Analytical Methods for Sulfur Determination in Glasses, Rocks, Minerals and Fluid Inclusions

Abstract

The analytical methods described above are all in use for the detection of sulfur concentration in a range of materials (Table 4). Choice of the most appropriate method is a function of the type of material to be analyzed, sample availability, and to some extent the (Figure presented) expected sulfur concentration. A review of the literature shows that the method of choice for bulk sulfur analyses of rocks (including ores) involves an elemental analyzer coupled with an infrared detection cell (e.g., LECO, ELTRA systems). The "Kiba" method of sulfur extraction followed by gravimetric analysis allows the detection of sulfur in the range of 50-100 ppm, but care must be exercised in the collection of produced sulfide and final weighing. The method is particularly suitable for the collection of finely disseminated sulfides in rocks for isotopic analysis. For routine determination of sulfur in minerals and glasses the electron microprobe remains the most utilized technique, unless sulfur is present at concentrations less than 50 to 100 ppm. For the detection of low-levels of sulfur in minerals and glasses Secondary Ion Mass Spectrometry may become the norm. Only a few labs in the world at present are capable of exploring sulfur determination by SIMS; the future for routine sulfur analysis may be a function (Table presented) of instrument availability. Nuclear methods of sulfur analyses offer the potential for low-level sulfur determination, but standards and samples with known isotopic compositions must be run together to reduce large variations in accuracy. Laboratory availability will limit the routine use of nuclear methods of analyses for most geologic materials. Sulfur analyses using LA-ICP-MS technology is in its infancy, but the potential to determine low-levels of sulfur concurrently with other trace-elements ensures that research will continue to be directed at making sulfur analyses via LA-ICP-MS routine. Analyses of sulfur in fluid inclusions via LA-ICP-MS will advance research on ore genesis and volatile interaction with rocks. Microanalytical tools involving the ion probe and LA-ICP-MS offer an additional benefit of potential determination of sulfur isotope ratios (see the contributions in this volume by Marini et al. 2011 and Simon and Ripley 2011). Samples analyzed via mass spectrometry following high-temperature combustion offer a similar benefit, but the extraction of sulfur species dissolved in glass by this method has proven difficult with most EA systems. © Mineralogical Society of America.