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The Postspinel Phase Boundary in Mg2SiO4 Determined by in Situ X-ray Diffraction

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Science  13 Mar 1998:
Vol. 279, Issue 5357, pp. 1698-1700
DOI: 10.1126/science.279.5357.1698

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Abstract

The phase boundary between spinel (γ phase) and MgSiO3 perovskite + MgO periclase in Mg2SiO4 was determined by in situ x-ray measurements by a combination of the synchrotron radiation source (SPring-8) and a large multianvil high-pressure apparatus. The boundary was determined at temperatures between 1400° to 1800°C, demonstrating that the postspinel phase boundary has a negative Clapeyron slope as estimated by quench experiments and thermodynamic analyses. The boundary was located at 21.1 (±0.2) gigapascals, at 1600°C, which is ∼2 gigapascals lower than earlier estimates based on other high-pressure studies.

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