Age of the Dominion-Nsuze Igneous Province, the first intracratonic Igneous Province of the Kaapvaal Craton

Abstract

The Kaapvaal Craton records a long Archaean to Phanerozoic history of intracratonic magmatism that reflects contrasting regimes of melt generation. The correct interpretation of this rich geological record relies critically on field evidence and ever refined chronological and isotopic data. Here, we present new U – Pb zircon, apatite and titanite ages, and Lu-Hf isotope results for volcanic and sedimentary rocks of the Dominion Group, its granitoid basement, and overlying strata of the Witwatersrand Supergroup. The data indicate an emplacement age of ca. 2.96 Ga for the Dominion Group, approximately 0.11 Ga later than previous estimates. These new ages, combined with lithological and geochemical similarities, allow the comparison and correlation between the Dominion Group and the Nsuze Group of the Pongola Supergroup. Together, the two successions constitute a single igneous province, here termed the Dominion-Nsuze Igneous Province, which was emplaced shortly after craton consolidation, spanning approximately 500 km across the central and eastern Kaapvaal Craton. This province constitutes the first intracratonic igneous province of the Kaapvaal Craton and one of the oldest in the world. The new age determinations also place limits on the onset of sedimentation of the overlying Witwatersrand Supergroup, which can now be constrained at < 2960 Ma.