Deep-crustal layered mafic complexes in the Mesoproterozoic oceanic-arc of the Tugela Terrane, South Africa

dc.contributor.authorWilson, Allan H.
dc.date.accessioned2025-03-25T08:36:47Z
dc.date.issued2025-03
dc.description.abstractLayered mafic intrusions are important in understanding the generation of continental crust in oceanic arcs. The Mesoproterozoic (c. 1200 Ma) Tugela Terrane in southeast South Africa is made up of a series of thrust slices of varied rock-types purported to have been derived in oceanic arcs prior to accretion onto the southern margin of the Archean Kaapvaal Craton. They are not ophiolites. Mafic intrusions in two adjacent thrust slices are known as the Tugela Rand and Mambula Complexes. Both intrusions are intensely layered on scales of centimetres to several tens of metres but clear cyclic units are not apparent and crystal fractionation is limited indicating these were open systems with magma chamber through-flow. Tugela Rand is made up of dominantly olivine-bearing rocks ranging from dunite and pyroxenite to gabbro. In contrast, Mambula is dominantly gabbroic with only rare olivine-bearing rocks and is more evolved with layers of titaniferous-magnetite. Primary magmatic structures in both complexes include graded bedding, slumping and erosion features. Relatively high pressure of formation is indicated by the aluminous nature of the pyroxenes and corona textures by reaction between plagioclase and olivine. Chromitites in Tugela Rand range from massive to podiform with the rare orbicular variety indicating complex controls on chromite accretion. They include the high-Al compositional variety. There are no other similar chromitite occurrences in South Africa. The complexes, together with their enclosing rock-types, draw striking parallels with the lower arc crust observed in the late Cretaceous Kohistan arc complex in NE Pakistan. The Tugela Rand Complex shares many similarities with the Chilas Complex in that terrane, while the Mambula Complex is considered to be a more evolved derivative of the same magma. This study shows that generation of juvenile continental crust formation in mature island arc systems may have been firmly established by the Mesoproterozoic.
dc.description.submitterPM2025
dc.facultyFaculty of Science
dc.identifier0000-0002-0267-2236
dc.identifier.citationAllan H. Wilson, Deep-crustal layered mafic complexes in the Mesoproterozoic oceanic-arc of the Tugela Terrane, South Africa, Lithos, Volumes 504–505, 2025, 108052, ISSN 0024-4937, https://doi.org/10.1016/j.lithos.2025.108052.
dc.identifier.doihttps://doi.org/10.71796/wits-figshare.28570223.v1
dc.identifier.issn0024-4937 (print)
dc.identifier.issn1872-6143 (online)
dc.identifier.other10.1016/j.lithos.2025.108052
dc.identifier.urihttps://hdl.handle.net/10539/44428
dc.journal.titleLithos
dc.language.isoen
dc.publisherElsevier
dc.rights© 2025 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license.
dc.schoolSchool of Geosciences
dc.subjectNatal-Namaqua metamorphic province
dc.subjectChilas complex (Kohistan Island arc)
dc.subjectTugela Rand and Mambula Complexes
dc.subjectSupra-subduction oceanic arc
dc.subject.primarysdgSDG-15: Life on land
dc.titleDeep-crustal layered mafic complexes in the Mesoproterozoic oceanic-arc of the Tugela Terrane, South Africa
dc.typeArticle

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