The oxygen isotope composition of San Carlos olivine on the VSMOW2‐SLAP2 scale

Abstract

RATIONALE: The precise determination of Δ'17 O values in terrestrial material is becoming increasingly important to understand the mass-dependent fractionation processes that cause variations in oxygen isotope ratios. San Carlos olivine is widely used as the reference material for oxygen isotope measurements of terrestrial and extraterrestrial materials. We report new Δ'17 O values for San Carlos olivine that were independently determined in two different laboratories (Geoscience Center [GZG], University of Göttingen) and Institute for Study of the Earth's Interior [ISEI], Okayama University, Misasa) in direct comparison with VSMOW2 and SLAP2 water standards. METHODS: The δ 17 O and δ 18 O values of VSMOW2, SLAP2, GISP, and San Carlos olivine were determined relative to reference gas. In both laboratories, water and San Carlos olivine samples were prepared by BrF 5 fluorination. In both laboratories, the O 2 released from water and olivine samples was passed through the same purification system and measured using the same mass spectrometer relative to the same reference gas. RESULTS: In both laboratories, the δ 17 O 0.528 value (calculated from the VSMOW2-SLAP2 scaled δ values) of San Carlos olivine from GZG was À36 ± 9 ppm and, from ISEI, a value of À40 ± 7 ppm (1σ standard deviation) was determined. These values are~50 ppm higher than previously reported from the same laboratories. Possible causes for the observed discrepancies are discussed. CONCLUSIONS:The results of this study in comparison with previous data from the same laboratories demonstrated that for high accuracy determination of Δ'17 O values: (i) calibration of the reference gas relative to O 2 released from primary standards (VSMOW2, SLAP2) in the same laboratory is highly recommended, (ii) non-linearity of the mass spectrometer may not only affect δ 17O values, and (iii) the VSMOW2-SLAP2 scaling should also be applied to analyses of rocks and minerals. Studies that are concerned with small differences in Δ'

Tracing the oxygen isotope composition of the upper Earth’s atmosphere using cosmic spherules

“…The corrected measured datum of Δ' 17 O=−0.467±0.005‰ for air oxygen14 is then identical to our measured datum of −0.469±0.007‰ (Supplementary Table 1) and agrees with the model datum of −0.469‰ presented by Young et al 14. The non-application of VSMOW2-SLAP2 scaling34 to our air data shifts the Δ' 17 O down to ∼−0.50‰, which would be closer to the values of Barkan and Luz18 and Kaiser and Abe20. For this study, we adopt δ 18 O=24.15‰ and Δ' 17 O=−0.47‰ for the troposphere.…”

“…As magnetite is the dominant phase in I-type spherules2446, we used terrestrial magnetite along with NBS-28 quartz for tests. For NBS-28, we adopted a δ 18 O=9.65‰ and Δ' 17 O=−0.054‰ (Δ' 17 O from47, with revision from34). …”

“…In brief, sample O 2 was liberated by laser fluorination (F 2 ) and analysed in continuous flow mode in a Thermo MAT253 gas source mass spectrometer. NBS-28 quartz was used for normalisation relative to VSMOW2 scale (δ 17 O=5.04‰, δ 18 O=9.65‰, Δ' 17 O=−0.054‰; using the revised calibration of San Carlos olivine from34). The total masses of the spheres were 160–370 μg and thus suitable for measurement of multiple aliquots of a single spherule.…”

“…Oxygen from air was extracted using the same line that was described by Pack et al 34. for their water (including VSMOW2 and SLAP2) and silicate analyses (San Carlos olivine) (Fig.…”

Interpreting and propagating the uncertainty of the standard atomic weights (IUPAC Technical Report)

“…However, and in general, igneous and metamorphic rocks need not lie on the same oxygen fractionation lines as meteoric waters or seawater [43,44].…”