Vol 148, No 2 (2019)

General section
Paleoproterozoic alkaline magmatism of the Murmansky neoarchaean craton, Kola peninsula
Petrovskiy M.N., Petrovskaya L.S.

The article represents results of geological, geochronological and isotope-geochemical studies of the alkaline-ultrabasic massif located in the lower reaches of the Iokanga River in the Karelian-Kola Alkaline Province. The alkaline-ultramafic massif is composed of nepheline clinopyroxenites, nepheline gabbroids, malignites, and nepheline syenites. These rocks are of Paleoproterozoic age. The age of crystallization determined for nepheline clinopyroxenites by the 40Ar/39Ar phlogopite method is 1955 ± 10.8 Ma, and Rb-Sr isochron over the entire pool of samples of the intrusive rocks corresponds to an age of 1937 Ma, at ISr = 0.70316. According to their isotope-geochemical Sm-Nd and Rb-Sr characteristics, rocks of the alkaline-ultrabasic massif in the lower reaches of the Iokanga River have the mantle origin, and the source of their melts was apparently a mantle of the BSE type.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019;148(2):1-11
Mineral and geochemical characteristics, composition of initial melt, and parameters of crystallization for Dzhigda gabbroids (south-eastern framing of the Siberian craton)
Rodionov A.A., Buchko I.V.

Dzhigda gabbroid massif is a typical representative of the Permo-Triassic ultramafic-mafic intrusions in the south-eastern framing of the Siberian Сraton. The article presents results of calculations of the composition and crystallization parameters of the melt that produced the gabbroids. It is has shown that crystallization of the melt occurred at the pressure of 4—6 kbar and initial temperature of 1125—1160 °С. Fractionation of the melt led to the formation of gabbro and gabbrodiorites, on the one hand, and to the formation of gabbro and gabbro-diorites enriched with sodium, on the other hand. Analysis of available data shows that the compositions of the initial melt and crystallization parameters for Permo-Triassic ultramafic-mafic intrusions in the south-eastern framing of the Siberian Craton are significantly differ. Perhaps this is a characteristic of this stage of magmatism. In addition, rocks from these intrusions have obvious features of geochemical duality, which is a combination of signature as intraplate and suprasubduction origin.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019;148(2):12-27
On mechanisms of the accessory chromian spinel formation in plastic deformed crystals of enstatite from kraka massifs (Urals ophiolite belt)
Saveliev D.E., Musabirov I.I.

Tiny chromian spinel precipitations associated with plastic deformed enstatite crystals from spinel peridotite were studied. It is defined that there are several localizations of the precipitations: 1) in recrystallization zones where they coexist with olivine and enstatite neoblasts, 2) in the volume of polygonized primary enstatite crystals as lamellae and holly leaf grains, 3) in lamellae and neoblasts of diopside and pargasite which were formed during a plastic deformation of primary orthopyroxene. In the first two cases, we suggest the solid-state mechanism of their formation. First, it is a result of an impurities segregation on the structure defects (dislocation → subgrain boundary → grain boundary). Second, it is a result of the nucleation and growth of the new-formed mineral phases (spinel, forsterite, enstatite II) in most distorted places of porphyroclasts. In the third case, it is possible that chromian spinel were appears either as a result of the solid-state crystallization or as a cumulate of «diopside» or «pargasite» melts formed by frictional melting of orthopyroxene porphyroclasts in micro-chambers.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019;148(2):28-49
Origin of hypergene and technogene minerals in mining technogene systems (a case study of the dalnegorsk Region, Primorye)
Zvereva V.P., Kostina A.M., Lysenko A.I.

The paper displays results of modeling the physical-chemical parameters of crystallization for hypergene minerals in mine, slurry and drainage waters within mining technogene systems of sulfide-bearing ore deposits of the Dalnegorsk district. The modeling has been carried out with the software package «Selector». Eh and pH parameters were calculated, thermal conditions of the saturation of hypergenic minerals from solutions were determined, and mineral assemblages have been distinguished. It is shown that hypergenic and technogenic minerals crystallize in the wide range of temperatures (from –25º to +40ºC) with significant variations of Eh (from 0.6 to 1.2 V) and pH (0.3—13.7) values. The principal role in the formation of mineral parageneses belongs to the composition of ores and host rocks. The greater is grade of sulfides in tails of processing, the more acid solutions they are producing, and the greater is the number of newly formed secondary minerals.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019;148(2):50-60
New Minerals
Dalnegorskite, Ca5Mn(Si3O9)2, a new pyroxenoid of the bustamite structure type, a rock-forming mineral of calcic skarns of the Dalnegorskoe boron deposit (Primorskiy kray, Russia)
Shchipalkina N.V., Pekov I.V., Ksenofontov D.A., Chukanov N.V., Belakovskiy D.I., Koshlyakova N.N.

Dalnegorskite — the new pyroxenoid with the crystal-chemical formula Ca2Ca2MnCa(Si3O9)2, and the simplified formula Ca5Mn(Si3O9)2, is a rock-forming mineral in the boron-bearing calcareous skarns of the Dalnegorskoe boron-silicate deposit (Dalnegorsk, Primorsky Krai, Russia). It belongs to the structural type of bustamite and forms a continuous solid-solution series with the isostructural mineral ferrobustamite Ca2Ca2FeCa[Si3O9]2. These pyroxenoids form thinly-radiated banded beige, pinkish-white and milky-white aggregates typically consisting of split thin acicular to fiber-like individuals and are associated with hedenbergite, datolite, andradite, galena, sphalerite, and pyrrhotite. Dmeas. = 3.02(2), Dcalc. = 3.035 g·cm–3. Dalnegorskite is optically biaxial, negative, α = 1.640 (3), β = 1.647 (3), γ = 1.650 (3)°, 2Vmeas. = 75(10)º. The average chemical composition of the holotype (electron microprobe data) is: MgO 0.23, CaO 40.02, MnO 5.02, FeO 3.64, SiO2 50.65, total 99.56 wt.%. The empirical formula calculated on 18 O atoms is Ca5.03Mn0.51Fe0.36Mg0.04Si6.03O18. The crystal structure of the new mineral was refined by powder X-ray diffraction data using the Rietveld method, Rp = 0.0345, Rwp = 0.0444, R1 = 0.0790, wR2 = 0.0802. Dalnegorskite is triclinic, P-1, a = 7.2588(11), b = 7.8574(15), c = 7.8765(6) Å, α = 88.550(15), β = 62.582(15), γ = 76.621(6)º, V = 386.23(11) Å3Z = 1. Dalnegorskite is distinctly different from the related mineral wollastonite in the infrared spectrum. The wave-numbers of maxima of strong bands in the characteristic region of Si—O stretching vibrations in the IR spectrum of dalnegorskite are (cm–1): 905, 937, 1025, 1070. The type specimen of dalnegorskite is deposited in the collection of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia (No. 96201).

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019;148(2):61-75
Minerals and parageneses of minerals
Platinum group minerals from chromitites of Kempirsai ultramafic massif (the South Urals): new data
Yurichev А.N., Chernyshov A.I., Korbovyak E.V.

Kempirsai is the largest massif of ultramafites in the South Urals, it is well known for its unique chromite ore deposits. Grains of chromespinelides in massive chromitites of the «Diamond-Pearl» deposit contain small isolated inclusions of PGE minerals represented by solid solutions of Os—Ir—Ru and Rh—Zn—Pt (later system has been revealed in the massif for the first time), disulfides of the isomorphic laurite-erlichmanite series, and sulfides of the Ir—Ni—Cu system. Some grains of the metal Os—Ir—Ru solid solutions contain up to 45 wt % of ruthenium, extending previously known boundaries of the mixing range in this triad of elements. The main trend in the Os, Ru and Ir fractionation in sulfides is enrichment of disulfides in osmium and ruthenium; iridium is mostly concentrated together with Ni and Cu in sulfides with different metal-sulfur ratios. The process of mineral-forming of these PGE associations was developing in several stages. The earliest among them are metallic solid solutions of Os—Ir—Ru and disulfides of laurite-erlichmanite series; minerals of Rh—Zn—Pt and Ir—Ni—Cu systems are related to later events connected with repeated partial melting and injection of the newly formed melt into already formed restites, or processes of the mantle metasomatism.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019;148(2):76-86
Mineralogy of zirconium and niobium in calcite-nepheline-feldspar pegmatite of the ilmeny-vishnevogorsky complex (the South Urals)
Cherednichenko S.V., Kotlyarov V.A.

Composition of minerals of the pyrochlore group, columbite-(Fe), Nb-containing rutile, zircon, baddeleyite and zirconolite has been studied in the calcite-nepheline-feldspar pegmatite (12 × 2 m in size) located in the south-west endoсontact of the Ilmenogorsky miaskite massif. There were identified two generations among the pyrochlore group minerals and for baddeleyite. Early generations of fluorcalciopyrochlore and fluornatropyrochlore have high contents of Ti and REE (TiO2 9—18 wt %, ∑REE up to 12 wt %), the early generation baddeleyite contains Nb (Nb2O5 6.2 wt %). Minerals of the later generation have been found in the ilmenite crystal inside the coarse-grained nepheline. The later pyrochlore group minerals contain low quantities of Ti, REE (TiO2 3—5 wt %, ∑REE up to 3 wt %), the later baddeleite contains Hf and Y (up to 1 wt %) and it does not contain Nb. Zirconolite has been revealed as a new mineral for the complex. It was formed in the hydrothermal stage in association with cancrinite, stronalsite and gonnardite and it has the higher contents of REE, Th and Mn in its composition.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019;148(2):87-99
Intergrowths of corundum and spinel from the Thurein-Taung deposit (Myanmar)
Muromtseva A.V., Ponomareva N.I., Bocharov V.N., Zilicheva O.M.

The article displays data on formation conditions and features of unique corundum-spinel aggregates from the Thurein-Taung deposit in Myanmar (Burma). Chemical composition of corundum and spinel is given, and there is traced the effect of iron admixture on the coloring of spinel and parameters of its crystal lattice on the base of X-ray diffraction analysis. The surface of corundum on contact with spinel was studied in detail with aid of the color cathodoluminescence; it is shown that the process of overgrowing by spinel was preceded by resorption of corundum surface. Mineral and fluid inclusions in these minerals have been studied with use of microprobe analysis and the Raman spectroscopy. The temperatures of homogenization have been determined for liquid carbon dioxide in fluid inclusions inside corundum. On the base of mineral equilibria analysis in the Al—Mg—O—CO2—H2S—C system there were determined the optimal activities of magnesium and calcium and the fugacity of carbon dioxide. They are equal to аMg = 10–5аCa = 10–1 and fCO2 = 10–4. It was found that corundum-spinel aggregates formed at temperature about 400 ºС as a result of partial dissolution of corundum protocrystal by high-temperature solutions containing Mg and Ca. Crystallization of the spinel took place with increasing pH (>3.5) and a decrease of redox potential (Eh ≤ –0.3 V).

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019;148(2):100-114
Discussions, bibliography, reviews
Ontogenetic orientations to choose the model of the formation of platinum-bearing mineralization in zonal clinopyroxenite-dunite massifs of the Urals
Kozlov A.V., Stepanov S.Y., Palamarchuk R.S., Minibayev A.M.

Results of ontogenetic studies of the early paragenesis of ore minerals in zonal clinopyroxenite-dunite massifes of the Middle Urals are discussed. It is shown that the formation of these minerals occurs in the following order: iridosmium → chrome-spinel → laurite-erlichmanite → оsmiridium → isoferroplatinum. Revealed ontogenic features of ore phases are in good agreement with models suggesting the concentration of platinum group metals at the magmatic stage of evolution of the clinopyroxenite-dunite massif before display of the superimposed high-temperature plastic deformation.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019;148(2):115-130

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