Abstract
1. Six samples with different colors and textures, were selected according to the depth in the soil derived from, granodiorite at Ogoe, Fukushima Prefecture. 2. After the collected materials in wet state were treated with 6% H_2O_2 in order to dissolve organic matters, they were dispersed in the NaOH solution with pH 8.5. These dispersed materials were separated in eight fractions by sedimentation method and centrifugation, and then the iron-hydroxide was removed from them by using TRUOG'S method. 3. The minerals of the sand fraction in these samples were quantitatively investigated under microscope. 4. From these results it was distinct that the soil was mainly composed of the weathering products, of granodiorite with small amounts of the volcanic ash of two pyroxene andesite transported from upper parts. 5. The weathering of the granodiorite in this district took place in hornblende, succeeding to biotite, oligoclase and orthoclase. The fact indicated that the environment rich in bases was formed at the early stage of the weathering. Such an environment at the early stage seemed to be similar to that formed from the weathering of basic rocks. 6. That condition seemed to disappear before long due to the vigorous leaching of bases from the soil. 7. It was distinct that the process of the weathering of parent rock was possibly controled by the properties of parent rock, the stability of essential minerals for weathering, and, on the other hand, by rainfall and topography.
