No liquid immiscibility in the system MgSiO3-SiO2 at 5.0 GPa
نویسنده
چکیده
A b s t r a c t L i q u i d u s phase relationships in the system MgSiO3-SiO2 at 5.0 GPa have been determined using a multianvil apparatus. Compared to phase relationships at 1 atm, the MgSiO3-SiO2 phase diagram at 5.0 GPa is significantly different in two respects. First, the composition of the eutectic between MgSiO3 and SiO2 moves from 65.0 wt% SiO2 at 1 atm/1547°C (protoenstatite-cristobalite eutectic; Bowen and Andersen, 1914) to 68.8 wt% SiO2 (orthoenstatite-coesite eutectic) at 5.0 GPa/1930°C. Second, no stable two-liquid field is present in the MgSiO3-SiO2 system at 5.0 GPa. The unbroken coesite liquidus curve is inflected indicating the presence of a submerged, metastable miscibility gap below the liquidus. Thus, although the temperature of the solvus critical point is likely to increase with pressure, the dT/dP slope of the SiO2 liquidus is much steeper and as a result, the immiscibility dome has become submerged completely. The reduction in liquid immiscibility in the MgSiO3-SiO2 system at 5.0 GPa implies that in more complex systems relevant to the Earth, immiscibility will also be suppressed at high pressures. Copyright © 1997 Elsevier Science Ltd
منابع مشابه
Self-consistent thermodynamic description of silicate liquids, with application to shock melting of MgO periclase and MgSiO3 perovskite
S U M M A R Y We develop a self-consistent thermodynamic description of silicate liquids applicable across the entire mantle pressure and temperature regime. The description combines the finite strain free energy expansion with an account of the temperature dependence of liquid properties into a single fundamental relation, while honouring the expected limiting behaviour at large volume and hig...
متن کاملStructure, thermodynamic and transport properties of liquid MgSiO3: Comparison of molecular models and laboratory results
Liquid MgSiO3 is a model for the Earth’s magma ocean and of remnant melt present near the core–mantle boundary. Here, models for molten MgSiO3 are computed employing empirical potential molecular dynamics (EPMD) and results are compared to published results including two EPMD studies and three first-principles molecular dynamics (FPMD) models and to laboratory data. The EPMD results derived fro...
متن کاملTHE SYSTEM DIOPSIDE – FORSTERITE – ENSTATITE AT 5.1 GPa: A TERNARY MODEL FOR MELTING OF THE MANTLE¶
Data determined using a multianvil press are given for liquidus phase relations in the system diopside – forsterite – enstatite (CaMgSi2O6 – Mg2SiO4 – MgSiO3) and extend for a limited distance into the larger ternary system diopside – forsterite – quartz at 5.1 GPa. In the system diopside–enstatite, which cuts across the system diopside – forsterite – quartz and divides it into two smaller tern...
متن کاملMelting phase relations in the MgSiO3–CaSiO3 system at 24 GPa
The Earth’s lower mantle is composed of bridgmanite, ferropericlase, and CaSiO3-rich perovskite. The melting phase relations between each component are key to understanding the melting of the Earth’s lower mantle and the crystallization of the deep magma ocean. In this study, melting phase relations in the MgSiO3–CaSiO3 system were investigated at 24 GPa using a multi-anvil apparatus. The eutec...
متن کاملDiamond formation in the deep lower mantle: a high-pressure reaction of MgCO3 and SiO2
Diamond is an evidence for carbon existing in the deep Earth. Some diamonds are considered to have originated at various depth ranges from the mantle transition zone to the lower mantle. These diamonds are expected to carry significant information about the deep Earth. Here, we determined the phase relations in the MgCO3-SiO2 system up to 152 GPa and 3,100 K using a double sided laser-heated di...
متن کامل