First Reliable Re–Os Ages of Pyrite and Stable Isotope Compositions of Fe(‐Cu) Deposits in the Hami Region,Eastern Tianshan Orogenic Belt,NW China

The Eastern Tianshan Orogenic Belt (ETOB) in NW China is composed of the Dananhu–Tousuquan arc belt, the Kanggurtag belt, the Aqishan–Yamansu belt and the Central Tianshan belt from north to south. These tectonic belts have formed through arc–continent or arc–arc collisions during the Paleozoic. A number of Fe(‐Cu) deposits in the Aqishan–Yamansu belt, including the Heifengshan, Shuangfengshan and Shaquanzi Fe(‐Cu) deposits, are associated with Carboniferous–Early Permian volcanic rocks and are composed of vein‐type magnetite ores. Metallic minerals are dominated by magnetite and pyrite, with minor chalcopyrite. Calcite, chlorite, and epidote are the dominant gangue minerals. Pyrite separates of ores from those three deposits have relatively high and variable Re contents ranging from 3.7 to 184 ppb. All pyrite separates have very low common Os, allowing us calculation of single mineral model ages for each sample. Pyrite separates from the Heifengshan Fe deposit have an ¹⁸⁷Re–¹⁸⁷Os isochron age of 310 ± 23 Ma (MSWD = 0.04) and a weighted mean model age of 302 ± 5 Ma (MSWD = 0.17). Those from the Shuangfengshan Fe deposit have an isochron age of 295 ± 7 Ma (MSWD = 0.28) and a weighted mean model age of 292 ± 5 Ma (MSWD = 0.33). The Shaquanzi Fe‐Cu deposit has pyrite with an isochron age of 295 ± 7 Ma (MSWD = 0.26) and a weighted mean model age of 295 ± 6 Ma (MSWD = 0.23). Pyrite separates from these Fe(‐Cu) deposits have δ³⁴S_CDT ranging from ?0.41‰ to 4.7‰ except for two outliers. Calcite from the Heifengshan Fe deposit and Shaquanzi Fe‐Cu deposit have similar C and O isotope compositions with δ¹³C_PDB and δ¹⁸O_SMOW ranging from ?5.5‰ to ?1.0‰ and from 10‰ to 12.7‰, respectively. These stable isotopic data suggest that S, C, and O are magmatic‐hydrothermal in origin. The association of low‐Ti magnetite and Fe/Cu‐sulfides resembles those of Iron–Oxide–Copper–Gold (IOCG) deposits elsewhere. Our reliable Re–Os ages of pyrite suggest that the Fe(‐Cu) deposits in the Aqishan–Yamansu belt formed at ～296 Ma, probably in a back‐arc extensional environment.     

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).     

Source Diversity of Ore Sulfur from Mesozoic-Cenozoic Mineral Deposits in the Korean Peninsula Region

Abstract: Sulfides from the Daebo Jurassic granitoids and some ore deposits from Korean Peninsula and Sikhote Alin occurring in different basement settings were analyzed for δ³⁴S values. Highly positive values were obtained from Jurassic Mo skarn deposit at Geumseong of the Ogcheon belt (average +13. 0%), Au‐quartz vein deposits at Unsan, North Korea (+6. 7%), and late Paleozoic Sn‐F deposit at Votnesenka (+8. 2%), Khanka massif, Russia. Together with published data of that region, regional variation of δ³⁴S values is shown across Korean Peninsula. Sulfur isotopic data published are compiled on 88 ore deposits, whose mineralization epochs belong to Cretaceous (58 deposits), Jurassic (25 deposits) and Precambrian (4 deposits) in South Korea. Average sulfur isotopic values vary across South Korea as follows: Cretaceous deposits in the Gyeongsang basin, +4. 8% ranging +1.2 ? +12.7‰ (n=28); Jurassic and Cretaceous deposits in the Sobaegsan massif, +3. 5% ranging 0.0 ? +7.8‰ (n=20); those of the Ogcheon belt, +6. 4% ranging ‐0.5 ? +15.4‰(n=19); those of the Gyeonggi massif, +5. 5% ranging +2.1 ? +9.0‰(n = 21). The δ³⁴S values of South Korea tend to be concentrated around +5. 5 permil, exhibiting little, if any, a systematic variation across the geotectonic belts. This tendency is seen also in North Korea and Northeast China within the Cino‐Korean Block, and may be called as Cino‐Korean type. Sulfur of this type is derived mostly from the crystalline basement. Khanka massif of Russia seems to have features of the Cino‐Korean type. In contrast, paired positive/negative belts corresponding to magnetite‐series/ilmenite‐series granitic belts are overwhelming in the Japanese Islands, especially in Southwest Japan. The similar trend is also seen in southern Sikhote Alin and northern Okhotsk Rim, which may be called as Japanese type. Source of the sulfur in this type is likely in the subducting oceanic slab for positive value and accreted sedimentary complex for the negative value, respectively. The Daebo granitoids have an average rock δ³⁴S value of +5. 3 permil, which should have reflected that of the source rocks in the continental crust. The ore sulfur heavier than this value may have been originated in other granitoids having even higher δ³⁴S values, or the ore fluids interacted directly with sulfate sulfur of the host evaporites or carbonate rocks. Rock isotopic values of granitoids and basement rocks need to be examined in future from the above point of view in mind.     

Geology, Fluid Inclusion and Isotopic Study of the Neoproterozoic Suoi Thau Copper Deposit, Northwest Vietnam

The Sin Quyen-Lung Po district is an important Cu metallogenic province in Vietnam, but there are few temporal and genetic constraints on deposits from this belt. Suoi Thau is one of the representative Cu deposits associated with granitic intrusion. The deposit consists of ore bodies in altered granite or along the contact zone between granite and Proterozoic meta-sedimentary rocks. The Cu-bearing intrusion is sub-alkaline I-type granite. It has a zircon U-Pb age of ~776 Ma, and has subduction-related geochemical signatures. Geochemical analysis reveals that the intrusion may be formed by melting of mafic lower crust in a subduction regime. Three stages of alteration and mineralization are identified in the Suoi Thau deposit, i.e., potassic alteration; silicification and Cu mineralization; and phyllic alteration. Two-phase aqueous fluid inclusions in quartz from silicification stage show wide ranges of homogenization temperatures(140–383℃) and salinities(4.18wt%–19.13wt%). The high temperature and high salinity natures of some inclusions are consistent with a magmatic derivation of the fluids, which is also supported by the H-O-S isotopes. Fluids in quartz have δD values of –41.9‰ to –68.8‰. The fluids in isotopic equilibrium with quartz have δ~(18)O values ranging from 7.9‰ to 9.2‰. These values are just plotted in the compositional field of magmatichydrothermal fluids in the δD_(water) versus δ~(18)O_(water) diagram. Sulfide minerals have relatively uniform δ~(34)S values from 1.84‰ to 3.57‰, which is supportive of a magmatic derivation of sulfur. The fluid inclusions with relatively low temperatures and salinities most probably represent variably cooled magmatic-hydrothermal fluids. The magmatic derivation of fluids and the close spatial relationship between Cu ore bodies and intrusion suggest that the Cu mineralization most likely had a genetic association with granite. The Suoi Thau deposit, together with other deposits in the region, may define a Neoproterozoic subduction-related ore-forming belt.     

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

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

U–Pb and Re–Os Geochronology of the Tongcun Molybdenum Deposit and Zhilingtou Gold‐Silver Deposit in Zhejiang Province,Southeast China,and Its Geological Implications

Mesozoic ore deposits in Zhejiang Province, Southeast China, are divided into the northwestern and southeastern Zhejiang metallogenic belts along the Jiangshan–Shaoxing Fault. The metal ore deposits found in these belts are epithermal Au–Ag deposits, hydrothermal‐vein Ag–Pb–Zn deposits, porphyry–skarn Mo (Fe) deposits, and vein‐type Mo deposits. There is a close spatial–temporal relationship between the Mesozoic ore deposits and Mesozoic volcanic–intrusive complexes. Zircon U–Pb dating of the ore‐related intrusive rocks and molybdenite Re–Os dating from two typical deposits (Tongcun Mo deposit and Zhilingtou Au–Ag deposit) in the two metallogenic belts show the early and late Yanshanian ages for mineralization. SIMS U–Pb data of zircons from the Tongcun Mo deposit and Zhilingtou Au–Ag deposit indicate that the host granitoids crystallized at 169.7 ± 9.7 Ma (2σ) and 113.6 ± 1 Ma (2σ), respectively. Re–Os analysis of six molybdenite samples from the Tongcun Mo deposit yields an isochron age of 163.9 ± 1.9 Ma (2σ). Re–Os analyses of five molybdenite samples from the porphyry Mo orebodies of the Zhilingtou Au‐Ag deposit yield an isochron age of 110.1 ± 1.8 Ma (2σ). Our results suggest that the metal mineralization in the Zhejiang Province, southeast China formed during at least two stages, i.e., Middle Jurassic and Early Cretaceous, coeval with the granitic magmatism.     

Geology,Mineralogy, Geochronology,and Sulfur Isotope Constraints on the Genesis of the Luanling Gold Telluride Deposit,Western Henan Province,Central China

The Luanling gold telluride deposit in the Xiong'ershan region is located in the southern margin of the North China Craton. The deposit formed in four stages, that is, an early pyrite‐quartz stage (I), a pyrite‐molybdenite stage (II), a sulfide‐telluride‐gold stage (III), and a late carbonate stage (IV). Six species of telluride in stage (III) are recognized, including hessite, altaite, petzite, unidentified Au‐Ag‐Te mineral, empressite, and unidentified Ag‐Te‐S mineral. Gold occurs mostly as native gold and electrum along the microfractures of sulfides or the contact between sulfide and telluride. The mineralization temperature of stage I and stage III ranges from 296 to 377°C and 241 to 324°C, respectively. Tellurides in stage III precipitate at the log?_S2 from ?14.3 to ?7.3 and log?_Te2 from ?17.4 to ?9.4. The ores were formed in an oxidizing environment. The Re‐Os model ages of molybdenite are 162–164 Ma, which indicate that the main ore formation stage was in the Late Jurassic. The Re contents of five molybdenite samples from the Luanling deposit have a range of 36.32–81.95 ppm, except for one large value of 220 ppm, which indicates that the ore‐forming materials are mainly derived from a crustal‐dominated source. The δ³⁴S values of sulfides range from ?17.6 to ?6.2‰, whereas those of sulfates are from 6.8 to 11.5‰. The δ³⁴S_∑S value of the ore‐forming system is 0.0–3.7‰, indicating that the sulfur of the Luanling deposit derived from a deep igneous source. Mineral association and isotope data of the Luanling deposit, together with its geodynamic setting, imply that this deposit belongs to a part of the metallogenic system of the Nannihu‐Sandaozhuang, Shangfangou porphyry molybdenum deposits, and the Late Jurassic granitic intrusions.     

Ore Geology,Fluid Inclusion,and S‐ and Pb‐Isotopic Constraints on the Genesis of the Chitudian Zn‐Pb Deposit,Southern Margin of the North China Craton

The Chitudian Zn‐Pb ore deposit, Luanchuan, Henan province, was recently discovered in the southern margin of the North China Craton. The Zn‐Pb orebodies are hosted in the Proterozoic Guandaokou and Luanchuan Groups, occurring as veins in interbedding fracture zones mainly in a WNW‐ and partially in a NS‐direction. The Zn‐Pb ores are characterized by banded, massive, and breccia structures, coarse crystal grains, and a simple mineral composition mainly of galena, sphalerite, pyrite, quartz, dolomite, and calcite. In addition to the vein type orebodies, there are Mo‐ and Zn‐bearing skarn orebodies in the northwest of the Chitudian ore field. Four types of primary fluid inclusions in quartz and calcite were recognized in the Chitudian Zn‐Pb ores, including aqueous, aqueous‐CO₂, daughter‐mineral‐bearing aqueous, and daughter‐mineral‐bearing aqueous‐CO₂ inclusions, with aqueous inclusion being most common. The homogenization temperatures of the fluid inclusions from the main mineralization stage are from 290°C to 340°C, and the salinities mainly from 3.7 to 14.8 wt% NaCl equivalent. In addition to CO₂, CH₄ and H₂S were detected in the vapor phase and HS^‐ in the liquid phase of the fluid inclusions by Laser Raman spectroscopy. The δ³⁴S_V‐CDT values of ore sulfides from the Chitudian deposit range from ?0.32‰ to 8.30‰, and show two modal peaks in the histogram, one from 1‰ to 4‰, and the other from 5‰ to 7‰. The former peak is similar to that of porphyry‐type Mo‐W deposits in the area, whereas the latter is relatively close to the sulfur in the strata. The ore sulfur may have been derived from both the magma and the strata. The Pb‐isotopic compositions of the ore minerals from Chitudian, with ²⁰⁶Pb/²⁰⁴Pb from 17.005 to l7.953, ²⁰⁷Pb/²⁰⁴Pb from 15.414 to 15.587, and ²⁰⁸Pb/²⁰⁴Pb from 37.948 to 39.036, are similar to those of Mesozoic porphyries in the Chitudian ore field, suggesting that the ore‐forming metals were mainly derived from the Mesozoic magmatic intrusions. The Chitudian Zn‐Pb deposit is interpreted to be a distal hydrothermal vein‐type deposit, which was genetically related to the proximal, skarn‐type Mo ore deposits in the region.     

Two geodynamic–metallogenic events in the Balkhash (Kazakhstan) and the West Junggar (China): Carboniferous porphyry Cu and Permian greisen W-Mo mineralization

This study focuses on the geochronology and elemental and Nd isotopic geochemistry of the Baogutu Cu deposit and the newly discovered Suyunhe W-Mo deposit in the southern West Junggar ore belt (Xinjiang, China), as well as the geology of the newly discovered Hongyuan Mo deposit in the southern West Junggar ore belt and the Kounrad, Borly, and Aktogai Cu deposits and the East Kounrad, Zhanet, and Akshatau W-Mo deposits in the North Balkhash ore belt (Kazakhstan). The aim is to compare their petrogenesis, tectonic setting, and mineralization and to determine the relationship between the southern West Junggar and North Balkhash ore belts. Based on our newly acquired results, we propose that the Kounrad, Borly, Aktogai, and Baogutu deposits are typical porphyry Cu deposits associated with calc-alkaline magmas and formed in a Carboniferous (327–312 Ma) subduction-related setting. In contrast, the East Kounrad, Zhanet, Akshatau, Suyunhe, and Hongyuan deposits are quartz-vein greisen or greisen W-Mo or Mo deposits associated with alkaline magmas and formed in an early Permian (289–306 Ma) collision-related setting. Therefore, two geodynamic–metallogenic events can be distinguished in the southern West Junggar and North Balkhash ore belts: (1) Carboniferous subduction-related calc-alkaline magma – a porphyry Cu metallogenic event – and (2) early Permian collision-related alkaline magma – a greisen W-Mo metallogenic event. The North Balkhash ore belt is part of the Kazakhstan metallogenic zone, which can be extended eastward to the southern West Junggar in China.     

东天山晚古生代内生金属矿床类型和成矿作用的动力学演化规律

新疆东天山是我国重要的矿产集中区之一,并且具有良好的进一步找矿潜力。本文在对东天山成矿地质背景和古生代大量内生金属矿床系统分析的基础之上,划分出7种内生金属矿床的主要成矿类型,阐明了该区晚古生代地壳经历了拉张、挤压、碰撞、碰撞后弛张、剪切走滑和局部伸展的发展阶段,金、铜等内生金属矿床属于不同地球动力学背景下的产物。     

赞比亚铜带省铜矿成因分析

中非(赞比亚―刚果(金))沉积型铜矿以其拥有高品位的大型超大型铜、钴矿床和众多的世界级铜矿山而闻名于世。铜矿类型可分为沉积型铜矿、热液脉型铜矿、变质热液型铜矿三类。沉积型铜矿床形成后,受到深部含矿岩浆热液的侵入形成脉状铜矿,可能还有斑岩型铜钼矿的成矿作用,叠加富集原有的沉积型铜矿床。硫同位素结果显示,硫源主要为成岩硫化物和海水硫酸盐的混合硫,受到深源岩浆或岩浆热液叠加改造。沉积型铜矿成矿年龄880~735Ma,后期岩浆热液型铜钼矿成矿年龄为514~502Ma。这些发现对进一步认识总结中非铜矿带上的矿床成因及成矿规律具有重要意义。     

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

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

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

The Nage Cu-Pb deposit,a new found ore deposit in the southeast Guizhou province,southwest China,is located on the southwestern margin of the Jiangnan Orogenic Belt.Ore bodies are hosted in slate and phyllite of Neoproterozoic Jialu and Wuye Formations,and are structurally controlled by EW-trending fault.It contains Cu and Pb metals about 0.12 million tonnes with grades of 0.2 wt% to 3.4 wt% Cu and 1.1 wt% to 9.27 wt% Pb.Massive and disseminated Cu-Pb ores from the Nage deposit occur as either veinlets or disseminations in silicified rocks.The ore minerals include chalcopyrite,galena and pyrite,and gangue minerals are quartz,sericite and chlorite.The H-O isotopic compositions of quartz,S-Cu-Pb isotopic compositions of sulfide minerals,Pb isotopic compositions of whole rocks and ores have been analyzed to trace the sources of ore-forming fluids and metals for the Nage Cu-Pb deposit.The δ65CuNBS values of chalcopyrite range from-0.09% to +0.33‰,similar to basic igneous rocks and chalcopyrite from magmatic deposits.δ65CuNBS values of chalcopyrite from the early,middle and final mineralization stages show an increasing trend due to63Cu prior migrated in gas phase when fluids exsolution from magma.δ34SCDT values of sulfide minerals range from 2.7‰ to +2.8‰,similar to mantle-derived sulfur(0±3‰).The positive correlation between δ65CuNBS and δ34SCDT values of chalcopyrite indicates that a common source of copper metal and sulfur from magma.δDH2OSMOW and δ18OH2O-SMOW values of water in fluid inclusions of quartz range from 60.7‰ to 44.4‰ and +7.9‰ to +9.0‰(T=260°C),respectively and fall in the field for magmatic and metamorphic waters,implicating that mixed sources for H2O in hydrothermal fluids.Ores and sulfide minerals have a small range of Pb isotopic compositions(208Pb/204Pb=38.152 to 38.384,207Pb/204Pb=15.656 to 17.708 and 206Pb/204Pb=17.991 to 18.049) that are close to orogenic belt and upper crust Pb evolution curve,and similar to Neoproterozoic host rocks(208Pb/204Pb=38.201 to 38.6373,207Pb/204Pb=15.648 to 15.673 and 206Pb/204Pb=17.820 to 18.258),but higher than diabase(208Pb/204Pb=37.830 to 38.012,207Pb/204Pb=15.620 to 15.635 and206Pb/204Pb=17.808 to 17.902).These results imply that the Pb metal originated mainly from host rocks.The H-O-S-Cu-Pb isotopes tegather with geology,indicating that the ore genesis of the Nage Cu-Pb deposit is post-magmatic hydrothermal type.     

湘东南锡田辉钼矿Re-Os同位素定年及其地质意义

湘东南锡田是近年来新发现的一个具有大型规模的钨锡多金属矿田,该矿田位于湘赣边界,南岭成矿带与钦杭成矿带的交汇部位,扬子地块与华夏地块的拼合带。目前对于矿体与成矿岩体之间的关系以及矿体形成时代的问题尚存争议,钨锡矿化究竟是与印支期还是与燕山期花岗岩有关,矿田中众多矿体是否同期形成,这些问题仍待进一步确定。本文选取了两个矿床,即山田云英岩-石英脉型锡多金属矿床和桐木山破碎带蚀变岩型锡多金属矿床,分别对来自这两个矿床的辉钼矿样品进行了Re-Os同位素定年,获得的ReOs模式年龄分别为(158.9±2.2)Ma(2SD)和(160.2±3.2)Ma(2SD),表明这两个矿床形成于晚侏罗世早期。高精度的云母Ar-Ar和辉钼矿Re-Os年龄数据表明锡田钨锡多金属矿田的垄上、荷树下、山田、桐木山矿床均形成于150~160 Ma,即南岭与花岗岩有关钨锡多金属矿大规模成矿作用的高峰期。上述两个辉钼矿样品的铼含量分别为12.44×10-6和2.367×10-6,指示成矿物质分别为壳-幔混合来源和地壳来源,为准确认识该矿田的成矿物质来源提供了进一步的制约。本文还对南岭地区晚侏罗世与花岗岩有关的钨锡多金属矿中90个辉钼矿的铼含量数据进行了统计,结果表明钨锡多金属矿的成矿物质绝大多数为地壳来源,少数为壳-幔混合来源。     

The Kiloton Class Jiaojia Gold Deposit in Eastern Shandong Province and Its Genesis

The recent deep prospecting results in the Jiaojia area of Eastern Shandong Province indicate that the Jiaojia ore field composed of several individual gold deposits as previously suggested is actually an ultra-large gold deposit. This deposit covers an area of ~40 km2, and shows a structural control by the Jiaojia fault and its secondary faults. Gold orebodies generally occur along the same mineralization-alteration belt, and the main orebodies intersect with each other or exhibit a parallel or overlapping distribution. This deposit's reserves are estimated to be 1, 200t of gold, being the first gold deposit of more than 1000t gold reserves in China. The No. I-1 orebody in the Shaling-deep Sizhuang ore blocks holds gold reserves greater than 350 t, or 29 percent of the total reserves, followed by the No. I orebody in Matang-Jiaojia ore blocks with exceeding 150t gold reserves. This deposit mainly occurs in the footwall of the Jiaojia fault, and presents zoned patterns in mineralization, alteration and structures. The strongly mineralized zones agree with strongly altered and tectonically fractured zones. These orebodies display strataform-like, veinlike or lenticular shapes, and generally show characteristics of pinching out and reappearing, branching and converging, expanding and shrinking. The orebodies commonly occur along positions where the fault strike changes and in gentle locations with dips changing from steep to gentle. The main orebodies are parallel to the main plane of the orecontrolling fault, and tend to be gentle from the surface to the deep. The orebodies mainly plunge to the southwest, with plunge angle of 45°–60°. Orebodies near the main plane of the ore-controlling fault have more gold resource than those away from main fault zone. The slant depth of orebodies is generally larger than the length along its strike direction; orebodies become thick and gold grades become low from the shallow area to the deep area. Ore-forming fluids are H2O-CO2-NaCl±CH4 type with medium-temperature and moderate to low salinity. Sulfur isotopic values(δ34SCDT) for gold ores range between 11.08‰ and 12.58‰, indicating mixed sulfur sources; hydrogen isotopic values(δDVSMOW) range from-83.68‰ to-116.95‰ and oxygen isotopic values(δ18OV-SMOW) range between 12.04‰ and 16.28‰. The hydrogen and oxygen isotopes suggest that ore-forming fluids originated from primary magma, and mixing with a large amount of atmospheric water during the late stage. The Eastern Shandong Province gold deposits are associated with magmatic activities which have mantlecrust-mixed source, and also share some similarities with orgenic and epithermal hydrothermal gold deposits. Because Eastern Shandong Province gold deposits with unique metallogenic features and formation setting which are different from other gold deposit types in the world, we call it the Jiaojiatype gold deposits. The kiloton class Jiaojia gold deposit is related to fluid activities, extension and detachment resulted from thermal upwelling of magmas. The strong magmatic activities in the middle to late stage of early Cretaceous in Eastern Shandong Province lead to active fluids, and provided abundant ore-forming materials for gold depsoits. Moreover, many extensional structures resulting from crustal extension provided favourable space for orebody positioning.     

Ore Genesis of the Lunwei Granite‐Related Scheelite Deposit in the Wuyi Metallogenic Belt,Southeast China: Constraints from Geochronology,Fluid Inclusions,and H–O–S Isotopes

A granite‐related scheelite deposit has been recently discovered in the Wuyi metallogenic belt of southeast China. The veinlet–disseminated scheelite occurs mainly in the inner and outer contact zones of the porphyritic biotite granite, spatially associated with potassic feldspathization and silicification. Re–Os dating of molybdenite intergrowths with scheelite yield a well‐constrained isochron age of 170.4 ± 1.2 Ma, coeval with the LA–MC–ICP–MS concordant zircon age of porphyritic biotite granite (167.6 ± 2.2 Ma), indicating that the Lunwei W deposit was formed in the Middle Jurassic (~170 Ma). We identify three stages of ore formation (from early to late): (I) the quartz–K‐feldspar–scheelite stage; (II) the quartz–polymetallic sulfide stage; and (III) the quartz–carbonate stage. Based on petrographic observations and microthermometric criteria, the fluid inclusions in the scheelite and quartz are determined to be mainly aqueous two‐phase (liquid‐rich and gas‐rich) fluid inclusions, with minor gas‐pure and CO₂‐bearing fluid inclusions. Ore‐forming fluids in the Lunwei W deposit show a successive decrease in temperature and salinity from Stage I to Stage III. The homogenization temperature decreases from an average of 299 °C in Stage I, through 251 °C in Stage II, to 212 °C in Stage III, with a corresponding change in salinity from an average of 5.8 wt.%, through 5.2 wt.%, to 3.4 wt.%. The ore‐forming fluids have intermediate to low temperatures and low salinities, belonging to the H₂O–NaCl ± CO₂ system. The δ¹⁸O_H2O values vary from 1.8‰ to 3.3‰, and the δD_V‐SMOW values vary from –66‰ to –76‰, suggesting that the ore‐forming fluid was primarily of magmatic water mixed with various amounts of meteoric water. Sulfur isotope compositions of sulfides (δ³⁴S ranging from –1.1‰ to +2.4‰) and Re contents in molybdenite (1.45–19.25 µg/g, mean of 8.97 µg/g) indicate that the ore‐forming materials originated mainly in the crust. The primary mechanism for mineral deposition in the Lunwei W deposit was a decrease in temperature and the mixing of magmatic and meteoric water. The Lunwei deposit can be classified as a porphyry‐type scheelite deposit and is a product of widespread tungsten mineralization in South China. We summarize the geological characteristics of typical W deposits (the Xingluokeng, Shangfang, and Lunwei deposits) in the Wuyi metallogenic belt and suggest that porphyry and skarn scheelite deposits should be considered the principal exploration targets in this area.     

Comparison of the Typical Metallogenic Systems in the North Slope of the Tongbai‐East Qinling Mountains and its Geologic Implications

The Tongbai-East Qinling Mountains, an important part of the Central orogenic belt, is one of the most important metallogenic belts in China and contains lots of orogenic-type and VMS-type (Volcanogenic Massive Sulfide type) metallogenic systems. The Dahe and Shuidongling VMS-type Cu-Zn deposits, located in the Erlangping Group in Tongbai and East Qinling Mountains, respectively, show similar geological and geochemical features. The Huoshenmiao Formation in the East Qinling region and the Liushanyan Formation in the Tongbai region are spilite-keratophyre sequences occurring in the western and eastern sides of the Nanyang Basin, respectively, and are interpreted to be equivalent to each other. The orogenic-type Au-Ag deposits can be subdivided into two styles; namely, fault- or structure-controlled (e.g. Yindonggou) and stratabound (e.g. Poshan). The Poshan and Yindongpo orogenic-type Au-Ag deposits, whose ore bodies are strictly hosted in carbonaceous strata in the Tongbai Mountains, show obvious stratabound characteristics. Their ore-fluids are enriched in K+ and SO42? and are regarded as K+-SO42? types. The Pb-isotope ratios of sulfides of the ores are extremely uniform and significantly different from those of the tectonostratigraphic terranes of the Qinling orogens except for the ore-hosting strata of the Waitoushan Formation. The Yindonggou and Xuyaogou orogenic Au-Ag deposits in the East Qinling Mountains, whose ore bodies are hosted in the faults cutting the hosting strata or granite body, show fault-controlled characteristics. Their ore-fluids belong to the Na+-Cl? type. The Pb-isotope ratios of sulfides of ores are similar to those of the northern Qinling orogenic belt. The Waitoushan Formation, dominated by carbonaceous sericite-rich schists and only occurring in Tongbai region, should be detached from the Erlangping Group, which occurs both in the western and eastern sides of the Nanyang Basin. Future ore exploration in the Tongbai-East Qinling Mountains should focus on fault-controlled Au-Ag lodes.     

新疆中亚造山带三叠纪矿床地质特征、时空分布及找矿方向

中亚造山带以晚古生代成矿为特色,但最近十几年来在新疆阿尔泰、东天山等发现越来越多的三叠纪矿床,包括3个超大型矿床。在古生代造山带中为什么三叠纪能够成矿和成大矿,不同类型矿产特征和分布规律是值得关注的重要科学问题。目前确定新疆中亚造山带19个三叠纪矿床主要为花岗伟晶岩型稀有金属矿床、斑岩型钼矿床和矽卡岩型钨矿床。花岗伟晶岩型稀有金属矿床分布于阿尔泰,斑岩型钼矿床、矽卡岩型钨矿床和钨(钼)矿床分布于东天山。19个矿床的成矿年龄变化于193～248 Ma,峰值为215 Ma。不同矿床类型成矿时代略有差别,形成时间相对较早的有矽卡岩型,其次是斑岩型,伟晶岩型形成时间跨度最大,多数形成于晚三叠世,少数延续到早侏罗世。东天山沙东-小白石头一带钨矿和阿尔泰稀有金属矿最具找矿潜力。     

Genesis of the Gold Deposit in the Indus-Yarlung Tsangpo Suture Zone, Southern Tibet: Evidence from Geological and Geochemical Data

The Nianzha gold deposit,located in the central section of the Indus-Yarlung Tsangpo suture(IYS) zone in southern Tibet,is a large gold deposit(Au reserves of 25 tons with average grade of 3.08 g/t) controlled by a E-W striking fault that developed during the main stage of Indo-Asian collision(~65-41 Ma).The main orebody is 1760 m long and 5.15 m thick,and occurs in a fracture zone bordered by Cretaceous diorite in the hanging wall to the north and the Renbu tectonic melange in the footwall to the south.High-grade mineralization occurs in a fracture zone between diorite and ultramafic rock in the Renbu tectonic melange.The wall-rock alteration is characterized by silicification in the fracture zone,serpentinization and the formation of talc and magnesite in the ultramafic unit,and chloritization and the formation of epidote and calcite in diorite.Quartz veins associated with Au mineralization can be divided into three stages.Fluid inclusion data indicate that the deposit formed from H_2O-NaCl-organic gas fluids that homogenize at temperatures of 203℃-347℃ and have salinities of 0.35wt%-17.17wt%NaCl equivalent.The quartz veins yield δ~(18)O_(fluid) values of 0.15‰-10.45‰,low δD_(V-SMOW)values(-173‰ to-96‰),and the δ~(13)C values of-17.6‰ to-4.7‰,indicating the ore-forming fluids were a mix of metamorphic and sedimentary orogenic fluids with the addition of some meteoric and mantle-derived fluids.The pyrite within the diorite has δ~(34)S_(V-CDT) values of-2.9‰-1.9‰(average-1.1‰),~(206)Pb/~(204)Pb values of 18.47-18.64,~(207)Pb/~(204)Pb values of 15.64-15.74,and ~(208)Pb/~(204)Pb values of 38.71-39.27,all of which are indicative of the derivation of S and other ore-forming elements from deep in the mantle.The presence of the Nianzha,Bangbu,and Mayum gold deposits within the IYS zone indicates that this area is highly prospective for large orogenic gold deposits.We identified three types of mineralization within the IYS,namely Bangbu-type accretionary,Mayum-type microcontinent,and Nianzha-type ophiolite-associated orogenic Au deposits.The three types formed at different depths in an accretionary orogenic tectonic setting.The Bangbu type was formed at the deepest level and the Nianzha type at the shallowest.     

湘东地区金矿床矿化年龄的测定及含矿流体来源的示踪——兼论矿床成因类型

文章对江南造山带中段湖南东部地区主要金矿床开展了成矿年龄测定和硫同位素分析。获得该区黄金洞和大洞金矿床矿脉石英流体包裹体Rb-Sr等时线年龄分别为152±13Ma和70±1.3Ma;同时获得黄金洞矿床矿脉硫化物δ34S均值为-6.3‰(主要集中在-4.8‰到-8.6‰之间)、大洞δ34S均值为-9.2‰(主要在-8‰到-10‰之间)、雁林寺δ34S均值为-1.2‰(主要在-2.6‰和6.1‰之间)。结合华南区域大地构造演化特征、江南造山带主要金矿床成矿地质条件,认为440～400Ma、160～110Ma和～70Ma是该区的三个主要金矿化期;含矿流体主要来源于深部,与变质水和/或岩浆水有关,但成矿晚期有大量再循环的大气降水和/或海水加入。江南造山带湖南段金矿床具有与造山作用有关的浅成型金矿的某些成矿特点。