Experimental Studies on K-Rich Rocks - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 407

Fig. 13.20 a Modal
proportions of phases in
experiments at 3.0 GPa. The
modes were calculated by the
least squares method using
microprobe analyses of all
phases (after Lloyd et al.
1985) b Modal proportions of
phases at 2.0 GPa. The modes
were calculated by the least
square method using
microprobe analyses (after
Lloyd et al. 1985). For
abbreviations see Table 13.1

(a)

1300

1250

ol

mgt

1200

0 20 40 60 80 100

Modal Proportion (vol%)

(b)

1300

1250

1200

0 20 40 60 80

Modal Proportion (vol%)

13.2.12 High P-T T Investigation on an Armalcolite-

Phlogopite Lamproite from Smoky Butte, Montana

-

Suprasolidus phase relations on an armalcolite-phlogopite lamproite (Table 13.2 )
was determined at pressures between 0.8 and 3.0 GPa and temperatures from 950 to
1,380 C by Edgar et al. (1992). Velde (1975) earlier described this armalcolite-

bearing phlogopite-diopside lamproite from Smokey Butte, Montana. The starting
material for the study was a glassy armalcolite-phlogopite lamproite (Fig. 13.21 )
from the chilled margin of a medium-grained lamproite from Smoky Butte, Mon-
tana. For abbreviations in Fig. 13.21 see Table 13.1 .

°