Tropospheric origin of quartz in ando solls and red-yellow soils on basalts, Japan

Abstract

Abstract Fine quartz silt (1-10 pm diameter, characteristic size of aerosolic dust) isolated from two Ando soils from volcanic ashes (Fukuoka and Iwate), two Red-Yellow soils on basalts (Saga and Nagasaki) and one loess deposit (Saga) exhibited a very narrow range of oxygen isotopic ratios (expressed as parts per thousand relative to Standard Mean Ocean Water, SMOW, σ18O) varying from 15.8 to 16.1\%0. These values were almost identical with those reported for a mud-rain deposit (σ180=16.2\%0) and two north Pacific pelagic sediments near the Japanese Islands (d180= 16.2 and 16.6%0)' all derived from continental aerosolic dusts, carried by Westerly Winds. The quartz oxygen isotopic ratios of the selected Ando soils preclude both an indigenous volcanic ash (magmatic) origin and secondary crystallization under the ambient temperature. The oxygen isotopic results together with the covariant relationship between the fine-grained-quartz and 2 : 1 type day mineral contents suggest that the great bulk of the 2 : 1 day mineral-bearing phase of Ando soils of Japan is also of tropospheric origin, resulting from long distance eolian transport from Asian semi-arid and arid regions.