Instrumental mass fractionation during sulfur isotope analysis by secondary ion mass spectrometry in natural and synthetic glasses

摘要: Abstract Sulfur isotope ratios are among the most commonly studied systems in geochemistry. While sulfur ratio analyses of materials such as bulk rock samples, gases, and sulfide grains routinely carried out, in-situ silicate glasses those formed magmatic relatively scarce literature. Despite a number attempts recent years to analyse volcanic experimental by secondary ion mass spectrometry (SIMS), effects instrumental fractionation (IMF) during analysis remain poorly understood. In this study we use more than 600 nine different characterise matrix that arise SIMS. Samples were characterised for major element composition, content, independent methods. Our contain between 500 3400 ppm cover wide compositional range, including low-silica basanite, rhyolite, phonolite, allowing us investigate composition-dependent IMF. We SIMS multi-collection mode with Faraday cup/electron multiplier detector configuration achieve uncertainty 0.3‰ 2‰ (2σ) on measured δ34S. At high analytical error our is similar methods, gas-source spectrometry. find IMF causes an offset −12‰ +1‰ Instrumental correlates non-linearly glass contents multivariate regression model combining Al, Na, K contents. Both ln(S) Al-Na-K models capable predicting good accuracy: 84% (ln(S)) 87% (Al-Na-K) can be reproduced within 2σ combined after correction applied. The process driving challenging identify. non-linear correlation S content dataset resembles previously documented H2O abundance D/H SIMS, could attributed changes 32S− 34S− yields changing composition. However, clear cannot identified dataset. speculate accumulation alkalis at crater floor may principal force Nonetheless, other currently unknown factors also influence observed results demonstrate multiple, well-characterised standards range required calibrate instruments prior glasses. Matrix related particular importance felsic systems, where alkali aluminium vary considerably mafic magmas.