Revision of the CaMgSi2O6−CO2 P-T phase diagram at 3-6 GPa

12 In the present work, we reexamined the phase relationships in the system diopside‒CO 2 in the 13 range of 3-6 GPa and 850-1500 °C in multianvil experiments including reversal ones lasting up to 169 14 hours. The reaction CaMgSi 2 O 6 (clinopyroxene) + 2CO 2 (fluid) = 2SiO 2 (quartz/coesite) + 15 CaMg(CO 3 ) 2 (dolomite) passes through 3 GPa/950 °C with a slope of 6 MPa/°C and terminates at an 16 invariant point near 4.5 GPa/1200 °C, where carbonate liquid coexists with clinopyroxene, coesite, 17 dolomite and CO 2 fluid. The newly determined boundary has the equation P (GPa) = 0.006× T (°C) ‒ 18 2.7. As temperature increases to 1250 °C at 4.5 GPa, liquid, dolomite, and coesite disappear and 19 clinopyroxene coexists with CO 2 fluid. As pressure increases to 6 GPa, the solidus temperature 20 increases to 1300 °C revealing a slope of 15 MPa/°C. At 4.5 and 6 GPa, solidus melts contain about 21 1 wt% SiO 2 . As temperature increases to 1400 and 1500 °C at 6 GPa, the silica contents in the 22 carbonate melt increase to 6 and 13 wt%, respectively. Our data combined with that of Luth (2006)