打古寨—罗布里两种不同类型花岗岩的岩石地球化学特征和形成条件探讨

一、地质概况打古寨岩体和罗布里岩体是桃山复式花岗岩基内部的两个小岩体。整个岩基的产出严格受本区NNE向深大断裂控制,出露面积约1000平方公里,形成时代为燕山早期。打古寨岩体位于岩基中部偏东部位,出露面积约30平方公里,形似一个南西端狭小、

Petrological and Geochemical Charcteristcs and Forming Conditions of Genetic Types of Granites in Daguzhai-Luobuli

Daguzhai and Luobuli granites occur as two small bodies of different genetic types. On the basis of field investigation and the study of petrology, petrochemistry and rare-earth elements as well as characteristics of strontium and oxygen isotopic compositions, it is believed that the Daguzhai granite is formed by the transformation of the upper caustal material through remelting, while the Luobuli monzogranite is generated by mixing of the mantle magma and the crustal materials basd on the data of inclusion thermometry and biotite chemical analysis, their crystallization conditions and emplacement depth are estimated. Besides,the genesis of andalusite and sillimanite in the Daguzhai granite is discussed on the basis of thermodynamic theory and geo- logical occurrence.