Oman Ophiolite Structural Constraints Complement Models of Crustal Accretion at the EAST Pacific RISE

Friday, 19 December 2014: 8:45 AM
David Jousselin1, Adolphe A Nicolas2 and Francoise I Boudier2, (1)CRPG Centre de Recherches Pétrographiques et Géochimiques, Vandoeuvre-Les-Nancy, France, (2)University of Montpellier II, Montpellier Cedex 05, France
This review documents significant similarities between East Pacific Rise (EPR), especially EPR at 9°-10°N and the Oman ophiolites. Both share comparable fast spreading rates, size and their dominant source of information that is mainly geophysical in EPR and structural in Oman. In these respects, they are remarkably complementary. Mantle upwelling zones at the EPR and mantle diapirs in Oman have a similar size and spacing. They punctually introduce basaltic melt and heat in the accreting crust, thus controlling elementary segments structure and activity. A tent-shaped magma chamber fits onto the diapir head, the top of which is a Mantle Transition Zone (MTZ) that stores, modifies, and injects the modified melt into the upper Axial Melt Lens (AML) beneath the lid. This MTZ-AML connection is central in crustal accretion, as documented in Oman. Heat from the diapir is captured above the Moho by the magma chamber and escapes through its walls, into a thin thermal boundary layer that bounds the chamber. Beyond, seawater at lower temperatures feeds smokers on the seafloor.