Semi-automatic determination of the carbon and oxygen stable isotope compositions of calcite and dolomite in natural mixtures - Université Pierre et Marie Curie Accéder directement au contenu
Article Dans Une Revue Applied Geochemistry Année : 2012

Semi-automatic determination of the carbon and oxygen stable isotope compositions of calcite and dolomite in natural mixtures

Résumé

A semi-automatic, on-line method was developed to determine the delta(13)C and delta(18)O values of coexisting calcite and dolomite. An isotopic mass balance is used to calculate the compositions of dolomite after having measured that of calcite and of the "bulk'' sample. The limit of validity of this method is established by performing isotopic measurements of artificial mixtures made of precisely weighted and isotopically-characterised dolomite and calcite. The accuracy and repeatability of the calculation of dolomite delta(13)C and delta(18)O are statistically determined with a Monte-Carlo procedure of error propagation. Stable isotope ratios are determined by using an automated MultiPrep T system on-line with an isotope-ratio massspectrometer (IRMS). The reaction time and the temperature of reaction were optimised by comparing the results with the isotopic composition of known mixtures. The best results were obtained by phosphoric acid digestion after 20 min at 40 degrees C for calcite and 45 min at 90 degrees C for dolomite. This procedure allows an accurate determination of the isotopic ratios from small samples (300 mu g). Application of this protocol to natural mixtures of calcite and dolomite requires the accurate determination of the relative abundance of calcite and dolomite by combining Melieres manocalcimetry (MMC) and X-ray diffractometry (XRD).

Dates et versions

hal-00674961 , version 1 (28-02-2012)

Identifiants

Citer

M. Baudrand, G. Aloisi, Christophe Lécuyer, Francois Martineau, François Fourel, et al.. Semi-automatic determination of the carbon and oxygen stable isotope compositions of calcite and dolomite in natural mixtures. Applied Geochemistry, 2012, 27 (1), pp.257-265. ⟨10.1016/j.apgeochem.2011.11.003⟩. ⟨hal-00674961⟩
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