In situ analyses of hydrogen and sulfur isotope ratios in basaltic glass using SIMS

We developed in situ analyses of hydrogen and sulfur isotope ratios of basaltic glass using high-resolution, multicollection secondary ion mass spectrometry (CAMECA IMS-1280HR). Hydrogen and sulfur isotopes of standard basaltic glasses were determined by a high-temperature conversion elemental analyzer/isotope ratio mass spectrometer (IRMS) and IRMS, respectively. For the in situ analysis of sulfur isotopes, a defocused Cs beam (similar to 0.5 nA; similar to 10 mu m diameter) was used, but for hydrogen isotopes, we used a larger defocused beam (similar to 5 nA; similar to 15 mu m diameter) to decrease the hydrogen background. For analyses of D/H (S-34/S-32) ratios, (OH)-O-16 (S-32) and (OD)-O-16 (S-34) were measured in multi-detection mode with a Faraday cup and an axial electron multiplier, respectively. Each measurement time was 6-7 minutes. Precisions (2 standard errors) for D/H and S-34/S-32 ratios were similar to 6 parts per thousand (H2O > 1 wt%) and similar to 0.6 parts per thousand (S > 1000 ppm), respectively. Our developed method for rapid and high spatial resolution analysis can determine multiple elements and isotopes of volatiles in a single small melt inclusion of similar to 30 mu m diameter. Using this method, we analyzed hydrogen and sulfur isotope ratios of submarine basaltic glasses from mid-oceanic ridges and oceanic islands of Hawaii and confirmed that their D/H and S isotope ratios were consistent with reported values.