新元古代宝兴杂岩的岩石成因及其对扬子西缘构造环境的制约  

Petrogenesis of the Neoproterozoic Baoxing Complex and its constraint on the tectonic environment in western margin of Yangtze Craton

作　　者：刘树文[1] 杨恺[1] 李秋根[1] 王宗起[2] 闫全人[2] 

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室,北京100871 [2]中国地质科学院地质研究所,北京100037

出　　处：《地学前缘》2009年第2期107-118,共12页Earth Science Frontiers

基　　金：国家重点基础研究发展计划“973”项目(2002CB412608);国家科技支撑计划(2006BAB01A11)

摘　　要：位于扬子克拉通西缘的新元古代宝兴杂岩主要由中低级变质的辉长质片麻岩、闪长质片麻岩、英云闪长质到花岗闪长质片麻岩和块状二长花岗岩组成。岩石地球化学和Sm-Nd同位素特征表明,辉长质片麻岩和闪长质片麻岩为同源岩浆演化序列,原始岩浆起源于亏损地幔尖晶石橄榄岩的部分熔融,在上升和侵位过程中受到了地壳岩石强烈混染。英云闪长质和花岗闪长质岩浆形成于下地壳玄武质岩石部分熔融,而二长花岗质岩浆形成于杂砂岩的部分熔融。综合分析宝兴杂岩的岩石组合、微量元素和同位素特征,该杂岩体最有可能形成于新元古代活动大陆边缘火山弧构造背景,并可能经历了碰撞过程。Neoproterozoic Baoxing Complex in middle to lower metamorphic grade, located in western margin of Yangtze Craton, consists mainly of metamorphic gabbroic, dioritic gneisses, tonalitic and granodioritic gneisses, and massive monzogranites. The studies of petrochemistry and Sm-Nd isotopes of Baoxing Complex reveal that the gabbroic and dioritic magmas came from a congeneric magma derived from the partial melting of spinel lherzolites in depletive mantle, and that the magma was intensively contaminated by crustal materials during its emplacement. The tonalitic and granodioritic magma were derived from the partial melting of metamorphic basalts in the lower crust. And the monzogranitic magma was formed from partial melting of metagreywacks. Integrating the lithological association, their trace elements, Sm-Nd isotopic characteristics and petrogenesis, the Baoxing Complex must likely have been emplaced in an island arc tectonic background at the Neoproterozoic active continental margin of Yangtze Craton.

关 键 词：宝兴杂岩 地球化学 SM-ND同位素 岩石成因 构造背景 

分 类 号：P588.345[天文地球—岩石学]