Timing of thermal events in eastern Dronning Maud Land, East Antarctica

Using cathodoluminescence (CL)images,the zircons analyzed by K. Shiraishi et al.(J.Geol.,102,47,1994) for SHRIMP U-Pb dating (prior to the use of CL images) have been re-examined in order to unravel the periods of multiple zircon growth in eastern Dronning Maud Land.In addition four new SHRIMP U-Pb zircon age determinations are presented:two from the Yamato Mountains and two from the Lutzow-Holm Complex (LHC).The major conclusion from this study is that the Grenvillian basement is not ubiquitous in the LHC.Some outcrops are of late Archean-Paleoproterozoic crustal fragments reworked during the Pan-African event. In such cases,there is no indication of a Grenvillian event.Other protoliths are derived from Meso-Neoproterozoic juvenile crust and recycled continental sediments from the margin of the craton.Thus the pre-history of the Pan-African LHC is not uniform.In the Yamato Mountains,two stages of the Pan-African event are suggested,at ~620 Ma and ~535 Ma. These two stages are similar to those recorded in the Sφr Rondane Mountains and central Dronning Maud Land further to the west.These new and revised,updated results provide important constraints on tectonic models for the formation of Gondwana.