Geochemical Study on the Strandline Glacier Terra Nova Bay, Antarctica

Abstract

A chemical study has been carried out on ice samples, collected from the Strandline Glacier during the Italian Antarctic Expedition to Terra Nova Bay (Antarctica) in 1989-90, in order to investigate sources and mode and type of transport of elements and compounds present. Main lithophile (Na, K, Ca, Mg, Fe), trace lithophile (Ti, V, Cr, Mn) and heavy metals (Zn, Cu, Ni) were determined by flame and flameless A.A. spectroscopic and PIXE (Particle Induced X-ray Emission) analysis in a series of samples collected in a longitudinal section of the frontal portion of the glacier. After Collection, samples were melted and acidified with HNO3. Analysis was performed on the whole sample without filtration of the particulate matter. Element abundances for both main and trace lithophile and heavy metals are much higher than literature data for polar ice and snow. In particular, samples from the frontal cliff zone are especially enriched in «crustal» lithophiles. Element overabundancies derive from the presence of solid particles of different origin (continental terrestial and cosmic) and of seasalt by local strong aerosol. Excess of heavy metals correlates to improper control of contamination problems from field sampling to laboratory analysis. Calculation of crustal enrichment factors (EF) taking Ti as normalizing element suggests that the chemistry of samples from the frontal zone is essentially controlled by the amount of rock particles from the substratum inglobed in the glacier during its movement. On the contrary, the chemistry of the surface ice samples derives from atmospheric or tropospheric introduction of dissolved constituents and solid particles of different origin (primary marine aerosol, continental and cosmic dust, etc.). In these samples, the abundances of cosmogenic elements like Ni and Fe-Ni ratios confirm that in polar ice the ratio of cosmic dust to terrestrial dust is significantly high. This study suggests that chemical data may constitute valuable support to investigate interactions between glacier and substratum rock and thus to reconstruct past and present dynamics of glaciers.