Thursday, 30 August 2007
4.PS-93

Pan-African granulites of central Dronning Maud Land and Mozambique - a comparison within the East-African-Antarctic Orogen

Ane K. Engvik1, Synnøve Elvevold2, Joachim Jacobs3, and Einar Tveten1. (1) Geological Survey of Norway, 7491 Trondheim, Norway, (2) Norwegain Polar Institute, 9296 Tromsø, Norway, (3) Institute of Geology, University of Bergen, 5020 Bergen, Norway

Granulite-facies metamorphism is reported extensively in Late Neoproterozoic/Early Palaeozoic time during formation of the East-African-Antarctic-Orogen (EAAO). Metamorphic data acquired from the Pan-African orogen of central Dronning Maud Land (cDML) are compared with data from northern Mozambique. The metamorphic rocks of cDML are characterised by Opx±Grt-bearing gneisses and Sil-bearing metapelites which indicate medium-pressure granulite-facies metamorphism. Peak conditions are estimated to 800-900 ºC at pressures up to 1.0 GPa. Peak metamorphism in cDML was followed by near-isothermal decompression during late-Pan-African extension and exhumation. In northern Mozambique, Grt+Cpx-bearing assemblages indicate high-pressure granulite-facies conditions during the Pan-African orogen with PT reaching 1.55 GPa and 900ºC. Garnet is replaced by symplectites of Pl+Opx+Mag indicating isothermal decompression, and the subsequent formation of Pl+amphibole-coronas suggests cooling into amphibolite facies. It is concluded that high-temperature metamorphism was pervasive in EAAO in Late Neoproterozoic/Early Paleozoic time, strongly overprinting any evidence of earlier metamorphic assemblages.

[Manuscript]