Crustal evolution of the East Antarctic mobile belt in Prydz Bay: Continental collision at 500 Ma?

The East Antarctic mobile belt as exposed in Prydz Bay presents an excellent example of a poly-metamorphic terrain where complicated high-grade structures can be grouped on the basis of lineation direction, sense of shear and metamorphic grade. In this way local intricacies resulting from truncating and interfering foliations and folds can be simplified by ordering structures with respect to their kinematic connotation. The resulting deformation scheme is simple and facilitates regional correlations, and simultaneously places metamorphic textures in a kinematic-structural background. The mobile belt in Prydz Bay is exposed along 200 km of coastline, and consists of granulite-facies gneiss in which low- to mid-crustal, compressional D-1-2 structures, and mid- to upper-crustal, extensional D-3-6 structures and related decompression-cooling textures are best explained in an exhumation model involving extensional collapse of upper crust in an overall compressional tectonic setting. This implies that compression and extension structures are genetically related. However, D-3-6 structures in the Larsemann Hills appear to have formed between 550 and 500 Ma, whilst D-2 structures in the Rauer Group have been dated at 1100-1000 Ma. Reinterpretation of the latter dates is possible, implying that most high-grade deformation in Prydz Bay is early Palaeozoic.