Chronology And Structural Properties Of Late Precambrian Stratigraphic In The Southern Margin Of The Eastern Jiangnan Orogenic Belt

The southern margin of the eastern Jiangnan Orogenic Belt, which is the assembly of the Upper Yangtze Block and Cathaysia Block, and also impact by the Shengong Movement and the late movements, its geological structure is complex, the late Precambrian stratigraphic in this area is diversity and isolated, the research of geochronology and tectonic evolution of this area is significant to the study of the Jiangnan Orogenic Belt, and even the assembly and evolution of the Upper Yangtze Block and Cathaysia Block. Thus, the paper is dedicated to find out the age of stratigraphic, tectonic attribute, and make the contrast between late Precambrian strata in the southern margin of the eastern Jiangnan Orogenic Belt, including the Tieshajie Formation and the Chencai Group to the south of the Jiangshao Fault, the Wenjialing Formation, the "Zhangcun Formation", the Shuangxiwu Group, and the Luojiamen Formation to the north of the Jiangshao Fault.In the framework of the geochronology and basis of petrology, the sedimentology, geochemistry and isotopic dating were employed to study the isotopic data, age contrast, and tectonic attribute of late Precambrian stratigraphic in the southern margin of the eastern Jiangnan Orogenic Belt in this thesis. Combined the field investigation and the experimental measurement with the results of other geologists, this paper has a comprehensive understanding of the isotopic data, age contrast, and tectonic attribute of late Precambrian stratigraphic in this area. The main conclusions and innovativeresults were listed as follows:Zircon SHRIMP U-Pb dating of quartz keratophyre is first time to report from the Tieshajie Formaion (1154±5Ma), it is the late Proterozoic strata. Synthetically analyze the stratigraphic age, geochemical characteristics, and zircon Hf isotopes, the Tieshajie Formaion formed in a continental intraplate setting, postorogenic stage. It may be formed in cracking stage of intraplate rift of the Cathaysia Block, and products of mantle material upwelling.Zircon SHRIMP U-Pb dating of tuff bedding is first time to report from the Wengjialing Formation in the east section of the Jiangnan Orogenic Belt in Northeast Jiangxi Province (841±5Ma), the stratigraphic age is defined, it is a strata under the Taoyuan Formation and equivalent strata with the Fanjingshan, the Sibao, the Lengjiaxi, and the Shuangqiaoshan groups.Zircon SHRIMP U-Pb dating of tuff bedding is821±7Ma and832±8Ma from the "Zhangcun Formation" in the West of Zhejiang Province, which is belongs to late Neoproterozoic. The "Zhangcun Formation" is equivalent with the Taoyuan Formation overlying the Wengjialing Formation, the igneous plutons which intruded into the Fanjingshan, the Sibao, the Lengjiaxi, the Shuangqiaoshan groups, also occurred simultaneously with the "Pingshui Group" in Pujiang County, Zheijiang Province. At820-830Ma, a magma event was widely developed from west to east in the Jiangnan Orogenic Belt.The age of the Shuangxiwu Group is of about877Ma to926Ma. The age of the Luojiamen Formation which is an angle unconformity overlying on the Shuangxiwu Group, gains isotopic data of824Ma to855Ma, it is a strata equivalent with the Fanjingshan, the Sibao, the Lengjiaxi, and the Shuangqiaoshan Groups. Thus, these could limit the age range of the Shengong Movement. The Shengong Movement is earlier than the Wuling Movement.Through summarizing the studying results of other geologists on the Jiangnan Orogenic Belt, the latest high precise isotope geochronology data and tectonic attribute attained by this thesis, the late Proterozoic to Pre-Nanhua system tectonic evolution pattern of eastern segment of the Jiangnan Orogenic Belt was built.