3:15 PM - 3:30 PM
[R1-06] Occurrence and genesis of Ca-rich nepheline and associated minerals in the Kajishiyama basanite, Tsuyama, Okayama Prefecture, SW Japan
[Presentation award entry]
Keywords:Nepheline, Basanite, Apatite, Calcic
Nepheline is a feldspathoid mineral, and the ideal formula is shown as K2Na6Al8Si8O32 (Z = 1). We found Ca-rich nepheline containing Ca up to 0.467 apfu from Kajishiyama basanite. Coexisted apatite was crystallized before crystallization of nepheline, and there is a negative correlation between P content of whole rock composition and Ca content of nepheline. Therefore, it is possible that in low P basanite magma, the amount of crystalized apatite is few, residual melt becomes high Ca, and Ca-rich nepheline is formed.