川西北碧口地块老河沟岩体和筛子岩岩体地球化学特征及其构造环境  

Geochemical Features and Tectonic Setting of the Laohegou Granite and the Shaiziyan Granite in Bikou Block,in Northwest Sichuan

作　　者：李佐臣[1] 裴先治[1] 丁仨平 刘战庆[1] 李瑞保[1] 孙雨[1] 冯建赟[1] 张亚峰[1] 

机构地区：[1]长安大学西部矿产资源与地质工程教育部重点实验室,长安大学地球科学与资源学院,西安710054

出　　处：《地质学报》2010年第3期343-356,共14页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40972136、40572121、40234041);教育部科学技术研究重点项目(编号104175)资助的成果

摘　　要：老河沟岩体和筛子岩岩体位于碧口地块西南部。岩体的SiO2(69.89%～71.69%)和Al2O3(15.01%～16.25%)含量均很高,A/CNK在1.04～1.12之间,为硅和铝过饱和类型,属典型的强过铝质花岗岩。稀土元素总量(∑REE)为33.13×10-6～150.42×10-6,稀土元素配分曲线呈右倾型,具有弱的负铕异常。高场强元素(Ta、Nb、Ti等)具有明显的负异常,大离子亲石元素(Rb、Ba、Sr等)具有明显的正异常。岩体可能是以杂砂岩成分为主的沉积岩部分熔融形成的花岗质岩浆上升侵位过程中形成的,是一种典型的壳源成因类型。老河沟岩体和筛子岩岩体具有后碰撞岩浆活动的特征,是印支期华北和扬子地块碰撞导致地壳加厚环境下下地壳部分熔融的产物,形成于同碰撞(挤压环境)向碰撞后(伸展环境)转化阶段,为后造山花岗岩类。The Louhegou granite and the Shaiziyan granite,located in southern margin of Bikou block. The data of occurrence,petrography and geochemical are reported,the source and tectonic setting of the granite are discussed in this paper. The results show that the Louhegou granite and the Shaiziyan granite have high SiO2（69.89%～71.69%）,and Al2O3 composition, A/CNK=1.04～1.12. It is a type with supersaturation of Al and Si,a typical strongly peraluminous granites. The ∑REE has the range of 33.13×10-6～150.42×10-6, REE diagram shows rightward incline and obvious Eu negative abnormity. The trace elements geochemistry was characterized by evidently negative anomaly of Ta,Nb,Ti,etc positive anomaly of Rb, Ba,Sr. The Louhegou granite and the Shaiziyan granite show post-collisional granitic characteristics. These rocks are post-orogenic granite,and are typical crust source petrogenesis. These granites mass are interpreted as a kind of syn-collisional granites resulted from the crustal thickening caused by the collision between the North China massif and Yangtze massif during the Indosinian. These rocks were transitional environment of compressional orogeny and extensional structure.

关 键 词：强过铝质花岗岩 地球化学 构造环境 后碰撞 碧口地块 

分 类 号：P588.121[天文地球—岩石学]