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Victoria University Antarctic Research Expedition Science and Logistics Reports 1992-93: VUWAE 37

ABSTRACT

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ABSTRACT

Lithospheric xenoliths were collected from basanitic scoria cones of the Mc Murdo Volcanic Province at a number of localities on and adjacent to Ross Island (Hut Point Peninsula, TurtleRock), Black Island and in the foothills of the Transantarctic Mountains.

The xenoliths vary from texturally variable, spinel lherzolites and dunites representative of upper mantle assemblages to ultramafic Al-augite ± kaersutite bearing ultramafic rocks and plagioclase bearing ultramafic to mafic granulites thought to represent the transition zone between upper mantle and lower crust. In some localities (e.g. Foster Crater) supracrustal rocks(sintered . granitoids and basement metasediments) occur in significant proportions. Many of the lower crustal mafic granulites are strongly layered mineralogically and, moreover, are notably denser than accepted upper mantle peridotites sampled from the same vent. This observation has an important bearing on the transition zone from lower crust to uppermost mantle and on model parameters for future geophysical modelling of sedimentary basin formation in the region.

The suites of xenoliths collected this season complement and in some cases (Black Island, Cape Bird and Foster Crater) greatly extend our existing xenolith sample sets. They will be used to expand previous models of 1 lithospheric structure for the Ross Sea Embayment region4 and to make comparisons with similar work being undertaken in West Antarctica as a part of the WAVE research programme, field work for which was undertaken in the 1989/90/91 seasons.