Dykes of the 1.11 Ga Umkondo LIP, Southern Africa: Clues to a complex plumbing system

• Published in: Precambrian Research
• Main Authors: de Kock, Michiel, O., Ernst, Richard, E., Söderlund, Ulf, Jourdan, Fred, Le Gall, Bernard, Bertrand, Hervé, Chisonga, Benny, C., Beukes, Nicolas J., Rajesh, H.M., Moseki, L.M., Fuchs, R.
• Other Authors: PPM Group University of Johannesburg, Department of Geology University of Johannesburg, University of Johannesburg South Africa (UJ)-University of Johannesburg South Africa (UJ), Department of Earth Sciences Ottawa, Carleton University, Department of Geology, Geobiosphere Science Centre, Skane University Hospital Lund, Laboratory for Isotope Geology, Swedish Museum of Natural History (NRM), Curtin University Perth, Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), CAE Mining Africa, Department of Geology, University of Botswana, University of KwaZulu-Natal Durban, Afrique du Sud (UKZN), Geological Survey of Botswana
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: Mesoproterozoic; Large Igneous Province; Geochronology; Rodinia; Kalahari craton; Dyke swarms; [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology; [SDE.MCG]Environmental Sciences/Global Changes; Grunehogna; Antarc*; Antarctica
• Online Access: https://insu.hal.science/insu-01004015; https://doi.org/10.1016/j.precamres.2014.05.006

International audience The Umkondo Large Igneous Province (LIP) is represented by widespread (∼2.0 × 106 km2) mafic intrusions that were rapidly emplaced (1112-1108 Ma) into the Kalahari craton of southern Africa and the formerly adjacent Grunehogna Province of Antarctica during Rodinia assembly. Very few Umkondo-aged dykes have been identified before, resulting in a poor understanding of this LIP's plumbing system and origin. Here we report six new ∼1110 Ma U-Pb TIMS baddeleyite ages for various dolerite dykes, which, when coupled with geochemistry from some of the dykes, suggest association with the Umkondo LIP. The distribution of dykes defines distinct radiating swarms, which locate two separate magmatic centers on the northern margin of the Kalahari craton, and a third less robust center on the SE margin. The Umkondo intrusions' geochemistry indicates significant partial melting of the sub-continental mantle lithosphere (SCLM) and requires a transient thermal anomaly in the mantle. A viable model sees a mantle plume ascend beneath the craton and split into different portions that moved and ascended to different lithospheric thin-spots along the margins of the craton. As an alternative, the rise in mantle temperature associated with continental aggregation at this time is considered sufficient to cause partial melting of the SCLM without any plume involvement. Specific features of the Umkondo LIP's plumbing system are supportive of either model, and an approach of multiple working hypotheses is recommended.