Mineralogical Characteristics of Yellow- Red Soils Derived from Granite

Mineral constituents and their weathering in yellow-red soils derived from granite in middle and lower reaches of the yangtze River were studied.Light minerals in fractions greater than silt contained over 80% quartz and feldspar,and heavy ones contained more than 60% various iron minerals and about 30% mica and bornblende.Kaolinite was the main clay mineral,the content of which was about 300-400g/kg.Quartz was weathered very weakly,Ca-feldspar was weathered over 65%,and about 25% of Na-feldspar was weathered.The vermiculitisation of mica was relativly obvious,>50% of mica being eathered to vermiculite.Weatherable minerals were also obviously eathered,the weathering being about 60%.Soil vermiculite was evolved through the process of mica→hydromica→vermiculite-chlorite→vermiculite,which was closely related to leaching situation and oxidic condition.

Mineral constituents and their weathering in yellow-red soils derived from granite in middle and lower reaches of the Yangtze R iver were studied. Light minerals in fractions greater than silt contained over 80% quartz and feldspar, and heavy ones contained more than 60% various iron minerals and about 30% mica and hornblende. Kaolinite was the main clay mineral, the content of which was about 300 -400 g/ kg. Quartz was weathered very weakly, Ca-feldspar was weathered over 65%, and about 25% of Na-feldspar was weathered. The vermiculitisation of mica was relativly obvious, > 50% of mica being weathered to vermiculite. Weatherable minerals were also obviously weathered, the weathering being about 60%. Soil vermiculite was evolved through the process of mica→hydromica→vermiculite-chlorite→vermiculite, which was closely related to leaching situation and oxidic condition.