Vol CLIV, No 1 (2025)

Mesozoic subduction-related gabbroic and ultramafic rocks from the Ildeus and Lucha intrusions in the central part of the Stanovoy superterrane contain microinclusions of iron-titanium oxides (magnetite, titanomagnetite, ilmenite, rutile, and titanite), apatite, sulfates (barite) and sulfides (pyrite, pyrrhotite, and chalcopyrite). Earlier, we attributed these minerals to the indicator ITOASS (Iron-Titanium Oxide–Apatite–Sulfate–Sulfide) assemblage for the Iron Oxide-Copper-Gold (IOCG) and Iron Oxide-Apatite (IOA) mineralization. The ITOASS assemblage is associated with hematite, silver chlorides, and native gold. Host minerals for ITOASS microinclusions are mostly plagioclase, pyroxenes, and high-Al amphibole, suggesting the late-stage magmatic origin of them. Late-stage magmatic amphiboles carry textural and compositional evidence for early stages of metasomatic alteration of minerals of ITOASS assemblage, that possibly indicate hydrothermal-metasomatic (autometasomatic) stage of the evolution of IOCG-IOA-type ore systems. We conclude that microinclusions of the ITOASS assemblages can be used for regional prespecting of iron oxide copper-gold and iron-oxide mineralization in accretionary-collisional structures of the Russian Far East.

In chromitites of northern part of the Voikar-Synya ultramafic massif, which is part of the Khadatinsky ophiolite belt of the Polar Urals, native osmium, Ir-containing native osmium, native iridium, hongshiite, As-containing laurite, Ru-Os-containing pentlandite, kuvaevite, unnamed PGE sulfide with non-ferrous metals, close in stoichiometry to formula Me₂S₃ (Me = Os, Ru, Cu, Pt, Ir, Fe, Pd, Ni, Rh), high-temperature metallic solid solution (Pd, Pt, Fe), stibiopalladinite, geversite, genkinite, unnamed PGM close in stoichiometry of formula (Pd, Ni, Rh)₅AsSb, Pd₃Sb and (Ni, Rh, Pt)Sb were the first time discovered and characterized along with previously known platinum group minerals (PGMs). The set of PGMs of massif has been expanded from 10 to 25 mineral spicies and varieties. PGMs from high-alumina chromitites are characterized by wider variety than those from high-chromium chromitites (15 and 9 mineral species, respectively). PGMs of both Os–Ir–Ru and Pt–Pd specializations were found in high-alumina chromitites. High-chromium chromitites are characterized mainly by Os–Ir–Ru specialization. Such feature of PGMs distribution is explained by low degree of partial melting of mantle source of high-alumina chromitites, compared to high-chromium chromitites, which experienced high-temperature partial melting with removal of easily mobile Pd group of PGMs in composition of melted basaltic melt. New data have been obtained on noble metal minerals in the composition of primary and secondary chromitite assemlages.

Thermal transformations of ornamental pink haüyne from the Malo-Bystrinskoye lazurite deposit in the Baikal region containing S₄ molecules as a chromophore were studied using electron microprobe analysis, synchronous thermal analysis, high-temperature X-ray diffraction and Raman scattering methods. A scheme of transformations of the S₄ molecule with the formation of a blue chromophore, the S₃^•– radical anion, was proposed. The upper temperature limit of the existence of sodalite group minerals with S₄ molecules (about 400 °C) was established.

A single-crystal X-ray diffraction study of novel natrural uranyl-vanadate phase, discovered in the rocks of the Hatrurim formation and close in composition to the mineral strelkinite, has been carried out. The studied crystal is orthorhombic, space group Pccn, a = 13.355(3), b = 8.2368(7), c = 10.6180(11) Å, V = 1168.0(3) ų, Z = 4, R₁ = 0.179, CSD2409185. The crystall chemical formula obtained in a course of the X-ray diffraction experiment is (Na_1.12K_0.88)(UO₂)₂(V₂O₈), which is in a good agreement with that calculated from the chemical analysis data (Na_1.16K_0.78) _Σ1.94(U_1.005O₂)₂(V₂O₈). Despite the high convergence parameters, the structural model can be considered as quite reliable, especially in the part of the uranyl-vanadate layers of the carnotite type. Strong diffuse scattering does not allow more precise refinement of the partially disordered sites of the interlayer cations. The mutual arrangement of the vanadate pyramids dimers in neighbor layers is unique in comparison with the crystal structures of other carnotite group minerals and related synthetic phases. It can be assumed that the studied phase is potentially a new mineral species — a dehydrated analogue of strelkinite — which cannot be approved yet due to the lack of sufficient material. Then, by analogy with tyuyamunite—metatyuyamunite pair, it can be called “metastrelkinite”.

The author has developed a computer program oriented towards ordinary work with large arrays of mineral chemical analyses, including the use of SEM images. The article describes briefly the main approaches and functionality of the program, which is now available to a wide range of users.