L.P. Vergasova1, S.K. Filatov2, T.M. Philosophova1

1Institute of Volcanology and Seismology FED RAS, Petropavlovsk-Kamchatsky, 683006, Russia
2St. Petersburg State University, St. Petersburg, 199034, Russia

We determined an isomorphic group of compounds with common formula K3Cu3(Fe3+, Al)O2(SO4)4 in products from fumarole activity of the Great Tolbatchik Fissure Eruption (GTFE, Kamchatka, 1975-1976). Within the isomorphic group, based on Fe and Al concentration we distinguished members on both sides of nominal 50 mol.% border. This fact along with variations in typical and diagnostically important physical characteristics of minerals was a factor for us to divide the group into two mineral species. Fe-members we called as "klyuchevskite", while Al-members were called as "alumoklyuchevskite". The latter is an aluminum analogue of klyuchevskite, compared to which Al is predominantly placed in Fe3+ positions.

Keywords: cone, postmagmatic activity, volcanic exhalations, fumarole minerals.