Thermal history, continental growth, and the Urey ratio: How continental growth affects the thermal evolution of the Earth.

摘要

Early thermal history models predicted a high Urey ratio (>0.7), in contrast to more recent geochemical estimates of 0.15-0.6. To potentially help resolve this discrepancy, we explore the effects of adding continental growth to thermal history models. The addition of continents has two effects, continents sequester radioactive material out of the mantle, and continents insulate the mantle. We incorporated these coupled effects into thermal history models to constrain the continental growth scenarios that can satisfy observational constraints for present heat flow, mantle potential temperature, and Urey ratios. To further constrain the allowable class of models we also included a cooling core in the thermal history calculation. This provides two added constraints; a core heat flux >15 mW/m2 to generate a geodynamo and an inner core size consistent with present observations. These constraints limited the class of allowable continental growth models to those with a component of progressive growth.