HAL will be down for maintenance from Friday, June 10 at 4pm through Monday, June 13 at 9am. More information
Skip to Main content Skip to Navigation

Mise en place et chimie des magmas dans le manteau supérieur de l'ophiolite d'Oman

Abstract : The Oman ophiolite offers the possibility to study mantle rocks which are inaccessible at mid-ocean ridges. The presence of five on-axis diapirs and an off-axis diapir allows comparison of magmatic processes occurring in these different settings. The Moho Transition Zone is dominated by dunite in both cases, but off-axis includes massive pyroxenites instead of layered gabbro. The off-axis diapir is surrounded by gabbroic intrusions in the crust and mantle, which are not found elsewhere in the ophiolite. While the on-axis samples have eNd values similar to those of MORB, all of the off-axis rocks have less radiogenic Nd suggesting a larger contribution from melting of pyroxenite veins in the off-axis source. The abundance of clinopyroxene in the off-axis MTZ results from the reaction between the pyroxenite-derived melts and the depleted harzburgite of the lithosphere, which explains the highly depleted incompatible trace element compositions of the clinopyroxenes. The presence of water from the hydrated lithosphere favors the crystallization of clinopyroxene instead of plagioclase, which should normally appear at this depth in the MTZ, as is the case on-axis. The gabbroic intrusions in the mantle and crust surrounding the off-axis diapir crystallized from the residual magma produced by the interaction between the pyroxenite-derived melts and the harzburgite. The off-axis diapir could be viewed as an analog to seamounts currently found near fast-spreading ridges, and could provide information on their internal structure. More generally, this study provides compelling evidence for the existence of pyroxenite veins in the asthenospheric mantle beneath mid-ocean ridges
Document type :
Complete list of metadata

Contributor : Thèses Ul Connect in order to contact the contributor
Submitted on : Thursday, March 29, 2018 - 12:52:29 PM
Last modification on : Tuesday, October 19, 2021 - 7:01:26 PM


Files produced by the author(s)


  • HAL Id : tel-01750683, version 1


Marie Nicolle. Mise en place et chimie des magmas dans le manteau supérieur de l'ophiolite d'Oman. Sciences de la Terre. Université de Lorraine, 2014. Français. ⟨NNT : 2014LORR0025⟩. ⟨tel-01750683⟩



Record views


Files downloads