Geoscience Reference
In-Depth Information
Table 1.4
Concentration of various trace elements (in ppm) in different materials. CI
=
Orgueil-type
chondrites, BSE
=
Bulk Silicate Earth.
T
cond
is the 50 percent condensation temperature
Carbonaceous
chondrites (CI)
Ordinary
chondrites
Continental
crust
MORB
basalt
Hawaiian
basalt
T
cond
BSE
K
1000
558
798
240
15772
848
12200
Ti
1549
436
617
1205
4197
8513
1.7
Rb
1080
2.3
3.0
0.600
58
1.26
2.1
Sr
-
7.8
10.7
19.87
325
113.2
221
Y
1592
1.56
2.10
4.30
20
35.82
19.5
Zr
1780
3.94
6.03
10.47
123
104.24
108
Nb
1550
0.246
0.38
0.658
12
3.51
8.3
Ba
-
2.34
4.23
6.600
390
13.87
60.2
La
1520
0.2347
0.31
0.648
18
3.90
6.808
Ce
1500
0.6032
0.88
1.675
42
12.00
17.56
Pr
1532
0.0891
0.126
0.254
5
2.074
2.81
Nd
1510
0.4524
0.66
1.250
20
11.18
13.74
Sm
1515
0.1471
0.193
0.406
3.9
3.75
3.665
Eu
1450
0.056
0.076
0.154
1.2
1.335
1.246
Gd
1545
0.1966
0.304
0.544
3.6
5.077
3.93
Dy
1571
0.2427
0.353
0.674
3.5
6.304
3.61
Er
1590
0.1589
0.236
0.438
2.2
4.143
1.738
Yb
1455
0.1625
0.215
0.441
2.0
3.90
1.426
Lu
1597
0.0243
0.032
0.0675
0.33
0.589
0.203
Hf
1652
0.104
0.167
0.283
3.7
2.97
2.548
Ta
1550
0.0142
0.023
0.0372
1.1
0.192
0.679
Pb
-
2.47
0.305
0.150
12.6
0.489
0.633
Th
1545
0.0294
0.043
0.0795
5.6
0.187
0.527
U
1420
0.0081
0.013
0.0203
1.42
0.071
0.181
13. Equilibrium of silicate melts can be described by the reaction
2O
−
⇔
O
2
−
+
O
0
(1.5)
in which O
0
,O
−
, and O
2
−
stand for bridging (Si-O-Si), singly bonded (Si-O) and free
oxygen, respectively. Assuming that one mole of melt is produced from
X
SiO
2
moles
of silica and (1
X
SiO
2
) mole of metal oxide MO, calculate the mole fractions of
O
0
,O
−
, and O
2
−
with the assumption that the reaction above can be described by the
equilibrium constant.
−
