HR: 0800h
AN: DI31A-0263    [Abstracts]
TI: Experimental Compaction in a Growing Dendritic Zone
AU: * Deguen, R
EM: renaud.deguen@obs.ujf-grenoble.fr
AF: LGIT, Université Joseph Fourier, Maison des Géosciences 1381, rue de la Piscine Saint Martin d'Heres, France, 38400,
AU: Alboussière, T
EM: talbouss@obs.ujf-grenoble.fr
AF: LGIT, Université Joseph Fourier, Maison des Géosciences 1381, rue de la Piscine Saint Martin d'Heres, France, 38400,
AU: Brito, D
EM: daniel.brito@ujf-grenoble.fr
AF: LGIT, Université Joseph Fourier, Maison des Géosciences 1381, rue de la Piscine Saint Martin d'Heres, France, 38400,
AU: La Rizza, P
EM: patrick.larizza@obs.ujf-grenoble.fr
AF: LGIT, Université Joseph Fourier, Maison des Géosciences 1381, rue de la Piscine Saint Martin d'Heres, France, 38400,
AU: Masson, J
EM: Jean-Paul.Masson@obs.ujf-grenoble.fr
AF: LGIT, Université Joseph Fourier, Maison des Géosciences 1381, rue de la Piscine Saint Martin d'Heres, France, 38400,
AB: The Earth inner core is thought to be in a state of dynamical equilibrium between dendritic solidification and compaction of the resulting solid-liquid region (or 'mushy zone') (Sumita et al.,1996). One important question is how much liquid can be trapped in the inner core, or how efficient is compaction to squeeze out the liquid phase. While this can be estimated theoretically in the case of non-reacting liquid and solid phases, this problem is somewhat more complicated in the case of a crystallizing mushy zone, as it involves a continuous mass transfer between the two phases as the system evolves. Consequences on the evolution of the connectivity of the melt as solidification proceed are difficult to assess, making the dependence of the permeability on porosity difficult to predict theoretically, particularly when the liquid fraction becomes small. Other open questions includes how does compaction and convection compete in the mushy zone? What are the effects of compaction on the thickness of the convecting zone? on the interdendritic spacing? on the structure and dimensions of chimneys? We present here preliminary results of an experiment devoted to the study of compaction during the dendritic crystallization of a model material. In our experimental set-up, compaction is promoted by a high apparent gravity, which is imposed by putting the crystallizing sample in a standard lab centrifuge, where the centrifuge acceleration can reach a few thousand g. While solidification proceed, the sample is scanned in situ with ultrasounds, allowing us to follow the propagation of the solidification front and to investigate the variations of ultrasound velocity and attenuation in the liquid, mush and solid domains.
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 1507 Core processes (1213, 8115)
DE: 8115 Core processes (1213, 1507)
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting