Geoscience Reference
In-Depth Information
4000
150
hcp-Fe Ma
et al
. (2004)
hcp-Fe Williams
et al
. (1987)
Kamada (2011)
123 GPa, 16(4)
at.%
3000
Fe -18 wt % Si alloy
Asanuma
et al
. (2010)
hcp-Fe
Boehler (1993)
100
Kamada
et al
.
(2010), 85.6
GPa, 19.6 at.%
2000
FeSi Santamaria-Perez and Boehler (2008)
γ
hcp-Fe Ma
et al
. (2004)
1000
Morard
et al
.
(2008) 42 GPa
19.9 at%
ε
50
α
Stewart
et al
.
(2007) 40 GPa
19.2 at.%
0
50
100
150
Pressure, GPa
Li
et al
. (2001)
25 GPa 23 at.%
Fig. 8.6
The melting curves of hcp-Fe and Fe-Si alloy.
Significant discrepancy exists in the melting curves of
Fe at high pressure (Williams
et al
., 1987; Boehler,
1993; Ma
et al
., 2004).
0
0
10 20 30
Eutectic comp., at.% Sulfur
Fig. 8.8
The eutectic compositions of the Fe-S system
at various pressures. 23 at % S at 25 GPa (Li
et al
.,
2001); 19.2 at % at 40 GPa (Stewart
et al
., 2007); 19.9 at
%at42GPa(Morard
et al
., 2008); 19.6 at % at 85.6
GPa (Kamada
et al
., 2010); 16 at % at 123 GPa (Kamada
et al
., 2011).
Boehler (1993)
3000
FeS
Fe-FeS
2000
Campbell
et al
.
(2007)
but above 10-15 GPa it increases with increas-
ing pressure. The effect of change with pressure
is caused by the FeO component having differ-
ent compressibility values in magnesiow ustite
and liquid iron; i.e., FeO is more compressible in
molten iron. The new experimental data, together
with results from previous studies obtained over a
wide P-T range (2-139 GPa, 2273-3150 K), were
fitted by a thermodynamic model that enables
extrapolation to the conditions of the outer core.
Assuming core-mantle equilibrium, the results
show that the outer core is undersaturated in O,
which causes a thin layer strongly depleted in FeO
at the base of the lower mantle. They suggested
that O is likely to be the main light element in
the Earth's core (e.g. 7%-8 wt% O).
Terasaki
et al
. (2011) determined both the
solidus and liquidus temperatures of the Fe-S-O
system up to 128 GPa. Figure 8.9 shows a phase
diagram of the Fe
75
O
5
S
20
composition in the
Fe-FeO-FeS system (Terasaki
et al
., 2011). The
solidus curve determined here is almost the same
as that of the Fe-Fe
3
S system (Campbell
et al
.,
Chudinovskikh & Boehler
(2007)
1000
Li
et al
. (2001)
0
0
20
40
60
80
Pressure, GPa
Fig. 8.7
The melting curve of FeS (Boehler, 1993) and
the eutectic temperature of the Fe-S system (Boehler,
1993; Campbell
et al
., 2007; Chudinovskikh &
Boehler, 2007).
a melt. After quenching, he observed the appear-
ance of Fe
3
S and hcp-Fe. Repeated appearance
of Fe
3
S during the temperature cycle confirmed
melting of the system under the pressure and
temperature conditions.
Asahara
et al
. (2007) reported new data on par-
titioning of FeO between magnesiow ustite and
liquid iron over a wide pressure and temper-
ature range (3-25 GPa and 2273-3200 K). The
amount of FeO partitioned in liquid iron de-
creases with increasing pressure below 10 GPa,
