Metamorphic conditions during formation of a metapelitic sillimanite-garnet gneiss from Clemence Massif, Prince Charles Mountains, East Antarctica

Abstract

The pressure (P) and temperature (T) conditions during metamorphism of a metapelitic sillimanite-garnet gneiss from Clemence Massif, Antarctic Prince Charles Mountains, are estimated using mineral abundance information and petrogenetic P–T 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. Citation: Corvino A. F., S. D. Boger, and C. J. L. Wilson (2007), Metamorphic conditions during formation of metapelitic sillimanite-garnet gneiss from Clemence Massif, Prince Charles Mountains, East Antarctica, in Antarctica: A Keystone in a Changing World – Online Proceedings of the 10th ISAES, edited by A.K. Cooper and C.R. Raymond et al., USGS Open-File Report 2007–1047, Short Research Paper 062, 9 p.; doi:10.3133/of2007-1047.srp062