Thermal processes in the formation of continental lithosphere

Abstract
The thermal evolution of continental lithosphere in atectonic regions has been interpreted in terms of (1) conductive cooling, in the same way as oceanic lithosphere, but over much longer periods; (2) conductive cooling accelerated by erosion; (3) erosional removal of near-surface concentrations of heat-producing elements; and (4) various special temperature conditions assumed for its base. Although all of these factors influence lithospheric temperatures, particularly early in the development of continents, for times greater than 10 9 a, the thickness of the lithosphere and the processes by which it forms are of overriding importance. Continental lithosphere may develop by cooling and the thermal accretion of mantle material which has not been depleted of a basaltic first melting fraction, or it may develop by diapiric accretion of low-density, depleted mantle bodies rising from the upper parts of lithospheric slabs heated during their descent in subduction zones. The former process alone could not generate continental lithosphere with the observed characteristics. The latter process is likely to be important, possibly in combination with the former.

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