西准噶尔托里县布尔克斯台岩体岩浆混合成因的确认及其地质意义

Genesis of Magma Mixing and Its Geological Implications for Buerkesitai Granite in Tuoli County,West Junggar

布尔克斯台岩体中存在大量闪长质微细粒包体,在阿达依金矿外围最为发育。包体带状分布,大小不一,具有细粒-微细粒结构和斑状结构等典型的岩浆结构,与寄主岩石界线或截然或渐变过渡,形态多为长条状、扁(椭)球状等,显塑性流变特征,长轴与达尔布特断裂延伸方向基本一致。镜下见混合带,主要矿物边缘熔蚀呈不规则状,斜长石异常环带发育,且斜长石捕虏晶中包裹了许多细小的暗色矿物,包体中发育独特的针状空心磷灰石。这些闪长质微细粒包体的岩相学特征佐证了布尔克斯台岩体为一岩浆混合花岗岩,表明达尔布特构造-岩浆带发生过强烈的壳-幔岩浆混合作用。闪长质微细粒包体与阿达依金矿的密切共生关系,为进一步研究该金矿及该构造-岩浆带的金矿成矿物质来源与成因提供了新的思路。

Abundant diorite microgranular enclaves exist in Buerkesitai granite and many of them are outside the Adayi gold mine. The enclaves which are highly different in size with typical mag- matic structure, such as fine and micro-fine grained texture and porphyritic texture, are in ban- ding distribution. The enclaves show clear boundary or transitional relationships with host rocks. Diorite microgranular enclaves are in good streamline shape like strips or ellipsoid on the whole, showing the characteristics of plastic deformation. longitudinal axis direction. Under the microscope, The enclaves are parallel to Darbut Fault in irregular margins of main minerals, abnormal zoning of plagioclase and unique hollow acicular apatite are developed in enclaves and bands of non-uniform mixing. Abundant melanocratic microgranular minerals can be found in plagioclase xenoliths. These petrographical phenomenon of diorite microgranular enclaves confirm that the genesis of Buerkesitai granite is magma mixing granite. It indicates that intense crust and mantle magma mixing may have had occurred in Darbut tectonic magmatic belt. The fact that diorite mi crogranular enclaves and the gold mine are in a kind of symbiosis provides new ideas for further study of the source and origin of gold in Darbut tectonic and magmatic belt.