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Geochemical and Sr-Nd isotope constraints on the provenance of Permian deposits from Mozambique's Lower Karoo Zambezi Basin
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ABSTRACT: Whole-rock geochemistry and Sr-Nd isotopic compositions of Permian mudrocks from the Moatize and Matinde formations were analysed 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,Sm- Eu/Eu & lowast;) 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 epsilon Nd (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 Al2O3-(CaO + Na2O)-K2O (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).
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Palavras-chave
Geochemistry Palaeogeography Palaeoweathering history Moatize Crustal evolution Karoo Zambezia Mozambique
Contexto Educativo
Citação
Jorge, R.C.G.S., Fernandes, P., Pereira, Z., Santos, J.F., Lopes, G., & Marques, J. (2026). Geochemical and Sr-Nd isotope constraints on the provenance of Permian deposits from Mozambique's Lower Karoo Zambezi Basin. In: Journal of African Earth Sciences, 2026, vol. 238, article 106106. https://doi.org/10.1016/j.jafrearsci.2026.106106
Editora
Elsevier