Secondary Ion Mass Spectrometry Bias on Isotope Ratios in Dolomite-Ankerite, Part I: δ18O Matrix Effects
- University of Wisconsin, Madison, WI (United States); UW-Madison
- University of Wisconsin, Madison, WI (United States)
- University of Wisconsin, Madison, WI (United States); Rutgers University, New Brunswick, NJ (United States)
Here, we document the development of a suite of carbonate mineral reference materials for calibrating SIMS determinations of δ18O in samples with compositions along the dolomite–ankerite solid solution series [CaMg(CO3)2–CaFe(CO3)2]. Under routine operating conditions for the analysis of carbonates for δ18O with an IMS 1280 instrument (at WiscSIMS, 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‰ (2s) for 10-μm spots and ± 0.7‰ (2s) 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‰ (2s) for 10-μm spots and ± 1‰ (2s) for 3-μm spots.
- Research Organization:
- University of Wisconsin, Madison, WI (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- FG02-93ER14389
- OSTI ID:
- 1666243
- Alternate ID(s):
- OSTI ID: 2007097
- Journal Information:
- Geostandards and Geoanalytical Research, Journal Name: Geostandards and Geoanalytical Research Journal Issue: 2 Vol. 40; ISSN 1639-4488
- Publisher:
- Wiley - International Association of GeoanalystsCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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