Geochemical mass-balance in intensely weathered soils, Darling Range, Western Australia

摘要

Chemical weathering, one of the major processes that modify the earth's surface, exerts important controls on the geochemical cycling of elements. The behavior of elements in rock weathering processes, especially in intensely weathered regolith profiles, is not very well understood. In addition, rigorous calculation of the mass fluxes during intense weathering is seldom performed. This study aimed to determine geochemical mass balance for regolith profiles subject to intense chemical weathering. Twolateritic profiles in Western Australia with different weathering intensity were studied, to investigate influence of weathering intensity on element loss or gain. GE lateritic profile (CIA values 90.8-99.2), with kaolinite and gibbsite as main weathering products, is more intensely weathered than MQ profile (CIA from 63.6 to 83.9). Calculating mass balance with Zr as the immobile element, Na, Ca, Sr, Rb and Ba were almost completely depleted in the GE profile, while in MQ profile, only Ca loss as highas 95%. Aluminium, Ti and Fe accumulate at 0.6 m depth MQ profile, which also has the highest clay content; in the GE profile, Fe is significantly enriched from 3.5-7 m, forming haematite and goethite in duricrust and ferruginous matrix.