Geology Reference
In-Depth Information
Fig. 10.6 Phase relation
in the join diopside
-
nepheline
-
akermanite
at 1 atmosphere
(after Onuma and Yagi 1967)
DIOPSIDE
1391.5
0
Di
ss
A
1258
0
F
0
1365 C
1212
0
G
50
50
Fo
0
B
H
1169 C
Mel
1193
0
C
Ne
ss
Cg
ss
0
1526
0
1454 C
V
DE
50
NEPHELINE
CARNEGIEITE
AKERMANITE
Weight Per Cent
Fig. 10.7 Phase relation in
the join diopside
DIOPSIDE
1391.5
0
nepheline
-
leucite at 1 atmosphere (after
Gupta and Lidiak 1973)
-
Di 60
0
Ne 8
Lc 32
Di 27.5
Ne 29.5
Lc 43
+
A(1275
-
5C)
Di
ss
0
+
B(1194
-
5)
1258
0
1302
0
A
50
50
1193
0
B
Lc
ss
Cg
ss
0
1686
0
1526 C
VVVVVVVVV
1325
0
NEPHELINE
CARNEGIEITE
LEUCITE
50
forsterite
ss
coexist with liquid. In this join, the assemblage forsterite
ss
+ nephe-
line
ss
+ diopside
ss
+ leucite
ss
+ liquid is reached between 1,168 and 1,100
C. Then
forsterite
ss
reacts with liquid to be completely consumed. The temperature of dis-
appearance for this phase varies: 1,135
°
±
10
°
C (near point A), 1,060
±
10
°
C (near
point, B) and 950
final assemblage in
this join consists of melilite + diopside
ss
+ nepheline
ss
+ leucite
ss
. The course of
crystallization of liquid in this join is shown by Fig.
10.8
, and the rock nomen-
clature diagram corresponding to Fig.
10.9
.
Gee and Sack (1988) performed experiments on a melilite nephelinite collected
from Nyiragongo, Zaire. They added additional amount of akermanite, leucite,
nepheline and olivine to this sample. The experiments were conducted under QFM
±
10
°
C near the join diopside
nepheline. The
-
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