青川县鹰咀山花岗岩体地球化学特征及构造环境

摘要

This paper deals with petrological, microelement and REE geochemical characteristics and its tectonic setting of the Yingzuishan granite mass in Qingchuan, Sichuan. SiO2 content ranges from 67.50%to 70.21%with A/CNK of 0.77-1.05. REE geochemistry of the granite mass is characterized by∑REE of 206.44-412.63×10-6ppm, La/Yb of 36.59-53.48, and δEu value of 0.67-0.84. Microelement geochemistry of the granite mass is characterized by enrichment in LIL elements such as Rb, Sr, Ba, K and depletion in HFSE such as T, Nb, P, Ti with Sr/Y ratio of 30.25-64.85. These indicate that the granite mass belongs to I-type granite emplaced in a volcanic arc setting.%对四川青川县鹰咀山花岗岩岩体进行了系统的地球化学研究，重点讨论了岩体的岩石学、微量元素、稀土元素地球化学特征及其构造环境。该岩体SiO2含量变化范围67.50%～70.21%，A/CNK值在0.77～1.05。为硅饱和类型，部分铝过饱和类型，属准铝质至过铝质花岗岩。稀土元素总量为206.44～412.63×10-6，轻重稀土分异程度差别较大(La /Yb=36.59～53.48)，稀土元素配分曲线呈右倾型，弱负Eu异常(δEu=0.67～0.84)，富集大离子亲石元素Rb、Sr、Ba、K，亏损高场强元素Ta、Nb、P、Ti ，与正常壳源钙碱性花岗岩相比，显示出更高的Mg#（多数＞45）和Sr/Y比值（30.25～64.85），表明鹰咀山岩体为较高分异的I型花岗岩，形成于火山弧构造环境，可能是底侵的幔源岩浆与下地壳熔融产物混合的结果。