A systematic investigation of ophiolite obduction resulting from the closure of small oceanic basins.

Ophiolite obduction, the process by which part of the oceanic crust overlaps the continental margin, is challenging when it comes to the geodynamic reconstruction of lithospheric processes. The oceanic crust is, on average, denser than the upper continental lithosphere. This density difference makes the obduction of the oceanic crust difficult, if not impossible, when only buoyancy forces are considered. To overcome the difficulties posed by the negative buoyancy, the initial configuration of the oceanic basins must have specific thermal and geometric constraints. Here we present a systematic investigation of the geometrical/geodynamical parameters which control the ophiolite emplacement process. We used the LaMEM finite-difference code and acounted for petrologically consistent density structure of the oceanic and continental regions. Our study reveals which parameters are the most important during ophiolite emplacement and which are the most optimal geometries that favor ophiolite emplacement.

Our current study focuses on “Tethyan” ophiolites which are characterized by relatively small inferred basin size and are commonly found in Mediterranean region. Based on a combination of various parameters, our study identified the most susceptible configurations for ophiolite obduction. Our models demonstrate, in agreement to geological data, that the obducted lithosphere must be young (<10Myr) and the length of the nature of Ocean-Continent-Transition (OCT) must be relatively sharp (length of initial OCT zone < 60 km) in order to achieve ophiolite obduction. In addition, our results show that the presence of a weak zone separating two parts of the oceanic lithosphere has a profound influence on the subduction initialization and final ophiolite obduction.