Crustal evolution in the central Congo-Kasai Craton, Luebo, D.R. Congo: Insights from zircon U–Pb ages, Hf-isotope and trace-element data

Abstract

Analysis of U–Pb ages, Hf isotopes and trace-element compositions in zircon collected from modern drainages is a robust methodology for tracking crustal and magmatic evolution. The application of the technique to zircons from the Luebo area in the central part of the Congo-Kasai Craton indicates the presence of a ∼3.6 Ga crust that underwent late Archean (2.9–2.5 Ga) reworking. Very low initial Hf-isotope ratios in zircons with U–Pb ages between 1.9 and 2.6 Ga suggest the presence of crust even older than 3.6 Ga at depth. The Archean crust underwent further reworking during Paleoproterozoic, Mesoproterozoic and Neoproterozoic thermal events. Post-Archean generation of juvenile crust appears to have occurred only sporadically during Meoproterozoic–Neoproterozoic time. The magmatic activity and tectonic events observed in the Neoproterozoic Katangan Belt had a regional extent as they also impacted the Congo-Kasai Craton where alkaline magmatism has occurred from late Archean to early Cambrian time. The ages of zircons with low HREE and U contents suggest three separate episodes of kimberlite magmatism in the central part of the Congo-Kasai Craton, in late Archean (2.8–2.6 Ga), Neoproteorozoic (850–582 Ma) and Cretaceous (116–70 Ma) time.