that ore‐forming fluids of the Pb–Zn mineralization originated from heated seawater with sulfur and lead sourced from seawater sulfate and upper crust, respectively. Thus, the Pb–Zn mineralization can be classified as the Paleoproterozoic SEDEX Pb–Zn category. Whereas, the ore‐forming fluids and sulfur of Au mineralization were of the Mesozoic magmatic origin, with the lead materials from the Paleoproterozoic Zhenzhumen Formation. These features demonstrate that the Au minerlization was closely related to the Mesozoic magmatic‐hydrothermal activity and thus categorized as Mesozoic magmatic hydrothermal Au.

New constraints on the origin of the Maozu carbonate-hosted epigenetic Zn-Pb deposit in NE Yunnan Province, SW China

Micro-scale isotopic compositions determined by micro-beam in situ analysis techniques are expected to provide new information for the understanding of ore genesis. Here we use the Maozu (∼20 Mt of sulfide ore, grading 7.25 wt% Zn and 4.15 wt% Pb) Zn-Pb deposit in the Upper Yangtze Zn-Pb metallogenic province as a case study, utilizing NanoSIMS in situ S, femtosecond LA-MC-ICPMS in situ Pb and conventional bulk Sr isotopes, as well as field data, aimed to reveal its origin and ore formation process. NanoSIMS in situ δ34S values of sulfide minerals from the Maozu deposit have a wider range (+5.9–+20.7‰) than that of bulk δ34S values (+9.9–+19.9‰). Such S isotope signatures reflect the enrichment of heavy S isotopes in ore-forming fluids, and further indicate the source of S is multiple reservoirs (e.g. marine evaporites, coeval seawater, and metamorphic rocks/fluids). Pb isotopic ratios of galena determined by LA-MC-ICPMS in situ techniques have a narrower range (206Pb/204Pb = 18.20–18.21, 207Pb/204Pb = 15.69–15.71 and 208Pb/204Pb = 38.40–38.43) than that of bulk Pb isotopic ratios (206Pb/204Pb = 18.13–18.38, 207Pb/204Pb = 15.64–15.69 and 208Pb/204Pb = 38.22–38.58). This implies that in situ Pb isotopes can truly reflect the source of Pb, which is due to impurities enclosed by sulfide crystals and pollutants introduced by chemical analysis could significantly affect the quality of the bulk Pb isotopic data. Compared with previously reported Pb isotopic data of potential source rocks (i.e. late Permian Emeishan basalts, Paleozoic ore-bearing sedimentary rocks and Proterozoic basement metamorphic rocks), the in situ Pb isotopic data are significantly different from those of basalts, but are similar to those of both basements and sediments. This means that metal-rich fluids were mainly derived from and/or flowed through basements and sediments. Sphalerite separates have initial Sr isotopic ratios (0.711–0.719) that are distinctly different from those of ore formation age-corrected basalts (87Sr/86Sr200 Ma = 0.704–0.708) and basements (87Sr/86Sr200 Ma = 0.724–0.729), whereas partly overlap with those of age-corrected sediments (87Sr/86Sr200 Ma = 0.707–0.714). Such Sr isotope signatures suggest that hydrothermal fluids were predominantly derived from and/or flowed through basements and sediments with a certain influence from basalts. Hence, the Maozu deposit has complex source rocks that are related to the local geological setting. The mixing of metal-rich fluids (related to basements and sediments, and even basalts) and S-bearing fluids (associated with multiple S reservoirs) plays a key role in the formation of sulfide ores. Therefore, the Maozu deposit, formed during Early Mesozoic (∼196 Ma), is an epigenetic Zn-Pb deposit that hosts in carbonate rocks, occurs along fault-fold structures, and has a mixed source of mineralizing elements and associated fluids.

Regional variations of sulfur isotope compositions for metallic deposits in the Taebaeksan Mineralized District, South Korea

Metallic ore deposits of various genetic types are distributed in the Taebaeksan mineralized district in South Korea. The different basements or host rocks for these deposits vary across the northern and southern regions of the district with the Baegunsan Syncline as its center. Previous and newly analyzed sulfur isotope data of 374 sulfide minerals collected from 45 ore deposits were reviewed to compare the genetic characteristics of the two regions. Metallic deposits in the study area were classified into skarn, hydrothermal replacement, and hydrothermal vein based on genetic types and W-Mo, Fe-Cu(-Mo-Pb-Zn), Pb-Zn(-Cu-Au- Ag), and Au-Ag(-Cu-Pb-Zn) deposits with regard to ore species. For each genetic type, average sulfur isotope values were found to be 6.8‰, 7.7‰, and 6.3‰ in the northern region, and 2.3‰, 3.6‰, and 3.5‰ in the southern region, respectively. Average sulfur isotope values for each of the ore species were 11.3‰, 2.6‰, 6.6‰, and 6.9‰ in the northern region, and 1.3‰,–0.2‰, 4.2‰, and 3.3‰ in the southern region, respectively. The results indicate that sulfur isotope compositions for both genetic types and ore species are distinctly higher in the northern region than in the southern region. These differences could be ascribed to different sulfur isotope compositions of basement and host rocks that provided sulfur to ore minerals during the evolution of hydrothermal fluids, though the mineralizing fluids were originated from magmatic source. In the northern region, higher δ34S values of ore sulfurs could be attributed to high δ34S values of sulfate and sulfide in carbonate rocks formed in seawater. On the contrary, lower δ34S values of sulfide minerals in the southern region seem to be attributed to metasedimentary rocks that have lower δ34S values as a result of bacterial sulfate reduction.

Ore genesis of the Fule Pb[sbnd]Zn deposit and its relationship with the Emeishan Large Igneous Province: Evidence from mineralogy, bulk C[sbnd]O[sbnd]S and in situ S[sbnd]Pb isotopes

Magmatic activity plays an important role in mineralization, but little is understood of its role with respect to carbonate-hosted stratabound epigenetic PbZn deposits. The Fule PbZn deposit (~10 Mt of sulfide ore with mean grades of 15–20wt% Zn+Pb), is stratigraphically placed in middle Permian strata and spatially (~1m) associated with late Permian continental flood basalts of the Emeishan Large Igneous Province (ELIP). It thus provides an ideal case to investigate its genetic relationship with the ELIP. In addition, the Fule deposit is characterized by high concentrations of Ag, Cd, Ge and Ga, and contains a variety of Cu and Ni sulfide minerals. Syn-ore calcite (δ13C=+2.57–+3.01‰) and associated fluids (δ13C=+2.96–+3.40‰) have δ13C values similar to those of fresh limestone (δ13C=+1.58–+2.63‰), but the δ18O values of calcite (+16.83–+19.92‰) and associated fluids (+7.80–+10.89‰) are distinctly lower than those of limestone (δ18O=+21.85–+23.61‰). This means that C is mainly derived from limestone, whereas the O isotope signature may be related to water/rock (W/R) interaction between mantle and/or metamorphic fluids and limestone. δ34S values of sulfide minerals obtained by in situ NanoSIMS and conventional bulk techniques record a range of +9.8–+23.1‰ and +10.04–+16.43‰, respectively, reflecting the enrichment of heavy S isotopes in the ore-forming fluids and thermochemical sulfate reduction (TSR) is the principal mechanism for the formation of S2−. Cores of sulfide crystals have much higher δ34S values than their rims, indicating a probable mixture of multiple S reservoirs and/or a dynamic fractionation of S isotopes occurred during sulfide precipitation. The uniform femtosecond (fs) LA-MC-ICPMS in situ Pb isotopic data for galena plot in the field that differs from any of the three potential sources in the region. Such signatures demonstrate that metal Pb was most likely derived from a well-mixed source of basalts, sedimentary rocks and basement rocks. We propose that (a) the enrichment in Ag, Cu, Ni, Cd, Ge and Ga, and the isotope signatures of hydrothermal minerals in the Fule region are related to fluids derived from or flowed through multiple reservoirs; (b) Emeishan magmatism provided heat, elements and associated fluids, and its basalts acted as an impermeable and protective layer; and (c) fluid mixing caused TSR, and then resulted in W/R interaction and CO2 degassing, all of which played a key role in the precipitation of hydrothermal minerals.

Sulfur isotope study of vent chimneys from Upper Cretaceous volcanogenic massive sulfide deposits of the eastern Pontide metallogenic belt, NE Turkey

We obtained sulfur isotope analysis results of sulfide samples from hydrothermal vent chimneys of the eastern Pontide volcanogenic massive sulfide (VMS) deposits. The total range of δ34S values for vent chimneys in the eastern Pontide VMS deposits is -2.7 to 6.5 per mil. Sulfide Δ34S values show narrow variation in the Lahanos, Killik, and Kutlular deposits, but wider variation in the Kizilkaya and Cayeli deposits. The δ34S values of sulfides in Cayeli chimney samples gave a slightly higher range than the other Pontide chimney samples. In some samples, a rough isotopic zonation pattern was observed throughout chimney zones. Variations in δ34S values of sulfides within chimney walls were probably caused by chemical reactions of reprecipitation and replacement between vent fluids and earlier sulfide minerals in the chimney. Ranges of Δ34S values of sulfide minerals are similar for different deposits within the same region. Variations in the δ34S values of the Pontide deposits appear to be geographic rather than stratigraphic. The sulfur isotope values of the deposits have a narrow compositional range, indicative of a fairly specific origin. Although deep-seated sulfur may be a potential source in the Pontide district, a significant contribution of seawater sulfate cannot be ruled out. The δ34S values of selected samples from Pontide vent chimneys are within the range of sulfur values obtained from Phanerozoic VMS deposits. The range is similar to, but slightly broader than, the range of values reported for modern vent chimneys and ancient vent chimneys from the Yaman-Kasy deposit.

Geology and sulfur isotope geochemistry of Dafulou tin-polymetallic deposit in Dachang orefield, Guangxi, China

No. 22 ore of Dafulou deposit was systematically analyzed for sulfur isotopes. The results show that the δ34S values of sulfide minerals, ranging from −0.154 to +0.218% and with an average value of +0.114 1%, are mostly positive and characterized by rich sulfur (S) content. This suggests that the sulfur of the Dafulou ore deposit is derived from magma and relates to the Longxianggai concealed granite, which points to the important role of magma during mineralization and implyies the product of the active continental margin. By comparison between the Dafulou and the Kengma tin deposit, significant differences exist in the sulfur isotope composition. In the Kengma deposit, the sulfur isotope composition is characterized by the high negative value, which is different from the Dafulou tin-polymetallic deposit. The difference of the enrichment and fractionation of the sulfur isotope is the synthesized result of the metallogenic conditions. It also has the difference in the metallogenic environment and metallogenic characteristics of the deposit in the same ore belt.

Reconstruction of Physicochemical Environment of Hydrothermal Mineralization at Malanjkhand Copper Deposit, Central India: Constraints from Sulfur Isotope Ratios in Pyrite, Molybdenite and Chalcopyrite

Abstractδ34S values of pyrite, molybdenite and chalcopyrite were determined from the Malanjkhand copper deposit. These minerals constitute the primary sulfide phases that were deposited after the initial magnetite deposition in the main orebody and host granitoid. Pyrite exhibits a depleted range of values (−2.63 to −0.56‰), chalcopyrite, a very narrow range of values around zero (−0.039 to 0.201‰) and molybdenite furnishes a range of enriched values (0.68 to 1.98‰). On back calculation of the δ34S values of H2S in the fluid from which the minerals were likely to have precipitated, using standard expressions for equilibrium fractionation at the temperature range obtained from fluid inclusion and mineral fluid equilibria, it is observed that H2S in the fluid at pyrite deposition was depleted and gradually became enriched towards molybdenite and chalcopyrite deposition. This trend is best explained as being due to inorganic reduction of SO42− in the fluid and is very much in agreement with the paragenetic sequence indicating increasing activity of H2S in the fluid. The very restricted range in the δ34S values of sulfide minerals in the fluid does indicate a single, possibly magmatic, source of sulfur that also agrees well with the earlier deduced model of genesis of the deposit as an ancient geothermal system associated with granitic magmatism.

Pingüino In-bearing polymetallic vein deposit, Deseado Massif, Patagonia, Argentina: characteristics of mineralization and ore-forming fluids

The Pingüino deposit, located in the low sulfidation epithermal metallogenetical province of the Deseado Massif, Patagonia, Argentina, represents a distinct deposit type in the region. It evolved through two different mineralization events: an early In-bearing polymetallic event that introduced In, Zn, Pb, Ag, Cd, Au, As, Cu, Sn, W and Bi represented by complex sulfide mineralogy, and a late Ag–Au quartz-rich vein type that crosscut and overprints the early polymetallic mineralization. The indium-bearing polymetallic mineralization developed in three stages: an early Cu–Au–In–As–Sn–W–Bi stage (Ps1), a Zn–Pb–Ag–In–Cd–Sb stage (Ps2) and a late Zn–In–Cd (Ps3). Indium concentrations in the polymetallic veins show a wide range (3.4 to 1,184 ppm In). The highest indium values (up to 1,184 ppm) relate to the Ps2 mineralization stage, and are associated with Fe-rich sphalerites, although significant In enrichment (up to 159 ppm) is also present in the Ps1 paragenesis associated with Sn-minerals (ferrokesterite and cassiterite). The hydrothermal alteration associated with the polymetallic mineralization is characterized by advanced argillic alteration within the immediate vein zone, and sericitic alteration enveloping the vein zone. Fluid inclusion studies indicate homogenisation temperatures of 308.2–327°C for Ps1 and 255–312.4°C for Ps2, and low to moderate salinities (2 to 5 eq.wt.% NaCl and 4 to 9 eq.wt.% NaCl, respectively). δ34S values of sulfide minerals (+0.76‰ to +3.61‰) indicate a possible magmatic source for the sulfur in the polymetallic mineralization while Pb isotope ratios for the sulfides and magmatic rocks (206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 17.379 to 18.502; 15.588 to 15.730 and 38.234 to 38.756, respectively) are consistent with the possibility that the Pb reservoirs for both had the same crustal source. Spatial relationships, hydrothermal alteration styles, S and Pb isotopic data suggest a probable genetic relation between the polymetallic mineralization and dioritic intrusions that could have been the source of metals and hydrothermal fluids. Mineralization paragenesis, alteration mineralogy, geochemical signatures, fluid inclusion data and isotopic data, confirm that the In-bearing polymetallic mineralization from Pingüino deposit is a distinct type, in comparison with the well-known epithermal low sulfidation mineralization from the Deseado Massif.

The role of the Kupferschiefer in the formation of hydrothermal base metal mineralization in the Spessart ore district, Germany: insight from detailed sulfur isotope studies

The Spessart district (SW Germany), located at the southwestern margin of the Permian Kupferschiefer basin in Central Europe, hosts abundant stratabound and structurally controlled base metal mineralization. The mineralization styles identified are (1) stratabound Cu-Pb-Zn-(Ag) ores in Zechstein sedimentary rocks, (2) structurally controlled Cu-As-(Ag) ores in Zechstein sedimentary rocks, (3) crosscutting Co-Ni-(Bi)-As and Cu-Fe-As veins, (4) stratabound metasomatic Fe-Mn carbonate ores in Zechstein dolomite, (5) barren barite veins, and (6) Fe-Mn-As veins in Permian rhyolites. Building on previous work that involved mineralogical, textural, and chemical characterization of the major mineralization types, we have performed a comprehensive sulfur isotope study that applied both conventional and novel laser-ablation multi-collector inductively coupled plasma mass spectrometry techniques. The δ34S values of sulfide minerals from the different ore types are consistently negative and highly variable, in the range between −44.5‰ and −3.9‰, whereas the δ34S values of barite are all positive in the range between 4.7‰ and 18.9‰. Remarkably, stratabound and structurally controlled mineralization in Zechstein sedimentary rocks has the least negative δ34S values, whereas vein-type deposits have consistently more negative δ34S values. The observed pattern of sulfide δ34S values can be best interpreted in terms of fluid mixing at the basement-cover interface. Hydrothermal fluids originating from the crystalline basement migrated upward along subvertical fault zones and were periodically injected into groundwaters that were flowing in the post-Variscan sedimentary cover. These groundwaters had interacted with the Zechstein sedimentary rocks, resulting in fluids characterized by elevated concentrations of reduced sulfur (with negative δ34S values) and alkaline pH. Repeated mixing between both chemically contrasting fluids caused rapid and efficient precipitation of sulfide ore minerals in hydrothermal veins with highly variable but distinctly negative δ34S values.

Mineralogical, petrological, and geochemical studies of the Limahe mafic–ultramatic intrusion and associated Ni–Cu sulfide ores, SW China

The Limahe Ni–Cu sulfide deposit is hosted by a small mafic–ultramafic intrusion (800 × 200 × 300 m) that is temporally associated with the voluminous Permian flood basalts in SW China. The objective of this study is to better understand the origin of the deposit in the context of regional magmatism which is important for the ongoing mineral exploration in the region. The Limahe intrusion is a multiphase intrusion with an ultramafic unit at the base and a mafic unit at the top. The two rock units have intrusive contacts and exhibit similar mantle-normalized trace element patterns and Sr–Nd isotopic compositions but significantly different cumulus mineralogy and major element compositions. The similarities suggest that they are related to a common parental liquid, whereas the differences point to magma differentiation by olivine crystallization at depth. Sulfide mineralization is restricted to the ultramafic unit. The abundances of sulfides in the ultramafic unit generally increase towards the basal contacts with sedimentary footwall. The δ34S values of sulfide minerals from the Limahe deposit are elevated, ranging from +2.4 to +5.4‰. These values suggest the involvement of external S with elevated δ34S values. The mantle-normalized platinum-group element (PGE) patterns of bulk sulfide ores are similar to those of picrites associated with flood basalts in the region. The abundances of PGE in the sulfide ores, however, are significantly lower than that of sulfide liquid expected to segregate from undepleted picrite magma. Cr-spinel and olivine are present in the Limahe ultramafic rocks as well as in the picrites. Mantle-normalized trace element patterns of the Limahe intrusion generally resemble those of the picrites. However, negative Nb–Ta anomalies, common features of contamination with the lower or middle crust, are present in the intrusion but absent in the picrites. Sr–Nd isotopes suggest that the Limahe intrusion experienced higher degrees of contamination with the upper crust than did the picrites. The results of this study permit us to suggest that the parental magma of the Limahe intrusion was derived from picritic magma by olivine fractionation and contamination in a staging chamber at mid-crustal levels. Depletion of PGE in the sulfide ores in the Limahe intrusion is likely due to previous sulfide segregation of the parental magmas in the staging chamber. Sulfide mineralization in the Limahe intrusion is related to second-stage sulfide segregation after the fractionated magmas acquired external S from pyrite-bearing country rocks during magma ascent to the Limahe chamber. The abrupt change in mineralogical and chemical compositions between the ultramafic unit and the overlying unit suggests that at least two separate pulses of magma were involved in the development of the Limahe intrusion. We propose that the Limahe intrusion was once a wider part of a dynamic conduit that fed magma to the overlying subvolcanic dykes/sills or lavas. The ultramafic unit formed by the first, relatively more primitive magma, and the mafic unit formed by the second, relatively more fractionated magma. Immiscible sulfide droplets that segregated from the first magma settled down with olivine crystals to form the sulfide-bearing, olivine-rich rocks in the base of the intrusion. The overlying residual liquids were then pushed out of the chamber by the second magma. Critical factors for the formation of an economic Ni–Cu sulfide deposit in such a small intrusion include the dynamic petrologic processes involved and the availability of external sulfur. The Limahe deposit reminds us that small, multiphase, mafic–ultramafic intrusions in the region should not be overlooked for the potential of economic Ni–Cu sulfide deposits.

Rare-Earth-Element and Isotopic Evidence for the Genesis of the Bajiazi Stratabound Sulfide Ore Bodies of Northeast China

This study examines the rare-earth-elemenl and isotopic geochemistry of sulfide ores and associated rocks in the Bajiazi sulfide deposits of northeastern China. The distribution and concentration of rare earth elements (REE) in sulfide ores and associated rocks from the Bajiazi deposits have been determined by inductively coupled plasma spectroscopy (ICP) methods. Birdwing-shaped rare-earth-element profiles are only observed in granitic rocks at Bajiazi. Diverse rare-earth-element profiles of the ores and dolostones are different from those of granite and are interpreted to reflect an early sedimentary-diagenetic mineralization stage during which rare earth elements were added to the ores and host rocks. The characteristic features of the abundances of REE in the Bajiazi samples, including granite and sedimentary host rocks, are demonstrated by a variety of Eu anomalies in the chondrite-normalized REE pattern. Eu is the most mobile element, exhibiting increasingly negative anomalies in granite rock samples relative to the depletion of the sulfide ores and associated sedimentary host rocks, which are considered to be caused by preferential scavenging of Eu from sea water to sediments. The δ34S values of sulfide minerals at Bajiazi generally range from −12.3 to 14.2%, suggesting reduction both of marine sulfate and biogenic sources. The δ34S values from different ore types, sulfide minerals, and mines indicate a sedimentary exhalative origin, although they were, to some extent, homogenized during late overprinting. The late-stage sulfides from Bajiazi are isotopieally remarkably homogeneous and are significantly, although slightly, enriched in δ34S. These results imply multiple sources of sulfur derived from biogenic reduction, and/or sulfate in oceanic and/or connate waters, or from marine evaporites, and/or from magmatic hydrothermal sources. Isotopic temperatures from intersulfide fractionations (pyrite, sphalerite, and galena) range from 75° to 542°C, indicating the Bajiazi sulfide minerals have experienced different mineralizing stages. Galena in the Bajiazi Proterozoic sediment-hosted Pb-Zn sulfide deposits has a very uniform Pb-isotope composition, with 206Pb/204Pb = 16.07 to 16.58, 207Pb/204Pb = 15.00 to 15.66, and 208Pb/204Pb = 36.13 to 36.92, suggesting that it all formed from a common mineralizing fluid. The variation of lead-isotopic values of ores is similar to that of their host sedimentary strata. The lead in the various ore types and host rocks within the Bajiazi district is virtually identical. Lead-isotope signatures, which generally plot very close to model crustal growth curves, characterized by a model age of ∼1350 Ma, indicate a normal, nonradiogenic origin and an Early Proterozoic upper-crustal source for the lead in the ores. That lead was unrelated to the radiogenic lead in the Mesozoic granite. The δ13C values range from +1 to −5% PDB, and the δ18O values from −6 to −15% PDB. Later crystallization generations are enriched in the light isotopes of carbon and oxygen compared to early generations. The characteristics of carbon and oxygen isotopes of the Bajiazi deposits indicate that: (1) primary ores were precipitated in the Proterozoic marine environment; (2) both ores and host carbonates from the Bajiazi district are remarkably homogeneous in their carbon- and oxygen-isotope compositions during later tectonic, conlact-metamorphic stages; (3) although the variations in isotopic composition of carbon and oxygen are relatively small, a significant evolution toward a lighter isotopic composition with advancing diagenetic, tectonic, and contact metamorphic processes is observed; and (4) this evolution is independent of the presence or absence of ore minerals.