Melting of clinopyroxene + magnesite in iron-bearing planetary mantles and implications for the Earth and Mars

摘要: The assemblage clinopyroxene + magnesite was observed in Earth’s high-pressure metamorphic samples, and its stability subducting slabs confirmed by experiments. Recent studies also suggested that the fO2 variations SNC meteorites can be explained polybaric graphite-CO-CO2 equilibria Martian mantle. Although there is no direct evidence for of cpx mc Mars mantle, high-pressure–high-temperature decomposition to fo CO2 makes it a good analogue source carbon metasomatism, particular, study nakhlites formation. Iron, which present mantles, may, however, influence speciation carbon. We performed experiments on at 1.8 3.0 GPa temperatures corresponding mantles. role iron investigated (1) replacing all or part siderite FeCO3, (2) adding Fe0 (3) using graphite C capsules. A carbonate-silicate melt forms both Earth conditions. Clinopyroxene olivine are main solid phases iron-free Fe2+ decrease their melting increase silicate fraction melt. produced melts may involved formation some carbon-rich lavas (e.g., carbonatites, ultramafic lamprophyres, kamafugites). Our results used interpret ophiolite samples inclusions. In we show wustite form equilibrium with opx-(and silica-) poor regions mantle below 3 GPa. confirm hypothesis metasomatism source. Immiscibility reduction could explain absence rarity lavas.