Ages and tectonic significance of the collision-related granite porphyries in the Lhunzhub Basin, Tibet, China  

作　　者：WANG LiQuan ZHU DiCheng GENG QuanRu LIAO ZhongLi PAN GuiTang 

机构地区：[1]Chengdu Institute of Geology and Mineral Resources, Chengdu 610082, China

出　　处：《Chinese Science Bulletin》2007年第12期1669-1679,共11页

基　　金：Supported by the National "973" Project (Grant No. 2002CB412609);the National Natural Science Foundation of China (Grant No. 40572051);the Integrated Study of Basic Geology in the Blank Area of Southern Tibetan Plateau from China Geological Survey (Grant No. 1212010510218)

摘　　要：The Paleocene collision-related granite porphyries are identified for the first time along the western margin of the Lhunzhub Basin, Tibet. SHRIMP U-Pb zircon analysis indicates that the granite porphyries were emplaced at 58.7±1.1 Ma (MSWD = 0.79) during the Indo-Asian continental collision. The granite porphyries are peraluminous and high in K, belonging to the calc-alkaline to high-K calc-alkaline series. They are relatively enriched in LILE, Th and LREE and depletion in Ba, Nb, P and Ti, characterized by LREE-enriched patterns with slightly to moderately negative Eu anomalies. These Paleocene granite porphyries are interpreted as the products generated by partial melting of the pre-existing arc crustal rocks caused by the increase of pressures and temperatures during the crustal shortening at the early stages of the Indo-Asian continental collision since 65 Ma. Despite inherited geochemical features and tectonic settings of the arc protoliths, they are significantly different from the volcanic rocks of the Dianzhong Formation within the Linzizong Group and the Miocene granite por- phyries in the Gangdise belt.The Paleocene collision-related granite porphyries are identified for the first time along the western margin of the Lhunzhub Basin, Tibet. SHRIMP U-Pb zircon analysis indicates that the granite porphyries were emplaced at 58.7±1.1 Ma （MSWD = 0.79） during the Indo-Asian continental collision. The granite porphyries are peraluminous and high in K, belonging to the calc-alkaline to high-K calc-alkaline series. They are relatively enriched in LILE, Th and LREE and depletion in Ba, Nb, P and Ti, characterized by LREE-enriched patterns with slightly to moderately negative Eu anomalies. These Paleocene granite porphyries are interpreted as the products generated by partial melting of the pre-existing arc crustal rocks caused by the increase of pressures and temperatures during the crustal shortening at the early stages of the Indo-Asian continental collision since 65 Ma. Despite inherited geochemical features and tectonic settings of the arc protoliths, they are significantly different from the volcanic rocks of the Dianzhong Formation within the Linzizong Group and the Miocene granite porphyries in the Gangdise belt.

关 键 词：中国 西藏 林周盆地 古新世 花岗石斑岩 U-Pb锆石测年 

分 类 号：P597.3[天文地球—地球化学]