HR: 1340h
AN: MR13A-0059    [Abstracts]
TI: Partial melting of Allende meteorite: Implications on early differentiation of planetary mantles
AU: * Mukherjee, S
EM: mukh0034@umn.edu
AF: University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, MN 55455 United States
AU: Hirschmann, M M
EM: hirsc022@umn.edu
AF: University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, MN 55455 United States
AB: Carbonaceous chondrites are one of the chief building blocks of primitive planetary bodies, so detailed exploration of their melting relations under appropriate P-T conditions can aid the comprehension of early differentiation in planets, planetesimals and meteorite parent bodies. Here we present results of partial melting experiments on Allende (CV3) under mantle conditions similar to those in the interiors of small planetary bodies. Experiments were performed in graphite capsules at 1GPa over a range of temperatures (1250°C to 1625°C) using an end loaded piston cylinder apparatus. The phase assemblage consists of liquid + olivine + metal sulphide ± spinel. With increasing temperature, olivine compositions range from Fo64 to Fo82, and spinels range from chromium number (100×Cr/Cr+Al) 26 to 58. In high temperature runs (1625°C - 1450°C) melts segregated at the margin of the charge and were mostly heterogeneous mats with quenched olivine blebs and fine metal droplets suspended in a melt pool. Melts were analyzed using defocused beam with variable spot size (10-100 microns). Liquids are FeO rich (34-36 wt.%) and SiO₂-poor (34-35wt.%) and show systematic compositional variation with increase in temperature. These liquids are more FeO-rich than known planetary basalts as reflected from compositions of achondrites, although Al₂O₃ and CaO contents are similar to shergottites. The data suggest that known achondritic basalts do not derive from simple carbonaceous chondritic sources, at least at conditions similar to those in the experiments.
DE: 3630 Experimental mineralogy and petrology
DE: 3662 Meteorite mineralogy and petrology (1028, 6240)
DE: 3672 Planetary mineralogy and petrology (5410)
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005