Tetrahedrite-(Cd), Cu10Cd2Sb4S13, is a member of the tetrahedrite series of the tetrahedrite group with a predominance of Cd at the C position typically occupied by divalent metals. Cadmium end-members from the tetrahedrite group are rare: they have been described in 15 deposits and ore occurrences. This work reports on a new discovery site of Ag-bearing tetrahedrite-(Cd) at the Kon-Dara mineral deposit (Southwestern Pamirs, Tajikistan) and summarizes the known data on rare Cd-bearing fahlores with a Cd content from 1 to 12.31 wt

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23050203

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23050215

Fahlore crystals and aggregates from the Darasun gold deposit show complex rhythmic-oscillatory chemical zoning resulting from crystal growth and coupled dissolution-reprecipitation reactions. Formation temperatures of these zonal fahlores were determined using the Raabe Sack (1984) geothermometer and results of 2780 microprobe analyses. Fahlore is a nearly complete solid solution between tetrahedrite-(Zn) and tennantite-(Fe) with ratios of Sb/(Sb + As) of 0.02–0.85 and Fe/(Fe + Zn) of 0.15–1.00, and exhibits a negative interdependence between these ratios consistent with the thermochemical incompatibility of As and Zn in fahlores. Fahlore compositions in the deposit exhibit scale invariance. The crystallization temperatures for zonal growth crystals of tennantite-(Fe) are from 115 to 314°C, vary from grain to grain and from rhythm to rhythm in individual grains, are similar to those for zonal-heterogeneous fahlore aggregates, from 115 to 290°C, and are in agreement with temperatures obtained for fahlores using fahlore-sphalerite (177–395°C) and fahlore-bournonite-seligmannite (117–316°C) geothermometers, with all of these temperatures being lower than the 284–395°C homogenization temperatures of fluid inclusions in coexisting quartz. Although overlapping in temperatures the general sequence of fahlores precipitated with decreasing temperature was: tetrahedrite + sphalerite → tennantite + sphalerite → fahlore + bournonite-seligmannite → zoned tennantite-(Fe) grains → pseudomorphic zonal-heterogeneous fahlore aggregates. The reasonable temperatures suggest that oscillatory zoning was created at nearly constant temperature and Fe(Zn)–1 exchange potential. About 30–40

The plutonic rocks studied in the Ashadze Complex contain four groups of mineral assemblages: (I) coarse-grained gabbronorite, which is dominant; (IIa) micrograined differentiated gabbro (oxide microgabbro) enriched in ilmenite and apatite and sporadically containing zircon grains smaller than 70 µm; (IIb) local oxide microgabbro aggregates with zircon grains as large as 200 µm and quartz; and (III) biotite- and orthopyroxene-bearing plagiogranite veinlets. As an interpretation, a model of sequential differentiation of MORB-type melt is proposed. The compositional variations of the plagioclase and orthopyroxene are consistent with the general sequence of crystal fractionation and show partial overlap of assemblages (II) and (III). In the sequence of zircon-bearing assemblages (IIa), (IIb), and (III), zircon shows a systematic enrichment in Hf. Zircon of assemblage (IIb) hosts melt inclusions. The inclusions were completely remelted at 910°C and quenched into homogeneous glass. The analyzed granitoid (75–76 wt % SiO2) water-bearing (H2O ~ 3 wt %) composition of the inclusions was interpreted as a residual melt after crystallization of the evolved vein gabbro rich in ilmenite. The results offer an example of an evolved granitoid product of MORB differentiation and are consistent with high-degree magmatic differentiation in the oceanic crust, a model according to which the crystallization of evolved oxide gabbro results in a residual silicic melt.

Despite the local occurrence of silicic magmatism during the formation of the oceanic crust, the nature of felsic granitoid veins (“oceanic plagiogranite”) remains an important debatable problem of chemical differentiation in the global system of mid-oceanic ridges. To date, the actual compositions of granitoid melts in the modern oceanic crust are still poorly constrained, and this complicates petrogenetic interpretations. The structural patterns and compositional variations of minerals from the oceanic core complex at 13° N on the Mid-Atlantic Ridge show the sequence of magmatic differentiation: coarse-grained gabbronorite → vein microgabbro enriched in Fe–Ti oxides and apatite → biotite–plagiogranite veins. The transition to silicic magmatism corresponds to the local crystallization of quartz and zircon in the vein microgabbro with the further Zr/Hf fractionation by zircon. Experimental study of melt inclusions in zircon demonstrated homogenization at 850–910°C and the granitoid composition of the melt with K2O >1.8 wt % and SiO2 of 75–76 wt %. Such a K/Si ratio of the silicic melt, along with the genetic relation to highly differentiated gabbroids, allows us to prefer the model of a high degree differentiation of MORB-type magma in the oceanic core complex for the studied plagiogranite–gabbro association.

A study on the typomorphic characteristics and age of the monazite the two giant titanium deposits of the Timan – Pizhemskoye and Yarega, which revealed differences in morphology in the species composition of the inclusions, the grain size, distribution of chemical types of a mineral associated with conditions of crystallization and different sources of the substance. The isochronous Th-Pb monazite age was calculated using the «CHIME» method. For Yarega monazite built three isochrone with age 1301, 1105 and 778 Ma; for Pizhemsky monazite-kularite one isochrone with age 782 Ma. Source of hith-Th monazite Yarega oil-titanium deposit could be ancient granite batholith and the origin Yarega less-Th monazite and Nd-Ce-monazite-kularite Pizhemskoye deposit with an age of ~ 780 Ma could be related to the hydrothermal conversion of the weathering crusts on lamprophyres close in age with lamprophyre (spessartite and kersantite) of Chetlassky Kamen.

In many types of hydrothermal ore deposits Au occurs in invisible state in most common minerals of the Fe-As-S system. It is supposed that the state of theinvisible Au may beeither non-structural (nano-sized inclusions of metal and its compounds) or chemically bound (isomorphous solid solution). Here we report results of investigation of the state and the concentration range ofinvisible Au in synthetic and natural arsenopyrites FeAsS (Vorontsovka deposit, North Urals, type Carlin). Conditions that favor the formation of Au-bearing arsenopyrite were identified. The synthesis experiments were carried out in Au-saturated system by means of salt flux method with a stationary temperature gradient. The temperature at the cold end of the ampole was 400500С. The chemical composition of arsenopyrite was determined by electron probe microanalysis. The composition of the synthesized arsenopyrite varied within [at.%]: Fe from 32.6 to34.4, As from 30.0 to 36.5, S from 29.4 to36.0. The Au content in arsenopyrite varied from the detection limit ( 45ppm) to 3wt.%. A strong negative correlation between the concentrations of Au and Fe was observed in the synthesized arsenopyrite grains. The slope of the correlation lines corresponds to the formation of the Au-bearing solid solution where Au isomorphically substitutes for Fe at the parameters of the synthesis experiments. In addition, there is a weaker positive correlation between Au and As: higher Au concentrations are characteristic of arsenic-rich compositions (As/S [at.%] 1) and those close to stoichiometric arsenopyrite, whereas in sulfur-rich arsenopyrite the concentration of Au is lower and does not exceed 0.25wt.%. The positive Au-As correlation appears not only on a local level within a single crystal of synthetic and natural arsenopyrite, but is valid on the Vorontsovka deposit scale: As-rich arsenopyrite formed at lower temperature and sulfur fugacity (t= 250370C, logfS2= 1217) contains more Au than the As-poor early arsenopyrite (t= 270400C, logfS2= 79). Comparison of these results with the literature data shows that the positive correlation between the concentrations of Au and As in arsenopyrite and the negative correlation between the concentrations of Au and Fe are the common features of ores of the Carlin-type deposits. We suggest that, in contrast to negative correlation Au-Fe, the positive correlation Au-As cannot be explained in terms of crystal chemistry, but can result from the effect of external factors among which are the difference in composition of ore-forming hydrothermal fluids and the sulfur fugacity.

Mineral associations, intergrowth features, chemical composition and Sb and As distribution in coexisting fahlore and bournonite-seligmanite solid solutions in the Darasun gold deposit were studied. For the first time the almost complete solid solution was found between bournonite and seligmanite with a continuous isomorphism between Sb and As in the range of Sb/(Sb + As) ratios from 0.21 to 1.00 in the Darasun deposit by EMPA. The composition of the fahlore coexisting with bournonite varies widely: Sb/(Sb + As) ratios 0.03-0.96 and Fe/(Fe + Zn) ratios 0.36-0.87. The coupled compositional evolution from early antimony to late arsenic in coexisting solid solutions has been established. Based on the investigation of the Sb and As distribution between coexisting fahlore and bournonite-seligmanite, the temperatures of their joint deposition and, as a result, of the productive stage, in which they are closely associated with native gold and tellurides (90–335 °С), are estimated.

Heterogeneous rhythmic–zonal aggregates of tennantite-IV partly or completely replacing early homogeneous Zn-tetrahedrite-I grains and euhedral (Fe–Zn)-tennantite-I crystal were found in ores of the Darasun gold deposit. The different stages of fahlore replacement were observed. This initiates at grain boundaries and is terminated by a complete transformation into pseudomorphic, newly formed (Zn–Fe)-tennantite-IV aggregates surrounded by Zn-tetrahedrite-IV. These aggregates closely associate with bournonite and galena, and their precipitation initiated the formation of pseudomorphs. As is evident from the results of EMPA, (Fe–Zn)-tetrahedrite enriched in As in relation to Zn-tetrahedrite-I was precipitated at the initial stage. Tennantite with wide variations in the Sb/(Sb + As) and Fe/(Fe + Zn) ratios predominates in zonal heterogenous aggregates. There is a negative correlation between Sb/(Sb + As) and Fe/(Fe + Zn) ratios in (Fe–Zn)-tetrahedrite–tennantite-IV. In all sites, there is a miscibility gap between As and Sb and a sharp decrease in Sb/(Sb + As) ratio and increase in Fe/(Fe + Zn) ratio at the contact between Zn-tetrahedrite-I and newly formed (Fe–Zn)-tetrahedrite–tennantite-IV. The sharp zigzag boundaries between Zn-tetrahedrite-I and tennantite-IV and pores in newly formed aggregates provide evidence for coupled dissolution–precipitation reactions. The dissolution was initiated by disequilibrium between Zn-tetrahedrite-I and undersaturated fluid due to the precipitation of galena and bournonite. The precipitation of tetrahedrite–tennantite-IV occurred under the conditions of oscillation in Sb/(Sb + As) and Fe/(Fe + Zn) ratios due to the gradient of concentrations in the fluid. The temperature of crystallization of zonal heterogenous tennantite-IV aggregates ((134–161) ± 20°С) was calculated by the sphalerite–fahlore geothermometer. Instability of early Zn-tetrahedrite-I results from hydrothermal fluid cooling, decrease in fluid salinity, and change in the tetrahedrite and tennantite solubility due to the evolution of the conditions of semimetal migration.

Four ureilites subjected to impact metamorphism in a pressure range of ~15–100 GPa were investigated for mineralogical and petrological features and optical luminescence of their diamonds with the aim to understand how properties of ureilitic diamonds are correlated with shock and thermal histories of the host meteorite. Petrological data show that all the investigated ureilites experienced multistage metamorphic histories. Some of them were shocked at least twice or/and underwent high‐temperature thermal metamorphism and fluid metasomatism in the parent body interior. Photoluminescence spectra of individual diamond grains reveal the presence of neutral and negatively charged nitrogen‐vacancy (NV 0 and NV − , respectively) and H3 (two nitrogens and a vacancy) defects, indicating relatively high nitrogen contents of the diamonds and some degree of thermal annealing of the grains. The diamond grain size and morphology, a texture of graphite‐diamond aggregates, and spectroscopic properties of the diamond phase vary widely both within an individual meteorite and between the ureilites. Shock‐driven transformation of sp2‐C into diamond provides the most natural explanation of the observed spectroscopic diversity of the diamond grains if one takes into account strong dependence of the PT parameters and efficiency of the transformation on structure of the carbonaceous precursor.

The partitioning of Fe and Zn between coexisting fahlore and sphalerite and fluid inclusions in sphalerite from the Darasun gold deposit have been studied. These data were used to estimate the formation temperature of the minerals by the sphalerite–fahlore geothermometer. The calculated crystallization temperature of 175–355°С is close to the homogenization temperature of fluid inclusions in sphalerite of 225–385°С.The estimated pressure for fluid inclusion trapping ranged from 340 to 1420 bar. The sulfur fugacity obtained from the FeS content in sphalerite associated with pyrite and the calculated temperature ranges from 10–5.5 to 10–11 bar.

Based on the investigation of melt inclusions in minerals using electronic and ion microprobe analysis, we estimated the composition and evolution of the melts involved in the formation of comendites of the bimodal association of Sant’s volcanites (Central Mongolia), the mechanisms of their formation were revealed. Primary melt inclusions and crystalline inclusions coexisting with them were studied in quartz in three samples of comendites selected in different parts of the volcanic section. Sanidin, zircon, and chevkinite were determined among crystalline inclusions. It was found that the crystallization of phenocrysts of comendites was carried out in the temperature range of 880–960 °C. It was determined that the glasses of homogeneous melt inclusions correspond to the compositions of trachydacites and rhyolites. They are also characterized by high concentrations of Zr, Nb, Rb, Y, Th and rare earth elements. At the same time, significant differences in the composition of melt inclusion glasses in the concentrations of Li and volatile components (H2O and F) were revealed. Some of the melts are enriched in these components, whereas other are depleted in them. Analysis of composition of glasses of homogenized melt inclusions in phenocrysts of alkaline salic rocks of bimodal association of Sant allowed to reveal magmatic processes responsible for the formation of comendite melts and leading to the accumulation of rare and rare earth elements in the latter. The dominant role among them is played by the process of magma crystallization differentiation accompanied by the process of liquid immiscibility with participation of fluoride melts.

UREILITIC DIAMONDS. A. A. Shiryaev1,2 , C. A. Lorenz3, I. I. Vlasov2, S. E. Borisovsky4, 1A. N. Frumkin Institute of physical chemistry and electrochemistry RAS, Moscow, Russia, a_shiryaev@mail.ru, 2Institute of general physics RAS, Moscow, Russia, 3Vernadsky Institute of Geochemistry and Analytical Chemistry, Kosygin St. 19, Moscow, 119991, Russia, 4Institute of geology of ore deposits, Petrography, Mineralogy, and Geochemistry RAS, Moscow, Russia

The mineral assemblages, mode of occurrence, and chemical compositions of coexisting fahlore and sphalerite from the Darasun gold deposit have been described. Three generations of fahlore and three generations of sphalerite have been recognized. The FeS content in sphalerite coexisting with fahlore ranges from 0.8 to 9.4 mol %. The complete solid solution series Fe-tetrahedrite–Zn-tetrahedrite–Fe-tennantite–Zn-tennantite reflected in Sb/(Sb + As) and Fe/(Fe + Zn) ratios ranging from 0 to 0.97 and from 0.07 to 1.00, respectively, with a predominant negative relationship between these ratios has been identified for the first time at the deposit. Stepped, oscillatory, and combined stepped-oscillatory growth zonings within fahlore grains and heterogeneous aggregates of fahlore have been found. Fahlore is enriched in As with respect to Sb, and Zn-tetrahedrite is followed by Fe- and Zn-tennantite from early to late generation; Zn-tetrahedrite is followed by Fe-tennantite in zoned grains and overgrown rims; sphalerite crystallized at decreased temperature and sulfur fugacity. The evolution of the chemical composition of fahlores was caused by the evolving temperature, fluid salinity, and conditions of metal migration.

This article presents the new mineralogical, fluid inclusion, and isotopic data for ores of the Novoshirokinsky base metal–gold deposit. Mineralogical sequence is supplemented and specified. The mineral assemblages containing native gold are studied. Morphology, grain size and chemical composition of native gold are described. Major parameters and composition of mineralizing fluids of the main ore stages at the deposit are estimated: main base metal (mid-temperature conditions, fluid salinity 3.1–13.1 wt % equiv NaCl) and carbonate–base metal (low-temperature conditions, fluid salinity 1.0–12.9 wt % equiv. NaCl). Sulfur isotopic composition of sulfides from commercial mineral assemblages has been studied. The δ 34 S value (+10.5 ± 1‰) of mineralizing fluid has been calculated. The Novoshirokinsky deposit is similar to epithermal deposits and is spatially related to the Late Jurassic porphyry system. Evidence is provided on carbonate rocks of basement involved in the ore-forming process.

This study focuses on the morphological features, color cathodoluminescence, chemical composition, age, and source of zircons from the Ichet’yu occurrence. The isotopic U–Pb age of Paleo–Mezoproterozoic zircon grains varies within an interval of ~700 Ma from 2247 to 1478 Ma. The average roundness and well-preserved integrity of zircon grains allow us to suggest their proximal source. The available data show that the basement of the Middle Timan, composed of continental Paleo–Mezoproterozoic igneous rocks, is the most probable source of zircon in the Ichet’yu occurrence. These rocks are apparently a continuation of the Archean–Proterozoic Arkhangel’sk Mobile Belt.

Mineralogical and petrological-geochemical features of the Mesoproterozoic (1.23–1.20 Ga) alkaline ultrabasic rocks from the Kostomuksha-Taloveis (Russia) and Lentiira-Kuhmo (Finland) areas, West Karelia, have been studied. In terms of mineralogy and geochemistry, these rocks more resemble group II kimberlites of South Africa (orangeites) than olivine lamproites or ultramafic lamprophyres. On the basis of phenocryst composition, the studied orangeites are divided into three types: Cpx-Phl-Ol, Phl-Ol, and Phl-Carb orangeites. The Cpx-Phl-Ol orangeites from the Kostomuksha cluster clearly differ from analogous rocks from the Lentiira cluster. The composition of Phl-Ol orangeites is indicative of derivation by intense fractional crystallization; Cpx-Phl-Ol orangeites from the Kostomuksha area display evidence of intense lithosphere assimilation. The Phl-Carb orangeites from the Taloveis cluster and Cpx-Ol orangeites from the Lentiira cluster most closely approximate primary melts. The Kostomuksha orangeites are characterized by lowto moderate-radiogenic (87Sr/86Sr)1220 ratio varying from 0.7038 to 0.7067. The Phl-Carb orangeites of Taloveis have less radiogenic Nd isotope composition (ɛNd from −11 to −12) as compared to the Cpx-Phl-Ol and Phl-Ol orangeites of Kostomuksha (ɛNd from −6.9 to −9.4). The Cpx-Phl-Ol orangeites from Lentiira contain fresh olivine. By morphology and composition, there are three olivine generations: (1) large rounded, usually zoned crystals with Fo 92 core, 0.33–0.37 wt % NiO, and 0.03–0.04 wt% CaO, which are interpreted as xenocrysts from depleted peridotites; (2) anhedral rounded zoned olivines of intermediate size with Fo 82–83 cores, 0.03–0.05 wt % CaO, 0.12–0.17 wt % NiO, and up to 0.40 wt % MnO. These olivines were entrapped by orangeite melt and presumably represent a cumulate of basaltic melts or were derived from metasomatized peridotites; (3) fine euhedral olivines and xenocryst rims corresponding to Fo 88–89 with 0.10–0.42 wt % CaO, 0.14–0.35 wt % NiO, and up to 0.07–0.21 wt % MnO; their origin was presumably related to the crystallization from kimberlite melt. The calculation of \(f_{O_2 }\) of kimberlite melt during crystallization of perovskites using Nb-Fe perovskite oxyba-rometer showed that Cpx-Phl-Ol orangeites of Kostomuksha and orangeites of Lentiira crystallized at similar oxygen fugacities corresponding to ΔNNO from −3.3 to −1.1 and from −3.3 to −0.9, respectively. The Sm-Nd and Rb-Sr isotope study provided evidence for the contribution from ancient enriched source in the genesis of the orangeites. It was proposed that their mantle source was formed in two stages: (1) metasomatic reworking of previously depleted lithospheric source at the Karelian Craton base during Paleoproterozoic orogenic events 2.1–2.0 Ga ago; (2) extension-related generation of orangeite melts 1.27–1.20 Ga ago.