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Journal of Earth Science 2024年

作者： Jing Lei Yilin Xiao Chinese Academy of Sciences Center of Excellence in Comparative Planetology cas key laboratory of crust-mantle materials and environments School of Earth and Space Sciences University of Science and Technology of China

Oxygen fugacity of magmas and hydrothermal fluids is an important factor affecting element migration and mineralization. Zircon is an excellent monitor for oxygen fugacity of melts and fluids due to its exceptionally stable nature. However， zircon oxybarometers involve many complex algorithms leading to difficulties in use. Therefore， there is an urgent need to realize automatic calculation of various zircon oxybarometers. This study developed a Visual Basic for Applications (VBA) program， ZirconfO2， built in an ExcelTMworkbook， for calculating the oxygen fugacity of magmatic and hydrothermal fluids through the trace element characteristics of zircons. The program covers almost all the algorithms of zircon oxybarometers commonly-used so far. Through the user-friendly interface， users may input data expediently， obtain multiple results of various algorithms and find the most reliable oxygen fugacity range， effectively avoiding the possible misdirection of a single algorithm.

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Trace Element Mobility in Subducted Marble and Associated Eclogite:Constraints from UHP Rocks in the Shuanghe Area,Central-East China

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Journal of Earth Science 2024年第1期35卷 1-15页

作者： Xingao Hou Zhiqiang Yu Shefa Chen Lei Liu Yilin Xiao key laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring Ministry of EducationSchool of Geosciences and Info-PhysicsCentral South UniversityChangsha 410083China key laboratory of Mineralogy and Metallogeny Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640China cas key laboratory of crust-mantle materials and environments School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China

In order to decipher element mobility in UHP meta-sedimentary rocks in the continental subduction zone,major and trace element compositions are investigated for a continuous profile from a representative UHP region in the Dabie Mountains.Among the lithologic contact zone,contents of K,Ca,LREE,and LILE exhibit varying degrees of downward trends in both marble and eclogite toward the contact zone,indicating that marble and their associated eclogite can release a large amount of K,Ca,and a small number of LILEs and LREEs.Titanite is the main Ti phase in both marble and eclogite.Titanite rims around rutile can occasionally be seen in eclogite.Contents of Ti and HFSE exhibit a well-coupled relation among marble and eclogite,indicating that substantial Ti and HFSEs were migrated from eclogite to marble,in accord with the capacity of a melt medium.Rutiles and titanites in marble exhibit a relatively limited variation in Nb/Ta ratios(12.9-16.2),similar to those of titanites in eclogite(14.2-16.7),which demonstrates that rutiles and titanites in marble were sourced from eclogite because of short-distance migrations of Ti and HFSEs.According to the P-T path and the temperature and pressure conditions of the peak metamorphism reported by previous studies,the eclogite associated with marble may not form supercritical fluids in the subduction zone because of the addition of carbonate minerals.

关键词： UHP metamorphism eclogite marble element migration fluid actions geochemistry

Reverse metasomatism of subduction zone fluids

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Science China Earth Sciences 2024年第2期67卷 634-638页

作者： Yixiang CHEN School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China key laboratory of crust-mantle materials and environments Chinese Academy of SciencesHefei 230026China Center of Excellence for Comparative Planetology Chinese Academy of SciencesHefei 230026China

1.Fluid metasomatism in subduction zones Subduction zones are the key tectonic setting that links Earth's surficial sphere to deep sphere(Zheng and Chen,2016).Fluid action occurring in subduction zones is closely related to many important geological processes such as volcanic and seismic activity,the migration,enrichment and mineralization of metallogenic elements,mass transport and crust-mantle material cycling,and the evolution of Earth's surface environment.Therefore,it is of great significance to study the sources,properties and geochemical effects of subduction zone fluids(Zheng,2019).

关键词： subduction metasomatism Earth

Lithium Isotope Analytical Methods and Implications for Rare-Metal Mineralization in Granite-Pegmatite Systems: An Overview

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Journal of Earth Science 2024年

作者： Xiang-Ying Ye Bin Li Dong-Bo Tan Ke-Cheng Liu Zhi-Yong Zhu Hafiz Muhammad Siddique Yi-Lin Xiao key laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Ministry of Education) School of Geosciences and Info-physics Central South University cas key laboratory of Geospace Environment and Department of Plasma Physics and Fusion Engineering University of Science and Technology of China Institute of Geology Chinese Academy of Geological Sciences cas key laboratory of crust-mantle materials and environments School of Earth and Space Sciences University of Science and Technology of China Chinese Academy of Sciences Center of Excellence in Comparative Planetology

The origin of highly-fractionated granite-pegmatite systems and their associated rare metal mineralization has been widely studied， but there is still ongoing debate. Prevailing hypotheses suggest that pegmatite formation and the associated rare metal mineralization are closely related to aqueous fluid processes. Lithium (Li) isotope analysis has been widely applied to trace granite-pegmatite evolution. This is because lithium is widely present in various minerals (e.g.， mica， tourmaline) that record the melt and fluid compositions， and lithium isotopes are sensitive to magmatic-hydrothermal processes. We briefly review the methodology of Li isotope analyses， the mechanisms of Li isotopic fractionation， and， in particular， Li isotope fractionation in granite-pegmatite system based on Li isotope data we have collected and the latest developments in Li isotope geochemistry. With the development of analytical technology， high-precision measurement of the Li content and isotopic compositions have facilitated a series of scientific breakthroughs in understanding the magmatic-hydrothermal evolution of rare-element ore deposits. Li isotope analysis on bulk mineral separates show ability to trace various hydrothermal processes (e.g. exotic or exsolved fluids). In situ Li isotope analysis methods has been enhanced by the development of new， homogeneous mineral reference materials. In situ SIMS and LA-MC-ICP-MS Li isotope measurements on minerals (e.g.， tourmaline) will likely become more important in studying the fluid–rock interactions in magmatic， metamorphic， and hydrothermal processes， as well as on pegmatite petrogenesis and rare-metal mineralization.

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海水对下寒武统黑色页岩V矿化/富集的贡献

Science Bulletin 2024年第8期69卷 1006-1010页

作者：董琳慧卫炜徐林刚吝祎勃刘泽瑞潘松圻荆振华黄方 cas key laboratory of crust–mantle materials and environments School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China cas Center for Excellence in Comparative Planetology University of Science and Technology of ChinaHefei 230026China School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China State key laboratory for Mineral Deposits Research School of Earth Sciences and EngineeringNanjing UniversityNanjing 210023China Frontiers Science Center for Critical Earth materials Cycling Nanjing UniversityNanjing 210023China School of Earth Resources China University of GeosciencesWuhan 430074China Research Institute of Petroleum Exploration and Development China National Petroleum CorporationBeijing 100083China

Early Cambrian black shales along the southern margin of the Yangtze Block are characterized by polymetallic mineralization in the lower part,including Ni-Mo sulfide ore,V ore,barite ore,phosphate ore,and"stone coal"(Fig.1a)[1,2],which were likely related to or at least coincident with the global ocean oxygenation event[3]and the radiation of early animals[4].The source of oreforming elements and the metallogenic mechanism of these polymetallic mineralization layers are highly debated.The models proposed include hydrothermal venting,seawater scavenging,and a combination of key mineralization factors such as terrigenous input,hydrothermal supply,seawater contribution,and impacts of clay mineral and organic matter(Fig.S1 online)[1].

关键词： mineralization hydrothermal shale

Tectonic evolution of convergent plate margins and its geological effects

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Science China Earth Sciences 2022年第7期65卷 1247-1276页

作者： Yongfei ZHENG Yixiang CHEN Renxu CHEN Liqun DAI cas key laboratory of crust and mantle materials and environments School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China

Oceanic lithosphere is generated at divergent plate boundaries and disappears at convergent plate boundaries.Seafloor spreading and plate subduction together constitute the physical coupling and mass conservation relationships to the movement of lithospheres on Earth.Subduction zones are a key site for the transfer of both matter and energy at converging plate boundaries,and their study has been the hot spot and frontier of Earth system science since the development of plate tectonics theory.As far as the dynamic regime and geothermal gradient of convergent plate margins are concerned,they have different properties in different stages of the subduction zone evolution.In general,the early low-angle subduction leads to compressional tectonism dominated by low geothermal gradients at the plate interface,and the late high-angle subduction results in extensional tectonism dominated by high geothermal gradients at the plate interface and its hanging wall.Active rifts are produced along suture zones through not only slab rollback or slab breakoff in the terminal stage of oceanic subduction but also foundering and thinning of the lithosphere in the post-subduction stage.Due to the differences and changes in the geometric and thermobaric structures of convergent plate margins,a series of changes in the type of metamorphism and magmatism can occur in active and fossil subduction zones.Dehydration and melting of the subducting oceanic crust are prominent at subarc depths,giving rise to fluids that dissolve different concentrations of fluid-mobile incompatible elements.The subduction zone fluids at subarc depths would chemically react with the overlying mantle wedge peridotite,generating metasomatites as the mantle sources of mafic magmas in oceanic and continental arcs.However,these metasomatites did not partially melt immediately upon the fluid metasomatism to trigger arc magmatism,and they did not melt until they were heated by asthenospheric convection due to rollback of the subducting slab.Therefore,recognition of the c

关键词： Plate tectonics Continental geology Convergent margins Continental rifting Subduction zone Orogenic belt

Magnesium isotope geochemistry of the carbonate-silicate system in subduction zones

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National Science Review 2022年第6期9卷 23-33页

作者： Shui-Jiong Wang Shu-Guang Li State key laboratory of Geological Processes and Mineral Resources and Institute of Earth SciencesChina University of Geosciences (Beijing) cas key laboratory of crust-mantle materials and environments School of Earth and Space SciencesUniversity of Science and Technology of China

The lighter magnesium(Mg) isotopic signatures observed in intraplate basalts are commonly thought to result from deep carbonate recycling, provided that the sharp difference in Mg isotopic composition between surface carbonates and the normal mantle is preserved during plate subduction. However, deep subduction of carbonates and silicates could potentially fractionate Mg isotopes and change their chemical compositions. Subducting silicate rocks that experience metamorphic dehydration lose a small amount of Mg, and preserve the original Mg isotopic signature of their protoliths. When the dehydrated fluids dissolve carbonate minerals, they may evolve into lighter Mg isotopic compositions. The solubility of carbonate minerals in fluids decreases in the order of calcite, aragonite, dolomite, magnesite and siderite, leading to selective and partial dissolution of carbonate minerals along the subduction path. At the island arc depth(70–120 km), the metamorphic fluid dissolves mainly Mg-poor calcites, and thus the fluid has difficulty modifying the Mg isotopic system of the mantle wedge and associated arc basalts. At the greater depth of the back arc system or continental margin(>150 km), the supercritical fluid can dissolve Mg-rich carbonate minerals, and its interaction with the mantle wedge could significantly imprint the light Mg isotopic signature onto the mantle rocks and derivatives. Meanwhile, the carbonate and silicate remaining within the subducting slab could experience elemental and isotopic exchange, during which the silicate can obtain a light Mg isotopic signature and high CaO/Al2O3, whereas the carbonates, particularly the Ca-rich limestone, shift Mg isotopes and Mg O contents towards higher values. If this isotopic and elemental exchange event occurs widely during crustal subduction, subducted Ca-rich carbonates can partially transform into being Mg-rich, and a portion of recycled silicates(e.g. carbonated eclogites) can have light Mg isotopic composition alongside carbonates. Both serve as the low-δ26M

关键词： magnesium isotope fractionation deep carbon cycle subduction carbonate

Detrital Zircon Geochronology and Provenance of Metasedimentary Rocks from the Susong Complex Zone in the Dabie Orogen

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地质学报:英文版 2023年第5期97卷 1335-1354页

作者： WU Zheng YANG Yang LIU Yican ZHANG Chengwei cas key laboratory of crust-mantle materials and environments School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China

The Susong complex zone is a relatively low-grade metamorphic unit located in the southern part of the Dabie orogen and preserves a variety of metasedimentary rocks,mostly with epidote-amphibolite facies.However,their depositional age,provenance and tectonic setting of sedimentary protolith remain controversial due to the lack of fossils,precise dating and integrated geochemical investigation.This study has conducted whole-rock elemental,and zircon U-Pb SHRIMP dating and Lu-Hf isotope analyses on three types of representative metasedimentary rocks including garnetbearing mica-quartz schist,graphite-muscovite-quartz schist and dolomitic marble from the Susong complex zone.The UPb SHRIMP dating data indicate that the sedimentary protolith of these rocks have the maximum depositional ages of less than 840-750 Ma and have various sedimentary provenances.In combination with zircon Lu-Hf isotope compositions,the provenance of the metasedimentary rocks in the region is for the first time documented to be mainly derived from four groups of magmatic rocks formed at~2.5 Ga,~2.0 Ga,~1.4 Ga and~0.8 Ga in response to four episodes of igneous activity in the northeastern margin of the Yangtze Block.The conventional geothermobarometry combined with rare metamorphic zircon ages indicate that the studied rocks underwent the Late Triassic continental subduction-related metamorphism with peak epidote-amphibolite facies conditions at P=0.34-0.91 GPa and T=427-532°C.In addition,results of the elemental contents(i.e.,La,Ce,Th andΣREE)and ratios(i.e.,Eu/Eu^(*)and La_(N)/Yb_(N))suggest that the protoliths of the metasedimentary rocks were mainly shales,wackes and limestones,most probably related to the Rodinia supercontinent rifting along the northern margin of the Yangtze Block during the Neoproterozoic.

关键词： provenance metasedimentary rocks SHRIMP dating Hf isotope Precambrian Susong complex zone

Plate tectonics in the twenty-first century

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Science China Earth Sciences 2023年第1期66卷 1-40页

作者： Yong-Fei ZHENG cas key laboratory of crust-mantle materials and environments Hefei 230026China School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China

Plate tectonics was originally established as a kinematic theory of global tectonics,in which the Earth’s rigid outer layer,the lithosphere,consists of different size plates that move relative to each other along divergent,convergent or transform boundaries overlying the ductile asthenosphere.It comprises three elements:rigid lithosphere plates,ductile asthenosphere,and coupled movement systems.It operates through the interlinked processes of continental drift,seafloor spreading and lithospheric subduction,resulting in the generation,modification and demise of lithospheres throughout geological time.The system of lithospheric plates in horizontal and vertical movements forms the spatiotemporal linkages of matter and energy between the surface and interior of Earth,advancing the kinematic theory with a dynamic explanation.While top-down tectonics through lithospheric subduction plays a key role in the operation of plate tectonics,it is balanced for the conservation of both mass and momentum on the spherical Earth by bottom-up tectonics through asthenospheric upwelling to yield seafloor spreading after continental breakup.The gravity-driven subduction of cool lithosphere proceeds through convergence between two plates on one side,and rollback of the subducting slab makes the vacancy for upwelling of the hotter asthenosphere to form active rifting in backarc sites.Plate convergence is coupled with plate divergence between two plates along mid-ocean ridges on the other side,inducing passive rifting for seafloor spreading as a remote effect.Thus,plate tectonics is recognizable in rock records produced by tectonic processes along divergent and convergent plate margins.Although the asthenospheric upwelling along fossil suture zones may result in continental breakup,seafloor spreading is only induced by gravitational pull of the subducting oceanic slab on the remote side.Therefore,the onset and operation of plate tectonics are associated with a series of plate divergent-convergent coupling systems,and they are critically

关键词： Continental breakup Seafloor spreading Oceanic subduction Continental collision Lithospheric thinning Asthenospheric upwelling

First finding of continental deep subduction in the Sesia Zone of the Western Alps and implications for subduction dynamics

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National Science Review 2023年第5期10卷 154-166页

作者： Yi-Xiang Chen Kun Zhou Qiang He Yong-Fei Zheng Hans-Peter Schertl Kun Chen cas key laboratory of crust-mantle materials and environments School of Earth and Space SciencesUniversity of Science and Technology of China Center of Excellence for Comparative Planetology Chinese Academy of Sciences Institute of Geology Mineralogy and Geophysics Faculty of GeosciencesRuhr University Bochum

Continental deep subduction after the closure of large oceanic basins is commonly ascribed to the gravitational pull of the subducting oceanic slab.However,it is not clear how continental lithosphere adjacent to small oceanic basins was subducted to mantle depths.The Sesia Zone in the Western Alps provides an excellent target for exploration of subduction dynamics in such a tectonic setting.Here we report the first finding of coesite in a jadeite-bearing orthogneiss from the Sesia Zone,providing the first evidence for deep subduction of the continental crust to mantle depths for ultrahigh-pressure(UHP)metamorphism in this zone.Three coesite inclusions were identified by laser Raman spectroscopy in two garnet grains.Based on zircon U-Pb dating and trace element analysis, the UHP metamorphic age was constrained to be 76.0 ±1.0 Ma.The phase equilibrium modeling yields peak metamorphic pressures of2.8-3.3 GPa,demonstrating the continental deep subduction to mantle depths of>80 km.The subducted continental crust was a rifted hyperextended continental margin,which was converted to the passive continental margin during seafloor spreading and then deeply subducted during the oblique convergence between the Adria microplate and Eurasian plate in the Late Cretaceous.Because the slab pull could only play a limited role in closing small oceanic basins for continental collision,the distal push of either continental breakup or seafloor spreading is suggested as the major driving force for the deep subduction of continental crust in the Western Alps.Therefore,deep subduction of the continental crust bordering small oceanic basins would have been induced by the far-field stress of compression,whereas that bordering large oceanic basins was spontaneous due to the oceanic slab pull.This provides a new insight into the geodynamic me chanism of continental deep subduction.

关键词： coesite ultrahigh-pressure metamorphism continental deep subduction Western Alps far-field stress