Analysis of ³⁴S-¹⁸O isotopic clumping in sulfate by high-resolution mass spectrometry of SO₂F₂

Abstract

We present a novel technique to analyze d³⁴S, d¹⁸O, D'³³S, and ³⁴S-^18OO double-substitution (D'³⁴S¹⁸O) in sulfate by measuring SO₂F₂ gas with a high-resolution isotope ratio mass spectrometer. The external reproducibility (1 sem, all numbers in per mille) is ± 0.09 (d³⁴S), ± 0.2 (d¹⁸O), ± 0.02 (D'³³S), and ± 0.08 (D'³⁴S¹⁸O) for repeated analyses of our in-house reference sulfate. Furthermore, accuracy of our analytical approach is demonstrated by the analysis of sulfate with distinct negative D'³⁴S¹⁸O, produced by mixing ³⁴S and ^18OO labeled sulfate solutions.Sulfates from laboratory experiments as well as from different natural environments show a total D'³⁴S¹⁸O range of approx. 1.5 per mille and indicate that sulfates that form in low temperature surface environments have distinctively higher D'³⁴S¹⁸O than sulfates which form at elevated temperature at hydrothermal conditions.Therefore, D'³⁴S¹⁸O may be a promising tracer for sulfate sources.