- © 2010 Geological Society of South Africa
The Vungu shear zone is one of only two D3 shear zones in the Margate Terrane, and is here named and examined in detail for the first time. Detailed mapping indicates that this ~10 km wide shear zone can be subdivided into a high-strain core (~2 to 4 km thick) and lower-strain southeastern and northwestern marginal (each ~3 to 4 km thick) subzones. Macro- and microstructures are similar to other D3 shear zones in the Natal Metamorphic Province. Part of the northwestern marginal subzone shows D3-parallel magmatic foliation developed in the Oribi Gorge granite, thereby providing a reliable upper age of ~1.07 to 1.08 Ga for D3 in the Margate Terrane. This upper age is ~20 to 47 Ma older than that determined for the D3 event in the Mzumbe Terrane. Integration with newly constrained ages of the D1 (~1.09 Ga) and D2 (1.09 to 1.06 Ga) events illustrate their temporal overlap and support models that propose the D1– D3 structures comprise different expressions of the same tectonic event.