Lower Cretaceous turbidites in the Shiquanhe–Namco Ophiolite Mélange Zone, Asa area, Tibet: Constraints on the evolution of the Meso-Tethys Ocean  

作　　者：Xiao-Wen Zeng Ming Wang Cai Li Hang Li Xian-Jin Zeng Di Shen 

机构地区：[1]College of Earth Sciences,Jilin University,Changchun 130062,China [2]Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources of China,Changchun 130062,China

出　　处：《Geoscience Frontiers》2021年第4期1-20,共20页地学前缘（英文版）

基　　金：by the National Natural Science Foundation of China(Grant No.41402190 and 41602230);the Program of China Geological Survey(Grant No.121201010000150014 and DD20160026);Opening Foundation of Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources(DBY-ZZ-18-06).

摘　　要：Turbidites fromthe Shiquanhe–Namco OphioliteMélange Zone(SNMZ)record critical information about the tectonic affinity of the SNMZand the evolutionary history of theMeso-Tethys Ocean in Tibet.This paper reports sedimentologic,sandstone petrographic,zircon U-Pb geochronologic,and clastic rocks geochemical data of newly identified turbidites(Asa Formation)in the Asa Ophiolite Mélange.The youngest ages of detrital zircon from the turbiditic sandstone samples,together with~115 Ma U-Pb concordant age from the tuff intercalation within the Asa Formation indicate an Early Cretaceous age.The sandstone mineral modal composition data show that the main component is quartz grains and the minor components are sedimentary and volcanic fragments,suggesting that the turbidites were mainly derived froma recycled orogen provenancewith a minor addition of volcanic arc materials.The detrital U-Pb zircon ages of turbiditic sandstones yield main age populations of 170–120 Ma,300–220 Ma,600–500 Ma,1000–700 Ma,1900–1500 Ma,and~2500 Ma,similar to the ages of the Qiangtang Terrane(age peak of 600–500 Ma,1000–900 Ma,~1850 Ma and~2500 Ma)and the accretionary complex in the Bangong–Nujiang Ophiolite Zone(BNMZ)rather than the age of the Central Lhasa Terrane(age peak of~300 Ma,~550 Ma and~1150 Ma).The mineral modal compositions,detrital U-Pb zircon ages,and geochemical data of clastic rocks suggest that the Asa Formation is composed of sediments primarily recycled from the Jurassic accretionary complex within the BNMZ with the secondary addition of intermediate-felsic island arc materials from the South Qiangtang Terrane.Based on our new results and previous studies,we infer that the SNMZ represents a part of the Meso-Tethys Suture Zone,rather than a southward tectonic klippe of the BNMZ or an isolated ophiolitic mélange zone within the Lhasa Terrane.The Meso-Tethys Suture Zone records the continuous evolutionary history of the northward subduction,accretion,arc-Lhasa collision,and Lhasa-Qiangtang collision of the Meso-Te

关 键 词：TIBET Shiquanhe–Namco Ophiolite Mélange Zone Early Cretaceous Sedimentary provenance Tectonic Affinity Meso-Tethys Ocean 

分 类 号：P534.53[天文地球—古生物学与地层学]