福建同安二长花岗岩风化壳中的粘土矿物

二长花岗岩风化壳自下而上划分为原生带、微风化带、弱风化带和强风化带。风化壳中粘土矿物主要为埃洛石,其次为高岭石及少量伊利石。微风化带下部以高岭石为主,往上埃洛石逐渐占优势,并于弱风化带中、上部和强风化带中局部富集,这与当时地下水活动状态有关。高岭石结晶程度随风化程度的增强而提高。在弱酸性介质条件下及水分丰富、溶出条件强烈时,从长石解理面上和长石的“溶蚀”空隙中可以直接形成高岭石或埃洛石,而过渡阶段的伊利石很不发育或不存在。

CLAY MINERALS IN THE WEATHERED CRUST OF MONZONITIC GRANITE FROM CERTAIN PARTS OF FUJIAN

The weathered crust of monzonitic granite studied can be divided into fourzones in ascending order: the primary zone; the slightly weathering zone, theweakly weathering zone; and the strongly weathering zone. In accordance with an intergrated study by X-ray diffraction, infrared spe-ctroscopy, differential thermal analysis, electron microscopy and chemical ana-lysis, clay minerals in the weathered crust are predominated by hallysite andsubordinately by kaolinite and illite. The distribution of clay minerals in the weathered crust shows such an ob-vious trend that kaolinite is distributed mainly in the lower part of the slightlyweathering zone, while hallysite in the upper part of the weathering zone.They are less concentrated in the middle-upper parts of the weakly weatheringzone and strongly weathering zone. This trend is related to the moving of under-ground waters at that time. The degree of crystallization of kaolinite tends toincrease with increasing weathering extent. The major clay minerals are derived from the weathering of feldspar mine-rals which can directly develop into kaolinite and hallysite alone. the cleavageplanes of feldspars and the holes due to feldspar corrosion. In a weakly-acidmedium water is abundant and dissolution is intensive, Illite is not quite deve-loped at the transitional stage,