Comparison of the crust and upper mantle structure of the Alboran and Algerian domains (Western Mediterranean): Tectonic significance

Abstract

We present a comparison of the present-day crust to upper-mantle structure in the Western Mediterranean along two NW-SE oriented geo-transects in the Alboran and Algerian basins. The Alboran domain geo-transect traverses the Iberian Massif, the Betics, the Alboran Basin and ends in the northern margin of Africa between the Tell and Rif mountains. The Algerian domain geo-transect traverses the Catalan Coast Ranges, the Valencia Trough, the Balearic Promontory, the Algerian basin, the Greater Kabylies and ends in the Tell-Atlas Mountains in the northern margin of Africa. We model the thermal, density (i.e. compositional) and seismic velocity structure by integrating geophysical and geochemical dataset in a self-consistent thermodynamic framework. The crustal structure is constrained by seismic experiments and geological cross-sections, whereas seismic tomography models and mantle xenoliths constrain the upper mantle structure and composition. The Algerian Basin lithosphere shows a typical oceanic lithosphere composition, whereas the Alboran Basin lithosphere is slightly fertile. The lithospheric mantle beneath the Betics and Greater Kabylies are also fertile compared to the Iberian and African lithospheres showing the involvement of the fertile sublithosphere mantle during the later stages of subduction. In the Valencia Trough, the lithosphere is fertile in comparison to the Balearic Promontory lithosphere, which is similar to Iberian lithosphere. A lithosphere-scale thickening is observed in the Betics, and the Greater Kabylies, and thinning follows towards the Alboran and Algerian back-arc basins. Detached slabs with anomalous temperature of-320 oC, with oceanic lithosphere composition beneath the Greater Kabylies, and Iberian lithosphere composition beneath the Betics, are required to fit the geoid height. Our results impose important constraints for the geodynamic evolution models of the Western Mediterranean.