Melting and decomposition of MgCO3 at pressures up to 84 GPa

Abstract

Magnesium carbonate MgCO3 (magnesite) was experimentally studied at pressures of 12–84 GPa and temperatures between 1,600 and 3,300 K. We applied the high-pressure technique using a multianvil press and a diamond anvil cell with laser heating. The phase relations and melting of magnesite were investigated by means of Raman and time-resolved multi-wavelength spectroscopy. Magnesite is found to melt congruently within the entire studied pressure range at temperatures of 2,100–2,650 K. At temperatures above 2,700 K, we observed decomposition of magnesite with formation of MgO and a carbon phase (diamond). Our results demonstrate that at high pressures, the magnesium carbonate melt can exist at a wide range of thermodynamic conditions.