Geology Reference
In-Depth Information
Fig. 10.18 The
flow-sheet diagram showing paragenetic relationship of various assemblages in
the join Fo
H
2
O studied under 2.3 GPa variable temperatures. In drawing the
ow-sheet
diagram it has been assumed that liquid + vapour observed in the products were present as
uid
elevated P-T
Di
Lc
-
-
-
T condition. It should be pointed out
that
the
flow sheet diagram for the join
-
forsterite
leucite
-
å
kermanite
H
2
O should be
…
this diagram. There is some difference in that the
-
-
univariant line (Fo + Di + Ph + f) in the Fo
H
2
O join is derived from the invariable
(Fo + Mer + Di + f). As merwinite reacts with the liquid and is eliminated, the melt composition
follows a divariant surface (Fo + Di + f) an moves along the univariant line (Fo + Ph + Di + f) and
finally moves towards the point
-
Lc
-
Ak
-
'
X
'
(Ph + Kf + Di + Fo + f) (after Nag et al. 2007)
this and presence of some components as solid solution in different phases, the
system in effect behaves as a four-component system. On these assumptions, a
flow-sheet diagram is drawn, as shown in Fig.
10.18
. This helps us to draw the
paragenetic sequence in the four-component system (Fig.
10.16
b, c) and also near
the points
'
N
'
and
'
O
'
(Fig.
10.17
b, c). At the invariant point
'
X
'
(975
±
10
°
C,
Fig.
10.18
), the number of phases is
ve (Fo
ss
+Di
ss
+Ph
ss
+Kf
ss
+ f) as expected
for a four-component system. Following the Scheinemaker
'
s rule there should be
four univariant
lines leading to the
five phase invariant point
'
X
'
. The four
univariant lines should be Fo
ss
-
Di
ss
-
Ph
ss
-
f, Kf
ss
-
Di
ss
-
Fo
ss
-
f, Kf
ss
-
Ph
ss
-
Fo
ss
-
f and
Ph
ss
-
f.
Likewise, the
Kf
ss
-
Di
ss
-
(Fig.
10.16
)
comprises Ph
ss
,Ks
ss,
Kf
ss,
Di
ss
and f, requires that there should be four univariant
lines namely: (1) Kf
ss
-
Ph
ss
-
Ks
ss
-
f, (2) Ph
ss
-
Kf
ss
-
Di
ss
-
f, (3) Kf
ss
-
Di
ss
-
Ks
ss
-
f,
five-phase invariant assemblage near the point
'
D
'
Search WWH ::
Custom Search