Neoproterozoic Tectonic Evolution In The Southwest Margin Of Tarim And Its Control On Source Rocks

Neoproterozoic is an important period of global tectonic evolution,which experienced the assembly and breakup of Rodinia supercontinent,multi-stage volcanic activities,low latitude glaciation and global oxidation events.The Precambrian strata widely exposed in the southwest margin of Tarim plate provide the basis for the Neoproterozoic tectonic evolution and the reconstruction of Rodinia supercontinent.Thorough study is helpful to understand the structural pattern,sedimentary evolution and geomorphic characteristics of Southwest Tarim Basin during Nanhua–Sinian,besides,the research is of great significance for finding various mineral resources.Based on the comprehensive analysis of the field outcrop,drilling and seismic data,combined with the previous research results,this paper defines the sedimentary age,provenance characteristics,sedimentary background and structural affinity of the Qiakemakelieke group in the southwest Tarim.The maximum sedimentary age of the Qiakemakelieke group is preliminarily obtained,the source supply model of Nanhua system is established,the structural evolution model of Southwest Tarim is clarified,the position of Tarim plate in Rodinia supercontinent is restored,and the formation mechanism of Precambrian source rocks in Tarim Basin is preliminarily discussed.The purpose of this study is to clarify the tectonic evolution events of Tarim plate.Based on the analysis of 565 U-Pb concordance ages and HF isotopes,it is found that the Tarim Basin has Archean basement,and combined with the study of igneous rocks and other events,it is proved that the Tarim plate has undergone the same tectonic evolution as the Yangtze plate and the West Kunlun plate.The oldest age group 3000-2433 Ma represents the formation of crystalline basement of Tarim craton;2396-2076 Ma and 2006-1646 Ma zircons may be related to the aggregation and breakup of Columbia supercontinent respectively;the youngest age group 972-675 Ma corresponds to the aggregation or breakup of Rodinia supercontinent respectively.At the same time,the youngest zircon age of the Qiakemakelieke formation represents the largest sedimentary age of the Qiakemakelieke formation,with the largest peak age of 760ma.According to the petrogeochemical and sedimentary characteristics,it is suggested that there may be a passive continental margin environment in the late Neoproterozoic in Southwest Tarim.It is found that the provenance of the southwest margin of Tarim plate is bi-directional.The main provenance is the same as the Kudi bimodal volcanic rocks of the West Kunlun plate,while a small part is the ancient provenance which has been transported for a long distance and may come from the denudation products of the northern uplift in the Southwest of Tarim plate or outside the Tarim plate.In the analysis of the black mudstone in the southwest of Tarim,the source rock of kurkak formation is found for the first time.The TOC distribution range of the source rock is 0.14-1.62%,and the average value of R_O is 1.83.Under the influence of Rodinia,the late Neoproterozoic black mudstone is mainly controlled by rift development,glacial events and paleoenvironment.In addition,with the help of seismic data,the distribution of late Neoproterozoic black mudstone is predicted.