Fluid inclusions in “superquartzites” of the Bural-Sardyk deposit (East Sayan)

We present results of study of fluid inclusions in “superquartzites” of the Bural-Sardyk deposit (East Sayan). “Superquartzites” are regarded as a source of extrapure quartz raw material; therefore, the presence of fluid inclusions in them is an important characteristics of their quality. We have first applied not only microthermometry but also LA-ICP-MS to study fluid inclusions in the above rocks. Release of volatiles in quartzite grit was studied by thermal-desorption mass spectrometry. The research has shown the uneven distribution of fluid inclusions in the quartz grains. The inclusions are flattened isometric or rounded (often, of complex morphology), up to 12 qm across. The concentration of salts in the fluid corresponds to 5.5-5.7 wt.% NaCl equiv., Na is the main element in its salt system, and K and Mg are present in background concentrations. According to mass-spectrometric analysis, water is the main volatile component in the “superquartzite” (39 to 124 ppm). Next in abundance are carbon-containing substances (CO, CO2, and hydrocarbons). On stepwise heating of the samples, H2O releases in two temperature regions: at low temperatures (with the maximum release at 400 °C) and at high temperatures (above 1000 °C). The results of the chemical enrichment of “superquartzites” indicate low initial contents of structural impurities, which expands the boundaries for the application of this type of raw material in the production of high-tech quartz products.