Abstract
Abstract. This is the initial paper in a pair of articles devoted to silicate minerals from fumaroles of the Tolbachik volcano (Kamchatka, Russia). These papers contain the first systematic data on silicate mineralization of fumarolic genesis. In this article nesosilicates (forsterite, andradite and titanite), cyclosilicate (a Cu,Zn-rich analogue of roedderite), inosilicates (enstatite, clinoenstatite, diopside, aegirine, aegirine-augite, esseneite, “Cu,Mg-pyroxene”, wollastonite, potassic-fluoro-magnesio-arfvedsonite, potassic-fluoro-richterite and litidionite) and phyllosilicates (fluorophlogopite, yanzhuminite, “fluoreastonite” and the Sn analogue of dalyite) are characterized with a focus on chemistry, crystal-chemical features and occurrence. Unusual As5+-rich varieties of forsterite, andradite, titanite, pyroxenes, amphiboles and mica are described. General data on silicate-bearing active fumaroles and the diversity and distribution of silicates in fumarole deposits are reported. Evidence for the fumarolic origin of silicate mineralization is discussed.
Highlights
Active volcanic fumaroles can be considered natural laboratories which make it possible to study in situ the processes of mineral formation, geochemical behaviour and migration of many chemical elements
Data on the mineralogy of fumaroles were given for Central American volcanoes by Stoiber and Rose (1974), for Kamchatka volcanoes by Serafimova (1979) and for European volcanoes by BalicŽunicet al. (2016)
In the present paper and the companion article we describe these silicates and report the first systematic characteristics of silicate mineralization formed in fumaroles at the active volcano
Summary
Active volcanic fumaroles can be considered natural laboratories which make it possible to study in situ the processes of mineral formation, geochemical behaviour and migration of many chemical elements. The main minerals in the majority of fumaroles related to active volcanoes are sulfates, halides, oxides and sulfides Such mineralization was reported in many papers, including review publications. Augustine (Alaska, USA) (Getahun et al, 1996), tremolite and aegirine (“acmite”) in fumaroles at Merapi (Indonesia) (Symonds et al, 1987), aegirine and andradite in fumaroles at Kudryavyi (Tessalina et al, 2008), orthoclase and albite in fumaroles borne by the Northern Breakthrough of the Great Tolbachik Fissure Eruption 1975–1976 (NB GTFE) at Tolbachik (Vergasova and Filatov, 2016), and esseneite and melilite in exhalations within a lava tube from the 2012–2013 eruption of Tolbachik (Sharygin et al, 2018) These articles, except for the last cited paper, do not contain data on chemical composition, morphological features and occurrence of silicates in fumarole systems. The discussion and conclusions concerning fumarolic silicate mineralization in general are given in the companion paper (Shchipalkina et al, 2020)
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