Claymineralogy of soils developed on weathered igneous rocks, West Antarctica

Abstract

Soil samples collected from 33 outcrops of weathered plutonic, hypabyssal, and volcanic rocks scattered along a 1400 km traverse from the West Antarctic coastline to the Polar Plateau were analysed for claymineral content. Clay minerals present (in approximate order of abundance) are “mica”, chlorite, illite-smectite, smectite, kaolinite and vermiculite. The large amount of “mica” and/or chlorite in almost all host rocks and their associate soils, the small amount of clay (generally < 1%) present in all soils, theweak development of most soil proflles, and the large amount of glass in the clay-sized fraction of soils developed onTertiary basaltic rocks indicate that physical weathering is the dominant process of weathering in this area. Smectite, vermiculite and illite-smectite are products of chemical weathering. Kaolinite in soils from the Thiel Mountains is unusual, because formation of this mineral is generally thought to require at least moderate amounts of leaching. We feel that kaolinite in Thiel Mountain soils is inherited from the saussuritised cores of plagioclase crystals in host granodiorite. © 1990 Taylor & Francis Group, LLC.