Abstract
The alteration of mica, chlorite and their related mineral in parent rocks from two terrains being the Middle Triassic to the Middle Jurassic was discussed in two paddy fields of Gray Lowland soils located in Fukui Prefecture.
Mica hardly altered to other mineral, but lost iron from its layer lattice and its crystallinity degraded a little in both two soils. Mica-vermiculite interstratified mineral in the Mino Terrain altered to vermiculite. Iron-rich chlorite in the Tanba Terrain changes partially to chlorite-vermiculite intergrade with the decrease of iron from its layer lattice. The alteration of these minerals was due to the decrease of iron content, the decrease of layer charge and the degradation of crystal structure, through the pedogenesis under the seasonally reductive condition.
