."-A. Peter Stille and Graham Shields
The first comprehensive, combined Rb-Sr and Sm-Nd isotope study of the
dissolved and suspended loads of various rivers was carried out by Goldstein and
Jacobsen (1987). They investigated major rivers in Canada, USA, Australia, Japan
and the Philipines. In this study, both the Sr and the Nd isotopic compositions
could be compared between the suspended load and the filtered water.
3.1 Sr Isotopes in River Water
The concentration of dissolved Sr in the various river waters studied ranged
between I and 3000 ~ ~__/1. Sr concentrations are correlated with the major elements
Na, Ca and Mg (Fig. 3.2).
The global, average (Na+Ca) concentration for river water is 18.6 rag/1. From
this it is possible to work out an average river water concentration for strontium of
60 I.tgrl. The Sr/(Na+Ca) ratios reflect the source regions of these elements and
therefore the drainage basins of the various rivers. The ratios lie understandably
between those for silicate rich rocks of the upper continental crust and those for
carbonate rich rocks and evaporites (Ix 10-3; Fig. 3.2).
500
400
~
300
~L
(~S 200
lO0
/
/,. o o
/
O0 :
0
the upver/o
/
^ / ' ~ " -
c,-,.,st /
/
o
y o
o
h'.X
o
SO
100
~0
200
250
Na-,. C a ( m q / l )
Fig. 3.2. St, Na and Ca concentrations of filtered river waters. Data from Goldstein and
Jacobsen 1987 (filled circles) and Tncca 1997 (open circles: rivers from the upper Rhine
valley I