ABSTRACT

The δ¹⁷O and δ¹⁸O values of some international silicate reference materials such as NBS-28 quartz, NBS-30 biotite, UWG2 garnet, San Carlos olivine and some mineral separates of terrestrial origin were re-evaluated on the VSMOW-SLAP scale using the CO₂-laser fluorination technique. To report their δ¹⁸O values on the VSMOW-SLAP scale, the δ¹⁷O and δ¹⁸O values of O₂ directly derived from VSMOW and SLAP were measured using the same preparation line as used for the silicates. Application of the VSMOW-SLAP scale to the above silicate reference samples resulted in the δ¹⁸O values of NBS-28 quartz, NBS-30 biotite, UWG2 garnet and San Carlos olivine that are 9.18, 4.88, 5.59 and 5.28‰, respectively. The data form a straight line in the 10³ ln(1 + δ¹⁷O/10³) vs. 10³ ln(1 + δ¹⁸O/10³) plot with a slope of 0.526 ± 0.003 (standard error at 95% confidence limit), but the line for the waters (VSMOW, GISP, SLAP and MSA-6) seems to have a slightly steeper slope of 0.528 ± 0.001, although difference of the slopes is not statistically significant.