广西合浦新屋面高岭石矿物学特征及其形成途径

Mineral Characteristics and Formation of Kaolinite in Xinwumian of Hepu,Guangxi

在野外实地考察的基础上,结合X射线衍射、扫描电镜(SEM)、化学成分分析等测试技术,对广西合浦新屋面高岭土矿床的风化物进行了研究。X射线衍射分析表明,黏土矿物主要为高岭石、伊利石、石英、正长石及斜长石。高岭石结晶度在0.489～1.210之间,随着深度的逐渐减小,高岭石逐渐增多,长石逐渐减少,高岭石的结晶程度则呈现变好的趋势,反映出花岗岩中原生矿物高岭土化程度逐渐加强。SEM结果表明,随着风化程度的加强,高岭石发育越来越好,晶形越来越完整。化学成分分析显示w(Al2O3)和w(K2O)互为消长关系,且随着深度的增大,Al2O3逐渐减少,K2O逐渐增多。该区长石蚀变为高岭土,可以经由绢云母中间阶段再转变形成高岭石和直接转变形成高岭石这两个途径。

This paper presents the study of the weathering mineral of kaolinite deposit in Xinwumian of Hepu,Guangxi,based on field investigation and X-ray diffraction,SEM and chemical analysis.The result of X-ray diffraction shows that the clay mineral consists of kaolinite,illite,quartz,orthoclase and anorthose.The crystallinity of kaolinite is between 0.489and 1.210.The kaolinite crystallinity tends to become better with the decreasing vertical depth,the gradual reduction of feldspar and the increase of kao-linite.This reflects the gradual strengthening of kaoliniation of primary minerals from granite.On the other hand,SEM images show the strengthening of weathering degree leads to the better growth of kaolinite and integrality of the crystal shape.While chemical analysis has revealed an alternative relation of growing and declining content of aluminium oxide and potassium oxide.With increase of the vertical depth,aluminium oxide declines gradually,while potassium oxide increases progressively.It is found that feldspar may be transformed into kaolinite either through an intermediate sericite stage or directly.