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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 *** 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 *** is the main Ti phase in both marble and *** rims around rutile can occasionally be seen in *** 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 *** 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 *** 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

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eclogite-melt/peridotite reaction: Experimental constrains on the destruction mechanism of the North China Craton

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Science China Earth Sciences 2010年第6期53卷 797-809页

作者： WANG Chao JIN ZhenMin GAO Shan ZHANG JunFeng ZHENG Shu State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesWuhan 430074China State Key Laboratory of Inorganic Synthesis and Preparative Chemistry College of ChemistryJilin UniversityChangchun 130012China

To study the mechanism of melt-peridotite reaction pertinent to the destruction of the North China Craton (NCC) lithosphere, a series of experiments were performed at a pressure of 2.0 GPa and temperatures from 1250 to 1400°C using Bixiling eclogite and Damaping peridotite as starting materials. The experimental results show that the reaction between eclogite melt and peridotite causes dissolution of olivine and orthopyroxene and precipitation of clinopyroxene in the melt. The experimental run products, characterized by a lherzolite/pyroxenite/garnet-pyroxenite sequence, are consistent with the mantle xenoliths in the Neogene Hannuoba basalt of the NCC found by Liu et al. (2005). It suggests that the mafic lower continental crust was probably recycled into the mantle during the Mesozoic Era. In the experiments conducted at 1300 and 1350°C, the resulting melts have a high Mg# andesite signature, indicating that the melt-peridotite reaction may have played a major role in the generation of high Mg# andesite. Our experimental results support the hypothesis that melts derived from foundered eclogite in the asthenosphere will consume the lithospheric peridotites. Therefore, melt-peridotite reaction is an important mechanism for the destruction/thinning of the lithosphere.

关键词： eclogite peridotite melt/peridotite reaction high Mg# andesite delamination destruction of lithosphere

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Application of microprobe-based flank method analysis of Fe^3＋ in garnet ofNorth Qilian eclogite and its geological implication

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Science Bulletin 2018年第5期63卷 300-305页

作者： Xiaoli Li Shuguang Song Lifei Zhang E. Heidi Hofer The Key Laboratory of Orogenic Belts and Crustal Evolution MOE School of Earth and Space Sciences Peking University Beijing 100871 China Institut fur Geowissenschaften Facheinheit Mineralogie Johann Wolfgang Goethe-Universitat D-60054 Germany

A newly developed microprobe-based methodology(the Flank Method)for Fe^(3+)/RFe quantification has been successfully applied to some natural garnets from the North Qilian eclogites by JEOL JXA-8100microprobe at Peking *** results demonstrated an obvious discrepancy in comparison with the outcomes by conventional stoichiometric *** methodology allows to measure theFe^(3+)/Rmeasurement of Fe^(3+)According to the compositional zonation displayed in the studied eclogitic garnets from North Qilian,a prograde metamorphic°C to 22 kbar,600°C was *** interestingly,the measured Fe^(3+)/RFe ratios in garnets decreasing from core to rim may probably imply that the oxygen fugacity(f O_2)declines with the depth of the subduction zone.

关键词： Microprobe Flank method Ferric iron GarnetNorth Qilian eclogite

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Mafic Archean continental crust prohibited exhumation of orogenic UHP eclogite

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Geoscience Frontiers 2021年第5期12卷 411-420页

作者： Richard M.Palin James D.P.Moore Zeming Zhang Guangyu Huang Jon Wade Brendan Dyck Department of Earth Sciences University of OxfordOxford OX13ANUnited Kingdom Earth Observatory of Singapore Nanyang Technological UniversitySingapore Institute of Geophysics SGEESVictoria University of WellingtonWellingtonNew Zealand Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Department of Earth Environmental and Geographical SciencesUniversity of British ColumbiaKelowna V1V 1V7Canada

The absence of ultrahigh pressure(UHP)orogenic eclogite in the geological record older than c.0.6 Ga is problematic for evidence of subduction having begun on Earth during the Archean(4.0-2.5 Ga).Many eclogites in Phanerozoic and Proterozoic terranes occur as mafic boudins encased within low-density felsic crust,which provides positive buoyancy during subduction;however,recent geochemical proxy analysis shows that Archean continental crust was more mafic than previously thought,having greater proportions of basalt and komatiite than modern-day ***,we show via petrological modelling that secular change in the petrology and bulk composition of upper continental crust would make Archean continental terranes negatively buoyant in the mantle before reaching UHP *** or delaminated Archean continental crust passes a point of no return during metamorphism in the mantle prior to the stabilization of coesite,while Proterozoic and Phanerozoic terranes remain positively buoyant at these *** orogenic eclogite may thus readily have formed on the Archean Earth,but could not have been exhumed,weakening arguments for a Neoproterozoic onset of subduction and plate ***,isostatic balance calculations for more mafic Archean continents indicate that the early Earth was covered by a global ocean over 1 km deep,corroborating independent isotopic evidence for large-scale emergence of the continents no earlier than c.3 *** findings thus weaken arguments that early life on Earth likely emerged in shallow subaerial ponds,and instead support hypotheses involving development at hydrothermal vents in the deep ocean.

关键词： Archean eclogite Exhumation Secular change Geodynamics Density

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A subduction channel model for exhumation of oceanic-type high-pressure to ultrahigh-pressure eclogite-facies metamorphic rocks in SW Tianshan,China

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Science China Earth Sciences 2016年第12期59卷 2339-2354页

作者： LI JiLei GAO Jun WANG XinShui Key Laboratory of Mineral Resources Institute of Geology and GeophysicsChinese Academy of Sciences

High-pressure(HP) and ultrahigh-pressure(UHP) eclogites exposed in collisional orogens are widely regarded to record the history of crustal rocks that were subducted to mantle depths and exhumed back to the *** into subduction and exhumation processes plays an important role in understanding the nature and evolution of subduction zones,geodynamics and plate *** contrast to continental-type HP to UHP metamorphic rocks that are dominated by felsic lithology,oceanic-type HP to UHP metamorphic rocks are dominated by mafic eclogites and thus have greater density,and their exhumation needs to overcome large barriers and may involve complicated tectonic *** exhumation of HP to UHP rocks is mainly influenced by the internal buoyancy,however,the external tectonic forces(such as channel flow) also act as effective exhumation drivers;in addition,effects of tectonic settings(such as slab rollback and breakoff) should take into *** HP-UHP metamorphic terrane in Southwestern Tianshan,which mainly comprises of metasediments with interlayered metamafic lenses and blocks,represents a typical accretionary melange associated with deep subduction of oceanic ***,the exhumation mechanisms of these once deeply buried HP-UHP rocks are still under *** on the field occurrences,petrographic features,peak metamorphic P-T conditions and ages of the eclogites/blueschists and their metasedimentary country rocks,a "sediment-type subduction channel" model is advocated in this study to appraise/decipher the formation and evolution of Southwestern Tianshan HP-UHP metamorphic ***-cyclic metamorphic eclogites record the multistage burial-exhumation cycling manipulated by convective flow in a channel-like interface between the plates,giving robust evidence for the presence of a subduction *** addition,this study summarizes some remaining geotectonic problems and research perspectives concerning the Southwestern Tianshan HP-UHP me

关键词： eclogite High-pressure metamorphism Oceanic crust Exhumation Subduction channel Southwestern Tianshan

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First discovery of coesite in eclogite from East Kunlun, northwest China

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Science Bulletin 2018年第23期63卷 1536-1538页

作者： Hengzhe Bi Shuguang Song Jinlong Dong Liming Yang Shengsheng Qi Mark B.Allen MOE Key Laboratory of Orogenic Belt and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China Qinghai Bureau of Geological Survey Xining 810012China Department of Earth Sciences Durham UniversityDurham DH13LEUK

Ultrahigh-pressure (UHP)metamorphism plays important roles in continental *** of this process has been enhanced by the discovery of coesite and micro-diamond from supracrustal rocks [1].Such UHP mineral inclusions provide unequivocal evidence that the least dense part of the lithosphere can be buried to 100-150km or more,and then returned to the ***,an ultrahigh-pressure polymorph of SiO2stable above 2.7GPa at metamorphic temperatures,is one of the most important index minerals for UHP metamomhism [1,2].

关键词： Cobalt feldspar East Kunlun eclogite

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Electrical Conductivity of eclogite, Amphibolite and Garnet-Quartz-Mica Schist with Implications for the Conductivity in the Qiangtang Terrane of Northern Tibetan Plateau

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Journal of Earth Science 2020年第4期31卷 683-692页

作者： Yi Cao Xinzhuan Guo Jinxue Du State Key Laboratory of Geological Processes and Mineral Resources School of Earth SciencesChina University of GeosciencesWuhan 430074China Key Laboratory for High-Temperature and High-Pressure Study of the Earth's Interior Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China

Understanding the electrical conductivity of high pressure metamorphic rocks is essential to constrain the compositions in the subduction zone and continental crust. In this study, we calculated the electrical conductivity for such rocks sampled from the central Qiangtang metamorphic belt in the northern Tibetan Plateau. The results reveal that, when aqueous fluids are absent, the conductivity of meta-mafic rocks(e.g., eclogite and amphibolite) is strikingly higher than that of meta-felsic rocks(e.g., garnet-quartz-mica schist). The conductivity of eclogite decreases due to the enrichment of amphibole, but this effect is diminished when a critical degree of amphibolization is reached. Our calculated conductivity of eclogite and amphibolite differs greatly from the experimentally derived results for the eclogites from other localities, partly owing to the strong effects of different mineral assemblages and chemical compositions on the conduction mechanisms and efficiencies. However, the disparity of conductivity between our calculated and the previously measured results for a similar amphibole-rich eclogite sampled from the same locality suggests that trails of highly conductive rutile-ilmenite aggregates may contribute to the higher bulk-rock conductivity in the laboratory measurements. Moreover, since the calculated conductivity of eclogite and amphibolite is not high enough at the temperatures relevant to their metamorphic thermal condition, partial melts or aqueous fluids originated from the upwelling asthenosphere are more likely to explain the anomalously high electrical conductivity zones in magnetotelluric images in the Qiangtang terrane in the northern Tibetan Plateau.

关键词： electrical conductivity eclogite amphibolite felsic schist high pressure metamorphic rock

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Metamorphism and Oceanic Crust Exhumation——Constrained by the Jilang eclogite and Meta-Quartzite from the Sumdo (U) HP Metamorphic Belt

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Journal of Earth Science 2019年第3期30卷 510-524页

作者： Yang Li Cong Zhang Xiaoyu Liu Tingting Shen Tian Qiu Jingsui Yang School of Earth Science and Engineering Shandong University of Science and Technology Qingdao 266590 China Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources Institute of GeologyChinese Academy of Geological Sciences Beijing 100037 China National Research Center for Geoanalysis Beijing 100037 China

The Sumdo eclogite-bearing (U)HP metamorphic belt extends over 100 km across the middle part of the Lhasa terrane in southern Tibet, which forms a Permian-Triassic oceanic subduction zone between the south and the north Lhasa sub-terranes, leading to the reinterpretation of the tectonic evolution of the Lhasa terrane in the Tibetan-Himalayan orogeny. Previous studies show that there are significant differences in temperature and pressure conditions of the eclogites in four areas, e.g., Sumdo, Xindaduo, Bailang and Jilang areas. Studying the peak metamorphic P-T conditions and path of eclogite in the Sumdo belt is of great significance to reveal the subduction and exhumation mechanism of Paleo-Tethys Ocean in the Lhasa terrane. In this contribution, eclogite in the Jilang area of the Sumdo belt is chosen as an example to study its metamorphic evolution. The mineral assemblage of the eclogite is garnet, omphacite, phengite, hornblende, epidote, quartz and minor biotite. Garnet has a “dirty" core with abundant inclusions such as epidote, amphibole, plagioclase and a “clear" rim with few inclusions of omphacite and *** the core to the rim, pyrope content in garnet increases while grossular content decreases, showing typical growth zoning. The rim of garnet is wrapped by the pargasite+plagioclase corona, showing amphibolite facies overprint during retrogression. Three stages of metamorphism are inferred as (1) prograde stage, represented by the core of garnet and mineral inclusions therein;(2) peak stage, represented by the garnet rim, omphacite, lawsonite, phengite, and quartz;(3) retrograde stage characterized by decomposition of lawsonite to zoisite, followed by symplectite of omphacite and corona rimmed garnet. A P-T pseudosection contoured with isopleths of grossular and pyrope contents in garnet is used to constrain the near peak P-T condition at 2.85 GPa, 575 °C. In general, the Jilang eclogite shows a clockwise P-T path with a near isothermal decompress

关键词： Sumdo UHP belt eclogite metamorphic evolution oceanic crust exhumation

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Phase Equilibrium Modeling of Retrograded eclogite at the Kekesu Valley, Eastern Segment of SW Tianshan Orogen and Tectonic Implications

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Journal of Earth Science 2018年第5期29卷 1060-1073页

作者： Bin Xia Qin Yang Neng-Song Chen Zhiqiang Zhou School of Earth Sciences China University of Geosciences State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Center for Global Tectonics China University of Geosciences

In this study, we report newly found strongly retrograded eclogite blocks in the Kekesu Valley, eastern segment of southwestern Tianshan, northwestern China. Based on detailed petrographi- cal studies and mineral chemistry analyses, we constrain P-T evolution of two representative samples via phase equilibrium modeling method using THERMOCALC software. The peak stage is evidenced by the primary inclusions of omphacite＋glaucophane＋lawsonite （inferred）＋chlorite＋white mica in garnet. Using grossular and pyrope isopleth thermobarometry in garnet, the P peak conditions for this stage were con- strained to be -23 kbar, 480-500℃ and the T peak conditions were constrained to be 19-20 kbar, 500-520℃. Subsequent exhumation led to the transformation of lawsonite to epidote. Using Si-in- phengite barometry, the P was constrained to be 16-20 kbar at T of 500-520 ℃ for this stage. Further retrograde stage was evidenced by the mineral assemblages of glaucophane＋garnet＋epidote＋paragonite＋ chlorite＋white mica＋quartz. Later stage retrogression is evidenced by glaucophane＋epidote＋chlorite＋ quartz＋white mica＋albite＋aetinolite with P of 5-9 kbar when T〈490 ~C, indicating the eclogite may have been exhumed to the middle crust level and overprinted by blueschist-greenschist facies metamorphism. The results show that eclogite at the eastern segment of SW Tianshan shares similar P-T path to the HP rocks from the western segment, implying a similar P-T evolution for these rocks.

关键词： eclogite P-T path phase equilibria southwestern Tianshan Kekesu Valley.

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Subduction channel fluid-rock interaction:Indications from rutile-quartz veins within eclogite from the Yuka terrane,North Qaidam orogen

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Geoscience Frontiers 2020年第2期11卷 635-650页

作者： Xin Chen Youye Zheng Rongke Xu Pingyang Gu Jiyuan Yu Jie Bai Pengjie Cai Xiaojia Jiang State Key Laboratory of Geological Processes and Mineral Resources and Faculty of Earth ResourcesChina University of GeosciencesWuhan 430074China State Key Laboratory of Geological Processes and Mineral Resources and School of Earth Science and ResourcesChina University of GeosciencesBeijing 100083China Xi’an Center of Geological Survey Geological Survey of ChinaXi’an 710054China

High-pressure(HP)or ultrahigh-pressure(UHP)rutile-quartz veins that form at mantle depths due to fluid-rock interaction can be used to trace the properties and behavior of natural fluids in subduction *** explore the fluid flow and the associated element mobility during deep subduction and exhumation of the continental crust,we investigated the major and trace elements of Ti-rich ***,U–Pb dating,trace element contents,and Lu–Hf isotopic composition of zircon grains in the UHP eclogite and associated rutile-quartz veins were examined in the North Qaidam UHP metamorphic belt,Yuka *** zircon grains in the rutile-quartz veins have unzoned or weak oscillatory zonings,and show low Th/U ratios,steep chondrite-normalized patterns of heavy rare earth elements(HREEs),and insignificant negative Eu anomalies,indicating their growth in metamorphic *** zircon grains formed in 4313 Ma,which is consistent with the 4322 Ma age of the host *** for the zircons in the rutile-quartz veins,they showed steep HREE patterns on one hand,and were different from the zircons present in the host eclogite on the *** demonstrates that their formation might have been related to the breakdown of the early stage of garnet,which corresponds to the abundance of fluids during the early exhumation *** core-rim profile analyses of rutile recorded a two-stage rutile growth across a large rutile grain;the rutile core has higher Nb,Ta,W,and Zr contents and lower Nb/Ta ratios than the rim,indicating that the rutile domains grew in different metamorphic fluids from the core towards the *** significant enrichment of high field strength elements(HFSEs)in the rutile core suggests that the peak fluids have high solubility and transportation capacity of these ***,variations in the Nb *** trends in rutile indicate a connection of rutile to mafic *** zircon grains from both the rutile-quartz veins and the host eclogite have s

关键词： Quartz-rutile veins eclogite Fluid-rock interaction Fluid flow Yuka North Qaidam

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