Geoscience Reference
In-Depth Information
87
Rb/
86
Sr
87
Sr/
86
Sr
Sample
B105
WR
2.244
0.738
B20C
WR
3.642
0.7612
B20
WR
3.628
0.7573
biotite
116.4
1.2146
B41
WR
6.59
0.7992
biotite
289.7
1.969
B4
WR
0.2313
0.7074
Table 4.4
Sm-Nd isotopic data for Apollo 17 basalt
75075 (Lugmair
et al.,
1975
)
147
Sm/
144
Nd
143
Sm/
144
Nd
Plagioclase
0.1942
0.51300
Ilmenite
0.2416
0.51417
Whole-rock
0.2566
0.51454
Pyroxene
0.2930
0.51542
the following samples (
Table 4.3
). Infer the emplacement age and the perturbation age
of these rocks.
5. The Sm-Nd dating of Apollo 17 basalt 75075 (Lugmair
et al.
,
1975
). Plot the results
(mineral) isochron and determine the eruption age of this basalt (
λ
147
Sm
= 0.654
×
10
−
11
a
−
1
).
the external (whole-rock) isochron and determine the emplacement age of these basalts
(
6.
10
−
11
a
−
1
). Do you think these basalts were erupted with the same
176
Hf/
177
Hf initial value? If not, why do you think the isochron looks so good?
7. Write the master equation for the
187
Re-
187
Os isochron using
188
Os as the stable
reference isotope.
8. Introducing
40
K-
40
Ca dating: the Pikes Peak granite (Wyoming). What are the respec-
tive probabilities that
40
K decays into
40
Ca and
40
Ar? What is the isochron equation
of the
40
K-
40
Ca system if one uses the stable isotope
42
Ca as the reference? Draw the
internal (mineral) isochron for the PP 76-2 sample (
Table 4.6
). What is the age of the
last homogenization of Ca in the Pikes Peak granite?
9. Minerals extracted from a basaltic andesite at the Soufrière St. Vincent in the Antilles
calculate the age of the last Th isotopic homogenization of these minerals.
λ
176
Lu
=
1.865
×
