The origin of the Agulhas Plateau at the African-Southern Ocean gateway: Planned research on igneous rocks from Exp. 392

Gabriele.Uenzelmann-Neben [ at ]


The opening of the Southern Ocean gateways has been debated as a key element in the emergence of the Antarctic Circumpolar Current (ACC), crucial for the onset of global Cenozoic cooling (e.g., Sijp et al., 2014, Glob. Planet. Change 119; Voigt et al., 2013, EPSL 369/370). South of Africa, the opening was associated with the formation of several large igneous provinces (LIPs) including the Mozambique Ridge, Agulhas Plateau and the smaller Northeast Georgia Rise and Maud Rise. Plate tectonic reconstructions imply that the latter two were once part of the much greater Agulhas Plateau and were separated by subsequent rifting (Parsaglia et al., 2008, Geophys. J. Int. 174). It is debated whether and to what extent the emplacement of these large volcanic features obstructed the exchange of water masses between the Atlantic and the Indian Ocean thereby delaying the onset of the ACC. The Agulhas Plateau was drilled during recent IODP Expedition 392 (Uenzelmann-Neben, Bohaty, Childress, et al., IODP Exp. 392 Preliminary Report, 2022, in press). Igneous rocks were recovered at two sites on the southern part of the plateau (Sites U1579, U1580) and at one site near its northern edge (U1582). Preliminary (shipboard) data indicate that all sites returned tholeiitic basalts, formed by low pressure (shallow magma chamber) fractionation of mainly olivine and plagioclase (as typical for mid-ocean ridge basalts and many LIP lavas). 40Ar/39Ar dating will help to answer fundamental questions regarding the emplacement age of the plateau and its temporal-spatial evolution. Geochemical investigations of the recovered rocks will reveal the nature and source of the magmatism. The proposed project will focus on the determination of radiogenic (Sr, Nd, Hf, Pb) isotope compositions to further constrain the magma source composition for comparison with other regional and global LIP magmatism. In particular, we want to address the open question whether the Agulhas Plateau, Northeast Georgia Rise and Maud Rise magmatism can all be attributed to the same magma source and setting (“Greater Agulhas”) to test the previous plate tectonic reconstruction models. Additional questions are whether a (deep-sourced?) mantle plume initiated the magmatism and its causal relationship to the regional continental breakup and opening of ocean basins. The isotope data (in combination with the results from age dating and major/trace element geochemistry) will help to constrain the origin and impact of this regional LIP magmatism on tectonic configuration, ocean circulation, and global climate in the mid to late Cretaceous.

Item Type
Conference (Paper)
Primary Division
Primary Topic
Helmholtz Cross Cutting Activity (2021-2027)
Publication Status
Event Details
DFG ICDP/IOCP Kolloquium, 01 Nov 2022 - 03 Nov 2022, Potsdam, Germany.
Eprint ID
DOI 10.48440/gfz.b103-22074

Cite as
Geldmacher, J. , Davidson, P. C. , Liu, J. , Ichiyama, Y. , Hoernle, K. , Uenzelmann-Neben, G. , Bohaty, S. M. and Childress, L. B. , IODP Expedition 392 Science Party (2022): The origin of the Agulhas Plateau at the African-Southern Ocean gateway: Planned research on igneous rocks from Exp. 392 , DFG ICDP/IOCP Kolloquium, Potsdam, Germany, 1 November 2022 - 3 November 2022 . doi: 10.48440/gfz.b103-22074

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