Melilite- and Leucite-Bearing Systems - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 318

10.3 Experimental Study of the Joins Forsterite Diopside

— —

Leucite and Forsterite Akermanite

up to 2.3 GPa [ P (H 2 O) = P (Total)] and Variable
Temperatures

Leucite

— —

10.3.1 Introduction

The four essential minerals of many high-K ma c igneous (kama-

fugitic) rocks are leucite, augite, olivine, and melilite. The bulk rock compositions
of these rocks lie within the phase volumes of forsterite (Fo) - diopside (Di) - leucite
(Lc)

c and ultrama

akermanite (Ak), and melting phase relationships of this system is thus
applicable to the understanding of the origin of high-K ma

-

c and ultrama c igneous

rocks (Yoder 1986). The phase volume of Fo Di Lc Ak is a part of the larnite

- - -

(La) silica tetrahedron (Fig. 10.14 ). Phase equilibria in this

larnite-based basaltic tetrahedron have been studied for last several decades at
atmospheric pressure (Schairer and Bowen 1938; Luth 1967; Gupta 1972; Yoder
1986; Veksler et al. 1998).
Phlogopite is the most abundant hydrous liquidus mineral in high-K ma

forsterite kalsilite

- - -

c and

ultrama c igneous rocks and much attention has been paid to the melting phase

relationships of phlogopite-bearing ma

c igneous rocks (ex. Barton
and Hamilton 1979; Arima and Edgar 1983a, b; Foley et al. 1987; Foley 1992;

c and ultrama

Fig. 10.14 The joins
Fo Di Lc and Fo Lc Ak as a

- - - -

part of the La Qz

tetrahedron (after Yoder
1986). Abbreviations are
given in text

Fo Ks

- - -