Late Jurassic oceanic plateau subduction in the Bangong-Nujiang Tethyan Ocean of northern Tibet  

作　　者：Hao Wu Haiyong Liu Yu Wang Xijun Liu Qinggao Zeng Panxi Wang 

机构地区：[1]Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration&Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources on Guangxi,Guilin University of Technology,Guilin 541006,China [2]Tibet Geological Survey,Lhasa 850000,China [3]Tibet Bureau of Geological and Mineral Exploration and Development,Lhasa 850000,China

出　　处：《Geoscience Frontiers》2024年第4期274-289,共16页地学前缘（英文版）

基　　金：funded by the Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(Grant No.2019QZKK0702);National Natural Science Foundation of China(Grant Nos.92055208,42174080);Natural Science Foundation of Guangxi,China(Grant No.AD21220033);Shandong Provincial Natural Science Foundation(Grant No.ZR2020QD045);China Geological Survey(Grant No.DD20190167).

摘　　要：Oceanic plateau accretion and subsequent flat-slab subduction in modern convergent settings have profoundly influenced the nature of subduction and mantle dynamics.However,evaluating similar impacts in ancient convergent settings,where oceanic plateaus have been subducted but geological records are limited,remains challenging.In this study,we present geochronological and geochemical data for a suite of ore-associated plutonic rocks from the Gaobaoyue area of northern Tibet.These rocks have zircon U-Pb ages of 152-146 Ma,with high Sr contents and Sr/Y and La/Yb ratios,low MgO,Yb,and Y contents,and depleted Sr-Nd-Hf isotopic compositions,consistent with an adakitic affinity that was generated by the partial melting of subducting oceanic crust.We compare the Late Jurassic adakitic magmatism with the spatiotemporal evolution of magmatism in northern Tibet to infer oceanic plateau subduction and subsequent flat-slab subduction in the Bangong-Nujiang Tethyan Ocean.This tectonic model explains(ⅰ)slab-derived adakitic magmatism,(ⅱ)the observed lull in magmatic activity,(ⅲ)intraplate compression and uplift,and(ⅳ)subduction jump and initiation.We also propose that the subduction of heterogeneous oceanic crust(i.e.,buoyant oceanic plateau subduction)provided favorable conditions for tectonic exhumation,vertical slab tearing,and the formation of Cu-Au deposits.Our findings not only have implications for establishing the fundamental process of oceanic plateau accretion in ancient subduction zones but also provide an alternative explanation for Late Jurassic complex tectonomagmatic activity in north-ern Tibet.

关 键 词：Northern Tibet Adakitic magma Oceanic plateau Flat-slab subduction Vertical slab tearing 

分 类 号：P736[天文地球—海洋地质]