Open AccessAccuracy and precision of 88 Sr/ 86 Sr and 87 Sr/ 86 Sr measurements by MC‐ICPMS compromised by high barium concentrations
Author(s) -
Scher Howie D.,
Griffith Elizabeth M.,
Buckley Wayne P.
Publication year - 2014
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2013gc005134
Subject(s) - isotopes of strontium , barium , strontium , analytical chemistry (journal) , isotope , fractionation , radiogenic nuclide , seawater , isotope fractionation , mineralogy , geology , chemistry , radiochemistry , mantle (geology) , environmental chemistry , chromatography , geochemistry , inorganic chemistry , physics , oceanography , quantum mechanics , organic chemistry
Barite (BaSO 4 ) is a widely distributed mineral that incorporates strontium (Sr) during formation. Mass‐dependent fractionation of Sr isotopes occurs during abiotic precipitation of barite and formation of barite associated with biological processes (e.g., bacterial sulfide oxidation). Sr isotopes in barite can provide provenance information as well as potentially reconstruct sample formation conditions (e.g., saturation state, temperature, biotic versus abiotic). Incomplete separation of Ba from Sr has complicated measurements of Sr isotopes by MC‐ICPMS. In this study, we tested the effects of Ba in Sr sample solutions and modified extraction chromatography of Sr using Eichrom Sr Spec (Eichrom Technologies LLC, USA) resin to enable rapid, accurate, and precise measurements of 88 Sr/ 86 Sr and 87 Sr/ 86 Sr ratios from Ba‐rich matrices. Sr isotope ratios of sample solutions doped with Ba were statistically indistinguishable from Ba‐free sample solutions below 1 ppm Ba. Deviations in both 87 Sr/ 86 Sr and δ 88/86 Sr occurred above 1 ppm Ba. An updated extraction chromatography method tested with barite and Ba‐doped seawater produces Sr sample solutions containing 10–100 ppb levels of Ba. The practice of Zr spiking for external mass‐discrimination correction of 88 Sr/ 86 Sr ratios was also evaluated, and it was confirmed that variable Zr levels do not have adverse effects on the accuracy and precision of 87 Sr/ 86 Sr ratios in the Zr concentration range required to produce accurate δ 88/86 Sr values.