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Victoria University Antarctic Research Expedition Science and Logistics Reports 1990-91: VUWAE 35

K-048 & S-081: WEST ANTARCTICA VOLCANO EXPLORATION (WAVE)

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K-048 & S-081: WEST ANTARCTICA VOLCANO EXPLORATION (WAVE)

J.A. Gamble (Victoria University, Wellington), J.L. Smellie (British Antarctic Survey), W,C. Mcintosh, K.T. Panter, P.R. Kyle and N.W. Dunbar (New Mexico Institute of Mining and Technology).

The two projected field seasons of the WAVE programme for research into the Intraplate volcanoes of West Antarctica have been completed. Detailed volcanological mapping and sampling was undertaken on Mounts Sidley, Waesche and Murphy and additional collections made at Mount Cumming, Dorrel Rock and the USAS Escarpment. Planned visits to Toney Mountain, the Crary Mountains, Mount Petras and Mount Flint were cancelled due to a combination of bad weather and aircraft breakdown.

The mapping programme confirmed that the majority of rocks forming Mounts Sidley and Waesche were erupted sub aerially while on Mount Murphy a transition from sub aqueous eruptions (perhaps sub glacial) at the base of the volcano to sub aerial at higher altitudes has been documented. In addition, sub aerial lavas can be demonstrated to have erupted onto glacially striated surfaces and occasional till horizons separate lava flow units - these sedimentary layers may yield microfossils which will be important paleoclimatic indicators. Other fossil material, which we believe to be the first insitu material from Marie Byrd Land, was found in sedimentary rocks forming the basement to Mount Murphy. High precision 40Ar/39Ar dating studies will be undertaken on samples collected across the transition zone. Detailed analysis of this data together with the stratigraphic information may yield important information as to the permanance of the West Antarctic ice sheet during late Cenozoic times.

Geochemical study of the volcanic rocks are being undertaken in order to understand the geochemical evolution of the magmas and their sources. Xenoliths (rock fragments entrained in the lavas and which were plucked from the lithospheric wall rocks as the magmas moved towards the surface) have been collected from parasitic scoria cones in all the centres visited. They range from shallow crustal rocks (either subvolcanic intrusions or immediate basement) to lower crustal (mafic and felsic granulites) to mantle peridotite in composition. The xenoliths promise to give unique information on the crust and lithosphere of the earth in a region where only the tops of the volcanoes peek through the ice cap.

At present two PhD projects are being undertaken in conjunction with the WAVE project and a number of papers have been submitted for presentation at the forthcoming Sixth International Symposium on Antarctic Earth Sciences.