Petrologic, Mineralogical, and Geochemical Properties of Ashes Discharged by the Summit Eruptions of Klyuchevskoi in 2020–2021 before the Lateral Eruption from the Gorshkov Vent

Our multidisciplinary petrologic, mineralogical, and geochemical studies of volcanic material sampled from three chronologically discrete, but successive, ash discharges during the period from November 30, 2020 to January 18, 2021 were concerned with grain-size inhomogeneity, chemical and mineral phase composition, the concentrations of trace elements, the isotopy of Sr, Nd, and carbon, and with the composition of inorganic and organic lithogenic gases. For the first time volcanic ashes were found to contain eskolaite, mantle spinellids of the magnetite–magnesioferrite composition, hybrid compounds of Ca–Zn-carbonates with titanium formate, and polycomponent metallo-organic compounds. The net result was to obtain proof of a mantle–asthenosphere origin of the ash material and to identify a previously unknown pattern consisting in a conjugate temporal orderliness in the variations of many properties in the material sampled from the explosions. This seems to reflect the evolution of the melt in the mantle magma chamber.