Central Tanzanian tectonic map: A step forward to decipher proterozoic structural events in the East African Orogen

Abstract

On the basis of a compilation of geological maps from central Tanzania coupled with structural and petrological studies a distinction is made between the tectonic evolution of the 1.8-2.0 Ga Usagaran orogeny and the 650-580 Ma Pan-African orogeny in the Mozambique Belt. The geometry of both orogens is determined by displacement partitioning around the indenting Tanzania Craton. The Usagaran Belt formed by strike-slip tectonics in an island arc regime. By contrast, the Mozambique Belt formed by westward thrust propagation during oblique collision of east and west Gondwana. This resulted in a first stage of lower crustal strike slip with isobaric cooling in the eastern hinterland. Continuous forward propagation of thrusts and coeval hinterland extension accompanied an isothermal decompression phase in all units. Displacement partitioning along the oblique continental margin triggered the formation of two crustal-scale Neoproterozoic shear belts, the dextral Central Tanzanian Shear Belt and the sinistral Kiboriani Shear Belt. Copyright 2005 by the American Geophysical Union.