Ultrahigh temperature granulites and magnesian charnockites: Evidence for Neoarchean accretion along the northern margin of the Kaapvaal Craton

Abstract

SHRIMP U–Pb analysis of zircon grains from an ultrahigh temperature Mg–Al granulite from the northern margin of the Kaapvaal Craton (Southern Marginal Zone) shows ages of ∼2.72Ga for the peak metamorphism. Geochemical characteristics of syn-tectonic charnockites in the area are similar to magnesian charnockites, typically formed in subduction settings. In contrast to the prevailing models on peak metamorphism in the context of Neoarchean continent collision between Archean Zimbabwe and Kaapvaal cratons resulting in the formation of the Limpopo Complex, we relate the Neoarchean events to the accretion of this marginal block to the rest of the Kaapvaal Craton. In this model, the subduction event is marked by the formation of magnesian charnockites, and the ultrahigh temperature metamorphism dates the collision event.