Title: The Isotope Geochemistry of Strontium and Lead in Lake Superior Sediments and Water
Abstract: Concentrations of potassium, rubidium, and strontium in eight samples of gray clay sediment from Lake Superior average 3.4%, 160 ppm, and 190 ppm, respectively. These concentrations vary less than ±15% over sediment depths of 4 meters and over an areal extent in the lake of 400 km. The isotopic composition of strontium in the sediment is also constant, with a Sr87/Sr86 value of 0.739. Two samples of deep lake water showed a strontium concentration of 0.018 ppm. As the Sr87/Sr86 value of this water strontium is 0.718, the water strontium is clearly not in isotopic equilibrium with the sediment strontium. Results of the isotopic analysis of three fractions of lead from one sediment sample indicate that the lake sediments were derived dominantly from the 2.5–3.0 b.y. rocks of the Superior Province shield. The strontium results are consistent with the following average values for this Precambrian shield source rock: Sr87/Sr86 = 0.730 ± 0.01, Rb/Sr = 0.25 ± 0.10. The lead data yield limiting values of Pb206/Pb204 ≥ 20.53, Pb207/Pb204 ≥ 15.87, Pb208/Pb204 ≥ 40.34, μ(U238/Pb204) ≥ 13.7.
Publication Year: 2013
Publication Date: 2013-04-03
Language: en
Type: book-chapter
Indexed In: ['crossref']
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Cited By Count: 25
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