Elastic properties of hydrous ringwoodite (γ-phase) in Mg2SiO4

Thermal, hydrous, and mechanical states of the mantle transition zone beneath southern Africa

“…5). A water-saturated mantle would reduce the bulk sound velocities of wadsleyite and ringwoodite by V3.7% [47] and V4.0% [48], respectively, several times greater than the observed velocity anomaly. For comparison, a 600^800-K reduction in mantle temperature in the transition zone would increase seismic velocity by a similar magnitude [49].…”

Isothermal compressibility of hydrous ringwoodite and its relation to the mantle discontinuities

“…The coarse grains (,,,100 microns) of hydrous ringwoodite are clearly distinct from the other phases under a microscope. The H20 content of the present hydrous ringwoodite was analyzed by a secondary ion mass spectrometry (SIMS: Cameca IMS-3F) and found to be 2.8 q-0.2 wt%, which is a higher H20 content than that of a sample used for Brillouin spectroscopy (2.2 q-0.2wt% of H20) [Inoue et al, 1998]. The electron probe microanalysis (EPMA: JOEL JXA8800) shows Mg/Si ratio of 1.88 q-0.2, which also gives 2.7 q-0.9 wt% as the …”

“…We indicated that even a small amount of H20 will considerably lower the bulk modulus. Recently, it has also been confirmed that the ringwoodite phase may contain a significant amount of H20 exceeding 2 wt% [Kohlstedt et al, 1996;Inoue et al, 1998]. If the H20 in hydrous ringwoodire has a great influence on the bulk modulus, we have to reconsider the elastic properties of the mantle discontinuities, such as the 660 km and 520 km discontinuities.…”

First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure

“…Although elastic moduli of hydrous wadsleyite and hydrous ringwoodite have recently been measured by Brillouin spectroscopy at ambient condition [Mao et al, 2008;Inoue et al, 1998], such information is still very limited at the transition zone pressure and temperature conditions.…”