Abstract

Refractory trace element concentrations in strongly weathered Hawaiian soils ranging in age from 20 to 4100 ka are highly elevated over parent-rock values due to extensive mass loss of more soluble major elements during pedogenesis. Nb and Ta exhibit virtually no mobility. Soil Nb/Ta ratios are within the range of fresh bedrock even when soil Nb concentrations are residually enriched by a factor of 10. In contrast, Al, Zr, and Hf are depleted relative to Nb in surface soil horizons but are enriched at depth, clearly indicating mobility of these elements. Variations in Th/Nb ratios in soil profiles indicate significant Th mobility within the soil column. However, mass-balance calculations require that accretion of Th-enriched Asian dust has resulted in a net increase in Th in some soils. Soils developed on a 150 ka rainfall gradient show that the mobility and loss of Zr increase with mean annual precipitation.

You do not currently have access to this article.