Lithospheric mantle xenoliths as a proxy for asthenospheric thermal events

Abstract

Thick lithosphere beneath continents plays an important role in suppressing heat loss from the earth. Heat flux through lithosphere-asthenosphere boundary (LAB) is critical in this regard and has been estimated from surface heat flow and thermal structure of the lithosphere from mantle xenoliths in alkali basalts and kimberlites by assuming steady heat flow and chemical equilibrium. We have estimated temporal change of thermal structure of the lithosphere near the LAB without such assumptions from mineral chemical study of spinel lherzolite xenoliths in alkali basalt from the Middle Atlas in Morocco and succeeded in detection of asthenospheric thermal event.