Genesis of the Nuri Cu-W-Mo Deposit,Tibet,China:Constraints from in situ Trace Elements and Sr Isotopic Analysis of Scheelite

The Nuri deposit is the only Cu-W-Mo polymetallic deposit with large-scale WO3 resources in the eastern section of the Gangdese metallogenic belt,Tibet,China.However,the genetic type of this deposit has been controversial since its discovery.Based on a study of the geological characteristics of the deposit,this study presents mineralization stages,focusing on the oxide stage and the quartz-sulfide stage where scheelite is mainly formed,referred to as Sch-A and Sch-B,respectively.Through LA-ICP-MS trace element and Sr isotope analyses,the origin,evolutionary process of the oreforming fluid and genesis of the ore deposit are investigated.Scanning Electron Microscope-Cathodoluminescence(SEMCL)observations reveal that Sch-A consists of three generations,with dark gray homogenous Sch-A1 being replaced by relatively lighter and homogeneous Sch-A2 and Sch-A3,with Sch-A2 displaying a gray CL image color with vague and uneven growth bands and Sch-A3 has a light gray CL image color with hardly any growth band.In contrast,Sch-B exhibits a‘core-rim’structure,with the core part(Sch-B1)being dark gray and displaying a uniform growth band,while the rim part(Sch-B2)is light gray and homogeneous.The normalized distribution pattern of rare earth elements in scheelite and Sr isotope data suggest that the early ore-forming fluid in the Nuri deposit originated from granodiorite porphyry and,later on,some country rock material was mixed in,due to strong water-rock interaction.Combining the O-H isotope data further indicates that the ore-forming fluid in the Nuri deposit originated from magmatic-hydrothermal sources,with contributions from metamorphic water caused by water-rock interaction during the mineralization process,as well as later meteoric water.The intense water-rock interaction likely played a crucial role in the precipitation of scheelite,leading to varying Eu anomalies in different generations of scheelite from the oxide stage to the quartz-sulfide stage,while also causing a gradual decrease in oxygen fugacity(fO2)and a slow rise in pH value.Additionally,the high Mo and low Sr contents in the scheelite are consistent with typical characteristics of magmatic-hydrothermal scheelite.Therefore,considering the geological features of the deposit,the geochemical characteristics of scheelite and the O-H isotope data published previously,it can be concluded that the genesis of the Nuri deposit belongs to porphyry-skarn deposit.

Cassiterite U-Pb dating of the Yelonggou pegmatite-type lithium deposit in western Sichuan and its metallogenic age constraints

1.Objective Pegmatite hosts important resource of rare metals,e.g.,lithium(Li)and beryllium(Be).In recent years,increasingly more studies were dedicated to characterize and unravel the formation of pegmatite-type deposits,for which accurate dating of pegmatite formation and mineralization is essential.The Songpan-Ganzi orogenic belt is a major rare metal metallogenic belt in China,hosting many important pegmatite-type Li deposits,including the Lijiagou,Dangba,Jiajika,Yelonggou,Cuola,and Declalongba.Radiometric age data(mica Ar-Ar and zircon/cassiterite U-Pb)from these Li deposits are sparse,ranging from 210 to 152 Ma.However,obtaining reliable zircon U-Pb dates can be a challenge due to the strong decidualization in pegmatites.As a result,the formation and mineralization ages of these rare metal pegmatites remain controversial,which hampers the development of pegmatite-type metallogenic model for the Songpan-Ganzi orogenic belt.

Fluid inclusion and H-O-S-Pb isotope systematics of the Chayong Cu-polymetallic deposit,Sanjiang Metallogenic Belt,Qinghai Province,China

The Chayong Cu-polymetallic deposit is a recently discovered Cu-polymetallic deposit hosted in the Sanjiang Metallogenic Belt within the Tibetan Plateau of China to the northeast of the North Qiangtang terrane.The ore body occurs in siltstone and is controlled by a northwest-trending fault structure.According to the associations,assemblages,and cutting relationships between ore veins,the hydrothermal mineralization period can be divided into three mineralization stages:(1)a molybdenite mineralization stage,(2)a Cu-polymetallic sulfide stage,and(3)a quartzcarbonate stage.Two types of fluid inclusions(FIs),namely,liquid and vapor-rich inclusions,are present in quartz as so ciated with sulfide minerals.Early-stage FIs are both iquid and vapor-rich,homogenized at temperatures ranging from 364.1 to 384.2℃,and have salinities ranging from0.70%to 9.60%NaCl equivalent(eqv).The middle-stage FIs are also both liquid-and vapor-rich,homogenized at temperatures ranging from 272.4 to 355.6℃,and have salinities ranging from 0.53%-17.10%NaCl eqv.The late-stage FIs are liquid,homogenized at temperatures ranging from 209.4to 255.3℃,and have salinities ranging from 0.35%-6.87%NaCl eqv.The samples from the deposit haveδ^(34)S values of-21.8‰to-19.2‰and-5.5‰to-6.0‰,suggesting that sulfur was derived from the host sediments and magmatic fluids,respectively.The metallic minerals within the deposit have^(206)Pb/^(204)Pb,^(207)Pb/^(204)Pb,and^(208)Pb/^(204)Pb values of 18.439-18.458,15.656-15.679,and 38.772-38.863,respectively,suggesting that the metals were derived from the upper crust and orogenic belts.The samples from the deposit haveδ^(18)O_(W)values of 2.99‰-7.99‰andδD_(W) values ranging from-84.4‰to-73.9‰,indicating that the pre-forming fluids were magmatic and mixed with minor amounts of meteoric water.The ore-forming fluid of the Chayong copper polymetallic deposit was a high-temperature,medium-to low-salinity H_(2)O-NaCl-CH_(4)-N_(2)±CO_(2)fluid system.The early high-temperature magmatic fluid,due to boiling,decreased in temperature,and via the mixing of meteoric water,gradually evolved towards the later-stage medium-to low-temperature and low-salinity fluid,causing nolybdenite mineralization and forming copper polymetallic sulfide veins and quartz carbonate veins.

Robust Timing Constraints for Granitic Magmatism and Hydrothermal Mineralization in the Tieshanlong W-Sn Ore Field,Eastern Nanling Range,South China

The Tieshanlong ore field is an important part of the Nanling Range,which is famous worldwide for its W-Sn mineralization.Notably,the mineralization age of the Tieshanlong ore field is not well constrained,and our field investigation reveals that granitic emplacement occurred at different stages.However,previous studies have not distinguished these multiple stages of magmatism.The Tieshanlong granite complex is closely related to the Huangsha quartz vein-type W-Sn deposit and Tongling skarn-type Cu-W-Sn deposit in this field.Through field investigations and isotopic age analyses,this work studies the relationship between multistage magmatic activity and mineralization in the Tieshanlong ore field.LA-ICP-MS zircon U-Pb isotope analyses revealed that the first-and second-staged granites formed at 154.2±0.6 Ma(MSDW=1.4)and 151.2±0.4 Ma(MSDW=1.5),with zirconε_(Hf)(t)values ranging from-13.1 to-10.5 and from-14.7 to-11.1,respectively.These data suggest that the Tieshanlong granite complex was derived from the partial melting of ancient crustal material.LA-ICP-MS U-Pb dating of wolframite and cassiterite reveals that W-Sn mineralization occurred at 160-150 Ma,which agrees well with the U-Pb dating results of the second-staged granite within analytical errors.The magmatic activity in this ore field can be divided into three stages:175-154 Ma,154-150 Ma and 150-145 Ma.The quartz vein-and skarn-type W-Sn mineralization is closely related to second-staged fine-grained twomica granite,and formed earlier than skarn-type Cu-mineralization.This study establishes a metallogenic model for the Tieshanlong ore field,and this model has important practical significance for identifying concealed W-Sn(-Cu)deposits around other granitic complexes in the Nanling Range.

Research on the Application of Electromagnetic Method in the Exploration of Altered Rock-type Gold Deposits in the East Kunlun Metallogenic Belt

Introduction The East Kunlun Orogenic Belt is located in the northeastern part of the Qinghai–Tibet Plateau(Li et al.,2007),stretching from the East Kunlun to the Elashan area in an east–west direction(Guo et al.,2018).It is an important part of the Central Orogenic Belt(Xiong et al.,2023).It is considered one of the important gold mineralization regions in the Tethys tectonic domain(Norbu et al.,2023)and an essential potential base for mineral resources in China.Wulonggou and Gouli gold mines have been discovered successively,earning the reputation of the"Golden Belt of Qinghai Province"(Feng et al.,2004;He et al.,2023).

Geology and mineralization of the Hongqiling large magmatic nickel-copper-cobalt deposit(22×10^(4)t)in Jilin Province,China:A review

The Hongqiling large nickel-copper-cobalt deposit(hereafter referred to as the Hongqiling deposit),a typical mafic-ultramafic copper-nickel deposit in China,boasts proven Ni(Ni)resources of approximately 22×10^(4)t,associated copper resources of 2×10^(4)t,and associated cobalt(Co)resources of 0.5×10^(4)t,with Ni reserves ranking 10th among China's magmatic nickel deposits.Geotectonically,the Hongqiling deposit is situated in the superimposed zone between the Xing'an-Mongolian orogenic belt and the circum-Western Pacific's active continental margin belt.Its ore-bearing plutons occur within the metamorphic rocks of the Ordovician Hulan Group,with the emplacement of plutons and the locations of orebodies governed by the deep-seated Huifahe fault and its secondary NW-trending Fujia-Hejiagou-Beixinglong-Changsheng fault zone.In the deposit,the rock assemblages of ore-bearing plutons predominantly encompass gabbro-pyroxenite-olivine pyroxenite-pyroxene peridotite(pluton No.1)and norite-orthopyroxenite-harzburgite(pluton No.7),with ore-bearing lithofacies consisting primarily of olivine pyroxenite and pyroxenite facies.The Hongqiling deposit hosts stratoid,overhanging lentoid,veined,and pure-sulfide veined orebodies.Its ores principally contain metallic minerals including pyrrhotite,pentlandite,chalcopyrite,violarite,and pyrite.Despite unidentified magma sources of ore-bearing mafic-ultramafic rocks,it is roughly accepted that the magmatic evolution in the Hongqiling deposit primarily involved fractional crystallization and crustal contamination.The ore-forming materials were primarily derived from the upper mantle,mixed with minor crustal materials.The ore-bearing mafic-ultramafic rocks in the deposit,primarily emplaced during the Indosinian(208-239 Ma),were formed in an intense extension setting followed by the collisional orogeny between the North China Plate and the Songnen-Zhangguangcai Range Block during the Middle-Late Triassic.From the perspective of the metallogenic geological setting,surrounding rocks,ore-controlling structures,and rock assemblages,this study identified one favorable condition and seven significant indicators for prospecting for Hongqiling-type nickel deposits and developed a prospecting model of the Hongqiling deposit.These serve as valuable references for exploring similar nickel deposits in the region,as well as the deep parts and margins of the Hongqiling deposit.

Geology and mineralization of the Dongping supergiant alkalic-hosted Au-Te deposit(>100 t Au)in Northern Hebei Province,China:A review

The Dongping deposit is the largest alkalic-hosted gold deposit in China containing>100 t of Au.This paper presents a new understanding for Dongping ore system,based on the previous studies.The mineralization originally occurred at 400-380 Ma,simultaneous with emplacement of the Shuiquangou alkaline complex,and was overprinted by the hydrothermal activity in the Yanshanian.Isotope compositions of ores indicate metals of the deposit are mainly provided by the Shuiquangou complex.Ore-forming fluids are characterized by increasing oxygen fugacity and decreasing sulfur fugacity,while tellurium fugacity increased in the Stage II-2 and decreased in Stage II-3.These systematic changes are closely related to the processes of mineral precipitation and fluid evolution.Sulfide precipitation from Stage Ⅰ to Stage Ⅱ was triggered by fluid boiling,which leads to the precipitation of Pb-Bi-Te,due to decrement of sulfur fugacity.Condensation of gas phase containing high concentration of H_2Te leads to precipitation of Te-Au-Ag minerals and native tellurium.Based on these hypotheses,this paper present a polyphase metallogenic model as follow.During the Devonian,fluids were released from alkaline magmas,which carried ore-forming materials form the surrounding rocks and precipitate the early ores.During the Jurassic-Cretaceous,fluorine-rich fluids exsolved from highly factionated Shangshuiquan granite,which extracted and concentrated Au from the Shuiquangou complex and the Sanggan Group metamorphic rocks,and finally formed the Dongping gold deposit.

内蒙古克什克腾旗小东沟斑岩型钼矿床成岩成矿机制探讨

本文选取内蒙古克什克腾旗的小东沟斑岩型钼矿区作为研究区,它位于西拉沐伦钼矿带的西南部。对小东沟岩体进行了主微量元素、SHRIMP锆石U-Pb定年等地球化学方面的研究;对岩体中的钾长石和含矿矿物辉钼矿进行了普通铅同位素分析。小东沟岩体具有高硅富钾、REE含量低、Zr含量高、无负铕异常、高ε_(Nd)(t)、低Sr_i等特点,指示岩浆起源于加厚新生下地壳的熔融,同时具有高温、快速熔融、快速析离逃离源区的特点;小东沟岩体的SHRIMP锆石U-Pb定年结果为142±2Ma,对应140Ma左右主应力场由南北向转为东西向的构造体制大转折时期,这个时期大兴安岭处于伸展的构造环境下,底侵作用发育,地幔物质可以添加到下地壳熔融形成的岩浆中;对岩体钾长石和辉钼矿进行的普通铅同位素分析显示前者具有从造山带-地幔过渡的特征,后者则显示有地幔特征,说明成岩、成矿物质来自两个不同的源区,下地壳的岩浆和地幔含矿流体发生了混合。通过以上的分析,结合水-岩浆物理反应的实验结果,本文提出小东沟斑岩型钼矿床的成矿模式:大兴安岭地区在早白垩世伸展的构造背景下,地幔含矿流体加入受底侵作用加热的下地壳中使之熔融形成岩浆,随后更多的地幔含矿流体进入岩浆房,促使其迅速析离逃逸出源区,二者一起上升侵位。在岩浆温度较高时,地幔含矿流体和岩浆大致以较稳定的液态不混溶的状态共存;当岩浆和流体侵位到较浅深度时,压力下降,温度降低,晶体增多,流体-岩浆体系变得不稳定,岩浆被流体分割成许多很小的岩浆团。流体中H^+、K^+和各种成矿元素的存在使之必然会和岩浆或冷却后形成的岩石发生蚀变反应,并晶出成矿矿物,形成现在我们看到的具有浸染状矿化现象的小东沟斑岩型钼矿床。

Contribution of components from volume defect in natural pyrite and quartz to solution chemistry of flotation pulp

The volume defects in pure pyrite and quartz from a classical Cu-Pb-Zn-Fe sulfide deposit were investigated.The results indicate that a large number of volume defects exist in natural pyrite and quartz.The volume defects assume a variety of shapes,including long strips,oval shapes and irregular shapes,with sizes ranging from a few microns to dozens of microns.These volume defects are rich in metallogenic elements as a result of the capture of metallogenic and mineralizing fluid during the defect-forming process.The volume defects are fractured during the grinding process,and their chemical components are released into the solution,as confirmed by the abundant presence of various metal and non-metal components in the cleaning water and EDS results.Under the experimental conditions of 10 g pyrite or quartz with grinding fineness of d90=37 μm,which was cleaned in 40 m L of pure deionised water under an inert atmosphere,the total average concentrations of Cu,Pb,Zn,Fe,Ca,Mg and Cl-in the aqueous solution are 32.09×10^-7,16.51×10^-7,19.45×10^-7,516.52×10^-7,129.50×10^-7,35.30×10^-7 and 433.80×10^-7 mol/L,respectively,for pyrite and 19.20×10^-7,8.88×10^-7,8.31×10^-7,82.71×10^-7,16.21×10^-7,4.28×10^-7 and 731.26×10^-7 mol/L,respectively,for quartz.These values are significantly greater than those from the experimental non-oxidative dissolution of the pyrite or quartz,respectively.Therefore,the metallogenic fluid in volume defects of mineral crystal is concluded to represent the dominant contribution to the solution chemistry of sulfide flotation pulp.The present investigation will help to deeply understand the flotation theory of sulfide minerals.

Control of Deep Tectonics on the Superlarge Deposits in China

Seventy-three large-superlarge deposits in China were formed in 4 metallogenic epochs, and located in 6 metallogenic domains. By combing their time-space distribution and the relevant data of crustal thickness, we discuss the control conditions of deep tectonics on superlarge deposits. The various spatial variation of the crustal thickness where deposits locate is closely related to their different tectonic setting. The crustal thickness of the region where deposits are in the Precatnbrian metallogenic epoch is 37.1 km and shows double-peak distribution, which is related to the different tectonic-mineralization processes in the Tarim-North China and Yangtze metallogenic domains. The crustal thickness of the region where deposits are in the Paleoproterozoic metallogenic epoch is 43.4 km and shows normal distribution, which is the result of 'pure' mineralization setting. The crustal thickness of the region where deposits are in the Late Palaeozoic-Early Mesozoic metallogenic epoch is about 41.2 km and shows multi-peak distribution, which can be related with dispersing distribution in the metallogenic domain of these superlarge deposits. The crustal thickness of the region where deposits are in the post-Indosinian metallogenic epoch is 37.3 km, and shows skew distribution, which resulted from different tectonic settings in eastern and western China.

Outline of Uranium Resources Characteristics and Metallogenetic Regularity in China

Uranium,as one of twenty-six kinds of important minerals in China,is strategic resource and energy mineral,which has been thoroughly investigated in the project of National Potential Evaluation of Uranium Resource.During the implementation of this project,the authors summarized the metallogenic regularity of uranium resource in China systematically,through the researches of geological characteristics of uranium resource,uranium deposits type（genetic and prediction type）,temporal and spatial distribution,and metallogenic series.Based on the investigation of present situation and progress in uranium exploration,this paper proposes the uranium deposits in China should be divided into 4 classes,9 types,21 subtypes in genetic,and 50 types in prediction;suggests to divide China into 29 uranium metallogenic belts and 20 uranium prospective area,and constructs 20uranium-polymetallic metallogenic series,through summarizing temporal and spatial distribution characteristics and metallogenic regularity of uranium deposits in China.The above research is beneficial to the comprehensive understanding of regional uranium metallogenic regularity,and will direct the uranium exploration in the future.

The Metallogenetic Regularities of Lithium Deposits in China

Lithium resources support the development of high-technology industries. China has abundant lithium resources which are mainly distributed in Tibet, Qinghai, Sichuan and Jiangxi. Salt lakes in China have significant lithium reserves, but lithium is mainly produced from hard rock lithium deposits because the extraction from salt lakes requires further improvements. The hard rock lithium deposits mainly occur in granitic pegmatite in the Altay region of Xinjiang and the Jiajika deposit in western Sichuan Province; they mainly formed in the Mesozoic and occurred in a relatively stable stage during orogenic processes. On the basis of the information from 151 lithium deposits or spots, 14 lithium metallogenic series were identified, and granitic pegmatite, granite, and sedimentary types were considered to be the main prediction types of lithium resources. Twelve lithium mineralization belts were divided and a series of maps showing the lithium metallogenetic regularity in China were drawn. We conclude that the hard rock and brine type of lithium resources possibly have a similar lithium source related to magmatism. The mctallogenic features of the lithium in China were related with the distinct history of tectonic-magmatic activity in China. This study benefits the assessment of, and prospecting for, lithium resources in China.

Coupling Effects on Gold Mineralization of Deep and Shallow Structures in the Northwestern Jiaodong Peninsula, Eastern China

For understanding the possible deep-seated processes and geodynamic constrains on gold mineralization, comprehensive physicochemical and geochemical studies of gold mineralization have been undertaken within the paleo-lithosphere framework during the metailogenic epoch from the northwestern part of the Jiaodong Peninsula in this paper. A general image of the paleo-crust has been remained although it has been superimposed and reformed by post-metailogenic tectonic movements. The gold ore deposits occur usually in local uplifts and gradient belts featuring a turn from steep to gentle in granite-metamorphic contact zones, relative uplifts of gradient zones of the Curier isothermal interfaces, depressions of the Moho discontinuity and areas where depth contours are cut by isotherms perpendicularly. Gold mineralization and lithogenesis are characterized by high temperature, low pressure and high strength of thermal flux. The depth of mineralization ranges from 0.8 to 4.5 km. The depth of the top interface of the granitic complex in the metallogenic epoch is about 3 km. There is a low-velocity layer （LVL） at the bottom of the upper crust with a depth close to 19.5 km, which may be a detachment belt in the crust. The appearance of the LVL indicates the existence of paleo-hyperthermal fluid or relics of molten magma chambers, which reflects partial melting within the crust during the diagenetic and metallogenic epochs and the superposition effects of strike-slip shearing of the Taulu fault zone. The subsidence of the Moho is probably attributed to the coupling process of the NW-SE continental collision between North China and the Yangtze Block and the strike-slip movement of the Tanlu fault accompanied with underplating of mantle magma in the northwestern part of the Jiaodong Peninsula. The underplating of mantle magma may result in partial melting and make granite magma transfer upwards. This is favorable for the migration of metallogenic materials from deep to shallow to be enriched to form deposits. Coupling interactions between the strike-slip of the Taulu fault, the underplating of mantle magma, partial melting within the crust, and hyperthermal fluid, etc. may be the important factors controlling the gold mineralization and spatial structures in the metailogenic system.

Genesis of sandstone-type uranium deposits along the northern margin of the Ordos Basin,China

Sandstone-type U mineral resources are among the important sources for nuclear energy.The U deposits in the Ordos Basin in China form part of the northern segment of the sandstone-hosted Central Asian Uranium MegaProvince.Two types of mineralizations are recognized in this basin:"phreatic permeable type"and"interlayer permeable type",both exhibiting features equivalent to roll-front subtypes.The"interlayer permeable type"is widely accepted as the dominant mineralization type for sandstone-type uranium deposits within large-scale basins,also designated as the"interlayer oxidation zone type",based on the horizontal color zoning model representing changing redox conditions.Here we synthesize data from several drill holes within the Ordos Basin,which suggest that major Mesozoic tectonic movements controlled the evolution of the sedimentary system in the basin.These tectonic movements contributed to the formation of three angular unconformities and four parallel unconformities as inferred from the stratigraphic relationships.In addition,other features such as vertical color zoning,paleo-channel controlled tabular or lentoid ore bodies(without roll-type)and a group interlayer horizontal zoning of altered minerals are also documented.Sequence stratigraphic analysis indicates that the Ordos Basin generally witnessed four cycles of water level variations during Mesozoic.During the variations,three high water level and three low water level events were recorded.Biological characteristics imply that the Ordos Basin went through multiple arid to humid climatic evolutions during Mesozoic.Combining the newly documented features with some novel concepts on the hydrodynamic mechanism for supergene ore-forming fluids,we propose a metallogenic model which invokes the importance of tectonic movements and water level fluctuations to explain the genesis of uranium deposits along the northern margin of the Ordos Basin.

Origin and Superposition Metallogenic Model of the Sandstone-type Uranium Deposit in the Northeastern Ordos Basin,China

This paper deals with the metallogenic model of the sandstone type uranium deposit in the northeastern Ordos Basin from aspects of uranium source, migration and deposition. A superposition metallogenic model has been established due to complex uranium mineralization processes with superposition of oil-gas reduction and thermal reformation.

Metallogenic mechanism of Pingguo bauxite deposit,western Guangxi,China:Constraints from REE geochemistry and multi-fractal characteristics of major elements in bauxite ore

Major and REE geochemistry and multi-fractal analysis of two types of bauxite(primary bauxite and accumulated bauxite) ores were studied in Pingguo bauxite orefield in western Guangxi,China.The results of geochemical data show that the accumulated bauxite has a feature of high Al_2O_3 whereas relative low Fe_2O_3 and SiO_2 contents compared to the primary bauxite.The similar chondrite-normalized rare earth element(REE) patterns illustrate that they have a cognate relationship.However,the negative Ce anomalies of primary bauxite and positive Ce anomalies of accumulated bauxite indicate that the ore-forming system changed from reducing environment to oxidation environment.The results of multi-fractal spectrum and parameters of Al_2O_3,Fe_2O_3 and SiO_2 between primary bauxite and accumulated bauxite show that the distinct multi-fractal spectrum parameters reflect the different grade distribution between accumulated and primary bauxite ores.Metallogenic process from primary bauxite to accumulated bauxite is accompanied by the loss of diffluent elements(e.g.,Si and S) and enrichment of stable elements(e.g.,Al and Fe) in the surface environment.Among the rest,the migration mechanism of iron during the evolutionary process from primary ore to accumulated ore can be described as combined leaching and chemical weathering action with participation of sulfur.

^40Ar/^39Ar and Rb-Sr Ages of the Tiegelongnan Porphyry Cu-(Au)Deposit in the Bangong Co-Nujiang Metallogenic Belt of Tibet,China:Implication for Generation of Super-Large Deposit

The Tiegelongnan deposit is a newly discovered super-large porphyry-epithermal Cu-（Au） deposit in the western part of the Bangong Co-Nujiang metallogenic belt, Tibet（China）. Field geology and geochronology indicate that the porphyry mineralization was closely related to the Early Cretaceous intermediate-felsic intrusions（ca. 123–120 Ma）. Various epithermal ore and gangue mineral types were discovered in the middle-shallow part of the orebody, indicating the presence of epithermal mineralization at Tiegelongnan. Potassic, propylitic, phyllic and advanced argillic alteration zones were identified. 40Ar/39Ar dating of hydrothermal biotite（potassic zone）, sericite（phyllic zone）, and alunite（advanced argillic zone） in/around the ore-bearing granodiorite porphyry yielded 121.1±0.6 Ma（1σ）, 120.8±0.7 Ma（1σ） and 117.9±1.6 Ma（1σ）, respectively. Five hydrothermal mineralization stages were identified, of which the Stage IV pyrite was Rb-Sr dated to be 117.5±1.8 Ma（2σ）, representing the end of epithermal mineralization. Field geology and geochronology suggest that both the epithermal and porphyry mineralization belong to the same magmatic-hydrothermal system. The Tiegelongnan super-large Cu-（Au） deposit may have undergone a prolonged magmatichydrothermal evolution, with the major mineralization event occurring at ca.120–117Ma.

The Discovery of Natural Native Uranium and Its Significance

This study analyzed the composition and uranium valence of pitchblendes sampled from the hydrothermal Guidong and Zhuguang uranium deposits of the middle Nanling metallogenic belt, Southern China using X-ray photoelectron spectroscopy（XPS）.A revolutionary discovery is that the uranium not only exists in the forms of tetravalent and hexavalent uranium oxides, but also occurs in the form of native uranium.This is the first discovery of the existence of native uranium in nature.It greatly helps to reveal the origin of hydrothermal mineralization of uranium, and also has great significance for studying the thermal energy, formation and evolution of the earth.

Metallogenic Epoch of Nonferrous Metallic and Silver Deposits in the Jiaodong Peninsula, China and its Geological Significance

As China＇s most important gold-producing district, the Jiaodong Peninsula also contains copper, lead-zinc, molybdenum （tungsten）, and other nonferrous metal ore deposits, but the space-time and genetic relationships with gold deposits remain uncertain. To investigate the temporal relationship between these nonferrous metal and gold ore deposits, We collected the samples from a number of nonferrous metallic and silver deposits and metallogenetic rock bodies in the eastern Jiaodong Peninsula for isotopic dating. The results show that the Re-Os isotopic model ages of the Lengjia molybdenum deposit in Rongcheng range from 114.5 ± 1.8 Ma to 112.6 ± 1.5 Ma, with an average age of 113.6 ± 1.6 Ma; the LA-ICP-MS ^206pb/^238U ages of 33 zircons in the sericitization porphyritic monzogranite that hosts the Tongjiazhuang silver deposit in Rongcheng range between 122 Ma and 109 Ma, with a weighted mean age of 116.04 ± 0.95 Ma; the LA-ICP-MS ^206pb/^238U ages of 31 zircons in the copper metallogenic pyroxene monzodiorite that hosts the Kuangbei copper deposit in Rongcheng range from 126 Ma to 106 Ma, with a weighted mean age of 116.6 ± 1.7 Ma; and the LA-ICP-MS ^206pb/^238U ages of 19 zircons in the pyroxene monzodiorite surrounding the Dadengge gold and multimetal deposit in Weihai range from 113 Ma to 110 Ma, with a weighted mean age of 111.7 ± 0.6 Ma. All these results indicate that the metallogenic ages of the silver and nonferrous metallic deposits in the Jiaodong Peninsula are in a limited range from 118 Ma to 111 Ma. Previous studies have demonstrated that the isotopic ages of gold deposits in the Jiaodong Peninsula range from 123 Ma to 110 Ma, while Weideshanian magmatism occurred between 126 Ma to 108 Ma. Both these ranges are grossly consistent with the metallogenic ages of silver and nonferrous metallic deposits in this study, suggesting that the large-scale mineralization occurred in the Early Cretaceous when magmatic activities were strong. This epoch may be linked to the lithosphere thinning and the thermo-upwelling extension in eastern China at that time. In addition, field investigation also shows that gold and nonferrous metallic deposits are distributed nearby the Weideshanian granite, with the nonferrous metallic deposits lying within or surrounding the granite pluton and the gold deposits outside the granite pluton. We propose the following mineralization scenario： In the Early Cretaceous, an intensive lithospheric extension induced partial melting and degassing of the metasomatized lithospheric mantle, which resulted in the formation of mantle-derived fluids enriched in metal elements. During the rapid process of magma ascent and intrusion, crust-derived fluids were activated by the magmatic thermal dome and served to further extract ore-forming materials from the crust. These fluids may have mixed with the mantle-derived fluid to form a crust-mantle mixing-type ore-forming fluid. The high-temperature conditions in the center or in contact with the granitic magmatic thermal dome would have been favorable for the formation of porphyry-type, skarn-type, and hydrothermal-vein-type ores, thus forming a series of Mo（W）, Cu, and Pb-Zn deposits in the mid-eastern Jiaodong Peninsula. In contrast, the medium- to low-temperature conditions in the periphery of the magmatic thermal dome would have favored the deposition of gold （silver） ores under the appropriate physiochemical and structural conditions. The metaliogenic epoch of the molybdenum, copper, and silver deposits, and their spatio-temporal and genetic relations to the gold deposits, as demonstrated in this study, not only provide important insights to the study of regional metallogeny, our understanding of the metallogenesis of the Jiaodong type gold deposit, and the geodynamic background of the large-scale mineralization in the Jiaodong Peninsula, but also have practical value in guiding the mineral exploration.

Geochemistry of Ore Fluids and Rb-Sr Isotopic Dating for the Wulong Gold Deposit in Liaoning, China

On the basis of detailed geological studies of the Wulong gold deposit, three metallogenic stages can be identified. With quartz fluid inclusions as an object of study, the authors investigated phase characteristics, compositional variations, temperature and pressure changes, fluid evolution, Pb isotope tracing and Rb-Sr isotopic dating of fluid inclusions entrapped in the above three metallogenic stages. The results show that Na+ is decreased obviously with metallogenic evolution, while K+ and other cations and gas compositions (H2, CO, CH4 and CO2) are increased slightly, and that the temperature and salinity vary in a pulsating manner along with the metallogenic evolution. Inverse calculation of hydrogen and oxygen isotopes indicate that at the first metallogenic stage the fluids were magmatic water, at the second stage they were dominated by magmatic water with a minor amount of meteoric water involved, and at the third stage, i.e., the final stage of metallogenesis, the fluids were composed completely of meteoric water. Its Pb isotopic composition implicates that the ore lead has some affinities with the lead in the Sanguliu granite, but the linear array of the ore-lead isotopic data reflects a mixing source of two end members. It can be deduced that the ore-forming materials and magma were both derived mainly from the same magma source region at depths. The Rb-Sr isotopic ages of the fluid inclusions are 112.2±3.2 Ma, indicating that the Wulong gold deposit was formed during the Yanshanian period.