2 Weathering
t5
displaying very similar mobility behavior. This can be seen in Fig. 2.3 in which
both 87Sr and ~ A r contents are found to correlate with each other.
250
2oo
150
o~ 100
~_. 5o
!
O0
1.75
,...~ ~~
~
o'2
!
i
0,25
050
0.75
L00
1.25
1.50
Total 'TSr (pg/g)
Fig. 2.3.Comparison of radiogenic STSr and ~~ in biotites with increasing weathering. I
and 2: fresh biotites: 3-11: altered biotites.(Clauer et al. 1982)
Table 2.1. Rb-Sr isotope data of biotites from a weathering protqle. (from Clauer 1981 )
sample
Rb
Sr
87Rb/86Sr
87Sr/86Sr
biotite I
579
16.6
I 01.3
1.5890
biotite 1'
655
22.0
86.33
1.3730
biotite 2
544
38.8
40.66
0,8477
biotite 3
593
33.3
51.67
0,8236
biotite 4
5t5
60.6
2-I..61
0.76.,1,8
biotite ,,,t'
526
59.0
25.83
0.7764
biotite 4"
543
60.5
26,03
0.7792
biotite 5
572
72,2
22.96
0.7836
biotite 5'
553
55.7
28.76
0.7967
biotite 6
"479
92.2
15.06
0.7667
biotite 6'
386
68.0
16.,1.3
0.7649