The newly discovered Yangchongli gold deposit is a unique independent gold deposit in the Tongling ore-cluster region controlled by the tectonic alteration firstly discovered in the Lower Yangtze Metallogenic Belt （L...The newly discovered Yangchongli gold deposit is a unique independent gold deposit in the Tongling ore-cluster region controlled by the tectonic alteration firstly discovered in the Lower Yangtze Metallogenic Belt （LYMB）. The host magmatic rocks mainly consist of monzodiorite and K-feldspar granite. The LA-ICP-MS U-Pb zircons dating yielded weighted mean 206pb/23SU ages of 140.7 ± 1.8 Ma and 126.4 ±1.2 Ma for the monzodiorite and K-feldspar granite, respectively. Monzodiorites are enriched in Sr, Ba, Rb, and depleted in Y, Yb with high Sr/Y and La/Yb ratios, similar to the geochemical features of adakite, considered as products of differentiation of mafic magmas originating from lithospheric mantle melt/fluids caused by metasomatism during paleo-Pacific Plate subduction in the Mesozic. In contrast, the compositions of K-feldspar granites are A-type granites, indicating an extensional tectonic background. Gold ores hosted in the fracture zone occurred as quartz vein within cataclastic rock. Sulfur and lead isotopes from pyrites show crust-mantle mixing characteristics. Metal components from strata also took part in the gold mineralization, and resulted from two episodes of magmatism that were probably related to tectonic transition from a compressive to an extensional setting between 140-126 Ma, which led to the Mesozoic large-scale polymetallic mineralization events in eastern China.展开更多
According to an analysis of the geological features in the eastern sector of the Bangong Co-Nujiang River suture zone, the Tethyan evolution can be divided into three stages. (1) The Embryo-Tethyan stage (Pz1): An imm...According to an analysis of the geological features in the eastern sector of the Bangong Co-Nujiang River suture zone, the Tethyan evolution can be divided into three stages. (1) The Embryo-Tethyan stage (Pz1): An immature volcanic arc developed in Taniantaweng (Tanen Taunggyi) Range, indicating the existence of an Embryo-Tethyan ocean. (2) The Palaeo-Tethyan stage (C-T2: During the Carboniferous the northern side of the Taniantaweng Range was the main domain of the Palaeo-Tethyan ocean, in which developed flysch sediments intercalated with bimodal volcanic rocks and oceanic tholeiite, and Pemian-Early Triassic are granites were superimposed on the Taniantaweng magmatic are; on the southern side the Dêngqên-Nujiang zone started secondary extension during the Carboniferous, in which the Nujiang ophiolite developed, and the Palaeo-Tethyan ocean closed before the Middle Triassic. (3) The Neo-Tethyan stage (T3-E): During the Late Triassic the Dêngqên zone developed into a relatively matural ocean basin, in which the Dêngqên ophiolite was formed. By the end of the Triassic intraocean subduction occurred, and the ocean domain was reduced gradually, and collided and closed by the end of the Early Jurassic, forming the Yazong mélange; then the Tethyan ocean was completely closed.展开更多
The Bayinqinggeli deposit in the northern Ordos Basin, northwestern of China, is a recently discovered sandstone-type uranium deposit. The uranium(U) orebodies are generally hosted in the lower member of the Jurassic ...The Bayinqinggeli deposit in the northern Ordos Basin, northwestern of China, is a recently discovered sandstone-type uranium deposit. The uranium(U) orebodies are generally hosted in the lower member of the Jurassic Zhiluo Formation(Fm.), and are primarily tabular or irregular in shape. In the study area, 23 sandstone samples were collected from the Zhiluo Fm. and analyzed for major, trace, and rare earth elements(REEs). The geochemical characteristics of these sandstones are used to evaluate the factors controlling U mineralization. The source rocks of the Zhiluo Fm. sandstones are mainly volcanic and felsic magmatic rocks formed in continental arc and active continentalmarginal arc environments, and they provided the material required for the mineralization. The index of compositional variability ranges from 1.02 to 3.29(average1.38), indicating that the Zhiluo Fm. sandstones are immature and composed of first-cycle sediments. The corrected chemical index of alteration averages 56, suggesting that the source rocks underwent weak chemical weathering. The ore host rocks are loose, providing favorable conditions for epigenetic oxidation and U precipitation and enrichment. Ferrous iron in minerals such as chlorite, biotite, ilmenite, and pyrite might have played a role either in adsorbing or reducing the uranium.展开更多
The northwestern margin of Junggar Basin is the region with the richest oil sand resources in China.For better understanding the enrichment rules and deployment of exploration and development of regional oil sand,it i...The northwestern margin of Junggar Basin is the region with the richest oil sand resources in China.For better understanding the enrichment rules and deployment of exploration and development of regional oil sand,it is of great scientific significance to study the accumulation conditions of oil sand in different strata and mining areas of the Junggar Basin.Through a large number of field investigations,drilling verification and sampling tests,it is found that the oil sand in the region covers an area of 2000 km^(2),with shallow and thick reservoir,and predicted resource of 180 million tons.The oil sand resources are mainly distributed in four geological strata,namely the Middle Triassic Karamay Formation,Early Jurassic Badaowan Formation,Late Jurassic Qigu Formation,and Early Cretaceous Qingshuihe Formation.The reservoir is mainly composed of sandstone with high porosity and permeability,and the reservoir space is mainly intergranular pores with a medium average oil content.The oil sand deposit in the region is a typical destructive oil reservoir.The crude oil in the oil sand layer is degraded and thickened from the deep to the shallow,the content of saturated hydrocarbon decreased,and the content of aromatic hydrocarbon,non-hydrocarbon and asphaltene increased.The oil source comes from the deep Permian hydrocarbon-generating depression.Unconformities,faults and marginal fan delta-braided river depositional systems constitute effective migration and storage systems.Caprocks of the Upper Triassic Baijiantan Formation,Lower Jurassic Sangonghe Formation and Lower Cretaceous Hutubihe Formation were formed by three large scale lake transgressions.The Indosinian,Yanshan and Late Yanshan movements are the main driving forces for the migration of deep oil and gas to the shallow edge to form oil sand deposits.It is considered that the oil sand in the northwestern margin of Junggar Basin is of a slope complex migration type.展开更多
Multiple instances of the Late Cretaceous granodiorites within the Anglonggangri region of the northwestern Lhasa Block were identified,their petrogenesis were explored and mineralization potential were assessed.The z...Multiple instances of the Late Cretaceous granodiorites within the Anglonggangri region of the northwestern Lhasa Block were identified,their petrogenesis were explored and mineralization potential were assessed.The zircon U-Pb dating of the Anglonggangri granodiorites revealed ages of 82.8 and 80.8 Ma.Granodiorite samples have SiO2 contents of 64.36-68.33 wt%,with high Sr/Y(55-95)and A/CNK ratios(0.99-1.06).Zirconε_(Hf)(t)values range from−0.3 to+16.2.Two granodiorite samples have(^(87)Sr/^(86)Sr)i values of 0.7034 and 0.7043 and positiveɛNd(t)values of 3.51 and 3.83.These geochemical properties indicate that they are adakitic rocks formed by partial melting of the juvenile thickened lower crust,slightly contaminated with material from the mantle due to the small-scale delamination of the lower crust.The zircons in the granodiorites have moderate Ce/Nd(2.5-43),logfO2(−20.0 to−9.6),andΔFMQ(−1.28 to+4.00)values;low(Ce/Nd)/Y(0.001-0.049)ratios;and high Dy/Yb(0.17-1.16)ratios,which indicate that these granodiorites exhibit moderate oxygen fugacity and lower magma water content than the Miocene Gangdese porphyry copper deposits associated with high-Sr/Y granites.Their ability to create porphyry-type copper deposits could have been hampered by their low magma water content and moderate oxygen fugacity.展开更多
The Cretaceous andesites were discovered in the Biluocuo area,and provided key records to understand the late Mesozoic geodynamic evolution and crustal basement for the southern Qiangtang block in the central Xizang.I...The Cretaceous andesites were discovered in the Biluocuo area,and provided key records to understand the late Mesozoic geodynamic evolution and crustal basement for the southern Qiangtang block in the central Xizang.In this study,we present a detailed study of zircon U-Pb dating,major and trace elemental composition,and Sr-Nd-Hf isotopes for the Biluocuo trachy-andesites.The trachy-andesites yielded zircon U-Pb ages at ca.97 Ma,and exhibited SiO_(2)contents ranging from 55.92 to 69.04 wt%,low TiO_(2)contents(0.37 to 0.75 wt%)and low Mg~#values(18.6 to 53.7),suggesting that they belong to high-K calc-alkaline series.They showed adakitic signatures,such as high Sr/Y ratios(almost 24 to 55)and low Y(<20 ppm),implying they were generated at great depths(>15 kbar).The samples have initial Sr isotopic ratios of 0.70963 to 0.70964,εNd(t)values of-4.7 to-4.6,and zirconεHf(t)values of-1.2 to+1.3 with two-stage Hf model ages of 0.95 to 1.09 Ga.Elemental and Sr-Nd-Hf isotopic signatures suggest that the trachy-andesites were derived from the partial melting of the thickened lower crust with involvement of metasomatized mantle components.Combined with coeval highMg andesites,we proposed that underplating of mantle induced melting of the lower crust at ca.97 Ma in the southern Qiangtang block,following by lithospheric delamination.Inherited/xenocrystic zircons from the trachy-andesites revealed magmatic activities at 2562 Ma,1850-1804 Ma,1768-1665 Ma,1043-935 Ma,851-736 Ma and 642-540 Ma.There is a Precambrian crustal basement in the southern Qiangtang block,which may have experienced the assembly and break-up of the Columbia,Rodinia,and Gondwana supercontinents.展开更多
Outcrop and drill hole data show that the Jurassic coal measures in the northeastern Ordos Basin are composed mainly of the Yan’an Formation and the lowstand system tract of the Zhiluo Formation,and there is a region...Outcrop and drill hole data show that the Jurassic coal measures in the northeastern Ordos Basin are composed mainly of the Yan’an Formation and the lowstand system tract of the Zhiluo Formation,and there is a regional unconformity between them.The Dongsheng uranium deposit is associated with the Jurassic coal measures.Research data indicate that the Jurassic coal measures in the study area have a certain hydrocarbon-generating capacity,although the metamorphic grade is low(Ro=0.40%–0.58%).In the Dongsheng region alone,the accumulative amount of generated coalbed methane(CBM)is about 2028.29×108–2218.72×108 m3;the residual amount is about 50.92×108 m3,and the lost amount is about 1977×108 m3.Analysis of the burial history of the host rocks and the evolutionary history of the Dongsheng uranium deposit suggests that the Jurassic coal measures generated hydrocarbon mainly from Middle Jurassic to Early Crataceous,which is the main mineralization phase of the Dongsheng uranium deposit.By the Late Cretaceous,a mass of CBM dissipated due to the strong tectonic uplift,and the Dongsheng uranium deposit stepped into the preservation phase.Therefore,the low-mature hydrocarbon-containing fluid in the Jurassic coal measures not only served as a reducing agent for the formation of sandstone-type uranium deposits,but also rendered the second reduction of paleo-interlayer oxidation zone and become the primary reducing agent for ore conservation.Regional strata correlation reveals that the sandstone-type uranium reservoir at the bottom of the Zhiluo Formation is in contact with the underlying industrial coal seams in the Yan’an Formation through incision or in the form of an unconformity surface.In the Dongsheng region with poorly developed fault systems,the unconformity surface and scour surface served as the main migration pathways for low-mature hydrocarbon-containing fluid migrating to the uranium reservoir.展开更多
The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small u...The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small ultramafic bodies intruding Proterozoic metamorphic rocks. Complexes at Shitoukengde contain all kinds of mafic-ultramafic rocks, and olivine websterite and pyroxene peridotite are the most important Ni-Cu-hosted rocks. Zircon U-Pb dating suggests that the Shitoukengde Ni-Cu deposit formed in late Silurian （426-422 Ma）, and their zircons have ~Hf（t） values of-9.4 to 5.9 with the older TDMm ages （0.80-1.42 Ga）. Mafic-ultramafic rocks from the No. I complex show the similar rare earth and trace element patterns, which are enriched in light rare earth elements and large ion iithophile elements （e.g., K, Rb, Th） and depleted in heavy rare earth elements and high field strength elements （e.g., Ta, Nb, Zr, Ti）. Sulfides from the deposit have the slightly higher ~34S values of 1.9-4.3%o than the mantle （0 ~ 2%o）. The major and trace element characteristics, and Sr-Nd-Pb and Hf, S isotopes indicate that their parental magmas originated from a metasomatised, asthenospheric mantle source which had previously been modified by subduction-related fluids, and experienced significant crustal contamination both in the magma chamber and during ascent triggering S oversaturation by addition of S and Si, that resulted in the deposition and enrichment of sulfides. Combined with the tectonic evolution, we suggest that the Shitoukengde Ni-Cu deposit formed in the post-collisional, extensional regime related to the subducted oceanic slab break-off after the Wanbaogou oceanic basalt plateau collaged northward to the Qaidam Block in late Silurian.展开更多
The Jinding superlarge lead and zinc deposit has attracted the attention of geologists of the world and its metallogenesis has long been in dispute. This paper takes the Jinding deposit and the Baiyangping Cu-Ag-Co de...The Jinding superlarge lead and zinc deposit has attracted the attention of geologists of the world and its metallogenesis has long been in dispute. This paper takes the Jinding deposit and the Baiyangping Cu-Ag-Co deposit which was recently found at about 30 km north of Jinding as one ore belt, and, based on researches on the helium, argon, and xenon isotopic compositions of primary inclusions in ore-forming solutions of the main stage, the authors have found that the 3He/4He ratio of the ore-forming fluid is 2.7×10?6 (varying from 0.19 to 1.97 Ra), the 4He/40Ar ratio (0.24–3.12) is close to the mantle characteristic ratio, and the xenon isotopic composition and evolution show characters of the mantle xenon. The above results reveal the characteristics of mantle source and crust-mantle fluid mixing (mantle helium reaching 32%) and the metallogenic contributions of the deep processes in the Jinding-Baiyangping ore belt.展开更多
Ore deposits (occurrences) of Au, As, Sb, Hg, etc. distributed in Southwest Guizhou constitute the important portion of the low-temperature metallogenic domain covering a large area in Southwest China, with the Carlin...Ore deposits (occurrences) of Au, As, Sb, Hg, etc. distributed in Southwest Guizhou constitute the important portion of the low-temperature metallogenic domain covering a large area in Southwest China, with the Carlin-type Au and Sb deposits being the most typical ones. In this paper the Au and Sb ore deposits are taken as the objects of study. Through the petrographic analysis, microthermomitric measurement and Raman spectrophic analysis of fluid inclusions in gangue minerals and research on the S and C isotopic compositions in the gold ore deposits we can reveal the sources of ore-forming materials and ore-forming fluids and the rules of ore fluid evolution. Ore deposits of Au, Sb, etc. are regionally classified as the products of ore fluid evolution, and their ore-forming materials and ore fluids were probably derived mainly from the deep interior of the Earth. Fluid inclusion studies have shown that the temperatures of Au mineralization are within the range of 170-361℃,the salinities are 0.35 wt%-8 wt% NaCl eq.; the temperatures of Sb mineralization are 129.4-214℃ and the salinities are 0.18 wt%- 3.23 wt% NaCl eq.; the ore-forming fluid temperatures and salinities tend to decrease progressively. In the early stage (Au metallogenic stage) the ore-forming fluids contained large amounts of volatile components such as CO2, CH4, N2 and H2S, belonging to the H2O-CO2-NaCl fluid system; in the late stage (Sb metallogenic stage) the ore-forming fluids belong to the Sb-bearing H2O-NaCl system. The primitive ore-forming fluids may have experienced at least two processes of immiscibility: (1) when early ore-bearing hydrothermal solutions passed through rock strata of larger porosity or fault broken zones, CO2, CH4, N2 would escape from them, followed by the release of pressure, resulting in pressure release and boiling of primitive homogenous fluids, thereafter giving rise to their phase separation, thus leading to Au unloading and mineralization; and (2) in the late stage (Sb metallogenic stage ) a large volume of meteoric water was involved in the ore-forming fluids, leading to fluid boiling as a result of their encounter, followed by the drop of fluid temperature. As a result, the dissolubility of Sb decreased so greatly that Sb was enriched and precipitated as ores. Due to differences in physic-chemical conditions between Au and Sb precipitates, Au and Sb were respectively precipitated in different structural positions, thus creating such a phenomenon of Au/Sb paragenesis and differentiation in space.展开更多
The Yamansu belt,an important tectonic component of Eastern Tianshan Mountains,of the Central Asian Orogenic Belt,NW China hosts many Fe-(Cu)deposit.In this study,we present new zircon U-Pb geochronology and geochemic...The Yamansu belt,an important tectonic component of Eastern Tianshan Mountains,of the Central Asian Orogenic Belt,NW China hosts many Fe-(Cu)deposit.In this study,we present new zircon U-Pb geochronology and geochemical data of the volcanic rocks of Shaquanzi Formation and diorite intrusions in the Yamansu belt.The Shaquanzi Formation comprises mainly basalt,andesite/andesitic tuff,rhyolite and sub-volcanic diabase with local diorite intrusions.The volcanic rocks and diorites contain ca.315-305 Ma and ca.298 Ma zircons respectively.These rocks show calc-alkaline affinity with enrichment in large-ion lithophile elements(LILEs),light rare-earth elements(LREEs),and depletion in high field strength elements(HFSEs)in primitive mantle normalized multi-element diagrams,which resemble typical back-arc basin rocks.They show depleted mantle signature with ε_(Nd)(t)ranging from+3.1 to +5.6 for basalt;+2.1 to+4.7 for andesite;-0.2 to+1.5 for rhyolite and the ε_(Hf)(t)ranges from-0.1 to +13.0 for andesites;+5.8 to +10.7 for andesitic tuffs.We suggest that the Shaquanzi Formation basalt might have originated from a depleted,metasomatized lithospheric mantle source mixed with minor(3-5%)subduction-derived materials,whereas the andesite and rhyolite could be fractional crystallization products of the basaltic magma.The Shaquanzi Formation volcanic rocks could have formed in an intracontinental back-arc basin setting,probably via the southward subduction of the Kangguer Ocean beneath the Middle Tianshan Massif.The Yamansu mineralization belt might have undergone a continental arc to back-arc basin transition during the Late Carboniferous and the intra-continental back-arc basin might have closed in the Early Permian,marked by the emplacement of dioritic magma in the Shaquanzi belt.展开更多
This study was conducted following research on metallogenesis in the Zhangjiajie-Xuanhua and East Hebei mantle branch structure zones. The Fuping mantle branch structure zone is one where Au, Cu and Ag poly-metallic o...This study was conducted following research on metallogenesis in the Zhangjiajie-Xuanhua and East Hebei mantle branch structure zones. The Fuping mantle branch structure zone is one where Au, Cu and Ag poly-metallic ore resources are concentrated in North Hebei. However, there has existed a long-standing controversy on the temporal-spatial distribution of ore resources and their ore-forming material sources. In terms of age dating and the comprehensive analysis of S, Pb, O, C and Si isotopes, it is considered that the temporal-spatial distribution of ore resources in this mantle branch structure zone is obviously controlled by the Fuping mantle branch structure. In space there is developed such a metallogenic pattern as to be Ag, Pb and Zn polymetallic ore deposits with gold appearing inside and copper appearing outside. Metallogenesis is dated mainly at Yanshanian, the ore-forming materials were derived predominantly from the deep interior of the Earth, and ore-forming fluids were derived largely from Yanshanian magmatism.展开更多
Acid intrusions are widespread in the Sawur region, Xinjiang. The Ka＇erjiao intrusion is mainly composed of albite granite porphyry, K-feldspar granite porphyry, ivernlte and granite porphyry. Being a transitional pr...Acid intrusions are widespread in the Sawur region, Xinjiang. The Ka＇erjiao intrusion is mainly composed of albite granite porphyry, K-feldspar granite porphyry, ivernlte and granite porphyry. Being a transitional product between magma intrusion and eruption in the Sawur region, the Ka＇erjiao intrusion was formed at the telophase of the late Carboniferous to the begining of early Permian as determined by the SHRIMP U-Pb zircon dating, with an age of 302.6±7.6 Ma （1 σ）. The intrusion consists of alkali-enriched rock, whose REE distribution patterns are of the LREE enrichment type, the δEu value is low and Nd, St, Pb isotopes reflect its mantle source characteristics. The δ^18O value of intrusion is low as a result of isotope exchange with meteoric water. The geochemical characteristics show that it was formed in a post-collisional tectonic setting. Taking combined considerations of current studies of A-type granites and Permian volcanic rocks, we think that in the telophase of the late Carboniferous to the beginning of the early Permian, the Sawur region was within the extension or compressional to extensional period of a post-collisionai stage. The Ka＇erjiao intrusion from mantle sources can confirm the vertical continental crust growth in the late Paleozoic. The Sawur region in west Junggar is consistent with east Junggar in post-collisionai tectonic evolution process.展开更多
The Shuiyindong deposit is one of the largest (more than 100 tonnes of Au) and highest grade (more than 7×10-6-10×10-6), strata-bound Carlintype gold deposits in southwestern Guizhou Province, China. The dep...The Shuiyindong deposit is one of the largest (more than 100 tonnes of Au) and highest grade (more than 7×10-6-10×10-6), strata-bound Carlintype gold deposits in southwestern Guizhou Province, China. The deposit is controlled by both structure and favorable lithology. It is situated near the axis of the striking Huijiabao anticline and is hosted in bioclastic limestone of the Permian Longtan Formation. Gold mineralization occurred under low temperature with Th of 220℃± and is closely associated with decarbonation, silicification, sulfidation and dolomitization. The deposit has a characteristic elemental assemblage of Au-As-Hg-Tl. Studies of geochemistry and isotope compositions indicated that the ore-bearing materials and fluids of the gold deposit mainly originated from a plutonic source, and possess a mixing feature with the strata matter during transportation from mantle to crust. Fluid inclusions in vein quartz from the gold deposit are rich in volatile flux, indicating that metallogenic fluid is an overpres-sured one. The activity and geothermal state of the Earth's crust in the long period of time are favorable for the formation of overpressured fluids in a large area, and extensive structures would drive the fluids into ore-forming sys-tem and make gold deposits formed. The complexity of structural movement in the upper crust of southwestern Guizhou Province resulted in complicated gold mineralization. Through metallogenic prognosis and exploration, the proven reserves of the deposit increased by tens of tonnes of Au and the deposit has become a super-large strata-bound Carlin-type gold deposit.展开更多
The Yinkeng orefield in Yudu County,Jiangxi Province,SE China,is a zone of concentrated Au-Ag-Pb-Zn-Cu-Mn polymetallic ores.Based on summing up basic geology and ore geology of the orefieid,the polymetallic deposits i...The Yinkeng orefield in Yudu County,Jiangxi Province,SE China,is a zone of concentrated Au-Ag-Pb-Zn-Cu-Mn polymetallic ores.Based on summing up basic geology and ore geology of the orefieid,the polymetallic deposits in the orefield have been divided into seven major substyles according to their occurring positions and control factors.The ore-forming fluid inclusion styles in the orefield include those of two-phase fluid,liquid CO2-bearing three-phase and daughter mineral-bearing multi-phase.The homogenization temperatures range from 382° to 122℃,falling into five clusters of 370° to 390°,300° to 360°,230° to 300°,210° to 290° and 120° to 200°,and the clusters of 300° to 360°,230° to 300° and 120° to 200° are three major mineralization stages,with fluid salinity peaks from 4.14% to 7.31%,2.07% to 7.31% and 0.53% to 3.90%,respectively.The ore-forming fluids are mainly type of NaCl-H2O with medium to high density （0.74-1.02 g/cm3）,or CO2-bearing NaCl-H2O with medium to low density （0.18-0.79 g/cm3）.The fluid salinity and density both show a decline tendency with decreasing temperature.According to the measurement and calculation of Hand O-isotopic compositions in the quartz of the quartz-sulfide veins,δDV-SMOW of the ore-forming fluid is from-84‰ to-54‰,and δ18OV-SMOW of that is from 6.75‰ to 9.21‰,indicating a magmatic fluid.The δ34SV-CDT of sulfides in the ores fall into two groups,one is from-4.4‰ to 2.2‰ with average of-1.42‰,and the other from 18.8‰ to 21.6‰ with average of 19.8‰.The S-isotopic data shows one peak at-4.4‰ to 2.2‰ （meaning-1.42‰） suggesting a simple magmatic sulfur source.The ore Pbisotopic ratios are 206pb/204pb from 17.817 to 17.983,207pb/204pb from 15.470 to 15.620 and 208pb/204pb from 38.072 to 38.481,indicating characteristics of mantle-derived lead.The data show that the major ore deposits in the orefield have a magmatic-hydrothermal genesis and that the SHRIMP zircon age of the granodiorite porphyry,closely related to the mineralization,is 151.2±4.2 Ma （MSWD =1.3）,which can represent the formation ages of the ores and intrusion rocks.The study aids understanding of the ore-forming processes of the major metallic ore deposits in the orefield.展开更多
Under the guidance of the theory of mantle-branch structure-associated metallogenesis and on the basis of the geological characteristics, analysis of the ore-forming and ore-controlling structures, the geochemical cha...Under the guidance of the theory of mantle-branch structure-associated metallogenesis and on the basis of the geological characteristics, analysis of the ore-forming and ore-controlling structures, the geochemical characteristics of metallogenesis, the source of ore-forming materials, changes in the physical and chemical conditions of metallogenesis, changes in the vertical width of ore veins, and changes in gold grade of the Shihu gold deposit, the mechanism of its metallogenesis was discussed and the rules of vertical variation of ore veins were summarized in this study. It is pointed out that the orebodies under exploitation at present time should be in the middle and upper portions of gold veins in the Shihu gold mining district. Particularly on the basis of the characteristics of mantle-branch structure-associated metallogenesis, it is indicated that metallogenesis is controlled mainly by such ore-forming conditions as temperature and pressure. Deep-seated ore-forming fluids are characterized mainly by injection and precipitation. So the vein bodies in the adjacent metallogenic structures are of obvious comparability, and there would be great prospects for ore search both at depth and in the periphery of the Shihu gold deposit. Therefore, ore prospecting should be strengthened both at depth and in the peripheries.展开更多
As the main part of the “central mountain system” in the continent of China, the Qinling, Qilian and Kunlun orogenic belts have been comprehensively and deeply studied since the 1970s and rich fruits have been reape...As the main part of the “central mountain system” in the continent of China, the Qinling, Qilian and Kunlun orogenic belts have been comprehensively and deeply studied since the 1970s and rich fruits have been reaped. However, these achievements were mostly confined to an individual orogenic belt and the study of the mutual relationship among the three orogenic belts was obliged to depend on comparative studies. Different views were produced therefrom. The material composition and structural features of the junction region show that there are several epicontinental and intracontinental transform faults developed in different periods. Restricted by these transform faults, the large-scale lateral movements and, as a consequence, complicated magmatism and tectonic deformation took place in the orogenic belts. According to these features, the authors put forward a three-stage junction and evolution model and point out that there is not a single junction zone traversing from west to east but that the three orogenic belts have been joined progressively by the epicontinental and intracontinental transform faults.展开更多
The Jingdezhen ductile shear zone is evolved from the Neoproterozoic Zhangyuan ophiolite melange belt in the eastern Jiangnan Orogen, South China. Comprehensive study of geometry, kinematics, quartz c-axis fabric, tem...The Jingdezhen ductile shear zone is evolved from the Neoproterozoic Zhangyuan ophiolite melange belt in the eastern Jiangnan Orogen, South China. Comprehensive study of geometry, kinematics, quartz c-axis fabric, temperature-pressure conditions and geochronology were conducted in this study. The Jingdezhen shear zone extends -180 km along the NE orientation with two groups of subvertical fo- liation and subhorizontal lineation. One group of foliation strikes NEN orientation whereas another one NEE orientation. Field investigation, microscopic observation and quartz c-axis fabric show that sinistral shearing along NEN-striking foliation occurred earlier than dextral shearing along NEE-striking foliation. Syn-tectonic staurolite porphyroblasts and deformation manner of feldspar imply that sinistral shearing occurred at 530-420 ℃ and 6-2 kbar. Deformation manner and c-axis fabric of quartz and pre-tectonic staurolite porphyroblasts indicate that dextral shearing took place at 420-300 ℃. LA-ICP-MS zircon U-Pb and mica ^40Ar/^39Ar dating indicate that the sinistral shearing occurred during Neoproterozoic oro- geny （830-800 Ma） whereas the dextral shearing at 447＋12 Ma. The sinistral shearing resulted from the Neoproterozoic final assembly between the Yangtze and Cathaysia blocks. The dextral shearing was caused by Early Paleozoic orogen parallel extension and clockwise rotation.展开更多
The area studied had developed into an inactive continental margin on the western edge of the Yangtze plate during the Jinning period in Proterozoic time.The Yangtze plate drifted from the south northwards in Paleozoi...The area studied had developed into an inactive continental margin on the western edge of the Yangtze plate during the Jinning period in Proterozoic time.The Yangtze plate drifted from the south northwards in Paleozoic time and reached about 9oS between Late Cambrian and Early Ordovician .The alkalic olivine basalt magma,which was produced via 2-5% partial melting of a fractionated mantle and was accumulated in a deep-seated magma chamber near the Moho.found its way upward along the reviving boundary faults into the upper crust.Two types of layered intrusions,basic and ultrabasic-basic,crystallized from the magma at different pressures.The high initial oxygen fugacity of the magma provides a favorable condition for the deposition of Fe-Ti oxides in the early stage of magmaevolution,resulting in large-sized early magmatic deposits.Magma crystallization may have been interrupted and repeated as a result of pulsative magma influx,giving rise to rhythmic cycles (including the corresponding V-Ti-magnetite ore beds).The magma was stratified owing to double diffusion at the crystallization front and convection was thus occasioned by the density gradient.This has greatly complicated the sequence as would be expected from normal crystallization.展开更多
The Nadingcuo high-K calc-alkaline rocks mainly composed of trachyte and trachyandesite are the largest outcrop area of volcanic rocks in southern Qiangtang terrane in the Tibetan plateau. However,their exact source a...The Nadingcuo high-K calc-alkaline rocks mainly composed of trachyte and trachyandesite are the largest outcrop area of volcanic rocks in southern Qiangtang terrane in the Tibetan plateau. However,their exact source and peterogenesis are still debated.^（40）Ar-^（39）Ar and LAM-ICPMS zircon U-Pb isotopic dating confirm that these rocks erupted in Eocene.In addition,the Nadingcuo volcanic rocks are characterized by high Sr/Y content ratios,similar with the adakite derived from partial melting of oceanic crust.They can be further classified as high Mg~#（Mg~#=48-57） and low Mg~# （Mg~#=33-42） subtypes.The Nadingcuo adakitic rocks have relatively low（^（87）Sr/^（86）Sr）_i and highε_（Nd）（t）, showing a trend of similarity to the Dongcuo ophiolite present in the Bangong-Nujiang oceanic crust. Simple modeling indicates that the Nadingcuo adakitic rocks are a mix resulting from the basalt of Bangong-Nujiang Ocean with 10%-20%crustal material of Lhasa terrane.On these bases we suggest that the low Mg~# Nadingcuo adakitic rocks are the product of partial melting of remnant oceanic crust with small sediment,and the high Mg~# rocks are the result of reaction between rising melt of remnant oceanic crust with subducted sediment and mantle wedge.Therefore,the origin of Nadingcuo adakitic rocks may be related to intracontinental subduction triggered by collision of India-Asia during Cenozoic.展开更多
基金supported by the DREAM project of MOST China (No.2016YFC0600404)the Natural Science Foundation of China (Grant Nos.41372087, 41673040)the Project of Geological Science and Technology of Anhui Province (2015-K-01)
文摘The newly discovered Yangchongli gold deposit is a unique independent gold deposit in the Tongling ore-cluster region controlled by the tectonic alteration firstly discovered in the Lower Yangtze Metallogenic Belt （LYMB）. The host magmatic rocks mainly consist of monzodiorite and K-feldspar granite. The LA-ICP-MS U-Pb zircons dating yielded weighted mean 206pb/23SU ages of 140.7 ± 1.8 Ma and 126.4 ±1.2 Ma for the monzodiorite and K-feldspar granite, respectively. Monzodiorites are enriched in Sr, Ba, Rb, and depleted in Y, Yb with high Sr/Y and La/Yb ratios, similar to the geochemical features of adakite, considered as products of differentiation of mafic magmas originating from lithospheric mantle melt/fluids caused by metasomatism during paleo-Pacific Plate subduction in the Mesozic. In contrast, the compositions of K-feldspar granites are A-type granites, indicating an extensional tectonic background. Gold ores hosted in the fracture zone occurred as quartz vein within cataclastic rock. Sulfur and lead isotopes from pyrites show crust-mantle mixing characteristics. Metal components from strata also took part in the gold mineralization, and resulted from two episodes of magmatism that were probably related to tectonic transition from a compressive to an extensional setting between 140-126 Ma, which led to the Mesozoic large-scale polymetallic mineralization events in eastern China.
文摘According to an analysis of the geological features in the eastern sector of the Bangong Co-Nujiang River suture zone, the Tethyan evolution can be divided into three stages. (1) The Embryo-Tethyan stage (Pz1): An immature volcanic arc developed in Taniantaweng (Tanen Taunggyi) Range, indicating the existence of an Embryo-Tethyan ocean. (2) The Palaeo-Tethyan stage (C-T2: During the Carboniferous the northern side of the Taniantaweng Range was the main domain of the Palaeo-Tethyan ocean, in which developed flysch sediments intercalated with bimodal volcanic rocks and oceanic tholeiite, and Pemian-Early Triassic are granites were superimposed on the Taniantaweng magmatic are; on the southern side the Dêngqên-Nujiang zone started secondary extension during the Carboniferous, in which the Nujiang ophiolite developed, and the Palaeo-Tethyan ocean closed before the Middle Triassic. (3) The Neo-Tethyan stage (T3-E): During the Late Triassic the Dêngqên zone developed into a relatively matural ocean basin, in which the Dêngqên ophiolite was formed. By the end of the Triassic intraocean subduction occurred, and the ocean domain was reduced gradually, and collided and closed by the end of the Early Jurassic, forming the Yazong mélange; then the Tethyan ocean was completely closed.
基金jointly supported by the CNNC Research and Innovation Project(grant no.Geo-SD04and Geo-LTD-1601)funded by the project“Geology of mineral resources in China”from China Geological Survey(grant nos.DD20160346,DD20190379)。
文摘The Bayinqinggeli deposit in the northern Ordos Basin, northwestern of China, is a recently discovered sandstone-type uranium deposit. The uranium(U) orebodies are generally hosted in the lower member of the Jurassic Zhiluo Formation(Fm.), and are primarily tabular or irregular in shape. In the study area, 23 sandstone samples were collected from the Zhiluo Fm. and analyzed for major, trace, and rare earth elements(REEs). The geochemical characteristics of these sandstones are used to evaluate the factors controlling U mineralization. The source rocks of the Zhiluo Fm. sandstones are mainly volcanic and felsic magmatic rocks formed in continental arc and active continentalmarginal arc environments, and they provided the material required for the mineralization. The index of compositional variability ranges from 1.02 to 3.29(average1.38), indicating that the Zhiluo Fm. sandstones are immature and composed of first-cycle sediments. The corrected chemical index of alteration averages 56, suggesting that the source rocks underwent weak chemical weathering. The ore host rocks are loose, providing favorable conditions for epigenetic oxidation and U precipitation and enrichment. Ferrous iron in minerals such as chlorite, biotite, ilmenite, and pyrite might have played a role either in adsorbing or reducing the uranium.
基金granted by the Xinjiang Geological Exploration Fund。
文摘The northwestern margin of Junggar Basin is the region with the richest oil sand resources in China.For better understanding the enrichment rules and deployment of exploration and development of regional oil sand,it is of great scientific significance to study the accumulation conditions of oil sand in different strata and mining areas of the Junggar Basin.Through a large number of field investigations,drilling verification and sampling tests,it is found that the oil sand in the region covers an area of 2000 km^(2),with shallow and thick reservoir,and predicted resource of 180 million tons.The oil sand resources are mainly distributed in four geological strata,namely the Middle Triassic Karamay Formation,Early Jurassic Badaowan Formation,Late Jurassic Qigu Formation,and Early Cretaceous Qingshuihe Formation.The reservoir is mainly composed of sandstone with high porosity and permeability,and the reservoir space is mainly intergranular pores with a medium average oil content.The oil sand deposit in the region is a typical destructive oil reservoir.The crude oil in the oil sand layer is degraded and thickened from the deep to the shallow,the content of saturated hydrocarbon decreased,and the content of aromatic hydrocarbon,non-hydrocarbon and asphaltene increased.The oil source comes from the deep Permian hydrocarbon-generating depression.Unconformities,faults and marginal fan delta-braided river depositional systems constitute effective migration and storage systems.Caprocks of the Upper Triassic Baijiantan Formation,Lower Jurassic Sangonghe Formation and Lower Cretaceous Hutubihe Formation were formed by three large scale lake transgressions.The Indosinian,Yanshan and Late Yanshan movements are the main driving forces for the migration of deep oil and gas to the shallow edge to form oil sand deposits.It is considered that the oil sand in the northwestern margin of Junggar Basin is of a slope complex migration type.
基金jointly supported by the National Key Research&Development Program of China(2021YFC2900100)the Basic Research Fund of the Chinese Academy of Geological Sciences(KK2306)+1 种基金the Geological Survey Project(DD20230360,DD20243483)the Sichuan Provincial Natural Science Foundation(2023NSFSC0798).
文摘Multiple instances of the Late Cretaceous granodiorites within the Anglonggangri region of the northwestern Lhasa Block were identified,their petrogenesis were explored and mineralization potential were assessed.The zircon U-Pb dating of the Anglonggangri granodiorites revealed ages of 82.8 and 80.8 Ma.Granodiorite samples have SiO2 contents of 64.36-68.33 wt%,with high Sr/Y(55-95)and A/CNK ratios(0.99-1.06).Zirconε_(Hf)(t)values range from−0.3 to+16.2.Two granodiorite samples have(^(87)Sr/^(86)Sr)i values of 0.7034 and 0.7043 and positiveɛNd(t)values of 3.51 and 3.83.These geochemical properties indicate that they are adakitic rocks formed by partial melting of the juvenile thickened lower crust,slightly contaminated with material from the mantle due to the small-scale delamination of the lower crust.The zircons in the granodiorites have moderate Ce/Nd(2.5-43),logfO2(−20.0 to−9.6),andΔFMQ(−1.28 to+4.00)values;low(Ce/Nd)/Y(0.001-0.049)ratios;and high Dy/Yb(0.17-1.16)ratios,which indicate that these granodiorites exhibit moderate oxygen fugacity and lower magma water content than the Miocene Gangdese porphyry copper deposits associated with high-Sr/Y granites.Their ability to create porphyry-type copper deposits could have been hampered by their low magma water content and moderate oxygen fugacity.
基金supported by Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(Grant No.2024ZD1001005)The Central Government Guided Local Scientific and Technological Development Funding Project(Grant No.XZ202401YD0006)+5 种基金Key Research and Development Program(Grant No.XZ202403ZY0040)National Natural Science Foundation of China(Grant No.U24A20597)China Geological Survey(Grant Nos.DD20230024,DD20230315)the Basic Scientific Research Project of Chinese Academy of Geological Sciences(Grant No.JKY202209)Hubei Provincial Natural Science Foundation of China(Grant Nos.2023AFD206,2023AFD230,2024AFD401)the Research Fund Program of Hubei Key Laboratory of Resources and Eco-Environment Geology(Grant No.HBREGKFJJ202302)。
文摘The Cretaceous andesites were discovered in the Biluocuo area,and provided key records to understand the late Mesozoic geodynamic evolution and crustal basement for the southern Qiangtang block in the central Xizang.In this study,we present a detailed study of zircon U-Pb dating,major and trace elemental composition,and Sr-Nd-Hf isotopes for the Biluocuo trachy-andesites.The trachy-andesites yielded zircon U-Pb ages at ca.97 Ma,and exhibited SiO_(2)contents ranging from 55.92 to 69.04 wt%,low TiO_(2)contents(0.37 to 0.75 wt%)and low Mg~#values(18.6 to 53.7),suggesting that they belong to high-K calc-alkaline series.They showed adakitic signatures,such as high Sr/Y ratios(almost 24 to 55)and low Y(<20 ppm),implying they were generated at great depths(>15 kbar).The samples have initial Sr isotopic ratios of 0.70963 to 0.70964,εNd(t)values of-4.7 to-4.6,and zirconεHf(t)values of-1.2 to+1.3 with two-stage Hf model ages of 0.95 to 1.09 Ga.Elemental and Sr-Nd-Hf isotopic signatures suggest that the trachy-andesites were derived from the partial melting of the thickened lower crust with involvement of metasomatized mantle components.Combined with coeval highMg andesites,we proposed that underplating of mantle induced melting of the lower crust at ca.97 Ma in the southern Qiangtang block,following by lithospheric delamination.Inherited/xenocrystic zircons from the trachy-andesites revealed magmatic activities at 2562 Ma,1850-1804 Ma,1768-1665 Ma,1043-935 Ma,851-736 Ma and 642-540 Ma.There is a Precambrian crustal basement in the southern Qiangtang block,which may have experienced the assembly and break-up of the Columbia,Rodinia,and Gondwana supercontinents.
基金sponsored by the National Natural Science Foundation Program of China(Nos.40772072 and 40802023)the Uranium Deposit Geological Program of Bureau of Geology,CNNC,the National Important Basic Research Program of China(No.2003CB214603 and No.2015CB453003)the Dongsheng coal and uranium exploration program of Central Geological exploration Fund(No.2008150013)
文摘Outcrop and drill hole data show that the Jurassic coal measures in the northeastern Ordos Basin are composed mainly of the Yan’an Formation and the lowstand system tract of the Zhiluo Formation,and there is a regional unconformity between them.The Dongsheng uranium deposit is associated with the Jurassic coal measures.Research data indicate that the Jurassic coal measures in the study area have a certain hydrocarbon-generating capacity,although the metamorphic grade is low(Ro=0.40%–0.58%).In the Dongsheng region alone,the accumulative amount of generated coalbed methane(CBM)is about 2028.29×108–2218.72×108 m3;the residual amount is about 50.92×108 m3,and the lost amount is about 1977×108 m3.Analysis of the burial history of the host rocks and the evolutionary history of the Dongsheng uranium deposit suggests that the Jurassic coal measures generated hydrocarbon mainly from Middle Jurassic to Early Crataceous,which is the main mineralization phase of the Dongsheng uranium deposit.By the Late Cretaceous,a mass of CBM dissipated due to the strong tectonic uplift,and the Dongsheng uranium deposit stepped into the preservation phase.Therefore,the low-mature hydrocarbon-containing fluid in the Jurassic coal measures not only served as a reducing agent for the formation of sandstone-type uranium deposits,but also rendered the second reduction of paleo-interlayer oxidation zone and become the primary reducing agent for ore conservation.Regional strata correlation reveals that the sandstone-type uranium reservoir at the bottom of the Zhiluo Formation is in contact with the underlying industrial coal seams in the Yan’an Formation through incision or in the form of an unconformity surface.In the Dongsheng region with poorly developed fault systems,the unconformity surface and scour surface served as the main migration pathways for low-mature hydrocarbon-containing fluid migrating to the uranium reservoir.
基金financially supported by the National Natural Science Foundation of China(No.41272093)China geological survey project(No.12120114080901)
文摘The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small ultramafic bodies intruding Proterozoic metamorphic rocks. Complexes at Shitoukengde contain all kinds of mafic-ultramafic rocks, and olivine websterite and pyroxene peridotite are the most important Ni-Cu-hosted rocks. Zircon U-Pb dating suggests that the Shitoukengde Ni-Cu deposit formed in late Silurian （426-422 Ma）, and their zircons have ~Hf（t） values of-9.4 to 5.9 with the older TDMm ages （0.80-1.42 Ga）. Mafic-ultramafic rocks from the No. I complex show the similar rare earth and trace element patterns, which are enriched in light rare earth elements and large ion iithophile elements （e.g., K, Rb, Th） and depleted in heavy rare earth elements and high field strength elements （e.g., Ta, Nb, Zr, Ti）. Sulfides from the deposit have the slightly higher ~34S values of 1.9-4.3%o than the mantle （0 ~ 2%o）. The major and trace element characteristics, and Sr-Nd-Pb and Hf, S isotopes indicate that their parental magmas originated from a metasomatised, asthenospheric mantle source which had previously been modified by subduction-related fluids, and experienced significant crustal contamination both in the magma chamber and during ascent triggering S oversaturation by addition of S and Si, that resulted in the deposition and enrichment of sulfides. Combined with the tectonic evolution, we suggest that the Shitoukengde Ni-Cu deposit formed in the post-collisional, extensional regime related to the subducted oceanic slab break-off after the Wanbaogou oceanic basalt plateau collaged northward to the Qaidam Block in late Silurian.
基金supported by the Chinese postdoctoral research fund,Major State Basic Research Program of China(G1999143201)special project of geological sciences(9801)of the State Planning Commission
文摘The Jinding superlarge lead and zinc deposit has attracted the attention of geologists of the world and its metallogenesis has long been in dispute. This paper takes the Jinding deposit and the Baiyangping Cu-Ag-Co deposit which was recently found at about 30 km north of Jinding as one ore belt, and, based on researches on the helium, argon, and xenon isotopic compositions of primary inclusions in ore-forming solutions of the main stage, the authors have found that the 3He/4He ratio of the ore-forming fluid is 2.7×10?6 (varying from 0.19 to 1.97 Ra), the 4He/40Ar ratio (0.24–3.12) is close to the mantle characteristic ratio, and the xenon isotopic composition and evolution show characters of the mantle xenon. The above results reveal the characteristics of mantle source and crust-mantle fluid mixing (mantle helium reaching 32%) and the metallogenic contributions of the deep processes in the Jinding-Baiyangping ore belt.
基金financially supported jointly by the State Science and Technology Supporting Program(2006BAB01A13)the Self-research Project funded by the State Key Laboratory of Ore Deposit Geochemistry(Ore Deposit Special Research Project 2008.3-2)Guizhou Provincial Bureau of Geology and Mineral Resource Exploration and Development[Qian Di Kuang Ke(2009)No.11]
文摘Ore deposits (occurrences) of Au, As, Sb, Hg, etc. distributed in Southwest Guizhou constitute the important portion of the low-temperature metallogenic domain covering a large area in Southwest China, with the Carlin-type Au and Sb deposits being the most typical ones. In this paper the Au and Sb ore deposits are taken as the objects of study. Through the petrographic analysis, microthermomitric measurement and Raman spectrophic analysis of fluid inclusions in gangue minerals and research on the S and C isotopic compositions in the gold ore deposits we can reveal the sources of ore-forming materials and ore-forming fluids and the rules of ore fluid evolution. Ore deposits of Au, Sb, etc. are regionally classified as the products of ore fluid evolution, and their ore-forming materials and ore fluids were probably derived mainly from the deep interior of the Earth. Fluid inclusion studies have shown that the temperatures of Au mineralization are within the range of 170-361℃,the salinities are 0.35 wt%-8 wt% NaCl eq.; the temperatures of Sb mineralization are 129.4-214℃ and the salinities are 0.18 wt%- 3.23 wt% NaCl eq.; the ore-forming fluid temperatures and salinities tend to decrease progressively. In the early stage (Au metallogenic stage) the ore-forming fluids contained large amounts of volatile components such as CO2, CH4, N2 and H2S, belonging to the H2O-CO2-NaCl fluid system; in the late stage (Sb metallogenic stage) the ore-forming fluids belong to the Sb-bearing H2O-NaCl system. The primitive ore-forming fluids may have experienced at least two processes of immiscibility: (1) when early ore-bearing hydrothermal solutions passed through rock strata of larger porosity or fault broken zones, CO2, CH4, N2 would escape from them, followed by the release of pressure, resulting in pressure release and boiling of primitive homogenous fluids, thereafter giving rise to their phase separation, thus leading to Au unloading and mineralization; and (2) in the late stage (Sb metallogenic stage ) a large volume of meteoric water was involved in the ore-forming fluids, leading to fluid boiling as a result of their encounter, followed by the drop of fluid temperature. As a result, the dissolubility of Sb decreased so greatly that Sb was enriched and precipitated as ores. Due to differences in physic-chemical conditions between Au and Sb precipitates, Au and Sb were respectively precipitated in different structural positions, thus creating such a phenomenon of Au/Sb paragenesis and differentiation in space.
基金financially supported by the Chinese National Basic Research 973-Program(No.2014CB440802)Project No.IS-2353 of GIGCAS
文摘The Yamansu belt,an important tectonic component of Eastern Tianshan Mountains,of the Central Asian Orogenic Belt,NW China hosts many Fe-(Cu)deposit.In this study,we present new zircon U-Pb geochronology and geochemical data of the volcanic rocks of Shaquanzi Formation and diorite intrusions in the Yamansu belt.The Shaquanzi Formation comprises mainly basalt,andesite/andesitic tuff,rhyolite and sub-volcanic diabase with local diorite intrusions.The volcanic rocks and diorites contain ca.315-305 Ma and ca.298 Ma zircons respectively.These rocks show calc-alkaline affinity with enrichment in large-ion lithophile elements(LILEs),light rare-earth elements(LREEs),and depletion in high field strength elements(HFSEs)in primitive mantle normalized multi-element diagrams,which resemble typical back-arc basin rocks.They show depleted mantle signature with ε_(Nd)(t)ranging from+3.1 to +5.6 for basalt;+2.1 to+4.7 for andesite;-0.2 to+1.5 for rhyolite and the ε_(Hf)(t)ranges from-0.1 to +13.0 for andesites;+5.8 to +10.7 for andesitic tuffs.We suggest that the Shaquanzi Formation basalt might have originated from a depleted,metasomatized lithospheric mantle source mixed with minor(3-5%)subduction-derived materials,whereas the andesite and rhyolite could be fractional crystallization products of the basaltic magma.The Shaquanzi Formation volcanic rocks could have formed in an intracontinental back-arc basin setting,probably via the southward subduction of the Kangguer Ocean beneath the Middle Tianshan Massif.The Yamansu mineralization belt might have undergone a continental arc to back-arc basin transition during the Late Carboniferous and the intra-continental back-arc basin might have closed in the Early Permian,marked by the emplacement of dioritic magma in the Shaquanzi belt.
基金supported by the National Natural Science Foundation of China (Grant No. 40872137)Natural Science Foundation of Hebei Province (GrantNo.D2007000751)
文摘This study was conducted following research on metallogenesis in the Zhangjiajie-Xuanhua and East Hebei mantle branch structure zones. The Fuping mantle branch structure zone is one where Au, Cu and Ag poly-metallic ore resources are concentrated in North Hebei. However, there has existed a long-standing controversy on the temporal-spatial distribution of ore resources and their ore-forming material sources. In terms of age dating and the comprehensive analysis of S, Pb, O, C and Si isotopes, it is considered that the temporal-spatial distribution of ore resources in this mantle branch structure zone is obviously controlled by the Fuping mantle branch structure. In space there is developed such a metallogenic pattern as to be Ag, Pb and Zn polymetallic ore deposits with gold appearing inside and copper appearing outside. Metallogenesis is dated mainly at Yanshanian, the ore-forming materials were derived predominantly from the deep interior of the Earth, and ore-forming fluids were derived largely from Yanshanian magmatism.
基金the National Key Basic Science Research project of China in Xinjiang the Anhui Provincial National Science Foundation for Distinguished Young Scholars （Grant No. 04045063）.
文摘Acid intrusions are widespread in the Sawur region, Xinjiang. The Ka＇erjiao intrusion is mainly composed of albite granite porphyry, K-feldspar granite porphyry, ivernlte and granite porphyry. Being a transitional product between magma intrusion and eruption in the Sawur region, the Ka＇erjiao intrusion was formed at the telophase of the late Carboniferous to the begining of early Permian as determined by the SHRIMP U-Pb zircon dating, with an age of 302.6±7.6 Ma （1 σ）. The intrusion consists of alkali-enriched rock, whose REE distribution patterns are of the LREE enrichment type, the δEu value is low and Nd, St, Pb isotopes reflect its mantle source characteristics. The δ^18O value of intrusion is low as a result of isotope exchange with meteoric water. The geochemical characteristics show that it was formed in a post-collisional tectonic setting. Taking combined considerations of current studies of A-type granites and Permian volcanic rocks, we think that in the telophase of the late Carboniferous to the beginning of the early Permian, the Sawur region was within the extension or compressional to extensional period of a post-collisionai stage. The Ka＇erjiao intrusion from mantle sources can confirm the vertical continental crust growth in the late Paleozoic. The Sawur region in west Junggar is consistent with east Junggar in post-collisionai tectonic evolution process.
基金supported jointly by the State Science and Technology Supporting Program (2006BAB01A13)the self-research project funded by the State Key Laboratory of Ore Deposit Geochemistry (Ore Deposit Special Research Project 2008.3-2)Guizhou Provincial Bureau of Geology and Mineral Resource Exploration and Development [Qian Di Kuang Ke (2009) No. 11]
文摘The Shuiyindong deposit is one of the largest (more than 100 tonnes of Au) and highest grade (more than 7×10-6-10×10-6), strata-bound Carlintype gold deposits in southwestern Guizhou Province, China. The deposit is controlled by both structure and favorable lithology. It is situated near the axis of the striking Huijiabao anticline and is hosted in bioclastic limestone of the Permian Longtan Formation. Gold mineralization occurred under low temperature with Th of 220℃± and is closely associated with decarbonation, silicification, sulfidation and dolomitization. The deposit has a characteristic elemental assemblage of Au-As-Hg-Tl. Studies of geochemistry and isotope compositions indicated that the ore-bearing materials and fluids of the gold deposit mainly originated from a plutonic source, and possess a mixing feature with the strata matter during transportation from mantle to crust. Fluid inclusions in vein quartz from the gold deposit are rich in volatile flux, indicating that metallogenic fluid is an overpres-sured one. The activity and geothermal state of the Earth's crust in the long period of time are favorable for the formation of overpressured fluids in a large area, and extensive structures would drive the fluids into ore-forming sys-tem and make gold deposits formed. The complexity of structural movement in the upper crust of southwestern Guizhou Province resulted in complicated gold mineralization. Through metallogenic prognosis and exploration, the proven reserves of the deposit increased by tens of tonnes of Au and the deposit has become a super-large strata-bound Carlin-type gold deposit.
基金financially supported jointly by the National Key Basic Research Program (Grant 2012CB416704) from the Ministry of Science and Technology, Chinathe Program of High-level Geological Talents (201309) and Youth Geological Talents (201112) from the China Geological Surveyby Geological Survey Program Grant 1212010561603-2 from the China Geological Survey
文摘The Yinkeng orefield in Yudu County,Jiangxi Province,SE China,is a zone of concentrated Au-Ag-Pb-Zn-Cu-Mn polymetallic ores.Based on summing up basic geology and ore geology of the orefieid,the polymetallic deposits in the orefield have been divided into seven major substyles according to their occurring positions and control factors.The ore-forming fluid inclusion styles in the orefield include those of two-phase fluid,liquid CO2-bearing three-phase and daughter mineral-bearing multi-phase.The homogenization temperatures range from 382° to 122℃,falling into five clusters of 370° to 390°,300° to 360°,230° to 300°,210° to 290° and 120° to 200°,and the clusters of 300° to 360°,230° to 300° and 120° to 200° are three major mineralization stages,with fluid salinity peaks from 4.14% to 7.31%,2.07% to 7.31% and 0.53% to 3.90%,respectively.The ore-forming fluids are mainly type of NaCl-H2O with medium to high density （0.74-1.02 g/cm3）,or CO2-bearing NaCl-H2O with medium to low density （0.18-0.79 g/cm3）.The fluid salinity and density both show a decline tendency with decreasing temperature.According to the measurement and calculation of Hand O-isotopic compositions in the quartz of the quartz-sulfide veins,δDV-SMOW of the ore-forming fluid is from-84‰ to-54‰,and δ18OV-SMOW of that is from 6.75‰ to 9.21‰,indicating a magmatic fluid.The δ34SV-CDT of sulfides in the ores fall into two groups,one is from-4.4‰ to 2.2‰ with average of-1.42‰,and the other from 18.8‰ to 21.6‰ with average of 19.8‰.The S-isotopic data shows one peak at-4.4‰ to 2.2‰ （meaning-1.42‰） suggesting a simple magmatic sulfur source.The ore Pbisotopic ratios are 206pb/204pb from 17.817 to 17.983,207pb/204pb from 15.470 to 15.620 and 208pb/204pb from 38.072 to 38.481,indicating characteristics of mantle-derived lead.The data show that the major ore deposits in the orefield have a magmatic-hydrothermal genesis and that the SHRIMP zircon age of the granodiorite porphyry,closely related to the mineralization,is 151.2±4.2 Ma （MSWD =1.3）,which can represent the formation ages of the ores and intrusion rocks.The study aids understanding of the ore-forming processes of the major metallic ore deposits in the orefield.
基金This research project is financially granted jointly by the National Natural Science Foundation of China (Grant No 40872137)the Natural Science Foundation of Hebei Province (Grant Nos D2007000751, D2008000534)
文摘Under the guidance of the theory of mantle-branch structure-associated metallogenesis and on the basis of the geological characteristics, analysis of the ore-forming and ore-controlling structures, the geochemical characteristics of metallogenesis, the source of ore-forming materials, changes in the physical and chemical conditions of metallogenesis, changes in the vertical width of ore veins, and changes in gold grade of the Shihu gold deposit, the mechanism of its metallogenesis was discussed and the rules of vertical variation of ore veins were summarized in this study. It is pointed out that the orebodies under exploitation at present time should be in the middle and upper portions of gold veins in the Shihu gold mining district. Particularly on the basis of the characteristics of mantle-branch structure-associated metallogenesis, it is indicated that metallogenesis is controlled mainly by such ore-forming conditions as temperature and pressure. Deep-seated ore-forming fluids are characterized mainly by injection and precipitation. So the vein bodies in the adjacent metallogenic structures are of obvious comparability, and there would be great prospects for ore search both at depth and in the periphery of the Shihu gold deposit. Therefore, ore prospecting should be strengthened both at depth and in the peripheries.
文摘As the main part of the “central mountain system” in the continent of China, the Qinling, Qilian and Kunlun orogenic belts have been comprehensively and deeply studied since the 1970s and rich fruits have been reaped. However, these achievements were mostly confined to an individual orogenic belt and the study of the mutual relationship among the three orogenic belts was obliged to depend on comparative studies. Different views were produced therefrom. The material composition and structural features of the junction region show that there are several epicontinental and intracontinental transform faults developed in different periods. Restricted by these transform faults, the large-scale lateral movements and, as a consequence, complicated magmatism and tectonic deformation took place in the orogenic belts. According to these features, the authors put forward a three-stage junction and evolution model and point out that there is not a single junction zone traversing from west to east but that the three orogenic belts have been joined progressively by the epicontinental and intracontinental transform faults.
基金supported by the National Natural Science Foundation of China (Nos. 41402174, 41472166)the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan)+1 种基金China Scholarship Council (No. 201406415007)the Natural Sciences and Engineering Research Council of Canada
文摘The Jingdezhen ductile shear zone is evolved from the Neoproterozoic Zhangyuan ophiolite melange belt in the eastern Jiangnan Orogen, South China. Comprehensive study of geometry, kinematics, quartz c-axis fabric, temperature-pressure conditions and geochronology were conducted in this study. The Jingdezhen shear zone extends -180 km along the NE orientation with two groups of subvertical fo- liation and subhorizontal lineation. One group of foliation strikes NEN orientation whereas another one NEE orientation. Field investigation, microscopic observation and quartz c-axis fabric show that sinistral shearing along NEN-striking foliation occurred earlier than dextral shearing along NEE-striking foliation. Syn-tectonic staurolite porphyroblasts and deformation manner of feldspar imply that sinistral shearing occurred at 530-420 ℃ and 6-2 kbar. Deformation manner and c-axis fabric of quartz and pre-tectonic staurolite porphyroblasts indicate that dextral shearing took place at 420-300 ℃. LA-ICP-MS zircon U-Pb and mica ^40Ar/^39Ar dating indicate that the sinistral shearing occurred during Neoproterozoic oro- geny （830-800 Ma） whereas the dextral shearing at 447＋12 Ma. The sinistral shearing resulted from the Neoproterozoic final assembly between the Yangtze and Cathaysia blocks. The dextral shearing was caused by Early Paleozoic orogen parallel extension and clockwise rotation.
文摘The area studied had developed into an inactive continental margin on the western edge of the Yangtze plate during the Jinning period in Proterozoic time.The Yangtze plate drifted from the south northwards in Paleozoic time and reached about 9oS between Late Cambrian and Early Ordovician .The alkalic olivine basalt magma,which was produced via 2-5% partial melting of a fractionated mantle and was accumulated in a deep-seated magma chamber near the Moho.found its way upward along the reviving boundary faults into the upper crust.Two types of layered intrusions,basic and ultrabasic-basic,crystallized from the magma at different pressures.The high initial oxygen fugacity of the magma provides a favorable condition for the deposition of Fe-Ti oxides in the early stage of magmaevolution,resulting in large-sized early magmatic deposits.Magma crystallization may have been interrupted and repeated as a result of pulsative magma influx,giving rise to rhythmic cycles (including the corresponding V-Ti-magnetite ore beds).The magma was stratified owing to double diffusion at the crystallization front and convection was thus occasioned by the density gradient.This has greatly complicated the sequence as would be expected from normal crystallization.
基金supported by the following projects:National Basic Research Program of China (2009CB421004,2009CB421003)Natural Science Foundation of China(41073033,40872055,and 40930316)+1 种基金Chinese Academy of Sciences(KZCX2-YW-Q04)China Geological Survey(1212010818098)
文摘The Nadingcuo high-K calc-alkaline rocks mainly composed of trachyte and trachyandesite are the largest outcrop area of volcanic rocks in southern Qiangtang terrane in the Tibetan plateau. However,their exact source and peterogenesis are still debated.^（40）Ar-^（39）Ar and LAM-ICPMS zircon U-Pb isotopic dating confirm that these rocks erupted in Eocene.In addition,the Nadingcuo volcanic rocks are characterized by high Sr/Y content ratios,similar with the adakite derived from partial melting of oceanic crust.They can be further classified as high Mg~#（Mg~#=48-57） and low Mg~# （Mg~#=33-42） subtypes.The Nadingcuo adakitic rocks have relatively low（^（87）Sr/^（86）Sr）_i and highε_（Nd）（t）, showing a trend of similarity to the Dongcuo ophiolite present in the Bangong-Nujiang oceanic crust. Simple modeling indicates that the Nadingcuo adakitic rocks are a mix resulting from the basalt of Bangong-Nujiang Ocean with 10%-20%crustal material of Lhasa terrane.On these bases we suggest that the low Mg~# Nadingcuo adakitic rocks are the product of partial melting of remnant oceanic crust with small sediment,and the high Mg~# rocks are the result of reaction between rising melt of remnant oceanic crust with subducted sediment and mantle wedge.Therefore,the origin of Nadingcuo adakitic rocks may be related to intracontinental subduction triggered by collision of India-Asia during Cenozoic.
