The A-type granites with highly positiveεNd(t) values in the West Junggar, Central Asian Orogenic Belt (CAOB), have long been perceived as a group formed under the same tectonic and geodynamic setting, magmatic sourceq and petrogenetic model. Geological evidence shows that these granites occurred at two different tectonic units related to the southeastern subduction of Junggar oceanic plate:the Hongshan and Karamay granites emplaced in the southeast of West Junggar in the Baogutu continental arc;whereas the Akebasitao and Miaoergou granites formed in the accretionary prism. Here the authors present new bulk-rock geochemistry and Sr-Nd isotopes, zircon U-Pb ages and Hf-O isotopes data on these granites. The granites in the Baogutu continental arc and accretionary prism contain similar zirconεHf(t) values (+10.9 to+16.2) and bulk-rock geochemical characteristics (high SiO2 and K2O contents, enriched LILEs (except Sr), depleted Sr, Ta and Ti, and negative anomalies in Ce and Eu). The Hongshan and Karamay granites in the Baogutu continental arc have older zircon U-Pb ages (315–305 Ma) and moderate 18O enrichments (δ18Ozircon=+6.41‰–+7.96‰);whereas the Akebasitao and Miaoergou granites in the accretionary prism have younger zircon U-Pb ages (305–301 Ma) with higher 18O enrichments (δ18Ozircon=+8.72‰–+9.89‰). The authors deduce that the elevated 18O enrichments of the Akebasitao and Miaoergou granites were probably inherited from low-temperature altered oceanic crusts. The Akebasitao and Miaoergou granites were originated from partial melting of low-temperature altered oceanic crusts with juvenile oceanic sediments below the accretionary prism. The Hongshan and Karamay granites were mainly derived from partial melting of basaltic juvenile lower crust with mixtures of potentially chemical weathered ancient crustal residues and mantle basaltic melt (induced by hot intruding mantle basaltic magma at the bottom of the Baogutu continental arc). On the other hand, the Miaoergou charnockite might be sourced from a deeper partial melting reservoir under the accretionary prism, consisting of the low-temperature altered oceanic crust, juvenile oceanic sediments, and mantle basaltic melt. These granites could be related to the asthenosphere's counterflow and upwelling, caused by the break-off and delamination of the subducted oceanic plate beneath the accretionary prism Baogutu continental arc in a post-collisional tectonic setting.

Chu Wu;Tao Hong;Xing-Wang Xud;Cheng-Xi Wang;Lian-Hui Dong

Development and Research Center of China Geological Survey,Ministry of Natural Resources,Beijing 100037,China;Guangdong Provincial Key Lab of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-sen University,Guangzhou 510275,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519082,China;Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China;Institutions of Earth Science,Chinese Academy of Sciences,Beijing 100029,China;Xinjiang Bureau of Geology and Mineral Resources,Urumqi,Xinjiang 830000,China

中国地质（英文）

[1]Chu Wu;Tao Hong;Xing-Wang Xud;Cheng-Xi Wang;Lian-Hui Dong-.A-type granites induced by a breaking-off and delamination of the subducted Junggar oceanic plate, West Junggar, Northwest China)[J].中国地质（英文）,2022(03):457-474

sourceq,Hongshan,Karamay,Baogutu,Akebasitao,Miaoergou,to+16,18Ozircon,charnockite,counterflow

type,granites,induced,by,breaking,off,delamination,subducted,Junggar,oceanic,plate,West,Northwest,China,highly,positive,Nd,values,Central,Asian,Orogenic,Belt,CAOB,have,long,been,perceived,group,formed,under,same,tectonic,geodynamic,setting,magmatic,petrogenetic,model,Geological,evidence,shows,that,these,occurred,two,different,units,related,southeastern,subduction,emplaced,continental,arc,whereas,accretionary,prism,Here,authors,present,new,bulk,rock,geochemistry,Sr,isotopes,Pb,ages,Hf,data,contain,similar,+10,geochemical,characteristics,SiO2,K2O,contents,enriched,LILEs,except,depleted,Ta,Ti,negative,anomalies,Eu,older,Ma,moderate,enrichments,+6,+7,younger,higher,+8,+9,deduce,elevated,were,probably,inherited,from,temperature,altered,crusts,originated,partial,melting,juvenile,sediments,below,mainly,derived,basaltic,lower,mixtures,potentially,weathered,ancient,crustal,residues,mantle,hot,intruding,bottom,On,other,hand,might,sourced,deeper,reservoir,consisting,These,could,asthenosphere,upwelling,caused,beneath,post,collisional

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