Geological and C–O–S–Pb–Sr isotopic constraints on the origin of the Qingshan carbonate-hosted Pb–Zn deposit,Southwest China

Located in the western Yangtze Block, the Qingshan Pb–Zn deposit, part of the Sichuan–Yunnan–Guizhou Pb–Zn metallogenic province, contains 0.3 million tonnes of 9.86 wt.% Pb and 22.27 wt.% Zn. Ore bodies are hosted in Carboniferous and Permian carbonate rocks, structurally controlled by the Weining–Shuicheng anticline and its intraformational faults. Ores composed of sphalerite, galena, pyrite, dolomite, and calcite occur as massive, brecciated, veinlets, and disseminations in dolomitic limestones.

The C–O isotope compositions of hydrothermal calcite and S–Pb–Sr isotope compositions of Qingshan sulphide minerals were analysed in order to trace the sources of reduced sulphur and metals for the Pb–Zn deposit. δ¹³C_PDB and δ¹⁸O_SMOW values of calcite range from –5.0‰ to –3.4‰ and +18.9‰ to +19.6‰, respectively, and fall in the field between mantle and marine carbonate rocks. They display a negative correlation, suggesting that CO₂ in the hydrothermal fluid had a mixed origin of mantle, marine carbonate rocks, and sedimentary organic matter. δ³⁴S values of sulphide minerals range from +10.7‰ to +19.6‰, similar to Devonian-to-Permian seawater sulphate (+20‰ to +35‰) and evaporite rocks (+23‰ to +28‰) in Carboniferous-to-Permian strata, suggesting that the reduced sulphur in hydrothermal fluids was derived from host-strata evaporites. Ores and sulphide minerals have homogeneous and low radiogenic Pb isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 18.561 to 18.768, ²⁰⁷Pb/²⁰⁴Pb = 15.701 to 15.920, and ²⁰⁸Pb/²⁰⁴Pb = 38.831 to 39.641) that plot in the upper crust Pb evolution curve, and are similar to those of Devonian-to-Permian carbonate rocks. Pb isotope compositions suggest derivation of Pb metal from the host rocks. ⁸⁷Sr/⁸⁶Sr ratios of sphalerite range from 0.7107 to 0.7136 and (⁸⁷Sr/⁸⁶Sr)_200Ma ratios range from 0.7099 to 0.7126, higher than Sinian-to-Permian sedimentary rocks and Permian Emeishan flood basalts, but lower than Proterozoic basement rocks. This indicates that the ore strontium has a mixture source of the older basement rocks and the younger cover sequence. C–O–S–Pb–Sr isotope compositions of the Qingshan Pb–Zn deposit indicate a mixed origin of the ore-forming fluids and metals.     

Geology,isotope geochemistry and ore genesis of the Shanshulin carbonate-hosted Pb–Zn deposit,southwest China

The Shanshulin Pb–Zn deposit occurs in Upper Carboniferous Huanglong Formation dolomitic limestone and dolostone, and is located in the western Yangtze Block, about 270 km west of Guiyang city in southwest China. Ore bodies occur along high angle thrust faults affiliated to the Weishui regional fault zone and within the northwestern part of the Guanyinshan anticline. Sulfide ores are composed of sphalerite, pyrite, and galena that are accompanied by calcite and subordinate dolomite. Twenty-two ore bodies have been found in the Shanshulin deposit area, with a combined 2.7 million tonnes of sulfide ores grading 0.54 to 8.94 wt.% Pb and 1.09 to 26.64 wt.% Zn. Calcite samples have δ¹³C_PDB and δ¹⁸O_SMOW values ranging from − 3.1 to + 2.5‰ and + 18.8 to + 26.5‰, respectively. These values are higher than mantle and sedimentary organic matter, but are similar to marine carbonate rocks in a δ¹³C_PDB vs. δ¹⁸O_SMOW diagram, suggesting that carbon in the hydrothermal fluid was most likely derived from the carbonate country rocks. The δ³⁴S_CDT values of sphalerite and galena samples range from + 18.9 to + 20.3‰ and + 15.6 to + 17.1‰, respectively. These values suggest that evaporites are the most probable source of sulfur. The δ³⁴S_CDT values of symbiotic sphalerite–galena mineral pairs indicate that deposition of sulfides took place under chemical equilibrium conditions. Calculated temperatures of S isotope thermodynamic equilibrium fractionation based on sphalerite–galena mineral pairs range from 135 to 292 °C, consistent with previous fluid inclusion studies. Temperatures above 100 °C preclude derivation of sulfur through bacterial sulfate reduction (BSR) and suggest that reduced sulfur in the hydrothermal fluid was most likely supplied through thermo-chemical sulfate reduction (TSR). Twelve sphalerite samples have δ⁶⁶Zn values ranging from 0.00 to + 0.55‰ (mean + 0.25‰) relative to the JMC 3-0749L zinc isotope standard. Stages I to III sphalerite samples have δ⁶⁶Zn values ranging from 0.00 to + 0.07‰, + 0.12 to + 0.23‰, and + 0.29 to + 0.55‰, respectively, showing the relatively heavier Zn isotopic compositions in later versus earlier sphalerite. The variations of Zn isotope values are likely due to kinetic Raleigh fractional crystallization. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of the sulfide samples fall in the range of 18.362 to 18.573, 15.505 to 15.769 and 38.302 to 39.223, respectively. The Pb isotopic ratios of the studied deposit plot in the field that covers the upper crust, orogenic belt and mantle Pb evolution curves and overlaps with the age-corrected Proterozoic folded basement rocks, Devonian to Lower Permian sedimentary rocks and Middle Permian Emeishan flood basalts in a ²⁰⁷Pb/²⁰⁴Pb vs. ²⁰⁶Pb/²⁰⁴Pb diagram. This observation points to the derivation of Pb metal from mixed sources. Sphalerite samples have ⁸⁷Sr/⁸⁶Sr_200 Ma ratios ranging from 0.7107 to 0.7115 similar to the age-corrected Devonian to Lower Permian sedimentary rocks (0.7073 to 0.7111), higher than the age-corrected Middle Permian basalts (0.7039 to 0.7078), and lower than the age-corrected Proterozoic folded basement (0.7243 to 0.7288). Therefore, the Sr isotope data support a mixed source. Studies on the geology and isotope geochemistry suggest that the Shanshulin deposit is a carbonate-hosted, thrust fault-controlled, strata-bound, epigenetic, high grade deposit formed by fluids and metals of mixed origin.     

The Paleozoic Ozbak-Kuh carbonate-hosted Pb-Zn deposit of East Central Iran: Isotope (C,O, S,Pb) geochemistry and ore genesis

Lead and zinc mineralization occurs in dolostones of the Middle Devonian Sibzar Formation at Ozbak-Kuh, which is located 150 km north of Tabas city in East Central Iran. The ore is composed of galena, sphalerite and calcite, with subordinate dolomite and bitumen. Wall-rock alterations include carbonate recrystallization and dolomitization. Microscopic studies reveal that the host rock is replaced by galena and sphalerite. The Pb–Zn mineralization is epigenetic and stratabound. The δ¹³C values of hydrothermal calcite samples fall in the narrow range between ?0.3‰ and 0.8‰. The δ¹⁸O values in calcite display a wider range, between ?14.5‰ and ?11.9‰. The δ¹³C and δ¹⁸O values overlap with the oxygen and carbon isotopic compositions of Paleozoic seawater, indicating the possible important participation of Paleozoic seawater in the ore-forming fluid. The δ¹⁸O signature corresponds to a spread in temperature of about 70 °C in the ore-bearing fluid. The δ¹³C values indicate that the organic materials within the host rocks did not contribute significantly in the hydrothermal fluid. The δ³⁴S values of galena and sphalerite samples occupy the ranges of 12.2‰–16.0‰ and 12.1–16.8‰, respectively. These values reveal that the seawater sulfate is the most probable source of sulfur. The reduced sulfur was most likely supplied through thermochemical sulfate reduction. The sulfur isotope ratios of co-precipitated sphalerite–galena pairs suggest that deposition of the sulfide minerals took place under chemical disequilibrium conditions. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios of the galena samples represent average values of 18.08, 15.66, and 38.50, respectively. These ratios indicate that galena Pb likely originated from an orogenic source in which supracrustal rocks with high ²³⁸U/²⁰⁴Pb and ²³²Th/²⁰⁴Pb ratios are dominant. The average lead isotope model age portrays Cambrian age. This model age is not coeval with the host rocks, which are of middle Devonian age. It is probable that the pre-Middle Devonian model age shows the derivation of Pb from older sources either from host rocks of Cambrian age or from deposits previously formed in these rock units. The Pb isotopic composition of galena accords with the occurrence of an orogenic activity from Late Neoproterozoic to Lower Cambrian in Central Iran. The proposed genetic model considers the fact that mineralization formed in fractured and brecciated host rocks along shear zones and faults from metal-bearing connate waters that were discharged due to deformational dewatering of sediments.     

Constraints of C–O–S–Pb isotope compositions and Rb–Sr isotopic age on the origin of the Tianqiao carbonate-hosted Pb–Zn deposit,SW China

The Tianqiao Pb–Zn deposit in the western Yangtze Block, southwest China, is part of the Sichuan–Yunnan–Guizhou (SYG) Pb–Zn metallogenic province. Ore bodies are hosted in Devonian and Carboniferous carbonate rocks, structurally controlled by a thrust fault and anticline, and carried about 0.38 million tons Pb and Zn metals grading > 15% Pb + Zn. Both massive and disseminated Pb–Zn ores occur either as veinlets or disseminations in dolomitic rocks. They are composed of ore minerals, pyrite, sphalerite and galena, and gangue minerals, calcite and dolomite. δ³⁴S values of sulfide minerals range from + 8.4 to + 14.4‰ and display a decreasing trend from pyrite, sphalerite to galena (δ³⁴S_pyrite > δ³⁴S_sphalerite > δ³⁴S_galena). We interpret that reduced sulfur derived from sedimentary sulfate (gypsum and barite) of the host Devonian to Carboniferous carbonate rocks by thermal–chemical sulfate reduction (TSR). δ¹³C_PDB and δ¹⁸O_SMOW values of hydrothermal calcite range from –5.3 to –3.4‰ and + 14.9 to + 19.6‰, respectively, and fall in the field between mantle and marine carbonate rocks. They display a negative correlation, suggesting that CO₂ in the hydrothermal fluid was a mixture origin of mantle, marine carbonate rocks and sedimentary organic matter. Sulfide minerals have homogeneous and low radiogenic Pb isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 18.378 to 18.601, ²⁰⁷Pb/²⁰⁴Pb = 15.519 to 15.811 and ²⁰⁸Pb/²⁰⁴Pb = 38.666 to 39.571) that are plotted in the upper crust Pb evolution curve and overlap with that of Devonian to Carboniferous carbonate rocks and Proterozoic basement rocks in the SYG province. Pb isotope compositions suggest derivation of Pb metal from mixed sources. Sulfide minerals have ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.7125 to 0.7167, higher than Sinian to Permian sedimentary rocks and Permian Emeishan flood basalts, but lower than basement rocks. Again, Sr isotope compositions are supportive of a mixture origin of Sr. They have an Rb–Sr isotopic age of 191.9 ± 6.9Ma, possibly reflecting the timing of Pb–Zn mineralization. C–O–S–Pb–Sr isotope compositions of the Tianqiao Pb–Zn deposit indicate a mixed origin of ore-forming fluids, which have Pb–Sr isotope homogenized before the mineralization. The Permian flood basalts acted as an impermeable layer for the Pb–Zn mineralization hosted in the Devonian–Carboniferous carbonate rocks.     

扬子陆块北缘马元铅锌矿床成矿物质来源探讨: 来自C、O、H、S、Pb、Sr同位素地球化学的证据

呈层状、似层状产于震旦系灯影组角砾状白云岩层间构造带中的马元铅锌矿床是近年来在扬子陆块北缘铅锌找矿的新突破。文章通过碳、氧、氢、硫、铅和锶同位素地球化学特征研究,探讨了成矿流体和成矿金属来源。研究结果表明:矿石中热液脉石矿物的δ13CPDB为-4.24‰~0.93‰,δ18OSMOW为15.92‰~23.24‰,表明成矿流体中的CO2为震旦系碳酸盐岩的溶解成因。矿石中硫化物的δ34S变化于12.94‰~19.4‰之间;硫酸盐矿物的δ34S为32.2‰~33.48‰,表明还原硫主要来自地层中海相硫酸盐的还原。矿石硫化物的铅同位素组成均一,206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为17.62~18.02、15.49~15.63和37.57~38.35,成矿金属可能主要来源于震旦系—志留系。脉石矿物石英流体包裹体的δDFI为-92‰和-113‰,如果取成矿温度200℃,根据δ18O石英值计算的相应流体包裹体的δ18O水为6.03‰~12.73‰,推测成矿流体可能起源于大气降水为主的盆地卤水,或为其他来源的流体与有机质反应形成。成矿流体87Sr/86Sr为0.70967~0.71146,高于赋矿围岩震旦系灯影组白云岩锶同位素比值(0.70890~0.70945),表明成矿流体流经了古生代地层(及基底),并与其中具有高锶同位素比值的碎屑岩、页岩和泥岩等进行了水岩反应及同位素交换。     

Isotopes and Geochronology of the Meixian-type Pb-Zn-(Ag)Deposits,Central Fujian Rift,South China:Implications for Geological Events

Central Fujian Rift is another new and important volcanogenic massive sulfide Pb-Zn polymetallic metallogenetic belt. In order to find out the material genesis and mineralization period of Meixian-type Pb-Zn-Ag deposits, S and Pb isotope analysis and isotope geochronology of ores and wall rocks for five major deposits are discussed. It is concluded that the composition of sulfur isotope from sulfide ore vary slightly in different deposits and the mean value is close to zero with the 834S ranging from -3.5‰ to ＋5.6‰ averaging at ＋2.0‰, which indicates that the sulfur might originate from magma or possibly erupted directly from volcano or was leached from ore-hosted volcanic rock. The lead from ores in most deposits displays radioactive genesis character （206pb/204pb〉18.140, 207Pb/204pb〉15.584, 208pb/204pb〉38.569） and lead isotope values of ores are higher than those of wall rocks, which indicates that the lead was likely leached from the ore-hosted volcanic rocks. Based on isotope data, two significant Pb-Zn metallogenesis are delineated, which are Mid- and Late-Proterozoic sedimentary exhalative metailogenesis （The single zircon U-Pb, Sm-Nd isochronal and Ar-Ar dating ages of ore- hosted wall rocks are calculated to be among 933-1788 Ma.） and Yanshanian magmatic hydrothermal superimposed and alternated metallogenesis （intrusive SHRIMP zircon U-Pb and Rb-Sr isochronal ages between 127-154 Ma）.     

广东长坑-富湾超大型独立银矿床Rb-Sr定年及形成分析

长坑-富湾超大型银矿床主要产在下石炭统灰岩与上三叠统页岩断层不整合面下的硅质岩及灰岩中,矿化多为脉状,主要由石英、方解石、方铅矿、闪锌矿及银矿物组成。成矿流体Rb-Sr 等时线年龄为68±8.5Ma,表明成矿发生在59.5-76.5 Ma 之间。(87Sr/86Sr)I= 0.7164.成矿流体δ¹⁸O 在-0.86‰-4.1‰之间,δD 在-39.8‰-59‰之间,表明成矿流体为循环大气降水或建造水。银矿床铅同位素组成和产于中新元古代地层中茶洞银矿床方铅矿的铅同位素组成基本一致。据成矿年龄、成矿流体氢氧同位素组成及铅同位素组成特点,认为长坑-富湾超大型独立银矿床是晚白垩世至第三纪火山及次火山活动加热循环大气降水及建造水溶解深部矿源岩中经过早期成矿富集的成矿物质,迁移至灰岩与硅质岩及硅质岩与页岩界面时沉淀析出形成的。     

Geology and Isotope Geochemistry of the Yinchanggou-Qiluogou Pb-Zn Deposit, Sichuan Province, Southwest China

The Yinchanggou-Qiluogou Pb-Zn deposit,located in the western Yangtze Block,southwest China,is hosted by the Upper Sinian Dengying Formation dolostone.Ore bodies occur in the Qiluogou anticline and the NS-and NNW-trending faults.Sulfide ores mainly consist of sphalerite,pyrite,galena and calcite,with subordinate dolomite and quartz.Seventeen ore bodies have been discovered to date and they have a combined 1.0 million tons of sulfide ores with average grades of 2.27wt%Zn and 6.89wt%Pb.The δD_(H2O-SMOW) and δ~(18)O_(H2O-SMOW) values of fluid inclusions in quartz and calcite samples range from-68.9‰ to-48.7‰ and 7.3‰ to 15.9‰,respectively,suggesting that H_2O in the hydrothermal fluids sourced from metamorphic water.Calcite samples have δ~(13)C_(PDB) values ranging from-6.2‰ to-4.1‰ and δ~(18)O_(SMOW) values ranging from 15.1‰ to 17.4‰,indicating C and O in the hydrothermal fluids likely derived from a mixed source of metamorphic fluids and the host carbonates.The δ~(34)S_(CDT) values of sulfide minerals range from 5.5‰ to 20.3‰,suggesting that thermal chemical reduction of sulfate minerals in evaporates were the most probable source of S in the hydrothermal fluids.The ~(206)Pb/~(204)Pb,~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb ratios of sulfide minerals fall in the range of 18.11 to 18.40,15.66 to 15.76 and 38.25 to 38.88,respectively.The Pb isotopic data of the studied deposit plot near the upper crust Pb evolution curve and overlap with the age-corrected Proterozoic basement rocks and the Upper Sinian Dengying Formation hosting dolostone.This indicates that the Pb originated from a mixed source of the basement metamorphic rocks and the ore-hosting carbonate rocks.The ore geology and C-H-O-S-Pb isotopic data suggest that the YinchanggouQiluogou deposit is an unusual carbonate-hosted,strata-bound and epigenetic deposit that derived ore-forming materials from a mixed source of the underlying Porterozoic basements and the Sinian hosting carbonates.     

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

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 δ65CuNBS 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 to63Cu 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 δ65CuNBS and δ34SCDT values of chalcopyrite indicates that a common source of copper metal and sulfur from magma.δDH2OSMOW and δ18OH2O-SMOW 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 and206Pb/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.     

Ore genesis of the Tianbaoshan carbonate-hosted Pb–Zn deposit,Southwest China: geologic and isotopic (C–H–O–S–Pb) evidence

The Tianbaoshan Pb–Zn deposit, part of the Sichuan–Yunnan–Guizhou (SYG) Pb–Zn metallogenic province, is located in the western Yangtze Block and contains 2.6 million tonnes of 10–15 wt.% Pb + Zn metals. Ore bodies occur as vein or tubular types and are hosted in Sinian (late Proterozoic) carbonate rocks and are structurally controlled by the SN-trending Anninghe tectonic belt and NW-trending concealed fractures. The deposits are simple in mineralogy, with sphalerite, galena, pyrite, chalcopyrite, arsenopyrite, freibergite, and pyrargyrite as ore minerals and dolomite, calcite, and quartz as gangue minerals. These phases occur as massive, brecciated, veinlet, and dissemination in dolostone of the upper Sinian Dengying Formation. Hydrogen and oxygen isotope compositions of hydrothermal fluids range from –47.6 to –51.2‰ and –1.7 to +3.7‰, respectively. These data suggest that H₂O in hydrothermal fluids had a mixed origin of metamorphic and meteoric waters. Carbon and oxygen isotope compositions range from –6.5 to –4.9‰ and +19.3 to +20.2‰, respectively. These compositions plot in the field between mantle and marine carbonate rocks with a negative correlation, suggesting that CO₂ in the ore-forming fluids had multiple sources, including the Permian Emeishan flood basalts, Sinian-to-Permian marine carbonate rocks, and organic matters in Cambrian-to-Permian sedimentary rocks. Sulphur isotope compositions range from –0.4 to +9.6‰, significantly lower than Cambrian-to-Permian seawater sulphate (+15 to +35‰) and sulphate (+15 to +28‰) from evaporates in Cambrian-to-Permian strata, implicating that the S was derived from host-strata evaporates by thermal–chemical sulphate reduction. ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios range from 18.110 to 18.596, 15.514 to 15.878, and 38.032 to 39.221, respectively, which plot in field of the upper crust Pb evolution curve, unlike those of Proterozoic basement rocks, Sinian dolostone, Devonian-to-Permian carbonate rocks, and the Permian Emeishan flood basalts, implying complex derivation of Pb metal in the ore-forming fluids. Geological and isotopic studies of the Tianbaoshan Pb–Zn deposit reveal that constituents in the hydrothermal fluids were derived from multiple sources and that fluid mixing was a possible metallogenic mechanism. The studied deposit is not distal magmatic–hydrothermal, sedimentary exhalative (SEDEX), or Mississippi Valley (MVT) types, rather, it represents a unique ore deposit type, named in this article the SYG type.     

The origin of the Maozu carbonate-hosted Pb–Zn deposit,southwest China: Constrained by C–O–S–Pb isotopic compositions and Sm–Nd isotopic age

The Maozu Pb–Zn deposit, located on the western margin of the Yangtze Block, southwest China, is a typical carbonate-hosted deposit in the Sichuan–Yunnan–Guizhou Pb–Zn metallogenic province with Pb + Zn reserves of about 2.0 million tonnes grading 4.15 wt.% Pb and 7.25 wt.% Zn. Its ore bodies are hosted in Sinian (635–541 Ma) Dengying Formation dolostone and show stratiform, vein and irregular textures. Ores are composed of sphalerite, galena, pyrite, calcite, dolomite, quartz and fluorite with massive, banded, disseminated and veined structures. The C–O–Sm–Nd isotopic compositions of hydrothermal calcites and S–Pb isotopic compositions of sulfides were analyzed to constrain the origin of the Maozu deposit. δ¹³C_PDB and δ¹⁸O_SMOW values of hydrothermal calcites range from −3.7‰ to −2.0‰ and +13.8‰ to +17.5‰, respectively, and plot near the marine carbonate rocks field in a plot of δ¹³C_PDB vs. δ¹⁸O_SMOW, with a negative correlation. It suggests that CO₂ in the hydrothermal fluids was mainly originated from marine carbonate rocks, with limited influence from sedimentary organic matter. δ³⁴S_CDT values of sulfides range from +9.9‰ to +19.2‰, similar to that of Cambrian to Triassic seawater sulfate (+15‰ to +35‰) and evaporate (+15‰ to +30‰) in the Cambrian to Triassic sedimentary strata. It suggests that reduced sulfur was derived from evaporate in sedimentary strata by thermo chemical sulfate reduction. Sulfides have low radiogenic Pb isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 18.129–18.375, ²⁰⁷Pb/²⁰⁴Pb = 15.640–15.686 and ²⁰⁸Pb/²⁰⁴Pb = 38.220–38.577) that plot in the field between upper crust and the orogenic belt evolution curve in the plot of ²⁰⁷Pb/²⁰⁴Pb vs. ²⁰⁶Pb/²⁰⁴Pb, and similar to that of age corrected Proterozoic basement rocks (Dongchuan and Kunyang Groups). This indicates that ore-forming metals were mainly derived from basement rocks. Hydrothermal calcite yields a Sm–Nd isotopic age of 196 ± 13 Ma, possibly reflecting the timing of Pb–Zn mineralization in the SYG province, younger than the Permian Emeishan mantle plume (∼260 Ma). All data combined suggests that hydrothermal fluids circulated through basement rocks where they picked up metals and migrated to surface, mixed with reduced sulfur-bearing fluids and precipitated metals. Ore genesis of the Maozu deposit is different from known magmatic–hydrothermal, Sedimentary Exhalative or Mississippi Valley-types, which maybe represent a unique ore deposit type, named as the SYG-type.     

Genesis of the Changba–Lijiagou Giant Pb-Zn Deposit, West Qinling, Central China: Constraints from S-Pb-C-O isotopes

The extensive Changba-Lijiagou Pb-Zn deposit is located in the north of the Xihe–Chengxian ore cluster in West Qinling. The ore bodies are mainly hosted in the marble, dolomitic marble and biotite-calcite-quartz schist of the Middle Devonian Anjiacha Formation, and are structurally controlled by the fault and anticline. The ore-forming process can be divided into three main stages, based on field geological features and mineral assemblages. The mineral assemblages of hydrothermal stage I are pale-yellow coarse grain, low Fe sphalerite, pyrite with pits, barite and biotite. The mineral assemblages of hydrothermal stage II are black-brown cryptocrystalline, high Fe shalerite, pyrite without pits, marcasite or arsenopyrite replace the pyrite with pits, K-feldspar. The features of hydrothermal stage III are calcite-quartz-sulfide vein cutting the laminated, banded ore body. Forty-two sulfur isotope analyses, twenty-five lead isotope analyses and nineteen carbon and oxygen isotope analyses were determined on sphalerite, pyrite, galena and calcite. The δ34 S values of stage I(20.3 to 29.0‰) are consistent with the δ34 S of sulfate(barite) in the stratum. Combined with geological feature, inclusion characteristics and EPMA data, we propose that TSR has played a key role in the formation of the sulfides in stage I. The δ34 S values of stage II sphalerite and pyrite(15.1 to 23.0‰) are between sulfides in the host rock, magmatic sulfur and the sulfate(barite) in the stratum. This result suggests that multiple S reservoirs were the sources for S2-in stage II. The δ34 S values of stage III(13.1 to 22‰) combined with the structure of the geological and mineral features suggest a magmatic hydrothermal origin of the mineralization. The lead isotope compositions of the sulfides have 206 Pb/204 Pb ranging from 17.9480 to 17.9782, 207 Pb/204 Pb ranging from 15.611 to 15.622, and 208 Pb/204 Pb ranging from 38.1368 to 38.1691 in the three ore-forming stages. The narrow and symmetric distributions of the lead isotope values reflect homogenization of granite and mantle sources before the Pb-Zn mineralization. The δ13 CPDB and δ18 OSMOW values of stage I range from-0.1 to 2.4‰ and from 18.8 to 21.7‰. The values and inclusion data indicate that the source of fluids in stage I was the dissolution of marine carbonate. The δ13 CPDB and δ18 OSMOW values of stage II range from-4 to 1‰ and from 12.3 to 20.3‰, suggesting multiple C-O reservoirs in the Changba deposit and the addition of mantle-source fluid to the system. The values in stage III are-3.1‰ and 19.7‰, respectively. We infer that the process of mineralization involved evaporitic salt and sedimentary organic-bearing units interacting through thermochemical sulfate reduction through the isotopic, mineralogy and inclusion evidences. Subsequently, the geology feature, mineral assemblages, EPMA data and isotopic values support the conclusion that the ore-forming hydrothermal fluids were mixed with magmatic hydrothermal fluids and forming the massive dark sphalerite, then yielding the calcite-quartz-sulfide vein ore type at the last stage. The genesis of this ore deposit was epigenetic rather than the previously-proposed sedimentary-exhalative(SEDEX) type.     

Isotope geochemistry of Mississippi Valley Type stratabound F-Ba-(Pb-Zn) ores of Hammam Zriba (Province of Zaghouan,NE Tunisia)

The Hammam Zriba F-Ba-(Zn-Pb) ore deposit in the Province of Zaghouan in north-eastern Tunisia is hosted in the shallow dipping unconformity between green marls with chalky biomicritic limestones of Campanian age and Uppermost Jurassic carbonates. The mineralization consists mainly of fluorite and barite with minor sphalerite and galena. Calcite is the main gangue mineral. Two types of Zn-Pb sulfides can be distinguished according to the geometry of the orebodies, i.e., lenticular or stratiform ores, intra-karstic fillings. Sulfur isotope compositions (δ³⁴S) of barite range from 14.7 to 17.2‰, indicating that sulfur was derived from Triassic evaporites and the higher ones (19–25.7‰) are due to reservoir effect associated with thermo-chemical sulfate reduction (TSR) or bacterial sulfate reduction (BSR) under conditions of restricted sulfate supply. δ³⁴S of galena and sphalerite in lenticluar and intra-karstic orebodies range from −13.8 to 2.1‰, and could be explained by multiple sources of reduced sulfur: Triassic evaporites, diagenetic primary sulfides as well as sulfur from organic matter. Both TSR and BSR as potential contributors of sulfur are needed for sulfide precipitation. Lead isotope compositions of galena exhibit very similar: ²⁰⁶Pb/²⁰⁴Pb (18.858–18.876), ²⁰⁷Pb/²⁰⁴Pb (15.667–15.684), and ²⁰⁸Pb/²⁰⁴Pb (38.680–38.747) ratios, and plot between the upper crust and orogene average growth curves, reflecting involvement of a mixing and subsequent homogenization of Pb isotopic compositions of different source Pb reservoirs. The underlying Paleozoic basement rocks were the plausible source of metals. The economic ore (fluorite F1) mineralization was formed during the Eocene-Miocene compressional phase. During this deformation phase, deep-seated basinal brines have been circulated as hydrothermal fluids that have interacted with the Paleozoic rocks, thereby leaching metals, and have been channelized through subsidiary faults associated with the major regional NE–SW-trending deep-seated Zaghouan-Ressas fault. Hydrothermal fluids then migrated to the site of deposition where they got mixed with shallow, cooler, metal-depleted, TSR- and BSR-derived sulfur-rich fluids, which triggered the precipitation of the ores.     

Genesis of Pb–Zn Mineralization Beneath the Xiangshan Uranium Orefield,South China: Constraints from H–O–S–Pb Isotopes and Rb–Sr Dating

The volcanic‐hosted Xiangshan uranium orefield is the largest uranium deposit in South China. Recent exploration has discovered extensive Pb–Zn mineralization beneath the uranium orebodies. Detailed geological investigation reveals that the major metallic minerals include pyrite, sphalerite, galena, and chalcopyrite, whilst the major non‐metallic minerals include quartz, sericite, and calcite. New δ¹⁸O_fluid and δD_fluid data indicate that the ore‐forming fluids were mainly derived from magmatic, and the sulfide δ³⁴S values (2.2–6.9‰) suggest a dominantly magmatic sulfur source. The Pb isotope compositions are homogeneous (²⁰⁶Pb/²⁰⁴Pb = 18.120–18.233, ²⁰⁷Pb/²⁰⁴Pb = 15.575–15.698, and ²⁰⁸Pb/²⁰⁴Pb = 37.047–38.446). The ⁸⁷Sr/⁸⁶Sr ratios of sulfide minerals range from 0.7197 to 0.7204, which is much higher than volcanic rocks and fall into the range of metamorphic basement. Lead and strontium isotopic compositions indicate that the metallogenic materials probably were derived from metamorphic basement. Pyrite Rb–Sr dating of the ores yielded 131.3 ± 4.0 Ma, indicating that the Pb–Zn mineralization occurred in the Early Cretaceous.     

The nappe-hosted Hoshbulak MVT Zn–Pb deposit,Xinjiang, China: A review of the geological,elemental and stable isotopic constraints

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.     

湘西-黔东地区碳酸盐岩容矿铅锌矿床成矿模式

湘西-黔东地区位于扬子陆块东南缘,在该地区碳酸盐岩地层中,目前已发现大、中、小型铅锌矿床及矿点200余处.为了解湘西-黔东地区铅锌矿床成矿作用过程,系统总结了区内主要铅锌矿床地质与地球化学特征,并对成矿机制进行探讨,建立成矿模式.区内铅锌矿床主要赋存于下寒武统碳酸盐岩中,分布明显受断裂及褶皱构造控制,矿体主要为层状、似...     

Sulphur- and lead-isotope geochemistry of the Arapuçandere lead–zinc–copper deposit,Biga Peninsula,northwest Turkey

The Arapuçandere Pb–Zn–Cu ore body is a typical vein-type lead–zinc deposit of the Biga Peninsula, and is currently being mined for lead and zinc. In the study area, Permian–Triassic metamorphic rocks, Triassic metaclastic and metabasic rocks, Oligocene–Miocene granitoids, Miocene volcanic rocks, and Quaternary terrigenous sediments crop out. The ore deposits developed as Pb–Zn–Cu-bearing veins along faults in Triassic metasandstone and metadiabase. Microscopic studies reveal that the veins contain galena, sphalerite, chalcopyrite, pyrite, marcasite, covellite, and specular hematite as ore minerals, and quartz, calcite, and barite as gangue minerals. Analysed sulphur-isotope compositions (δ³⁴S_VCDT) of galena, sphalerite, and chalcopyrite range from ? 5.9 to ? 1.9‰ (average ? 3.4‰), from ? 5.5 to ? 1.7‰ (average ? 4.2 ‰), and from ? 3.5 to ? 0.9‰ (average ? 2.6‰), respectively; that of H₂S in the hydrothermal fluid was in the calculated range of ? 5.8 to +0.1‰ (average ? 2.5‰). These isotopic values suggest that magmatic sulphur dominates in sulphides, mixed with minor, isotopically light sulphur. Because no contemporaneous magmatic activity is associated with mineralization, it may be assumed that sulphur was leached from the surrounding Triassic units, mainly from metabasic, partly from metaclastic rocks. Lead-isotope studies indicate a model age of 114–63 Ma for the lead reservoir, in accord with possible sulphur-bearing local source rocks. Thus, the sulphur and lead deposited in the studied ore veins were probably leached from Triassic metabasic and metaclastic rocks some time during the Early Cretaceous to the Palaeocene.     

Cadmium and sulfur isotopic compositions of the Tianbaoshan Zn–Pb–Cd deposit,Sichuan Province,China

Although Zn–Pb deposits are one of the most important Cd reservoirs in the earth, few studies have focused on the Cd isotopic fractionation in Zn–Pb hydrothermal systems. This study investigates the causes and consequences of cadmium and sulfur isotope fractionation in a large hydrothermal system at the Tianbaoshan Zn–Pb–Cd deposit from the Sichuan–Yunnan–Guizhou (SYG) metallogenic province, SW China. Moderate variations in Cd and S isotope compositions have been measured in sphalerite cover a distance of about 78 m. Sphalerite has δ^114/110Cd values ranging from 0.01 to 0.57‰, and sulfides (sphalerite, galena and chalcopyrite) have δ³⁴S_CDT values ranging from 0.2 to 5.0‰. Although δ³⁴S_CDT and δ^114/110Cd values in sphalerites have no regular spatial variations, the δ³⁴S_CDT values in galena and calculated ore-forming fluid temperatures decreased from 2.1 to 0.2‰ and from about 290 to 130 °C, respectively, from the bottom to the top of the deposit. Heavy Cd isotopes are enriched in early precipitated sphalerite in contrast to previous studies. We suggest that Cd isotopic compositions in ore-forming fluids are heterogeneous, which result in heavy Cd isotope enrichment in early precipitated sphalerite. In comparison with other Zn–Pb deposits in the SYG area, the Tianbaoshan deposit has moderate Cd contents and small isotope fractionation, suggesting differences in origin to other Zn–Pb deposits in the SYG province.In the Tianbaoshan deposit, the calculated δ³⁴S∑_S-fluids value is 4.2‰, which is not only higher than the mantle-derived magmatic sulfur (0 ± 3‰), but also quite lower than those of Ediacaran marine sulfates (about 30 to 35‰). Thus, we suggest that reduced sulfur of ore-forming fluids in the deposit was mainly derived from the leaching of the basement, which contains large amount of volcanic or intrusive rocks. Based upon a combination of Cd and S isotopic systems, the Tianbaoshan deposit has different geochemical characteristics from typical Zn–Pb deposits (e.g., the Huize deposit) in SYG area, indicating the unique origin of this deposit.     

Geology and Geochemistry of the Bianbianshan Au‐Ag‐Cu‐Pb‐Zn Deposit,Southern Da Hinggan Mountains,Northeastern China

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.     

The origin of the Dapingzhang volcanogenic Cu–Pb–Zn ore deposit,Yunnan province,SW China: Constraints from host rock geochemistry and ore Os–Pb–S–C–O–H isotopes

The Dapingzhang volcanogenic Cu–Pb–Zn sulfide deposit is located in the Lancangjiang tectonic zone within the Sanjiang region, Yunnan province of southwestern China. The deposit occurs within a felsic volcanic dome belonging to a mid-Silurian volcanic belt stretching for more than 100 km from Dapingzhang to Sandashan. The mineralized volcanic rocks are predominantly keratophyre and quartz keratophyre with subordinate spilite. The Dapingzhang deposit is characterized by well-developed vertical zonation with stockwork ores in the bottom, disseminated sulfide ores in the middle, and massive sulfide ores in the top, overlain by a thin layer of chemical sedimentary exhalative rocks (chert and barite). The Re–Os age of the pyrites from the deposit is 417 ± 23 Ma, indistinguishable from the age of the associated felsic volcanic rocks. The associated felsic volcanic rocks are characterized by negative Nb–Ta anomalies and positive ε_Nd(t) values (+ 4.4–+6.5), similar to the coeval calc-alkaline volcanic rocks in the region. This observation supports the interpretation that the felsic volcanic rocks associated with the Dapingzhang deposit are the derivatives of arc basaltic magma by extensive fractional crystallization. The δ³⁴S values of the sulfides from the deposit vary from − 1.24 to + 4.32‰, indicating a predominantly magmatic source for the sulfur. The sulfides are also characterized by homogeneous and relatively low radiogenic Pb isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 18.310–18.656, ²⁰⁷Pb/²⁰⁴Pb = 15.489–15.643 and ²⁰⁸Pb/²⁰⁴Pb = 37.811–38.662), similar to the Pb isotopic compositions of the associated volcanic rocks. The Pb isotopic data indicate that mantle-derived Pb is more prevalent than crust-derived Pb in the deposit. The S–Pb isotopic data indicate that the important ore-forming materials were mainly derived from the associated volcanic rocks. The δ¹³C_PDB and δ¹⁸O_SMOW values of the associated hydrothermal calcite crystals vary from − 2.3‰ to + 0.27‰ and from + 14.6 to + 24.4‰, respectively. These values are between the mantle and marine carbonate values. The narrow range of the δ¹³C_PDB values for the calcite indicates that carbon-bearing species in the hydrothermal fluids were primarily derived from marine carbonates. The δ¹⁸O values for the hydrothermal fluids, calculated from the measured values for quartz, are between − 2.1‰ and + 3.5‰. The corresponding δD values for the fluids range from − 59‰ to − 84‰. The O–H isotopic data indicate mixing between magmatic fluids and seawater in the ore-forming hydrothermal system. Similar to a typical volcanogenic massive sulfide (VMS) deposit, the ore-forming fluids contained both magmatic fluids and heated seawater; the ore metals and regents were derived from the underlying magma as well as felsic country rocks.