ИСТИНА

In 2020, the Tolbachik volcano at the Kamchatka Peninsula, Russia became the world record-holder in a number of new minerals first discovered for one geological object, when passed the former leader, Khibiny alkaline complex, Kola Peninsula, Russia. Today the three leaders in this field are as follows: Tolbachik – 133 IMA-approved new mineral species, Khibiny – 127, and Lovozero alkaline complex (Kola Peninsula) – 114. Tolbachik also demonstrates the world-highest dynamics in discoveries of new minerals for one locality: since 2011, i.e. during the last decade 103 minerals were first described there, including 77 species characterized by our research team. All 133 new minerals were found in deposits of active oxidizing-type fumaroles born by Great Tolbachik Fissure Eruption 1975– 1976 (mainly) and the Tolbachik eruption of 2012–2013. Only 14 of them are H2O-bearing species that formed under temperatures below 100–150oC involving atmospheric agents while others are products of high-temperature fumarolic activity (200–800oC). A very bright geochemical feature of Tolbachik fumaroles is the distinct "ore" specialization reflected, in particular, in the chemistry of new minerals: the majority of them are oxygen compounds or chlorides with species-defining chalcophile elements: Cu, Pb, Zn, As, Se, Te, Tl, Cd, Bi, Sn. Strongly oxidizing conditions of mineral crystallization are illustrated by high oxidation states of indicator elements: minerals with only S 6+, Fe3+, As5+, Mo6+, W6+ are known there; some new minerals contain V5+, V4+, Se4+, Te4+ or Tl3+. The distribution of Tolbachik new minerals between chemical classes is as follows: arsenates – 42, sulfates – 41, chlorides – 13, vanadates – 12, selenites – 10, borates – 5, molybdates – 2, silicates – 2, oxides – 2, phosphates – 2, fluoride – 1, and carbonate – 1. All these arsenates, vanadates, selenites, borates, molybdates, silicates, oxides, and phosphates are H- free and known only in high-temperature (> 200–300oC) parageneses. In whole, in deposits of Tolbachik fumaroles about 330 minerals are reliably known now (including products of the supergene alteration of sublimates), i.e. 133 new species consist 40% of their mineral diversity. So high share of new minerals clearly demonstrates the uniqueness of Tolbachik fumarole fields. They can be considered as the world-brightest example of an on-land oxidizing-type fumarolic mineral-forming system, an etalon object for the studies of this genetic type in both mineralogical and geochemical aspects. Such originality is caused by unique for natural systems physical and chemical conditions and mechanisms of mineral formation, namely a combination of high temperatures, atmospheric pressure, very high oxygen fugacity (due to mixing of hot volcanic gas with air), gas transport of the majority of chemical elements and direct deposition of minerals from volcanic gases which have here specific geochemical features including strong enrichment by alkali metals and chalcophile ("ore") elements. The study was supported by the Russian Science Foundation, grant 19-17-00050.