山西铝土矿的成因属性及地质意义

Genetic Attribute and Geological Significance of Bauxite Ores in Shanxi

通过对山西铝土矿成因研究 ,得出山西铝土矿是堆积 -沉积在长期风化的碳酸盐岩古陆上的古风化壳型铝土矿 ,风化源岩主要为基底碳酸盐岩及其过渡岩石和盐质沉积。其 2 6个一水硬铝石的氢氧同位素平均值 :δ1 8O为 8.1 6‰ ,δD为 - 1 0 9‰ ;3个勃姆石的 δ1 8O为 1 0 .4‰ ,δD为 -1 0 7‰ ;2 6个高岭石的 δ1 8O为 1 6 .84‰ ,δD为 - 91 .7‰。这些数值都与国内外近代风化壳及现代土壤中相同或相近矿物的氢氧同位素数值基本一致。而硬水铝石和高岭石的同位素计温还表明 ,山西铝土矿形成时的年平均气温为 3 2 .3℃或 2 9.4℃及 3 1 .3℃ ,属热带陆地大气环境下表生作用的产物。

Bauxite ores in Shanxi is a type of ancient weathering crust bauxite ores, which is accumulated and deposited on the old land of carbonate rock. Weathering source rock is mainly made up of basal carbonate rock,its transitional rock and salty deposits. The mean values from 26 samples of hydrogen and oxygen isotope compositions of diaspore in bauxite ores of Shanxi are that:8.16‰ for δ 18 O and -109‰ for δD; 10.4‰ for δ 18 O and -107‰ for δD in three boehmite; 16.84‰ for δ 18 O and -91.7‰ for δD in twenty six kaolinites. These data basically coincide with the values of hydrogen and oxygen isotope of similar ores in national or overseas modern weathering crust and soil. And the isotope thermometry of diaspore and kaolinites is also proved that mean annual formation temperature of bauxite ores in Shanxi is 32.3℃ or 29.4℃ and 31.3℃,which are supergenesis products under tropical land climatic environment.