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Secondary Ion Mass Spectrometry Bias on Isotope Ratios in Dolomite–Ankerite, Part I: δ 18 O Matrix Effects
Author(s) -
Śliwiński Maciej G.,
Kitajima Kouki,
Kozdon Reinhard,
Spicuzza Michael J.,
Fournelle John H.,
Denny Adam,
Valley John W.
Publication year - 2016
Publication title -
geostandards and geoanalytical research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.037
H-Index - 73
eISSN - 1751-908X
pISSN - 1639-4488
DOI - 10.1111/j.1751-908x.2015.00364.x
Subject(s) - ankerite , dolomite , analytical chemistry (journal) , repeatability , chemistry , isotope , carbonate , matrix (chemical analysis) , mineralogy , ion , calcite , physics , chromatography , siderite , organic chemistry , quantum mechanics
We document the development of a suite of carbonate mineral reference materials for calibrating SIMS determinations of δ 18 O in samples with compositions along the dolomite–ankerite solid solution series [CaMg( CO 3 ) 2 –CaFe( CO 3 ) 2 ]. Under routine operating conditions for the analysis of carbonates for δ 18 O with a CAMECA IMS 1280 instrument (at Wisc SIMS , University of Wisconsin‐Madison), the magnitude of instrumental bias along the dolomite–ankerite series decreased exponentially by ~ 10‰ with increasing Fe content in the dolomite structure, but appeared insensitive to minor Mn substitution [< 2.6 mol% Mn/(Ca+Mg+Fe+Mn)]. The compositional dependence of bias (i.e., the sample matrix effect) was calibrated using the Hill equation, which relates bias to the Fe# of dolomite–ankerite [i.e., molar Fe/(Mg+Fe)] for thirteen reference materials (Fe# = 0.004–0.789); for calibrations employing either 10 or 3 μm diameter spot size measurements, this yielded residual values ≤ 0.3–0.4‰ relative to CRM NBS 19 for most reference materials in the suite. Analytical precision was ± 0.3‰ (2 s , standard deviations) for 10‐μm spots and ± 0.7‰ (2 s ) for 3‐μm spots, based on the spot‐to‐spot repeatability of a drift monitor material that ‘bracketed’ each set of ten sample‐spot analyses. Analytical uncertainty for individual sample analyses was approximated by a combination of precision and calibration residual values (propagated in quadrature), suggesting an uncertainty of ± 0.5‰ (2 s ) for 10‐μm spots and ± 1‰ (2 s ) for 3‐μm spots.