Abstract
Recent models for the chemical composition of the continental crust rely on various geophysical, geological, and petrological constraints and display a wide range in composition, with $$SiO_{2}$$ varying between 57 and 64 wt % and $$K_{2}O$$ varying between 1.1 and 2.4 wt %. Models that predict relatively high levels of the most incompatible elements imply extreme depletion (>70%) of these elements in the "depleted mantle." Crustal heat flow constrains the abundances of heat-producing elements (HPE: K, Th, U) within the continental crust and thus provides a relatively unambiguous and important test for these various models. The crustal radiogenic component of continental heat flow must lie within the range of $$18-48 mW/m^{2}$$ and almost certainly lies within the range of $$21-34 mW/m^{2}$$. The latter constraints limit the abundances of HPE within the crust (assuming K/U = 10,000, Th/U = 3.8, and a crust 41 km thick) to $$K_{2}O = 0.96-1.57\%$$; Th = 3.0-4.94 ppm, and U = 0.80-1.30 ppm. Models of crustal composition based largely on seismological or geological mapping data, and that predict relatively siliceous and incompatible element enriched compositions, exceed the upper limits of these constraints.
Published Version
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