Geoscience Reference
In-Depth Information
Table 2.3 Composition of a deep-sea sediment and
its mineral phases
Oxide
Sediment
Quartz
Clay
Carbonate
SiO 2
45.7
100
51.4
0
Al 2 O 3
13.2
0
26.4
0
CaO
16.5
0
0
55
Table 2.4 Concentration of Fe and Ni (wt%) in H and LL ordinary
chondrites and for the Bulk Silicate Earth (BSE).
Element
H
LL
BSE
Fe
27.5
18.5
6.3
Ni
1.6
1.0
0.020
Table 2.5 Concentrations of various cations in water samples (1-3) taken from
an estuary (
mol l −1 )
µ
Element
River
1
2
3
4
Seawater
2.20 × 10 2
1.07 × 10 5
2.13 × 10 5
3.20 × 10 5
4.26 × 10 5
5.33 × 10 5
Cl
1.69 × 10 2
1.05 × 10 4
2.08 × 10 4
3.11 × 10 4
4.15 × 10 4
5.18 × 10 4
Mg
4.93 × 10 1
1.34 × 10 1
4.0 × 10 2
1.5 × 10 2
8.3 × 10 3
Al
1.85
2.32 × 10 2
1.49 × 10 2
1.18 × 10 2
1.07 × 10 2
1.02 × 10 2
1.01 × 10 2
Si
3.75 × 10 2
2.36 × 10 3
4.35 × 10 3
6.34 × 10 3
8.33 × 10 3
1.03 × 10 4
Ca
7.14 × 10 1
9.75 × 10 2
1.41 × 10 2
2.77 × 10 3
1.24 × 10 3
1.03 × 10 3
Fe
test two extreme compositions, those of the H chondrites and LL chondrites. Use data
in Table 2.4 . For each case, find the abundances of Fe, Ni, and the sum of the other
elements.
6. Using the data of Appendix A and F a nd a spreadsheet, calculate the abundances of
various elements in the mean mantle by removing the amounts held in the continental
crust from the BSE inventory.
7. Table 2.5 gives the composition of water samples taken along an estuary. We assume
that, because of its high solubility, Cl is a good mixing indicator between fresh-
water and seawater. Plot the concentration of each element vs. [Cl] down the estuary.
Elements Al, Si, and Fe are considered to be non-conservative. Explain why.
8. Explain why moderate contamination of a basalt by granitic rocks does not greatly
change the FeO/MgO ratio of the hybrid magma with respect to the ratio of the original
basalt.
9. Black smokers from mid-ocean ridges spout waters resulting from the mixing of
hydrothermal solutions with seawater. Which of the following plots do you expect
to produce binary mixing arrays that are straight lines:
 
 
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