HR: 15:25h
AN: U33B-08    [Abstracts]
TI: Deep mantle heat flow and thermal evolution of the Earth's core based on thermo-chemical mantle convection
AU: * Nakagawa, T
EM: takashi@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Sciences, University of Tokyo, 7-3-1 Hongo Bunkyo, Tokyo, 113-0033 Japan
AU: Tackley, P
EM: ptackley@ess.ucla.edu
AF: Department of Earth and Space Sciences, and Institute of Geophysics and Planetary Physics, University of California Los Angeles, 3806 Geology Building, BOX 951567, Los Angeles, CA 90095-1567 United States
AU: Buffett, B
EM: buffett@geosci.uchicago.edu
AF: Department of Geophysical Sciences, University of Chicago, 5734 S. Ellis Ave., Chicago, IL 60637 United States
AB: A coupled core-mantle evolution model that combines the global heat balance in the core with a fully-dynamical thermo-chemical mantle convection [Nakagawa and Tackley, 2004 published in EPSL] is used to investigate the deep mantle heat flow that is required to sustain the magnetic field generated by the geodynamo process. Effects of a radioactive heat source due to potassium in the core are also included in the global heat balance in the Earth??s core. Two important parameters are checked in this study; (1) density variation between depleted hartzbergite and basaltic material (0 to 3 percent) and (2) concentration of radioactive potassium in the core alloy (0ppm to 400ppm). The parameter set that most closely satisfies the criteria of size of the inner core (1220km at present time) is around 2 percent of density difference in a convecting mantle and 200ppm of radioactive heat source in the core. The concentration of potassium in the core is consistent with the geochemical approach [Murthy et al., 2003] but smaller than other successful thermal evolution models [Labrosse, 2003; Nimmo et al., 2004]. Heat flow through the core-mantle boundary and the contribution of radioactive heat sources in the core are consistent with theoretical estimates [e.g. Buffett, 2002] and geochemical constraints [Gessmann and Wood, 2002]. The power available to the geodynamo, based on the predicted heat flow through the core-mantle boundary, is approximately four times greater than the value predicted by numerical models of the geodynamo [Christensen and Kutzner, 2004] but closer to theoretical estimates [e.g. Buffett, 2002].
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 8125 Evolution of the Earth
DE: 8130 Heat generation and transport
DE: 1212 Earth's interior--composition and state (8105)
DE: 1213 Earth's interior--dynamics (8115, 8120)
SC: Union [U]
MN: 2004 AGU Fall Meeting