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对研究区内花岗岩类的60个薄片进行了岩相学研究.研究的目的是确定区内岩石中普遍存在的矿物组成及结构类型. 碱性长石花岗岩为中粒,块状,白到粉色,主要由碱性长石和石英组成,含镁铁质矿物如黑云母、白云母等,含副矿物磷灰石、褐帘石和锆石.碱性长石占岩石组成的绝大部分,包括微斜长石和微条纹长石.斜长石晶体一般具钠长石—卡斯巴双晶,无条带. 正常花岗岩通常比碱性长石花岗岩稍暗,中—粗粒,一般为半自形粒状或花岗结构.长石和镁铁质矿物都以半自形晶体出现,而石英则通常为灰色玻璃质,充填于其他矿物颗粒之间. 对碱性斜长花岗岩和正常花岗岩所做的化学分析显示,这些过铝质岩石呈高Si、Al、Na和K含量的特征.其中碱性斜长花岗岩的氧化物含量为:SiO2 76.61%,TiO20.15%,Al2O3 12.81%,Fe2O3 0.67%,FeO0.5%,MnO0.01%,MgO0.19%,CaO0.18%,Na2O3.82%,K2O4.46%,P2O5 0.01%.正常花岗岩中氧化物含量为:SiO2 73.76%,TiO2 0.12%,Al2O3 13.93%,Fe2O3 0.77,FeO0.58%,MnO0.03%,MgO0.16%,CaO0.31%,Na2O3.04%,K2O3.64%,P2O5 0.02%. 关于花岗岩类中钾长石的成因有2种观点.一种认为形成于岩浆的结晶作用,钾长石或是缓慢长大,或是在成核作用后快速长大;另一种观点则认为钾长石是钾交代成因的.岩浆成?
A total of 60 thin sections of granitic rocks in the study area were studied by petrography.The purpose of the study was to determine the mineral composition and structure types prevailing in the rocks of the area.The alkaline feldspar granites were medium-grain, massive, white to pink , Mainly composed of alkaline feldspar and quartz, containing iron-bearing iron minerals such as biotite, muscovite, etc., with sub-mineral apatite, brown curtain stone and zircon.The alkaline feldspar accounts for most of the rock composition, including micro Plagioclase and micropaniform feldspar.The plagioclase crystals generally have albite - Casper double crystal, no band Normal granite is usually darker than the alkaline feldspar granite, medium - coarse grain, usually semi-self-shaped Granular or granodiorite feldspar and mafic minerals appear as semi-self-crystalline crystals, while quartz is usually gray vitreous, filled in between other mineral particles. For alkaline plagiogranite and normal granite chemistry The analysis shows that these peraluminous rocks are characterized by high contents of Si, Al, Na and K. The oxide content of alkaline plagioclase granites is 76.61% for SiO2, 0.15% for TiO2, 12.81% for Al2O3 and 0.67% for Fe2O3, FeO 0.5%, MnO 0.01%, MgO 0.19%, CaO 0.18%, Na 2 O 3 82%, K 2 O 4.46%, P 2 O 5 0.01% .The content of oxide in normal granite is: SiO2 73.76%, TiO2 0.12%, Al2O3 13.93%, Fe2O3 0.77, FeO 0.58%, MnO 0.03%, MgO 0.16%, CaO 0.31%, Na2O3 0.04% , K2O3.64%, P2O5 0.02% .There are two kinds of viewpoints on the genesis of K-feldspar in granites: one is that the crystallization formed in magma, K-feldspar either grows slowly or after nucleation Quickly grow up; another view is that potassium feldspar is the cause of potassium metasomatism.