西藏班戈北部早白垩世火山岩:班公湖-怒江洋闭合的岩浆记录  

Early Cretaceous volcanic rocks in northern Baingoin,Tibet:Magmatic record of the closure of the Bangong-Nujiang Ocean

作　　者：吴昊[1] 翟庆国[1] 胡培远[1] 唐跃[1] 朱志才 王伟[1] 谢超明 强巴扎西 WU Hao;ZHAI Qingguo;HU Peiyuan;TANG Yue;ZHU Zhicai;WANG Wei;XIE Chaoming;QIANGBA Zhaxi(Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;College of Earth Science,Jilin University,Changchun 130061,Jilin,China;Regional Geological Survey Party,Tibet Bureau of Geology and Mineral Exploration and Development,Lhasa 851400,Tibet,China)

机构地区：[1]自然资源部深地动力学重点实验室,中国地质科学院地质研究所,北京100037 [2]吉林大学地球科学学院,吉林长春130061 [3]西藏地勘局区域地质调查大队,西藏拉萨851400

出　　处：《中国地质》2021年第5期1623-1638,共16页Geology in China

基　　金：国家自然科学基金项目(42072268、42002069、41872240);第二次青藏高原综合科学考察(2019QZKK0703);中国地质调查局项目(DD20190370、DD20190060)联合资助。

摘　　要：对班戈县北部马前乡地区的早白垩世安山岩和英安岩进行了详细的地质填图及岩石学、年代学、地球化学和Hf同位素研究。锆石U-Pb定年获得安山岩年龄分别为(108.0±1.5)Ma和(113.6±0.9)Ma;英安岩年龄为(106.7±1.9)Ma和(113.6±0.8)Ma。安山岩富集Th和U,亏损Nb、Ta和Ti,具有变化范围较大的Mg^(#)值(25~63),锆石ε_(Hf)(t)值(-8.6~+1.5)以负值为主,应当为幔源镁铁质熔体与壳源熔体的混合产物。英安岩具有与安山岩类似的微量元素成分特征及负的锆石ε_(Hf)(t)值(-12.3~-8.1),应当是地壳部分熔融的产物。结合前人研究成果认为,这些早白垩世岩浆岩是约110 Ma沿班公湖—怒江缝合带岩浆大爆发的产物,可能与班公湖—怒江洋闭合之后的拉萨与羌塘地块陆-陆碰撞有关。The petrological,zircon U-Pb dating,whole-rock geochemical,and zircon Hf isotopic data of the Early Cretaceous andesites and dacites in the Maqianxiang area of Baingoin County,Tibet,are reported.The zircon U-Pb ages of andesite are(108.0±1.5)Ma and(113.6±0.9)Ma,and those of dacite are(106.7±1.9)Ma and(113.6±0.8)Ma.The andesites are enriched in Th and U and depleted in Nb,Ta,and Ti,have variable Mg^(#) values(25-63),and show mainly negative zircon ε_(Hf)(t)values(-8.6 to+1.5).They are probably generated by mixing of mantle-and crust-derived melts.Dacite shares similar trace element features with the coeval andesite,and has negative zircon ε_(Hf)(t)values(-12.3 to-8.1).It is interpreted as a product of partially melting crust.The andesite and dacite are interpreted as a product of the ca.110 Ma magmatism along the Bangong-Nujiang suture zone,and may be related to the continent-continent collision process after the closure of the Bangong-Nujiang Ocean.

关 键 词：早白垩世火山岩 地球化学 岩石成因 岩浆混合 地质调查工程 班公湖—怒江缝合带 

分 类 号：P588.142[天文地球—岩石学] P588.144[天文地球—地质学]