Liquidus phase relationships in the system KAlSi₃O₈-CaAl₂Si₂O₈-KAlSiO₄ at P(H₂O) = 5 kbar Available to Purchase

Liquidus phase relationships in the system KAlSi₃O₈-CaAl₂Si₂O₈-KAlSiO₄ (Or-An-Ks) have been determined for low anorthite contents (<20 wt% An) at a pressure of H₂O of 5 kbar. A temperature maximum occurs on the plagioclase + leucite field boundary, and two ternary eutectics have been defined: the assemblage plagioclase + kalsilite + leucite + liquid at 735 °C at the composition of Q₂₁An₁₄Ks₆₅, and the assemblage alkali feldspar + plagioclase + leucite + liquid at the composition Q₂₈An₈Ks₆₄, at a temperature slightly higher than 735 °C. Fractionation trends in the high-K, silica-undersaturated rocks from the Roccamonfina complex of the Roman Volcanic Region, Italy, may be partially explained by phase relationships in the system Q-An-Ks at P(H₂O) on the order of 5 kbar, or at a higher total pressure and H₂O-undersaturated conditions. However, Na-bearing normative components in these rocks are also important to the interpretation of fractionation trends.