Studies on the Weathering of Igneous Rocks

(1) Chemical studies were made on the weathering of quartz-trachyte at Sayo-machi, Hyogo-ken and at Gendayuyama, Tottori-shi, Tottori-ken. (2) The profiles of the weathering products studied consisted of the weathered rock, light brown horizon, light brown subsoil, and brown surface soil. These soils are sandy. (3) The amount of silica decreased by degrees from the lower horizon towards the subsoil, whereas it begans to increase in the surface soil. The alumina and iron oxide gradually increased in their amount from the lower horizon towards the subsoil, but in the surface soil they began to decrease. The bases decreased slowly through the weathering. Ca was more leachable than Mg. (4) The NIGGLI's h values increased from the lower horizon towards the subsoil, and then decreased or increased slightly in the surface soil. In the subsoils, the f values were maximum, the si and si/al values were minimum, and the amount of silica, alumina, and iron oxide which were dissolved by HCI and H2SO4 were maximum. The facts showed that the iron oxide and some parts of the clay having the low si/al values-had been transferred from the upper horizon to the subsoil. (5) The results obtained from alkali solution treatment showed that the weathering products contained very little free alumina._??_