大别造山带南坡晚白垩世玄武岩源区地幔特征  

MANTLE SOURCE OF LATE CRETACEOUS BASALTS IN SOUTH DABIE OROGENIC BELTS, CHINA

作　　者：匡少平[1] 张本仁[1] 凌文黎[1] 韩吟文[1] 

机构地区：[1]中国地质大学地球化学研究所,武汉430074

出　　处：《地质科学》2001年第2期203-211,共9页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学重大基金!项目"大别造山带结构;形成和演化的地球化学约束"( No.4 9794 0 4 3)资助

摘　　要：大别造山带南坡中生代断陷盆地中出露大量晚白垩世碱性玄武岩类。因岩浆受结晶分异和陆壳混染影响微弱 ,其成分基本可代表本区原生玄武岩浆。在微量元素原始地幔标准化蛛网图上 ,本区玄武岩具有地壳富集组分 Pb、K、Rb、Ba等的正异常和 Nb、P、Hf等高场强元素的负异常。同位素和微量元素特征显示 ,玄武岩浆来自亏损地幔 (DM)和富集地幔(EM +EM )混合源区。玄武岩源区地幔中 Pb的富集和 Nb、P、Hf等的亏损基本可由中国东部亏损地幔与榴辉岩的混合获得 ,由此揭示富集地幔端元组成特征可能与晚白垩世前造山带根部榴辉岩拆沉并参与地幔再循环有关。There are abundant Late Cretaceous basalts distributed in Mesozoic faulted basins in South Dabie orogenic belts. Since little obviously contamination from continental crust and differentiation crystallization being observed, it is suggested, based on a study of trace elements, that these basalts are resulted from batch partial melting of the regional mantle rocks and shared the same or similar geochemical features on magma source. In spider diagram normalized by primitive mantle, these basalts are characterized by enriched Pb and depleted Nb, P and Hf. Isotopic geochemical constraints reveal that their magma source has experienced some enrichment process, which imprinted the features of EMⅠ and EMⅡ components. To compared with the Meso Cenozoic basalts derived from the depleted mantle in the eastern China, the process can be explained by the delamination of eclogites in Dabie orogenic belt and their subsequent reaction with the mantle rocks. Moreover, the enriched Pb and depleted Nb, P and Hf of the Late Cretaceous basalts could be expected from the mixture of the depleted mantle in eastern China with the eclogites in Dabie orogenic belt.

关 键 词：地幔 玄武岩 榴辉岩 地球化学 大别造山带 晚白垩世 陆内造山作用 

分 类 号：P588.145[天文地球—岩石学]