The system diopside-acmite-nepheline at low oxygen fugacity

Abstract

Nepheline component (NaAlSiO4, 20 wt.%) was added to the join diopside(CaMgSi2O6)-acmite(NaFeSi2O6) and the phase relations were determined at 10-12 atm fO2 and 1050-1300°C. The liquidus lines for wustite and clinopyroxene cross each other at about 1160°C and the composition of Di24Ac56Ne20. The field of clinopyroxene + wustite + liquid extends from Di15Ac75Ne20 to Di40AC40Ne20 at 1050°C. In the Di-rich region the phase relations are complicated. Olivine appears as second phase, but disappears at lower temperatures (<1100°C). Melilite (<1200°C) and nepheline (<1150°C) are present at lower temperature region and coexist with olivine and/or clinopyroxene. -Authors