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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 4. (April)

First Page: 533

Last Page: 533

Title: Variations in Mg/Ca as a Control on Distribution of Strontium Concentrations and ^dgr18O in Upper Tertiary Dolomites from Bahamas: ABSTRACT

Author(s): Peter K. Swart, Jean Michel Dawans


Strontium concentrations and ^dgr18O are commonly used to infer the gross composition of dolomitizing waters, yet the bases for such inferences are not firmly established. A new approach to calibrating these 2 parameters is suggested from analyses of a section of upper Tertiary dolomites from the Bahamas.

In an interval of dolomite, 120 m (394 ft) thick from a core taken on San Salvador Island, mole % MgCO3 is correlated positively with ^dgr18O, and negatively with strontium. Strontium substitutes mainly for calcium, thus the negative correlation with the mole % MgCO3. Dolomites are enriched between 3 to 7% in ^dgr18O as compared with coprecipitated calcite, and thus the positive correlation. These two covariations indicate the need to consider the stoichiometric coefficient of dolomites, and to normalize strontium concentrations and ^dgr18O with their respective stoichiometric coefficients before inferring their relationship with fluid composition.

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