The System KCl–CaCO3–MgCO3 at 3 GPa

Inclusions in mantle minerals and xenoliths from kimberlites worldwide derived depths exceeding 100 km vary composition alkali-rich saline to carbonatitic. Despite the wide distribution of these melts their geochemical importance as metasomatic agents that altered mineralogy geochemistry rocks, P-T range stability remains largely undefined. Here we report new experimental data on phase relations system KCl–CaCO3–MgCO3 at 3 GPa obtained using a multianvil press. We found KCl–CaCO3 KCl–MgCO3 binaries have eutectic type T-X diagrams. The KCl-calcite is situated K2# 56 1000 °C, while KCl-magnesite located 79 1100 where = 2KCl/(2KCl + CaCO3 MgCO3) × mol%. Just below solidus, divided into two partial ternaries: KCl magnesite dolomite calcite–dolomite solid solutions. Both ternaries start melt near °C. minimum liquidus/solidus surface corresponds Ca0.73Mg0.27CO3 K2#/Ca# 39/73, Ca# 100∙Ca/(Ca Mg) At bulk ≤ 68, melting controlled by ternary peritectic: liquid with 40/68. Based our present previous data, reaction, expected control solidus KCl-bearing carbonated eclogite, passes through °C 1200 6 crossovers 43-mW/m2 geotherm depth 120 37-mW/m2 190 km.