Geology Reference
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Fig. 11.8 Flow-sheet diagram summarising the course of crystallisation of liquid in the system
akermanite-leucite-albite-SiO 2 at 1 atm (after Gupta and Gupta 1997)
wollastonite-pyroxene-trachyte (m
j). Association of wollastonite with pyroxene,
melilite and leucite has been discussed by Stoppa (1988) from Colli Fabbri, Spo-
teto, Italy. The
-
flowsheet diagram (Fig. 11.8 ) also shows that a wollastonite-
pyroxene rhyolite can be derived from a wollastonite-pyroxene tridymite lava
(g
(f-k), a pyroxene-bearing rhyolite (f
(f-k), a wollastonite-rhyolite (h
(f-k), or a wol-
-
-
-
lastonite-pyroxene trachyite (m
k). If a small amount of FeSiO 3 is present in the
-
system, the assemblages along a
i (melilite leucitite), b-i
i (melilitite), c-i
i (melilite
-
-
-
leucitite) and l-i
-
l-i (leucitite) should be represented by simpli
ed rock types as shown
within the brackets. In case of a
-
l-i the pyroxenes are hedenbergitic but along l-i
-
i and
b
i pyroxenes are diopside-hedenbergite solid solutions.
With addition of FeSiO 3 , similarly the assemblages along m-j and e-j should be
pyroxene trachyte and pyroxene phonolite. Pyroxenes in these cases are diopside-
hedenbergite solid solution. In case of both e
-
i pyroxene are diopsidic.
If FeO is added in the system, the assemblages along g
j and c
-
-
k (pyroxene-tridymite
lava), h - f-k (hedenbergitic rhyolite) and f - f-k (pyroxene rhyolite) and m - k (pyroxene
trachyte) should be represented by simpli
-
ed rock types as mentioned in the
bracket. Along h
k pyroxene is hedenbergitic.
-
 
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