Phase Relations in the System Leucite-Akermanite-Albite-SiO2
In certain ultrapotassic petrographic provinces such as Somma-Vesuvius (Savelli, 1967, Cioni et al. 1995), Coli-Albani (Aurisicchio et al., 1988) and Vico, all localities from Italy (Cundari and Mattias, 1974), Bufumbira region of East Africa (Holmes and Harwood, 1937; Rogers et al. 1998) and Highwood Mountains, Montana , U.S.A. (O`Brien et al. 1991), leucite-bearing SiO2 -undersaturated rocks are associated with highly silicic, potassium-rich (K2O ≥ 3 wt%) feldspathic rocks.