WEATHERING OF LIPARITIC-WELDED TUFF : Volumetric Research of Weathering

Abstract The degree of chemical weathering has been calculated from chemical analytical data on an A12O3 base, but the author used quartz insted of A12O3 because, the state of A12O3 is not constant. As an example, he used a soil profile derived from biotite-liparitic-welded tuff from Mt. Tokachi at Biel Tw. and studied it genetically. He decided it belonged to acid brown forest soil. The plagioclase content diminishes towards the surface but 14 and 7A minerals increase and are more obvious in the upper profile than in the A/B horizon. The volume change of each horizon in consequence of soil genesis was calculated by volume density and quartz content and the results indicated that the surface horizon and B horizons to 2.7 and 1.5-1.6 times the volume of the parent material, respectively. Recalculation of the data of the chemical analysis taking volume change into consideration showed some tendency towards the eluviation of the combined SiO2 in the A horizon. The author would consider this phenomenon as les...