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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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Tectonic Evolution of an Early Precambrian high-pressure Granulite Belt in the North China Craton

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Acta Geologica Sinica(English Edition) 2000年第2期74卷 246-258页

作者： Alfred KRONER P.O.BRIEN Institut fuer Geowissenschaften Universitaet Mainz 55099 Mainz GermanyBayerisches Geoinstitut Universitat Bayreuth 95440 Bayreuth Germany

A large-scale high-pressure granulite belt (HPGB), more than 700 km long, is recognized within the metamorphic basement of the North China craton. In the regional tectonic framework, the Hengshan-Chengde HPGB is located in the central collision belt between the western block and eastern block, and represents the deep crustal structural level. The typical high-pressure granulite (HPG) outcrops are distributed in the Hengshan and Chengde areas. HPGs commonly occur as mafic xenoliths within ductile shear zones, and underwent multipile deformations. To the south, the Hengshan-Chengde HPGB is juxtaposed with the Wutai greenstone belt by several strike-slip shear zones. Preliminary isotopic age dating indicates that HPGs from North China were mainly generated at the end of the Neoarchaean, assocaited with tectonic assembly of the western and eastern blocks.

关键词： North China craton high-pressure metamorphism collision belt Neoarchaean

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Exhumation of deeply subducted crust:Review and outlook

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Science China Earth Sciences 2020年第12期63卷 1904-1924页

作者： Yican Liu Chengwei Zhang CAS Key Laboratory of Crust-Mantle Materials and Environments School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei230026China

The discovery of ultrahigh-pressure(UHP)index minerals such as coesite and micro-diamond in supracrustal rocks indicate that a large amount of crustal rocks were subducted to mantle depths and subsequently returned to the Earth’s ***,exhumation mechanism of the deeply subducted crustal rocks has been a hot topic in geodynamic community and remains *** studies have been performed by petrologic observations,analogue experiments and numerical simulations for exhumation processes and mechanisms of deeply subducted crustal rocks,and a series of important results have been *** this paper,we summerize in detail recent progresses and existing problems on types of subduction zones,exhumation processes and mechanisms of deeply subducted crustal rocks,and related *** on these,three forthcoming prospects are presented:(1)The geological processes within the exhuming crust;(2)the interaction between the exhuming crust and the surface process;(3)the interaction between the exhuming crust and the mantle.

关键词： Subduction zone high-pressure metamorphism Ultrahigh-pressure metamorphism Exhumation of subducted crust Crustal detachment Metamorphic P-T-t path

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40Ar-39Ar Geochronology and Tectonic Implications of the Blueschist from Northwestern Qiangtang, Northern Tibet, Western China

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Acta Geologica Sinica(English Edition) 2012年第6期86卷 1471-1478页

作者： TANG Xianchun ZHANG Kaijun Guangzhou Institute of Geochemistry Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences Research Institute of Petroleum Exploration and Development East China CompanySINOPEC Asian Tectonics Research Group Department of Earth SciencesNanjing University

Blueschist exposed in the northwestern Qiangtang terrane, northern Tibet, western China （84 30＇ E, 34024＇ N）, provides new constraints on the tectonic evolution of Qiangtang as well as northern Tibet. The blueschist represented by lawsonite- and glaucophane-bearing assemblages equilibrated at 375-400 C and 11 kbar. 4Ar-39Ar analysis on mineral separate from one blueschist sample yielded a well-defined plateau age of 242 Ma. Geochemical studies show the blueschist is metamorphosed within-plate basalts. The high pressure-low temperature blueschist indicates a Triassic event of lithosphere subduction, and clearly represents an extension of the central Qiangtang metamorphic belt, and defines an in situ suture between eastern and western Qiangtang.

关键词： blueschist high-pressure metamorphism 40Ar-39Ar geochronology Qiangtang Tibet

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Compressional origin of the Aegean Orogeny,Greece

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Geoscience Frontiers 2022年第2期13卷 383-404页

作者： Michael P.Searle Thomas N.Lamont Dept Earth Sciences Oxford UniversitySouth Parks RoadOxfordOX13ANUK School of Earth and Environmental Sciences University of St AndrewsSt AndrewsKY169ALUK

The Aegean Sea area is thought to be an actively extending back-arc region,north of the present day Hellenic volcanic arc and north-dipping subduction zone in the Eastern *** area shows extensive normal faulting,ductile‘extensional’shear zones and extensional S-C fabrics throughout the islands that have previously been related to regional Aegean extension associated with slab rollback on the Hellenic Subduction *** this paper,we question this interpretation,and suggest the Cenozoic geodynamic evolution of the Aegean region is associated with a Late Cretaceous-Eocene NE-dipping subduction zone that was responsible for continentcontinent collision between Eurasia and Adria-Apulia/*** of eclogite and blueschist facies rocks in the Cyclades and kyanite-sillimanite grade gneisses in the Naxos core complex have pressures that are far greater than could be accounted for purely by lithospheric extension and isostatic *** identify four stages of crustal shortening that affected the region prior to regional lithospheric extension,herein called the Aegean *** orogeny followed a classic Wilson cycle from early ophiolite obduction(ca.74 Ma)onto a previously passive continental margin,to attempted crustal subduction with HP eclogite and blueschist facies metamorphism(ca.54-45 Ma),through crustal thickening and regional kyanite-sillimanite grade Barroviantype metamorphism(ca.22-14 Ma),to orogenic collapse(<14 Ma).At least three periods of‘extensional’fabrics relate to:(1)Exhumation of blueschists and eclogite facies rocks showing tight-isoclinal folds and top-NE,base-SW fabrics,recording return flow along a subduction channel in a compressional tectonic setting(ca.50-35 Ma).(2)Extensional fabrics within the core complexes formed by exhumation of kyanite-and sillimanite gneisses showing thrust-related fabrics at the base and‘extensional’fabrics along the top(ca.18.5-14 Ma).(3)Regional ductile-brittle‘extensional’fabrics and low-angle

关键词： Cyclades Ophiolite high-pressure metamorphism Core complex Compressional tectonics

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U-Pb zircon geochronology of Tianshan eclogites in NW China:implication for the collision between the Yili and Tarim blocks of the southwestern Altaids

U-Pb zircon geochronology of Tianshan eclogites in NW China:...

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中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： REINER KLEMD GeoZentrum Nordbayern Universitat ErlangenSchlossgarten 5a91054 ErlangenGermany

Zircon grains separated from an eclogite boudin intercalated within blueschists in Tianshan(NW China) were investigated by Raman spectroscopy,cathodoluminescence imaging and secondary ion mass spectrometry(SIMS).These grains have a thin homogeneous rim and an oscillatory inner zone domain with or without a relict inherited ***,phengite and rutile inclusions were identified within the rim domain of zircon grains only,indicating that the rim had formed during peak eclogite-facies metamorphism. U-Pb zircon data record three distinct age populations:2450±31 to 1956±26 Ma(for the inherited core),486±8 to 428±6 Ma (oscillatory inner zone) as well as 319.5±2.9 Ma and 318.7±3.3 Ma(for the metamorphic rim).These new ages suggest that the metamorphism associated with the collision of the Yili and the Tarim blocks along the southwestern margin of the Altaids must have occurred during the Late Carboniferous(ca.,320 Ma).

关键词： eclogite U-Pb zircon age collision time high-pressure metamorphism Tianshan

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Geochemistry and U–Pb zircon dating of the Toudaoqiao blueschists in the Great Xing'an Range, NE China, and tectonic implications

Geochemistry and U–Pb zircon dating of the Toudaoqiao blues...

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2014年中国地球科学联合学术年会——专题45：中亚-兴蒙造山带

作者： Bin Wang Jian-Bo Zhou Jia-Lin Cao College of Earth Sciences Jilin University

The Toudaoqiao Complex is a sequence of high-pressure metamorphic rocks located along the suture zone that separates the Xing’an and Erguna blocks in northeast China. The rocks were metamorphosed up to epidote-blueschist facies at P-T conditions of approximately 0.9-1.1 GPa and 320-450℃. Lithological associations and major and trace element compositions indicate that the blueschists are metabasalts with ocean island basalt(OIB) and normal mid-ocean ridge basalt(N-MORB) affinities, similar to those of the Philippines intraoceanic accretionary complex formed by subduction of oceanic crust. Magmatic zircons extracted from two samples of the epidote-blueschist facies metabasalts from the North Mountain in the Toudaoqiao Complex exhibit 206Pb/238 U ages of 511 ± 5 and 516 ± 17 Ma, whereas a greenschist from the South Mountain has a 206Pb/238 U age of 511 ± 2 Ma;These data show that the protoliths of the Toudaoqiao Complex are of early Paleozoic age. In addition, a granitic dike from the South Mountain exhibits a weighted mean 206Pb/238 U age of 492 ± 1 Ma. These ages constrain the timing of high-pressure metamorphism in the Toudaoqiao Complex to 490-510 Ma. The new data support the view that the suture zone between the Xing’an and Erguna blocks is the Toudaoqiao-Xinlin Fault, rather than the Derbugan Fault as previously thought. This suture, which extends from Xinlin, through Toudaoqiao, and southern Mongolia, named the ‘South Mongolia-Toudaoqiao-Xinlin Suture Zone’, may be an important boundary between the Central Mongolia-Erguna and Xing’an blocks.

关键词： LA-ICPMS U-Pb zircon dating Toudaoqiao blueschist high-pressure metamorphism early Paleozoic Central Asian Orogenic Belt

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Exact timing of granulite metamorphism in the Namche-Barwa,eastern Himalayan syntaxis:new constrains from SIMS U-Pb zircon age

Exact timing of granulite metamorphism in the Namche-Barwa,e...

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中国科学院地质与地球物理研究所2012年度（第12届）学术年会

作者： Wen Su Ming Zhang Xiaohan Liu Jinfu Lin Kai Ye Xin Liu State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences Department of Earth Sciences University of CambridgeCambridgeUK Institute of Tibetan Plateau Research Chinese Academy of Sciences Engineering Research Center of Exploration for Hidden Non-Ferrous and Precious Metal Ore Deposits Ministry of EducationGuilin University of Technology

Zircon grains separated from 2 granulites from the eastern Himalaya were investigated by Raman spectroscopy, cathodoluminescence imaging,and secondary ion mass *** grains have a thin homogeneous rim and an oscillatory inner zone domain with or without a relict inherited ***,kyanite,and rutile inclusions were identified within only the rim domain of zircon grains,indicating that the rim had formed during peak granulite-facies metamorphism.U-Pb zircon data record three distinct age populations:1,805 Ma(for the inherited core),ca.500 Ma(oscillatory inner zone),as well as 24-25 Ma and ca.18 Ma(for the metamorphic rim).These new precision ages suggest that the peak metamorphic age for the HP granulite is at ca.24-25 Ma,and subsequent amphibolite-facies retrograde metamorphism occurred at ca.18 Ma.

关键词： Granulite SIMS U-Pb zircon age high-pressure metamorphism Himalaya

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