SS-LASS Zircon Dating Deciphering Multiple Episodes of Anatexis in a Deeply-Subducted Continental Crust:An Example from Sulu Orogen,China  

作　　者：Peng Feng Lu Wang Xiawen Li Wenjie Ding Zhe Chen 

机构地区：[1]School of Resource&Environment and Safety Engineering,University of South China,Hengyang 421001,China [2]State Key Laboratory of Geological Processes and Mineral Resources,Center for Global Tectonics,School of Earth Sciences,China University of Geosciences,Wuhan 430074,China [3]No.8 Institute of Geology and Mineral Resources Exploration of Shandong Province,Rizhao 276826,China

出　　处：《Journal of Earth Science》2024年第1期85-98,共14页地球科学学刊（英文版）

基　　金：supported by National Natural Science Foundation of China(Nos.42072228,42102060,41902036,41572182);China Postdoctoral Science Foundation(No.2021M692983);the Chinese Ministry of Education(No.BP0719022);the Most Special Fund(Nos.MSFGPMR02-3,MSFGPMR30);Open funds from the State Key Laboratory of Geological Processes and Mineral Resources;China University of Geosciences(Nos.GPMR201703,GPMR201704 and GPMR201903);the Fundamental Research Funds for National University(No.CUG-G1323511572)。

摘　　要：‘Single shot'laser-ablation split-stream(SS-LASS)technique analyzing unpolished zircon grains makes their thin rims tenable for determination,which thus offers great potential in deciphering the timing of multiple and short-lived episodes of anatexis and metamorphism in deeplysubducted continental crusts.Dominated granitic gneisses in the deeply subducted continental crust undergoing considerable fluid-melt activities persist multistage growth of zircon.Therefore,a comparative study of SS-LASS and laser ablation inductively coupled plasma mass spectrometer(LA-ICP-MS)zircon dating was conducted on the granitic gneisses from the Sulu belt in this study.Zircons mostly show a core-mantle-rim structure with CL-bright rims thinner than 5μm.For LA-ICP-MS dating,relict magmatic zircon cores yield protolith ages of ca.756-747 Ma;whereas the dark mantles record synexhumation anatexis at ca.214 Ma.By contrast,according to the U-Pb dates,trace element features,zircon crystallization temperatures and geological context,SS-LASS zircon petrochronology deciphers three episodes of anatectic events,as follows:(i)the first episode of anatexis at ca.218-217 Ma dominated by phengite-breakdown melting,likely facilitating the exhumation of the UHP slice from mantle depth;(ii)the second episode of anatexis at ca.193–191 Ma indicating part of northern Dabie-Sulu belt was still“hot”because of buried in the thickened orogenic crust at that time;(iii)the third episode of anatexis(ca.162–161 Ma)consistent with the intrusion ages(ca.161–141 Ma)of the Jurassic to Cretaceous granitoids in this orogen,suggesting the initial collapse of the orogenic root of the Sulu belt occurred at Late Jurassic due to the Izanagi plate initially subducting beneath the margin of Eastern Asia.This study sheds new light upon the utilization of SS-LASS petrochronology deciphering multiple anatectic events in the deeply-subducted continental crust and supports us in better understanding the tectonic evolution of Dabie-Sulu Orogen.

关 键 词：ANATEXIS laser ablation laser-ablation split-stream ultrahigh-pressure metamorphic belt Sulu Orogen 

分 类 号：P542[天文地球—构造地质学] P597.3[天文地球—地质学]