Interaction between layered mantle flow and progressively thinned lithosphere beneath the Armenia Volcanic Highland: Evidence from seismic azimuthal anisotropy

Removal of lithospheric mantle and subsequent volcanic activity are common phenomena along orogenic belts in response to plate convergence. In the Arabia-Eurasia collision zone, heterogeneous volcanism younger than 11 Ma, including Quaternary and Holocene-historical volcanism, is widespread in the northeastern Turkish-Armenian Plateaus. This post-collisional volcanism is attributed to significant lithospheric thinning, marked by a change in thickness of up to ∼50 km across Armenia toward Iran and Azerbaijan. Using a decade of unique datasets, we investigate the mantle flow patterns beneath the Armenia Volcanic Highland using azimuthal anisotropy constrained by shear-wave splitting. The large-scale pattern reveals a predominantly NE-SW fast direction, integrated with an ENE-WSW-oriented asthenospheric flow coupled to the plate motion and a sub-NS deep mantle flow likely originating from the Afar upwelling. Beneath the southwestern Armenian Highland, the detailed variation in anisotropy further suggests that the mantle flow is detoured around the sloping bottom of lithosphere. Owing to a higher thermal gradient at the lithospheric corner, edge-driven convection drives the progressive thinning of the lithosphere, which explains the migrating behavior of episodic delamination/volcanism.