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The Moho transition zone in the Oman ophiolite-relation with wehrlites in the crust and dunites in the mantle

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Abstract

Field data in the Oman ophiolite show that the Moho transition zone (MTZ), which is on average 300 m thick above mantle diapirs, reduces to 50 m away from diapirs, with a sharp transition at the outskirts of the diapirs. We show here that this reduction is dominantly due to compaction of a dunitic mush present above diapirs in the MTZ, with upward injection of a wehrlitic magma in the crust, and, to a lesser extent, due to tectonic stretching. In order to explain the fraction of wehrlites injected into the crust, which is in the range of 25%, it is necessary that mantle upwelling is active, with a mantle flow velocity away from diapirs several times faster than the spreading velocity. If this velocity exceeds 5 times the ridge spreading-rate, a significant part of the MTZ may be entrained down into the mantle, flowing away from the diapir as tabular dunites.

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  1. David Jousselin

    Present address: Department of Geological Sciences, University of Oregon, Eugene, OR 97403, USA

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  1. Laboratoire de Tectonophysique, UM II, Pl. E.Bataillon, 34095, Montpellier Cedex 05, France

    David Jousselin & Adolphe Nicolas

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Jousselin, D., Nicolas, A. The Moho transition zone in the Oman ophiolite-relation with wehrlites in the crust and dunites in the mantle. Marine Geophysical Researches 21, 229–241 (2000). https://doi.org/10.1023/A:1026733019682

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