Origin and Emplacement of the Cambrian Yanglong Ophiolite in the North Qilian Suture  

作　　者：FU Changlei XUE Wanwen PAN Tong YAN Zhen GUO Xianqing Jonathan C.AITCHISON XIAO Wenjiao WANG Bingzhang LI Wufu 

机构地区：[1]State Key Laboratory of Deep Earth and Mineral Exploration,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China [2]Key Laboratory of the Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources,Qinghai Geological Survey Institute,Xi’ning 810012,China [3]Bureau of Geological Exploration and Development of Qinghai Province,Xi’ning 810008,China [4]Chinese Academy of Geological Sciences,Beijing 100037,China [5]School of Earth and Environmental Sciences,University of Queensland,Brisbane 4072,Australia [6]Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Urumqi 830011,China

出　　处：《Acta Geologica Sinica(English Edition)》2025年第2期409-424,共16页地质学报(英文版)

基　　金：the National Natural Science Foundation of China(Grant Nos.42230308,42072266,42102032,42362006);Bureau of Geological Exploration and Development of Qinghai Province(Grant Nos.[2023]33,[2022]32);China Geological Survey(Grant Nos.DD20221649,DD20242935,12120114079701).

摘　　要：Fragments of Proto-Tethyan oceanic lithosphere are well-preserved along the southern belt of the North Qilian suture,and the origin and emplacement of these ophiolites have become subjects of intense debate.In this study,we integrate field observations,mineralogical and geochemical analyses,zircon U-Pb dating,and isotopic data to investigate the Yanglong ophiolite.The Yanglong ophiolitic rocks are found as tectonic slices resting on the Neoproterozoic sedimentary and volcanic rocks.These rocks are composed of Cambrian serpentinized peridotite,gabbro,dolerite,and rodingite.The spinels in the serpentinized peridotites have variable Cr^(#)values(21,38-46,and 59-61)and display affinity to those in abyssal and forearc peridotites.The dolerites show slight enrichment in Th and have elevated(La/Sm)_(N) ratios(1.19-2.01),indicating a subduction-related geochemical affinity.The Yanglong ophiolitic rocks have positive zirconεHf(t)values(+10.3 to+18.4)and whole-rockεNd(t)values(+5.3 to+6.7)indicating derivation from partial melting of a depleted mantle source.These results,together with the regional geology,collectively suggest that the Yanglong ophiolite was generated in a forearc setting during the Early Cambrian northward intra-oceanic subduction.It was emplaced onto the Central Qilian Block during the subsequent arc-continent collision,no later than the Early Ordovician.

关 键 词：forearc ophiolite intra-oceanic subduction arc–continent collision Qilian Orogen Proto-Tethys Ocean 

分 类 号：P588.2[天文地球—岩石学]