Density and bulk sound velocity jumps across the 660 km seismic discontinuity

• Published in: Physics of the earth and planetary interiors Vol. 125; no. 1; pp. 141 - 146
• Main Author: Matsui, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2001
• Subjects: 660 km discontinuity; Equation of state; Lower mantle; Mantle transition zone; Phase transformation; Lower mantle; Phase transformation; Mantle transition zone; Equation of state; 660 km discontinuity
• ISSN: 0031-9201; 1872-7395
• DOI: 10.1016/S0031-9201(01)00235-7

Molecular dynamics (MD) simulation with realistic and accurate potential models, previously obtained for Mg 2SiO 4 polymorphs, MgO periclase and MgSiO 3 polymorphs, is used to predict the density and bulk sound velocity jumps in the phase transformation from Mg 2SiO 4 spinel to MgSiO 3 perovskite plus MgO periclase at high-temperature and high-pressure conditions corresponding to the 660 km seismic discontinuity in the mantle. The simulated density and bulk sound velocity jumps are then compared with seismological models reported for the 660 km discontinuity. The MD simulation for a pyrolite composition (60 vol.% spinel) is found to be compatible with a recent model SF99 [Shearer and Flanagan, Science 285 (1999) 1545] within nearly 1 σ limit for both density and bulk sound velocity jumps. The MD-simulated bulk sound velocity jump for a piclogite composition (40 vol.% spinel) is also consistent with SF99 within 1 σ, while the MD density jump for the piclogite lies outside the SF99 data. Our MD computed density and bulk sound velocity jumps, either for the pyrolite or the piclogite composition, differ substantially from the values by the PREM or the ak135 model.