A review of tectonic events in the East Antarctic Shield and their implications for Gondwana and earlier supercontinents

Late Neoproterozoic to Cambrian tectonism in East Antarctica was widely assumed to have been restricted to the Ross Orogen at the Palaeopacific margin of the Precambrian shield, but it is now clear that two 'Pan-African age' mobile belts cut across the East Antarctic Shield, the Lutzow Helm and Prydz Belts, and these rework, truncate and offset three regions of late Mesoproterozoic to early Neoproterozoic tectonism: the Maud, Rayner and Wilkes Provinces. These three segments were previously assumed to form one single 'Grenville-age' orogen around the coastline, but now appear to represent distinct crustal fragments juxtaposed in the Cambrian. The Lutzow Helm Belt is a continuation of the East African Orogen and developed during closure of the Mozambique Ocean. It is unclear whether the Prydz Belt involved ocean closure or regional-scale transcurrent tectonics, but it does juxtapose numerous terranes with different geological histories, and it seems likely that the East Antarctic Shield behaved as a collage rather than a keystone during the amalgamation of Gondwana. Increasing evidence that East Gondwana underwent significant reorganisation during the Cambrian requires changes to current models for both the assembly of Gondwana and the configuration of the late Mesoproterozoic supercontinent of Rodinia. (C) 2000 Elsevier Science Limited. All rights reserved.