HR: 0800h
AN: T11E-1328    [Abstracts]
TI: EH vs. CI chondrite derived mantle: A geodynamical comparison
AU: * Samuel, H
EM: henri.samuel@yale.edu
AF: Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, P.O. Box 208109, New Haven, CT 06520-8109 United States
AU: Farnetani, C G
EM: cinzia@ipgp.jussieu.fr
AF: Laboratoire de Dynamique des Systemes Geologiques, Institut de Physique du Globe de Paris, 4 place jussieu, Paris cedex 05, 75252 France
AU: Javoy, M
EM: mja@ipgp.jussieu.fr
AF: Laboratoire de G‚ochimie des Isotopes Stables, Institut de Physique du Globe de Paris, 4 place jussieu,, Paris, 75251 France
AB: It is generally assumed that the Earth's bulk composition is derived from carbonaceous CI chondrites. However, arguments based on stable isotopes and redox considerations favor another type of material from which the Earth could be derived: the enstatite EH chondrites. The latter implies substantial heterogeneities either in minor and major elements within the mantle which is strongly suggested by seismological observations and further reinforced by noble gas constraints. Here we investigate the geodynamical consequences of CI and EH derived Earth's mantle compositions. Using numerical simulations in cylindrical geometry with an appropriate scaling to approximate the spherical Earth, we compare the evolution of mantles derived from EH and from CI chondrites from 4.5 Gyr B.P. to present day. For both EH and CI models the upper part of the mantle (from which continental crust is extracted) has a pyrolitic-like composition, therefore the differences between the two models are shifted to the lower part of the mantle mantle, implying substantial differences in heat producing elements concentrations and Si, Fe and Mg content. Both models consider the extraction of continental crust, heterogeneous internal heating related to local concentrations of heat producing elements, and the presence of chemically denser material in the lowermost mantle, as suggested by tomographic studies. The thermal and chemical evolution of these two models is therefore compared and the implications on present day mantle heterogeneity in both major and trace elements as well as the consequences on seismological observables are investigated.
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 8125 Evolution of the Earth
DE: 8130 Heat generation and transport
DE: 3655 Major element composition
DE: 1025 Composition of the mantle
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting