SHRIMP U-Pb zircon ages of granitoids from the Western Domain of the Kaapvaal Craton, Southeastern Botswana: implications for crustal evolution

Abstract

SHRIMP U-Pb zircon dating of granitoids from borehole cores from the Amalia-Kraaipan granite-greenstone terrain of southeast Botswana yielded dates of: 2939±9 Ma for the biotite granite gneiss, 2943±9 Ma for the pink granite and 2782±6 Ma for the red granite. These dates define two main granite magmatic events in the Western Domain of the Kaapvaal Craton at ~2.96 to ~2.94 Ga and ~2.78 Ga. In the Kaapvaal Shield the main magmatic events are dated at ~3.5 to ~3.3, ~3.2 to ~3.1, ~2.96 to ~2.94 and ~2.78 Ga. The two domains were therefore affected by coeval igneous events at ~2.96 to ~2.94 Ga and ~2.78 Ga and therefore the age of ~2.96 to ~2.94 Ga is taken to date their amalgamation along the Colesberg lineament. The ages of ~2.78 Ga correspond to the emplacement of the Gaborone Igneous Complex of southeast Botswana, which is possibly related to the reactivation of or renewed igneous activity along the Colesberg lineament.