Thursday, 30 August 2007
4.PS-99

P-T conditions during formation of a metapelitic gneiss from Clemence Massif, Antarctic Prince Charles Mountains

Adrian F. Corvino, Steven D. Boger, and Christopher J. L. Wilson. School of Earth Sciences, The University of Melbourne, Victoria, 3010, Australia

The pressure (P) and temperature (T) conditions during metamorphism of a metapelitic sillimanite-garnet gneiss from Clemence Massif are estimated using mineral abundance information and petrogenetic pseudosections computed in the chemical system MnO-N2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3 (MnNCKFMASHTO). Calculated mineral equilibria for the appropriate bulk composition predict that the observed assemblage, of K-feldspar-garnet-quartz-sillimanite-biotite-ilmenite-rutile, stabilised at approximately 8-9 kbar and 760-790ºC. Reaction microstructures are rare, but the preservation of relic spinel inclusions in garnet indicates an earlier low-P, high-T component and possible anticlockwise path resembling the Northern Prince Charles Mountains. On the basis of radiogenic age data, the metamorphism of Clemence Massif may be related to either of the ~1000 Ma or ~500 Ma episodes in East Antarctica and the possible superimposition of these episodes is an unresolved matter of concern.

[Manuscript]

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