System CaO-MgO-Al₂O₃-SiO₂ Undersaturated with Silica

Abstract

Despite being relatively simple, the CMAS system represents a good approximation to complex mantle compositions, since its phase relations resemble closely the phase relations observed in mantle materials, and include all important phases occurring in the Earth’s mantle. At the same time, the system is complex enough to serve as a good starting point for petrologic applications, such as the thermobarometry of mantle xenoliths and metamorphic rocks, and for understanding the mineralogy, chemistry, and structure of the deep Earth. The importance of the CMAS system is evident from the amount of time and effort devoted to the experimental investigation of the corresponding phase relations and to the measurement of the thermochemical, physical, and structural properties of the participating phases.