The Systems CaSiO3–CaF2 and Ca0.5Mg0.5SiO3–CaF2 at 6 GPa

Abstract The present work is devoted to the experimental study of phase relations in the CaSiO 3 –CaF 2 and Ca 0.5 Mg 0.5 SiO 3 –CaF 2 systems under mantle pressure. The experiments were run on a multianvil press in graphite capsules. At 6 GPa, both systems have an eutectic type of phase diagram. The breyite-fluorite eutectic is established at 1200°C and 37 mol % CaF 2 (14 wt % F). The diopside-fluorite eutectic is situated at 1300°C and 58 mol % CaF 2 (23 wt % F). Considering the melting points of breyite, 1750°C, and diopside, 1940°C, a presence of CaF 2 suppresses the silicate solidus by 550–640°C and yields formation of fluorine-rich Ca or Ca–Mg silicate melts under temperature conditions corresponding to the continental geotherms with a surface heat flux of 37 and 39 mW/m 2 , respectively, at a depth of 180 km.