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The paper reports comprehensive petrological, geochemical and mineralogical studies of osumilite-bearing andesite-dacitic lavas of Kordieritoviy Volcano (Keli Highland, Greater Caucasus) erupted at the end of the Pleistocene (about 200 ka). The petrographic and microprobe analysis showed that the rocks contain three paragenetic mineral associations: (1) "xenogenic" (metamorphic) association consisting of garnet (XPrp = 0.42, XAlm = 0.51–0.53, XGrs = 0.04–0.05) + hercynite + sapphire + bronzite + pargasite + ilmenite; (2) early magmatic association represented by hypersthene + hercynite + garnet (XPrp = 0.21–0.31, XAlm = 0.52–0.71, XGrs = 0.04–0.13) + ferro-kaersutite + ilmenite; (3) late magmatic association including hypersthene-ferrohypersthene + labradorite + garnet (XPrp = 0.04–0.14, XAlm = 0.65–0.81, XGrs = 0.06–0.18) + osumilite-(Mg) + phlogopite + tridymite + ilmenite + apatite. The osumilite-(Mg) (phenocrysts, xenomorphic aggregates in the rock matrix, and crystals in miarolic cavities), the average formula for dacites of Kordieritoviy Volcano can be written as (K0.73Na0.06Ca0.02 )1.00(Mg1.06 Mn0.04)2.00(Al2.75 Ti0.01)3.00(Si10.34Al1.66)12O30, formed mainly at late magmatic stages – in intermediate chambers immediately prior to the rise of the melt to the surface or after its eruption. Accordingly, this mineral in the studied lavas has a purely magmatic origin. Thermobarometric calculations and petrological modeling showed that the deep magma chamber of Kordieritoviy Volcano was located at a depth of 45–53 km near the Moho discontinuity. The temperature of the melt at the early magmatic stage was no less than 1100°C at 17–23 kbar. Crystallization of osumilite-(Mg) in intermediate magmatic chambers (at depths of 30–40 km) and during the lava ejection occurred at 1030–870°C and pressure progressively decreasing from 14–9 to 1 kbar. A petrogenetic model has been proposed to explain the genesis of exotic osumilite-bearing lavas of Kordieritoviy Volcano. It includes several stages: (1) formation of an enriched upper-mantle source (lithospheric mantle metasomatized by permanent interaction at the Moho discontinuity with the overlying lower crust composed of metamorphosed terrigenous-volcanogenic complexes); (2) generation of "dry" basaltic magmas in the source; (3) crystallization differentiation in the source (fractionation of olivine and chromium spinels) with the formation of a "dry" overheated andesitic melt; (4) limited-scale assimilation of the lower crustal material made up of leucocratic granulites by highly differentiated andesitic melts rising to the surface, with simultaneous fractionation of garnet, orthopyroxene and ilmenite from the melt. [ABSTRACT FROM AUTHOR]

A comparative study of impact glasses from the Lonar crater, located on the Deccan basalt plateau, India, and impact glasses from lunar regolith delivered by the Soviet automatic stations (AS) Luna-16 and Luna-24 (Sea of Plenty and Sea of Crises) was carried out. Numerous natural alloys (Cu3Ni2, Ni2Cu and Ni3Cu) that were previously unknown in nature were discovered in the impactites of the Lonar crater and the regolith of the Moon. The discovery of such alloys expands the area of isomorphism in the Cu–Ni system. As a result of a comparison of impactites of the Earth and the Moon, similarities were discovered in the composition, size and morphology of particles of copper–nickel alloys, which may be an indicator of impact processes. One of the possible mechanisms for the formation of Ni–Cu particles was condensation from a gas–plasma cloud. A possible source of material for Cu–Ni alloys was both the impactor material and the target material. [ABSTRACT FROM AUTHOR]

Studies of lunar regolith delivered to Earth by the Soviet automatic station (AS) Luna-24 using highly local electron microscopy methods made it possible to obtain data confirming the migration of sulfur during cooling of metal melts during the process of liquation. As a result, local Fe-S concentrates are formed, and part of the sulfur is displaced outward, forming sulfur shells on the surface of the melt droplets. Their formation on the surface is associated with the evaporation-condensation process during the cooling process of iron balls. The resulting sulfur coatings can be preserved if they are preserved in glass or under thin films of silicate condensate. [ABSTRACT FROM AUTHOR]

Native cobalt was found in amphibolite of the Kola superdeep borehole (SG-3) from a depth of 9630 m by a complex of local analytical methods (analytical scanning electron microscopy, electron backscatter diffraction). The studied amphibolite is a fine-grained melanocratic rock composed mainly of magnesioferri- hornblende and containing accessory native metal, telluride, sulphotelluride, and sulphide (Au, Ag, Pd, Bi, Cu, Pb, Zn, Sb, and Fe) mineralization.It also includes the clinopyroxene xenoclast carrying a fundamentally different set of accessories—poor in sulphides and including native cobalt. The absence of significant impurities, including iron, in native cobalt and its belonging to the hexagonal α-modification was determined. It is shown, that the metallic cobalt particles exposed during ion polishing of a compact pyroxene matrix cannot be a contaminant, introduced into the sample during drilling and sample preparation. Cobalt, obviously, was formed not only before the stage of retrograde metamorphism and subsequent hydrothermal processing of the amphibolite containing it, but probably long before the formation of the sedimentary protolith of this rock. That is, native cobalt belongs to the early high-temperature mineral phases inherited from the older Proterozoic—Archean main volcanism, while the time of formation of this layer of amphibolites dates back to the age of 2.4 billion years—the Early Karelian era of the Proterozoic. [ABSTRACT FROM AUTHOR]

The Lonar crater (India) is the best preserved and most studied on Earth, formed in basalts, which makes it possible to conduct a comparative study with impact transformations of mineral matter on the Moon and other planets of the Solar System. Comparative studies have shown that impactor material, both on the Earth and on the Moon, is present in impactites not only in a geochemically dispersed form, as previously thought, but also in the form of individual submicron particles distributed in the molten target material. These are particles of native nickel, taenite, and high-nickel kamacite, which, apparently, are the transformed material of the impactor. High-nickel submicron metal inclusions are widespread in the impactites of the Lonar crater, as they were found in all studied preparations made from materials collected from different points along the rim of the crater. The high-nickel particles found in this study are an additional argument in favor of the previously stated assumption about the chondrite type of impactor. [ABSTRACT FROM AUTHOR]

The crystal structure of the rare mineral caryochroite is determined for the first time using X-ray diffractometry and electron microdiffraction data. The new idealized crystal formula of the mineral is [Na(Sr0.5Ca0.5)Mg]3[Fe Mn()]10(Ti2Si12)O37(OH)14(Н2О)3. The parameters of the monoclinic unit cell refined by the least square method are a 16.550(3), b 5.281(2), c 24.25(3) Å, β 93.0°, Z = 2, space group P2/n. The crystal structure of caryochroite is a new type of Ti–Si lattice responsible for the large structural channels, which are able to enclose the exchange cations and a high amount of water components (OH groups and H2O molecules). [ABSTRACT FROM AUTHOR]

The lunar regolith delivered to Earth in the 1970s by the Soviet automatic stations Luna-16, -20, and -24, despite the small amount of material, is of great value for science and requires careful study. However, since soil samples have gone quite a long way from the moment of extraction to direct examination, there is a danger of possible contamination of the samples with foreign material, both man-made and terrestrial natural minerals. The probability of contamination of the finest fraction of regolith, the particle size of which is less than 100 microns, is especially high, since their detection is possible only by electron microscopy. Using the methods of analytical scanning electron microscopy in regolith samples, contaminant phases that contaminated the original preparations were found, and the sources of these artifacts were shown. The examples of contamination of regolith samples given in this paper and the methods for their identification will make it possible in the future to more accurately diagnose the phases of lunar origin. [ABSTRACT FROM AUTHOR]

Polycomponent condensate glasses found in nature provide an insight into condensation mechanisms, which are still understood inadequately poorly. Condensate glasses found in the impactites of the Lonar crater contain nanosized inclusions of metallic Fe, Cr, Cu, Zn, Ag, In, Te, Au, Pt, and Bi, along with Fe, Cu, and Zn sulfides. This combination may be indicative either of a brief condensation window for the almost simultaneous condensation of components with so different fugacity or of a possible mechanism of cluster condensation, provided that the condensation temperatures of such clusters are close. [ABSTRACT FROM AUTHOR]

An extended isostructural solid solution (isomorphic series) between arsenate and vanadate of the garnet supergroup — berzeliite (NaCa2)Mg2(AsO4)3 and schäferite (NaCa2)Mg2(VO4)3 — was studied for the first time. The studied material is from sublimates of the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka. These minerals here form aggregates of yellow or orange transparent crystals (up to 1 mm in size). Anhydrite, forsterite, diopside, andradite, hayuin, potassium–sodium feldspars, hematite, magnesioferrite, spinel, barite, aphtitalite-like sulfates, minerals of the powellite–scheelite series, ludwigite, calcium chillerite, paraberzeliite, members of the series rhabdoborite–(V)–rhabdoborite–(W)–rhabdoborite–(Mo), apatite–swabite–pliniusite, tilasite–isokite, udinaite–arsenudinaite, and wagnerite–arsenovagnerite associate with the studied minerals. They were formed under the oxidizing conditions at temperatures not lower than 550°С. The composition of the tetrahedrally coordinated components in the schäferite–berzeliite isomorphic series in the Arsenatnaya fumarole continuously varies from (V2.54As0.48P0.04Si0.01) to (As2.77V0.22Si0.03P0.01). The XCa2+ + ZSi4+ = XNa+ + Z5+ heterovalent isomorphism scheme plays a subordinate role. The crystal structures of three samples (space group Ia–3d) with different As : V ratios were studied: The dimorphism of the garnet supergroup and alluodite group arsenates is discussed. [ABSTRACT FROM AUTHOR]

Palladium mineralization was registered in the Kola superdeep borehole (SG-3) for the first time in samples from deep horizons (in the fault zone at ~10 km). A proper palladium mineral (merenskyite) with the formula Pd1.00(Te1.21Bi0.79)2.00 was detected using the analytical electron microscopy and EBSD methods. The unusually high content of bismuth in the discovered merenskyite crystal most likely indicates the lower temperatures of its formation from a bismuth-rich fluid. This is supported by numerous finds of associated bismuth minerals (native and intermetallic minerals, sulfides, tellurides, and sulfotellurides) as well. A close geochemical association of noble and rare elements was revealed in the composition of the rich and diverse ore mineralization in the samples studied. It can be argued that a new type of mineralization was discovered for the SG-3 rocks: noble metal (Au–Ag–Pd) rare-element (Bi–Te). [ABSTRACT FROM AUTHOR]

The results of long-term mineralogical studies of the lunar regolith, obtained using analytical scanning and transmission electron microscopy, are presented. These studies revealed 105 mineral phases new for the Moon, 43 of which were discovered for the first time under natural conditions; an electronic link to the final table is given. An example of studying condensate glasses and native molybdenum is presented. [ABSTRACT FROM AUTHOR]

A high-calcium high-temperature condensate is detected in the Earth's impact Lonar crater for the first time. Its finding confirms in practice the theoretical conclusions made earlier from the experimental results. The high-silica condensate found in the Lonar crater, which is similar to those ones in the Zhamanshin crater and in the lunar regolith, confirms the absence of a correlation between the compositions of the target and the impact condensates. The presence of high-temperature condensate glasses in ring structures may be one of the diagnostic criteria to differentiate between volcanogenic and impact formations. [ABSTRACT FROM AUTHOR]

Dispersed radioactive ore mineralization (uranium blacks) in paleovalley deposits of the Vitim uranium-ore region (Buryat Republic) has been studied by a set of methods of analytical electron microscopy (SEM, TEM).The ore component, tetravalent uranium phosphate ningyoite, in the form of micrometer crystalline mineraloid precipitations is represented in all kinds of host rocks (sands, bedding granites, overlapping basalts). The previously little known phosphate-black uranium ores are new-for-Russia type of industrial ores. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070140 [ABSTRACT FROM AUTHOR]

For the first time, a high-temperature condensate in the form of two-component glass beads of about 200–400 nm size, consisting of an Al–Ca oxide core rimmed by a uniform oxide film of high-silica glass containing iron nano-inclusions, has been found in natural samples of the lunar regolith from Mare Crisium (Luna-24). Earlier, a high-temperature condensate was only theoretically predicted on the basis of laser evaporation experiments. [ABSTRACT FROM AUTHOR]

The Raman spectroscopic studies of the lunar regolith from the samples of the Luna 24 automatic station resulted in recognition of the occurrence of three structural modifications of carbon: amorphous sp2-carbon, schungite-like carbon, and turbostratic graphite. [ABSTRACT FROM AUTHOR]

The paper presents pioneering data on the comparative study of impact glasses from the Zhamanshin crater and lunar regolith (delivered by the Luna 16, 20, and 24 probes). The data were acquired using analytical techniques of ultrahigh spatial resolution. Many of the melt and condensate impact glasses, both terrestrial and lunar, are similar in inner structure and composition, which were controlled primarily by the physics of the impacts and similar compositions of the targets. [ABSTRACT FROM AUTHOR]

For the first time, high-purity native cobalt was detected in two preparations from a lunar regolith sample delivered by the Luna 24 automatic station. Presumably, it was formed during the condensation of a substance from an impact gas-plasma cloud. Previously, native cobalt of similar purity was observed only in products of low-temperature hydrothermal alteration of hyperbasites. [ABSTRACT FROM AUTHOR]

A 3-µm particle of HgS is found by electron microscopy techniques in studying the lunar regolith samples delivered by Apollo 17. It might have been preserved due to a thin cover of highly siliceous glass, having protective functions. This particle was likely formed from a gaseous phase by the condensation of Hg and S vapors. [ABSTRACT FROM AUTHOR]

The close intergrowth of two native alloys of the compositions Ni0.59Cu0.24Al0.15Fe0.01Mn0.01 and Pd0.55Pt0.36Rh0.09 with a size of 10 μm has been discovered in the regolith from the Mare Crisium. A conclusion on its exhalative origin is made. [ABSTRACT FROM AUTHOR]

Two cases of mineral associations from the samples of regolith delivered by AS Luna 20 and AS Luna 24, which indicate possible hydrothermal alteration of primary lunar rocks, are considered. The probability of hydrothermal processes on the Moon means a drastic change in the firm views of the processes of the formation of lunar mineral. [ABSTRACT FROM AUTHOR]

Using high-resolution analytical electron microscopy, heterogeneous fragments of cosmogenic substances, such as nickelphosphide Ni3P and the unnamed intermetallide ZnAl2, are detected for the first time for a large meteorite crater, the Zhamanshin circular structure. Due to the impossibility of simultaneous finding these phases in the same meteorite, an assumption is made on the cometary nature of the impactor of the Zhamanshin crater. [ABSTRACT FROM AUTHOR]

Particles of tantalo-niobate of the ferrotantalite-manganotantalite series are discovered for the first time in two lunar regolith fragments delivered by the Apollo-17 mission. Allochtonous and autochtonous mineralization that accompanies tantalo-niobate in the regolith is described. An attempt is made to explain the formation of tantalite in anorthosites of the continental region of the Moon. [ABSTRACT FROM AUTHOR]

The article discusses the discovery of new mineral phases containing lanthanoids and actinoids from the regolith samples delivered to the earth by the automatic station Luna-24. It discusses several particles of REE carbonate as well as observes several particles with fractionated REE including lanthanum, cerium, and gadolinium as well as uranium-bearing phase. Regolith fragments were studied in back-scattered electrons on a scanning microscope and the element composition was examined for the fragments with a higher average atomic number in comparison with the silicate matrix.