Liquid immiscibility in a nephelinite–carbonate system at 25 kbar and implications for carbonatite origin

摘要: Mantle-derived carbonate-rich melts may have an important role in mantle metasomatism, and serve as parent liquids for crustal carbonatite magmas. Experiments shown that carbonatitic can be produced by partial melting of peridotite + CO_2 H_2O above 22 kbar (ref. 3), silicate carbonate are immiscible between 2 15 a wide range Ca/Na ratios. We determined the extent silicate-carbonate liquid immiscibility at 25 1,050–1,300°C using mixtures magnesian nephelinite, dolomite sodium with without water. In contrast to low-pressure data, two-liquid field is restricted more sodium-rich compositions, far removed from natural melts. Our experimental results suggest neither carbonated peridotite, nor extensive fractional crystallization magmas depths corresponding kbar, likely generate immiscibility.