栗木矿田深部新发现二云母花岗岩及其与上部白云母花岗岩的相变关系研究

Phase relationship between binary granite and upper Muscovite granite lately found at depth in Limu ore-field

在栗木矿田沟挂垒钻孔深部发现花岗岩体下部有厚度大于190m的二云母花岗岩,通过对二云母花岗岩以及上部白云母花岗岩的岩相学研究和分析对比,认为该区第二阶段的花岗岩上部为白云母花岗岩,在深部相变为二云母花岗岩,岩体中、上部的白云母花岗岩相主要是二云母花岗岩不同程度蚀变交代形成的,而不是岩浆就地重力分离结晶形成的,其蚀变程度相当于该区含矿花岗岩体矿化蚀变带下部的钾长石化带。无斑的白云母花岗岩相在钾长石化带中蚀变最强,最靠近主矿化蚀变带,有重要的找矿意义。各岩相的化学分析表明,W、Sn、Nb、Ta的矿化富集可能与岩浆气液分离作用或深部岩浆分异有关。

Binary granite,which has a thickness of more than 190m,has been found at depth in Gougualei of Limu ore-field lately by bore hole survey.Base on the petrographic analysis and comparative analysis of bina- ry granite and upper muscovite granite,this paper believes that the upper part of the granite of second phase is muscovite granite which turns to be binary granite at depth through phase transition.The muscovite gran- ite in the upper and middle part of the rock body is mainly formed by binary granite through alteration and re- placement but is not formed by gravitational separation crystallization.Its grade of alteration is as the same as that of K-feldspathization zone which locates at the lower part of mineralization alteration zone of mineral- bearing granite mass in this area.The alteration of lithofacies of Nonporphyritic muscovite granite is the strongest among K-feldspathization zone and its location is the nearest to main mineralization alteration zone.The prospecting potential is great.The chemical analysis on various lithofacies suggests that the concentrated mineralization of W,Sn,Nb and Ta may be related to magmatic liquid-gas separation or magma splitting at depth.