Open Session - SWISS GEOSCIENCE MEETINGs

8
Symposium 2: Mineralogy-Petrology-Geochemistry
]
%
t
w
[
T ot
F e
TiO [ wt%
]
2
20
18
16
14
12
10
8
6
4
2
0
4
3
2
1
0
Chelan complex
1 Gpa (Kägi 2000)
1.5 Gpa (Alonso 2006)
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Mg*
]
%
t
w
[
Al O 2 3
C aO
[ wt%
]
22
20
18
16
14
12
10
8
6
4
2
18
16
14
12
10
8
6
4
2
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Figure 1: Comparison between whole rock analyses and experiments at 1.0 GPa (black dashed line, Kägi, 2000) and 1.5 GPa (grey dashed
line, Alonso Perez, 2006).
2.11
Experimental re-determination of initial melting in the system calcite-
H 2 O at 100 MPa and calcite/melt element fractionation
Durand Cyril* and Baumgartner Lukas*
*Institut de Minéralogie et Géochimie, Université de Lausanne, BFSH2, CH-1015 Lausanne (cyril.durand@unil.ch)
The study investigates the partial melting of calcite in the presence of water. We determined the temperature of initial melting
in the binary calcite-H 2 O system using rapid vertical quench equipment, as well as the partitioning of elements between
calcite and melt for major and trace elements. The classic studies of Wyllie and Tuttle (1959; 1960) placed initial melting at
ca. 740°C at 100 MPa. Hence partial melting in contact metamorphic terrains was predicted to be possible, though difficult.
Field studies (Wenzel et al., 2002; Jutras et al., 2006) and discussions (Lentz, 1998, 1999) have suggested that partial melting
does occur.
Vertical rapid-quench cold-seal pressure vessels were used. Temperature was measured with external NiSil-thermocouples,
resulting in an estimated 5°C uncertainty. Powders were sealed into gold capsules along with variable amounts of water.
Natural calcite and synthetic reaction grade calcite (>99.5%, Alfa Aesar, lot C24Q27) were used. Run times varied between
1.5h and 90h. Melting was identified by SEM and EMP. Unequivocal initial melt textures were the formation triple junction
Mg*