Noble Gas and Stable Isotopic Constraints on the Origin of the Ag–Cu Polymetallic Ore Deposits in the Baiyangping Area,Yunnan Province,SW China

The Lanping basin, Yunnan province, SW China, is located at the juncture of the Eurasian and Indian Plates in the eastern part of the Tibetan Plateau. The Lanping basin, in the Sanjiang Tethyan metallogenic province, is a significant Cu–Ag–Zn–Pb mineralized belt in China that includes the largest sandstone‐hosted Zn–Pb deposit in the world, the Jinding deposit, as well as several Ag–Cu deposits (the Baiyangping and Jinman deposits). These deposits, with total reserves of over 16.0 Mt Pb + Zn, 0.6 Mt Cu, and 7,000 t Ag, are mainly hosted in Meso‐Cenozoic clastic rocks and are dominantly controlled by two Cenozoic thrust systems developed in the western and eastern segments of the basin. The Baiyangping, Babaoshan, and Hetaoqing ore deposits are representative of the epithermal base metal deposits in the Lanping basin. The microthermometric data show that the ore‐forming fluids for these deposits were low temperature (110–180 °C) and had bimodal distribution of salinity at moderate and mid to high salinities (approximately 2–8 wt.% and 18–26 wt.% NaCl equivalent). The C and O isotope data indicate that the ore‐forming fluids were related to hot basin brines. We present new He and Ar isotope data on volatiles released from fluid inclusions contained in sulfides and in barite in these three deposits. ³He/⁴He ratios of the ore‐forming fluids are 0.01 to 0.14 R/Ra with a mean of 0.07 Ra (where R is the ³He/⁴He ratio and Ra is the ratio for atmospheric helium). This mean value is intermediate to typical ³He/⁴He ratios for the crust (R/Ra = 0.01 to 0.05) and the ratio for air‐saturated water (R/Ra = 1). The mean ratio is also significantly lower than the ratios found for mantle‐derived fluids (R/Ra = 6 to 9). The ⁴⁰Ar/³⁶Ar ratios of the ore‐forming fluids range from 298 to 382 with a mean of 323. This value is slightly higher than that for the air‐saturated water (295.5). The ³He/⁴He ratios of fluids from the fluid inclusions imply that the ore‐forming fluid for the Baiyangping, Babaoshan, and Hetaoqing deposits was derived from the crust and that any mantle‐derived He was negligible. The content of the radiogenic Ar ranges between 0.2 to 20.4%, and the proportion of air‐derived ⁴⁰Ar averages 94.1%. This indicates that atmospheric Ar was important in the formation of these deposits but that some radiogenic ⁴⁰Ar was derived from crustal rocks. Based on these observations coupled with other geochemical evidence, we suggest that the ore‐forming fluids responsible for the formation of the Ag–Cu–Pb–Zn polymetallic ore deposits in the Baiyangping area of the Lanping basin were mainly derived from crustal fluids. The fluids may have mixed with some amount of air‐saturated water, but there was no significant involvement of mantle‐derived fluids.     

He–Ar Isotopic Tracing of Pyrite from Ore-forming Fluids of the Sanshandao Au Deposit, Jiaodong Area

The Sanshandao Au deposit is located in the famous Sanshandao metallogenic belt, Jiaodong area. To date, accumulative Au resources of 1000 t have been identified from the belt. Sanshandao is a world-class gold deposit with Au mineralization hosted in Early Cretaceous Guojialing-type granites. Thus, studies on the genesis and ore-forming element sources of the Sanshandao Au deposit are crucial. He and Ar isotopic analyses of fluid inclusions from pyrite(the carrier of Au) indicate that the fluid inclusions have 3 He/4 He=0.043–0.21 Ra with an average of 0.096 Ra and 40 Ar/36 Ar=488–664 with an average of 570.8. These values represent the initial He and Ar isotopic compositions of ore-forming fluids for trapped fluid inclusions. The comparison of H–O isotopic characteristics combined with deposit geology and wall rock alteration reveals that the ore-forming fluids of the Sanshandao Au deposit show mixed crust–mantle origin characteristics, and they mainly comprise crust-derived fluid mixed with minor mantle-derived fluid and meteoric water during the uprising process. The ore-forming elements were generally sourced from pre-Cambrian meta-basement rocks formed by Mesozoic reactivation and mixed with minor shallow crustal and mantle components.     

金顶超大型铅锌矿床的成矿金属来源——来自铅同位素组成的制约

金顶矿床是世界著名的超大型铅锌矿床,其巨量的金属堆积引起许多学者对成矿金属来源的关注。前人通过铅同位素示踪研究,提出了成矿金属来自地幔、上地壳、下地壳及不同端员混合等不同认识。理论分析表明,这些观点认识的差异可能源于不同作者分析铅同位素数据存在测试误差。基于此,笔者在金顶矿床选择了7个代表性硫化物样品,再次进行了铅同位素分析。结果显示,矿床铅同位素组成为~(206)Pb/~(204)Pb=18.3945~18.4429、~(207)Pb/~(204)Pb=15.6412~15.6583、~(208)Pb/~(204)Pb=38.6266~38.6772,在铅同位素演化模式图解(Zartman et al.,1979)中数据点分布集中,处于"造山带"和"上地壳"演化曲线之间,未显示出明显的线性分布特点,表明金顶矿床成矿金属来源主要为壳源;区域对比表明,金顶矿床明显比白秧坪矿带铅锌矿床贫放射性成因铅,而与区域VMS型矿床铅同位素组成更为接近,这表明金顶矿床与白秧坪矿带矿床有着不同的金属物源区,其金属可能来自盆地底部晚三叠世火山岩或其内早期的VMS矿化。     

He-Ar Isotopic Systematics of Fluid Inclusions in Pyrites from PGEpolymetallic Deposits in Lower Cambrian Black Rock Series, South China

He-Ar isotopic compositions of fluid inclusions trapped in pyrites from some representative PGE-polymetallic deposits in Lower Cambrian black rock series in South China were analyzed by using an inert gas isotopic mass spectrometer. The results show that the ore-forming fluids possess a low 3He/4He ratio, varying from 0.43×10-8 to 26.39×10-8, with corresponding R/Ra value of 0.003-0.189. The 40Ar/36Ar ratios are 258-287, close to those of air saturated water (ASW). He-Ar isotopic indicator studies show that the ore-forming fluids were mainly derived from the formation water or basinal hot brine and sea water, while the content of mantle-derived fluid or deep-derived magmatic water might be negligible. The PGE-polymetallic mineralization might be related to the evolution of the Caledonian miogeosynclines distributed along the southern margin of the Yangtze Craton. During the Early Cambrian, the formation water or basinal hot brine trapped in Caledonian basins which accumulated giant thick sediments was     

He-Ar-S-Pb Isotopic Compositions of Pyrite: Constraints on the Source of Ore-forming Materials of the Chengchao Skarn Iron Deposit, SE Hubei Province, Eastern China

The Chengchao iron deposit,the largest high-grade skarn iron deposit in southeastern Hubei Province,contains considerable amounts of magnetite and by-product anhydrite.To obtain better understanding of the ore-formation process,this study carried out He-Ar-S-Pb multi-isotopic analyses on the pyrites formed during two stages of mineralization.The results indicate that the δ~(34)S values(ranging from 14.0‰ to 17.6‰) of pyrites formed from the two stages have no obvious differences,suggesting that they were not derived from a single magmatic sulfur source.The δ~(34)S values of anhydrite mostly range from 21.9‰ to 28.4‰,similar to that of the Middle Triassic sedimentary anhydrite in the Middle-Lower Yangtze River metallogenic belt(MLYRB).The Pb isotopic compositions of the pyrites of both stages are homogeneous,with values of ~(208)Pb/~(204)Pb,~(207)Pb/~(204)Pb,and~(206)Pb/~(204)Pb being 38.006-38.257,15.523-15.556,and 17.806-18.052,respectively,indicating a mixed crust-mantle source.The He-Ar results exhibit different compositions of the two stages:the ~3He/~4He(R/Ra) and ~(40)Ar/~(36)Ar values for the early-stage pyrite are 0.46-0.63 and 311-322,respectively,whereas the values for late-stage pyrite are 0.23-0.34 and 305-361,respectively.Both stages of pyrites indicate the multiple sources of the ore-forming fluids,with decreasing amount of magmatic water and increasing amount of modified meteoric water(MASW) during fluid evolution.The Triassic evaporites played an important role in the mineralization process.     

河南桐柏老湾金矿床氢氧氦同位素地球化学及成矿流体来源

河南桐柏老湾金矿床的成矿作用是在变基性火山碎屑沉积岩为矿源层的背景上演化的。本文根据矿床氢氧同位素研究,认为矿床的热液成矿期成矿流体为大气降水和老湾花岗岩岩浆水的混合,成矿Ⅰ阶段和Ⅱ阶段以岩浆水为主,成矿Ⅲ阶段以大气降水为主,但在成矿Ⅱ阶段大气降水已占有很大的比例。氦同位素分析表明,在老湾金矿形成过程中有地幔流体加入,且从成矿Ⅱ阶段至Ⅲ阶段,由于大气降水比例增大,其与地幔流体的混合导致成矿流体的³He/⁴He比值不断减小。     

Geology and Isotope Geochemistry of the Dongzhongla Pb–Zn Deposit in Tibet: Implications for the Origin of the Ore‐Forming Fluids and Storage Condition of Certain Metals

As a newly discovered medium‐sized deposit (proven Pb + Zn resources of 0.23 Mt, 9.43% Pb and 8.73% Zn), the Dongzhongla skarn Pb–Zn deposit is located in the northern margin of the eastern Gangdese, central Lhasa block. Based on the geological conditions in this deposit of ore‐forming fluids, H, O, C, S, Pb, Sr, and noble gas isotopic compositions were analyzed. Results show that δ¹⁸O_SMOW of quartz and calcite ranged from −9.85 to 4.17‰, and δD_SMOW ranged from −124.7 to −99.6‰ (where SMOW is the standard mean ocean water), indicating magma fluids mixed with meteoric water in ore‐forming fluids. The δ¹³C_PDB and δ¹⁸O_SMOW values of calcite range from −1.4 to −1.1‰ and from 5.3 to 15.90‰, respectively, show compositions consistent with the carbonate limestone in the surrounding rocks, implying that the carbon was primarily sourced from the dissolution of carbonate strata in the Luobadui Formation. The ore δ³⁴S composition varied in a narrow range of 2.8 to 5.7‰, mostly between 4‰ and 5‰. The total sulfur isotopic value δ³⁴S was 4.7‰ with characteristics of magmatic sulfur. The ³He/⁴He values of pyrite and galena ranged from 0.101 to 5.7 Ra, lower than those of mantle‐derived fluids (6 ± 1 Ra), but higher than those of the crust (0.01–0.05 Ra), and therefore classified as a crust–mantle mixed source. The Pb isotopic composition for ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb values of the ores were in the ranges of 18.628–18.746, 15.698–15.802, and 39.077–39.430, respectively, consistent with the Pb isotopic composition of magmatic rocks in the deposit, classified as upper‐crust lead. The ore lead was likely sourced partially from the crustal basement of the Lhasa Terrane. The initial (⁸⁷Sr/⁸⁶Sr)_i value from five sulfide samples ranged from 0.71732 to 0.72767, and associated ore‐forming fluids were mainly sourced from the partial melting of the upper‐crust materials. Pb isotopic compositions of ore sulfides from the Dongzhongla deposit are similar to that of the Yuiguila and Mengya'a deposit, indicating that they have similar sources of metal‐rich ore‐forming solution. According to basic skarn mineralogy, the economic metals, and the origin of the ore‐forming fluids, the Dongzhongla deposit was classified as a skarn‐type Pb–Zn deposit.     

S and Pb Isotopic Constraints on the Relationship between the Linong Granodiorite and the Yangla Copper Deposit,Yunnan, China

The Yangla copper deposit, located in western Yunnan Province, China, is a typical giant, newly started mining copper deposit with an estimated Cu reserves of about 1,200,000 tons. The deposit is spatially and temporally associated with the Linong granodiorite, which is rich in SiO2 (SiO2=58.25 wt%–69.84 wt%) and alkalis (Na2O+K2O=5.98 wt%–8.34 wt%), indicating an association with shoshonitic series to high-K calc-alkaline series granites, and shows low contents of TiO2 (0.35 wt%–0.48 wt%), MgO (1.51 wt%–1.72 wt%), and Al2O3 (13.38 wt%–19.75 wt%). The δ34S values of sulfides of the main ore stage from copper ores vary range from ?4.2‰ to ?0.9‰, indicating a much greater contribution from the mantle to the ore-forming fluids. The δ34S values of the late ore stage is ?9.8‰, indicating enrichment of biogenic sulfur which may derive from the crustal hydrothermal fluid. The 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb of sulfides of the main ore stage from copper ores range within 38.66–38.73, 15.71–15.74 and 18.35–19.04, respectively, implying that the Pb was derived from the mantle, with the crustal component, probably representing mixtures of mantle lead and crustal lead. Sulfide of the late ore stage in their Pb isotopic composition, 208Pb/204Pb= 38.69, 207Pb/204Pb=15.70, 206Pb/204Pb=18.35, implying that the Pb was derived from the crust. The Linong granodiorite is syn-collisional, produced by partial melting of thickened lower crust, which was triggered by the westward subduction of the Jinshajiang Oceanic plate. During a transition in geodynamic setting from collision-related compression to extension, gently dipping ductile shear zones (related to subduction) were transformed to brittle shear zones, consisting of a series of thrust faults in the Jinshajiang tectonic belt. The tensional thrust faults would have been a favorable environment for ore-forming fluids. The ascending magma provided a channel for the ore-forming fluid from the mantle wedge. After the magma arrived at the base of the early-stage Linong granodiorite, the platy granodiorite at the base of the body would have shielded the late-stage magma from the fluid. The magma would have cooled slowly, and some of the ore-forming fluid in the magma would have entered the gently dipping thrust faults near the Linong granodiorite, resulting in mineralization.     

Fluid Inclusions and Hydrogen,Oxygen, and Lead Isotopes of the Antuoling Molybdenum Deposit,Northern Taihang Mountains,China

The Antuoling Mo deposit is a major porphyry‐type deposit in the polymetallic metallogenic belt of the northern Taihang Mountains, China. The processes of mineralization in this deposit can be divided into three stages: an early quartz–pyrite stage, a middle quartz–polymetallic sulfide stage, and a late quartz–carbonate stage. Four types of primary fluid inclusions are found in the deposit: two‐phase aqueous inclusions, daughter‐mineral‐bearing multiphase inclusions, CO₂–H₂O inclusions, and pure CO₂ inclusions. From the early to the late ore‐forming stages, the homogenization temperatures of the fluid inclusions are 300 to >500°C, 270–425°C, and 195–330°C, respectively, with salinities of up to 50.2 wt%, 5.3–47.3 wt%, and 2.2–10.4 wt% NaCl equivalent, revealing that the ore‐forming fluids changed from high temperature and high salinity to lower temperature and lower salinity. Moreover, based on the laser Raman spectra, the compositions of the fluid inclusions evolved from the NaCl–CO₂–H₂O to the NaCl–H₂O system. The δ¹⁸O_H2O and δD values of quartz in the deposit range from +3.9‰ to +7.0‰ and ?117.5‰ to ?134.2‰, respectively, reflecting the δD of local meteoric water after oxygen isotopic exchange with host rocks. The Pb isotope values of the sulfides (²⁰⁸Pb/²⁰⁴Pb, 36.320–37.428; ²⁰⁷Pb/²⁰⁴Pb, 15.210–15.495; ²⁰⁶Pb/²⁰⁴Pb, 16.366–17.822) indicate that the ore‐forming materials originated from a mixed upper mantle–lower crust source.     

A Study of Ore-forming Fluids in the Shimensi Tungsten Deposit, Dahutang Tungsten Polymetallic Ore Field, Jiangxi Province, China

The Dahutang tungsten polymetallic ore field is located north of the Nanling W-Sn polymetallic metallogenic belt and south of the Middle—Lower Yangtze River Valley Cu-Mo-Au-Fe porphyry-skarn belt.It is a newly discovered ore field,and probably represents the largest tungsten mineralization district in the world.The Shimensi deposit is one of the mineral deposits in the Dahutang ore field,and is associated with Yanshanian granites intruding into a Neoproterozoic granodiorite batholith.On the basis of geologic studies,this paper presents new petrographic,microthermometric,laser Raman spectroscopic and hydrogen and oxygen isotopic studies of fluid inclusions from the Shimensi deposit.The results show that there are three types of fluid inclusions in quartz from various mineralization stages:liquid-rich two-phase fluid inclusions,vapor-rich two-phase fluid inclusions,and three-phase fluid inclusions containing a solid crystal,with the vast majority being liquid-rich two-phase fluid inclusions.In addition,melt and melt-fluid inclusions were also found in quartz from pegmatoid bodies in the margin of the Yanshanian intrusion.The homogenization temperatures of liquid-rich two-phase fluid inclusions in quartz range from 162 to 363℃ and salinities are 0.5wt%-9.5wt%NaCI equivalent.From the early to late mineralization stages,with the decreasing of the homogenization temperature,the salinity also shows a decreasing trend.The ore-forming fluids can be approximated by a NaCl-H_2O fluid system,with small amounts of volatile components including CO_2,CH_4 and N_2,as suggested by Laser Raman spectroscopic analyses.The hydrogen and oxygen isotope data show that δ5D_(V-smow) values of bulk fluid inclusions in quartz from various mineralization stages vary from-63.8‰ to-108.4‰,and the δ~(18)O_(H2O) values calculated from the δ~(18)O_(V-)smow values of quartz vary from-2.28‰ to 7.21‰.These H-O isotopic data are interpreted to indicate that the ore-forming fluids are mainly composed of magmatic water in the early stage,and meteoric water was added and participated in mineralization in the late stage.Integrating the geological characteristics and analytical data,we propose that the ore-forming fluids of the Shimensi deposit were mainly derived from Yanshanian granitic magma,the evolution of which resulted in highly differentiated melt,as recorded by melt and melt-fluid inclusions in pegmatoid quartz,and high concentrations of metals in the fluids.Cooling of the ore-forming fluids and mixing with meteoric water may be the key factors that led to mineralization in the Dahutang tungsten polymetallic ore field.     

Stable Isotopic Geochemical and Geochronological Constraints on the Formation of the Shihu Gold Deposit: The Intracontinental Metallogeny of the Taihang Tectonic Belt,Eastern China

The Early Cretaceous Shihu gold deposit is located in the northern segment of the Taihang Tectonic belt, which extends across the central part of the North China Craton. The deposit is hosted predominantly by the Archean metamorphic crystalline units, and is spatially and temporally related to quartz diorite porphyry present extensively throughout the gold deposit. We studied the geology, geochronology and stable isotopic geochemistry. Zircon U–Pb LA–ICP–MS ages of the quartz diorite porphyry at deposit range from 134 ± 1 to 131 ± 2 Ma, which are coeval and probably genetically related to the mineralization. The majority of the sulfides of the gold deposit have δ³⁴S values ranging from ?1 to 2‰, which suggest an homogeneous magmatic source. In addition, the isotopic compositions of δ¹⁸O_fluid and δ¹⁸D_fluid vary from 2.1 to 7.0‰ and ?93 to ?65‰, respectively, suggesting that the magmatic fluids mingled with meteoric water. The Pb isotopic analyses reveal that both the ore‐forming materials and the quartz diorite porphyry originated from the lower crust and may have been mixed with mantle material. The ⁸⁷Sr/⁸⁶Sr_i and ¹⁴³Nd/¹⁴⁴Nd (¹⁴³Nd/¹⁴⁴Nd)_i ratios for the quartz diorite porphyry demonstrate that there was mixing of two end‐member (crust and the mantle) isotopic compositions. These results suggest that the ore‐forming fluids and materials were derived from lower‐crustal melting induced by mantle processes. Processes associated with the formation of the Shihu gold deposit differ significantly from those that characterize orogenic gold deposits, and instead are representative of formation in an intracontinental tectonic environment.     

Geology and D-O-C Isotope Systematics of the Tieluping Silver Deposit,Henan, China: Implications for Ore Genesis

The Tieluping silver deposit, which is sited along NE-trending faults within the high-grade metamorphic basement of the Xiong‘er terrane, is part of an important Mesozoic orogenic-type Ag-Pb and Au belt recently discovered. Ore formation includes three stages: Early (E), Middle (M) and Late (L), which include quartz-pyrite (E),polymetallic sulfides (M) and carbonates (L), respectively. The E-stage fluids are characterized by δD=-90%c,δ^13CCO2=2.0‰ and δ^18O=9‰ at 373℃, and are deeply sourced; the L-stage fluids, with δD=-70‰, δ^13C CO2=-1.3%c and δ^18O=-2‰, are shallow-sourced meteoric water; whereas the M-stage fluids, with δD=-109‰, δ^13C CO2=0.1%c and δ^18O2‰, are a mix of deep-sourced and shallow-sourced fluids. Comparisons of the D-O-C isotopic systematics of the Estage ore-forming fluids with the fluids derived from Mesozoic granites, Archean-Paleoproterozoic metamorphic basement and Paleo-Mesoproterozoic Xiong‘er Group, show that these units cannot generate fluids with the measured isotopic composition (high δ^180 and δ^13C ratios and low δD ratios) characteristic of the ore-forming fluids. This suggests that the E-stage ore-forming fluids originated from metamorphic devolatilization of a carbonate-shale-chert lithological association, locally rich in organic matter, which could correspond to the Meso-Neoproterozoic Guandaokou and Luanchuan Groups, rather than to geologic units in the Xiong‘er terrane, the lower crust and the mantle. This supports the view that the rocks of the Guandaokou and Luanchuan Groups south of the Machaoying fault might be the favorable sources. A tectonic model that combines collisional orogeny, metallogeny and hydrothermal fluid flow is proposed to explain the formation of the Tieluping silver deposit. During the Mesozoic collision between the South and North China paleocontinents, a crustal slab containing a lithological association consisting of carbonate-shale-chert, locally rich in organic matter (carbonaceous shale) was thrust northwards beneath the Xiong‘er terrane along the Machaoying fault.Metamorphic devolatilization of this underthrust slab provided the ore-forming fluids to develop the Au-Ag-(Pb-Zn) ore belt, which includes the Tieluping silver deposit.     

Ore Genesis and Tectonic Significance of the Xiaojiashan Tungsten Deposit,Eastern Tianshan,Xinjiang, China: Evidence from Geology,Fluid Inclusions,and Stable Isotope Geochemistry

The Xiaojiashan tungsten deposit is located about 200 km northwest of Hami City, the Eastern Tianshan orogenic belt, Xinjiang, northwestern China, and is a quartz vein‐type tungsten deposit. Combined fluid inclusion microthermometry, host rock geochemistry, and H–O isotopic compositions are used to constrain the ore genesis and tectonic setting of the Xiaojiashan tungsten deposit. The orebodies occur in granite intrusions adjacent to the metamorphic crystal tuff, which consists of the second lithological section of the first Sub‐Formation of the Dananhu Formation (D₂d ₁²). Biotite granite is the most widely distributed intrusive bodies in the Xiaojiashan tungsten deposit. Altered diorite and metamorphic crystal tuff are the main surrounding rocks. The granite belongs to peraluminous A‐type granite with high potassic calc‐alkaline series, and all rocks show light Rare Earth Element (REE)‐enriched patterns. The trace element characters suggest that crystallization differentiation might even occur in the diagenetic process. The granite belongs to postcollisional extension granite, and the rocks formed in an extensional tectonic environment, which might result from magma activity in such an extensional tectonic environment. Tungsten‐bearing quartz veins are divided into gray quartz vein and white quartz veins. Based on petrography observation, fluid inclusions in both kinds of vein quartz are mainly aqueous inclusions. Microthermometry shows that gray quartz veins have 143–354°C of T_h, and white quartz veins have 154–312°C of T_h. The laser‐Raman test shows that CO₂ is found in fluid inclusions of the tungsten‐bearing quartz veins. Quadrupole mass spectrometry reveals that fluid inclusions contain major vapor‐phase contents of CO₂, H₂O. Meanwhile, fluid inclusions contain major liquid‐phase contents of Cl^?, Na⁺. It can be speculated that the ore‐forming fluid of the Xiaojiashan tungsten deposit is characterized by an H₂O–CO₂, low salinity, and H₂O–CO₂–NaCl system. The range of hydrogen and oxygen isotope compositions indicated that the ore‐forming fluids of the tungsten deposit were mainly magmatic water. The ore‐forming age of the Xiaojiashan deposit should to be ~227 Ma. During the ore‐forming process, the magmatic water had separated from magmatic intrusions, and the ore‐bearing complex was taken to a portion where tungsten‐bearing ores could be mineralized. The magmatic fluid was mixed by meteoric water in the late stage.     

Geologic, fluid inclusion and isotopic characteristics of the Jinding Zn–Pb deposit, western Yunnan, South China: A review

With a reserve of  200 Mt ore grading 6.08% Zn and 1.29% Pb (i.e., a metal reserve of  15 Mt) hosted in Cretaceous and Tertiary terrestrial rocks, the Jinding deposit is the largest Zn–Pb deposit in China, and also the youngest sediment-hosted super giant Zn–Pb deposit in the world. The deposit mainly occurs in the Jinding dome structure as tabular orebodies within breccia-bearing sandstones of the Palaeocene Yunlong Formation (autochthonous) and in the overlying sandstones of the Early Cretaceous Jingxing Formation (allochthonous). The deposit is not stratiform and no exhalative sedimentary rocks have been observed. The occurrence of the orebodies, presence of hangingwall alteration, and replacement and open-space filling textures all indicate an epigenetic origin. Formation of the Jinding Zn–Pb deposit is related to a period of major continental crust movement during the collision of the Indian and Eurasian Plates. The westward thrusts and dome structure were successively developed in the Palaeocene sedimentary rocks in the ore district, and Zn–Pb mineralisation appears to have taken place in the early stage of the doming processes.The study of fluid inclusions in sphalerite and associated gangue minerals (quartz, celestine, calcite and gypsum) shows that homogenisation temperatures ranged from 54 to 309 °C and cluster around 110 to 150 °C, with salinities of 1.6 to 18.0 wt.% NaCl equiv. Inert gas isotope studies from inclusions in ore- and gangue-minerals reveal 2.0 to 15.6% mantle He, 53% mantle Ne and a considerable amount of mantle Xe in the ore-forming fluids. The Pb-isotope composition of ores shows that the metal is mainly of mantle origin, mixed with a lesser amount of crustal lead. The widely variable and negative δ³⁴S values of Jinding sulphides suggest that thermo-chemical or bacterial sulphate reduction produced reduced sulphur for deposition of the Zn–Pb sulphides. The mixing of a mantle-sourced fluid enriched in metals and CO₂ with reduced sulphide-bearing saline formation water in a structural–lithologic trap may have been the key mechanism for the formation of the Jinding deposit.The Jinding deposit differs from known major types of sediment-hosted Zn–Pb deposits in the world, including sandstone-type (SST), Mississippi Valley type (MVT) and sedimentary-exhalative (SEDEX). Although the fine-grained ore texture and high Zn/Pb ratios are similar to those in SEDEX deposits, the Jinding deposit lacks any exhalative sedimentary rocks. Like MVT deposits, Jinding is characterised by simple mineralogy, epigenetic features and involvement of basinal brines in mineralisation, but its host rocks are mainly sandstones and breccia-bearing sandstones. The Jinding deposit is also different from SST deposits with its high Zn/Pb ratios, among other characteristics. Most importantly, the Jinding deposit was formed in an intracontinental terrestrial basin with an active tectonic history in relation to plate collision, and mantle-sourced fluids and metals played a major role in ore formation, which is not the case for SEDEX, MVT, and SST. We propose that Jinding represents a new type of sediment-hosted Zn–Pb deposit, named the ‘Jinding type’.     

云南白秧坪银多金属矿集区成矿流体特征及成矿机制

云南白秧坪银多金属矿集区是滇西兰坪盆地内新发现的矿集区,属东特提斯—喜马拉雅成矿域的一部分。通过流体包裹体的类型、均一温度和盐度的研究分析,结合流体包裹体的化学成分和C、H、O同位素资料及成矿地质条件的综合分析,提出流体包裹体主要具有盆地沉积卤水及大气降水的特征,但成矿流体具有壳幔混合来源的特征。这些特征与该区特定的地质背景和演化历史密切相关。兰坪盆地是在澜沧江和金沙江两条深大断裂之间发展起来的一个拉分盆地,这两条深断裂连同盆地中央的中轴断裂,不仅控制了盆地的发生和发展过程,而且也控制了盆地内成矿流体的来源及银、铜等多金属矿床的成矿作用。因此认为成矿作用是流体混合作用、有机质和膏盐地层的还原作用等综合作用的结果。     

山东招远金翅岭金矿床H,O,He,Ar同位素组成及其对成矿流体示踪的研究

金翅岭金矿是位于胶东西北部招莱成矿带内的一个中型石英脉型金矿床,受招平断裂带下盘次级NE-NNE向密集构造裂隙带控制,成矿围岩为玲珑花岗岩和郭家岭花岗闪长岩。本文通过对成矿作用过程中的贯通性矿物石英H,O同位素及黄铁矿中流体包裹体He,Ar同位素进行研究,探讨了成矿流体的来源。研究表明:金翅岭金矿床成矿流体的氢、氧同位素组成存在明显的变化趋势,10件样品的氢氧同位素组成δD值变化于-74.80‰～-95.70‰之间,平均值-85.41‰;δ18 O值变化于+1.30‰～+11.12‰之间,平均值为+4.95‰。分析结果显示,成矿流体早期以岩浆水为主,晚期主要为岩浆水和大气降水的混合。黄铁矿流体包裹体3 He/4 He值为0.09R/Ra～1.51R/Ra,平均0.72R/Ra,位于地壳氦和地幔氦之间。根据成矿流体的壳幔二元混合模式进行计算:地幔流体参与成矿的比例为7.49%～11.85%,地壳流体占主导地位。40 Ar/36 Ar值为365.9～4 042.6,集中在地壳流体与地幔流体之间,大气饱和水的范围附近。结合H-O同位素的结果可知,金翅岭金矿床成矿流体是以地壳流体占主导地位的壳幔混合流体,而地壳流体端元又是岩浆水和大气降水的混合流体,并且大气降水参与成矿流体的比例随着成矿作用从早到晚,以及成矿流体由深到浅的运移而不断增多。     

S, C, O, H Isotope Data and Noble Gas Studies of the Maoniuping LREE Deposit, Sichuan Province, China： A Mantle Connection for Mineralization

The Maoniuping REE deposit, located about 22 km to the southwest of Mianning, Sichuan Province, is the second largest light REE deposit in China, subsequent to the Bayan Obo Fe-Nb-REE deposit in the Inner Mongolia Autonomous Region. Tectonically, it is located in the transitional zone between the Panxi rift and the Longmenshan-Jinpingshan orogenic zone. It is a carbonatite vein-type deposit hosted in alkaline complex rocks. The bastnaesite-barite, bastnaesite-calcite, and bastnaesite-microcline lodes are the main three types of REE ore lodes. Among these, the first lode is distributed most extensively and its REE mineralization is the strongest. Theδ34Sv-CDT values of the barites in the ore of the deposit vary in a narrow range of +5.0 to +5.1‰in the bastnaesite-calcite lode and +3.3 to +5.9‰in the bastnaesite-barite lode, showing the isotopic characteristics of magma-derived sulfur. Theδ13Cv-PDB values and theδ518OV-SMOW values in the bastnaesite-calcite lode range from -3.9 to -6.9‰and from +7.3 to +9.7‰, respectively, which fall into the range of "primary carbonatites", showing that carbon and oxygen in the ores of the Maoniuping deposit were derived mainly from a deep source. Theδ13Cv-PDB values of fluid inclusions vary from -3.0 to -5.6‰, with -3.0 to -4.0‰in the bastnaesite-calcite lode and -3.0 to -5.6‰in the bastnaesite-barite lode, which show characteristics of mantle-derived carbon. TheδDv-SMOW values of fluid inclusions range from -57 to -88‰, with -63 to -86‰in the bastnaesite-calcite lode and -57 to -88‰in the bastnaesite-barite lode, which show characteristics of mantle-derived hydrogen. Theδ18OH2OV-SMOW values vary from +7.4 to +8.6‰in the bastnaesite calcite lode, and +6.7 to +7.8‰in the bastnaesite-barite lode, almost overlapping the range of +5.5 to +9.5‰for magmatic water. The 4He content, R/Ra ratios are (13.95 to 119.58×10-6 (cm3/g)STP and 0.02 to 0.11, respectively, and 40Ar/36Ar is 313±1 to 437±2. Considering the 4He increase caused by high contents of radioactive elements, a mantle-derived fluid probably exists in the inclusions in the fluorite, calcite and bastnaesite samples. The Maoniuping deposit and its associated carbonatite-alkaline complex were formed in 40.3 to 12.2 Ma according to K-Ar and U-Pb data. All these data suggest that large quantities of mantle fluids were involved in the metallogenic process of the Maoniuping REE deposit through a fault system.     

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

In Kamchatka, Central Koryak, Central Kamchatka and East Kamchatka metallogenic belts are distributed from northwest to southeast. K–Ar age, sulfur isotopic composition of sulfide minerals, and bulk chemical compositions of ores were analyzed for 13 ore deposits including hydrothermal gold‐silver and base metal, in order to elucidate the geological time periods of ore formation, relationship to regional volcanic belts, type of mineralization, and origin of sulfur in sulfides. The dating yielded ore‐forming ages of 41 Ma for the Ametistovoe deposit in the Central Koryak, 17.1 Ma for the Zolotoe deposit and 6.9 Ma for the Aginskoe deposit in the Central Kamchatka, and 7.4 Ma for the Porozhistoe deposit and 5.1 Ma for the Vilyuchinskoe deposit in the East Kamchatka metallogenic belt. The data combined with previous data of ore‐forming ages indicate that the time periods of ore formation in these metallogenic belts become young towards the southeast. The averaged δ³⁴S_CDT of sulfides are ?2.8‰ for the Ametistovoe deposit in Central Koryak, ?1.8‰ to +2.0‰ (av. ?0.1‰) for the Zolotoe, Aginskoe, Baranievskoe and Ozernovskoe deposits in Central Kamchatka, and ?0.7 to +3.8‰ (av. +1.7‰) for Bolshe‐Bannoe, Kumroch, Vilyuchinskoe, Bystrinskoe, Asachinskoe, Rodnikovoe, and Mutnovskoe deposits in East Kamchatka. The negative δ³⁴S_CDT value from the Ametistovoe deposit in Central Koryak is ascribed to the contamination of ³²S‐enriched sedimentary sulfur in the Ukelayat‐Lesnaya River trough of basement rock. Comparison of the sulfur isotope compositions of the mineral deposits shows similarity between the Central Koryak and Magadan metallogenic belts, and East Kamchatka and Kuril Islands belts. The Central Kamchatka belt is intermediate between these two groups in term of sulfur isotopic composition.     

The origin of the Tongkeng-Changpo tin deposit,Dachang metal district,Guangxi, China: clues from fluid inclusions and He isotope systematics

Tongkeng-Changpo is the largest tin deposit within the giant Dachang polymetallic tin ore field in Guangxi, southern China, which is part of a large skarn system associated with Cretaceous granitoids. The Tongkeng-Changpo mineralization consists of veins and stockworks in the upper levels and replacement stratiform orebodies (mantos) at lower levels. Based on textural relationships, three major mineralizing stages can be recognized: stage I with cassiterite, sulphides, stannite, tourmaline, and quartz; stage II with cassiterite, sulphides, sulphosalts, quartz, and calcite; and stage III with calcite as the main phase. The study of fluid inclusions has shown that there are two main fluid types: CO₂ and NaCl-H₂O. Homogenization temperatures are 270 to 365°C, 210 to 240°C, and 140 to 190°C for stages I, II, and III, respectively. Salinities range from 1 to 7 wt.% NaCl equiv. in the early ore stage and 3 to 10 wt.% NaCl equiv. in the late stages. Laser Raman Spectroscopy indicates that the inclusion fluids in stages I and II were of carbono-aqueous composition, with minor amounts of CH₄ and H₂S, whereas those in stage III were aqueous. Helium isotopic analyses of inclusion fluids indicate that the ³He/⁴He ratios in the ore veins are in between 1.2 to 2.9 Ra (Ra = 1.4 × 10⁻⁶, modern atmospheric ratio), and range from 1.6 to 2.5 Ra in the stratiform orebodies. This range of ³He/⁴He ratios is significantly higher than that of crustal fluids (0.01–0.05 Ra). The similar characteristics of fluid inclusions and their He isotopic composition, as well as age constraints, indicate that the ore veins and stratiform orebodies of the Tongkeng-Changpo deposit formed from the same hydrothermal system, likely related to granite intrusions of the Mesozoic Yanshanian tectono-thermal event. In addition, the high R/Ra ratios indicate a mantle contribution in the ore fluids.     

He–Ar Isotope Composition of Pyrite and Wolframite in the Tieshanlong Tungsten Deposit,Jiangxi, China: Implications for Fluid Evolution

The Tieshanlong tungsten‐polymetallic deposit is a large wolframite deposit of quartz vein type located in southern Jiangxi, South China. It is genetically related to a high‐K S‐type granite. Seven pyrite and two wolframite samples, selected for He and Ar isotope analyses, yielded ³He/⁴He values of 0.04–0.98 Ra, ⁴⁰Ar/³⁶Ar ratios of 293.5–368.0, and ³⁸Ar/³⁶Ar ratios of 0.176–0.193. These data indicate that the ore‐forming fluids associated with the deposit did not result from a simple mixing of the crustal‐ and mantle‐derived end‐member fluids, but that primeval meteoric fluids were also involved in the generation of the associated granitic magma by partial melting of crustal metasedimentary rocks. Further investigations show that only minimal He from the mantle was added during generation of the associated granitic magma. It is postulated that boiling and second mixing with “new” meteoric fluids took place during migration of magmatic‐hydrothermal fluids into wall‐rock fractures, resulting in a drastic decrease of their metal transport capacity, which triggered the tungsten‐polymetallic mineralization.