东天山喀拉塔格地区贝义西组火山岩地球化学特征及构造环境

摘要

This paper studies the Beiyixi Formation volcanic rocks from Kalatag area of Kawabulake block,as the re-search object in East Tianshan of China.Use of petrology,geochemistry methods to analyze petrogenesis and tectonic set-ting of Beiyixi Formation volcanic rocks.The results show that volcanic lava of Beiyixi Formation mainly composed of basalt,andesite,dacite and rhyolite.Rare earth elements (REEs) patterns have shown varying degrees of light rare earth el-ements (LREEs) enrichment,negative Eu anomalies gradually increased from mafic to acidity.Basalts trace with Ba,Ce, Nb,Zr,Hf positive anomalies,Sr,Th,P negative anomalies,showing the within plate basalt characteristics,and the initial of rift basalts similar.Some acidic volcanic samples showed the nature of the volcanic arc environment because of strongly crustally contaminated resulting in Nb,Ta,Yb,Y and other content decreased.The Beiyixi Formation volcanic rocks formed in an intraplate rift environment,and is the product of the initial break-up of Rodinia supercontinent.%以东天山卡瓦布拉克地块喀拉塔格地区贝义西组火山岩为研究对象，通过对岩石学、岩石地球化学分析，探讨贝义西组火山岩岩石成因及构造环境。研究表明，贝义西组火山岩主要由玄武岩、安山岩、英安岩及流纹岩组成，稀土元素分布型式反映不同程度轻稀土富集，从基性到酸性Eu负异常逐渐增强。玄武岩微量元素具Ba，Ce， Nb，Zr，Hf正异常，Sr，Th，P负异常，具板内玄武岩特征，与裂谷初期玄武岩相似。酸性火山岩受地壳强烈混染，使Nb，Ta，Yb，Y等含量降低，部分样品具火山弧性质。贝义西组火山岩形成于板内裂谷构造环境，是Rodinia大陆裂解初期产物。