Analyses of fluid\|inclusion leachates from ore deposits show that Na/Br ratios are within the range of 75-358 and Cl/Br 67-394, respectively, and this variation trend coincides with the seawater evaporation trajector...Analyses of fluid\|inclusion leachates from ore deposits show that Na/Br ratios are within the range of 75-358 and Cl/Br 67-394, respectively, and this variation trend coincides with the seawater evaporation trajectory on the basis of the Na/Br and Cl/Br ratios. The average Cl/Br and Na/Br ratios of mineralizing fluids are 185 and 173 respectively, which are very close to the ratios (120 and 233) of the residual evaporated seawater past the point of halite precipitation. It is suggested that the original mineralizing brine was derived from highly evaporated seawater with a high salinity. However, the inclusion fluids have absolute Na values of \{69.9\}-\{2606.2\} mmol kg\+\{-1\} and Cl values of \{106.7\}-\{1995.5\} mmol kg\+\{-1\}. Most of the values are much less than those of seawater: Na, 485 mmol kg\+\{-1\} and Cl, 566 mmol kg\+\{-1\}, respectively; the salinity measured from fluid inclusions of the deposits ranges from \{2.47 wt%\} to \{15.78 wt%\} NaCl equiv. The mineralizing brine has been diluted. The \{δ\{\}\+\{18\}O\} and δD values of ore\|forming fluids vary from \{-8.21‰\} to \{9.51‰\} and from \{-40.3‰\} to \{-94.3‰\}, respectively. The δD values of meteoric water in this region varied from \{-80‰\} to \{-100‰\} during the Jurassic. This evidenced that the ore\|forming fluids are the mixture of seawater and meteoric water. Highly evaporated seawater was responsible for leaching and extracting Pb, Zn and Fe, and mixed with and diluted by descending meteoric water, which resulted in the formation of ores.展开更多
Mississippi Valley-type(MVT) Zn-Pb deposits predominantly form within both orogenic forelands and fold-andthrust belts, yet the mineralization process within the latter tectonic setting remains inadequately understood...Mississippi Valley-type(MVT) Zn-Pb deposits predominantly form within both orogenic forelands and fold-andthrust belts, yet the mineralization process within the latter tectonic setting remains inadequately understood. This study, through a comprehensive review of MVT deposits across global fold-and-thrust belts, introduces a novel model elucidating the mineralization process in the context of tectonic belt evolution. It is demonstrated that during the stage Ⅰ, regional compression is introduced by early stages of plate convergence, causing the folding and thrusting and creating structural or lithological traps such as evaporite diapirs and unconformity-related carbonate dissolution-collapse structures. Thereafter, in stage Ⅱ, hydrocarbons begin to migrate and accumulate within these traps, where reduced sulfur is generated through thermochemical or bacterial sulfate reduction concurrent with or preceding Zn-Pb mineralization. In the subsequent stage Ⅲ, as plate convergence persists, the regional stress transitions from compression to transpression or extension. Under these conditions, steeply-dipping extensional faults are generated, facilitating the ascent of metalliferous brines into early-formed structural or lithological traps. Precipitation of Zn and Pb sulfides occurs through the mixing of Zn-Pb-transporting fluids with pre-existing reduced sulfur or by interaction with hydrocarbons.展开更多
The Tethyan domain hosts the world's most abundant hydrocarbon and Mississippi Valley-type(MVT) Pb-Zn resources. The relations among organic matter-rich sediments, MVT Pb-Zn mineralization, and the Tethyan tectoni...The Tethyan domain hosts the world's most abundant hydrocarbon and Mississippi Valley-type(MVT) Pb-Zn resources. The relations among organic matter-rich sediments, MVT Pb-Zn mineralization, and the Tethyan tectonic evolution history are an important scientific issue. The data of paleogeographic reconstruction indicate that the Proto-, Paleo-, and NeoTethys oceans mainly lay in low latitude areas between 30°N and 45°S. The high temperature and precipitation and the lack of sea water overturning in stagnant basins resulted in high marine biological productivity and good preservation conditions for organic matter-rich sediments. Consequently, abundant organic matter-rich sediments were developed and preserved in the Tethyan domain and thus created abundant hydrocarbon resources. Mineralization age data demonstrate that MVT deposits mainly formed during the continent-continent convergence in the late stage of the Tethyan tectonic evolution. Deposits are located in the fold-and-thrust belts and forelands of the continent-continent convergence orogen, and spatially associated with hydrocarbon basins. Organic matter-rich sediments are well developed in MVT ore districts, where hydrocarbon activity appeared earlier than or nearly simultaneous with the Pb-Zn mineralization event. Hydrocarbon activity generally began earlier than the Pb-Zn mineralization in individual deposits. Organic matter-rich sediments and hydrocarbons mainly play the role of reducing agents in the MVT Pb-Zn mineralization process. Through bacterial or thermal reduction, dissolved sulfates from sedimentary strata were reduced to generate reduced sulfur for Pb-Zn sulfide mineralization. In summary, the Tethyan oceans have long been in low latitude areas near the equator, making the Tethyan domain develop abundant organic matterrich sediments and associated hydrocarbon resources which reduce sulfates to provide sufficient reduced sulfur for MVT PbZn mineralization in the region.展开更多
The carbonate-hosted Pb–Zn deposits in the Sanjiang metallogenic belt on the Tibetan Plateau are typical of MVT Pb–Zn deposits that form in thrust-fold belts. The Jiamoshan Pb–Zn deposit is located in the Changdu a...The carbonate-hosted Pb–Zn deposits in the Sanjiang metallogenic belt on the Tibetan Plateau are typical of MVT Pb–Zn deposits that form in thrust-fold belts. The Jiamoshan Pb–Zn deposit is located in the Changdu area in the middle part of the Sanjiang belt, and it represents a new style of MVT deposit that was controlled by karst structures in a thrust–fold system. Such a karst-controlled MVT Pb–Zn deposit in thrust settings has not previously been described in detail, and we therefore mapped the geology of the deposit and undertook a detailed study of its genesis. The karst structures that host the Jiamoshan deposit were formed in Triassic limestones along secondary reverse faults, and the orebodies have irregular tubular shapes. The main sulfide minerals are galena, sphalerite, and pyrite that occur in massive and lamellar form. The ore-forming fluids belonged to a Mg2+–Na+–K+–SO2-4–Cl-–F-–NO-3–H2 O system at low temperatures(120–130°C) but with high salinities(19–22% NaCl eq.). We have recognized basinal brine as the source of the ore-forming fluids on the basis of their H–O isotopic compositions(-145‰ to-93‰ for δDV-SMOW and-2.22‰ to 13.00‰ for δ18 Ofluid), the ratios of Cl/Br(14–1196) and Na/Br(16–586) in the hydrothermal fluids, and the C–O isotopic compositions of calcite(-5.0‰ to 3.7‰ for δ13 CV-PDB and 15.1‰ to 22.3‰ for δ18 OV-SMOW). These fluids may have been derived from evaporated seawater trapped in marine strata at depth or from Paleogene–Neogene basins on the surface. The δ34 S values are low in the galena(-3.2‰ to 0.6‰) but high in the barite(27.1‰), indicating that the reduced sulfur came from gypsum in the regional Cenozoic basins and from sulfates in trapped paleo-seawater by bacterial sulfate reduction. The Pb isotopic compositions of the galena samples(18.3270–18.3482 for 206 Pb/204 Pb, 15.6345–15.6390 for 207 Pb/204 Pb, and 38.5503–38.5582 for 208 Pb/204 Pb) are similar to those of the regional Triassic volcanic-arc rocks that formed during the closure of the Paleo-Tethys, indicating these arc rocks were the source of the metals in the deposit. Taking into account our new observations and data, as well as regional Pb–Zn metallogenic processes, we present here a new model for MVT deposits controlled by karst structures in thrust–fold systems.展开更多
Mississippi Valley-type(MVT)Pb-Zn deposits serve as the world’s major supply of Pb-Zn resources.However,the age constraint of MVT Pb-Zn deposits has long been a big challenge,due to the lack of minerals that are uneq...Mississippi Valley-type(MVT)Pb-Zn deposits serve as the world’s major supply of Pb-Zn resources.However,the age constraint of MVT Pb-Zn deposits has long been a big challenge,due to the lack of minerals that are unequivocally related to ore deposition and that can be used for radioisotopic dating.Here we show sporopollens can provide useful chronological information on the Changdong MVT Pb-Zn deposit in the Simao basin,Sanjiang belt,West China.The Pb-Zn ores in the Changdong deposit are hosted by internal sediments in paleo-karst caves of meteoric origin.Sphalerite and galena occur as replacements of carbonate minerals and void infillings in the internal sediments.The relations suggest that the Pb-Zn mineralization occurred after the deposition of the internal sediments.A palynological assemblage mainly composed of angiosperm pollen dominated by Castanea,Quercus,and Carya and fern spores dominated by Polypodiaceae,Pteris,and Athyriaceae was identified.These pollen and spores place the ore-hosting internal sediments and the Changdong paleo-karst at early to middle Oligocene.Consequently,the Changdong Pb-Zn deposit must have formed after the early Oligocene(~34 Ma).These age constraints,together with the geological characteristics,indicate that the Changdong Pb-Zn deposit is a paleo-karst-controlled MVT deposit related to fold-thrust systems in the Sanjiang belt.The Changdong deposit is similar to other MVT Pb-Zn deposits in the northern part of the Sanjiang belt,making it possible to extend this Pb-Zn belt 500 km further to the South.Results presented here highlights the potential of sporopollens in dating the age of MVT deposits related to paleo-karst formation in young orogenic belts.展开更多
为查明太行山东麓铁铜铅锌等多金属矿成矿带的成矿地质条件,在大古石沟地区相继开展了1∶50000矿产地质调查、1∶50000水系沉积物测量、1∶50000高精度磁法测量和1∶50000电法测量工作。在圈定物化探异常和矿化有利地段的基础上,利用1∶...为查明太行山东麓铁铜铅锌等多金属矿成矿带的成矿地质条件,在大古石沟地区相继开展了1∶50000矿产地质调查、1∶50000水系沉积物测量、1∶50000高精度磁法测量和1∶50000电法测量工作。在圈定物化探异常和矿化有利地段的基础上,利用1∶10000地质草测、1∶10000地物化探综合剖面测量和槽探工程等,开展了系统的矿产调查分析。综合研究表明:①大古石沟铅锌矿赋存于中寒武统张夏组和上寒武统三山子组碳酸盐岩地层中,是一种碳酸盐岩容矿的低温热液型矿床,属层控矿床,具有密西西比河谷型(Mississippi Valley Type,MVT)矿床特征;②矿体主要有2种形态,一种呈脉状、透镜状、囊肿状赋存于NNE向、NWW向断裂带中,一种呈层状、似层状、不规则状、透镜状、窝状等赋存于近水平的层间顺层破碎带中,角砾岩化、白云岩化共同构成了铅锌矿床围岩蚀变的主要形式;③地表共发现了铁、铜、铅锌矿(化)脉31条(层),其中,具有价值的铜铅锌多金属矿化体3条、含铅重晶石脉3条,初步圈定了2条工业矿体,富矿体延伸长度可达2000 m以上,矿体总厚度达10~12 m,Pb品位高达3.9%~10.26%,矿体远景资源量可达中小型矿床规模。在上述分析的基础上,根据矿区地质特征、物化探特征及含矿特征,初步划分了大古石沟、小东沟和普泉等3个有利的成矿区段,具有较好的找矿潜力。可见,采用地质调查、物化探扫面、大比例尺地质填图及物化探综合剖面测量、槽探揭露等方法,具有良好的找矿效果。展开更多
This study reports the sphalerite Rb-Sr age and LA-MC-ICP-MS in situ sulfur isotope analysis results of the Daliangzi Lead-Zinc Deposit in the Sichuan-Yunnan-Guizhou （SYG） triangle. Sphalerite Rb-Sr dating yields a ...This study reports the sphalerite Rb-Sr age and LA-MC-ICP-MS in situ sulfur isotope analysis results of the Daliangzi Lead-Zinc Deposit in the Sichuan-Yunnan-Guizhou （SYG） triangle. Sphalerite Rb-Sr dating yields a Mississippian age of 345.2±3.6 Ma （MSWD=I.4）, which is older than the published Late Triassic mineralization ages （230-200 Ma） of some other deposits. This indicates that at least two stages of lead-zinc mineralization have occurred in the SYG lead-zinc triangle. The first stage occurred in the Mississippian under an extensional environment, while the second stage occurred in the Late Triassic under a compressional environment. In situ sulfur isotope analysis of sphalerite growth zoning presents relatively large δ^34S values of 11.3‰-15.2‰ with small variations. The large δ^34S values indicate a reduced sulfur source of thermochemical reduction of seawater sulfates. Abundant organic matter in the black fracture zone possibly supplied reductants for thermochemical sulfate reduction （TSR） at the mineralization site. The small variation of δ^34S values suggests a slow and stable TSR process that could prevent the sudden supersaturation of sphalerite in the fluid and the resulting of fast participation. This is consistent with the well-crystallized characteristic of the sphalerite of the Daliangzi Deposit.展开更多
基金ThisresearchprojectwasfundedbytheNationalNaturalScienceFoundationofChina (No .4 0 1 72 0 39)
文摘Analyses of fluid\|inclusion leachates from ore deposits show that Na/Br ratios are within the range of 75-358 and Cl/Br 67-394, respectively, and this variation trend coincides with the seawater evaporation trajectory on the basis of the Na/Br and Cl/Br ratios. The average Cl/Br and Na/Br ratios of mineralizing fluids are 185 and 173 respectively, which are very close to the ratios (120 and 233) of the residual evaporated seawater past the point of halite precipitation. It is suggested that the original mineralizing brine was derived from highly evaporated seawater with a high salinity. However, the inclusion fluids have absolute Na values of \{69.9\}-\{2606.2\} mmol kg\+\{-1\} and Cl values of \{106.7\}-\{1995.5\} mmol kg\+\{-1\}. Most of the values are much less than those of seawater: Na, 485 mmol kg\+\{-1\} and Cl, 566 mmol kg\+\{-1\}, respectively; the salinity measured from fluid inclusions of the deposits ranges from \{2.47 wt%\} to \{15.78 wt%\} NaCl equiv. The mineralizing brine has been diluted. The \{δ\{\}\+\{18\}O\} and δD values of ore\|forming fluids vary from \{-8.21‰\} to \{9.51‰\} and from \{-40.3‰\} to \{-94.3‰\}, respectively. The δD values of meteoric water in this region varied from \{-80‰\} to \{-100‰\} during the Jurassic. This evidenced that the ore\|forming fluids are the mixture of seawater and meteoric water. Highly evaporated seawater was responsible for leaching and extracting Pb, Zn and Fe, and mixed with and diluted by descending meteoric water, which resulted in the formation of ores.
基金funded by National Natural Science Foundation of China (Grant Nos. 42125204, 92155305, 42103068, 42372114, 42372115)。
文摘Mississippi Valley-type(MVT) Zn-Pb deposits predominantly form within both orogenic forelands and fold-andthrust belts, yet the mineralization process within the latter tectonic setting remains inadequately understood. This study, through a comprehensive review of MVT deposits across global fold-and-thrust belts, introduces a novel model elucidating the mineralization process in the context of tectonic belt evolution. It is demonstrated that during the stage Ⅰ, regional compression is introduced by early stages of plate convergence, causing the folding and thrusting and creating structural or lithological traps such as evaporite diapirs and unconformity-related carbonate dissolution-collapse structures. Thereafter, in stage Ⅱ, hydrocarbons begin to migrate and accumulate within these traps, where reduced sulfur is generated through thermochemical or bacterial sulfate reduction concurrent with or preceding Zn-Pb mineralization. In the subsequent stage Ⅲ, as plate convergence persists, the regional stress transitions from compression to transpression or extension. Under these conditions, steeply-dipping extensional faults are generated, facilitating the ascent of metalliferous brines into early-formed structural or lithological traps. Precipitation of Zn and Pb sulfides occurs through the mixing of Zn-Pb-transporting fluids with pre-existing reduced sulfur or by interaction with hydrocarbons.
基金supported by the National Natural Science Foundation of China (Grant Nos. 92155305, 91855214, and 42125204)the National Key R&D Plan (Grant No. 2021YFC2901805)。
文摘The Tethyan domain hosts the world's most abundant hydrocarbon and Mississippi Valley-type(MVT) Pb-Zn resources. The relations among organic matter-rich sediments, MVT Pb-Zn mineralization, and the Tethyan tectonic evolution history are an important scientific issue. The data of paleogeographic reconstruction indicate that the Proto-, Paleo-, and NeoTethys oceans mainly lay in low latitude areas between 30°N and 45°S. The high temperature and precipitation and the lack of sea water overturning in stagnant basins resulted in high marine biological productivity and good preservation conditions for organic matter-rich sediments. Consequently, abundant organic matter-rich sediments were developed and preserved in the Tethyan domain and thus created abundant hydrocarbon resources. Mineralization age data demonstrate that MVT deposits mainly formed during the continent-continent convergence in the late stage of the Tethyan tectonic evolution. Deposits are located in the fold-and-thrust belts and forelands of the continent-continent convergence orogen, and spatially associated with hydrocarbon basins. Organic matter-rich sediments are well developed in MVT ore districts, where hydrocarbon activity appeared earlier than or nearly simultaneous with the Pb-Zn mineralization event. Hydrocarbon activity generally began earlier than the Pb-Zn mineralization in individual deposits. Organic matter-rich sediments and hydrocarbons mainly play the role of reducing agents in the MVT Pb-Zn mineralization process. Through bacterial or thermal reduction, dissolved sulfates from sedimentary strata were reduced to generate reduced sulfur for Pb-Zn sulfide mineralization. In summary, the Tethyan oceans have long been in low latitude areas near the equator, making the Tethyan domain develop abundant organic matterrich sediments and associated hydrocarbon resources which reduce sulfates to provide sufficient reduced sulfur for MVT PbZn mineralization in the region.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFC0600306)the National Natural Science Foundation of China(Grant Nos 41773042,41922022,41773043,41772088,91962105 and 41702082)+1 种基金the independent research project from Key Laboratory of DeepEarth Dynamics of the Ministry of Natural Resources(Grant No.J1901-6)the IGCP-662 program。
文摘The carbonate-hosted Pb–Zn deposits in the Sanjiang metallogenic belt on the Tibetan Plateau are typical of MVT Pb–Zn deposits that form in thrust-fold belts. The Jiamoshan Pb–Zn deposit is located in the Changdu area in the middle part of the Sanjiang belt, and it represents a new style of MVT deposit that was controlled by karst structures in a thrust–fold system. Such a karst-controlled MVT Pb–Zn deposit in thrust settings has not previously been described in detail, and we therefore mapped the geology of the deposit and undertook a detailed study of its genesis. The karst structures that host the Jiamoshan deposit were formed in Triassic limestones along secondary reverse faults, and the orebodies have irregular tubular shapes. The main sulfide minerals are galena, sphalerite, and pyrite that occur in massive and lamellar form. The ore-forming fluids belonged to a Mg2+–Na+–K+–SO2-4–Cl-–F-–NO-3–H2 O system at low temperatures(120–130°C) but with high salinities(19–22% NaCl eq.). We have recognized basinal brine as the source of the ore-forming fluids on the basis of their H–O isotopic compositions(-145‰ to-93‰ for δDV-SMOW and-2.22‰ to 13.00‰ for δ18 Ofluid), the ratios of Cl/Br(14–1196) and Na/Br(16–586) in the hydrothermal fluids, and the C–O isotopic compositions of calcite(-5.0‰ to 3.7‰ for δ13 CV-PDB and 15.1‰ to 22.3‰ for δ18 OV-SMOW). These fluids may have been derived from evaporated seawater trapped in marine strata at depth or from Paleogene–Neogene basins on the surface. The δ34 S values are low in the galena(-3.2‰ to 0.6‰) but high in the barite(27.1‰), indicating that the reduced sulfur came from gypsum in the regional Cenozoic basins and from sulfates in trapped paleo-seawater by bacterial sulfate reduction. The Pb isotopic compositions of the galena samples(18.3270–18.3482 for 206 Pb/204 Pb, 15.6345–15.6390 for 207 Pb/204 Pb, and 38.5503–38.5582 for 208 Pb/204 Pb) are similar to those of the regional Triassic volcanic-arc rocks that formed during the closure of the Paleo-Tethys, indicating these arc rocks were the source of the metals in the deposit. Taking into account our new observations and data, as well as regional Pb–Zn metallogenic processes, we present here a new model for MVT deposits controlled by karst structures in thrust–fold systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.41922022,41773042,41773043,41772088,and 41472067)the Strategic Priority Research Program of Chinese Academy of Sciences,China(Grant No.XDA20070304)+2 种基金the Key Laboratory of Deep-Earth Dynamics of the Ministry of Natural Resources(Grant No.J1901-6)the Basic Scientific Research Foundation of the Institute of Geology,Chinese Academy of Geological Sciences(Grant No.2105)the IGCP-662 Program。
文摘Mississippi Valley-type(MVT)Pb-Zn deposits serve as the world’s major supply of Pb-Zn resources.However,the age constraint of MVT Pb-Zn deposits has long been a big challenge,due to the lack of minerals that are unequivocally related to ore deposition and that can be used for radioisotopic dating.Here we show sporopollens can provide useful chronological information on the Changdong MVT Pb-Zn deposit in the Simao basin,Sanjiang belt,West China.The Pb-Zn ores in the Changdong deposit are hosted by internal sediments in paleo-karst caves of meteoric origin.Sphalerite and galena occur as replacements of carbonate minerals and void infillings in the internal sediments.The relations suggest that the Pb-Zn mineralization occurred after the deposition of the internal sediments.A palynological assemblage mainly composed of angiosperm pollen dominated by Castanea,Quercus,and Carya and fern spores dominated by Polypodiaceae,Pteris,and Athyriaceae was identified.These pollen and spores place the ore-hosting internal sediments and the Changdong paleo-karst at early to middle Oligocene.Consequently,the Changdong Pb-Zn deposit must have formed after the early Oligocene(~34 Ma).These age constraints,together with the geological characteristics,indicate that the Changdong Pb-Zn deposit is a paleo-karst-controlled MVT deposit related to fold-thrust systems in the Sanjiang belt.The Changdong deposit is similar to other MVT Pb-Zn deposits in the northern part of the Sanjiang belt,making it possible to extend this Pb-Zn belt 500 km further to the South.Results presented here highlights the potential of sporopollens in dating the age of MVT deposits related to paleo-karst formation in young orogenic belts.
文摘为查明太行山东麓铁铜铅锌等多金属矿成矿带的成矿地质条件,在大古石沟地区相继开展了1∶50000矿产地质调查、1∶50000水系沉积物测量、1∶50000高精度磁法测量和1∶50000电法测量工作。在圈定物化探异常和矿化有利地段的基础上,利用1∶10000地质草测、1∶10000地物化探综合剖面测量和槽探工程等,开展了系统的矿产调查分析。综合研究表明:①大古石沟铅锌矿赋存于中寒武统张夏组和上寒武统三山子组碳酸盐岩地层中,是一种碳酸盐岩容矿的低温热液型矿床,属层控矿床,具有密西西比河谷型(Mississippi Valley Type,MVT)矿床特征;②矿体主要有2种形态,一种呈脉状、透镜状、囊肿状赋存于NNE向、NWW向断裂带中,一种呈层状、似层状、不规则状、透镜状、窝状等赋存于近水平的层间顺层破碎带中,角砾岩化、白云岩化共同构成了铅锌矿床围岩蚀变的主要形式;③地表共发现了铁、铜、铅锌矿(化)脉31条(层),其中,具有价值的铜铅锌多金属矿化体3条、含铅重晶石脉3条,初步圈定了2条工业矿体,富矿体延伸长度可达2000 m以上,矿体总厚度达10~12 m,Pb品位高达3.9%~10.26%,矿体远景资源量可达中小型矿床规模。在上述分析的基础上,根据矿区地质特征、物化探特征及含矿特征,初步划分了大古石沟、小东沟和普泉等3个有利的成矿区段,具有较好的找矿潜力。可见,采用地质调查、物化探扫面、大比例尺地质填图及物化探综合剖面测量、槽探揭露等方法,具有良好的找矿效果。
基金financially supported by the China Geological Survey (No. 12120114019701)the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan)
文摘This study reports the sphalerite Rb-Sr age and LA-MC-ICP-MS in situ sulfur isotope analysis results of the Daliangzi Lead-Zinc Deposit in the Sichuan-Yunnan-Guizhou （SYG） triangle. Sphalerite Rb-Sr dating yields a Mississippian age of 345.2±3.6 Ma （MSWD=I.4）, which is older than the published Late Triassic mineralization ages （230-200 Ma） of some other deposits. This indicates that at least two stages of lead-zinc mineralization have occurred in the SYG lead-zinc triangle. The first stage occurred in the Mississippian under an extensional environment, while the second stage occurred in the Late Triassic under a compressional environment. In situ sulfur isotope analysis of sphalerite growth zoning presents relatively large δ^34S values of 11.3‰-15.2‰ with small variations. The large δ^34S values indicate a reduced sulfur source of thermochemical reduction of seawater sulfates. Abundant organic matter in the black fracture zone possibly supplied reductants for thermochemical sulfate reduction （TSR） at the mineralization site. The small variation of δ^34S values suggests a slow and stable TSR process that could prevent the sudden supersaturation of sphalerite in the fluid and the resulting of fast participation. This is consistent with the well-crystallized characteristic of the sphalerite of the Daliangzi Deposit.
