7 Sm-Nd Isotope Geochemistry of Ar~llaceous Sediments 191
Z
Z
0.5113
3"
0.5111
~,,~,t'~/"~ L1
05109
L2 / oR1
0.5t08
, ~ 2
"~ E3-Et, ~
0.5107
"~'~'~"~0,50959
~ 10
0.5106
0.5105
,
,
~
,
,
,
,
,
,
0.08
0.09
0.10
0.11
0.12
l~Sm / l~"Nd
0
WR
i
i
0.13
O.lt.
Z
"1:3
Z
0.5112
O /
0.5111
~ " %x%
~
L!
0.5110
~t,%~/~ "/
/
e/e El
0.5;09
/ L2
0.5106
050953 "- 7
0.5105
,
,
,
A
,
,
0.04
0.09
0]0
0.11
I~7Sm / ~Nd
i
i
i
012
0.13
Fig. 7.4. Sm-Nd isochron diagram for two bituminous clay-shale samples from Gabon.
WR: whole rock: El: clay fraction <0.2 }.a'n: E2: Clay fraction <0.4 }am. Ll, L2, RI, R2:
Leachate-residue pairs for El and E2 respectively. E3-ES: clay fractions >0.4 p.m. Only the
clay fractions El, E2 and the corresponding leachate-residue pairs define isochrons whose
ages are identical within the margin or" error. The initial i'*3Nd/l~Nd ratios of these
isochrons are also identical at 0.50959 +/- I0 and 0.50953 +I- 7 (MSWD = mean square of
weighted deviates). (Bros et al. 1992)