Publication Date:
2016-09-15
Description:
We report an experimental study of the phase diagrams of MgO, MgSiO 3 and Mg 2 SiO 4 at high pressures. We measured the shock compression response, including pressure-temperature Hugoniot curves of MgO, MgSiO 3 and Mg 2 SiO 4 between 0.2-1.2 TPa, 0.12-0.5 TPa and 0.2-0.85 TPa respectively, using laser-driven decaying shocks. A melting signature has been observed in MgO at 0.47 ± 0.04 TPa and 9860 ± 810 K, while no such phase changes were observed either in MgSiO 3 or in Mg 2 SiO 4 . Increases of reflectivity of MgO, MgSiO 3 and Mg 2 SiO 4 liquids have been detected above 0.55 TPa (12760 K), 0.15 TPa (7540 K), 0.2 TPa (5800 K), respectively. In contrast to SiO 2 , melting and metallization of these compounds do not coincide, implying the presence of poorly electrically conducting liquids close to the melting lines. This has important implications for the generation of dynamos in super-Earth's mantles.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics