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Effect of sea water interaction on strontium isotope composition of deep-sea basalts

Dasch E. Julius·C. E. Hedge·J. Dymond
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Abstract

Analyses of rim-to-interior samples of fresh tholeiitic pillow basalts, deuterically altered holocrystalline basalts, and older, weathered tholeiitic basalts from the deep sea indicate that 87 Sr/ 86 Sr ratios of the older basalts are raised by low temperature interaction with strontium dissolved in sea water. 87 Sr/ 86 Sr correlates positively with H 2 O in these basalts; however, there is little detectable modification of the strontium isotope composition in rocks with H 2 O contents less than 1%. The isotope changes appear to be a function of relatively long-term, low-temperature weathering, rather than high-temperature or deuteric alteration. Strontium abundance and isotopic data for these rocks suggest that strontium content is only slightly modified by interaction with sea water, and it is a relatively insensitive indicator of marine alteration. Average Rb-Sr parameters for samples of apparently unaltered basalt are: Rb= 1.11ppm; Sr= 132ppm; 87 Sr/ 86 Sr= 0.70247.

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Dasch E. Julius, C. E. Hedge, J. Dymond. 1973. Effect of sea water interaction on strontium isotope composition of deep-sea basalts. https://doi.org/10.1016/0012-821x(73)90112-x

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