Geochemical and Sr-Nd isotope constraints on the provenance of Permian deposits from Mozambique's Lower Karoo Zambezi Basin

Whole-rock geochemistry and Sr-Nd isotopic compositions of Permian mudrocks from the Moatize and Matinde formations were analyzed to constrain the sediment provenance, weathering history and palaeogeographic setting of the Moatize - Minjova Sub-Basin in the Karoo Zambezi Basin of Mozambique. The geochemical signatures of both formations suggest minimal effects of recycling and sorting, and point to rapid sediment deposition within an active tectonic setting. Trace element systematics and key provenance ratios (Th/Sc, La/Sc, Cr/Th, La N /Sm N, Eu/Eu*) indicate heterogeneous source areas dominated by felsic rocks with a minor mafic contribution. The mudrocks of the Moatize and Matinde formations exhibit similar isotopic signatures, with εNd (t) values of −9.32 ± 0.74 and −7.99 ± 1.10, and Nd T DM model ages of 1.68 ± 0.08 and 1.51 ± 0.12 Ga, respectively. These isotopic signatures indicate that both formations were derived from mixed sources, including late Mesoproterozoic and Neoproterozoic rocks from southern Malawi, the Nampula Block (a subdomain of southernmost Malawi), the Guro Suite and the Macossa-Chimoio Nappe. Both Moatize and Matinde mudrocks exhibit high Chemical Index of Alteration (>85) and Chemical Index of Weathering (>90) values, along with low Index of Compositional Variability and low K/Cs ratios. The Al 2 O 3 –(CaO + Na 2 O)–K 2 O (A–CN–K) relationships indicate that the Moatize and Matinde mudrocks have not undergone post-depositional K-metasomatism. The data collectively indicate intense palaeoweathering conditions in the source areas. Furthermore, the weathering indices suggest warm and humid palaeoclimate during the deposition of the Moatize and Matinde formations. These formations were deposited in a confined continental basin between the Guadalupian (middle Permian) and the Lopingian (late Permian). • Provenance proxies indicate a heterogeneous source area dominated by felsic rocks. • Sr–Nd isotopic data suggest the sediments were derived from mixed, predominantly local sources. • Geochemical proxies suggest intense palaeoweathering conditions in the source area(s). • Weathering indices point to warm and humid palaeoclimatic conditions. • Data support the presence of a palaeotopographic barrier between the Moatize-Minjova Sub-basin and the southern Karoo-age basins.