title: The postspinel phase boundary in Mg2SiO4 determined by in situ X-ray diffraction
abstract: The phase boundary between spinel (gamma 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 degrees to 1800 degreesC, 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 degreesC, which is approximately 2 gigapascals lower than earlier estimates based on other high-pressure studies.
authors.affiliation: T. Irifune, N. Nishiyama, K. Kuroda, T. Inoue, M. Isshiki, Department of Earth Sciences, Ehime University, Matsuyama 790, Japan. W. Utsumi, Japan Atomic Energy Research Institute, Kamigori, Ako-gun, Hyogo 678-12, Japan. K. Funakoshi, Ja.
authors.initials: T
authors.lastname: Irifune
authors.initials: N
authors.lastname: Nishiyama
authors.initials: K
authors.lastname: Kuroda
authors.initials: T
authors.lastname: Inoue
authors.initials: M
authors.lastname: Isshiki
authors.initials: W
authors.lastname: Utsumi
authors.initials: K
authors.lastname: Funakoshi
authors.initials: S
authors.lastname: Urakawa
authors.initials: T
authors.lastname: Uchida
authors.initials: T
authors.lastname: Katsura
authors.initials: O
authors.lastname: Ohtaka