老挝孟南县晚石炭世玄武岩地球化学特征及成因  

Geochemical Characteristics and Genesis of Late Carboniferous Basalt in B. Muang-Nan County, Laos

作　　者：李振江[1] 吴振波[2] 游水生 刘书生[2] 李瑞 LI Zhen-jiang;WU Zhen-bo;YOU Shui-sheng;LIU Shu-sheng;LI Rui(-Regional Geological Surveying Team,BGEEMRSP,Chengdu 610213;-Chengdu Center,CGS,Chengdu 610081)

机构地区：[1]四川省地质矿产勘查开发局区域地质调查队,成都610213 [2]中国地质调查局成都地质调查中心,成都610081

出　　处：《四川地质学报》2018年第3期372-379,383,共9页Acta Geologica Sichuan

基　　金：中国地质调查局项目(编号:12120114018701-02);老挝1:20万孔县幅区域地质填图项目

摘　　要：老挝琅勃拉邦孟南县一带广泛分布的晚石炭世玄武岩为钙碱性系列-高钾钙碱性系列,亏损高场强元素,具Nb、Ta、Ti、Zr、Hf负异常的弧火山岩特征。岩石稀土总量(ΣREE)较低,轻稀土弱-中等富集,稀土元素配分模式总体协调一致,呈轻稀土富集的右倾斜型;岩石微量元素显示了与陆缘弧火山岩类似的稀土元素和微量元素配分曲线特征。构造环境判别图解表明该区玄武岩形成于陆缘岛弧及陆缘火山弧环境,是墨江-黎府-罗文真火山弧的基性岩组成部分。岩浆动力来源于晚石炭世哀牢山-斯雷博河洋向西俯冲的消减,其空间展布限定并指示了结合带的空间位置,其构造属性是斯雷博河洋俯冲极性的重要制约。The Late Carboniferous basalt is widely exposed in the Ban Muang-Nan County area, Luangprabang, Laos. The basalt belongs to calc-alkaline series to high-potassium calc-alkaline series basalt, with high A1203 （ 12.27-19.79% ） and low TiO2 （ 0.68-1.20% ）. The rock suite is characterized by depletion in HFSE such as Nb, Ta, Ti, Zr, Hf, characteristic of volcanic arc, EREE of 64.25 ppm in average, LREE/HREE of 3.46 in average, （ La/Yb ） N of 2.99 in average, （ Ce/Yb ）N of 2.2 in average, （ LaJSm ）N of 1.58 in average and （ Gd/Yb ）N of 1.35 in average, along with weak to medium enrichment in LREE. The tectonic discrimination diagrams indicate that the basalt was formed at a continental arc setting, i.e. Mojiang-Loei-Luowenzhen volcanic arc. The magmatism is thus suggested to be related to westward subduction of the Ailaoshan-Sre Pok Ocean in the Late Carboniferous. The spatial distribution provides the volcanic rock evidence for the southward extension of the suture zone, and an important constraint on the subduction polarity of Sre Pok ocean.

关 键 词：玄武岩 地球化学 构造环境 孟南县 老挝 

分 类 号：P584[天文地球—岩石学]