COMPRES 2009 abstract

Melting experiments at high pressures

Andrew J. Campbell (1)
Noah A. Miller (1)
Rebecca A. Fischer (1,2)
E. Tess Van Orden (1)

(1) Dept. of Geology, University of Maryland
(2) Northwestern University

Melting and crystallization processes are responsible for most of the large scale differentiation in the Earth and other planets, so it is important to establish melting curves and phase diagrams to high pressure conditions. However, significant discrepancies remain in the recent literature, even for relatively simple phases and those that are very important to planetary interiors; therefore it is useful to have multiple experimental tools to investigate high pressure melting processes. Our present work is based on a recently developed method for measuring 2D temperature distributions in laser heated diamond anvil cell samples, and exploits changes in these temperature distributions and their relation to the apparent emissivity of the sample and (in some cases) laser power. We show melting curves in wustite, Fe-Si alloys, and Mo as examples of the method. Comparison of these results to our recent synchrotron XRD-based melting studies show that those measurements tend to slightly overestimate the melting temperature, if the axial temperature gradient through the sample is not explicitly accounted.