Melilite- and Leucite-Bearing Systems - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 330

with forsterite ss + leucite ss + kermanite ss +liq, can be derived from a monticellite

alnoite, a melilite italite or an olivine italite. The assemblage at 2.3 GPa shows that
katungite has heteromorphic relation to olivine-bearing madupite (

å

' N ' ), minette

( final assemblage

might correspond to katungite. The univariant equilibrium involving reaction (2)
(Ph = 3Fo + Lc + Ks + V) has been identi

' O ' ) or kalsilite minette P (Fig. 10.17 b). At low pressure, the

ed by Holmes (1942), who described

lava flows containing clinopyroxene, kalsilite, olivine, melilite and leucite from the

western limb of the African Rift valley system (also see Yoder 1986).
In summary the experimental data of Nag et al. demonstrated that high pressure
crystal differentiation can produce various types of K-rich ma

c
igneous rocks. The data of Nag et al. suggest that olivine leucitite (ugandite) can be
derived from an olivine italite. The paragenetic relationship was also inferred for
phlogopite-bearing madupite, pyroxene-bearing minette and kalsilite-bearing mi-
nette. The data further suggest that katungite has heteromorphic reaction to olivine-
bearing madupite, pyroxene-bearing minette and kalsilite-bearing minette. The
phlogopite-bearing clinopyroxenite xenoliths commonly found in kamafugitic
rocks (cf. Lloyd and Bailey 1975; Lloyd et al. 2002) would probably represent high
pressure crystallization product derived from kamafugitic magmas.

c and ultrama