| Located in the Shuangxiwu area of the Zhejiang,Heshangzhen group,the aera of research,sedimentary facies and tectonic background has many views.Especially ancient geography of the Heshangzhen group,Hongchicun formation and stratum is shallow.Therefore,in order to check the relationship between time and space of the Heshangzhen group,according to the previous data and research results,Heshangzhen group community using stratigraphy,geochronology and geochemistry method and considering the features of prototype basin,therefore draws the following conclusions:1.redefined the years of sedimentary Luojiamen formation eastern section of the Jiangnan orogenic belt,obtain luojiamen formation bottom tuff zircon SHRIMP U-Pb age of 868Ma±6.4Ma,determine the Luojiamen formation sedimentary age of late Neoproterozoic,Luojiamen formation and Lengjiaxi group,Sibao group,Fanjingshan group are the same age stratum;2.determine the zircon SHRIMP U-Pb age of Zhitang bottom formation the upper strata is 784±7Ma and the upper strata is 773.6±5.7Ma,and then from the chronology of limiting the formation time,and compared Hongchicun and shangshu formation together with the formation of Banxi group,Danzhou group,Xiajiang group formation;3.according to the geochemical analysis,Luojiamen formation is the ocean continent subduction stage of back arc basin sedimentary strata,and Hongchicun formation,"Zhitang formation" is the post orogenic continental breakup sedimentary strata,as continental volcano rock in shallow sea sedimentary sequence;4.Since the group is formed by two or more formations with two or more adjacent lithologic features in the longitudinal direction,and the Luojiamen formation is incontact with the Hongchicun formation and the upper strata,and belongs to two completely different tectonical systems,So the original Heshangzhen group lost the meaning of the group,it should be abandoned. |
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