First Petrological-Geochemical results from SO-232 (SLIP) at the Mozambique Ridge (SW Indian Ocean)

Gabriele.Uenzelmann-Neben [ at ]


The SO-232 cruise took place in April-May 2014 at the Mozambique Ridge, a presumably 120-140 Ma-old submarine volcanic plateau located in the SW Indian Ocean. The major goal of this multi-disciplinary project is to better understand the formation of the Mozambique Ridge, in relation to the opening of the South Atlantic Ocean and the break-up of the Gondwana supercontinent. Three different models have been proposed for the origin for this plateau: 1) a continental fragment formed during the break-up of Gondwana, 2) an independent microplate, or 3) an oceanic Large Igneous Province (LIP). Our studies aim to characterize age and geochemical composition of magmatic sam-ples in order to reconstruct the nature, origin, and spatial and temporal evolution of the plateau. The rock sampling mainly yielded basaltic lava (SiO2 = 47-52 wt. %) indicating a volcanic origin of the plateau. Bathymetry data show small cones scattered on the plateau, which represent the latest stage of volcanism. The samples form tight correlations with fluid-immobile trace elements ratios such as Nb/Yb and Th/Yb. Most of the samples have relatively flat REE pattern. A few, however, show steeper Heavy REE patterns, indicating a more enriched source or lower degrees of mantle melting. The REE patterns are consistent with a LIP origin of the plateau basement and a less voluminous, younger phase of volcanism. Sr and Nd isotope ratios extend from present-day South Indian mid-ocean-ridge basalts (MORB) and ocean island basalts (OIB) to slightly more enriched values. Prelim-inary age correction improves the Sr-Nd isotope correlation, and thus superimposed alteration effects can be excluded. On the uragonenic Pb isotope diagram, the samples extend to higher Δ7/4 than the South West Indian array and overlap the South Atlantic MORB field. This observation implies that initial opening of the SW-Indian Ocean was rather influenced by South Atlantic than Indian MORB mantle.

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GeoBerlin, 04 Oct 2015 - 07 Oct 2015, Berlin, Germany.
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Jacques, G. , Werner, R. , Hauff, F. , Uenzelmann-Neben, G. and Hoernle, K. (2015): First Petrological-Geochemical results from SO-232 (SLIP) at the Mozambique Ridge (SW Indian Ocean) , GeoBerlin, Berlin, Germany, 4 October 2015 - 7 October 2015 .

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