Detrital zircon constraints on late Paleozoic tectonism of the Bogda region(NW China)in the southern Central Asian Orogenic Belt  

作　　者：Qian Wang Guochun Zhao Yigui Han Jinlong Yao 

机构地区：[1]State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,229 Northern Taibai Road,Xi’an 710069,China [2]Department of Earth Sciences,The University of Hong Kong,Pokfulam Road,Hong Kong,China

出　　处：《Geoscience Frontiers》2020年第5期1533-1548,共16页地学前缘（英文版）

基　　金：financially supported by the National Key R&D Program of China(2017YFC0601205);National Natural Science Foundation of China(41730213 and 41190075);the Hong Kong Research Grants Council General Research Fund(grants 17307918 and 17301915);the Youth Program of Shaanxi Natural Science Foundation(2020JQ589)。

摘　　要：The Chinese North Tianshan(CNTS)in the southern part of the Central Asian Orogenic Belt(CAOB)has undergone multistage accretion-collision processes during Paleozoic time,which remain controversial.This study addresses this issue by tracing the provenance of Late Paleozoic sedimentary successions from the Bogda Mountain in the eastern CNTS through U-Pb dating and Lu-Hf isotopic analyses of detrital zircons.New detrital zircon U-Pb ages(N=519)from seven samples range from 261±4 Ma to 2827±32 Ma.The most prominent age peak is at 313 Ma and subordinate ages vary from 441 Ma to 601 Ma,with some Precambrian detrital zircon ages(~7%)lasting from 694 Ma to 1024 Ma.The youngest age components in each sample yielded weighted mean ages ranging from 272±9 Ma to 288±5 Ma,representing the maximum depositional ages.These and literature data indicate that some previously-assumed"Carboniferous"strata in the Bogda area were deposited in the Early Permian,including the Qijiaojing,Julideneng,Shaleisaierke,Yangbulake,Shamaershayi,Liushugou,Qijiagou,and Aoertu formations.The low maturity of the sandstones,zircon morphology and provenance analyses indicate a proximal sedimentation probably sourced from the East Junggar Arc and the Harlik-Dananhu Arc in the CNTS.The minor Precambrian detrital zircons are interpreted as recycled materials from the older strata in the Harlik-Dananhu Arc.Zircon EHf(t)values have increased since^408 Ma,probably reflecting a tectonic transition from regional compression to extension.This event might correspond to the opening of the Bogda intraarc/back arc rift basin,possibly resulting from a slab rollback during the northward subduction of the North Tianshan Ocean.A decrease of zirconεHf(t)values at^300 Ma was likely caused by the cessation of oceanic subduction and subsequent collision,which implies that the North Tianshan Ocean closed at the end of the Late Carboniferous.

关 键 词：North Tianshan Detrital zircon Sedimentary provenance Late Paleozoic Central Asian orogenic belt 

分 类 号：P534.4[天文地球—古生物学与地层学] P597.3[天文地球—地质学] P542