THE HIGH-PRESSURE MELTING CURVE OF ALLENDE METEORITE

Laser-heated diamond-cell experiments on Allende meteorite, a natural analog for undifferentiated terrestrial planetary mantles, yield a mel ting curve increasing from similar to 2200 to 3200 K over the pressure range of 15-70 GPa, significantly below that of peridotite that is re presentative of the Earth's current upper mantle. Samples quenched fro m high temperatures and pressures reveal structures that may mimic the initial stages of differentiation between core and mantle materials. Micron-scale chemical analyses support the idea that sulfur is enriche d, and silicon, oxygen and aluminum are depleted, in the (potentially core-forming) metal relative to the silicate phases.