Isotopic Compositions Of Sulfide Minerals Research Articles

Provenance Tracing and Age Analysis of Lead–Zinc Mineralization in Qiyimuchang, Inner Mongolia, NE China

The Qiyimuchang lead–zinc deposit is an important deposit in the Erguna Massif on the west slope of Daxinganling, for which the material source and age of mineralization remain unclear. The lead–zinc deposit in Qiyimuchang has been observed to occur in Jurassic volcanic strata as a vein-like orebody, and its strike is nearly perpendicular to that of the strata and the regional structures of the orogenic belt. The ore is mainly composed of sphalerite, galena, chalcopyrite, pyrite, and quartz, and hydrothermal alteration zones dominated by silicification, fluoritization, and pyritization are common within 1–5 m on both sides of the vein. The metasomatic lead–zinc mineralization is characterized by a massive vein structure. The mineralization process can be divided into three stages, pre-ore (mainly quartz, arsenopyrite and a small amount of pyrite), ore-formation (pyrite, chalcopyrite, sphalerite, galena, fluorite, and a small amount of tetrahedrite), and post-ore (quartz-calcite veinlets with a small amount of pyrite). Element and isotope geochemical studies show that the trace element compositions of the wall rocks (andesite, tuff, etc.) of Jurassic volcanic rocks in the ore bodies and surrounding rocks reflect affinity or similarity between them. The S isotopic composition of sulfide minerals in the metallogenic stage (δ 34SV-CDT = 1.6‰~4.8‰) indicate the sulfur isotopic composition of the magma. The Pb isotopic compositions of sulfide minerals (38.5–38.39, 15.55–15.62, and 18.33–18.41 for 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb, respectively) in the metallogenic stage are relatively concentrated and close to the average Pb isotopic compositions of the mantle and average Pb isotopic composition of an orogenic belt, indicating that the ore-forming metals are likely to be a mixed source of crust and mantle. A new zircon U-Pb age of 150.8 ± 1.3 Ma (MSWD = 0.74) was obtained from andesitic tuff. Collectively considering the regional geology and ore deposit geological analysis, the lead–zinc mineralization in Qiyimuchang possibly occurred during the early Cretaceous. The ore-forming processes belong to Cretaceous magmatic-hydrothermal activity in extensional tectonic setting.

Chemical and Isotopic Composition of Sulfide Minerals from the Noho Hydrothermal Field in the Okinawa Trough

Studies of the element contents and isotopic characteristics of sulfide minerals from seafloor hydrothermal sulfide deposits are a significant method of investigating seawater-fluid mixing and fluid-rock and/or sediment interactions in hydrothermal systems. The seafloor hydrothermal sulfide ores from the Noho hydrothermal field (NHF) in the Okinawa Trough (OT) consist of pyrrhotite, isocubanite, sphalerite, galena, and amorphous silica. The Rh, Ag, Sb, and Tl contents mostly increase in galena as the fluid temperature decreases in the late ore-forming stage. In the sulfide minerals, the rare earth elements are mainly derived from the hydrothermal fluids, while the volcanic rocks and/or sediments are the sources of the sulfur and lead in the sulfide minerals. After the precipitation of galena, the redox state becomes oxidizing, and the pH value of the fluid increases, which is accompanied by the formation of amorphous silica. Finally, neither pyrite nor marcasite has been observed in association with pyrrhotite in the NHF sulfides, likely indicating that the amount of sulfur was limited in this hydrothermal system, and most of the residual Fe was incorporated into the sphalerite. This suggests that the later pyrite and/or marcasite precipitation in the seafloor hydrothermal sulfide deposit is controlled by the sulfur content of the fluid. Furthermore, it is possible to use hydrothermal sulfides and their inclusions to trace subseafloor fluid circulation processes.

Heterogeneous lead isotopic compositions of sulfide minerals from a hydrothermal replacement deposit (Janggun mine, South Korea)

The Janggun lead-zinc-(silver) deposit in South Korea was formed by hydrothermal-metasomatic processes. We collected 12 samples over a 100 m transect in one of the five orebodies recognized in the deposit and analyzed a total of 68 sulfide minerals.Detailed mineralogical observations show successive modifications and overprint of pristine sulfide by replacement reactions, suggesting several distinct petrogenetic events. We distinguished four different phase assemblages, which occur in contiguous zones of the transect. This suggests multiple alteration fronts. Major and minor element concentrations of sulfide phases were measured for the different sulfide generations.Milligram-sized sulfide mineral samples were micro-drilled for Pb and S isotope analyses with a resolution of 200 µm to 1 mm. Pb and S isotopic compositions (206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb and δ34S) are variable, showing 206Pb/204Pb ranges from 18.334 to 18.879, 207Pb/204Pb; 15.667 to 15.692, and 208Pb/204Pb; 38.682 to 38.899, and δ34S ranges from + 4.4 to + 6.2‰. Although Pb isotopic compositions and δ34S data are similar to literature data from different areas of the Janggun deposit, the Pb isotopic variations between the different samples (at the 10 m scale), and within individual polished sections (at the cm scale) are well over 100 times larger than the analytical uncertainty. The scatter in sulfur isotopic compositions confirms the Pb isotopic heterogeneity at both the cm and 10 m scales. At least seven isotopically well distinct fluid circulation episodes are required in the study area to explain different projections of common-denominator Pb isotope diagrams. This suggests that fluid pulses of distinct chemical and isotopic compositions circulated in distinct spatial and temporal episodes.To investigate the role of country rocks as sources of the metals transported by the ore-forming fluids, we leached 13 samples of country rocks (Janggun limestone, Chunyang granite, granophyre, and dyke) with dilute acid and analyzed both leachates and residues. Correlations are observed between Pb isotopic compositions and trace ratios (e.g. Co/Ni, Cu/Ag, and Zn/Cd). The Pb isotopic compositions of country rocks and Precambrian basement suggest that leaching of country rocks by circulating fluids is able to produce the observed Pb isotope and trace elements variations in the sulfide minerals, whereby different end-members in the isotope correlation diagrams can be linked to different country rocks.

Sulfur and lead isotopic variations in the giant Yulong porphyry Cu (Mo[sbnd]Au) deposit from the eastern Tibetan Plateau: Implications for origins of S and Pb, and metal precipitation

The giant Yulong porphyry Cu (MoAu) deposit, located in the eastern Tibetan Plateau, is a typical post-subduction porphyry Cu ± Mo ± Au deposit formed in an intracontinental strike-slip fault system, and it is also one of the largest porphyry Cu deposits in China with reserves of 6.5Mt Cu @ 0.62% and 0.41Mt Mo @ 0.042%, respectively. In this study, sulfur and lead isotopic compositions of sulfides and ore-related porphyry samples were determined to constrain the sources of ore-forming materials and ore-forming process. Sulfides (e.g., pyrite, chalcopyrite and molybdenite) from phyllic alteration zone, where the Cu and Mo mineralization mainly occurred, have uniform δ34S values ranging from −0.6 to +2.1‰ (average + 1.1‰), which indicates a magmatic origin of the sulfur. In situ Nano-SIMS sulfur isotope analysis further reveals that pyrites formed in potassic alteration stage have systematically negative δ34S values ranging from −0.2 to −9.7‰ (average − 4.5‰), whereas pyrites formed in phyllic alteration stage have systematically positive δ34S values ranging from +1.1 to +3.2‰ (average + 2.1‰). This regular variation is considered to be resulted from disproportionation of aqueous SO2 and subsequent sulfate reduction, further suggesting a magmatic origin of the sulfur. The sulfides have initial Pb isotopic compositions ((206Pb/204Pb)i = 18.616–18.812, (207Pb/204Pb)i = 15.670–15.740, (208Pb/204Pb)i = 38.956–39.080) deviating from those of the ore-related porphyries ((206Pb/204Pb)i = 18.549–18.718, (207Pb/204Pb)i = 15.647–15.662, (208Pb/204Pb)i = 38.794–39.888), but more close to those of the ore-hosting strata ((206Pb/204Pb)i = 18.423–18.761, (207Pb/204Pb)i = 15.654–15.713, (208Pb/204Pb)i = 38.867–39.062). The shift of Pb isotopic compositions of sulfide minerals toward those of ore-hosting strata indicates that the ore-hosting strata had provided a significant amount of Pb for ore formation, and most probably suggests fluid-rock interaction processes in the hydrothermal system. Our study represents a case study in which ore-hosting strata had provided a significant amount of ore-forming materials for porphyry Cu ± Mo ± Au formation in the post-subduction setting.

Environmental controls on sulfur isotopic compositions of sulfide minerals in seep carbonates from the South China Sea

Authigenic carbonates and pyrite associated with sulfate-driven anaerobic oxidation of methane (AOM) at methane seeps provide archives to explore the biogeochemical processes involved and seepage dynamics over time. The wide range and extremely high δ34S values of pyrite (δ34Spy) have been used to trace the AOM-related processes. However, the detailed mechanism for this phenomenon is not well understood. We propose that the characteristics of δ34Spy were mainly controlled by the competition between sulfate reduction and sulfate supply, as well as the redox condition. To test this hypothesis, we investigated Sr/Ca and Mg/Ca ratios, trace element compositions, pyrite contents and sulfur isotopic compositions in seep carbonates from Site F and Haima in the northern South China Sea. Calcite and aragonite contents were distinguished through the Sr/Ca and Mg/Ca ratios. The data show that aragonites are always associated with relatively low δ34Spy values compared to calcites. The Mo contents show a good correlation with pyrite contents in calcites and aragonites, and the slope in aragonites is larger than that in calcites. This relationship indicates that the aragonite precipitated in a relatively open system with higher Mo availability. Thus, we conclude that sulfides with low δ34S values formed at high supply of sulfate under the relatively open system with respect to diffusive replenishment of sulfate, where the carbonate precipitation occurred close to the seafloor due to a strong methane flux. Under vigorous methane flux simultaneously, the high potential of less anoxic conditions, which could limit the additional pyrite accumulation and/or favor the microbial disproportionation, could also be the cause of the low δ34Spy, as supported by samples from the Haima sites. Evidence for this assumption is based on the occurrence of bivalve shells and less enrichment in As and Sb. Conversely, the positive δ34Spy values result from near to complete exhaustion of dissolve sulfate via AOM within a deeper sulfate-methane transition zone, where Mo is less available. The combination of a detailed elemental study of authigenic carbonates with sulfur isotopic composition of sulfide minerals in carbonates is a promising tool for reconstructing the dynamics of seep intensities at modern and, potentially, geological seep sites.

Simultaneous measurement of sulfur and lead isotopes in sulfides using nanosecond laser ablation coupled with two multi-collector inductively coupled plasma mass spectrometers

We herein report the coupling of a nanosecond laser ablation system with a large-scale multi-collector inductively coupled plasma mass spectrometer (Nu1700 MC-ICPMS, NP-1700) and a conventional Nu Plasma II MC-ICPMS (NP-II) for the simultaneous laser ablation and determination of in situ S and Pb isotopic compositions of sulfide minerals. We found that the required aerosol distribution between the two spectrometers depended on the Pb content of the sample. For example, for a sulfide containing 100–3000 ppm Pb, the aerosol was distributed between the NP-1700 and the NP-II spectrometers in a 1:1 ratio, while for lead contents >3000 and <100 ppm, these ratios were 5:1 and 1:3, respectively. In addition, S isotopic analysis showed a pronounced matrix effect, so a matrix-matched external standard was used for standard-sample bracketing correction. The NIST NBS 977 (NBS, National Bureau of Standards; NIST, National Institute of Standards & Technology) Tl (thallium) dry aerosol internal standard and the NIST SRM 610 (SRM, standard reference material) external standard were employed to obtain accurate results for the analysis of Pb isotopes. In tandem experiments where airflow conditions were similar to those employed during stand-alone analyses, small changes in the aerosol carrier gas flow did not significantly influence the accurate determination of S and Pb isotope ratios. In addition, careful optimization of the flow ratio of the aerosol carrier (He) and makeup (Ar) gases to match stand-alone analytical conditions allowed comparable S and Pb isotope ratios to be obtained within an error of 2 s analytical uncertainties. Furthermore, the results of tandem analyses obtained using our method were consistent with those of previously reported stand-alone techniques for the S and Pb isotopes of chalcopyrite, pyrite, galena, and sphalerite, thus indicating that this method is suitable for the simultaneous analysis of S and Pb isotopes of natural sulfide minerals, and provides an effective tool to determine S and Pb isotope compositions of sulfides formed through multi-stage deposition routes.

Multiple sulfur isotope constraints on microbial sulfate reduction below an Archean seafloor hydrothermal system.

Microbial sulfate reduction is among the most ubiquitous metabolic processes on earth. The oldest evidence of microbial sulfate reduction appears in the ca. 3.5Ga Dresser Formation in the North Pole area of Pilbara Craton in Western Australia. That evidence was found through analysis of quadruple sulfur isotopes of sulfate and sulfide minerals deposited on the seafloor. However, the activity of microbial sulfate reduction below the Archean seafloor remains poorly understood. Here, we report the quadruple sulfur isotopic compositions of sulfide minerals within hydrothermally altered seafloor basalt and less altered basaltic komatiite collected from the North Pole Dome area. The Δ33 S values of the sulfide minerals were nonzero negative, suggesting that sulfate reduction occurred below the Archean seafloor. To constrain the substrate sulfate sources and sulfate reduction processes, we constructed a numerical model. Comparing the modeled and observed sulfur isotopes, we show that the substrate sulfate comprises seawater sulfate with a negative Δ33 S anomaly and 34 S-enriched sulfate with no anomalous Δ33 S. The latter component probably represents sulfate produced by local hydrothermal processes. The maximum sulfur isotopic fractionation between the putative substrate sulfate and the observed sulfide minerals within the altered basalt and basaltic komatiite is 35‰, which is consistent with a microbial origin. Alternatively, thermochemical sulfate reduction may also produce sulfide. However, considering the hydrothermal temperature inferred from the metamorphic grade of the altered basalt, the sulfur isotopic fractionation produced by inorganic sulfate reduction is probably below 20‰. Collectively, larger fractionations imply the involvement of biological sulfate reduction processes, both in the hydrothermal system below the seafloor and in less altered subsurface settings.

Pyrite-walled tube structures in a Mesoproterozoic sediment-hosted metal sulfide deposit

Unusual decimeter-scale structures occur in the sediment-hosted Black Butte Copper Mine Project deposit within lower Mesoproterozoic strata of the Belt Supergroup, Montana. These low domal and stratiform lenses are made up of millimeter-scale, hollow or mineral-filled tubes bounded by pyrite walls. X-ray micro−computed tomography (micro-CT) shows that the tube structures are similar to the porous fabric of modern diffuse hydrothermal vents, and they do not resemble textures associated with the mineralization of known microbial communities. We determined the sulfur isotopic composition of sulfide minerals with in situ secondary ion mass spectrometry (SIMS) and of texture-specific sulfate phases with multicollector−inductively coupled plasma−mass spectrometry (MC-ICP-MS). The sedimentological setting, ore paragenesis, sulfur isotope systematics, and porosity structure of these porous precipitates constrain the site of their formation to above the sediment-water interface where metalliferous hydrothermal fluids vented into the overlying water column. These data constrain the geochemistry of the Mesoproterozoic sediment-water interface and the site of deposition for copper-cobalt-silver mineralization. Metals in the hydrothermal fluids titrated sulfide in seawater to create tortuous fluid-flow conduits. Pyrite that precipitated at the vent sites exhibits large sulfur isotope fractionation (>50‰), which indicates a close association between the vents and sulfate-reducing microbiota. In the subsurface, base metal sulfides precipitated from sulfide formed during the reduction of early diagenetic barite, also ultimately derived from seawater. This model suggests dynamic bottom-water redox conditions at the vent site driven by the interplay between sulfate-reducing organisms and metalliferous fluid effluence.

Genesis of the Pb−Zn deposits of the Qingchengzi ore field, eastern Liaoning, China: Constraints from carbonate LA−ICPMS trace element analysis and C–O–S–Pb isotopes

The Qingchengzi ore field is an important Pb–Zn polymetallic ore district located in northeastern China, where more than ten Pb–Zn deposits and several Au-Ag deposits occur. The Pb–Zn mineralization is mainly hosted in the marble of the Dashiqiao Formation. Three distinct mineralization styles (strata-bound, open-space-filling and transitional type) are recognized. Two genetic models have been proposed to explain the Pb–Zn mineralization in this district: the sedimentary-exhalative model and the superimposed multi-stage model, in which syn-sedimentary deposition is overprinted by metamorphic and magmatic hydrothermal modification. Based on these three mineralization styles, this study provides new C–O–S–Pb isotopic data and LA–ICPMS trace element analyses of carbonates in order to place more constraints on the genesis of the Pb–Zn deposits.The δ13CPDB values of the syn-ore carbonates range from −5.11‰ to −1.06‰, and their δ18OSMOW values range from 3.30‰ to 13.2‰; these values are distinctively lower than those of barren meta-sedimentary rocks (δ13C=−1.98‰–−0.55‰, δ18O=19.69‰−22.76‰). The depleted C–O isotopic values of syn-ore carbonates are inferred to result from fluid-rock interactions combined with the impact of graphite. In situ LA–ICPMS trace element analyses show that syn-ore carbonates record enriched REE contents, pronounced positive Eu anomalies and lower Y/Ho ratios compared to barren carbonates. The depleted C–O isotopic signatures and distinctive REE characteristics of syn-ore carbonates indicate that the hydrothermal fluid is likely magmatic in origin and has mixed with low δ18O fluids, such as meteoric or formation water. Sulfide minerals have δ34S values ranging from 3.16‰ to 9.14‰ and display a gradually increasing trend from open-space-filling to transitional type to strata-bound mineralization styles, which reflect different mixing proportions of the two end-members of magmatic sulfur and sedimentary sulfur. The Pb isotopic compositions of sulfide minerals are relatively uniform (206Pb/204Pb=17.511–17.883, 207Pb/204Pb=15.549–15.64 and 208Pb/204Pb=37.670–38.178) for different mineralization styles; however, the open-space-filling mineralization records relatively lower lead isotope values. The linear correlation of ore lead isotopes between schist and Triassic intrusions indicates that lead may have originated from a mixture of magmatic and sedimentary end-members. The relatively lower Pb isotopes of the open-space-filling mineralization suggest the presence of higher proportions from a magmatic source. Mineralization styles respond to diverse ore-controlling structures and their proximity to the mineralizing source: open-space-filling mineralization shows the least stratigraphic control, with more pronounced “magmatic marks” (i.e., lower S–Pb isotopic values and more depleted C–O values), compared to strata-bound mineralization.These mineralization styles, combined with C–O–S–Pb isotopic geochemistry, consistently preclude a SEDEX origin for the Pb–Zn deposits in the Qingchengzi district, but suggest that they represent a distal hydrothermal mineralization type related to Triassic magmatic activity.

Sulfur and lead isotopic compositions of massive sulfides from deep-sea hydrothermal systems: Implications for ore genesis and fluid circulation

Studies of sulfur and lead isotopic compositions in hydrothermal deposits are an important tool to determine the source and processes of both sulfur and lead, and to understand the origin of hydrothermal ore deposits. Here, the sulfur and lead isotopic compositions of sulfide minerals have been studied for different hydrothermal fields in the East Pacific Rise (EPR), Mid-Atlantic Ridge (MAR), Central Indian Ridge (CIR), Southwest Indian Ridge (SWIR), and North Fiji Basin (NFB). The sulfur isotopic compositions of the studied sulfide samples are variable (δ34S 0.0 to 9.6‰, avg. δ34S 4.7‰; n=60), being close to the associated igneous rocks (~0‰ for, e.g., basalt, serpentinized peridotite), which may reflect the S in the sulfide samples is derived mainly from the associated igneous rocks, and a relatively small proportion (<36%) of seawater sulfur incorporated into these sulfides during mixing between seawater (δ34S 21‰) and hydrothermal fluid. In contrast for a mixed origin for the source of S, the majority of the lead isotopic compositions (206Pb/204Pb 17.541±0.004 to 19.268±0.001, 207Pb/204Pb 15.451±0.001 to 15.684±0.001, 208Pb/204Pb 37.557±0.008 to 38.988±0.002, n=21) of the sulfides possess a basaltic Pb isotopic composition, suggesting that the lead in the massive sulfide is mainly leached from local basaltic rocks that host the sub-seafloor hydrothermal systems in sediment-free mid-ocean ridges and mature back-arc basins. Furthermore, sulfide minerals in the super-fast and fast spreading mid-ocean ridges (MORs) exhibit less spread in their the δ34S values compared to sulfides from super-slow, and slow spreading MORs, which is most easily explained as a lesser degree of fluid-rock interaction and hydrothermal fluid-seawater mixing during hydrothermal ore-forming process. Additionally, the S and Pb isotope compositions of sulfides are controlled by the fluid processes for forming seafloor massive sulfide deposits. We demonstrate that the variable sulfur and lead isotopic compositions exhibit a relationship with the sulfur and lead sources, fluid–rock interaction, and fluid–seawater mixing.

Sulfur and Lead Isotopic Geochemistry of the Shidi Pb-Zn Deposit in Xiushan County, Chongqing

The Shidi Pb-Zn deposit is located in Xiushan County, southern Chongqing, and its orebodies were hosted in marine carbonates of the Cambrian Pingjing Formation. The authors selected sulfide minerals from the deposit for the analysis of sulfur and lead isotopic compositions. Theδ34S values of sulfide minerals vary from 10.8 to 15.6, with an average value of 13.52, indicating these sulfide materials were mainly derived from marine sulfate reduction. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios for sulfide minerals vary within the ranges of 18.319~18.422, 15.740~15.784 and 38.355~38.511, respectively. In the diagrams of Zartman, the Pb isotopic compositions of sulfide minerals fall into the regional upper crust lead zone. According to the characteristics of sulfur and lead isotopic compositions of the Shidi Pb-Zn deposit, the ore-forming materials might have come from the black shales of the Lower Cmabrian Niutitang Formation.

H‐O‐S‐Cu‐Pb Isotopic Constraints on the Origin of the Nage Cu‐Pb Deposit, Southeast Guizhou Province, SW China

Abstract:The Nage Cu‐Pb deposit, a new found ore deposit in the southeast Guizhou province, southwest China, is located on the southwestern margin of the Jiangnan Orogenic Belt. Ore bodies are hosted in slate and phyllite of Neoproterozoic Jialu and Wuye Formations, and are structurally controlled by EW‐trending fault. It contains Cu and Pb metals about 0.12 million tonnes with grades of 0.2 wt% to 3.4 wt% Cu and 1.1 wt% to 9.27 wt% Pb. Massive and disseminated Cu‐Pb ores from the Nage deposit occur as either veinlets or disseminations in silicified rocks. The ore minerals include chalcopyrite, galena and pyrite, and gangue minerals are quartz, sericite and chlorite. The H‐O isotopic compositions of quartz, S‐Cu‐Pb isotopic compositions of sulfide minerals, Pb isotopic compositions of whole rocks and ores have been analyzed to trace the sources of ore‐forming fluids and metals for the Nage Cu‐Pb deposit. The δCuNBS values of chalcopyrite range from −0.09% to +0.33‰, similar to basic igneous rocks and chalcopyrite from magmatic deposits. δ65CuNBS values of chalcopyrite from the early, middle and final mineralization stages show an increasing trend due to 63Cu prior migrated in gas phase when fluids exsolution from magma. δ34SCDT values of sulfide minerals range from −2.7‰ to +2.8‰, similar to mantle‐derived sulfur (0±3‰). The positive correlation between δCuNBS and δ34SCDT values of chalcopyrite indicates that a common source of copper metal and sulfur from magma. δDH2O‐SMOW and δ18OH2O‐SMOV values of water in fluid inclusions of quartz range from −60.7‰ to −44.4‰ and +7.9‰ to +9.0‰ (T=260°C), respectively and fall in the field for magmatic and metamorphic waters, implicating that mixed sources for H2O in hydrothermal fluids. Ores and sulfide minerals have a small range of Pb isotopic compositions (208Pb/204Pb=38.152 to 38.384, 207Pb/204Pb=15.656 to 17.708 and 206Pb/204Pb=17.991 to 18.049) that are close to orogenic belt and upper crust Pb evolution curve, and similar to Neoproterozoic host rocks (208Pb/204Pb=38.201 to 38.6373, 207Pb/204Pb=15.648 to 15.673 and 206Pb/204Pb=17.820 to 18.258), but higher than diabase (208Pb/204Pb=37.830 to 38.012, 207Pb/204Pb=15.620 to 15.635 and 206Pb/204Pb=17.808 to 17.902). These results imply that the Pb metal originated mainly from host rocks. The H‐O‐S‐Cu‐Pb isotopes tegather with geology, indicating that the ore genesis of the Nage Cu‐Pb deposit is post‐magmatic hydrothermal type.

Microscale sulfur isotopic compositions of sulfide minerals from the Jinding Zn–Pb deposit, Yunnan Province, Southwest China

The Jinding Zn–Pb deposit, located in the Lanping basin in Northwest Yunnan Province, is the largest Zn–Pb deposit in China, and also probably the youngest sediment-hosted super giant Zn–Pb deposit in the world. Its genesis differs from the well-known major types of sediment-hosted Zn–Pb deposits. Based on mineral paragenesis and textures, there are two stages of mineralization: stage 1 that is typically characterized by fine-grained sulfide minerals (galena, sphalerite, pyrite and marcasite) disseminated in sandstones of the Lower Cretaceous Jingxing Formation (K1j), and massive sulfides in limestone breccias of the Paleocene Yunlong Formation (E1y); and stage 2 which mainly occurs as coarse-grained galena veins crosscutting stage 1 sulfides, and minor amounts of colloform sphalerite intergrown with galena. In situ sulfur isotopic analyses of galena, sphalerite and pyrite were determined by secondary ion mass spectrometry (SIMS), and showed highly variable δ34S values (−42.1‰–7.7‰) of different ore types. Stage 1 mineralization has δ34S values from −42.1‰ to −10.2‰ with the majority ranging from −26‰ to −14‰. Stage 2 mineralization has higher δ34S values (−8.3‰–7.7‰). Combined with the geological settings and mineral paragenesis, the sulfur isotopic data presented here suggest multiple sulfur sources (biogenic sulfur+evaporites) and formation mechanisms for reduced sulfur (H2S). H2S responsible for stage 1 sulfide precipitation was associated with bacterial sulfate reduction (BSR). However, H2S of stage 2 was likely derived from thermochemical sulfate reduction (TSR). The most reasonable scenario for the stage 1 mineralization is a metal-bearing brine mixing with an H2S-rich fluid, thereby causing rapid sulfide precipitation. Till the stage 2, the ore-forming fluid shifted to the meteoric water that infiltrated and reacted with evaporitic rocks, leached metals and transported them as sulfate- or sulfite-complexes to the Jinding dome where the oxidized sulfur was reduced by organic matters to H2S, leading to precipitation of metal sulfides. In contrast to other sulfide deposits in the Lanping basin, biogenic sulfur might have played a key role in the mineralization process, especially during the early stage of formation of the Jinding Zn–Pb deposit.

Genesis of the Au–Bi–Cu–As, Cu–Mo ± W, and base–metal Au–Ag mineralization at the Mountain Freegold (Yukon, Canada): constraints from Ar–Ar and Re–Os geochronology and Pb and stable isotope compositions

The genesis of mineralized systems across the Mountain Freegold area, in the Dawson Range Cu–Au ± Mo Belt of the Tintina Au province was constrained using Pb and stable isotope compositions and Ar–Ar and Re–Os geochronology. Pb isotope compositions of sulfides span a wide compositional range (206Pb/204Pb, 18.669–19.861; 208Pb/204Pb, 38.400–39.238) that overlaps the compositions of the spatially associated igneous rocks, thus indicating a magmatic origin for Pb and probably the other metals. Sulfur isotopic compositions of sulfide minerals are broadly similar and their δ34S (Vienna-Canyon Diablo Troilite (V-CDT)) values range from −1.4 to 3.6 ‰ consistent with the magmatic range, with the exception of stibnite from a Au–Sb–quartz vein, which has δ34S values between −8.1 and −3.1 ‰. The δ34S values of sulfates coexisting with sulfide are between 11.2 and 14.2 ‰; whereas, those from the weathering zone range from 3.7 to 4.3 ‰, indicating supergene sulfates derived from oxidation of hypogene sulfides. The δ13C (Vienna Peedee Belemnite (VPDB)) values of carbonate range from −4.9 to 1.1 ‰ and are higher than magmatic values. The δ18O (V-SMOW) values of magmatic quartz phenocrysts and magmatic least-altered rocks vary between 6.2 and 10.1 ‰ and between 5.0 and 10.1 ‰, respectively, whereas altered magmatic rocks and hydrothermal minerals (quartz and magnetite) are relatively 18O-depleted (4.2 to 7.9 ‰ and −6.3 to 1.5 ‰, respectively). Hydrogen isotope compositions of both least-altered and altered igneous rock samples are D-depleted (from −133 to −161 ‰ Vienna-Standard Mean Ocean Water (V-SMOW)), consistent with differential magma degassing and/or post-crystallization exchange between the rocks and meteoric ground water. Zircon from a chlorite-altered dike has a U–Pb crystallization age of 108.7 ± 0.4 Ma; whereas, the same sample yielded a whole-rock Ar–Ar plateau age of 76.25 ± 0.53 Ma. Likewise, molybdenite Re–Os model ages range from 75.8 to 78.2 Ma, indicating the mineralizing events are genetically related to Late Cretaceous volcano-plutonic intrusions in the area. The molybdenite Re–Os ages difference between the nearby Nucleus (75.9 ± 0.3 to 76.2 ± 0.3 Ma) and Revenue (77.9 ± 0.3 to 78.2 ± 0.3 Ma) mineral occurrences suggests an episodic mineralized system with two pulses of hydrothermal fluids separated by at least 2 Ma. This, in combination with geological features suggest the Nucleus deposit represents the apical and younger portion of the Revenue–Nucleus magmatic-hydrothermal system and may suggest an evolution from the porphyry to the epithermal environments.

Ore‐forming Ages and Sulfur Isotope Study of Hydrothermal Deposits in Kamchatka, Russia

AbstractIn Kamchatka, Central Koryak, Central Kamchatka and East Kamchatka metallogenic belts are distributed from northwest to southeast. K–Ar age, sulfur isotopic composition of sulfide minerals, and bulk chemical compositions of ores were analyzed for 13 ore deposits including hydrothermal gold‐silver and base metal, in order to elucidate the geological time periods of ore formation, relationship to regional volcanic belts, type of mineralization, and origin of sulfur in sulfides. The dating yielded ore‐forming ages of 41 Ma for the Ametistovoe deposit in the Central Koryak, 17.1 Ma for the Zolotoe deposit and 6.9 Ma for the Aginskoe deposit in the Central Kamchatka, and 7.4 Ma for the Porozhistoe deposit and 5.1 Ma for the Vilyuchinskoe deposit in the East Kamchatka metallogenic belt. The data combined with previous data of ore‐forming ages indicate that the time periods of ore formation in these metallogenic belts become young towards the southeast. The averaged δ34SCDT of sulfides are −2.8‰ for the Ametistovoe deposit in Central Koryak, −1.8‰ to +2.0‰ (av. −0.1‰) for the Zolotoe, Aginskoe, Baranievskoe and Ozernovskoe deposits in Central Kamchatka, and −0.7 to +3.8‰ (av. +1.7‰) for Bolshe‐Bannoe, Kumroch, Vilyuchinskoe, Bystrinskoe, Asachinskoe, Rodnikovoe, and Mutnovskoe deposits in East Kamchatka. The negative δ34SCDT value from the Ametistovoe deposit in Central Koryak is ascribed to the contamination of 32S‐enriched sedimentary sulfur in the Ukelayat‐Lesnaya River trough of basement rock. Comparison of the sulfur isotope compositions of the mineral deposits shows similarity between the Central Koryak and Magadan metallogenic belts, and East Kamchatka and Kuril Islands belts. The Central Kamchatka belt is intermediate between these two groups in term of sulfur isotopic composition.

Re–Os and U–Pb Geochronology of the Erlihe Pb–Zn Deposit, Qinling Orogenic Belt, Central China, and Constraints on Its Deposit Genesis

Abstract:The Erlihe Pb–Zn deposit is an important mine of the Pb–Zn metallogenic zone in the South Qinling Orogen. It has been considered a sedimentary exhalative deposit in previous investigations because the ore body occurs concordantly at the transitional location of an upright fold. Re and Os isotopic analyses for paragenetic pyrites with sphalerite and galena from the ore body have been used to determine the timing of mineralization and to trace the source of metallogenic materials. The Re–Os isotopic data of four pyrite samples construct an isochron, yielding a weighted average age of 226±17 Ma (mean square weighted deviation=1.7), which is considered the main mineralization age. A dioritic porphyrite vein sample, showing weaker mineralization, was also dated using the SHRIMP zircon U–Pb isotopic method to constrain the youngest metallogenic age of the ore deposit, because it distributes along a group of tensional joints cutting not only the upright fold in the deposit field, but also the main ore bodies. The dioritic porphyrite sample yields a weighted mean 206Pb/238U age of 221±3 Ma, which is slightly younger than the Re–Os isotopic isochron age of the pyrites, considered as the upper age limit of the mineralization, namely the ending age of the mineralization. The Os isotopic compositions of sulfide minerals distribute within a range between Os isotopic compositions of the crust and the mantle, indicating that the ore deposit can be derived from magma‐related fluid, and the metallogenic materials are most likely derived from the mixing source of the crust and the mantle. The Erlihe Pb–Zn deposit and associated dioritic porphyrite vein, important records of Qinling tectonic–magmatism–mineralization activities, were formed during the Triassic collisional orogeny processes.

Isotope geochemical sequence of gold deposits in terrigenous successions

Based on the sulfur isotopic composition of sulfide minerals, gold deposits in terrigenous successions were systematized and grouped by variation ranges, intervals of modal values, and distribution of δ34S. It was concluded that the evolution of the sulfur isotopic composition of deposits depends on the character of changes in sulfur isotopes in the host rocks of the continental crust.

Sulfur, lead and helium isotopic compositions of sulfide minerals from the Dachang Sn-polymetallic ore district in South China: implication for ore genesis

The Dachang Sn-polymetallic ore district is one of the largest tin producing districts in China. Its origin has long been in dispute between magmatic-hydrothermal replacement and submarine exhalative-hydrothermal origin. The Dachang ore district comprises several types of ore deposits, including the Lamo magmatogenic skarn deposit near a granite intrusion, the Changpo-Tongkeng bedded and vein-type sulfide deposit, and the Gaofeng massive sulfide deposit. Sulfide minerals from the Lamo skarn ores show δ34S values in the range between −3 and +4‰ with a mean close to zero, suggesting a major magmatic sulfur source that likely was the intrusive Longxianggai granite. Sulfide minerals from the Gaofeng massive ores show higher δ34S values between +5 and +12‰, whereas sulfide minerals from the Changpo-Tongkeng bedded ores display lighter δ34S values between −7 and −0.2‰. The difference in the sulfur isotope ranges in the two deposits can be interpreted by different degrees of inorganic thermochemcial reduction of marine sulfate using a one-step batch separation fractionation model. Sulfur isotopic compositions from the vein-type ores at Changpo-Tongkeng vary widely from −8 to +4‰, but most of the data cluster around −2.9‰, which is close to that of bedded ores (−3.6‰). The sulfur in vein-type ores might be derived from bedded ores or it represents a mixture of magmatic- and sedimentary-derived sulfur. Pb isotopic compositions of sulfide minerals in the Dachang ore district reveal a difference between massive and bedded ores, with the massive ores displaying more radiogenic Pb isotope ratios. Correlations of 206Pb/204Pb and 207Pb/204Pb or 208Pb/204Pb for the massive and bedded ores are interpreted as two-component mixing of Pb leached from sedimentary host rocks and from deep-seated Precambrian basement rocks composed of metamorphosed volcano-sedimentary rocks. Pb isotopic compositions of sulfide minerals from vein-type ores overlap with those of bedded sulfides. Similar to the sulfur, the lead in vein-type ores might be derived from bedded ores. Skarn ores at Lamo show very limited variations in Pb isotopic compositions, which may reflect a major magmatic-hydrothermal lead source. Helium isotope data of fluid inclusions trapped in sulfides indicate that He in the massive and bedded ores has a different origin than He in fluorite of granite-related veins. The 3He/4He ratios of 1.2–2.9 Ra of fluid inclusions from sulfides at Gaofeng and Changpo-Tongkeng imply a contribution of mantle-derived fluids. Overall our data support a submarine exhalative-hydrothermal origin for the massive and bedded ore types at Dachang.

Sulfur Isotope Geochemistry of Sulfide Minerals

Research Article| January 01, 2006 Sulfur Isotope Geochemistry of Sulfide Minerals Robert R. Seal, II Robert R. Seal, II U.S. Geological Survey 954 National Center Reston, Virginia, 20192, U.S.A., e-mail: rseal@usgs.gov Search for other works by this author on: GSW Google Scholar Reviews in Mineralogy and Geochemistry (2006) 61 (1): 633–677. https://doi.org/10.2138/rmg.2006.61.12 Article history first online: 13 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Robert R. Seal; Sulfur Isotope Geochemistry of Sulfide Minerals. Reviews in Mineralogy and Geochemistry 2006;; 61 (1): 633–677. doi: https://doi.org/10.2138/rmg.2006.61.12 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 SocietyReviews in Mineralogy and Geochemistry Search Advanced Search Sulfur, the 10th most abundant element in the universe and the 14th most abundant element in the Earth’s crust, is the defining element of sulfide minerals and provides insights into the origins of these minerals through its stable isotopes. The insights come from variations in the isotopic composition of sulfide minerals and related compounds such as sulfate minerals or aqueous sulfur species, caused by preferential partitioning of isotopes among sulfur-bearing phases, known as fractionation. These variations arise from differences in temperature, or more importantly, oxidation and reduction reactions acting upon the sulfur. The oxidation and reduction reactions can... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Variations in the chemical and stable isotope composition of carbon and sulfur species during organic-rich sediment alteration: An experimental and theoretical study of hydrothermal activity at guaymas basin, gulf of california

Organic-rich diatomaceous ooze was reacted with seawater and a Na-Ca-K-Cl fluid of seawater chlorinity at 325–400°C, 400–500 bars, and fluid/sediment mass ratios of 1.56–2.35 to constrain factors regulating the abundance and stable isotope composition of C and S species during hydrothermal alteration of sediment from Guaymas Basin, Gulf of California. Alteration of inorganic and organic sedimentary components resulted in extensive exchange reactions, the release of abundant H 2S, CO 2, CH 4, and C organic, to solution, and recrystallization of the sediment to an assemblage containing albitic plagioclase, quartz, pyrrhotite, and calcite. The δ 34S cdt values of dissolved H 2S varied from −10.9 to +4.3‰ during seawater-sediment interaction at 325 and 400°C and from −16.5 to −9.0‰ during Na-Ca-K-Cl fluid-sediment interaction at 325 and 375°C. In the absence of seawater SO 4, H 2S is derived from both the transformation of pyrite to pyrrhotite and S released during the degradation of organic matter. In the presence of seawater SO 4, reduction of SO 4 contributes directly to H 2S production. Sedimentary organic matter acts as the reducing agent during pyrite and SO 4 reduction. Requisite acidity for the reduction of SO 4 is provided by Mg fixation during early-stage sediment alteration and by albite and calcite formation in Mg-free solutions. Organically derived CH 4 was characterized by δ 13C pdb values ranging between −20.8 and −23.1‰, whereas δ 13C pdb values for dissolved C organic ranged between −14.8 and −17.7%. Mass balance calculations indicate that δ 13 C values for organically derived CO 2 were ≥ − 14.8%. Residual solid sedimentary organic C showed small (≤ 0.7‰) depletions in 13C relative to the starting sediment. The experimental results are consistent with the isotopic and chemical composition of natural hydrothermal fluids and minerals at Guaymas Basin and permit us to better constrain sources and sinks for C and S species in subseafloor hydrothermal systems at sediment-covered spreading centers. Our data show that the sulfur isotope composition of hydrothermal Sulfide minerals in Guaymas Basin can be explained by derivation of S from diagenetic sulfide and seawater sulfate. Basaltic S may also contribute to hydrothermal sulfide precipitates but is not required to explain their isotopic composition. Estimates of seawater/ sediment mass ratios based on sulfur isotopic composition of sulfide minerals and the abundance of dissolved NH 3 in vent fluids range from 3–29 during hydrothermal circulation. Sources of C in Guaymas Basin hydrothermal fluids include thermal degradation of organic matter, bacteriogenic methane production, and dissolution of diagenetic carbonate.