16
Peter Stille and Graham Shields
6(]0
500
4OO
0
300
<
2OO
100
e~'~,.
& Rb-St apparent ages
9 K - Ar appaitent ages
.,.r 0
"N
,.,"
\ e ~ e
~
A ~
Kllll
I
I
I
[
K t3
KA4
KB5
KC8
K09
K J5
Boreholes
Fig. 2.4. Apparent Rb-Sr and K-Ar biotite ages as a function ot increasing weathering.
Fresh biotites from boreholes K2/3 and Kill. Altered biotites from bvreholes KA4-KJS.
(Cfauer e[ aI. 1982)
T a b l e 2.2. 8~SO and 8D values (SMOW) in altered biotites, ffrom Clauer et al. 1982)
sample
61SO
8D
H,O (%)
I
5.7
-65
2.77
3
7,2
-83
5.73
4
7.4
-92
5,05
5
8,5
-84
530
6
7.6
-84
5.29
7
8.4
-87
5.17
8
7.5
-92
.4.67
9
8.0
-91
4.75
10
8.5
-87
7.14
Weathered biotites fall without exception on a straight line, which can be
extended to reach the fresh biotites. This means nothing other than that Sr and Ar
have been lost to the system at comparable rates. The K-Ar age produces an
"apparent age" that is likely Io be similar to the Rb-Sr "age" (Fig. 2.4).
Peter Stille and Graham Shields
6(]0
500
4OO
0
300
<
2OO
100
e~'~,.
& Rb-St apparent ages
9 K - Ar appaitent ages
.,.r 0
"N
,.,"
\ e ~ e
~
A ~
Kllll
I
I
I
[
K t3
KA4
KB5
KC8
K09
K J5
Boreholes
Fig. 2.4. Apparent Rb-Sr and K-Ar biotite ages as a function ot increasing weathering.
Fresh biotites from boreholes K2/3 and Kill. Altered biotites from bvreholes KA4-KJS.
(Cfauer e[ aI. 1982)
T a b l e 2.2. 8~SO and 8D values (SMOW) in altered biotites, ffrom Clauer et al. 1982)
sample
61SO
8D
H,O (%)
I
5.7
-65
2.77
3
7,2
-83
5.73
4
7.4
-92
5,05
5
8,5
-84
530
6
7.6
-84
5.29
7
8.4
-87
5.17
8
7.5
-92
.4.67
9
8.0
-91
4.75
10
8.5
-87
7.14
Weathered biotites fall without exception on a straight line, which can be
extended to reach the fresh biotites. This means nothing other than that Sr and Ar
have been lost to the system at comparable rates. The K-Ar age produces an
"apparent age" that is likely Io be similar to the Rb-Sr "age" (Fig. 2.4).