Mineralogical and geochemical studies of glacial sediments from Schirmacher Oasis, East Antarctica

Schirmacher Oasis, East Antarctica hosts loose unconsolidated sediments that consist dominantly of sand-silt admixtures with minor clay. These sediments were collected from different glacial environments such as polar ice sheets, inland lakes, exposed bedrock, and coastal shelf areas. Two sediment fractions (coarse 0.25-0.125 mm and fine 0.125-0.063 mm) were separated and chemically analyzed. Mineralogically, the mixture is composed dominantly of quartz and feldspar, and a large variety of heavy minerals: zircon, tourmaline, rutile, garnet, hornblende, hypersthene, enstatite, kyanite, sillimanite, andalusite, zoisite, lawsonite, chlorite, spine!, topaz, and opaques. The clay minerals i.e., chlorite, illite, smectite, kaolinite, and vermiculite constitute a small fraction. There is a mineralogical control over the observed geochemical patterns and anomalies of these sediments. The rare earth element and incompatible trace element spidergrams show relative enrichment in the coarse fraction as against fine fraction, indicating enrichment of the carrier minerals of these elements (mostly heavy minerals) in the coarse fraction. The overall geochemistry of the sediments classifies them as greywacke as per Lindsey, Fe-sand to arenite as per Herron, and sodic sandstones as per Blatt et al. These sediments show quartzose sedimentary provenance, but influence of other unknown sources is also discernible. Transporting agencies for the sediments are commonly meltwater channels and wind. However, transport under influence of gravity, glacier action and sea waves are also envisaged. The sediments have undergone low degrees of chemical weathering ranging between incipient and moderate types. (C) 2012 Elsevier Ltd and INQUA. All rights reserved.