Detrital Zircon Geochronology of Early Triassic Strata in the West Qinling Orogen:Implications for the Tectonic Evolution of the Paleo-Tethyan Ocean  

作　　者：Zuochen Li Xianzhi Pei Liyong Wei Guobing Liang Meng Wang Ruibao Li Lei Pei Chengjun Liu Youxin Chen Feng Gao 

机构地区：[1]Xi’an Key Laboratory for Mineralization and Efficient Utilization of Critical Metals,School of Earth Science and Resources,Chang’an University,Xi’an,710054,China [2]Xi’an Mineral Resources Survey Center,China Geological Survey,Xi’an,710100,China [3]School of Geology and Mining Engineering,Xinjiang University,Urumqi,830000,China

出　　处：《Journal of Earth Science》2024年第4期1087-1106,共20页地球科学学刊（英文版）

基　　金：supported financially by the National Nature Sciences Foundation of China(Nos.41872235,42172236,41872233,42072267,41802234,41602229 and 41502191);China Scholarship Council(No.201806565026);Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2019JM-312,2019JQ-090 and 2019JQ-209);China Geological Survey(Nos.12120114041201 and DD2016007901);China Postdoctoral Science Foundation(No.2016M592726);the Fundamental Research Funds for the Central Universities of China(Nos.300102270202,300103120009,202110710062,300103183081,300104282717,300102279204 and 201810710233).

摘　　要：The West Qinling Orogen(WQO)is located in the western part of the Qinling Orogen and in the transition zone of Qilian Orogen,Songpan-Garze Orogen and Yangtze Block,and also the key position of Triassic collision orogenic event.The study of the Early Triassic strata in the WQO is contributed to analyze the closure process of the paleo-Tethys.We conducted LA-ICP-MS U-Pb dating studies on detrital zircons to determine the provenance,depositional age,and tectonic setting of the Early Triassic Longwuhe Formation in the Lintan area of the WQO.The results show that the majority of the detrital zircons in the Longwuhe Formation are mainly magmatic origin and have characteristic of crust source zircon.The lowest limit of sedimentation of the Longwuhe Formation is constrained to the Early Triassic,with the youngest detrital zircon age of 253±3 Ma.The ages can be divided into five age groups:3346–1636 Ma,with two peak ages of ca.2495 and ca.1885 Ma;1585–1010 Ma,with a peak age at ca.1084 Ma;992–554 Ma,with a peak age at ca.939 Ma;521–421 Ma,with a peak age at ca.445 Ma;418–253 Ma,with a peak age at ca.280 Ma.Apparently,the sources of the Longwuhe Formation include the northern margin of the WQO,the Qilian Orogen(QLO)and the basement of the southern margin of the North China Block(NCB),of which the ancient basement of the southern margin of the NCB is the main source area of the Longwuhe Formation.Combined with previous studies,we propose that the Longwuhe Formation was formed in a fore-arc basin,which is related to the closure of the A’nyemaqen-Mianlüe Ocean from the Early Permian to Early–Middle Triassic due to the northward subduction-collision of the Yangtze Block(YZB).This also indicates that the A’nyemaqen-Mianlüe Ocean has flat subduction characteristics.

关 键 词：West Qinling orogenic belt Early Triassic paleo-Tethyan Ocean GEOCHRONOLOGY zircon 

分 类 号：P534.51[天文地球—古生物学与地层学] P542[天文地球—地质学] P597.3