Early Paleozoic granitic magmatism related to the processes from subduction to collision in South Altyn, NW China

查看全文 作　　者：LIU [1]Liang;KANG [1]Lei;CAO [2]YuTing;YANG [1]WenQiang

机构地区：[1]State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University;[2]Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Minerals, College of Earth Science & Engineering,Shandong University of Science and Technology

出　　处：《Science China Earth Sciences》索引2015年第58卷第9期,共10页

基　　金：supported by the National Basic Research Program of China(Grant No.2015CB856103);the National Natural Science Foundation of China(Grant Nos.41430209,4140020262&41421002);Regional Geological Survey Project of Key Area in Western Kunlun-South Altyn from China Geological Survey and Special Fund from the State Key Laboratory of Continental Dynamics,Northwest University 摘　　要：Four episodes of granitic rocks at 517, 501–496, 462–451, and 426–385 Ma occurred in the South Altyn subduction-collision complex. The first episode of granite emplacement predates the formation of the ophiolite type mafic rock(?500 Ma), and the three subsequent episodes can be temporally correlated to high-pressure(HP) to ultrahigh-pressure(UHP) metamorphism at ca. 500 Ma, retrograde granulite-facies metamorphism at ca. 450 Ma, and amphibolite-facies metamorphism at ca. 420 Ma, respectively. A comprehensive study of these granitic rocks, along with the regional geological background, mafic-ultramafic rocks, and HP-UHP metamorphism, indicates that the four episodes of granitic magmatism are sequentially derived from the partial melting of the earlier subducted oceanic crust at 517 Ma, the thickened continental crust due to continental subduction at ca. 500 Ma, the mid-upper crust in response to slab breakoff at ca. 450 Ma, and the tectonic transition from contraction to extension at ca. 420 Ma. The formation age of 517 Ma for oceanic adakite provides a direct constraint on the time of the oceanic subduction in South Altyn. In addition, there is a ca. 10 Myr interval between the oceanic subduction to the continental deep subduction, suggesting that the Early Paleozoic tectonic evolution might have been a successive process in South Altyn. The four episodes of formation of granitic rocks, mafic-ultramafic rocks, and HP-UHP metamorphic rocks have fully recorded the tectonic evolution, beginning with the oceanic subduction, followed by continental subduction, and later exhumation during the Early Paleozoic in South Altyn. 关键词：花岗质岩石大陆俯冲碰撞络合物早古生代岩浆活动阿尔金镁铁质-超镁铁质岩超高压变质作用

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Early Paleozoic granitic magmatism related to the processes from subduction to collision in South Altyn, NW China

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