Abstract

This paper presents new U-Pb zircon ages on gneisses and pegmatite cropping out south of the Murchison greenstone belt. Located in the northeastern part of the Kaapvaal Craton, 190 km north of the classic and extensively studied granite-greenstone terrane of the 3.5 to 3.2 Ga Barberton Mountain Land, the 3.09 to 2.97 Ga Murchison greenstone belt is orientated along a major east-northeast crustal lineament. The belt is tectonically bounded to the north and south by a variety of Archaean granites and gneisses as well as an extensive zone of pegmatite development in the south. U-Pb zircon results on gneisses from south of the belt demonstrate that granite magmatism was associated with volcanism in the Murchison belt at around 3.09 Ga. Consequently, the belt could be interpreted as a volcanic arc linked to a subduction zone. U-Pb zircon results for the pegmatites point to a minimum age of 2.85 Ga. This age could be related to granitoid magmatism associated with intrusion of bodies such as the Willie Granite. These results demonstrate again that the granitoid rocks associated with the Murchison belt are markedly younger than those of the Barberton greenstone belt.

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