碳酸盐岩地区红土针铁矿中铝对铁的置换作用及其环境意义

ALUMINUM SUBSTITUTION OF GOETHITE FROM LATERITE IN CARBONATE ROCK-DISTRIBUTED AREAS

针铁矿是地表分布最广的氢氧化铁矿物，针铁矿的结构、成分和形态等特征，在一定程度上反映了其形成环境特征及其变化。根据作者提出和设计的红土中氧化铁矿物分离和分析程序，运用X射线衍射分析、红外光谱和电子探针等方法研究了贵州碳酸盐岩红土中针铁矿的铝类质同像置换作用。研究结果表明，针铁矿中铝的类质同像置换量定量地反映了碳酸盐岩红土成土地球化学环境和风化程度，是针铁矿的重要环境指示特征，具有一定的标型意义。

On the basis of high-gradient magnetic separation of iron oxide minerals from laterite in the carbonate rock-distributed areas, studies have been made of the Al-substitution of goethite by X-ray diffraction, infrared spectroscopic analysis and electron microprobe analysis. In terms of the systernatic measurement of Al-substitution for goehite from laterite, it is shown that in the study areas the appearance and regular pattem of the isommphous substitution of aluminum in goethite from laterite are affected rnainly by pedogenetic geochemistry and pedognetic environrnent, which is therefore of great significance in indicating environxnntal fluctuations.