福建郭山高岭土矿床中高岭矿物的研究

本文运用X射线衍射、红外吸收光谱、分析电子显微术和化学分析等多种方法对福建郭山高岭土矿床中的高岭矿物(高岭石和埃洛石)的矿物学性质、分布及矿物形成的阶段性变化进行了系统研究。结果表明,根据高岭石和埃洛石相对含量的多少,花岗岩风化剖面全风化带划分的4个矿物段可以反映这两种矿物的分布特点。埃洛石为具有管状和多面体球状的7?型以及10?—7?、7?-高岭石过渡型。高岭石晶体形态和结晶有序度在风化剖面垂直方向上的规律性变化与高岭石的形成经历了初始结晶——强烈高岭土化——风化作用后期的阶段性变化有关。

A Study of Kaolin Minerals from the Guoshan Kaolin Deposit,Fujian Province

The Guoshan kaolin deposit, located in the area from Tongan countytown to Xinxu of Fujian Province, is of weathering residual type formed byweathering of adamellite. Completely-weathering zone, semi-weathering zoneand parent rock can be separated in downward succession along theweathering profile. The completely-weathering zone (i.e.the main ore body)can be further divided into four mineral segments by estimation of therelative content of kaolinite and halloysite using transmission electron micros-copy. Studies indicate that kaolin minerals are mainly concentrated in thecompletely-weathering zone. The clay minerals have been studied systematically by such means asanalytical electron microscopy (AEM), X-ray diffraction (XRD), infraredabsorption spectra (IR), chemical analysis and optical examination. Theresults obtained show that they consist mainly of kaolin minerals (kaoliniteand halloysite) associated with small amounts of allophane, imogolite, sodicmontmorillonite, hydromucovite and "gibbsite. Kaolinite and halloysite, arecommon members of the kao1in group in the, 1:1 dioctahedral phyllosilica-tes. Allophane can also be regarded as a mineral related to this group.Detailed investigations show that kaolinite has low degree of order and ??irregular crystal form in the semi-weathering zone, higher degree of orderand pseudo-hexagonal sheet form in the completely-weathering surface soilzone. Such a regular variation in the degree of order and crystal form ofkaolinite in the weathering profile of monzonitic granite serves as an indi-cator of the developmental stage of the weathering crust. Halloysite ismainly of 2 H_2O (7 A) type, with transitional types of 10A to 7A and 7Ato kaolinite also discovered by XRD and AEM. The crystals of halloysite arebasically spherical and tubular in form. Halloysite contains interlayerwater which is readily dehydrated, and dehydration might result in partialor complete splitting and unrolling of tubes and the formation of the polygo-nal cross section. Having been dried, spherical halloysite takes somewhatpolyhedral form due to shrinkage. Morphological feature is very importantin the study of kaolin minerals and has been used as a diagnostic criterionto distinguish different mineral species in kaolin minerals.