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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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Metamorphic P-T Path Differences between the Two uhp Terranes of Sulu Orogen, Eastern China: Petrologic Comparison between Eclogites from Donghai and Rongcheng

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Journal of Earth Science 2018年第5期29卷 1151-1166页

作者： Zhuoyang Li Yilong Li Jan R.Wijbrans Qijun Yang Hua-Ning Qiu Fraukje M.Brouwer School of Earth Sciences State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Geology & Geochemistry Group Department of Earth Sciences VU Amsterdam College of Earth Sciences Guilin University of Technology Faculty of Earth Resources Key Laboratory of Tectonics and Petroleum Resources Ministry of Education China University of Geosciences

The Sulu Orogen constitutes the eastern part of the Sulu-Dabie Orogen formed by Triassic collision between the Sino-Korean and Yangtze plates. An HP Slice Ⅰ and two uhp slices Ⅱ and Ⅲ with contrasting subduction and exhumation histories within the Sulu Orogen were postulated. This study presents the metamorphic P-T paths of eclogites from the two uhp belts constructed by petrog- raphy, mineral chemistry and Perple_X P-T pseudosection modeling in the MnC（K）NFMASHO system. Eclogites from Slice Ⅲ mainly consist of omphacite, garnet and quartz, with minor rutile, ilmenite, amphibole and phengite. Eclogites from Slice Ⅱ show a porphyroblastic texture with epidote porphyroblasts and garnet, omphacite, phengite, quartz and rutile in matrix. Pseudosection modeling reveals that eclogites from Slice Ⅱ witness a peak metamorphism of eclogite-facies under conditions of 3.1-3.3 GPa and 660-690 ℃, and a retrograde cooling decompression process. The eclogites from Slice Ⅲ record a heating decompressive P-T path with a peak-P stage of 3.2 GPa and 840℃ and a peak-T stage of 2.4 GPa and 950 ℃, suggesting an apparent granulite-facies metamorphism overprint during exhumation. Both eclogites recorded clockwise P-T paths with peak P-T conditions suggesting a subduction beneath the Sino-Korean Plate to -100-105 km depth. Combined with tectonic scenarios from previous studies, it is concluded that the two uhp crustal slices in the Sulu terrane have a similar geodynamic evolution, but the uhp rocks in Slice Ⅱ exhumed after the eclogitic peak-pressure conditions earlier than that of Slice Ⅲ. The existence of Slice Ⅱ diminished the buoyancy force on Slice Ⅲ, resulting in a granulite-facies overprint on Slice Ⅲ. The Sulu orogenic belt is made up of different crustal slices that underwent different subduction and exhumation histories, rather than a single unit.

关键词： petrology uhp metamorphism exhumation process Sulu Orogen.

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Petrology of the Non-mafic uhp Metamorphic Rocks from a Drillhole in the Southern Sulu Orogenic Belt,Eastern-Central China

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Acta Geologica Sinica(English Edition) 2003年第2期77卷 173-186页

作者： ZHANG Zeming, XU Zhiqin and XU HuifenInstitute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Rd., Beijing 100037 E-mail: zzm@***. Chinese Acad Geol Sci Inst Geol Beijing 100037 Peoples R China

The Drillhole ZK703 with a depth of 558 m is located in the Donghai area of the southern Sulu ultrahigh-pressure (uhp) metamorphic belt, eastern China, and penetrates typical uhp eclogites and various non-mafic rocks, including peridotite, gneiss, schist and quartzite. Their protoliths include ultramafic, mafic, intermediate, intermediate-acidic, acidic igneous rocks and sediments. These rocks are intimately interlayered, which are meters to millimeters thick with sharp and nontectonic contacts, suggesting in-situ metamorphism under uhp eclogite facies conditions. The following petrologic features indicate that the non-mafic rocks have experienced early-stage uhp metamorphism together with the eclogites: (1) phengite relics in gneisses and schists contain a high content of Si, up to 3.52 p.f.u. (per formula unit), while amphibolite-facies phengites have considerably low Si content (<3.26 p.f.u.); (2) jadeite relics are found in quartzite and jadeitite; (3) various types of symplectitic coronas and pseud

关键词： uhp metamorphism non-mafic rock drillhole Dabie-Sulu orogenic belt eastern-central China

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Continental versus oceanic subduction zones

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National Science Review 2016年第4期3卷 495-519页

作者： Yong-Fei Zheng Yi-Xiang Chen CAS Key Laboratory of Crust-mantle Materials and Environments School of Earth and Space SciencesUniversity of Science and Technology of China

Subduction zones are tectonic expressions of convergent plate margins,where crustal rocks descend into and interact with the overlying mantle *** are the geodynamic system that produces maic arc volcanics above oceanic subduction zones but high-to ultrahigh-pressure metamorphic rocks in continental subduction *** the metamorphic rocks provide petrological records of orogenic processes when descending crustal rocks undergo dehydration and anataxis at forearc to subarc depths beneath the mantle wedge,the arc volcanics provide geochemical records of the mass transfer from the subducting slab to the mantle wedge in this period though the mantle wedge becomes partially melted at a later *** the mantle wedge overlying the subducting oceanic slab is of asthenospheric origin,that overlying the descending continental slab is of lithospheric origin,being ancient beneath cratons but juvenile beneath marginal *** either case,the mantle wedge base is cooled down during the slab–wedge coupled *** dehydration is prominent during subduction of crustal rocks,giving rise to aqueous solutions that are enriched in luid-mobile incompatible *** the subducting slab is decoupled from the mantle wedge,the slab–mantle interface is heated by lateral incursion of the asthenospheric mantle to allow dehydration melting of rocks in the descending slab surface and the metasomatized mantle wedge base,***,the tectonic regime of subduction zones changes in both time and space with respect to their structures,inputs,processes and *** record the tectonic conversion from sealoor spreading to oceanic subduction beneath continental margin,whereas ultrahigh-temperature metamorphic events mark the tectonic conversion from compression to extension in orogens.

关键词： subduction factory orogenic magmatism ophiolite uhp metamorphism UHT metamorphism

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Hydrogen and oxygen isotope studies of metamorphic fluid-rock interactions in the Dabie Mountains

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Science China Earth Sciences 1999年第1期42卷 61-71页

作者：傅斌郑永飞李一良肖益林龚冰 Department of Earth and Space Sciences University of Science and Technology of China Hefei China

Hydrogen and oxygen isotope studies were carried out on mineral separates from high to ultrahigh pressure metamorphic rocks at Huangzhen and Shuanghe in the eastern Dabie Mountains, East China. The δ18O values of eclogites cover a wide range of ?5‰ to+9‰, but the δD values of micas fall within a narrow range of ?85% to ?70‰. Both equilibrium and disequilibrium oxygen isotope fractionations were observed between quartz and the other minerals, with reversed fractionations between omphacite and garnet in some eclogite samples. The δ18 O values of ?5‰ to ?1‰ for some of the eclogites represent the oxygen isotope compositions of their protoliths which underwent meteoric water-rock interaction prior to plate subduction. The preservation of oxygen isotope heterogeneity in the eclogites implies a channelized flow of fluids during progressive metamorphism caused by rapid subduction. Retrograde metamorphism has caused oxygen and hydrogen isotope disequilibria between some of the minerals, but the fluid for retrograde reactions was internally buffered in the stable isotope compositions.

关键词： fluid-rock interactions hydrogen isotopes oxygen isotopes eclogites uhp metamorphism the Dabien Mountains

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Subduction of Continental Crust in the Early Palaeozoic North Qaidam Ultrahigh-Pressure Metamorphic Belt, NW China:Evidence from the Discovery of Coesite in the Belt

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Acta Geologica Sinica(English Edition) 2002年第1期76卷 63-68页

作者：杨经绥许志琴宋述光张建新吴才来史仁灯李海兵 Maurice BRUNEL Paul TAPPONNIER Institute of Geology Chinese Academy of Geological Science 26 Baiwanzhuang Rd. Beijing 100037 China Department of Earth Sciences University of Montpellier II Montpellier France Institut de Physique du Globe 75252 Paris Cedex 05 France

Coesite was discovered as inclusions in zircon separates from pelitic gneissassociated with a large eclogite body in the North Qaidam ultrahigh-pressure (uhp) terrane. Somegraphite inclusions were also found. This finding suggested the occurrence of in-situ uhpmetamorphism and that the terrane was most likely recrystallized at pressures below the diamondstability field. It supported other previous indirect uhp evidence, such as polycrystalline quartzinclusions in eclogitic garnet, quartz lamellae in omphacite and P-T estimates for both eclogite andgarnet peridotite. The U-Pb and Sm-Nd ages of the North Qaidam eclogite indicated that subductionof continental crust occurred in the Early Palaeozoic, which probably recorded a collision betweenthe Sino-Korean and Yangtze plates.

关键词： uhp metamorphism coesite eclogite Qinghai-Tibet plateau North QaidamMountains

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Exhumation P-T path of uhp eclogites in the Hong'an area,western Dabie Mountains,China

Exhumation P-T path of UHP eclogites in the Hong'an area,wes...

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中国科学院地质与地球物理研究所2006学术年会

作者： Jingbo Liu~a,Kai Ye~a,Min Sun~b a State Key Laboratory of Lithosphere Tectonic Evolution,Institute of Geology and Geophysics, Chinese Academy of Sciences,Beijing,100029,China b Department of Earth Sciences,The University of Hong Kong,Pokfulam Rd.,Hong Kong

Four generations of mineral assemblages have been identified in ultrahigh-pressure (uhp) eclogites from the Hong’an area,recording four metamorphic stages of the exhumation trajectory,i.e.,garnet+omphacite+kyanite+ zoisite/epidote+rutile+coesite formed at the uhp stage,garnet+omphacite+paragonite+phengite+amphibole+epidote+quartz at the high-pressure (HP) eclogitic stage,amphibole+epidote+albite-oligoclase+paragonite+quartz at the epidote-amphibolite facies(EA) stage,and actinolite+ albite and pumpellyite+albite+K-feldspar+muscovite+chlorite+margarite+epidote+quartz at the greenschist facies(GS) *** formed at the uhp stage was overgrown by atoll garnet at the HP stage. X-ray images,mineral compositions and compositional profiles indicate that the uhp garnet experienced a variable Fe-Mg modification in response to Fe-Mg exchange between garnet and omphacite prior to the overgrowth of atoll HP garnet.A volume diffusion zone was also observed between the uhp and HP *** following P-T conditions were estimated for these mineral assemblages:480 to 560℃and 2.5 to 2.9 GPa with median values of 520℃and 2.8 GPa at uhp stage,575 to 685℃and 1.6 to 1.9 GPa with the average results of 634±37℃and 1.8±0.06 GPa at the HP stage,500 to 640℃and 0.4 to 1 GPa at the EA stage,and 160 to 320℃and 0.2 to 0.8 GPa at the GS *** Hong’an uhp eclogites experienced a temperature increase of over 100℃from the uhp to HP stages and continued to exhume from the HP to EA stages through a process of approximately isothermal depression,which was followed by a significantly cooling from the EA to GS *** the process of exhumation,uhp eclogites witnessed a series of events involving fluid influx,resulting in the formation of hydrous minerals at different stages. The nature of fluids changed from K-rich at the HP stage to K-poor at the EA stage and then K-rich again at the GS stage.

关键词： uhp metamorphism Eclogite Coesite P-T path Exhumation The Dabie Mountains

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Multi-stage metamorphic evolution of eclogite in Younusisayi area of the South Altyn HP-uhp Belt, Northwest China

Multi-stage metamorphic evolution of eclogite in Younusisayi...

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2020年中国地球科学联合学术年会

作者： Ma Tuo Liu Liang Gai Yongsheng Northwest University

Eclogite with ultrahigh-pressure(uhp) metamorphic potential have been found for the first time in Younusisayi area of Southern Altyn continental high-pressure to ultra-high-pressure(HP-uhp) metamorphic belt, and studied using comprehensive petrology, mineral chemistry, phase equilibrium modeling and geochronology. It can be identified from metamorphic microstructures and mineralogical symbioses that the Phg-bearing eclogites underwent the early prograde(Grt±Mu+Cpx+Amp+Q+Ru), the peak uhp eclogite facies(Grt+Omp+Mu+Ru+Q), and three retrograde metamorphisms of HP granulite facies(Grt+Cpx±Ksp+Ru+Ilm+Q), granulite facies(Grt+Cpx±Amp+Pl±Bi+Q+Ilm), amphibolite facies(Amp+Pl±Bi+Q+Ilm), with peak condition of P>24.1～50.0 kbar, T=793～880℃ by calculations of P-T pseudosections. U-Pb dating and trace element analysis of zircons by LA-ICP-MS reveal that the peak metamorphic ages are 501.0±9.1 Ma, and retrograde age of 464.4±9.1 Ma, in accord with reported Jianggalesayi HP-uhp rocks in the western of Southern Altyn continental HP-uhp metamorphic belt. It defines the clockwise P-T-t paths, indicating the uhp and retrograde metamorphism associated with continental crust deep subduction-collision and exhumation. The uniform metamorphic evolution process of HP-uhp rocks in Younusisayi and western segment of South Altyn HP-uhp Belt, provide a further restriction on the to the spatial and temporal distributions of Early Paleozoic HP-uhp rocks in the South Altyn Tagh.

关键词： Phg-bearing eclogite uhp metamorphism Multi-stage retrograde P-T-t evolution South Altyn

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Petrogenesis of the Maowu pyroxenite-eclogite body from the uhp metamorphic terrane of Dabieshan:chemical and isotopic constraints

Petrogenesis of the Maowu pyroxenite-eclogite body from the ...

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中国科学院地质与地球物理研究所2003学术年会

作者： Bor-ming Jahn O.Henin Geosciences Rennes Universite de Rennes 1.CNRS-UPR 466135042 RennesFrance Geosciences Rennes Universite de Rennes 1CNRS-UPR 466135042 RennesFrance

The Maowu eclogite-pyroxenite body is a small(250×50 m) layered intrusion that occurs in the ultra-high-pressure(uhp) metamorphic terrane of Dabieshan,*** the adjacent Bixiling complex,the Maowu intrusion was initially emplaced at a crustal level,then subducted along with the country gneisses to mantle depths and underwent uhp metamorphism during the collision of the North and South China Blocks in the *** paper presents the results of a geochemical and isotopic investigation on the metamorphosed Maowu *** Maowu intrusion has undergone open system chemical and isotopic behavior three *** crustal contamination during magmatic differentiation is manifested by high initial Sr/Sr ratios (0.707-0.708) and inhomogeneous negativeε(T) values of -3 to - 10 at 500 Ma(probable protolith age).Post-magmatic and pre-uhp metamorphic metasomatism is indicated by sinusoidal REE patterns of garnet orthopyroxenites,lack of whole-rock (WR) Sm-Nd isochronal relationship,lowδO values and an extreme enrichment of Th and REE in a clinopyroxenite. Finally,K and Rb depletion during uhp metamorphism is deduced from the high initial Sr/Sr ratios unsupported by in situ Rb/Sr *** ICP-MS spot analyses on mineral grains show that(1) Grt and Cpx attained chemical equilibrium during uhp metamorphism,(2) Cpx/Grt partition coefficients for REE correlate with Ca,and(3) LREE abundances in whole rocks are not balanced by that of the principal phases(Grt and Cpx),implying that the presence of LREE-rich accessory phases,such as monazite and apatite,is required to account for the REE budget. Sm-Nd isotope analyses of minerals yielded three internal isochrons with ages of 221±5 Ma andε(T)= -5.4 for an eclogite,231±16 Ma andε(T)= - 6.2 for a garnet websterite,and 236±19 Ma andε(T) = - 6.9 for a garnet clinopyroxenite. The Cpx/Grt chemical equilibrium and the consistent mineral isochron ages indicate that the metasomatic processes mentioned above must have occurred prior

关键词： Dabieshan Maowu uhp metamorphism Eclogite Pyroxenite Sm-Nd isotopes Age

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Calculated Phase Relations in the System Na2O-CaO-K2O-FeO-MgO-Ai2O3-SiO2-H2O with Applications to uhp Eclogites and Whiteschists

Calculated Phase Relations in the System Na2O-CaO-K2O-FeO-Mg...

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中国科学院地质与地球物理研究所2006学术年会

作者： Roger Powell School of Earth Sciences The University of MelbourneParkvilleVictoria 3010MelbourneAustralia

Pressure-temperature grids in the system Na2O-CaO-K2O-FeO-MgO- Al2O3-SiO2-H2O and its subsystems have been calculated in the ranges of 15-45 kbar and 550-900℃,using an internally consistent thermodynamic dataset and new thermodynamic models for amphibole,white mica,and clinopyroxene,with the software THERMOCALC. Minerals considered for the grids include garnet,omphacite,diopside,jadeite,hornblende, actinolite,glaucophane,zoisite,lawsonite,kyanite,coesite,quartz,talc,muscovite,paragonite, biotite,chlorite,and *** diagrams are used to illustrate the phase relationships in the ***-bearing eclogites and a whiteschist from China are used to demonstrate the ability of pseudosections to model phase relationships in natural ultrahigh-pressure metamorphic *** water-saturated conditions,chlorite-bearing assemblages in Mg and Al-rich eclogites are stable at lower temperatures than in Fe-rich eclogites. The relative temperature stability of the three amphiboles is hornblende > actinolite > glaucophane (amphibole names used sensu lato).Talc-bearing assemblages are stable only at low temperature and high pressure in Mg and Al-rich *** most eclogite compositions,talc coexists with lawsonite,but not zoisite,in the stability field of *** content contouring of pressure-temperature pseudosections along with appropriate geotherms provides new constraints concerning dehydration of such rocks in subducting *** and lawsonite are two important H2O-carriers in subducting *** on bulk composition and pressure-temperature path,amphibole may or may not be a major H2O-carrier to *** most cases,dehydration to make ultrahigh-pressure eclogites takes place gradually,with H2O content controlled by divariant or higher variance ***,fluid fluxes in subduction zones are likely to be continuous,with the rate of dehydration changing with changing pressure and ***,eclogites of different

关键词： dehydration eclogites phase relations THERMOCALC uhp metamorphism whiteschists

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