Leucite tephrite, leucite basanite, and potassic ankaramite are the rock types recognized in the highly potassic undersaturated volcanic rocks forming gravitatively differentiated lava flows in north Johore, Malaysia. The flows are intruded by thin shoshonitic dikes and a large undifferentiated shonkinite sill. Both the lavas and hypabyssal intrusions are probably Tertiary in age. Modal and chemical analyses are presented. It is concluded that the parent magma was close to a biotite pyroxenite in composition and possibly the hybrid product of assimilation of peridotite by granite.

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