Leucite- and Feldspar-Bearing Systems - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 290

Fig. 9.3 Liquidus phase
relations in the join
diopside - nepheline - sanidine
under 1 GPa [P(H 2 O) = P
(Total)] and variable
temperatures (Gupta et al.
2006)

Fig. 9.4 Liquidus phase
relations in join
dipside

Diopside

sanidine
under 2 GPa [P(H 2 O) = P
(Total)] and variable
temperatures (Gupta et al.
2006)

- nepheline -

Di ss

640 0

U

N

Ne ss

V V P

Nepheline

60 S 80

Sanidine

20 40

9.2.3 Petrological Signi cance

If a small amount of possible alumina (3 wt%) in diopside is ignored, then the join
diopside nepheline sanidine may be represented as a join of the system nephe-

- -

line SiO 2 system. Because of the incongruent melting phe-

nomenon of sanidine, there is a primary phase of leucite ss . Forsterite ss also appears

kalsilite CaO MgO

- - - -