The Geochemical Features and Evolution of Laterite in the Karst Areas of Guizhou Province

摘要

Guizhou is one of the dominating karst regions, where laterite is widespread, in China. Seventy-two laterite samples were taken from twelve laterite sections in the karst areas of Guizhou Province, which are possessed of typical subtropical karst geomorphological and ecological environmental features and have evolved completely from dolostones and limestones. In terms of the major, trace and REE data for the samples this paper discusses the geochemical characteristics of laterite in the karst areas with an attempt to disclose the geochemical process and evolutionary rule of laterite formation. There have been involved three important pedoge-netic geochemical precesses in the formation of laterite in the karst areas: (1) enrichment of silicon and aluminum and depletion of calcium and magnesium; (2) enrichment of iron and manganese, and (3) enrichment of aluminum and depletion of silicon. During the formation and evolution of laterite, obvious enrichment and differentiation of trace elements such as Cu, Pb, Zn, Ni, Co, Cr, Rb, F, Cl, and As can be observed, but for the rare-earth elements, their enrichment is remarkable against a weak differentiation. The REE distribution patterns in the laterite are similar to those of its parental carbonate rocks.