3.08 billion-year-old crustal differentiation constrained by Sn and O isotopes of detrital cassiterite

Abstract

Formation of granite-hosted tin deposits reflects the differentiation and maturation of continental crust. While rare in Earth’s early continental crust, the eastern Kaapvaal Craton in southern Africa may harbor the oldest known tin-bearing granites. Here we present a perspective of early continental evolution from the study of Archean detrital cassiterite from the volcano-sedimentary continental cover succession of the Dominion Group of the western Kaapvaal Craton. The cassiterites yield a concordia age of 3084.7 ± 2.3 million-year-old, representing the oldest detrital cassiterite ever found. They are enriched in hafnium, zirconium, niobium, and tantalum, depleted in tungsten, and have overall consistent δ18O values (mostly 3‒5‰) but heterogeneous δ122/118Sn values (−0.59 to 0.79‰). They likely originated from erosion of peraluminous granites, forming immediate basement of the Dominion Group. The occurrence of ~3.08 billion-year-old detrital cassiterite suggests widespread tin mineralization in the granites, the intrusion of which led to stabilization of the Kaapvaal craton. A detrital cassiterite found in the Kaapvaal Craton, South Africa, implies widespread tin mineralization and stabilization of granitic cratons approximately 3.08 billion years ago, as shown by U-Pb geochronology, trace element and oxygen and tin isotopes.