Beishan Complex in the Middle Section of Southern Central Asian Orogenic Belt:History,Progress and Problems

Wang Zhenyi; Zhang Jin; Wu Chunjiao; Zhang Beihang; Zhao Heng

doi:10.3799/dqkx.2024.014

Abstract：The Precambrian geological bodies in the orogenic belts are important for the division of tectonic units and also provide important information for understanding the amalgamation and fragmentation of early supercontinents.The understanding of their formation ages,distribution ranges,material compositions,etc.affects the view on the tectonics,evolution,and orogenic models of the different orogenic belts.It is the basis of many scientific issues and has important research values.However,due to structural deformation and replacement,it is difficult to differentiate some Phanerozoic and Precambrian geological bodies in ancient orogenic belts around the world.In addition,different research levels and testing methods in different periods have led to several changes in the classifications,nomenclatures,distribution ranges,and geotectonic attributes of some Precambrian geological bodies,affecting the understanding of the topics above.This study focuses on the Beishan Complex in the middle segment of the southern Central Asian Orogenic Belt(CAOB)to discuss the influence of the complicated and arbitrary classifications,divisions,and distribution of a Precambrian geological body on the tectonics and evolution of the orogenic belt.The Beishan Complex has long been regarded as the Precambrian basement of the microcontinents in the Beishan Orogenic Blet(BOB)in the middle section of the southern CAOB.In recent years,numerous advances have been made in its distribution ranges,ages,and basement affinities,which affect the tectonics and evolution of the BOB.This study reviews the classification history of the Beishan Complex,summarizes the previous views on the differences in the basement rocks between the southern and northern zones of the BOB,compares the Beishan Complex of the BOB with the Precambrian geological bodies of northern Alxa and the Central Tianshan blocks,and elaborates the understanding of the basement attribution of the tectonic units to which the Beishan Complex belongs.Based on the comprehensive comparison of rock assemblages,the Precambrian detrital zircon peak characteristics,magmatic event sequences,and zircon Hf isotope characteristics of the microcontinents in the middle section of the southern margin of the CAOB,it is considered that these microcontinents might experience a similar Precambrian evolution history.Integrated with previous data,it is proposed that these microcontinents may originate from the breakup of the Columbia Supercontinent,participate in the evolution of the Rodinia Supercontinent amalgamation,and finally break up into several microcontinent blocks.In view of the importance of geological bodies with Precambrian basement attributes and the various differences caused by the constantly changing connotation and distribution ranges,this paper calls for strengthening the research on the division and evolution of Precambrian geological bodies in the middle section of the southern CAOB and attaching importance to the compilation of regional geologic maps.