Abstract
The isotopic composition of strontium of pore water and of authigenic minerals leached from the sediment of core 119K with hot aqua regia is similar to that of the brine in the Discovery deep and differs from that of normal seawater. The average 87 Sr 86 Sr ratio of strontium removed by acid leaching is 0.7077 ± 0.0007 (1σ) compared to a value of 0.70904 for the Red Sea. The detrital silicate fraction exhibits an approximate inverse correlation between 87 Sr 86 Sr ratios and strontium concentrations which provides tentative support for a model in which the detrital silicate fraction of deep-sea sediment is considered to be a mixture of terrigenous dust of sialic composition enriched in radiogenic 87Sr and of volcanogenic material of basaltic composition and low 87Sr abundance. The 87 Sr 86 Sr ratios of the shells of foraminifers and pteropods, expressed as δ 87Sr‰ relative to 0.70904 for seawater, decrease from −0.23 ± 0.17‰ at 90 cm to −0.82 ± 0.17‰ at 273 cm and remain constant at this value to a depth of 450 cm. The lowering of the δ 87Sr values is attributed both to the presence of aragonite overgrowths on pteropod shells and to possible isotope exchange with strontium in the connate fluid.
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