The strontium isotopic composition of interstitial waters from sites 245 and 336 of the Deep Sea Drilling Project |
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| Authors: | CJ Hawkesworth H Elderfield |
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| Institution: | aDepartment of Earth Sciences, The University of Leeds, Leeds LS2 9JT Great Britain |
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| Abstract: | Measurements of 87Sr/86Sr ratios of interstitial waters from leg 25, site 245 and leg 38, site 336 of the Deep Sea Drilling Project show that the enrichment of Sr2+ with depth is caused both by the alteration of volcanic material and by the introduction of strontium derived from calcium carbonate. 87Sr/86Sr ratios range from 0.70913 to 0.70794 at site 245 and from 0.70916 to 0.70694 at site 336. The low ratios compared with contemporaneous seawater reflect the release of Sr from a volcanic source having, according to material-balance calculations, a 87Sr/86Sr ratio of about 0.7034 at site 336. At this site the source appears to be volcanic ash and not basaltic basement which acts as a sink for Sr2+ during in situ low-temperature weathering. The volcanic contribution to the strontium enrichment in the basal interstitial waters varies from <10% at site 245 to >50% at site 336. The remaining Sr2+ is derived from Sr-rich biogenic carbonate during diagenetic recrystallization to form Sr-poor calcite. |
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