GEOLOGIC HISTORY OF THE ARCHEAN BUHWA GREENSTONE-BELT AND SURROUNDINGGRANITE-GNEISS TERRANE, ZIMBABWE, WITH IMPLICATIONS FOR THE EVOLUTIONOF THE LIMPOPO BELT

The Buhwa Greenstone Belt (BGB) of southern Zimbabwe is the only major greenstone belt in the Archean Zimbabwe Craton directly adjacent to t he granulite-facies rocks that constitute the Northern Marginal Zone o f the Limpopo Belt. The deformational history and assembly of the BGB shed light on the evolution of the Northern Marginal Zone - Zimbabwe C raton transition. Assembly of the region began with deposition of the dominantly sedimentary cover succession at similar to 3.0 Ga on banded gneisses of the similar to 3.5 Ga Tokwe segment. At similar to 2.9 Ga the northern margin of the greenstone belt experienced kilometres of ductile, oblique-slip, dextral shearing. This shear zone was later int ruded by the granitic to tonalitic similar to 2.9 Ga Chipinda batholit h. The remaining events recognized in the region occurred during the t ime span 2.9-2.5 Ga. Northwest-directed thrusting of the Northern Marg inal Zone over the Zimbabwe Craton took place along a collection of di screte, typically metre-wide shear zones, which collectively form the tectonic break between the Zimbabwe Craton and the Northern Marginal Z one. In response to thrusting, the cover succession and surrounding gr anitoids were folded and underwent regional greenschist-facies metamor phism. Two suites of potassic granites were emplaced north and south o f the greenstone belt towards the end of thrusting. Plutonism was foll owed by conjugate faulting and later filling of the fractures by the G reat Dyke of Zimbabwe. The youngest events may have occurred between s imilar to 2.5 and similar to 2.0 Ga, and include sinistral shearing al ong the southern margin of the belt, transecting cleavage formation, a nd open folding as a result of northeast-directed crustal shortening.