Thermo-mechanical modeling of the obduction process based on the Oman Ophiolite case

Obduction emplaces regional-scale fragments of oceanic lithosphere (ophiolites) over continental lithosphere margins of much lower density. For this reason, the mechanisms responsible for obduction remain enigmatic in the framework of plate tectonics. We present two-dimensional (2D) thermo-mechanical models of obduction and investigate the possible dynamics and physical controls of this process. Model geometry and boundary conditions are based on available geological and geochronological data and numerical modeling results are validated against petrological and structural observations of the Oman (Semail) Ophiolite. Our model reproduces the stages of oceanic subduction initiation away from the Arabian margin, the emplacement of the Oman Ophiolite on top of it, and the domal exhumation of the metamorphosed margin through the ophiolitic nappe. A systematic study indicates that 350-400 km of bulk shortening provides the best fit for both maximum pressure-temperature conditions of the metamorphosed margin (1.5-2.5 GPa/450-600 degrees C) and the dimension of the ophiolitic nappe (similar to 170 km width). Our results confirm that a thermal anomaly located close to the Arabian margin (similar to 100 km) is needed to initiate obduction. We further suggest that a strong continental basement rheology is a prerequisite for ophiolite emplacement. (C) 2015 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.