Geochemical studies on the rocks in the McMurdo Sound region

Geochemical studies were conducted in the McMurdo Sound region. Mossbauer spectrocopic studies of Desert Varnish, the physical and chemical weathering processes of the lavas on Ross Island and bedrock and soils of the Dry Valleys were investigated. 1) Mossbauer spectroscopic study of desert varnish: Samples of dolerite, granite, sandstone and quartzite heavily stained with desert varnish were collected from appropriate outcrops in the Depot Nunatak, the Kennar, Beacon, Pearce, land ower Taylor Valleys, the Labyrinth and the Upper Wright Valley and the Olympus range and Lake Vida areas of Victoria Valey. The prevailing wind direction, and patterns of local snow accumulations, particularly in the labyrinth, were noted to see if these were of significance to the distributions and nature of desert varnish coatings. Mossbauer spectroscopy and nuclear microprobe methods were used to study the iron mineralogy of these coatings to see if the different locations and bedrock types are of significance to their nature and formation. 2) Crystal chemistry of the Erebus lava flows: Samples of kenyte containing anorthoclase and plagioclase feldspar crystals were collected from exposed lava flows at Cape Royds, Barne, Evans, Turks Head and the Dellbridge Islands. Structural studies by xray diffraction methods were conducted on the samples to see if the Si/Al distribution in them can be determined and if the crystallographic parameters can be used to correlate the flows. 3) Examination of the bedrock and soils of the Dry Valleys: Soil samples were collected at the same locations as samples used for Mossbauer spectroscopic studies. Mossbauer spectroscopy was used to determine the extent of weathering and soil formation in these location and secondary iron oxide/oxidehydroxide mineralogy of the soils. In addition olivine containing samples were collected from Crater Hill and Observation Hill and from the cinder cones in the Lake Bonney area of the Taylor Valley and analysed by Mossbauer spectroscopy to determine the cation distribution and hence the cooling history of these olivines.