老挝沙耶武里玄武岩的地球化学特征、成因及其地质意义
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本文为国土资源大调查项目(编号 12120114018701)资助成果。


Geochemical Characteristics and Petrogenesis of the Basalts in Xaignabouri, Laos and Their Geological Significance
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    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SiO2含量为49.43%~51.35%,K2O+Na2O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。

    Abstract:

    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 SiO2 of 49.43%~51.35% and K2O+Na2O 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.

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高建华,范文玉,王宏,吴振波, 刘书生,朱华平.2015.老挝沙耶武里玄武岩的地球化学特征、成因及其地质意义[J].地质学报,89(9):1696-1702.
GAO Jianhua, FAN Wenyu, WANG Hong, WU Zhenbo, LIU Shusheng, ZHU Huaping.2015. Geochemical Characteristics and Petrogenesis of the Basalts in Xaignabouri, Laos and Their Geological Significance[J]. Acta Geologica Sinica,89(9):1696-1702.

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  • 在线发布日期: 2015-09-16
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