Heat Flow, Heat Generation, and the Thermal State of the Lithosphere

The thermal structure of the lithosphere controls many properties and processes of Earth's crust. The total ∼47-TW heat loss of Earth is key to understanding and modeling this thermal structure, as is partitioning the various sources of that heat into heat entering the base of the lithosphere, heat generated within the lithosphere by radioactive decay (primarily within the continental crust), and secular cooling of the mantle lithosphere (primarily in oceanic lithosphere). A set of framework geotherms for the continental lithosphere explains deep crustal melting in high heat flow regions, metamorphic pressure-temperature (P-T) space in the crust, partial melting at the base of the lithosphere to produce an S-wave low-velocity zone in Phanerozoic and younger terranes, and the P-T fields inferred from mantle xenoliths. Important perturbations to a standard thermal state are produced by orogenic overprints, transient thermal regimes, and exhumation.