摘要
广西黎塘碳酸盐岩红土风化壳发育良好。经鉴定的矿物有三水铝石、针铁矿、赤铁矿、高岭石、伊利石、锐钛矿、金红石、锂硬锰矿、蛋白石、石英和白云石等。研究表明,红土风化壳剖面自下而上,伊利石、高岭石减少,三水铝石、针铁矿、赤铁矿增多。因此,依矿物组合与演化次序,可分为以白云石为主的原生带,以高岭石为主的淋溶带和以三水铝石、针铁矿为主的水解带。在针铁矿中存在着铝的类质同象置换现象。这种置换,使X射线衍射峰的d值向低值方向偏移,偏移值和置换量呈线性关系,从而可计算其中铝的置换量;在红外吸收光谱分析图谱中,导致900cm^(-1)和800cm^(-1)两个吸收峰变得平缓,900cm^(-1)峰值向高频偏移,偏移量与铝的置换量亦呈线性关系,同理可以计算置换量。
The laterite weathering crust of Litang carbonatite, Guangxi, is well developed, consisting of gibbsite, goethite, hematite, kaolin, illite, anatase, rutile, lithium psilomelane, opal, quartz, dolomite, and so on. The study shows that from the bottom to the top of laterite weathering crust profile,illite and kaolin decrease, gibbsite, goethite and hematite increase. According to the association and evolutional sequence of minerals,the weathering crust can be divided into three zones,i. e. .primary zone dominated by dolomite,infiltration zone by kaolin and hydrolytic zone by gibbsite and goethite. The i-somorphous substitution of aluminium exists in goethite. The substitution results in deviation of a value of X - ray diffraction peak towards the low value. The deviation value is in the linear relation with the substitution amount, hence, the substitution amount of aluminium can be calculated in goethite. On the infrared absorption spectra obtained,the two absorption peaks of 900 CM-1 and 800 CM-1 become gentle, the peak value of 900 CM-1 deviating towards high frequency. The deviation value is also in linear relation with substitution amount of aluminium, the substitution amount can be calculated in this way.
