Intra-continental back-arc basin inversion and Late Carboniferous magmatism in Eastern Tianshan,NW China:Constraints from the Shaquanzi magmatic suite

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.

Timing of carbonatite-hosted U-polymetallic mineralization in the supergiant Huayangchuan deposit,Qinling Orogen:Constraints from titanite U-Pb and molybdenite Re-Os dating

The newly-discovered supergiant Huayangchuan uranium(U)-polymetallic(Sr,Se,REEs,Ba,Nb and Pb)deposit is located in the Qinling Orogen,central China.The deposit underwent multistage mineralization,with the main carbonatite ore stage being the most important for the U,Nb,REE,Sr and Ba endowments.According to the mineral assemblages,the main carbonatite ore stage can be divided into three substages,i.e.,sulfate(Ba-Sr),alkali-rich U and REE-U mineralization.Main-stage titanite from the Huayangchuan igneous carbonatite are rich in high field strength elements(HFSEs,e.g.,Zr,Nb and REEs),and show clear elemental substitutions(e.g.,Ti vs.Nb+Fe+Al and Ca+Ti vs.Fe+Al+REE).High-precision LA-ICP-MS titanite dating yielded a U-Pb age of 209.0±2.9 Ma,which represents the mainstage mineralization age at Huayangchuan,and is coeval with the local carbonatite dyke intrusion.This mineralization age is further constrained by the Re-Os dating of molybdenite from the Huayangchuan carbonatite,which yielded a weighted mean age of 196.8±2.4 Ma.Molybdenite Re contents(337.55-392.75 ppm)and C-OSr-Nd-Pb isotopic evidence of the Huayangchuan carbonatite both suggest a mantle origin for the carbonatite.Our study supports that the Late Triassic carbonatite magmatism was responsible for the world-class U-Mo-REE mineralization in the Qinling Orogen,and that the regional magmatism and ore formation was likely caused by the closure of the Mianlue ocean and the subsequent North China-South China continent-continent collision.

Coupled trace element and SIMS sulfur isotope geochemistry of sedimentary pyrite:Implications on pyrite growth of Caixiashan Pb-Zn deposit

Colloform pyrite with core-rim texture is commonly deposited in carbonate platforms associated with the sulfide ores such as the Caixiashan Pb-Zn deposit.However,the genesis of colloform pyrite in Pb-Zn deposits,its growth controls and their geological implication are insufficiently understood.Integration of in-situ trace element and SIMS sulfur isotopes has revealed geochemical variations among these pyrite layers.These colloform pyrite occur as residual phases of core-rim aggregates,the cores are made up of very fine-grained anhedral pyrite particles,with some rims being made up of fine-grained and poorlycrystallized pyrite,while the other rims were featured with euhedral cubic pyrite.which are cemented by fine-grained calcite and/or dolomite with minor quartz.Sulfur isotope analysis shows that some wellpreserved rims have negative δ^34 S values(-28.12‰to-0.49‰),whereas most of the cores and rims have positive δ^34 S values(>0 to+44.28‰;peak at+14.91‰).Integrating with the methane and sulfate were observed in previous fluid inclusion study,we suggest that the 34 S depleted rims were initially formed by bacteria sulfate reduction(BSR),whereas the positive δ^34 S values were resulted from the sulfate reduction driven by anaerobic methane oxidation(AOM).The well-developed authigenic pyrite and calcite may also support the reaction of AOM.Combined with petrographic observations,trace element composition of the colloform pyrite reveals the incorporation and precipitation behavior of those high abundance elements in the pyrite:Pb and Zn were present as mineral inclusion and likely precipitated before Fe,as supported by the time-resolved Pb-Zn signal spikes in most of the analyzed pyrite grains.Other metals,such as Hg,Co and Ni,may have migrated as chloride complexes and entered the pyrite lattice.Arsenic and Sb,generally influenced by complex-forming reactions rather than substitution ones,could also enter the pyrite lattice,or slightly predate the precipitation of colloform pyrite as mineral inclusions,which are controlled by their hydrolysis constant in the ore fluids.The colloform pyrite may have grown inward from the rims.The successive BSR reaction process would enrich H^32/2S in the overlying water column but reduce the metal content,the nucleation of these pyrite rims was featured by strongly negative sulfur isotopes.The following AOM process should be activated by deformation like the turbidity sediment of the mudstone as the sulfide deposition are associated with fault activities that caused the emission of methane migration upward and simultaneously replenishing the metal in the column.The higher AOM reaction rate and the higher metal supply(not only Fe.but with minor other metals such as Pb and Zn) caused by sediment movement enhanced the metal concentration within the pyrite lattice.

Mineral Resource Science in China:Review and perspective

Mineral resources are essential to prosperity and security of modern societies.How mineral resources can guar-antee sustainable development of economy in countries,especially those developing countries,has long been a focus of attention of international communities.This paper provides a comprehensive summary for major ad-vance of the research on mineral resources in past decades,and proposes some key issues regarding ore-forming mechanism,exploration and utilization of major and critical mineral resources.On the basis of these aspects,we also identify four priority science issues to be addressed in the future,including(1)mechanism of both metal circulation and extremely high concentration,(2)theories and technologies of prospecting deep-earth resources,(3)investigation of mineral resources in seafloor and polar regions,and(4)efficient,clean and recycling utiliza-tion of mineral resources.It can be expected that new advances in these four issues would tremendously promote the innovation of mineral resource science,and provide scientific and technologic support to meet the demand of mineral resources for human activities and the harmonious development of both mineral-resource exploration and ecological restoration.

Deciphering fluid origins in the Paleozoic Laoshankou Fe-Cu-Au deposit, East Junggar: Constraints from noble gases and halogens

To constrain the ore-fluid source(s)of the Laoshankou Fe-Cu-Au deposit(Junggar orogen,NW China),we analyzed the fluid inclusion(FI)noble gas(Ar,Kr and Xe)and halogen(Cl,Br and I)compositions in the hydrothermal epidote and quartz.Four hypogene alteration/mineralization stages,including(I)pre-ore Ca-silicate,(II)early-ore amphibole-epidote-magnetite,(III)late-ore pyrite-chalcopyrite,and(IV)post-ore hydrothermal veining,have been identified at Laoshankou.Stage II FIs have salinity of 15.7 wt.%(NaCl eq.),I/Cl molar ratios of 75×10^(−6)-135×10^(−6),and Br/Cl molar ratios of 1.4×10^(−3)-2.1×10^(−3).The moderately-high seawatercorrected Br*/I ratios(0.5-1.5)and low 40ArE/Cl slope(-10−5)indicate the presence of sedimentary marine pore fluid,which was modified by seawater reacting with the Beitashan Fm.volcanic rocks.Stage III fluid is more saline than their stage II and IV counterparts,reaching up to 23.3 wt.%(NaCl+CaCl2 eq.)close to halite saturation(-26 wt.%).The fluid has I/Cl ratios of 75×10^(−6)-90×10^(−6) and Br/Cl ratios of 1.5×10^(−3)-1.8×10^(−3).Considering the increasing 40ArE/Cl trend toward bittern brine and the higher 36Ar content than air-saturated water(ASW),a bittern fluid source is inferred from seawater evaporation,which was modified by interaction with organic-rich marine sedimentary rocks.Stage IV FIs have lower temperature(110-228°C)and Br/Cl(0.90×10^(−3)-1.2×10^(−3)),but higher 36Ar content than ASW,indicative of dissolved evaporite or halite input.Considering also the lowδDfluid(−114‰to−144‰)andδ18Ofluid(2.1‰-3.5‰)values,meteoric water(with minor dissolved evaporites)likely dominated the stage IV fluid.The evaporites may have formed through continuous evaporation of the stage III surface-derived bittern.Involvement of non-magmatic fluids and different ore-fluid origins in stages II and III suggest that the ore-forming process was different from a typical magmatichydrothermal fluid-dominated skarn mineralization,which was previously proposed for Laoshankou.Our noble gas and halogen study at Laoshankou provide new insights on the fluid sources for the Paleozoic Fe−Cu(−Au)deposits in the Central Asian Orogenic Belt(CAOB),and our non-magmatic fluid source interpretation is consistent with the basin inversion setting for the mineralization.

褐帘石稀土活化对离子吸附型稀土矿床成矿的指示

古城矿床为华南地区新发现的一个同时富含轻重稀土的离子吸附型稀土矿床,矿体位于粗粒黑云母花岗岩风化壳中.褐帘石是粗粒黑云母花岗岩中一种重要的副矿物(占比约为0.09%(vol)),U-Pb年龄分析结果显示其结晶年龄为102.8±4.3 Ma.化学成分分析结果显示原生褐帘石具有富轻稀土的特征,其轻稀土、重稀土和轻稀土/重稀土比值分别为179778~189429、2165~4595 ppm(1 ppm=10^(–6)m^(3)/m^(3))和41~84.这些原生褐帘石轻稀土含量约占全岩轻稀土总量的97%,为古城矿区轻稀土元素的主要来源.褐帘石结构与成分分析指示,稀土元素的存在会导致其晶体结构中稀土元素与氧原子构成的化学键键长增加而键强减弱.在被岩浆-热液流体交代时,这些化学键发生破裂,进而导致轻稀土元素会被淋滤出来并进入到热液流体中,并在随后主要进入了氟碳钙铈矿中.综上,褐帘石被交代后形成氟碳钙铈矿的过程中轻稀土元素发生了活化、迁移和富集,且在该过程中轻稀土元素之间发生了分馏.本研究表明,原生褐帘石被热液流体交代有利于轻稀土元素的富集成矿,但对重稀土矿化的贡献较小.

Geochemistry and geochronology of multi-generation garnet:New insights on the genesis and fluid evolution of prograde skarn formation

Origin of garnet in skarn(magmatic vs.hydrothermal)and the prograde skarn fluid evolution are still controversial.Two generations of garnet(Grt1,Grt2)were identified at the Tongshankou deposit:Grt1 is anisotropic with oscillatory zoning and resorbed boundary,whilst Grt2 grew around Grt1 and formed oscillatory rims.In-situ LA-ICP-MS U-Pb dating of Grt1 and Grt2 yielded a lower intercept^(206)Pb/^(238)U age of 142.4±2.8 Ma(n=57;MSWD=1.16)and 142.3±9.6 Ma(n=60;MSWD=1.06),respectively,coeval with the ore formation and ore-related granodiorite emplacement.Positive Eu anomaly,non-CHARAC Y/Ho value and low TiO_(2)content,together with the mineral assemblages indicate that both Grtl and Grt2 have a hydrothermal origin.The existence of melt and melt-fluid inclusions in Grt1,together with similar LREE-enriched patterns to the granodiorite,further indicate that Grt1 may have formed in the magmatic-hydrothermal transition.Higher U contents and LREE-enriched patterns of Grt1 indicate that fluid I is mildly acidic pH and low fO_(2).The inner gray Grt2 rims(Grt2A)is HREE-enriched with low U contents,indicating that fluid II has nearly neutral pH and high fO_(2).The wider Y/Ho range and LREE-enriched patterns of the outer light-gray Grt2 rims(Grt2B)show that the evolved magmatic fluidⅡhad mixed with an external fluid,characterized by being mildly acidic pH and with high fO_(2)·Our results suggest that the prograde skarn-forming fluids can be multistage at Tongshankou,and the mixing of meteoric water may have been prominent in the prograde skarn stage.

丝绸之路经济带自然灾害与重大工程风险

丝绸之路经济带穿越了地质结构复杂、构造运动活跃、气候条件多变的地区,区域内各种原生和次生自然灾害频发.地震作为典型的原生自然灾害具有突发性强、危害范围广、破坏严重等特点,并诱发一系列次生灾害.气象灾害具有种类多、空间分布广、时间跨度大等特点.山区地质灾害大多由地震、极端降雨等灾害诱发,具有类型多样、分布广泛、危害严重等特点.该经济带沿线各类自然灾害风险严重影响沿线各国深入合作与交流,制约着社会经济的快速发展.本文阐述了丝绸之路经济带上地震灾害、气象灾害和地质灾害等三类主要自然灾害特点及其发展趋势,并针对丝绸之路经济带上的重大工程建设,提出了5点应对策略:(1)建立丝绸之路经济带孕灾背景和灾害数据库;(2)集成现有的灾害防控技术,研发减灾关键技术;(3)发展空-天-地立体、全天候的监测预警方法;(4)科学评估灾害风险;(5)建立多国协调减灾和信息共享机制.

21世纪矿产勘查的未来发展方向在哪里?

1研究背景矿产勘查研究的未来趋势取决于我们社会和工业界的需求,而这些需求在过去十年中已发生了明显的变化,并将在未来持续演变.总体上,当前所有矿床地质学家必须认真思考如何应对矿产勘查领域中的(1)深部勘查、(2)智能勘查和(3)绿色勘查等(即:Deep-Intelligent-Green(DIG)exploration)三大挑战.对于研究人员来说,最关键的是要确定我们在矿产勘查研究中应该关注什么?以及我们可以做些什么工作来应对这些矿产勘查中的挑战?

Progress and records in the study of endogenetic mineralization during collisional orogenesis

To develop and perfect the theory of plate tectonics and regional metallogeny, metal-logenesis during collisional orogenesis should be thoroughly studied and will attract increasing at-tention of more and more scientists. This paper presents the main aspects of research and discus-sions on metallogenesis during collisional orogenesis after the development of plate tectonics, and accordingly divides the study history into two stages, i.e. the junior stage during 1971-1990 and the senior stage after 1990. Beginning with the negation of mineralization in the collision regime by Guild (1971), the focus of study was put on whether there occurred any mineralization during collisional orogenesis at the junior stage. At the senior stage, which is initiated by the advance of met-allogenic and petrogenic model for collisional orogenesis, scientists begin to pay their attention to the geodynamic mechanism of metallogenesis, spatial and temporal distribution of ore deposits, ore-forming fluidization, relationship

Metallogenesis and major challenges of porphyry copper systems above subduction zones

Porphyry copper±molybdenum±gold deposits(PCDs) are the most representative magmatic-hydrothermal metallogenic system above subduction zones with important economic value. Previous studies revealed that large PCDs are generally formed from initial arc magmas(from subduction-induced partial melting of the mantle wedge), which eventually ascend to the shallow crust(3–5 km) for mineralization after a series of complex evolution processes. These processes include(1) the dehydration or partial melting of subducting slab, which induces partial melting of the metasomatized mantle wedge;(2)the ascent of mantle-derived magma to the bottom of the lower crust, which subsequently undergoes crustal processes such as assimilation plus fractional crystallization(AFC) or melting, assimilation, storage and homogenization(MASH);(3) the magma chamber formation at the bottom of the lower, middle and upper crust;(4) the final emplacement and volatilization of porphyry stocks;and(5) the accumulation of ore-forming fluids and metal precipitation. Despite the many decades of research, many issues involving the PCD metallogenic mechanism still remain to resolve, such as(1) the tectonic control on the geochemical characteristics of ore-forming magma;(2) the reason for the different lifespans of the long-term magmatic arc evolution and geologically "instantaneous" mineralization processes;(3) the source of ore-forming materials;(4) the relative contributions of metal pre-enrichment to mineralization by the magma source and by magmatic evolution;and(5) the decoupling behaviors of Cu and Au during the pre-enrichment. These issues point out the direction for future PCD metallogenic research, and the resolution to them will deepen our understanding of the metallogenesis at convergent plate boundaries.

Multiple-Stage Mineralization in the Huayangchuan U-REE-Mo-Cu-Fe Ore Belt of the Qinling Orogen,Central China:Geological and Re-Os Geochronological Constraints

The Huayangchuan ore belt is located in the western segment of Xiaoqinling Orogen in the southern margin of the North China Craton(NCC),and hosts voluminous magmatism and significant U-REE-Mo-Cu-Fe polymetallic mineralization.However,geochronological framework of the various mineralization phases in this region is poorly understood.Here,we present new Re-Os isochron ages on magnetite from the Caotan Fe deposit(2 675 ± 410 Ma,MSWD = 0.55),and on pyrite from the Jialu REE deposit(2 127 ± 280 Ma,MSWD = 1.9) and Yuejiawa Cu deposit(418 ± 23 Ma,MSWD =11.5),and Re-Os weighted average model age on pyrite from the Taoyuan Mo-U deposit(235 ± 14 Ma,MSWD = 0.17).These ages,combined with regional geology and mineralization ages from other deposits,suggest that mineralization in the Huayangchuan ore belt lasted from the Neoarchean to the Late Mesozoic.The mineralization corresponds to regional tectono-magmatic events,including the Neoarchean alkali magmatism(REE mineralization),Paleoproterozoic plagioclase-amphibolite emplacement(Fe mineralization),Paleoproterozoic pegmatite magmatism(U mineralization),Paleozoic Shangdan oceanic slab subduction-related arc magmatism(Cu mineralization),Early Mesozoic Paleo-Tethys Ocean subduction-related arc magmatism(Mo-U mineralization),and Late Mesozoic Paleo-Pacific oceanic plate subduction direction change-related Mo(-Pb) mineralization.We proposed that the Huayangchuan ore belt has undergone prolonged metallogenic evolution,and the magmatism and associated mineralization were controlled by regional geodynamic events.

Experimental study of high to intermediate temperature alteration in porphyry copper systems and geological implications

Porphyry copper systems, which provide most of the world's copper resource, are commonly associated with characteristic concentric zonation of alteration and mineralization. In-depth knowledge of the distribution and transport mechanism of elements in the alteration zones is essential for understanding the ore-forming processes. We employed flow-reaction apparatus to simulate the fluid-rock interactions during porphyry ore formation so as to investigate the mechanisms that govern the transport of elements and the development of zonation. The results indicate more heterogeneous distribution of elements in the experimental products at 450°C compared to those at lower temperatures, which implies a crucial role of temperature in controlling elements redistribution in hydrothermal systems. Heating advances potassic alteration and Ca leaching of wall rocks.To achieve the same degree of sodic alteration, it requires a higher concentration of Na+in the fluid toward higher temperature.Temperature also facilitates the incorporation of Ti, Sr and Pb into silicate minerals through cation substitution. We infer from experimental results that from the center of intermediate to mafic volcanic wall rocks toward periphery, the contents of K and Ti should decrease and the contents of Ca, Zn and Mn should increase, whereas the trend for Si and Na could be non-monotonic.This study provides experimental and theoretical insights into a variety of vital geological observations, including anhydrite formation and the widespread development of potassic rather than sodic alteration in porphyry copper deposits.

Advances in Isotope Geochronology and Isotope Geochemistry:A Preface

Isotope geochronology and isotope geochemistry are important branches of geochemistry. They are based on variations in radiogenic or stable isotope ratios of elements and provide key chemical fingerprints to understand dynamic evolution of the Earth and other planetary bodies from the past to the present, and from their interior to exterior systems.

What is the Future Road for Mineral Exploration in the 21st Century?

The future trends for mineral exploration study should depend on the demands from our society and industry,which have clearly changed in the past decade and will continuously evolve in the future.In general,three major challenges on mineral exploration have been raised for all economic geologists,including:(1)deep exploration;(2)intelligent exploration and;(3)green exploration(i.e.,“DIG”exploration).