Melt Composition and Phase Equilibria in the Eclogite-Carbonate System at 6 GPa and 900–1500 °C

Melting phase relations in the eclogite-carbonate system were studied at 6 GPa and 900–1500 °C. Starting mixtures prepared by blending natural bimineral eclogite group A (Ecl) with eutectic Na-Ca-Mg-Fe (N2) K-Ca-Mg-Fe (K4) carbonate (systems Ecl-N2 Ecl-K4). In system, subsolidus assemblage is represented garnet, omphacite, eitelite, a minor amount of Na2Ca4(CO3)5. Ecl-K4 includes clinopyroxene, K2Mg(CO3)2, magnesite. The solidus both systems located 950 °C controlled following melting reaction: Ca3Al2Si3O12 (Grt) + 2(Na or K)2Mg(CO3)2 (Eit) = Ca2MgSi3O12 [2(Na K)2CO3∙CaCO3∙MgCO3] (L). silica content (in wt%) melt increases temperature from < 1 to 3–7 1300 °C, 7–12 1500 Thus, no gradual transition kimberlite-like (20–32 wt% SiO2) carbonate-silicate occurs even as mantle adiabat. This supports hypothesis that high kimberlite result decarbonation low pressure. As Ca# ranges 58–60 42–46. infiltration such into peridotite should lower its causes refertilization harzburgite lherzolite wehrlitization.