RATIONALE
Oxygen triple isotope compositions give key information for understanding physical processes during isotopic fractionation between the geo‐, hydro‐, bio‐, and atmosphere. For detailed discussion of these topics, it is necessary to determine precise 17O‐excess values of terrestrial silicate/oxide minerals with respect to Vienna Standard Mean Ocean Water (VSMOW).
METHODS
Water was fluorinated in an electrically heated Ni‐metal tube into which water and BrF5 were loaded for the quantitative extraction of oxygen. Silicate/oxide minerals were fluorinated by heating with a CO2 laser in an atmosphere of BrF5. The extracted oxygen was purified and isotope ratios of the oxygen triple isotope compositions were determined using a Finnigan MAT253 isotope ratio mass spectrometer.
RESULTS
The oxygen triple isotope compositions of meteoric water and terrestrial silicate/oxide minerals fall on statistically distinguishable fractionation lines, defined as [ln(δ17O + 1) = λln(δ18O + 1) + Δ], where λ and Δ correspond to the slope and intercept, respectively. The fractionation line for meteoric water has λ = 0.5285 ± 0.0005 and Δ = 0.03 ± 0.02‰ and for terrestrial silicate/oxide minerals has λ = 0.5270 ± 0.0005 and Δ = –0.070 ± 0.005‰, at the 95% confidence limit.
CONCLUSIONS
All the analyzed terrestrial silicate/oxide minerals including internationally accepted reference materials (NBS‐28, UWG‐2, and San Carlos olivine) have a negative 17O‐excess with respect to VSMOW. We propose that it is necessary to specify if the determined δ17O values of terrestrial and extraterrestrial samples are expressed as the difference from VSMOW or the terrestrial silicate mineral‐corrected value.
@article{20131009140130-121830,
author = "Ryoji Tanaka and Eizo Nakamura",
title = "Determination of 17O-excess of terrestrial silicate/oxide minerals with respect to Vienna Standard Mean Ocean Water (VSMOW)",
journal = "Rapid Communications in Mass Spectrometry",
year = "2013",
volume = "27",
pages = "285-297",
doi = "10.1002/rcm.6453",
}
caption | ID | rowname | stone | ||
---|---|---|---|---|---|
Table 4. Oxygen isotopic compositions of silicate and oxidite minerals analyzed in this study pub | 20191220152011-412905 | oxygen (Tanaka,2013) | 14 | ||
Table 1. Major element compositions (wt.%) of silicate and oxide minerals prepared in this study pub | 20191220140310-677294 | major_min (Tanaka et al., 2013) | 12 | ||