Browsing by Author "Boger, Steven D."

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    Two pulses of Mesoproterozoic intra-plate magmatism in the heart of the Palaeoproterozoic Ubendian Domain of northern Malawi
    (Elsevier, 2023) Thomas, Robert J.; Boger, Steven D.; Fullgraf, Thomas
    Two Mesoproterozoic anorogenic igneous events are recorded in the Palaeoproterozoic Ubendian Domain in northern Malawi. The oldest is represented by the Mwakikome orthogneiss, a small peraluminous, sub-alkaline and ferroan syenogranite that has a U–Pb zircon emplacement age of 1411 ± 3 Ma, an initial εNd of 􀀀 4.5 and a Nd TDM2 model age of 2.27 Ga. These data are interpreted to suggest that the Mwakikome intrusion was derived mainly from the melting of the adjacent Palaeoproterozoic country rocks during Kibaran-aged extension. The second anorogenic igneous event is defined by the more widespread Mwenga Suite, a series of small (<100 km2) NW-SE oriented and elongated plutons that occur in a narrow belt in the north of the Ubendian Domain. Seven samples from different intrusions gave U–Pb zircon emplacement ages between ~1150 and 1110 Ma. The Mwenga Suite is comprised of rocks that are also ferroan, potassic and sub-alkaline in composition and shows a range of major element compositions from monzogranite to alkali-feldspar granite. Nd isotopic data from one sample yielded an initial εNd of 􀀀 2.2 and a Nd TDM2 model age of 1.88 Ga, suggesting that the suite was also largely derived from melting of the Ubendian host rocks, but with some additions from an enriched mantle source.