HR: 16:15h
AN: V34A-02    [Abstracts]
TI: Continental Growth and the Thermal History of the Earth
AU: * Lenardic, A
EM: ajns@rice.edu
AF: Rice University, Department of Earth Science, Houston, TX 77251, United States
AU: Woods, S G
EM: sgwoods@rice.edu
AF: Rice University, Department of Earth Science, Houston, TX 77251, United States
AB: First generation thermal history models predicted a Urey ratio (radiogenic mantle heat production divided by heat loss) of 0.7. Geochemical arguments constrain the Urey ratio to a range of 0.15-0.6. To potentially help resolve this discrepancy, we explore the effects of adding continental growth to thermal history models. Placement of radiogenics into the continental crust decreases the amount of radioactive material in the mantle. The thermal insulation effect of the continents affects the heat flow out of the mantle. We incorporated these coupled effects into thermal history models to constrain the continental growth scenarios that can satisfy constraints for present day mantle potential temperature and heat flow while at the same time predicting Urey ratios in accord with geochemical constraints. To further constrain allowable models, we also included a cooling core in the calculations. This provides two added constraints in that allowable models must have a core heat flux sufficient to generate a geodynamo and must predict an inner core size consistent with present observations. Under the assumptions of our modeling approach, these constraints limited the class of allowable continental growth models to those that have a component of progressive growth over geologic time (i.e., either smooth or episodic growth of continents over the Earths history).
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8125 Evolution of the Earth (0325)
DE: 8130 Heat generation and transport
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting