Continental lithospheric temperatures

Abstract

Thermal structure of the lithosphere exerts a primary control on its strength and density and thereby its dynamic evolution as the outer thermal and mechanic boundary layer of the convecting mantle. This contribution focuses on continental lithosphere. We review constraints on thermal conductivity and heat production, geophysical and geochemical/petrological constraints on thermal structure of the continental lithosphere, as well as steady-state and non-steady state 1D thermal models and their applicability. Commonly used geotherm families that assume that crustal heat production contributes an approximately constant fraction of 25–40% to surface heat flow reproduce the global spread of temperatures and thermal thicknesses of the lithosphere below continents. However, we find that global variations in seismic thickness of continental lithosphere and seismically estimated variations in Moho temperature below the US are more compatible with models where upper crustal heat production is 2–3 times higher than lower crustal heat production (consistent with rock estimates) and the contribution of effective crustal heat production to thermal structure (i.e. estimated by describing thermal structure with steady-state geotherms) varies systematically from 40 to 60% in tectonically stable low surface heat flow regions to 20% or lower in higher heat flow tectonically active regions. The low effective heat production in tectonically active regions is likely partly the expression of a non-steady thermal state and advective heat transport. Show more