Research subject. Serpentinites of the apocarbonate type in the contact aureole of the Salmi Batholith. Aim. Mineralogical and genetic description of the calcite-serpentine rocks of the Hopunvaara ore field. Materials and methods. Thirty samples of ophicalcite were studied using scanning electron microscopy, electron probe analysis, powder X-ray diffraction, FTIR and Raman spectroscopy, as well as differential thermal analysis. Results. The ophicalcite of the Hopunvaara ore field is represented by two types. The first variety was studied on samples from the Izvestkovyi quarry (“Lime Break”). It consists of thin-fibrous aggregates of clinochrysotile and lizardite (or only lizardite) intergrowing with calcite, with subordinate amounts of phlogopite and fluorapatite, as well as with veins of magnetite. Serpentine contains a small amount of impurities – up to 1.0 wt % FeO, up to 0.7 wt % Al2O3 and not more than 0.1 wt % MnO. Calcite is chemically pure. Ophicalcite of the second type, described in the Klara mining, is composed mainly of lizardite, which forms complete pseudomorphs after crystals of forsterite and/or minerals of the humite group enclosed among a carbonate matrix. Serpentine contains 0.4–2.5 wt % FeO, 0.0–1.6 wt % Al2O3, 0.1–0.2 wt % MnO, and 0.9–2.1 wt % F. In the carbonate matrix, along with almost pure calcite, there is dolomite containing 1.4 wt % MnO. Minor minerals are represented by fluorite, phlogopite and sphalerite. Such a rock is sectioned by antigorite-carbonate-fluorite-hematite veins with cassiterite, the formation temperature of which is estimated at 300–350°C. Conclusions. The formation of ophicalcite of the first type occurred through the interaction of dolomite with acidic SiO2-rich 200–300°C hydrothermal solutions. The microfiber structure of apodolomite serpentine aggregates is due to the mechanism of their crystallization in a porous medium that occurs during carbonate leaching. Ophicalcite of the second type was formed as a result of serpentinization of forsterite calciphyres at the regressive stage of skarnification process at T < 370°C.

This paper is devoted to the olivine pseudomorphization processes occurring in basalt under the action of high-temperature O2-rich gas in oxidizing-type fumaroles at the Tolbachik volcano (Kamchatka, Russia). The alteration of olivine with composition Fo72–90 in a terraneous oxidizing-type exhalation system involves two independent processes: (1) oxidative breakdown (above 600 °C) with the formation of forsterite Fo90–100 together with hematite, magnesioferrite, and, presumably, “magnesian laihunite”; (2) replacement by mineral aggregates in which pyroxenes [enstatite, clinoenstatite, diopside, aegirine-augite (Ca0.5Na0.5)(Mg0.5Fe0.5)Si2O6], low-alumina fluoromagnesian micas (yangzhumingite and fluorotetraferriphlogopite), chondrodite or cristobalite are the main components accompanied by hematite, sometimes with magnesioferrite or tenorite. In the active Arsenatnaya fumarole, the change of the main Si minerals in pseudomorphs with the gas temperature decrease occurs in a sequence that generally reflects an increase in the degree of condensation of tetrahedral Si-O motifs: olivine (forsterite) → orthopyroxene (enstatite) → clinopyroxenes → micas → cristobalite.

Five specific types of silicate apobasaltic gas metasomatites formed in the temperature range from 850–900 to 450–500 °C have been identified and characterized in oxidizing-type fumaroles at the Tolbachik volcano (Kamchatka, Russia): (1) diopside-esseneite, (2) haüyne-diopside, (3) anorthoclase/Na-sanidine, (4) sanidine, and (5) fluorophlogopite/sanidine-fluorophlogopite metasomatites. Exhalation incrustations of certain mineral and chemical composition are related to each of these types. In the vertical section of the fumarole system from bottom to top, against the background of volcanic gas cooling, a sequential spatial change of the first four types of gas metasomatites occurs. Fluorophlogopite and sanidine-fluorophlogopite gas metasomatites have not a clear position in the vertical section of the fumarole system and presumably are formed under the action of a gas significantly enriched with Cl and F. Highly siliceous metasomatites, consisting mainly of silica phases, form instead of silicate rocks at temperatures below 450–500 °C.

Background. A rare morphological variety of magnesian serpentine, described in 1939 in the veins of the Lesnaya Varaka alkaline ultrabasic massif (Kola Peninsula) under the name “kolskite” is studied. For a long time, this variety has been considered an antigorite. Aim. Identification of the polymorphic modification of “worm-like” serpentine; determination of its crystal chemical features and possible genesis. Materials and methods . Samples were studied using electron probe analysis and scanning electron microscopy by a Jeol JSM-IT500 scanning electron microscope equipped with an INCA X-Max energy dispersion spectrometer; powder X-ray diffraction; infrared spectroscopy using a FSM-1201 IR Fourier spectrometer; and Raman spectroscopy using a EnSpectr R532 spectrometer. Results. Serpentine “kolskite” is represented by lizardite with the empirical formula (Mg 2.79 Al 0.04 Fe 3+ 0.01 ) ∑2.84 [Si 2.06 O 5 ](OH) 4 . The calculated parameters of the trigonal unit cell are as follows: a = 5.32(1) Å, c = 7.88(2) Å, V = 193.0(1) Å 3 . An increase in parameter c compared to that of apoolivine lizardite typical of ultrabasic objects indicates an expansion of the interlayer distance and is associated with serpentine hydration. Conclusion . The formation of “worm-like” lizardite aggregates could occur either by replacing vermiculite under the action of low-temperature alkaline hydrothermal solutions, or as a result of hypergenic alteration in the earlier apoolivine serpentine.

In this paper, we provide characteristics of sulfates of exhalation origin—langbeinite K2Mg2(SO4)3, two modifications of calciolangbeinite K2Ca2(SO4)3 (new data), and vanthoffite Na6Mg(SO4)4 (first mineralogical data for this genetic type)—from active fumaroles of the Tolbachik volcano in Kamchatka. These minerals are associated with anhydrous copper sulfates and arsenates, minerals of the aphthitalite and alluaudite groups, krasheninnikovite, anhydrite, sanidine, cristobalite, tridymite, tenorite, hematite, etc. Langbeinite and calciolangbeinite form a series of solid solutions, in which most of the compositions correspond to the ranges of (Mg2.0–1.6Ca0.0–0.4) and (Ca1.2–2.0Mg0.8–0.0). It is shown that, in calciolangbeinite, with a content of more than 20 mol

Atakamite with the empirical formula (Cu1.97Zn0.01)Cl0.94(OH)3.02, originating from the paleofumaroles of the monogenic volcano Vysota 1004 (Tolbachik, Kamchatka, Russia), has been studied by thermal and electron microprobe analyses, X-ray powder diffraction, IR and Raman spectroscopy, Calve microcalorimetry. Using X-ray diffraction and IR spectroscopy, the process of thermal decomposition of atacamite was studied. The enthalpy of formation from the elements for atacamite of the theoretical composition Cu2Cl(OH)3(−810.2 ± 7.7 kJ/mol) was determined by melt dissolution calorimetry and the Gibbs energy of formation (−657.0 ± 7.7 kJ/mol) was calculated. Based on the data obtained, thermodynamic modeling of the stability of atacamite in the Cu–O–Cl–H system was carried out, and the boundaries of its stability were calculated under conditions of high alkalinity and high acidity of the mineral-forming medium.

This paper in focused on the data for ludwigite and yuanfuliite of the new fumarolic genetic type. These ferric–magnesian borates (oxoborates) have been found in exhalations of the Arsenatnaya fumarole at the Tolbachik volcano in Kamchatka. They occur in mineral assemblages formed at temperature above 550°С. Ludwigite is primarily associated with anhydrite, diopside, berzeliite–scháferite series minerals (garnet supergroup), tilasite, svabite, calciojohillerite, hematite and rhabdoborite-group minerals, whereas yuanfuliite is associated with hematite, forsterite, enstatite, diopside, fluorophlogopite, magnesioferrite, and spinel. The replacement of ludwigite by yuanfuliite was observed. Both oxoborates are represented by previously unknown chemical varieties, almost free of minor Fe 2+ , Al, and Ti. Ludwigite is enriched in Mn 3+ up to composition (Mg 2.05 Cu 0.01 ) 2.06 ( Fe_0.71^3 + Mn_0.29^3 + Cr 0.01 ) 1.01 [B 0.96 O 3 ]O 2 . Yuanfuliite is chemically very close to the ferric endmember of warwickite–yuanfuliite series and contains only minor Sn; its typical composition is Mg 1.10 Fe_0.91^3 + Sn 0.03 [B 0.98 O 3 ]O. The orthorhombic unit-cell parameters of ludwigite and yuanfuliite are: a = 9.297(6), b = 12.349(7), c = 3.021(2) Å, V = 346.5(4) Å 3 ; and a = 9.30(4), b = 9.43(3), c = 3.051(13) Å, V = 268(2) Å 3 , respectively. Raman spectra of ludwigite with variable contents of admixtures, yuanfuliite, and warwickite are given and discussed.

Fluoborite extremely close to the fluorine endmember of the fluoborite Mg3[BO3]F3–hydroxylborite Mg3[BO3](ОН)3 series has been found in exhalations of the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. The proportion of the molecule Mg3[BO3](ОН)3 in it does not exceed 1 mol