The Yadovitaya fumarole, Tolbachik volcano: A comprehensive mineralogical and geochemical study and driving factors for mineral diversity

Active volcanic fumaroles are one of the most spectacular natural objects in terms of mineral diversity. The Great Tolbachik Fissure Eruption (GTFE) (Kamchatka) fumaroles are renowned for its exceptional number of mineral species. The total number of mineral species that have been reliably identified from this particular locality exceeds 600, which is approximately 10 % of all known minerals to date. In this study, we employ a comprehensive approach (bulk chemistry, microprobe analysis, powder X-ray diffraction, HR X-ray computed tomography, and 34S, 18O, and 65Cu isotope measurements) to study the distribution of primary exhalation and secondary mineral assemblages and to reveal the driving factors responsible for the unique mineral diversity in the Yadovitaya fumarole. High oxygen fugacity, interaction of minerals with atmospheric oxygen and water from seasonal precipitation (leading to abundant hydrated mineral associations), temperature conditions controlling the spatial distribution of mineral-forming components, gas-rock interactions, and basaltic scoria morphology perfect for the crystallization of various minerals are some of the factors revealed. The Yadovitaya fumarole cross-section consists of 12 zones, each of which has characteristic mineral assemblages. The temperature ranges from 400 °C at the bottom to 30 °C at the surface. The zonal cross-section and sequential formation of exhalative fumarolic minerals are associated with the gradual distribution of a number of key mineral-forming elements, primarily S, Cu, Pb, Zn, and As. Furthermore, characteristic patterns for Rb and Cs are observed. The significance of atmospheric oxygen (δ18O = 23 ‰) and the impact of δ18O fractionation versus δ65Cu fractionation on the formation of exotic fumarolic minerals is discussed.