Multiple Episodes of Zircon Growth during Anatectic Metamorphism of Metasedimentary Rocks in Collisional Orogens:Constraints from Felsic Granulites in the Bohemian Massif  

作　　者：Guang Yang Ren-Xu Chen Yong-Fei Zheng Qiong-Xia Xia Yong-Jie Yu Kun Li Zhaochu Hu Bing Gong Xiang-Ping Zha 

机构地区：[1]CAS Key Laboratory of Crust-Mantle Materials and Environments,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China [2]Center of Excellence for Comparative Planetology,Chinese Academy of Sciences(CAS),Hefei 230026,China [3]Frontiers Science Center for Planetary Exploration and Emerging Technologies,University of Science and Technology of China,Hefei 230026,China [4]State Key Laboratory of Geological Processes and Mineral Resources,Faculty of Materials Science and Chemistry,China University of Geosciences,Wuhan 430078,China

出　　处：《Journal of Earth Science》2023年第3期609-639,共31页地球科学学刊（英文版）

基　　金：supported by the Natural Science Foundation of China(Nos.41673030,41590624);the Strategy Guide Project B of the Chinese Academy of Sciences(No.XDB18020303);the Youth Innovation Promotion Association of CAS(No.2013283);the Fundamental Research Programs for the Central Universities。

摘　　要：Zircon is a key accessary mineral for metamorphic geochronology and geochemical tracing,but it has been a challenge to interpret its complex chemical zoning and age record acquired during multiple episodes of anatectic metamorphism in collisional orogens.This is illustrated by a combined study of petrography,phase equilibrium modeling and metamorphic P-T-t determination for granulites from the Bohemian Massif in the Variscan Orogen.These rocks record multiple episodes of zircon growth during anatectic metamorphism.They started from the compressional heating for prograde metamorphism to high-pressure(HP)to ultrahigh-pressure(UHP)eclogite facies with low degrees of partial melting.Afterwards,they underwent a decompressional stage from UHP eclogite facies to HP granulite facies for dehydration melting.These were followed by a further decompressional stage either to kyanite granulite facies or to sillimanite granulite facies at ultrahigh-temperature(UHT)conditions.Episodes of zircon growth are linked to specific metamorphic conditions for peritectic reactions on the basis of zoning patterns,trace element signatures,index mineral inclusions in dated domains and textural relationships to coexisting minerals.The results indicate that relict zircon domains are preserved even at UHT granulite facies conditions.A few zircon domains in the kyanite granulite grew during the prograde to peak UHP metamorphism,possibly corresponding to consumption of biotite and plagioclase but growth of garnet.During the decompressional exhumation to the HP granulite-facies,relict or prograde zircon domains were mostly dissolved into anatectic melts produced by muscovite breakdown.Most zircon grains grew during this transition to the HP granulite-facies in the kyanite granulite and are chemically related to continuous growth of garnet,whereas abundant zircon grains grew subsequently at the UHT granulite facies in the sillimanite granulite and are chemically related to garnet breakdown reactions.Another peak of zircon growth occurred at the fin

关 键 词：ultrahigh-pressure metamorphism ultrahigh-temperature metamorphism felsic granulite ZIRCON continental collision crustal anataxis 

分 类 号：P542.2[天文地球—构造地质学] P588.3[天文地球—地质学]