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1.
More than 200 analyses of the sulfur isotopic composition of sulfides from various terrigenous and intrusive host rocks, metasomatically altered wall rocks, and gold lodes of the Upper Kolyma region are presented. In accessory pyrite of the metaterrigenous rocks, δ34S varies from ?23.1 to +5.7‰ δ34S of pyrite and arsenopyrite from gold-quartz mineralization is within the range ?10.6 to ?0.4‰ and is close to the average δ34S of pyrite from the metaterrigenous rocks (?4.4‰). In the intrusive rocks, δ34S of pyrite varies from ?3.8 to +2.6‰ (+0.7‰, on average) and drastically differs from δ34S of arsenopyrite from postmagmatic gold-rare-metal mineralization (?7.9 to ?2.7‰; ?5.2‰, on average). The comparison of the δ34S of accessory sulfides from the host rocks with δ34S of sulfides from the gold deposits suggests that sulfur mobilized from the terrigenous sequences participated in the hydrothermal process. The results obtained are consistent with the metamorphic model of the formation of gold-quartz deposits in the Upper Kolyma region.  相似文献   

2.
The Sawuershan region, one of the important gold metallogenic belts of Xinjiang, is located in the western part of the Kalatongke island arc zone of north Xinjiang, NW China. There are two gold deposits in mining, namely the Kuoerzhenkuola and the Buerkesidai deposits. Gold ores at the Kuoerzhenkuola deposit occur within Carboniferous andesite and volcanic breccias in the form of gold‐bearing quartz–pyrite veins and veinlet groups containing native gold, electrum, pyrite, pyrrhotite and chalcopyrite. Gold ores at the Buerkesidai deposit occur within Carboniferous tuffaceous siltstones in the form of gold‐bearing quartz veinlet groups and altered rocks, with electrum, pyrite and arsenopyrite as major metallic minerals. Both gold deposits are hosted by structurally controlled faults associated with intense hydrothermal alteration. The typical alteration assemblage is sericite + chlorite + calcite + quartz, with an inner pyrite–sericite zone and an outer chlorite–calcite–epidote zone between orebodies and wall rocks. δ34S values (0.3–1.3‰) of pyrite of ores from Kuoerzhenkuola deposit are similar to those (0.4–2.9‰) of pyrite of ores from Buerkesidai deposit. δ34S values (1.1–2.8‰) of pyrite from altered rocks are similar to δ34S values of magmatic or igneous sulfide sulfur, but higher than those from ores. 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb data of sulfide from ores range within 17.72–18.56, 15.34–15.61, and 37.21–38.28, respectively. These sulfur and lead isotope compositions imply that ore‐forming materials might originate from multiple, mainly deep sources. He and Ar isotope study on fluid inclusions of pyrites from ores of Kuoerzhenkuola and Buerkesidai gold deposits produces 40Ar/36Ar and 3He/4He ratios in the range of 282–525 and 0.6–9.4 R/Ra, respectively, indicating a mixed source of deep‐seated magmatic water (mantle fluid) and shallower meteoric water. In terms of tectonic setting, the gold deposits in the Sawuershan region can be interpreted as epithermal. These formations resulted from a combination of protracted volcanic activity, hydrothermal fluid mixing, and a structural setting favoring gold deposition. Fluid mixing was possibly the key factor resulting in Au deposition in the gold deposits in Sawuershan region.  相似文献   

3.
The Jiapigou gold belt (>150 t Au), one of the most important gold-producing districts in China, is located at the northeastern margin of the North China Craton. It is composed of 17 gold deposits with an average grade around 10 g/t Au. The deposits are hosted in Archean gneiss and TTG rocks, and are all in shear zones or fractures of varying orientations and magnitudes. The δ34S values of sulfide from ores are mainly between 2.7?‰ and 10?‰. The Pb isotope characteristics of ore sulfides are different from those of the Archean metamorphic rocks and Mesozoic granites and dikes, and indicate that they have different lead sources. The sulfur and lead isotope compositions imply that the ore-forming materials might originate from multiple, mainly deep sources. Fluid inclusions in pyrite have 3He/4He ratios of 0.6 to 2.5 Ra, whereas their 40Ar/36Ar ratios range from 1,444 to 9,805, indicating a dominantly mantle fluid with a negligible crustal component. δ18O values calculated from hydrothermal quartz are between ?0.2?‰ and +5.9?‰, and δD values of the fluids in the fluid inclusions in quartz are from ?70?‰ to ?96?‰. These ranges suggest dominantly magmatic water with a minor meteoric component. The noble gas isotopic data, along with the stable isotopic data, suggest that the ore-forming fluids have a dominantly mantle source with minor crustal addition.  相似文献   

4.
The S-isotope composition (δ34SCDT) of 213 samples of sulfides, sulfates and native sulfur from the pyrite mineralizations of southern Tuscany and associated country rocks were determined. The sulfur isotopic composition of pyrite is quite homogeneous and similar for all studied ore bodies, with an average δ34S value near +9,5‰. Pyrite disseminated within the Filladi di Boccheggiano formation, and thought to be authigenic, shows a much larger range of δ34S values (-13.1 to +14.5‰). The isotopic compositions of other sulfides associated with pyrite in the deposits show that isotopic equilibrium among sulfides was approached on a regional scale, but seldom fully attained. Isotopic data suggest that sedimentary marine sulfate was the ultimate source of sulfur in ores. Sulfates (mostly anhydrite) from the sulfate-carbonate lenses associated with both the Filladi di Boccheggiano and the Calcare Cavernoso formations also have similar and homogeneous compositions (average δ34S=+15–16‰). Coexisting sulfates and sulfides are not in isotopic equilibrium. In the light of the isotopic data, among the many proposed genetic models for the largest stratabound pyrite bodies the two following alternatives appear the most likely: 1) in agreement with recently suggested hypotheses, the ore bodies are older than the emplacement of the Mio-Pliocenic granitoids in the area, and are probably hydrothermal-sedimentary in origin, coeval with associated country rocks; 2) the ore bodies were formed as a consequence of bacterial reduction of anhydrite in low-temperature convection systems related to the early stages of the Mio-Pliocenic thermal anomaly. In both cases, the emplacement of the Mio-Pliocenic granitoids caused metamorphism and remobilization of the pre-existing ores, producing smaller discordant mineralized bodies.  相似文献   

5.
The Bianbianshan deposit, the unique gold-polymetal (Au-Ag-Cu-Pb-Zn) veined deposit of the polymetal metallogenic belt of the southern segment of Da Hinggan Mountains mineral province, is located at the southern part of the Hercynian fold belt of the south segment of Da Hinggan Mountains mineral province, NE China. Ores at the Bianbianshan deposit occur within Cretaceous andesite and rhyolite in the form of gold-bearing quartz veins and veinlet groups containing native gold, electrum, pyrite, chalcopyrite, galena and sphalerite. The deposit is hosted by structurally controlled faults associated with intense hydrothermal alteration. The typical alteration assemblage is sericite + chlorite + calcite + quartz, with an inner pyrite - sericite - quartz zone and an outer seicite - chlorite - calcite - epidote zone between orebodies and wall rocks. δ34 S values of 17 sulfides from ores changing from –1.67 to +0.49‰ with average of –0.49‰, are similar to δ34 S values of magmatic or igneous sulfide sulfur. 206Pb/204Pb, 207Pb/204Pb and 208Pb/ 204Pb data of sulfide from ores range within 17.66–17.75, 15.50–15.60, and 37.64–38.00, respectively. These sulfur and lead isotope compositions imply that ore-forming materials might mainly originate from deep sources. H and O isotope study of quartz from ore-bearing veins indicate a mixed source of deep-seated magmatic water and shallower meteoric water. The ore formations resulted from a combination of hydrothermal fluid mixing and a structural setting favoring gold-polymetal deposition. Fluid mixing was possibly the key factor resulting in Au-Ag-Cu-Pb-Zn deposition in the deposit. The metallogenesis of the Bianbianshan deposit may have a relationship with the Cretaceous volcanic-subvolcanic magmatic activity, and formed during the late stage of the crust thinning of North China.  相似文献   

6.
The Hoshbulak Zn–Pb deposit is located in South Tianshan, Xinjiang, China. The Zn–Pb orebody is tabular and stratoid in form and it is hosted in calcareous rocks of the Upper Devonian Tan'gaitaer Formation which were thrust over the Carboniferous system. The ores are mineralogically simple and composed mainly of sphalerite, galena, pyrite, calcite, dolomite and exhibit massive, banded, veinlets, colloidal, metasomatic, eutectic, concentric ring and microbial-like fabrics. The Co/Ni ratios of pyrite in the ores range from 0.46 to 0.90 by electron microprobe, which suggested that the Hoshbulak Zn–Pb mineralization was formed in a sedimentary environment. The REE patterns of the hydrothermal calcite coincide well with those of recrystallized micritic limestones, suggesting that the Hoshbulak Pb–Zn mineralization was closely genetically related to limestones of the Tan'gaitaer Formation. The C-, H- and O-isotopic compositions of hydrothermal calcite and dolomite in the ores yield δ13C(VPDB) values ranging from − 1.9‰ to + 2.6‰ (mean 0.79‰), δ18O(VSMOW) values from 22.41‰ to 24.67‰ (mean 23.04‰) and δD values from − 77‰ to − 102‰ for fluid inclusions. It is suggested that the ore-forming fluids, including CO2, were derived from the calcareous strata of the Tan'gaitaer Formation in association with hydrocarbon brines. The δ34S(VCDT) ranges from − 22.3‰ to − 8.5‰ for early ore-stage sulfides and from 5.9‰ to 24.2‰ with a cluster between 14.4‰ and 24.2‰ for the sulfides (pyrite, sphalerite, galena) in the main ore-stage. The ore sulfur may have been derived from evaporite rocks by thermochemical sulfate reduction (TSR) as the predominant mechanism for H2S generation. The Pb-isotopic compositions of the sulfide minerals from the Hoshbulak ores yield 206Pb/204Pb ratios from 17.847 to 18.173, 207Pb/204Pb ratios from 15.586 to 15.873 and 208Pb/204Pb ratios from 37.997 to 38.905, which indicate that the metals were sourced mainly from the Tan'gaitaer Formation. We conclude that the genesis of the Hoshbulak Mississippi Valley-type deposit was closely related to thrust faulting in the South Tianshan orogen of China.  相似文献   

7.
西秦岭阳山金矿带硫同位素特征:成矿环境与物质来源约束   总被引：13，自引：9，他引：4  
阳山金矿带成岩期的黄铁矿主要为立方体-他形,反映出一种较低温度(<200℃)、成岩流体的过饱和度低、快速冷却、氧逸度和硫逸度低、物质供应不足的成岩条件,δ34S值变化范围较大(-4.2‰～12.5‰),反映了硫源自于泥盆系地层,其中灰岩中黄铁矿硫源自于海水中硫酸根离子的还原作用,千枚岩中黄铁矿经历了细菌还原作用。成矿期黄铁矿具有多种晶形,但立方体单晶较少,指示成矿系统处于中-低温(200～300℃)、成矿流体的过饱和度高、缓慢冷却、氧逸度和硫逸度高、物质供应充分的成矿有利条件。成矿早阶段和主阶段硫化物的δ34S值变化范围为-4.2‰～3‰,接近于岩浆硫范围,其中成矿主阶段的黄铁矿以五角十二面体、八面体和立方体形成的聚形更常见,且聚形黄铁矿的硫同位素值变化范围更窄(-2.1‰～1.2‰),更符合岩浆硫来源特征;成矿晚阶段辉锑矿的δ34S值变化范围为-6.6‰～-4.5‰,而与其共生的黄铁矿δ34S值分别是7.6‰和-12.1‰,反映晚阶段除岩浆岩硫源外,浅变质的泥盆系地层也提供了部分硫源。  相似文献   

8.
The Prominent Hill deposit is a world-class iron oxide copper–gold (IOCG) deposit in South Australia, characterized by a high Cu/S ratio of the dominant Cu-(Fe) sulfides hosted by hematite breccias. It contains a total resource of 278 Mt of ore at 0.98% Cu and 0.75 g/t Au. Prominent Hill is one of several IOCG deposits and numerous prospects in the Olympic IOCG province that are temporally associated with the 1603–1575 Ma Gawler Range Volcanics, a large igneous province including co-magmatic granitoid intrusions of the Hiltaba Suite. Globally, IOCG deposits share many similar features in terms of their geological environment and mineral association. However, it is not yet clear whether sulfur and copper originate from the same source rocks and which hydrothermal redox processes created the characteristic iron oxide enrichment. Highly variable sulfur isotope compositions of sulfides and sulfates in IOCG deposits have previously been interpreted in terms of diverse sulfur sources that may include contributions from magmatic, sedimentary, seawater or evaporitic sulfur. In order to test these alternatives, we performed a detailed sulfur isotope study of Cu-(Fe) sulfides from Prominent Hill and IOCG prospects nearby. The Prominent Hill deposit shows a wide range in δ34SV-CDT between − 33.5‰ and 29.9‰ for Cu-(Fe) sulfides, and a narrower range of 4.3‰ to 15.8‰ for barite. Iron sulfides (pyrite, pyrrhotite) show a narrow range in sulfur isotope composition, whereas Cu-bearing sulfides show a much wider range, and more negative δ34SV-CDT values on average. We propose a two-stage sulfide mineralization model for the IOCG system in the Prominent Hill area, in which all hydrothermal sulfur is ultimately derived from a magmatic source that had a composition of 4.4 ± 2‰. The diversity in sulfur isotope composition can be produced by different fluid evolution pathways along reducing or oxidizing trajectories. A reduced sulfur evolution pathway is responsible for stage I mineralization, when intrusion-derived magmatic-hydrothermal fluids produced early pyrite and minor chalcopyrite at Prominent Hill, and iron ± copper sulfides in regional magnetite skarns and in some pervasively altered volcanic rocks of the Gawler Range Volcanics. Shallow-venting magmatic-hydrothermal fluids and subaerial volcanic gases that became completely oxidized by reaction with atmospheric oxygen produced sulfate and sulfuric acid with a sulfur isotope composition equal to their magmatic source. This highly oxidized ore fluid probably consisted dominantly of water from the hydrosphere, but contained magmatic solute components, notably sulfate, acidity and Cu. Sulfate reduction produced hydrothermal Cu sulfides with a wide range in sulfur isotope compositions from very negative to moderately positive values. Partial reaction of the Cu-rich stage II fluid with earlier stage I sulfides resulted in mixing of sulfur derived from sulfate reduction and from sulfides deposited during stage I. Modeling of the sulfur isotope fractionation processes in response to reducing and oxidizing pathways demonstrates that the entire spectrum of sulfur isotope data from stage I and stage II mineralization can be explained with a single, ultimately magmatic sulfur source. Such a magmatic sulfur source is also adequate to explain the complete spectrum of sulfur isotope data of other IOCG prospects and deposits in the Olympic province, including Olympic Dam. The results of our study challenge the conventional model that suggests the requirement of multiple and compositionally diverse sulfur sources in hematite-breccia hosted IOCG style mineralization.  相似文献   

9.
The Yinkeng orefield in Yudu County, Jiangxi Province, SE China, is a zone of concentrated Au-Ag-Pb-Zn-Cu-Mn polymetallic ores. Based on summing up basic geology and ore geology of the orefield, the polymetallic deposits in the orefield have been divided into seven major substyles according to their occurring positions and control factors. The ore-forming fluid inclusion styles in the orefield include those of two-phase fluid, liquid CO2-bearing three-phase and daughter mineral-bearing multi-phase. The homogenization temperatures range from 382o to 122oC, falling into five clusters of 370o to 390o, 300o to 360o, 230o to 300o, 210o to 290o and 120o to 200o, and the clusters of 300o to 360o, 230o to 300o and 120o to 200o are three major mineralization stages, with fluid salinity peaks from 4.14% to 7.31%, 2.07% to 7.31% and 0.53% to 3.90%, respectively. The ore-forming fluids are mainly type of NaCl-H2O with medium to high density(0.74–1.02 g/cm3), or CO2-bearing NaCl-H2O with medium to low density(0.18–0.79 g/cm3). The fluid salinity and density both show a decline tendency with decreasing temperature. According to the measurement and calculation of Hand O-isotopic compositions in the quartz of the quartz-sulfide veins, δDV-SMOW of the ore-forming fluid is from-84‰ to-54‰, and δ18OV-SMOW of that is from 6.75‰ to 9.21‰, indicating a magmatic fluid. The δ34SV-CDT of sulfides in the ores fall into two groups, one is from-4.4‰ to 2.2‰ with average of-1.42‰, and the other from 18.8‰ to 21.6‰ with average of 19.8‰. The S-isotopic data shows one peak at-4.4‰ to 2.2‰(meaning-1.42‰) suggesting a simple magmatic sulfur source. The ore Pbisotopic ratios are 206Pb/204Pb from 17.817 to 17.983, 207Pb/204Pb from 15.470 to 15.620 and 208Pb/204Pb from 38.072 to 38.481, indicating characteristics of mantle-derived lead. The data show that the major ore deposits in the orefield have a magmatic-hydrothermal genesis and that the SHRIMP zircon age of the granodiorite porphyry, closely related to the mineralization, is 151.2±4.2 Ma(MSWD = 1.3), which can represent the formation ages of the ores and intrusion rocks. The study aids understanding of the ore-forming processes of the major metallic ore deposits in the orefield.  相似文献   

10.
徐亮  谢巧勤  周跃飞  陈平  孙少华  陈天虎 《岩石学报》2019,35(12):3721-3733
铜官山矿田是铜陵矿集区内五大矿田之一,矿田内顺层产出的层状硫化物矿体是铜金矿床的主矿体,矿体内含有较多的胶状黄铁矿,其成因的争议制约了对铜金矿床成矿作用的解析。本文主要利用场发射扫描电镜(FE-SEM)等纳米矿物学手段,并结合光学显微镜、粉晶X射线衍射(XRD)、微区激光拉曼光谱分析等方法,对矿田内铜官山矿床及天马山矿床内层状硫化物矿体中胶状黄铁矿矿石的矿物组成、微形貌、微结构等特征进行系统研究,结果表明胶状黄铁矿矿石多呈胶状、鲕状结构,具有同心环状构造,同心环被赤铁矿、菱铁矿与黄铜矿脉穿切。同心环主要由白铁矿+有机质与胶状黄铁矿交替组成。胶状黄铁矿的黄铁矿颗粒粒径从纳米至亚微米均有分布,以自形-半自形立方体为主,少数呈他形,脉体边部胶状黄铁矿颗粒较大,自形程度较高,重结晶显著。矿石中含有少量白云石、伊利石微晶体,与胶状黄铁矿紧密共存,显示典型沉积特征。共存石英磨圆度较高,存在次生加大现象,表面存在胶状黄铁矿印模,显示为碎屑成因。这些综合信息表明胶状黄铁矿非岩浆热液成因,而是与石炭系地层同沉积成岩成因,并可能有微生物作用参与。高孔隙率、高化学活性及较高有机质含量的胶状黄铁矿可能为燕山期岩浆热液演化的含铜成矿流体提供了沉淀剂,对矿田内铜金硫化物矿体的层控性发挥了重要的控制作用。  相似文献   

11.
内蒙古甲生盘铅锌硫矿床硫同位素特征及其成因意义   总被引：4，自引：2，他引：2  
甲生盘铅锌硫矿床位于华北陆块北缘西段狼山—渣尔泰山成矿带,赋存于中元古代渣尔泰山群地层中,具有明显的层控特征并受同生断裂影响,区内矿石层纹状、角砾状和浸染状构造发育。矿石硫化物硫同位素测试分析表明:早期沉积硫化物3δ4S值变化范围在17.0‰~31.5‰之间,均值为23.9‰;后期穿插脉状硫化物3δ4S值变化范围在13.1‰~31.1‰之间,均值为24.1‰;二者3δ4S值相近,均属海水硫酸盐来源,后期热液改造作用微弱,火山活动对该矿区成矿作用直接贡献不明显;围岩3δ4S值变化范围在7.7‰~15.1‰之间,均值为10.2‰,明显小于矿石硫化物的3δ4S值,亦属海相沉积范畴;矿体北翼发育海西期花岗岩,但其对矿体的改造作用有限。  相似文献   

12.
The Heijianshan Fe–Cu (–Au) deposit, located in the Aqishan-Yamansu belt of the Eastern Tianshan (NW China), is hosted in the mafic–intermediate volcanic and mafic–felsic volcaniclastic rocks of the Upper Carboniferous Matoutan Formation. Based on the pervasive alteration, mineral assemblages and crosscutting relationships of veins, six magmatic–hydrothermal stages have been established, including epidote alteration (Stage I), magnetite mineralization (Stage II), pyrite alteration (Stage III), Cu (–Au) mineralization (Stage IV), late veins (Stage V) and supergene alteration (Stage VI). The Stage I epidote–calcite–tourmaline–sericite alteration assemblage indicates a pre-mineralization Ca–Mg alteration event. Stage II Fe and Stage IV Cu (–Au) mineralization stages at Heijianshan can be clearly distinguished from alteration, mineral assemblages, and nature and sources of ore-forming fluids.Homogenization temperatures of primary fluid inclusions in quartz and calcite from Stage I (189–370 °C), II (301–536 °C), III (119–262 °C) and V (46–198 °C) suggest that fluid incursion and mixing probably occurred during Stage I to II and Stage V, respectively. The Stage II magmatic–hydrothermal-derived Fe mineralization fluids were characterized by high temperature (>300 °C), medium–high salinity (21.2–56.0 wt% NaCl equiv.) and being Na–Ca–Mg–Fe-dominated. These fluids were overprinted by the external low temperature (<300 °C), medium–high salinity (19.0–34.7 wt% NaCl equiv.) and Ca–Mg-dominated basinal brines that were responsible for the subsequent pyrite alteration and Cu (–Au) mineralization, as supported by quartz CL images and H–O isotopes. Furthermore, in-situ sulfur isotopes also indicate that the sulfur sources vary in different stages, viz., Stage II (magmatic–hydrothermal), III (basinal brine-related) and IV (magmatic–hydrothermal). Stage II disseminated pyrite has δ34Sfluid values of 1.7–4.3‰, comparable with sulfur from magmatic reservoirs. δ34Sfluid values (24.3–29.3‰) of Stage III Type A pyrite (coexists with hematite) probably indicate external basinal brine involvement, consistent with the analytical results of fluid inclusions. With the basinal brines further interacting with volcanic/volcaniclastic rocks of the Carboniferous Matoutan Formation, Stage III Type B pyrite–chalcopyrite–pyrrhotite assemblage (with low δ34Sfluid values of 4.6–10.0‰) may have formed at low fO2 and temperature (119–262 °C). The continuous basinal brine–volcanic/volcaniclastic rock interactions during the basin inversion (∼325–300 Ma) may have leached sulfur and copper from the rocks, yielding magmatic-like δ34Sfluid values (1.5–4.1‰). Such fluids may have altered pyrite and precipitated chalcopyrite with minor Au in Stage IV. Eventually, the Stage V low temperature (∼160 °C) and low salinity meteoric water may have percolated into the ore-forming fluid system and formed late-hydrothermal veins.The similar alteration and mineralization paragenetic sequences, ore-forming fluid sources and evolution, and tectonic settings of the Heijianshan deposit to the Mesozoic Central Andean IOCG deposits indicate that the former is probably the first identified Paleozoic IOCG-like deposit in the Central Asian Orogenic Belt.  相似文献   

13.
The Jinwozi lode gold deposit in the eastern Tianshan Mountains of China includes auriferous quartz veins and network quartz veins that are exemplified by the Veins 3 and 210, respectively. This paper presents H‐, O‐isotope compositions and gas compositions of fluid inclusions hosted in sulfides and quartz, and S‐, Pb‐isotope compositions of sulfide separates collected from the principal Stage 2 ores in Veins 3 and 210. Fluid inclusions trapped in quartz and sphalerite are pseudo‐secondary and primary. They were trapped from the fluids during the successive or alternate precipitation of quartz with sulfides. H‐ and O‐isotope compositions of fluid inclusion of three pyrite and one quartz separates from Vein 210 plot within the field of degassed melt, which is evidence for the incorporation of magmatic fluid as well with some possibility of contribution of metamorphic water to the hydrothermal system since the two datasets show a higher oxygen isotopic ratio than those of degassed melt. However, δD and δ18O values of fluid inclusions hosted in sulfides and quartz from Vein 3 are distinctly lower than those from Vein 210. In addition, salinities of fluid inclusion from Vein 3, approximately 3 to 6 wt% NaCl equivalent, are considerably lower than those from Vein 210, which are approximately 8 to 14 wt% NaCl equivalent. Ore‐forming fluids of Veins 3 and 210 have migrated through the relatively high and low levels in the imbricate‐thrust column where rock deformation is characterized by dilatancy or ductile–brittle transition, respectively. Therefore, the ore‐forming fluid of Vein 3 is interpreted to have mixed with greater amounts of meteoric‐derived groundwater than that of Vein 210. Fluid inclusions hosted in sulfides contain considerably higher abundances of gaseous species of CO2, N2, H2S, and so on, than those hosted in quartz. Many of these gaseous species exhibit linear correlations with H2O. These linear trends are interpreted in terms of mixing between magmatic fluid and groundwater. The relative enrichment of gaseous species in fluid inclusions hosted in sulfides, coupled with the banded ore structure, suggests that the magmatic fluid was involved with the ore‐forming fluid in pulsation. Lead isotope compositions of 21 pyrite and galena separates form a linear trend, suggesting mixing of metallic materials from diverse reservoirs. The δ34S values of pyrite and galena range from +5.6‰ to +7.9‰ and from +3.1‰ to +6.3‰, respectively, indicating sulfur of the Jinwozi deposit has been leached mainly from the granodiorite and partly from the Jinwozi Formation by the circulating ore‐forming fluid.  相似文献   

14.
云南思茅盆地位于特提斯成矿带东南段,上白垩统勐野井组是该区域一套广泛分布的含盐地层,该组内赋存有中国目前唯一的前第四纪固体钾盐矿床。对思茅盆地江城地区勐野井组石膏和黄铁矿样品,利用电子探针和质谱仪进行了主、微量元素和硫同位素分析,结果表明黄铁矿的n(S)/n(Fe)平均值为202,为硫富集型黄铁矿;黄铁矿的w(Co)/w(Ni)值为301~1074,变化范围较大;黄铁矿的δ34SV-CDT值为-836‰~-336‰,平均值为-633‰,而石膏的δ34SV-CDT值为66‰~107‰,平均值为948‰。通过对黄铁矿n(S)/n(Fe)、w(Co)/w(Ni)、硫同位素以及石膏硫同位素进行分析,认为勐野井组石膏层在成岩期后受到了热液蚀变的作用,热液蚀变导致石膏被还原形成S2-,S2-与热液带来的Fe结合形成了粒状黄铁矿。通过对思茅盆地江城地区勐野井组黄铁矿、石膏的成因机制研究得出,受印度板块俯冲活动控制,深部热液对该区上白垩统勐野井组内原生蒸发岩有明显改造作用并有多种金属矿物伴生。思茅盆地晚白垩世以来热液活动频繁,多期次的热液作用对盆地金属成矿有积极影响,对勐野井组钾盐有不利的改造作用,使得原生钾盐发生蚀变,普遍发生重结晶作用。  相似文献   

15.
Chilean manto-type (CMT) Cu(–Ag) hydrothermal deposits share a characteristic association of volcano-sedimentary Jurassic to Lower Cretaceous host rocks, style of mineralization, ore and associated mineralogy and geochemistry, with ore grades typically > 1%Cu, that make this family of deposits significant and interesting, both academically and economically. Although often stratabound, geological evidence supports an epigenetic origin for these deposits. We present a detailed stable isotope study of La Serena and Melipilla–Naltahua Lower Cretaceous deposits, central Chile, which reveals extremely negative δ34S values, to − 50‰, which are among the lowest values found in any ore deposit. In addition, the range of δ34S values from sulfides in the two areas is very wide: − 38.3 to − 6.9‰ in La Serena, and − 50.4 to − 0.6‰ in Melipilla–Naltahua. These new data significantly extended the reported range of δ34S data for CMT deposits. Co-existing sulfates range from 7.9 to 14.3‰, and are exclusive to La Serena deposit. The wide sulfide isotopic range occurs at deposit and hand specimen scale, and suggests a polygenic sulfur source for these deposits, where bacteriogenic sulfide dominates. While sulfur isotope data for the bulk of Jurassic CMT deposits, northern Chile, suggests a predominant magmatic source in their origin (mean = − 2.7 ± 1.9‰, 1σ), contributions of a magmatic component is only likely to be involved at Melipilla–Naltahua deposit.The δ13C values obtained for calcites associated with the mineralization range from − 20.1 to 0.2‰ also suggesting polygenic carbon sources, with the likely strong involvement of degradation of organic matter and leaching of limestone.Two different genetic models, with involvement of hydrocarbon, are proposed for both areas. For Melipilla–Naltahua, a two-step model can be developed as follows: 1) Framboidal pyrite growth, with very low δ34S, formed by bacterial sulfate reduction in an open system, and with diagenetic degradation of oil-related brines, leaving pyrobitumen. 2) Cu-bearing stage, replacing of framboidal pyrite, inheriting depleted sulfur as low as − 50.4‰, together with sulfides directly precipitated from a hydrothermal fluid with δ34S close to 0‰. For La Serena, a single step model fits best, without framboidal pyrite generation. Cu-bearing sulfides were precipitated mainly in veins where Cu plus base metal-bearing hydrothermal fluids mixed with H2S generated by bacterial sulfate reduction in the host rocks. Isotopic evidence clearly illustrates that bacterial activity, perhaps enhanced by hydrothermal activity, was fed by hydrocarbon brines and sulfate remobilized from continental evaporites. It is possible that variable ecological conditions led to different extents of isotopic fractionation, adding to the typical sulfur isotopic heterogeneity of such bacterial systems. For both areas, the Cu-bearing stage occurred during the peak to waning stages of the very low-grade metamorphism that affected the Lower Cretaceous sequence.  相似文献   

16.
The Palinuro volcanic complex and the Panarea hydrothermal field, both located in the Tyrrhenian Sea (Italy), are associated with island arc magmatism and characterized by polymetallic sulfide mineralization. Dissolved sulfide concentrations, pH, and Eh measured in porewaters at both sites reveal a variable hydrothermal influence on porewater chemistry.Multiple sulfur isotopic measurements for disseminated sulfides (CRS: chromium reducible sulfur) extracted from sediments at Palinuro yielded a broad range in δ34S range between ?29.8 and + 10.2‰ and Δ33S values between + 0.015 and + 0.134‰. In contrast, sediments at Panarea exhibit a much smaller range in δ34SCRS with less negative values between ?11.3 and ?1.8‰. The sulfur isotope signatures are interpreted to reflect a mixture between hydrothermal and biogenic sulfide, with a more substantial biogenic contribution at Panarea.Multiple sulfur isotope measurements were performed on sulfides and elemental sulfur from drill core material from the Palinuro massive sulfide complex. δ34S and Δ33S values for pyrite between ?32.8 and ?1.1‰ and between ?0.012 to + 0.042‰, respectively, as well as for elemental sulfur with δ34S and Δ33S values between ?26.7 and ?2.1‰ and between + 0.035 and + 0.109‰, respectively, point to a microbial origin for much of the sulfide and elemental sulfur studied. Moreover, data suggest a coupling of bacterial sulfate reduction, sulfide oxidation and sulfur disproportionation. In addition, δ34S values for barite between + 25.0 and + 63.6‰ are also in agreement with high microbial turnover of sulfate at Palinuro.Although a magmatic SO2 contribution towards the formation of the Palinuro massive sulfide complex is very likely, the activity of different sulfur utilizing microorganisms played a fundamental role during its formation. Thus, porewater and multiple sulfur isotope data reveal differences in the hydrothermal activity at Palinuro and Panarea drill sites and underline the importance of microbial communities for the origin of massive sulfide mineralizations in the hydrothermal subsurface.  相似文献   

17.
王萍  周琦  杜远生  余文超  徐源  齐靓  袁良军 《地球科学》2016,41(12):2031-2040
黔东松桃地区是我国重要的锰矿富集区,其中大塘坡组中黄铁矿δ34S存在比较大的差异.通过CF-IRSM法对松桃李家湾、道坨、西溪堡矿区菱锰矿样品中黄铁矿硫同位素组成开展研究,结果显示出两个明显的特征:(1) 样品中黄铁矿普遍具有极高的δ34S值,为47.69‰~66.76‰;(2) 在同一成锰盆地中,水深相对较浅的李家湾矿区黄铁矿δ34S值(47.69‰~59.15‰)明显低于水深相对较深的道坨矿区的δ34S值(53.85‰~62.86‰),且中心相δ34S的值(53.85‰~66.76‰)明显高于过渡相δ34S的值(47.69‰~59.15‰),黄铁矿硫同位素组成表现出明显的深度梯度效应.大塘坡组含锰层位黄铁矿异常高的δ34S值及其明显的深度梯度特征表明,在新元古代Sturtian冰期刚刚结束的间冰期初期,海水硫酸盐浓度极低,海洋呈现显著的分层现象,这一时期深部海洋可能并没有完全氧化.   相似文献   

18.
Research on sulfur isotopes in hydrothermal uranium deposits with acid alterations shed much light on the genetic aspects of hydrothermal uranium deposits. Based on the studies of uranium deposits of different genesis, it is concluded that σ34S of Sulfides in hydrothermal uranium deposits derived from residual magma is within the range of +2‰ ?2.6‰, approximately the same as meteorite sulfur. δ34S of Sulfides in polygenetic hydrothermal uranium deposits is slightly lighter than meteorite sulfur and varies over a restricted range (6.7‰), averaging ?10.15‰. Two intervals can be recognized with respect to sulfur isotopic compositions in palingenetic hydrothermal uranium deposits. δ34S of sulfides formed in diagenesis, autometamorphism and hypothermal stages is similar to meteorite sulfur. On the other hand, at the stage starting from the alteration of uranium mineralization to the formation o uranium deposits and postmineralization the average δ34S is -7.89‰, with a wider range of δ34S variation (13.7‰), which can be attributed to the enrichment of δ34S in palingenetic hydrothermal solutions.  相似文献   

19.
查汗萨拉金矿是近年在新疆西天山新发现的一处金矿床,处于依连哈比尔尕构造带西端.矿体旱不规则脉状产于细品闪长岩构造破碎蚀变带及其接触带附近的上石炭统奇尔古斯套组蚀变围岩中,围岩蚀变较弱.矿石中硫化物主要为黄铁矿,并含少量磁黄铁矿、黄铜矿、方铅矿等.硫化物矿物呈自形粗晶或半自形结构,斑杂状分布在构造蚀变岩石中.金矿物以自然金和银金矿为主,还发现有硫(碲)银金矿和金铀化物等独特矿化线索,金矿物多赋存在黄铁矿中,以包体金、裂隙金和少量粒间金形式存在.金矿物形态以粒状和长角状为主,多为细、微细粒金(粒度<10 μm).矿石中矿物流体包裹体均一温度为220～340℃.热液脉三石矿物石英流体包裹体的δD为-92‰～-74‰,δ18Ov-SMOW为11.8‰～12.6‰,成矿流体显尔岩浆热液和变质建造水混合的特征.热液方解石脉的占δ13Cv-PDB为-8.92‰～-8.06‰,δ18Ov-SMOW为13.45‰～17.18‰,反映成矿流体中CO2主体米源于岩浆.硫化物206pb/204Pb为18.036～18.173,207pb/204pb为15.536～15.612,208pb/204pb为37.940～38.097,成矿金属具岩浆来源特征.矿石中硫化物δ34Sv-CDT为-9.8‰～-7.3‰,显示其可能与地层有关.查汗萨拉金矿为构造蚀变岩型中温岩浆热液矿床.小同于本区阿希金矿,是西天山金矿勘查中值得关注的新类型.  相似文献   

20.
老金厂金矿床是北山成矿南带最具代表性的中低温岩浆热液型金矿床之一，其规模为中型。依据脉体穿插、矿物共生组合和矿石结构构造等特征，将矿床矿化作用过程划分为石英-黄铁矿阶段（Ⅰ）、石英-含砷黄铁矿-毒砂阶段（Ⅱ）、石英-黄铁矿-多金属硫化物阶段（Ⅲ）和石英-方解石阶段（Ⅳ）。利用电子探针研究了不同成矿阶段载金矿物的元素组成及其分布规律。Ⅰ阶段：黄铁矿以粗粒自形立方体为主，粒度为0.50~1.50 mm，贫As、Au；毒砂含量极少，呈细粒他形。Ⅱ阶段：含砷黄铁矿周围常有大量毒砂产出，含砷黄铁矿多为立方体、五角十二面体，粒度为0.30~1.00 mm，富As、Au；该阶段矿化最为强烈，毒砂主要形成于此时期，多呈棱柱状、柱状、放射状集合体，显示富S亏As特征。Ⅲ阶段：多以黄铁矿-黄铜矿-闪锌矿共生组合脉的形式产出，黄铁矿多呈长条状，以富S、Cu、Zn、Au和贫Fe、As为特征。Ⅳ阶段：矿化作用极弱，毒砂、黄铁矿含量极少，为细粒他形。原位硫同位素组成显示：Ⅰ阶段黄铁矿δ34SV-CDT值为-3.8‰~-2.9‰，均值为-3.3‰；Ⅱ阶段黄铁矿和毒砂δ34SV-CDT值为-4.7‰~2.6‰，均值为-3.3‰；Ⅲ阶段黄铁矿和闪锌矿δ34SV-CDT值主要分布于-1.9‰~1.0‰之间，均值为0.1‰。此3个阶段硫同位素组成反映了成矿期硫主要来源于幔源岩浆，混入了部分地层硫。综合前人研究成果，认为成矿早期至晚期，成矿流体总体上由富S贫As向富As贫S演化。Ⅰ阶段体系处于中性稳定的环境，硫源充足；Ⅱ阶段为贫S富As的高氧逸度环境，由于大气降水对地层的淋滤渗透，混入富As流体，Au可能与As结合形成Au-As络合物，在成矿有利部位富集沉淀；Ⅲ阶段成矿元素种类丰富，体系为富S贫As的弱还原环境，Au很可能与HS-、S-形成络合物进入黄铁矿晶格。  相似文献   

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