内蒙古林西县北三段矿区花岗质岩石地球化学特征及构造背景

The Granitic Rocks' Geochemistry and Tectonic Setting of the Beisanduan Mining Area in Linxi County,Inner Mongolia

内蒙古北三段矿区处在华北地台北缘,区内有较多金及多金属矿床,具有良好的区域成矿条件。矿区内晚侏罗世侵入岩以花岗岩、花岗斑岩和石英闪长玢岩为主,具有高K和富碱的特点。通过将北三段矿区花岗岩的地球化学数据与国内外不同类型的花岗岩进行对比,判定北三段矿区花岗岩属于A型花岗岩,具有富Si、富碱、贫Mg的特点,Sr、P、Eu、Ti出现低谷,其稀土配分模式曲线呈右倾型,为典型的海鸥式。该类花岗岩可能是在造山运动完成后,岩石圈的伸展减薄环境中形成的。在岩石圈伸展减薄该过程中,局部压力的降低和软流圈的上涌对造成了地壳的部分熔融,从而为花岗岩的形成提供了条件。

The Beisanduan mining area is located in the northern margin of North China platform,where has good regional metallogenetic condition.There are lots of gold deposits and other polymetallic deposits in the region.After comparing and discriminating the geochemical data of monzogranite and alkali granite in the Beisanduan mining area with the various types of graniteat home and abroad,the granite in Beisanduan mining area is classified as A type granites,which is rich in Si and alkali,and is poor in Mg.The trace elements（Sr,P,Eu and Ti） present a trough,and the REE patterns show right deviation type,with a typical style of A-typegranite.These granites may be formed in the extension and thinning environment afterorogenic movement.The reduction of local pressure and upwelling of asthenosphere have played a certain role in the partial melting of crust,providing the conditions for the formation of granite.