Mineralogy - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 21

Fig. 2.4 Phase relations along the join albite K-feldspar determined at 2 GPa [P(H 2 O) = P

(Total)] and various temperatures (after Gupta et al. 2010)

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Fig. 2.5 Phase relations along the join nepheline - albite determined at 2 GPa [P(H 2 O) = P(Total)]
and various temperatures (after Gupta et al. 2010)

2.3 Plagioclase

Plagioclase is a common mineral in leucite-bearing tephrites, basanites, tephritic
phonolites and phonolitic tephrites of Vulsini, Vico, Sabatini and Somma-Vesuvius
volcanic complexes, but it is absent in all lamproitic rocks. It is also found in the
leucite-bearing rocks of Manchuria (China), Utsuryo islands (Korea) and Tristan da
Cunha Islands. Plagioclase coexisting in equilibrium with leucite is calcium-rich