TY - JOUR
T1 - Dykes of the 1.11Ga Umkondo LIP, Southern Africa
T2 - Clues to a complex plumbing system
AU - De Kock, Michiel O.
AU - Ernst, Richard
AU - Söderlund, Ulf
AU - Jourdan, Fred
AU - Hofmann, Axel
AU - Le Gall, Bernard
AU - Bertrand, Hervé
AU - Chisonga, Benny C.
AU - Beukes, Nicolas
AU - Rajesh, H. M.
AU - Moseki, L. M.
AU - Fuchs, R.
PY - 2014/8
Y1 - 2014/8
N2 - The Umkondo Large Igneous Province (LIP) is represented by widespread (~2.0×106km2) mafic intrusions that were rapidly emplaced (1112-1108Ma) 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 ~1110Ma 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.
AB - The Umkondo Large Igneous Province (LIP) is represented by widespread (~2.0×106km2) mafic intrusions that were rapidly emplaced (1112-1108Ma) 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 ~1110Ma 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.
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U2 - 10.1016/j.precamres.2014.05.006
DO - 10.1016/j.precamres.2014.05.006
M3 - Article
AN - SCOPUS:84901814297
SN - 0301-9268
VL - 249
SP - 129
EP - 143
JO - Precambrian Research
JF - Precambrian Research
ER -