西藏拉萨地块西段狮泉河地区晚侏罗世花岗岩年代学、地球化学与岩石成因  

Geochronology, Geochemistry and Petrogenesis of Late Jurassic Granitoids in Shiquanhe Area, Western Lhasa Block, Tibet

作　　者：李勇[1] 张士贞 李奋其[1] 秦雅东[1] Li Yong;Zhang Shizhen;Li Fenqi;Qin Yadong(Chengdu Center of China Geological Survey,Chengdu 610081,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081

出　　处：《地球科学》2020年第8期2846-2856,共11页Earth Science

基　　金：国家自然科学基金项目(No.41773026);中国地质调查局项目(Nos.DD20160015-31,DD20190053)。

摘　　要：目前关于拉萨地块西段狮泉河地区中生代岩浆岩的报道相对较少,限制了对该地区中生代岩浆作用的认识.对狮泉河地区石英闪长岩和闪长质包体的锆石U-Pb年龄、岩石学特征与元素地球化学进行了研究.结果显示,寄主石英闪长岩的年龄为161.1±1.7 Ma,闪长质包体的年龄为159.8±1.6 Ma和157.0±1.3 Ma,两者为同期形成.寄主石英闪长岩为I型准铝质中钾-高钾钙碱性系列岩石,具有富集大离子亲石元素、亏损高场强元素的特征.闪长质包体为准铝质中钾-高钾钙碱性系列岩石.岩石学、地球化学特征研究表明,该套岩石可能与中侏罗世班公湖-怒江特提斯洋南向俯冲有关,班公湖-怒江特提斯洋南向俯冲引起幔源物质发生熔融,上涌的幔源岩浆与拉萨地块古老基底重熔形成的酸性岩浆混合,形成了含闪长质包体的晚侏罗世岩体.There are relatively few reports on the Mesozoic magmatic rocks in the Shiquanhe area of western Lhasa Block, which limits the understanding of the Mesozoic magmatism in this area. In this paper, it presents the major element, trace element and zircon U-Pb age data of bulk-rock for the host quartz diorite and dioritic enclaves from the Shiquanhe area. The zircon dating yields U-Pb age of 161.1±1.7 Ma for the host quartz diorite, of 159.8±1.6 Ma and 157.0±1.3 Ma respectively for dioritic enclaves,indicating that the host quartz diorite and dioritic enclaves have similar crystallization ages and they both formed at Late Jurassic.The host quartz diorite is metaluminous and calc-alkaline to high K calc-alkaline I-type granitoids. They are enriched in large ion lithopile elements, and depleted in high field strength elements. The dioritic enclaves are metaluminous and calc-alkaline to high K calc-alkaline. Based on the data in this study and previous ones, it is proposed that Late Jurassic quartz diorite was formed in tectonic setting of the southward subduction of Bangongco-Nujiang Neo-Tethyan oceanic seafloor, and generated by the magma mixing between mantle-derived basic magma and acidic magma formed by the melting of the ancient crustal material of Lhasa Block.

关 键 词：晚侏罗世 石英闪长岩 闪长质包体 锆石U-Pb年龄 狮泉河地区 地球化学 地质年代学 

分 类 号：P581[天文地球—岩石学]