The Composition of near-solidus melts of peridotite in the presence of CO₂ and H₂O between 40 and 60 kbar

Partial melting experiments at 40, 50 and 60 kbar pressure on three peridotite compositions with 0.5-0.63 wt.% H₂O and 2.0-3.2 wt.% CO₂ added indicate melting temperatures only marginally above continental geotherms. Most experiments were performed on a composition with 1.5 wt.% K₂O added, which causes a further decrease of about 40°C in melting temperature. Melts progress gradually from carbonate-rich to carbonated silicate in composition: near-solidus melts have Ca/(Ca + Mg) of 0.46-0.53, which fall to 30 wt.%) and Al₂O₃ (9 wt.%) and concomitant decrease in CaO (>20 to 20wt.% SiO₂, are only mildly enriched in trace elements, and will not cause large time-integrated isotopic in-growth except over long geological time intervals. The temperature interval over which melts are carbonatitic with SiO₂ contents