老挝沙耶武里玄武岩的地球化学特征、成因及其地质意义  

Geochemical Characteristics and Petrogenesis of the Basalts in Xaignabouri,Laos and Their Geological Significance

作　　者：高建华[1] 范文玉[1] 王宏[1] 吴振波[1] 刘书生[1] 朱华平[1] 

机构地区：[1]中国地质调查局成都地质调查中心,成都610081

出　　处：《地质学报》2015年第9期1696-1702,共7页Acta Geologica Sinica

基　　金：国土资源大调查项目(编号12120114018701)资助成果

摘　　要：哀牢山古特提斯洋东南分支洋盆-斯雷博河洋在构造演化上存在俯冲极性问题,沙耶武里地区大片玄武岩的构造属性是对斯雷博河洋俯冲方向的重要制约。沙耶武里玄武岩SiO2含量为49.43%～51.35%,K2O＋Na2O含量为5.30%～6.18%,在化学成分上属于钙碱性岩石;其稀土元素的总量为57.65×10^-6～64.69×10^-6,LREE/HREE=3.69～3.84,表明在其形成过程中发生过一定程度的岩浆分异作用。基于此,对沙耶武里玄武岩进行了成因分析、构造环境和可能的形成机制探讨,认为沙耶武里玄武岩形成于岛弧环境之中,是在晚石炭世哀牢山-斯雷博河洋向西俯冲消减形成,其岩浆来源于受大洋岩石圈混染的亏损地幔楔,形成过程之中有地壳物质参与。The dispute still occurs in the tectonic evolution of the Srepok River Ocean-the southeast branch of Paleotethys ocean in Ailaoshan. The structural properties of large basalt in the Xayaboury area can offer an important constraint on subduction direction of Srepok ocean. Geochemcial analysis shows that basalts in the Xaignabouri area have SiO2 of 49.43%～51. 35% and K2O＋Na2O of 5.30 % ～6.18%, suggesting that it belongs to calcium alkaline type. Total REE content of 7.65× 10-6 ～64. 69 × 10^-6 and LREE/HREE ratio of 3.69～3.84 indicates a differentiation occurring in the formation of the basalt. Therefore, chemical composition of basalt can reflect the basic feature of chemical compositions of magmatic source and evolution. This study conducted an extensive study for tectonic environment and possible formation mechanism of the basalts in the Xaignabouri area. It is concluded that the basalt formed in the island-arc setting and resulted from the westward subduction of the Tethys sea in the late Carboniferous, and magma derived from the depleted mantle wedge, with involvement of also the oceanic lithosphere and crustal material during its formation.

关 键 词：玄武岩 地球化学 构造环境 沙耶武里 老挝 

分 类 号：P588.145[天文地球—岩石学]