云南东川奚家坪玄武岩的地球化学特征、成因及其地质意义

为了探讨云南东川地区奚家坪玄武岩的地球化学特征及其意义,本文以奚家坪玄武岩的地球化学分析数据为基础,在分析了其主微量和稀土元素的特征之后发现奚家坪玄武岩w(SiO2)为46.44%～49.56%,(K2O+Na2O)为2.6%～5.8%,在化学成分上属于钙碱性-低钾拉斑型过渡的岩石;其稀土元素的总量为80.98×10-6～102.77×10-6,LREE/HREE=0.78～1.11,表明在其形成过程中并没有发生过大规模的岩浆分异作用,因此化学成分基本可以反映出岩浆源区的化学组成特征。基于此,对奚家坪玄武岩其进行了源区性质、构造环境和可能的成因机制探讨,认为奚家坪玄武岩形成于拉张环境之中,很有可能是在昆阳裂谷形成初期形成,其岩浆来源于较富集的地幔源区,形成过程中几乎没有地壳物质参与。

THE GEOCHEMICAL CHARACTERISTICS,PETROGENESIS AND GEOLOGICAL SIGNIFICANCE OF THE BASALTS IN XIJIAPING OF DONGCHUAN AREA,YUNNAN

Characteristics of the major,trace and rare earth elements from basalts in Xijiaping area show that it belongs to calcium alkaline-low potassium type in the chemical composition,and no large scale magmatic differentiation happened in the forming process.Therefore,chemical composition of basalt can reflect the basic feature of chemical composition of magma source.The magma source characteristics,tectonic environment and possible formation mechanism of the basalts in Xijiaping area are discussed,and conclusion reached that the basalts was forms in the tensional environment in the Kunyang rift valley in the early stage,and magma derived from the enriching mantle source area,almost no crustal material participates in the forming process.