Ternary Systems with Feldspathoids - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 264

Fig. 7.9 Plots of the rock compositions in the albite — K-feldspar - nepheline - kalsilite quadrilat-
eral. The compositional plots near the eutectic E 1 are taken from Washington (1917), Eby et al.
(1998), Jones and Larsen (1985) and Snavely et al. (1976). The compositional plot near eutectic E 2
is after Savelli (1967), Wallace and Martin (1990) and Ageeva et al. (2004). The compositional
plots near the jadeite end are from Okey (1997). Compositions of rock samples from Brasil are
taken from Brotzu et al. (1989). The position of the ternary eutectic E3 is after Huang And Wyllie
(1975)

convex toward nepheline. In the khibiny massif of Kola Peninsula, the nal

assemblage is nepheline kalsilite syenite. According to Ageeva and Borutzky

(2004), these rocks show an intergrowth of kalsilite with nepheline or orthoclase,
and in which, the cubic habit of primary leucite is absent. The absence of Leucite
and the presence of an intergrowth of kalsilite and K-feldspar suggest that these
rocks crystallized at least at a depth of 60

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65 km.
Hamilton and Mackenzie (1965) selected 102 compositions of plutonic nephe-
line syenitic rocks from Washington (1917). These compositions were recalculated
to 100 % in terms of nepheline, kalsilite and quartz (total modal per cent of which
exceeds 80 %) by them. Analytical data for nepheline syenites published by various
other authors were considered by Gupta et al. The analytical data of following
investigators were included: Eby et al. (1998), Jones and Larsen (1985), Snavely

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