Determination of sulfur in fluid inclusions by laser ablation ICP-MS

Abstract

The quantification capabilities for sulfur microanalysis in quartz-hosted fluid inclusions were investigated with laser ablation (LA) inductively coupled plasma quadrupole mass spectrometry (ICP-Q-MS) and ICP sector field mass spectrometry (ICP-SF-MS) allowing resolution of sulfur from polyatomic interferences. A scapolite mineral sample was used to determine the sulfur concentration in NIST SRM 610 (570 ± 70 µg g⁻¹), which was further validated using EPMA and then used as standard reference material for the fluid inclusion analysis. The sulfur concentration in an assemblage of brine inclusions from a quartz–molybdenum vein was determined to be 5900 ± 2000 µg g⁻¹ measuring 17 inclusions with the ICP-SF-MS and 13 inclusions with the ICP-Q-MS instrument. The agreement between the two ICP-MS instruments for sulfur was ∼5% and well within the overall precision of 35% relative standard deviation. The precision and accuracy was not limited by interferences, but by a so far unknown sulfur contamination source when ablating the host mineral quartz. Due to this contamination, a careful baseline correction is necessary which is described and discussed in detail. Nevertheless, the method developed to determine sulfur maintains the multi-element capabilities for individual fluid inclusions. Limits of detection for sulfur are correlated with the inclusion mass and were found to be ∼ 30–100 µg g⁻¹ for 60 μm inclusions.