HR: 11:05h
AN: P42A-04    [Abstracts]
TI: Modeling the Chondrite Impact Histories Revealed by High-Pressure Minerals in Melt Veins
AU: * De Carli, P S
EM: paul.decarli@sri.com
AF: SRI International, 333 Ravenswood Ave, Menlo Park, CA 94025 United States
AU: Xie, Z
EM: Zhidong.xie@asu.edu
AF: Arizona State University, Dept. of Geological Sciences P.O. Box 871404, Tempe, AZ 85287 United States
AU: Sharp, T G
EM: tom.sharp@asu.edu
AF: Arizona State University, Dept. of Geological Sciences P.O. Box 871404, Tempe, AZ 85287 United States
AB: Melt veins are observed in numerous chondrites. These veins are analogous to pseudotachylites and represent material that was locally melted and quenched via conduction to the adjacent cooler material. Recent studies indicate that the high-pressure minerals crystallizing during vein solidification provide constraints on the shock pressure history during the vein-forming event (Chen et al. 1996, Langenhorst and Poirier 2000,Xie and Sharp 2004, Ohtani et al. 2004). The vein mineralogy of Tenham, for example, implies a pressure pulse having a duration > 50 ms over the narrow pressure range between ~ 18 GPa and 25 GPa. The upper bound of 25 GPa could imply a relatively low-velocity (~ 2 km/s) collision between two km-size bodies, based on the simple flat plate impact model. Alternatively, Tenham could have been located at a sufficient depth in a larger parent body to permit attenuation of the peak shock pressure from a higher velocity impact. Preliminary calculations, using the Autodyn(TM) 2-D wave propagation code indicate that pressures at the point of impact between spherical bodies decay much more rapidly than one would have predicted on the basis of the flat plate model. This paper presents the results of a wide variety of calculations, for impacts at velocities in range of 2 km/s-8 km/s between bodies of various shapes and compositions, including a rubble-pile model,in an attempt to find regions with pressure histories compatible with our observations on Tenham and other chondrites.
DE: 0545 Modeling (4255)
DE: 5420 Impact phenomena, cratering (6022, 8136)
DE: 5460 Physical properties of materials
DE: 6022 Impact phenomena (5420, 8136)
DE: 6240 Meteorites and tektites (1028, 3662)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005