大别造山带红安地块康家湾构造混杂岩锆石U-Pb年龄和Hf同位素组成及其地质意义  

U-Pb ages and Hf isotope compositions of the zircons in the Kangjiawan mélange of the Hong’an block,Dabie orogenic belt and its geological implication

作　　者：童喜润[1,2] 陈伟雄 江拓 童铄云[1,2] 杨文武 彭旎 邱啸飞 TONG Xirun;CHEN Weixiong;JIANG Tuo;TONG Shuoyun;YANG Wenwu;PENG Ni;QIU Xiaofei(Wuhan Center of China Geological Survey,Wuhan,Hubei 430205,China;Central South China Innovation Center for Geosciences,Wuhan,Hubei 430205,China;Institute of Geological Survey,China University of Geosciences,Wuhan,Hubei 430074,China;School of Earth Sciences,Yunnan University,Kunming,Yunnan 650500,China)

机构地区：[1]中国地质调查局武汉地质调查中心,湖北武汉430205 [2]中南地质科技创新中心,湖北武汉430205 [3]中国地质大学(武汉)地质调查研究院,湖北武汉430074 [4]云南大学地球科学学院,云南昆明650500

出　　处：《地质学报》2023年第1期52-68,共17页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号42003017);中国地质调查局地质调查项目(编号DD20211391);中国地质调查局花岗岩成岩成矿地质研究中心开放基金(编号PMGR202017,PMGR202003)联合资助的成果。

摘　　要：扬子克拉通北缘中元古代—新元古代地质构造演化一直是地学界研究的热点。本文报道了大别造山带红安地块康家湾混杂岩中榴闪岩岩块和含石榴子石白云钠长片岩基质中锆石U-Pb年龄和Hf同位素组成。结果表明,康家湾混杂岩中榴闪岩岩块的原岩形成时间为1064±10 Ma,且经历了183±3 Ma的流体作用过程;中元古代锆石Hf同位素组成(εHf(t)=4.7~12.3)接近当时的亏损地幔值,指示榴闪岩原岩(玄武质岩石)可能来自亏损的地幔源区部分熔融作用;混杂基质中碎屑锆石年龄谱可大致分为2576 Ma、2065~1698 Ma、1071~560 Ma和254~156 Ma四组,暗示其物源可能主要来自于近源的秦岭-大别造山带前寒武纪基底;基质中最年轻的岩浆锆石年龄为~240 Ma,表明康家湾混杂岩的最终就位时间可能在晚三叠世到早侏罗世之间。综合秦岭-大别造山带新元古代构造演化过程,本研究认为大别造山带红安地块与扬子克拉通庙湾蛇绿岩、神农架弧等共同构成了一套中元古代末期—新元古代早期岛弧增生造山体系,从而支持扬子克拉通可能由一系列微陆块逐渐拼合而成。The Mesoproterozoic-Neoproterozoic tectonic evolution of the northern Yangtze Craton is of great significance to the Precambrian geological evolution of South China.Here the authors report U-Pb ages and Hf isotope compositions of the zircons in block(garnet-amphibolite)and matrix(metasedimentary rock)in the Kangjiawan mélange of the Hong’an block,western Dabie orogen.The results show that the garnet-amphibolite protolith was formed at 1064±10 Ma,and has undergone fluid overprinting at 183±3 Ma.The Hf isotope compositions(εHf(t)=4.7~12.3)of the zircons having the age of 1064 Ma in the garnet-amphibolite are close to the depleted mantle value,indicating that the garnet-amphibolite protolith(basaltic rock)may have been derived from partial melting of the depleted mantle.The U-Pb ages of detrital zircons in the metasedimentary rock cluster at:2576 Ma,2065~1698 Ma,1071~560 Ma and 254~156 Ma,suggesting that the provenances of the metasedimentary rock are mainly from the Early Precambrian basement of the nearby Qingling-Dabie orogenic belt.The youngest magmatic zircon in the metasedimentary rock has an age of~240 Ma,indicating that the final formation time of the Kangjiawan mélange may be between the Late Triassic and the Early Jurassic.Combined with the Neoproterozoic tectonic evolution process in the Qinling-Dabie orogenic belt,this study proposed that the Hong’an block in the Dabie orogenic belt,the Miaowan ophiolite and the Shennongjia arc in the Yangtze craton constitute the Late Mesoproterozoic-Early Neoproterozoic arc system,supporting the assumption that the Yangtze craton may have been gradually assembled from a series of microcontinents.

关 键 词：大别造山带 康家湾混杂岩 锆石 U-PB年龄 HF同位素 

分 类 号：P597.3[天文地球—地球化学]