HR: 08:30h
AN: U21D-03 INVITED    [Abstracts]
TI: Energy Sources for an Early Dynamo
AU: * Buffett, B A
EM: buffett@geosci.uchicago.edu
AF: University of Chicago, 5734 S Ellis Avenue, Chicago, IL 60637, United States
AB: Convection in the Earth's core is currently driven by a combination of thermal and compositional buoyancy. The compositional buoyancy is due to light elements, which segregate into the liquid core as the inner core grows. Prior to the formation of the inner core, it is thought that convection is sustained solely by thermal buoyancy as the core cools. However, the high heat flow needed to power an early dynamo raises questions about the primordial heat needed to maintain this high heat flow over the age of the Earth. Radiogenic elements, such as 40^K, can provide another energy source which alleviates problems with the thermal history of the core. An alternate energy source involves changes in chemical equilibrium between the core and the base of the mantle. High-pressure experiments suggest that partitioning of oxygen and silicon between liquid iron and mantle minerals is strongly dependent on temperature. Cooling is expected to transfer light elements from liquid iron into the mantle minerals, leaving behind a dense, iron-enriched liquid at the top of the core. This additional source of compositional buoyancy can drive vigorous convection prior to the formation of the inner core and may be the primary energy source for an early dynamo.
DE: 8115 Core processes (1213, 1507)
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 8130 Heat generation and transport
SC: Union [U]
MN: 2007 Fall Meeting