Geochronological evidence of Indosinian(high-pressure) metamorphic event and its tectonic significance in Taxkorgan area of the Western Kunlun Mountains,NW China  

作　　者：YANG WenQiang1,LIU Liang1,CAO YuTing1,WANG Chao1,2,HE ShiPing2,LI RongShe2 & ZHU XiaoHui1 1 State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an 710069,China 2 Xi’an Institute of Geology and Mineral Resource,Xi’an 710054,China 

出　　处：《Science China Earth Sciences》2010年第10期1445-1459,共15页中国科学（地球科学英文版）

基　　金：supported by National Basic Research Program of China (Grant No.2009CB825003);National Natural Science Foundation of China (Grant No.40972128);China Geological Survey "Comprehensive Research of Precambrian Geology and Paleozoic Tectono-paleogeography in Qing-hai-Tibet Plateau"

摘　　要：The CL images,LA-ICP-MS in situ trace elements analysis,and U-Pb dating for zircons indicate that the metamorphic ages of the sillimanite-garnet-biotite gneiss and the garnet-amphibole gneiss from eastern Taxkorgan of the Western Kunlun Mountains are 220±2 and 220±3 Ma respectively,and their protolith ages are younger than 253±2 and 480±8 Ma respectively.Two samples were collected at the same outcrops with HP mafic granulite and HP pelitic granulite.Mineral assemblage of the sillimanite-garnet-biotite gneiss(Grt+Sill+Per+Q) is consistent with that of HP pelitic granulite at early high amphibolite-granulite facies stage.Mineral assemblage of the garnet-amphibole gneiss(Grt+Amp+Pl+Q) is consistent with retro-metamorphic assemblage of HP mafic granulite at amphibolite facies stage.The dating results suggest that these HP granulites underwent peak metamorphism at 220±2 to 253±2 Ma.Thus,the Kangxiwar tectonic zone was probably formed by subduction and collision of the Paleo-Tethys Ocean during Indosinian.Protolith ages of the two samples,together with previously published U-Pb zircon dating age,suggest that the sillimanite-garnet schist-quartzite unit is a late Paleozoic unit,not a part of the Paleoproterozoic Bulunkuole Group.The CL images,LA-ICP-MS in situ trace elements analysis,and U-Pb dating for zircons indicate that the metamorphic ages of the sillimanite-garnet-biotite gneiss and the garnet-amphibole gneiss from eastern Taxkorgan of the Western Kunlun Mountains are 220±2 and 220±3 Ma respectively,and their protolith ages are younger than 253±2 and 480±8 Ma respectively.Two samples were collected at the same outcrops with HP mafic granulite and HP pelitic granulite.Mineral assemblage of the sillimanite-garnet-biotite gneiss(Grt+Sill+Per+Q) is consistent with that of HP pelitic granulite at early high amphibolite-granulite facies stage.Mineral assemblage of the garnet-amphibole gneiss(Grt+Amp+Pl+Q) is consistent with retro-metamorphic assemblage of HP mafic granulite at amphibolite facies stage.The dating results suggest that these HP granulites underwent peak metamorphism at 220±2 to 253±2 Ma.Thus,the Kangxiwar tectonic zone was probably formed by subduction and collision of the Paleo-Tethys Ocean during Indosinian.Protolith ages of the two samples,together with previously published U-Pb zircon dating age,suggest that the sillimanite-garnet schist-quartzite unit is a late Paleozoic unit,not a part of the Paleoproterozoic Bulunkuole Group.

关 键 词：Western KUNLUN MOUNTAINS LA-ICP-MS ZIRCON dating Bulunkuole Group INDOSINIAN Kangxiwar TECTONIC zone 

分 类 号：P597.3[天文地球—地球化学] P548[天文地球—地质学]