New heat flow measurements in Oman and the thermal state of the Arabian Shield and Platform

Abstract

The present-day thermal regime of the Arabian plate is affected by the dynamics of the Afar plume and the rifting of the Red Sea and the Gulf of Aden. The Arabian plate is a Precambrian Shield and its thermal regime, before the plume and rifting activities, should be similar to that of other Precambrian Shields with a thick lithosphere. This is consistent with low heat-flow values measured in Saudi Arabia (35–44mWm−2), but not with recent measurements in Jordan that show higher heat flow (56–66mWm−2). We have conducted measurements in the eastern Arabian plate to obtain 10 new heat-flux values. We also derived 20 heat-flux values from oil exploration wells. Our measurements show that surface heat flux is uniformly low (45mWm−2) in the eastern Arabian Shield and is consistent with low crustal heat production (0.7μWm−3). A steady-state geotherm for the Arabian platform that intersects the isentropic temperature profile at a depth of 150km is consistent with the seismic observations. Differences in heat flow between the eastern (60mWm−2) and the western (45mWm−2) parts of Arabia reflect differences in crustal heat production as well as a higher mantle heat flux in the west. Seismic tomography studies of the mantle beneath Arabia show this east–west contrast. The lithospheric thickness for the Arabian plate is 150km, and the progressive thinning near the Red Sea is caused by the thermal erosion of the plume. The Afar plume mostly affects the base of the Arabian lithosphere along the Red Sea and the western part of the Gulf of Aden by channeling magmas from the asthenosphere through the rift. The continental domain is not affected by rifting in the Gulf of Aden. The main thermal effect of the Arabian plate is probably the channeling of the Afar plume to the North.