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Effect of isotope diffusion in solids on isochron ages under -pper mantle conditions

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Chinese science Bulletin 1997年第6期42卷 492-495页

作者： ZHI Xiachen, CHEN Zengbing, ZHANG Xuehua and zheng yongfei1. Department of {2. and {3. sciences, university of science and technology of china, Hefei 2.002., china: 2.Advanced Centre for {2. science and Astronomy, USTC, Third World Academy of science, Hefei 2.002., china

DODSON presented the concepts of closure temperature (T_c), transitional temperature range (T_h—T_l) and T_lT_l, the effect of matter transfer by diffusion on radiometric dating is not negligible in the transitional ... 详细信息

DODSON presented the concepts of closure temperature (T_c), transitional temperature range (T_h—T_l) and T_learth crust, geochronometers work usually under cooling conditions of Tearth mantle at T>T_l, the effect of matter transfer by diffusion on radiometric dating is not negligible in the transitional temperature range

关键词： diffusion in solids temperature transitional range isochron age lithospheric mantle.

北秦岭松树沟榴闪岩变质演化:石榴石矿物学和锆石年代学制约

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地球科学 2024年第8期49卷 2714-2735页

作者：林少伟张强强高晓英郑永飞中国科学院壳幔物质与环境重点实验室中国科学技术大学地球和空间科学学院安徽合肥230026 中国科学院比较行星学卓越创新中心安徽合肥230026

北秦岭造山带早古生代的构造格局和变质演化过程长期以来存在较大争议,是地学界比较关注的问题之一.尽管前人对松树沟变质岩进行了大量的同位素年代学研究工作,但是峰期榴辉岩相变质时间的限定仍然存在较大争议.基于此,以松树沟榴闪岩... 详细信息

北秦岭造山带早古生代的构造格局和变质演化过程长期以来存在较大争议,是地学界比较关注的问题之一.尽管前人对松树沟变质岩进行了大量的同位素年代学研究工作,但是峰期榴辉岩相变质时间的限定仍然存在较大争议.基于此,以松树沟榴闪岩为研究对象,进行系统的石榴石矿物学和锆石年代学研究.根据岩相学显微结构、矿物包裹体和矿物地球化学成分研究,在榴闪岩中识别出进变质(52.~611℃/1.4~3.0 kbar)、峰期(742.749℃/>3.0 GPa)以及退变质(72.~764℃/7.3.8.3.kbar)3.变质矿物组合.锆石年代学研究识别出3.年龄:G1为残留锆石核部,具有典型岩浆振荡环带,富集HREE,明显的Eu负异常,具有746±16 Ma到72.±7 Ma的锆石2.6Pb/2.8U年龄,表明榴闪岩的原岩结晶时代为新元古代时期;G2.石无环带或保留较弱的切割原岩锆石的振荡环带,具有陡峭的HREE配分型式,明显变化的Eu异常,属于变质重结晶锆石,具有从492.15 Ma到547±17 Ma较大变化范围的2.6Pb/2.8U值.G3.石主要靶上位于锆石边部以位于石榴石边部与其平衡共存的原位锆石为主,具有云雾状或冷杉叶状CL特征,2.6Pb/2.8U年龄范围为491~480 Ma(加权平均年龄为488±10 Ma),富集MREE,亏损HREE,低Th/U比值(0.01~0.04),微弱的Eu异常,表明其形成于榴辉岩相变质阶段,代表峰期变质年龄.此外,我们在榴闪岩中代表石榴石峰期的边部发现包裹大量呈定向的棒状出溶体Rt+Ap+Qz,可能表明该岩石曾经历过超高压变质作用.松树沟榴闪岩原岩是来源于Rodinia超大陆在新元古代裂解出来的北秦岭微陆块,于寒武纪开始深俯冲并在488 Ma达到峰期榴辉岩相,而后发生折返并经历角闪岩相退变质作用.

关键词：榴闪岩多期次变质石榴石锆石北秦岭造山带俯冲带地球化学

Low-grade metamorphic rocks in the Dabie-Sulu orogenic belt:A Passive-margin accretionary wedge deformed during continent subduction

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Low-grade metamorphic rocks in the Dabie-Sulu orogenic belt:...

Fluid-solid coupling numerical simulation of micro-disturbance grouting treatment for excessive deformation of shield tunnel

中生代以来中国大陆板块作用过程学术研讨会

作者： Yong-Fei zheng, Jian-Bo ZHOU Yuan-Bao Wu school of {2. and {3. sciences, university of science and technology of china, Hefei 2.002.

＜正＞Duringsubuctionofanoceanicplate,marinesedimentsandunderlyingrocksgenerallycanbescrapedo***-marginaccretio***edbythesubductionofanoceanicplate,butitislessoftenreportedforanorogenicbeltresultingfromthesubductionofa

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Underground space 2024年第6期19卷 87-100页

作者： Yanjie Zhang zheng Cao Chun Liu Hongwei Huang College of Civil Engineering and Architecture Henan University of TechnologyZhengzhou 450001China school of earth {2. and Engineering Nanjing UniversityNanjing 210023China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji UniversityShanghai 200092China Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai 200092China

Micro-disturbance grouting is a recovery technique to reduce the excessive deformation of operational shield tunnels in urban *** grout mass behaves as a fluid in the ground before hardening to form a grout–soil mixture,which highlights the necessity of using fluid–solid coupling method in the simulation of grouting *** a discrete element modeling environment,this paper proposes a novel fluid-solid coupling method based on the pore density flow *** demonstrate the effectiveness of this method,it is applied to numerical simulation of micro-disturbance grouting process for treatment of large transverse deformation of a shield tunnel in Shanghai Metro,*** simulation results reveal the mechanism of recovering tunnel convergence by micro-disturbance grouting in terms of compaction and fracture of soil,energy analysis during grouting,and mechanical response of soil-tunnel interaction ***,the influence of the three main grouting parameters(i.e.,grouting pressure,grouting distance,and grouting height)on tunnel deformation recovery efficiency is evaluated through parametric *** order to efficiently recover large transverse deformation of shield tunnel in Shanghai Metro,it is suggested that the grouting pressure should be about 0.55 MPa,the grouting height should be in the range of 6.2.7.0 m,and the grouting distance should be in the range of 3.0–3.6 *** results provide a valuable reference for grouting treatment projects of over-deformed shield tunnel in soft soil areas.

关键词： Fluid-solid coupling Discrete element method Pore density flow Micro-disturbance grouting Soil-tunnel interaction

Metamorphism, fluid behavior and magmatism in oceanic subduction zones

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science china {2. {3. 2020年第1期63卷 52-77页

作者： Chimjing WEI yongfei zheng Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China school of earth and {2. {3. University of Science and Technology of ChinaHefei 230026China

Based on the updated results of experimental petrology and phase equilibria modelling and combined with the available thermal structure models of subduction zones, this paper presents an overview on the dehydration and melting of basic,sedimentary and ultrabasic rocks that occur in the different stages during oceanic subduction processes and their influences on magmatism above subduction zones. During the subduction at the forearc depth of 2.0 km. For example, more than 90% water in basic rocks is released by the successive dehydration of chlorite, glaucophane, talc and lawsonite in the subarc depths. This is diversely in contrast to the previous results from synthetic experiments. Ultrabasic rocks may undergo strong dehydration through antigorite, chlorite and phase 10 ? at the subarc depth of 12.–2.0 km. However,sediments can contribute minor fluids at the subarc depth, one main hydrous mineral in which is phengite(muscovite). It can stabilize to ~3.0 km depth and transform into K-hollandite. After phengite breaks down, there will be no significant fluid release from oceanic slab until it is subducted to the mantle transition zone. In a few hot subduction zones, partial melting(especially flux melting) can occur in both sediments and basic rocks, generating hydrous granitic melts or supercritical fluids, and in carbonates-bearing sediments potassic carbonatite melts can be generated. In a few cold subduction zones, phase A occurs in ultrabasic rocks, which can bring water deep into the transition zone. The subducted rocks, especially the sediments, contain large quantities of incompatible minor and trace elements carried through fluids to greatly influence the geochemical composition

关键词： Oceanic subduction Metamorphism Phase equilibria Fluid activity Subduction zone magmatism Carbon cycle

Tectonic evolution of the Qinling-Tongbai orogenic belt

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Tectonic evolution of the Qinling-Tongbai orogenic belt

Sm-Nd AND Rb-Sr AGES AND GEOCHEMISTRYOF VOLCANICS FROM THE DINGYUANFORMATION IN DABIE MOUNTAINS,CENTRAL china: EVIDENCE TO THE PALEOZONIC MAGMATIC ARC

中国矿物岩石地球化学学会第13.学术年会

作者： WU Yuan-bao~1,zheng Yong-fei~2.1.State Key Laboratory of Geological Processes and Mineral Resources,Faculty of earth {2.,{3. university of Geo{2., Wuhan 43.074,{3. 2.CAS Key Laboratory of Crust-Mantle Materials and Environments,school of earth and space {2.,university of {12. and technology of {3.,Hefei 2.002.,{3.

＜正＞The Qinling-Tongbai-Dabie-Sulu orogenic belt marks the suture between the North and South china Blocks in Central china,forming one of the most important orogens in the eastern *** are hot controversies about the location and number of sutures and the timing of arc-continent and continent-continent collisions during the convergence between the North and South china *** Dabie-Sulu orogenic belt is characterized by the occurrence of Triassic UHP eclogite-facies metamorphic rocks due to the Triassic continental deep subduction. Thus,the Triassic continent-continent collision is evident in east-central *** the other hand,there are Paleozoic events of arc-continent collision in the Qinling-Tongbai orogenic belt that were overprinted by the Triassic process of continental *** has caused much complexity on the time and location of arc-continent and continent-continent collisions between the North and South china *** present an

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Scientia Geologica Sinica 1998年第4期 461-470页

作者： Shuguang Li Weili Han Fang Huang yongfei zheng (Department of {2. and {3. sciences, university of science and technology of china, Hefei, Anhui2.002., china)Siqing Zhang and Zongheng ZhangGeological team No.3.of the Hen an Province, Xinyang, 464000

The meta-basic volcanic rocks from the Dingyuan formation in Beihuaiyang zone of Dabie Mountainshave typical island arc geochemical feature : e.g. negative anomalies of Nb, Ti, P in trace elementalspidediagram and high LREE, Ba, Ph abundances as well as high La/Nb, Ba/Nb, TI/Nb ratios. Their SmNd and Rb-Sr whole rock isochrons give the ages of 446 ± 2. Ma and 444 ± 3. Ma respectively. Basedon these geochemical feature and ages as well as their tectonic setting at convergent plate boundary, wesuggest that they were formed in a typical island arc environment in the late Ordovician to early *** is the first evidence to the Paleozoic magmatic arc in the Dabie Mountains.

关键词： Nd Rb Sr Sm-Nd AND Rb-Sr AGES AND GEOCHEMISTRYOF VOLCANICS FROM THE DINGYUANFORMATION IN DABIE MOUNTAINS,CENTRAL china

The timing of continental collision between India and Asia

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science Bulletin 2018年第24期63卷 1649-1654页

作者： yongfei zheng Fuyuan Wu Key Laboratory of Crust-Mantle Materials and Environments Chinese Academy of SciencesSchool of Earth and Space SciencesUniversity of Science and Technology of China State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences

The timing of continental collision between India and Asia has been controversial for a long time because of the difficulty in screening isotopic ages for different types of tectonothermal event along the convergent continental boundary. After distinguishing the collisional orogeny from the precollisional accretionary orogeny and the postcollisional rifting orogeny, an age range of 55 ± 10 Ma is obtained to mark the collisional orogeny in the Early Cenozoic rather than throughout the Cenozoic. This age range provides the resolution to the timing of tectonic reactivation not only for reworking of the marginal arc systems in the Early Cenozoic but also for overprinting of granulite facies metamorphism on eclogites in the Late Cenozoic. In particular, superimposition of the rifting orogeny on both accretionary and collisional orogens in the Late Cenozoic is the key to the reactivation of both Gangdese and Himalayan orogens for contemporaneous metamorphism and magmatism at high thermal gradients. Therefore, rise of the plateau may be caused by underplating of the asthenospheric mantle for rifting orogeny in the composite Himalayan–Tibetan orogens after foundering of their roots in the Late Cenozoic.

关键词： Himalayan orogen Gangdese orogen Neo-Tethys Ocean Accretionary orogeny Collisional orogeny Rifting orogeny

Mantle geochemistry: Insights from ocean island basalts

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science china {2. {3. 2017年第11期60卷 1976-2000页

作者： HUANG ShiChun zheng yongfei Department of Geoscience University of Nevada CAS Key Laboratory of Crust-Mantle Material and Environment School of Earth and Space Sciences University of Science and Technology of China

The geochemical study of the earth's mantle provides important constraints on our understanding of the formation and evolution of earth, its internal structure, and the mantle dynamics. The bulk earth composition is inferred by comparing terrestrial mantle rocks with chondrites, which leads to the chondritic earth model. That is, earth has the same relative proportions of refractory elements as that in chondrites, but it is depleted in volatiles. Ocean island basalts(OIB) may be produced by mantle plumes with possible deep origins; consequently, they provide unique opportunity to study the deep earth. Isotopic variations within OIB can be described using a limited number of mantle endmembers, such as EM1, EM2.and HIMU, and they have been used to decipher important mantle processes. Introduction of crustal material into the deep mantle via subduction and delamination is important in generating mantle heterogeneity; however, there is active debate on how they were sampled by mantle melting, i.e.,the role of olivine-poor lithologies in the OIB petrogenesis. The origin and location of high 3.e/4He mantle remain controversial,ranging from unprocessed(or less processed) primitive material in the lower mantle to highly processed materials with shallow origins, including ancient melting residues, mafic cumulates under arcs, and recycled hydrous minerals. Possible core-mantle interaction was hypothesized to introduce distinctive geochemical signatures such as radiogenic 186 Os and Fe and Ni enrichment in the OIB. Small but important variations in some short-lived nuclides, including 142.Nd, 182.W and several Xe isotopes, have been reported in ancient and modern terrestrial rocks, implying that the earth's mantle must have been differentiated within the first 100 Myr of its formation, and the mantle is not efficiently homogenized by mantle convection.

关键词： Mantle structure Mantle composition Crustal components Crust-mantle interaction Crustal recycling