Magma genesis controlled by tectonic styles in the northern part of the Arabia plate during Cenozoic time
Widespread lava fields in the northern part of the Arabian platform are the subject of an open geodynamic debate on the origin of the intraplate volcanism. We present new K–Ar ages and whole-rock geochemical data for lava flows from Syria, which allow us to propose a new model of volcano-tectonic evolution highlighting how tectonics have controlled magma genesis in the region during the last 18 Ma. The Cenozoic Syrian lavas are alkaline and subalkaline rocks, typical of magma erupted in such a continental intraplate context. Basaltic samples from different Syrian volcanic provinces show significant variations in terms of incompatible trace element signatures. Crustal contamination plays a negligible role during magma migration and differentiation, and crystal fractionation is essentially restricted to olivine and clinopyroxene. Our results suggest that the Syrian lavas have been generated by variable degrees of partial melting (c. 1–10%) from different levels of a locally heterogeneous lithospheric mantle. The light/medium rare Earth element (LREE/MREE) ratios not only illustrate how the degree of partial melting has changed spatially and temporally during the last c. 18 Ma, but also indicate that the degree and the style of extensional tectonics has changed through time. We conclude that the Cenozoic Syrian volcanism is a consequence of extensional tectonics, under periodical influence of the north- and eastwards convergence at the Arabia–Eurasia margin, which induces rotational tectonic styles. This controls the partial melting at various depths in the mantle. The volcanism of northern Arabia developed in the framework of the Red Sea rifting and initiated at the same time as the southern Red Sea volcanism. It extends up to historical time, progressively smoothed to the north in a contradictory relation with the compressional/extensional setting of the Arabia–Eurasia margin.