Bromine isotope ratio measurements in seawater by multi-collector inductively coupled plasma-mass spectrometry with a conventional sample introduction system

A simple and accurate methodology for Br isotope ratio measurements in seawater by multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) with pneumatic nebulization for sample introduction was developed. The Br+ signals could be measured interference-free at high mass resolution. Memory effects for Br were counteracted using 5 mmol L-1 of NH4OH in sample, standard, and wash solutions. The major cation load of seawater was removed via cation exchange chromatography using Dowex 50WX8 resin. Subsequent Br preconcentration was accomplished via evaporation of the sample solution at 90 °C, which did not induce Br losses or isotope fractionation. Mass discrimination was corrected for by external correction using a Cl-matched standard measured in a sample-standard bracketing approach, although Sr, Ge, and Se were also tested as potential internal standards for internal correction for mass discrimination. The δ81Br (versus standard mean ocean bromide (SMOB)) values thus obtained for the NaBr isotopic reference material NIST SRM 977 and for IRMM BCR-403 seawater certified reference material are in agreement with literature values. For NIST SRM 977, the 81Br/79Br ratio (0.97291) was determined with a precision ≤0.08‰ relative standard deviation (RSD).A simple and accurate methodology for Br isotope ratio measurements in seawater by multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) with pneumatic nebulization for sample introduction was developed. The Br+ signals could be measured interference-free at high mass resolution. Memory effects for Br were counteracted using 5 mmol L-1 of NH4OH in sample, standard, and wash solutions. The major cation load of seawater was removed via cation exchange chromatography using Dowex 50WX8 resin. Subsequent Br preconcentration was accomplished via evaporation of the sample solution at 90 A degrees C, which did not induce Br losses or isotope fractionation. Mass discrimination was corrected for by external correction using a Cl-matched standard measured in a sample-standard bracketing approach, although Sr, Ge, and Se were also tested as potential internal standards for internal correction for mass discrimination. The delta Br-81 (versus standard mean ocean bromide (SMOB)) values thus obtained for the NaBr isotopic reference material NIST SRM 977 and for IRMM BCR-403 seawater certified reference material are in agreement with literature values. For NIST SRM 977, the Br-81/Br-79 ratio (0.97291) was determined with a precision a parts per thousand currency sign0.08aEuro degrees relative standard deviation (RSD)

Cl/Br ratios and stable chlorine isotope analysis\ud of magmatic–hydrothermal fluid inclusions from Butte,\ud Montana and Bingham Canyon, Utah

A bulk geochemical study has been carried out\ud on fluid inclusion leachates extracted from quartz veins\ud from porphyry Cu deposits in Butte, Montana, USA and\ud Bingham Canyon, Utah, USA. The leachates mostly represent\ud low-salinity magmatic–hydrothermal fluid inclusions.\ud Their halogen ratios (Br/Cl) of fluid inclusion leachates were\ud determined by ion chromatography, and δ37Cl values of the\ud leachates were measured by continuous-flow isotope ratio\ud mass spectrometry. Br/Cl ratios from early pre-Main stage\ud and later Main stage veins at Butte range from 0.60 to\ud 1.88×10−3M. Ratios are similar in pre-Main stage veins with\ud sericite bearing selvages and Main stage samples ranging\ud from 0.81 to 1.08×10−3 and from 0.92 to 1.88×10−3M,\ud respectively, clustering below seawater (1.54×10−3M) and\ud overlapping mantle values (~1–2×10−3M). Two samples\ud associated with early pre-Main stage potassic alteration yield\ud distinctly lower Br/Cl ratios of 0.60 and 0.64 × 10−3M. Butte\ud δ37Cl values range from −0.8‰ to −2.3‰ with no\ud significant difference between pre-Main stage and Main\ud stage samples. Br/Cl ratios for quartz veins from Bingham\ud Canyon range from 0.18 to 3.68×10−3M. Br/Cl ratios from\ud Bingham range above and below previously reported for\ud porphyry copper deposits. In contrast to Butte, δ37Cl values\ud for Bingham are lower, ranging from −0.9‰ to −4.1‰. In\ud the absence of any processes which can significantly\ud fractionate chlorine isotopes at high temperatures, we\ud suggest that the porphyry system at Bingham, and to a\ud lesser extent at Butte, have inherited negative chlorine\ud isotopic signatures from the subducting slab generated at\ud low temperatures