Genesis of the Bangbu Orogenic Gold Deposit,Tibet: Evidence from Fluid Inclusion,Stable Isotopes,and Ar-Ar Geochronology

The Bangbu gold deposit is a large orogenic gold deposit in Tibet formed during the AlpineHimalayan collision. Ore bodies(auriferous quartz veins) are controlled by the E-W-trending Qusong-Cuogu-Zhemulang brittle-ductile shear zone. Quartz veins at the deposit can be divided into three types: pre-metallogenic hook-like quartz veins, metallogenic auriferous quartz veins, and postmetallogenic N-S quartz veins. Four stages of mineralization in the auriferous quartz veins have been identified:(1) Stage S1 quartz+coarse-grained sulfides,(2) Stage S2 gold+fine-grained sulfides,(3) Stage S3 quartz+carbonates, and(4) Stage S4 quartz+ greigite. Fluid inclusions indicate the oreforming fluid was CO_2-N_2-CH_4 rich with homogenization temperatures of 170–261°C, salinities 4.34–7.45 wt% Na Cl equivalent. δ~(18)Ofluid(3.98‰–7.18‰) and low δDV-SMOW(-90‰ to-44‰) for auriferous quartz veins suggest ore-forming fluids were mainly metamorphic in origin, with some addition of organic matter. Quartz vein pyrite has δ~(34)SV-CDT values of 1.2‰–3.6‰(an average of 2.2‰), whereas pyrite from phyllite has δ~(34)SV-CDT 5.7‰–9.9‰(an average of 7.4‰). Quartz vein pyrites yield 206Pb/204 Pb ratios of 18.662–18.764, 207Pb/204 Pb 15.650–15.683, and ~(208)Pb/204 Pb 38.901–39.079. These isotopic data indicate Bangbu ore-forming materials were probably derived from the Langjiexue accretionary wedge. 40Ar/39 Ar ages for sericite from auriferous sulfide-quartz veins yield a plateau age of 49.52 ± 0.52 Ma, an isochron age of 50.3 ± 0.31 Ma, suggesting that auriferous veins were formed during the main collisional period of the Tibet-Himalayan orogen(~65–41 Ma).     

Geology and Geochemistry of the Buerkesidai and Kuoerzhenkuola Gold Deposits in the Sawuershan Region, Xinjiang Uigur Autonomous Region, Northwest China

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

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。     

Fluid origin and structural enhancement during mineralization of the Jinshan orogenic gold deposit, South China

The Jinshan orogenic gold deposit is a world-class deposit hosted by a ductile shear zone caused by a transpressional terrane collision during Neoproterozoic time. Ore bodies at the deposit include laminated quartz veins and disseminated pyrite-bearing mylonite. Most quartz veins in the shear zone, with and without gold mineralization, were boudinaged during progressive shear deformation with three generations of boudinage structures produced at different stages of progressive deformation. Observations of ore-controlling structures at various scales indicate syn-deformational mineralization. Fluid inclusions from pyrite intergrown with auriferous quartz have ³He/⁴He ratios of 0.15–0.24 Ra and ⁴⁰Ar/³⁶Ar ratios 575–3,060. δ¹⁸O_fluid values calculated from quartz are 5.5–8.4‰, and δD values of fluid inclusions contained in quartz range between −61‰ and −75‰. The δ¹³C values of ankerite range from −5.0‰ to −4.2‰, and ankerite δ¹⁸O values from 4.4‰ to 8.0‰. The noble gas and stable isotope data suggest a predominant crustal source of ore fluids with less than 5% mantle component. Data also show that in situ fluids were generated locally by pervasive pressure solution, and that widespread dissolution seams acted as pathways of fluid flow, migration, and precipitation. The in situ fluids and fluids derived from deeper levels of the crust were focused by deformation and deformation structures at various scales through solution-dissolution creep, crack-seal slip, and cyclic fault-valve mechanisms during progressively localized deformation and gold mineralization.     

Magma mixing and gold mineralization in the Maevatanana gold deposit,Madagascar

The Maevatanana gold deposit in Madagascar is hosted by Archean metamorphic rocks in quartz–sulfide veins that are structurally controlled by NNW–SSE trending shear zones. Fluid inclusion data show that the trapping conditions in quartz range from 0.87 to 2.58 kbar at temperatures of 269–362 °C. Laser Raman spectroscopy confirms that these inclusions consist of CO₂, SO₂, and H₂O. The δ³⁴S values of the pyrites range from 1.7‰ to 3.6‰, with an average of 2.25‰, supporting a magmatic origin. Noble gases (He, Ne, Ar, Ke, Xe) are chemically inert, thus will not be involved in chemical reactions during geological processes. Also due to the low concentration of He in the atmosphere and the low solubility of He in aqueous fluids, the atmosphere-derived He is unlikely to significantly affect He abundances and isotopic ratios of crustal fluids, ensures that He production should have the typical crust ³He/⁴He ratios. The ³He/⁴He ratios of fluid inclusions in pyrite from the deposit range from 0.06 to 0.12 Ra, while the ⁴⁰Ar/³⁶Ar ratios range from 6631 to 11441. We infer that the ore-forming fluids could have been exsolved from a granitic magma. The oxygen and hydrogen isotope compositions of the ore-forming fluids (1.5‰ ≤ δ¹⁸O_H2O ≤ 7.8‰; –72‰ ≤ δD ≤ –117‰) indicate they were derived from a granitic magma. Four pyrite samples from the gold deposit yield a precise Re–Os isochron age of 534 ± 13 Ma. Given that the post-collisional granites in northern and central Madagascar were derived by melting of sub-continental lithospheric mantle and formed between 537 and 522 Ma, we can state that the gold metallogenesis was coeval with the crystallization age of these parental magmas. These data could be accounted for the formation of the Maevatanana gold deposit. First, the shear zones hosting the deposit formed around 2.5 Ga, when the Madagascan micro-continental blocks collided with other continental blocks, triggering large-scale tectono-magmatic activity and forming NNW–SSE trending shear zones. The gold mineralization at Maevatanana is coeval with the crystallization age of the Cambrian post-collisional A-type granitoid plutons in northern and central Madagascar, implying that this deposit is associated with extensional collapse of the East African Orogen. This extension in turn induced asthenospheric upwelling, melting of sub-continental lithospheric mantle. These magmas underplated the lower crust, generating voluminous granitic magmas by partial melting of the lower crust. The mixing magma during tectono-thermal reactivation of the East African Orogen produced large volumes of volatiles that extracted gold from the granitic magma and produced Au–S complexes (e.g., Au(HSO₃)²⁻). The shear zones, which were then placed under extensional collapse of the East African Orogen in the Cambrian, formed favorable pathways for the magmatic ore-forming fluids. These fluids then precipitated gold-sulfides that form the Maevatanana gold deposit.     

Origin of the Dachang gold deposit,NW China: constraints from H,O, S,and Pb isotope data

The Dachang gold deposit is located in the Late Triassic Songpan-Ganzi Fold Belt, NE Tibetan Plateau. Gold ore is concentrated as veins along secondary faults and fracture zones in the Bayan Har Group metaturbidites. No exposed felsic plutons are present in the vicinity of the deposit. The auriferous veins contain <15% sulphide minerals, mainly arsenopyrite, pyrite, and stibnite. Gold is commonly enclosed within arsenopyrite and pyrite. Typical alteration around the ore bodies includes silicification, sericitization, and weak carbonatization.

Gold-bearing quartz samples have δ¹⁸O values of 16.9–21.2‰ (V-SMOW) from which δ¹⁸O_H2O values of 6.2–9.6‰ can be calculated from the fluid inclusion temperatures (or 10.0 to 12.7‰ if we used the average arsenopyrite geothermometer temperature of 301°C). The δD values of fluid inclusions in quartz range from –90‰ to –72‰. δ³⁴S values of gold-bearing sulphides mainly range from –5.9‰ to –2.8‰ (V-CDT). Pyrite and arsenopyrite in ores have ²⁰⁶Pb/²⁰⁴Pb ratios of 18.2888 to 18.4702, ²⁰⁷Pb/²⁰⁴Pb ratios of 15.5763 to 15.6712, and ²⁰⁸Pb/²⁰⁴Pb ratios of 38.2298 to 38.8212. These isotopic compositions indicate that the ore-forming fluids were of metamorphic origin, and the S and Pb may have been derived from the host metaturbidites of the Bayan Har Group. The Dachang Au deposit has geological and geochemical features similar to orogenic gold deposits. We propose that the ores formed when the Songpan-Ganzi Fold Belt was intensely deformed by Late Triassic folding and thrusting. Large-scale thrusting resulted in regional allochthons of different scales, followed by secondary faults or fracture zones that controlled the ore bodies.     

The Ore-forming Fluid of the Gold Deposits of Muru Gold Belt in Eastern Shandong, China - a Case Study of Denggezhuang Gold Deposit

Abstract. Denggezhuang gold deposit is an epithermal gold‐quartz vein deposit in northern Muru gold belt, eastern Shandong, China. The deposit occurs in the NNE‐striking faults within the Mesozoic granite. The deposit consists of four major veins with a general NNE‐strike. Based on crosscutting relationships and mineral parageneses, the veins appear to have been formed during the same mineralization epochs, and are further divided into three stages: (1) massive barren quartz veins; (2) quartz‐sulfides veins; (3) late, pure quartz or calcite veinlets. Most gold mineralization is associated with the second stage. The early stage is characterized by quartz, and small amounts of ore minerals (pyrite), the second stage is characterized by large amounts of ore minerals. Fluid inclusions in vein quartz contain C‐H‐O fluids of variable compositions. Three main types of fluid inclusions are recognized at room temperature: type I, two‐phase, aqueous vapor and an aqueous liquid phase (L+V); type II, aqueous‐carbonic inclusions, a CC₂‐liquid with/without vapor and aqueous liquid (LCO₂+VCC₂+Laq.); type III, mono‐phase aqueous liquid (Laq.). Data from fluid inclusion distribution, microthermometry, and gas analysis indicate that fluids associated with Au mineralized quartz veins (stage 2) have moderate salinity ranging from 1.91 to 16.43 wt% NaCl equivalent (modeled salinity around 8–10 wt% NaCl equiv.). These veins formatted at temperatures from 80d? to 280d?C. Fluids associated with barren quartz veins (stage 3) have a low salinity of about 1.91 to 2.57 wt% NaCl equivalent and lower temperature. There is evidence of fluid immiscibility and boiling in ore‐forming stages. Stable isotope analyses of quartz indicate that the veins were deposited by waters with δ^O and δD values ranging from those of magmatic water to typical meteoric water. The gold metallogenesis of Muru gold belt has no relationship with the granite, and formed during the late stage of the crust thinning of North China.     

新疆阿合奇县布隆金矿床成矿流体及成矿作用

新疆阿合奇县布隆石英重晶石脉型金矿床是一个少见的金矿新类型 ,其中流体包裹体类型主要有NaCl H2 O型、CO2 H2 O±CH4型和CO2 H2 O NaCl型。均一温度变化范围大 ,从 1 5 9～ 390℃ ,金主成矿阶段温度集中于 2 0 0～ 340℃ ,流体盐度为 2 .4 2 %～ 1 9.2 9%NaCleq ,但各阶段含石盐子晶多相包裹体的盐度高达 2 9.0 2 %～ 4 6 .2 %NaCleq。成矿流体密度为 0 .731～ 1 .1 32g/cm3 。成矿流体气相成分中以H2 O和CO2 为主 ,含少量N2 ,CH4,C2 H6,H2 S等 ;液相成分以Na+ 、Cl-为主 ,其次是Ca2 + ,K+ ,Mg2 + ,SO2 -4。布隆金矿床石英中流体包裹体的δ1 3 CPDB值为 - 4 .6‰～ - 1 .4‰ ,δ1 8OSMOW 为 1 7.2‰～2 1 .1‰ ,δ1 8O水 值为 6 .7‰～ 1 4 .7‰ ,δD变化于 - 70‰～ - 5 5‰ ,表明成矿流体主要来源于建造水 ,并混合少量岩浆水和大气降水 ,流体中的碳主要来源于海相碳酸盐岩。物理化学条件和流体组成的改变以及流体的不混溶作用在成矿过程中起了重要作用     

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.     

北阿尔金地区大平沟金矿H-O-S-Pb同位素地球化学特征对金矿成因的启示

大平沟金矿床是北阿尔金地区典型金矿床之一,矿化类型以钾长石-石英脉型和蚀变岩型为主,矿体赋存于近东西向韧性剪切带中,围岩为太古宇米兰岩群钾长变粒岩。矿石矿物以黄铁矿为主,另有少量褐铁矿和自然金等。大平沟金矿床含金石英脉中石英的δ¹⁸O_VSMOW值为12.4‰~15.3‰,估算的流体δ¹⁸O_H2O值介于7.4‰~10.3‰之间,石英中流体包裹体的氢同位素为-97‰~-66‰,表明成矿流体以变质流体来源为主;含金石英脉中硫化物的δ³⁴S_VCDT值为6.9‰~8.3‰,主要为壳源硫,与典型造山型金矿的硫值一致;硫化物的²⁰⁶Pb/²⁰⁴Pb值为18.310 1~19.373 9,²⁰⁷Pb/²⁰⁴Pb值为15.587 2~15.654 1,而²⁰⁸Pb/²⁰⁴Pb值为38.119 1~39.143 9,反映硫化物的铅来源具有造山带铅特征。综合分析认为,大平沟金矿床属于造山型金矿,其形成受近东西向次级断裂和韧性剪切带控制,成矿流体以变质流体为主,成矿物质来源于太古宙深变质岩。     

Fluid Inclusion and Stable Isotope Study at the Southeastern Martabe Deposit: Purnama,Barani and Horas Ore Bodies,North Sumatra,Indonesia

The Martabe Au–Ag deposit, North Sumatra Province, Indonesia, is a high sulfidation epithermal deposit, which is hosted by Neogene sandstone, siltstone, volcanic breccia, and andesite to basaltic andesite of Angkola Formation. The deposit consists of six ore bodies that occurred as silicified massive ore (enargite–luzonite–pyrite–tetrahedrite–tellurides), quartz veins (tetrahedrite–galena–sphalerite–chalcopyrite), banded sulfide veins (pyrite–tetrahedrite–sphalerite–galena) and cavity filling. All ore bodies are controlled by N–S and NW–SE trending faults. The Barani and Horas ore bodies are located in the southeast of the Purnama ore body. Fluid inclusion microthermometry, and alunite‐pyrite and barite‐pyrite pairs sulfur isotopic geothermometry show slightly different formation temperatures among the ore bodies. Formation temperature and salinity of fluid inclusions of the Purnama ore body range from 200 to 260 C and from 6 to 8 wt.% NaCl equivalent, respectively. Formation temperature and salinity of fluid inclusions of the Barani ore body range from 200 to 220 °C and from 0 to 2.5 wt.% NaCl equivalent and those of the Horas ore body range from 240 to 275 °C and from 2 to 3 wt.% NaCl equivalent, respectively. The Barani and Horas ore bodies are less silicified and sulfides are less abundant than the Purnama ore body. A relationship between enthalpy and chloride content indicates mixing of hot saline fluids with cooler dilute fluids during the mineralization of each of the ore bodies. The δ¹⁸O values of quartz samples from the southeast ore bodies exhibit a wide range from +4.2 to +12.9‰ with an average value of +7.0‰. The δ¹⁸O values of H₂O estimated from δ¹⁸O values of quartz, barite and calcite confirm the oxygen isotopic shift to near meteoric water trend, which support the incorporation of meteoric water. Salinity of the fluid inclusions decrease from >5 wt.% NaCl equivalent in the Purnama ore body to <3 wt.% NaCl equivalent in the Barani ore body, indicating different fluid systems during mineralization. The δ³⁴S values of sulfide and sulfate in Purnama range from ? 4.2 to +5.5‰ and from +1.2 to +26.7‰, those in the Barani range from ? 4.3 to +26.4‰ and from +3.9 to +18.5‰ and those in the Horas ore body range from ? 11.8 to +3.5‰ and from +1.4 to +25.7‰, respectively. The δ³⁴S of total bulk sulfur in southeastern ore bodies (Σδ³⁴S) was estimated to be approximately +6‰. The estimated sulfur fugacity during formation of the Purnama and Horas ore bodies is relatively high. It was between 10^?4.8 and 10^?10.8 atm at 220 to 260 °C. Tellurium fugacity was between 10^?7.8 and 10^?9.5 atm at 260 °C and between 10^?9 and 10^?10.6 atm at 220 °C in the Purnama ore body. The Barani ore body was formed at lower fS₂, lower than about 10^?14 atm at 200 to 220 °C based on the presence of arsenopyrite and pyrrhotite in the early stage, and between 10^?14 and 10^?12 atm based on the existence of enargite and tennantite in the last stage. © 2016 The Society of Resource Geology     

陕西柞山地区穆家庄铜矿床成矿流体来源的氦氩氢氧同位素示踪

最近,在秦岭柞山地区泥盆系中又发现了穆家庄铜矿,矿体明显受层间破碎带控制,矿石主要产在铁白云石-石英脉中,其后生成矿现象非常明显.文章利用的黄铁矿流体包裹体He-Ar同位素和氢氧同位素,来探讨这类矿床的成矿流体的来源.穆家庄铜矿床矿石矿物黄铁矿流体包裹体的3He/4He比值为0.322～0.889R/Ra,小于1.0R/Ra.3He/4He比值远远低于地幔流体的比值,与地壳流体的比值在相同的数量级上.穆家庄铜矿成矿流体的40Ar/36Ar比值为377～569,平均470,显然偏离大气氩的同位素组成.穆家庄铜矿成矿流体的40Ar/4He比值为0.09～0.23,平均值为0.164.很显然,该矿床的成矿流体的40Ar/4He比值接近地壳.根据以上分析,柞山地区的穆家庄铜矿床的成矿流体是壳源的.氢氧同位素分析表明穆家庄铜矿的氢氧同位素则落入原生岩浆水范围内,表明穆家庄铜矿的成矿流体为岩浆水.综合对比分析后认为,穆家庄铜矿的成矿流体是由壳源岩浆驱动并参与的岩浆流体提供的.     

Geological,fluid inclusion,and O–C–S–Pb–He–Ar isotopic constraints on the genesis of the Honghuagou lode gold deposit,northern North China Craton

The Honghuagou Au deposit is located in the Chifeng-Chaoyang region within the northern margin of the North China Craton. The auriferous quartz veins are mainly hosted in the mafic gneiss and migmatite of the Neoarchean Xiaotazigou Formation along NNW- and NE-striking faults, with pyrite as the predominant ore mineral. The gold mineralization process can be divided into two stages, involving stage I quartz-pyrite and stage II quartz-calcite-polymetallic sulfide. Three types of fluid inclusions (FIs) have been identified in the Honghuagou deposit, namely, carbonic inclusions, aqueous‑carbonic inclusions, and aqueous inclusions. Quartz of stage I contains all types of FIs, whereas only aqueous inclusions are evident in stage II veins. The FIs of stages I and II yield homogenization temperatures of 275–340 °C and 240–290 °C with salinities of 3.4–10.7 wt% and 1.4–9.7 wt% NaCl eqv., respectively. The ore-forming fluids are characterized by medium temperature and low salinity, belonging to the H₂O–NaCl–CO₂ system. The δ¹⁸O_H2O values of the ore fluids are between 2.1‰ and 5.9‰, within the range of enriched mantle-derived fluids in the North China Craton. The carbon isotope compositions of calcite (δ¹³C_PDB = −4.4‰ to −4‰) are also similar to mantle carbon. He-Ar isotope data (³He/⁴He = 0.38–0.44 Ra; ⁴⁰Ar/³⁶Ar = 330–477) of fluid inclusions in pyrite indicate a mixed crustal and mantle source for the ore-forming fluids. Whereas, S-Pb isotope compositions of sulfides reveal that ore metals are principally derived from crustal rocks. On the basis of available geological and geochemical evidence, we suggest that the Honghuagou deposit is an orogenic gold deposit.     

Ore‐Forming Fluids as Sampled by Sulfide‐ and Quartz‐Hosted Fluid Inclusions in the Jinwozi Lode Gold Deposit,Eastern Tianshan Mountains of China

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

The Daduhe gold field at the eastern margin of the Tibetan Plateau: He, Ar, S, O, and H isotopic data and their metallogenic implications

The Daduhe gold field comprises several shear-zone-controlled Tertiary lode gold deposits distributed at the eastern margin of the Tibetan Plateau. The deposits are hosted in a Precambrian granite–greenstone terrane within the Yangtze Craton. The gold mineralization occurs mainly as auriferous quartz veins with minor sulphide minerals. Fluid inclusions in pyrite have ³He/⁴He ratios of 0.16 to 0.86 R_a, whereas their ⁴⁰Ar/³⁶Ar ratios range from 298 to 3288, indicating a mixing of fluids of mantle and crust origins. The δ³⁴S values of pyrite are of 0.7–4.2‰ (n = 12), suggesting a mantle source or leaching from the mafic country rocks. δ¹⁸O values calculated from hydrothermal quartz are between − 1.5‰ and + 6.0‰ and δD values of the fluids in the fluid inclusions in quartz are − 39‰ and − 108‰. These ranges demonstrate a mixing of magmatic/metamorphic and meteoric fluids. The noble gas isotopic data, along with the stable isotopic data suggest that the ore-forming fluids have a dominantly crustal source with a significant mantle component.     

Electron microprobe analyses of ore minerals and H–O,S isotope geochemistry of the Yuerya gold deposit,eastern Hebei,China: Implications for ore genesis and mineralization

The Yuerya gold deposit in eastern Hebei Province, China, is located on the eastern margin of the North China Craton and is hosted by Mesozoic Yanshanian granitoid rocks and adjacent Mesoproterozoic Gaoyuzhuang Formation carbonates. The auriferous quartz veins in this deposit are dominated by pyrite, with subordinate sphalerite, chalcopyrite, and galena in a quartz-dominated gangue that also contains calcite, dolomite, barite, apatite, and fluorite. Gold is present as native gold and electrum, which are generally present as micron-size infillings in microfissures within pyrite and less commonly as tiny inclusions within pyrite, quartz, and tellurobismuthite. The pyrite in this deposit has high Co/Ni ratios and contains elevated concentrations of both of these elements, suggesting that the Yuerya gold deposit has a magmato-hydrothermal origin and that the ore-forming fluids that formed the deposit leached trace elements such as Co, Ni, As, and Au during passage through Archean metamorphic rocks, Mesoproterozoic carbonates, and the Yanshanian Yuerya granitoid. Pyrite in the study area has S/Se ratios and S isotopic compositions that suggest that the sulfur (and by inference the gold) within the deposit was sourced from magmato-hydrothermal fluids that were probably originally derived from Archean metamorphic rocks and Yanshanian granitoids. Tellurobismuthite in the study area is closely intergrown with gold and was the single telluride phase identified during this study. The fineness of gold associated with tellurobismuthite is greater than the fineness of gold associated with pyrite, although the fine particle size of the gold surrounded by tellurobismuthite means that the recovery of this gold is difficult, in turn meaning that the tellurobismuthite has little significance to the economics of the Yuerya gold deposit. Only trace amounts of sulfides are associated with the tellurobismuthite within the Yuerya gold deposit, suggesting that this mineral was deposited under conditions of low fS₂ and/or high fTe₂. In addition, the presence of tellurides within the Yuerya gold deposit reflects a genetic relationship between the deposit and magmatism. Quartz from mineralized veins in the study area has δ¹⁸O values of 11.2‰–12.9‰ and the fluids that formed these veins have δD values of − 78.3‰ to − 72.1‰. The δ³⁴S values of pyrite within the deposit are rather restricted (2.3‰–3.5‰). These data, combined with the trace element geochemistry of sulfides within the deposit, suggest that the formation of the Yuerya gold deposit was closely related to both Archean metamorphic rocks and the Yanshanian Yuerya granitoid.     

广西栗木锡铌钽矿田成矿物质来源的惰性气体同位素示踪

文章利用黄铁矿流体包裹体惰性气体同位素,探讨了广西栗木锡铌钽矿田成矿流体的来源.黄铁矿流体包裹体的3He/4He比值为0.14～0.97 Ra,远远低于地幔流体的比值,接近饱和大气水的比值,并与地壳流体的比值处在相同的数量级上;40 Ar/36 Ar比值为555.98～ 855.11,平均705.55,显然偏离大气氩的同位素组成;40Ar*/4He比值为0.08～0.27,平均值为0.153,接近地壳值;20Ne/22 Ne=9.671～9.748和21Ne/22 Ne=0.0306～ 0.0330,具有饱和大气水的Ne同位素比值特征.结果表明,广西栗木锡铌钽矿田老虎头、牛栏岭和金竹源3个矿床的成矿流体是大气水和地壳流体的混合流体;水溪庙矿床的成矿流体也主要是大气水和地壳流体的混合流体,但可能有少量地幔流体的加入.     

Multiple isotope composition (S, Pb, H, O, He, and Ar) and genetic implications for gold deposits in the Jiapigou gold belt, Northeast China

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

Geology,Pb Isotope Geochemistry and Ore Genesis of the Liziyuan Gold Deposit,West Qinling Orogen,Central China

The Liziyuan gold deposit, situated on the south side of the Shangdan suture zone, West Qinling Orogen, occurs in metamorphic volcanic rocks(greenschist facies) of the early Paleozoic Liziyuan Group and in Indosinian Tianzishan monzogranite. Orebodies in the Liziyuan gold field are controlled by the ductile-brittle shear zone, and by thrusting nappe faults related to the Indosinian orogeny. In detail, this paper analyzed the geological characteristics of the Liziyuan gold field, and the Pb isotopes of the Lziyuan host rocks, granitoids(Tianzishan monzogranite and Jiancaowan syenite porphyry), sulfides, and auriferous quartz veins by multiple-collector inductively coupled plasma mass spectrometry(MC-ICPMS). In addition, previous data on the sulfur, hydrogen, and oxygen isotopes were employed to discuss the possible sources of the ore-forming fluids and materials, and to further understand the tectonic setting of the Liziyuan gold deposit. The sulfides and their host rocks(Lziyuan Group), Tianzishan monzogranite and Jiancaowan syenite porphyry, and auriferous quartz veins have similar Pb isotopic compositions.Zartman's plumbotectonic model diagram shows that most of the data for the deposit fall near the orogenic Pb evolutionary curve or within the area between the orogenic and mantle Pb evolutionary curves. In the△β-△γ diagram, which genetically classifies the lead isotopes, most of the data fall within the range of the subduction-zone lead mixed with upper crust and mantle. This indicates that a complex source of the ore lead formed in the orogenic environment. The δ~(34)S values of the sulfides range from 3.90 to 8.50‰(average6.80‰), with a pronounced mode at 5.00‰-8.00‰. These values are consistent with that of orogenic gold deposits worldwide, indicating that the sulfur sourced mainly from reduced metamorphic fluids. The isotopic hydrogen and oxygen compositions support a predominantly metamorphic origin of the oreforming fluids, with possible mixing of minor magmatic fluids, but the late stage was dominated by meteoric water. The characteristics of the Liziyuan gold deposit formed in the Indosinian orogenic environment of the Qinling Orogen are consistent with those of orogenic gold deposits found worldwide.     

粤北诸广南部铀矿田流体包裹体的氦氩同位素组成及成矿流体来源示踪

粤北诸广南部铀矿田是我国重要的花岗岩型铀矿产地之一,有关诸广南部花岗岩型铀矿田的成因,多年来一直存在较大的争议。本文以诸广南部铀矿田典型铀矿床成矿期萤石、方解石和黄铁矿中流体包裹体为测试对象,研究了成矿流体的He、Ar同位素地球化学。研究表明,萤石流体包裹体的~3He/~4He比值为0. 021～0. 186Ra,~(40) Ar/~(36)比值为298. 4～2515. 7;方解石流体包裹体的3He/4He比值为0. 027～0. 209Ra,~(40) Ar/~(36)比值为295. 9～327. 2;黄铁矿流体包裹体的3He/4He比值为0. 021～1. 543Ra,~(40) Ar/~(36)比值为326. 9～1735. 1; He-Ar同位素系统显示成矿流体的3He/4He比值略高于地壳氦同位素特征值(0. 01～0. 05Ra),但低于幔源氦同位素特征值(6～9Ra),~(40) Ar/~(36)比值接近或高于大气氩的同位素组成(~(40) Ar/~(36)=295. 5),成矿流体为壳-幔混合来源。结合H-O、He-Ar、C和Sr等多元同位素证据表明,成矿流体由两个端元组成:一是含有一定放射性成因Ar的大气降水的地壳流体,二是含幔源He的地幔流体。进一步研究表明,受NNW向断裂控制的棉花坑、书楼丘、长排等铀矿床受地幔流体影响比较大,而受NE向断裂控制的蕉坪、东坑、烟筒岭铀矿床受大气降水影响比较大。