The Pan-African event in East Antarctica: a view from Sri Lanka and the Mozambique Belt

Late Pan-African (∼ 580-550 Ma) high-grade deformation of the Sri Lankan basement gave rise to a fold-and-thrust belt. The resulting axial planes to upright folds and earlier stretching lineations define a large-scale syntaxial bend. This syntaxis is attributed to E-W shortening and simultaneous sinistral strike-slip along a ∼ N-S-trending transcurrent zone, located west of Sri Lanka prior to Gondwana break-up. The resulting geometry is consistent with a 'corner effect' (Brun and Burg, 1982) produced by westward indenting of the basement underneath eastern Sri Lanka during collision. In Gondwana reconstructions, the sinistral strike-slip zone fits into the late kinematics of the Mozambique Belt (Shackleton, 1986). These new structural data constrain the position of Sri Lanka in Gondwana and favour reconstructions in which Sri Lanka is located near the Lützow-Holm-Bay in East Antarctica. A review of data from adjacent Gondwana fragments suggests that the tectonometamorphic evolution of the Sri Lankan basement is closely related to the interplay between two orogenic belts: the Mozambique Belt and the Lützow-Rayner Belt. It is argued that a late event of N-S shortening (Gondwana coordinates) in the Lützow-Rayner Belt can be attributed to a Pan-African tectonometamorphic event. In this interpretation, the Lützow-Rayner Belt developed in part simultaneously with the Mozambique Belt, reworking an older granulitic basement in the Rayner Complex.