Formation age and tectonic environment of the Gantaohe Group,North China Craton:Geology,geochemistry,SHRIMP zircon geochronology and Hf-Nd isotopic systematics

查看全文 作　　者：XIE [1,2]HangQiang;LIU [1,2]DunYi;YIN [3]XiaoYan;ZHOU [4]HongYing;YANG [1]ChongHui;DU [1]LiLin;WAN [1,2]YuSheng

机构地区：[1]Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;[2]Beijing SHRIMP Center, Chinese Academy of Geological Sciences, Beijing 100037, China;[3]Chinese Academy of Geological Sciences, Beijing 100037, China;[4]Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin 200170, China

出　　处：《Chinese Science Bulletin》索引2012年第57卷第36期,共11页

基　　金：supported by the China Geological Survey(1212010811033);the National Basic Research Program of China(2012CB416601) 摘　　要：The Gantaohe Group is an important early Precambrian unit in the Trans-North China Orogen,North China Craton,and is mainly composed of greenschist-facies metabasalt,meta-sandstone and dolomitic marble.We report whole-rock geochemical compositions and SHRIMP zircon ages as well as LA-ICP-MS Hf-in-zircon isotopeic analyses for metabasalts from the Gantaohe Group.SHRIMP dating yielded a weighted mean 207Pb/206Pb age of 2087±16 Ma(MSWD=1.3) for magmatic zircons,but there are also abundant ca.2.5 Ga inherited zircon xenocrysts.The magmatic zircons shows a large Hf(t) variation in Hf(t) from 7.17 to +0.45,suggesting an isotopically highly heterogeneous source for the metabasalt.Chemically all samples show no distinct Zr or Hf anomalies,and some samples show no Nd or Ta anomalies in a primitive mantle-normalized trace element variation diagram,and their whole-rock Nd(t) values range from 4.0 to 0.8.We suggest that the basalt is formed by partial melting of a depleted mantle source,followed by significant crustal contamination.Field observations,the presence of abundant inherited zircon,as well as isotope and trace elements geochemistry support formation of the Gantaohe Group on top of a continental basement.These data and the regional geology lead us to conclude that the Trans-North China Orogen constituted an intracontinental rift during the Paleoproterozoic that was connected to the Eastern Block since the end of the Archean. 关键词：微量元素地球化学 SHRIMP锆石年龄锆石年代学 ND同位素中国北方构造环境形成时代板块

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Formation age and tectonic environment of the Gantaohe Group,North China Craton:Geology,geochemistry,SHRIMP zircon geochronology and Hf-Nd isotopic systematics

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