西藏措勤布嘎寺组中基性火山岩特征及成因

西藏措勤地区布嘎寺组火山岩是一套钾质到超钾质的岩石,根据化学组成可以分为中酸性和中基性火山岩.在前人研究的基础上对布嘎寺组中基性火山岩进行野外地质调查及全岩地球化学分析,并对该构造背景、源区性质及岩石成因做了进一步的研究和探讨.该火山岩具有轻稀土元素强烈富集、大离子亲石元素和高场强元素不同程度富集、弱负铕异常等地球化学...

Characteristics and causes of the intermediate-basic volcanic rocks from Bugasi Formation in Cuoqin,Tibet,China

The Cuoqin volcanic rocks of Miocene Bugasi Formation in Tibet are a set of potassic to ultrapotassic rocks.They are divided into two subgroups based on the chemical composition,that is,intermediate-acid group and intermediate-basic group.Based on previous studies,this paper further researches the tectonic setting,the nature of the source area and diagenesis by conducting the field geological investigation and doing geochemical analysis of the volcanic rocks from Bugasi Formation.The volcanic rocks are strongly enriched with LREE,large ion lithophile elements,high field strength elements to varying degrees,and weak negative Eu anomaly.They formed in an intra-continental extensional environment after the collision of Qinghai-Tibet Plateau and are probably the products formed by partial melting of the rocks from upper mantle and crust of different depths with different degrees.The formation and distribution is also controlled by the north-south graben which generated by the tectonic detachment and extension of Late Cenozoic on Qinghai-Tibet Plateau.