Group Minerals Research Articles

PLATINUM GROUP MINERALS OF THE BAIMKA GOLD PLACER CLUSTER, WESTERN CHUKOTKA: THE NEW DATA

The results of the study of the platinum group minerals of the Baimka gold placer cluster, Western Chukotka, Russia, are presented. Platinum group minerals belong to the iridium-platinum and platinum miner- alogical-geochemical types with the Late Jurassic cumulative pyroxenite-gabbro complexes as a probable source. Platinum group minerals came to alluvial gold placers primarily from intermediate reservoirs, which is the Volgian volcanic-sedimentary sequence. Rounded silicate glass inclusions are a specific feature of platinum minerals from the Baimka placer cluster.

A RELATIONSHIP BETWEEN CHLOROPHYLL AND DISSOLVED SUBSTANCES IN COASTAL WATERS OF SOUTH BALTIC SEA – ANTHROPOGENIC AND NATURAL INFLUENCES

The objectives of this study were to indicate the relationship between chlorophyll levels, dissolved metal group minerals and phosphates in the studied area of the Central Polish Coastal Waters and to relate these data to the influence of the terrestrial environment. In 2020, in the Central Polish Coastal Waters (PLB990002), which is a special area for the protection of birds, tests were carried out on the concentrations of chlorophyll, phosphates, dissolved microelements: zinc, cobalt, nickel and iron, and electrolytic conductivity. For the analysis of dissolved microelements, a graphite cuvette version of atomic absorption spectrophotometer (AAS-GF) was used. Chlorophyll and phosphates were studied using UV-VIS spectrophotometer. The concentrations obtained in coastal sea water in the spring after the wintering of waterfowl and in the autumn were compared. Microelement and phosphate concentrations were higher in spring than in autumn. The relationship between the level of chlorophyll and phosphates and the tested microelements in coastal waters was demonstrated, and the results were linked to the possible sources of these chemical substances, such as wintering of birds, tourism, municipal and port management. It was also observed that the upwelling effects occurred in the study area, which significantly influenced changes in the chemical composition of sea water.

Mckelveyite group minerals – Part 3: Bainbridgeite-(YCe), Na2Ba2YCe(CO3)6 ⋅ 3H2O, a new species from Mont Saint-Hilaire, Canada

Abstract. The new mckelveyite group mineral bainbridgeite-(YCe), ideally Na2Ba2YCe(CO3)6 ⋅ 3H2O, was found at Mont Saint-Hilaire, Quebec, Canada. Bainbridgeite-(YCe) occurs as pseudotrigonal and pseudohexagonal hemimorphic crystals that show platy, columnar, tabular, cone-shaped, barrel-shaped, saucer-shaped, or spindle-shaped habit. They often form stacked or parallel growth aggregates, rosettes, and groups of radiating crystals. The crystals are usually less than 1 mm in size. Bainbridgeite-(YCe) varies in colour from pale yellow to yellow, grey to almost black, bluish grey, green-grey, or white. The streak is white; the lustre is vitreous. The mineral has no cleavage. The Mohs hardness is 3. Dcalc is 3.49 g cm−3. Bainbridgeite-(YCe) is optically biaxial (+), α= 1.572(2), β= 1.586(2), γ= 1.628(2), 2 V (calc.) = 62∘, 2 V (meas.) = 45(4)∘(589 nm). The IR spectrum is reported. The composition (wt %, average of five analyses) is Na2O 6.86, CaO 0.59, SrO 4.01, BaO 25.71, Y2O3 8.24, La2O3 4.96, Ce2O3 8.38, Pr2O3 0.48, Nd2O3 1.87, Sm2O3 0.23, Gd2O3 0.67, Tb2O3 0.07, Dy2O3 1.38, Ho2O3 0.32, Er2O3 0.94, Tm2O3 0.08, Yb2O3 0.49, CO2 27.03, H2O 5.67, total 97.98. The empirical formula of the holotype calculated on the basis of six cations is as follows: Na2.11Ca0.10Sr0.37Ba1.60Y0.70La0.29Ce0.49Pr0.03Nd0.11Sm0.01Gd0.03Dy0.07Ho0.02Er0.05 Yb0.02(CO3)5.86(H2O)3.00. The mineral is triclinic, P1, a= 9.1079(2) Å, b= 9.1066(3) Å, c= 6.9332(2) Å, α= 102.861(2)∘, β= 116.148(2)∘, γ= 60.181(2)∘, V= 447.85(2) Å3, and Z= 1. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are 6.22(42)(001, 1‾1‾1, 1‾01), 4.430(100)(01‾1, 2‾1‾1, 120), 4.094(37)(1‾2‾1, 1‾11, 210, 111), 3.263(26)(11‾1, 2‾1‾2, 121), 2.888(67)(1‾2‾2, 1‾12, 211), 2.633(38)(3‾01, 030, 3‾3‾1), 2.263(23)(2‾21, 2‾4‾1, 4‾2‾1). 2.010(20)(03‾2, 3‾3‾3, 3‾03, 301, 032, 331). The crystal structure, solved and refined from single-crystal X-ray diffraction data (R1= 0.040), is of the weloganite type.

Exploring the staining potential of 1 GSK-3 inhibitors in bovine teeth: 2 a one-year laboratory investigation.

GSK-3 inhibitors, such as Tideglusib (TG) and CHIR-99021 (CHIR), show promise in stimulating reparative dentin formation. The aim of this study was to assess the discoloration potential of TG and CHIR in an established in vitro model. Enamel-dentin specimens made from bovine incisors were randomly allocated to five groups (n=15 each): group bovine blood (BB), group dimethyl sulfoxide (DMSO), group TG, group CHIR, and group mineral trioxide aggregate (MTA). Each specimen had a central cavity in which the respective material was applied and sealed with resin-based luting material. Color determination was conducted using a dental spectrophotometer at t0 (before filling), t1 (immediately after filling), t2 (after one week), t3 (after one month), t4 (after three months), t5 (after six months), and t6 (after one year). Statistical analysis involved descriptive statistics, Kruskal-Wallis tests, and analysis of variance (α=0.05). Group BB and group CHIR exhibited the most significant decrease in lightness (ΔL*) after one year (ΔL*-4.7 and ΔL* -5.7, respectively), whereas groups DMSO, TG, and MTA showed minimal changes (DMSO ΔL*: -0.3; TG ΔL*: 1.4; MTA ΔL*: -0.5). Group BB and CHIR exhibited the highest ΔE values (6.4Å}0.6 and 6.5Å}0.8, respectively). Unlike CHIR, TG did not result in discoloration exceeding the threshold of visual perception, defined by a ΔE value of 5.5, during the one-year observation period. This laboratory study therefore suggests that TG could be utilized for indirect or direct pulp capping without major discoloration concerns. However, additional research is required to corroborate these findings.

The primary geology of the Paleoproterozoic Mt Weld Carbonatite Complex, Western Australia

Abstract The paleoregolith overlying the c. 2.06 Ga Mt Weld carbonatite (eastern Yilgarn Craton, Western Australia) hosts one of the largest Rare Earth Element (REE) deposits globally. Historic exploration and research has focussed on this weathered material, with a lack of unweathered samples preventing a thorough investigation into the nature of the underlying carbonatite. Recent deep drilling has allowed this first in-depth study into the primary geology, mineralogy and geochemistry of the carbonatite complex. Mt Weld shares a similar lithological architecture to other global carbonatite complexes, such as Ngualla (Tanzania, Bonga (Angola), Chilwa Island (Malawi) and Mirima Hill (Malawi), displaying a central (~600 m diameter) unit of magnesio- to ferrocarbonatite is surrounded by a broad (~1.2 km) annulus of calciocarbonatite, itself surrounded by a fenitic halo. Primary REE mineralisation occurs within the central magnesio- to ferrocarbonatites (~2% Total Rare Earth Oxides in bulk rock) and is dominated by fine-grained monazite hosted within fractures and voids, as well as late magmatic synchysite/bastnäsite. Both high and low phosphourous ferrocarbonatites occur within this central magnesio- to ferrocarbonatite unit that display (respectively) monazite or synchysite/bastnäsite mineralisation with textural evidence for these REE-bearing carbonates occasionally forming as polycrystalline pseudomorphs of earlier burbankite group minerals. Magnesio- to ferrocarbonatite dykes with zhonghuacerite/olekminskite/ancylite assemblages occur throughout the otherwise REE-poor calciocarbonatites (~0.2% Total Rare Earth Oxides in bulk rock). Late hydrothermal events strongly influenced the modern-day mineral assemblages with much of the existing ore mineral textures interpreted as hydrothermal reworkings of pre-existing REE-bearing minerals. A comparison of the fresh carbonatite and the paleoregolith geochemistry suggests minimal horizontal migration of ore elements during paleoregolith formation, with the overlying paleoregolith material broadly reflecting the underlying carbonatite trace and minor element signatures. This allows the inference of an approximately 5× upgrade in REE (and Nb) concentrations from the primary carbonatite to the overlying paleoregolith. Mt Weld shows distinct geological, mineralogical and isotopic differences to other currently mined carbonatite-associated REE deposits, such as Bayan Obo (China), Mountain Pass (USA) and the Mianning-Dechang belt (China), which suggests that fundamentally different carbonatite mantle sources and evolutionary paths can form world-class REE ore bodies.

Supergene mineral assemblage from sediments affected by contact and hydrothermal metamorphism, locality Dobrá – Staré Město near Frýdek-Místek (Czech Republic)

At locality Dobrá – Staré Město, series of outcrops occur on both banks of the Morávka River. The river cuts through the sediments on the tectonic contact between the Silesian and Subsilesian units of the Outer Western Carpathians. Clayey facies of the Hradiště Formation (Early Cretaceous, Valanginian to Aptian) contains numerous tectonic fragments reaching hundreds meters in size of strongly altered (carbonatized, smectitized) subaquatic volcanic rocks of the Teschenite Association. These volcanic rocks are dominated by fine-grained to aphanitic rocks, possibly of both effusive and intrusive origin. The host sediments affected by the contact metamorphism (contact adinole) also occur. Framboidal pyrite is abundant in majority of sediments of the studied area, giving rise to efflorescences of gypsum, baryte, celestine, and a mineral of alunite group (Figure 1). A more varied assemblage of supergene minerals was recognized on a small rock outcrop at GPS coordinates N 49° 39.992’ E 018° 23.810’ (Figure 2), where it developed relatively recently after the big floods in 2010 that washed away the previous mineralization. During the first years, only gypsum crusts were detectable, while in 2023, we recognized 4 macroscopic and 5 microscopic minerals forming thin botryoidal crusts. These crusts show faint zoning, with gooey, gel-like X-ray amorphous material in the humid upper part , middle zone with abundant fibroferrite and the lower part dominated by gypsum. Gypsum forms well-developed, but frequently corroded crystals with various habitus (Figure 4A, B). Fibroferrite is present as fibrous aggregates with individual crystals of up to ca. 100–150 µm long and <1 µm thick (Figure 4C). It forms directly from the gel-like substance (Figure 4D). Rhombohedral crystals and rossete aggregates of hydroniumjarosite vary from 2 µm to 5 µm in size (Figure 4E), but the most common are dust-like coatings on rock fissures with particle size <1 µm. Rusty coatings of schwertmannite (Figure 4F), in some places accompanied by gypsum, with Fe/S at. % ratios near 4–5 are common. In some cases, the Al/Fe at. % ratio exceed 1, which might indicate presence of yet undescribed Al-analogue of schwertmannite, ill-defined alumogel, or an amorphous precursor of aluminite. Presence of ferrihydrite is possible but not confirmed. The above-mentioned Fe-rich phases are frequently accompanied by diplobacilli-shaped bacteria (Figure 4F). Slavíkite, pickeringite-halotrichite, alunogen, copiapite group mineral, hexahydrite, and melanterite (Figure 5) were also recognized by EDS and PXRD. Slavíkite and copiapite group minerals seem to be alteration products of fibroferrite. Unit-cell parameters refined from the X-ray powder diffraction are presented for all recognized phases (Table 1). Surprisingly, secondary sulfates are present on the metasediments with abundant calcite (Figure 3), which should serve as a neutralization buffer. The reason is the restricted amount of calcite available on the rock fissure surfaces, and water infiltration partially blocked by newly-formed gypsum. The albite in contact adinole (Figure 3) is unaffected by the acid rock drainage, since Na ions are not present in significant quantities in supergene phases. Since there is still enough available unaltered pyrite, we expect a shift towards more stable mineral assemblage in future. The limited amount of secondary sulfates does not present any significant harm to the environment.

Plumboperloffite, PbMn2+2Fe3+2(PO4)3(OH)3, a new member of the bjarebyite group from Wiperaminga Hill, South Australia, Australia

AbstractPlumboperloffite, PbMn2+2Fe3+2(PO4)3(OH)3, is a new mineral and member of the bjarebyite group from Wiperaminga Hill West Quarry, Boolcoomatta Reserve, Olary Province, South Australia, Australia. The mineral was found in a single cavity in triplite–barbosalite matrix associated with fluorapatite, phosphosiderite, natrodufrénite and fluorite. The mineral forms intergrowths of subparallel, thin tabular to bladed crystals. Individual crystals are up to 40 μm in length. Plumboperloffite is brownish orange in colour with a vitreous lustre. The mineral has brittle tenacity, an excellent cleavage on {100} and uneven fracture. The calculated density is 4.416 g/cm3. Plumboperloffite is biaxial (+), α = 1.87(1), β = 1.88(1) and γ = 1.89(1) as measured in white light. The measured 2V is 88(1)°. Dispersion is apparently strong, based on extinction colours and the orientation is Y = b. The pleochroism in shades of yellow brown is X < Z < Y. Electron microprobe analysis gave the empirical formula (based on 15 O apfu) (Pb0.92Ca0.04Ba0.01K0.01)Σ0.98(Mn2+1.84Fe2+0.13)Σ1.97(Fe3+1.97Al0.03)Σ2.00(P3.01O11.94)(OH)Σ3.06. Plumboperloffite is monoclinic, space group P21/m with a = 9.1765(18), b = 12.340(3), c = 5.0092(10) Å, β = 101.01(3)°, V = 556.8(2) Å3 and Z = 2. The crystal structure has been refined using X-ray single-crystal data to a final R1 = 0.0207 on the basis of 1417 reflections with Fo > 4σ(Fo). The mineral is isostructural with members of the bjarebyite-group minerals.

Ab-initio calculations of structural, vibrational, electronic and elastic properties of fluorite minerals: A computer simulation approach

There are numerous industrial and technological uses for minerals from the fluorite group. Fluorite group minerals, according to Dana's mineralogy, are simple metallic fluorides with a cubic crystal structure that belongs to the space group Fm-3m (225). Fluorite, Stronitiofluorite, Frankdicksonite, and Fluorocronite are the members of fluorite group minerals. These are F-centered cubic minerals, also known as halides, having general formula MF2, where M = Ca, Sr, Ba, and Pb. These minerals have cubic (Fm-3m), orthorhombic (Pnma), and hexagonal (P63/mmc) phases at different pressure. In the present study, the structural optimization of CaF2, SrF2, BaF2, and PbF2 with cubic (Fm-3m) phase has been performed by Density Functional Theory (DFT) calculation using Generalized Gradient Approximation (GGA) with Quantum Espresso code. The electronic band structure of fluorite group minerals has been investigated. From the electronic band structure, it has been found that these minerals are insulator having indirect band gap. Phonon dispersion curves for CaF2, SrF2, BaF2, and PbF2 confirms that fluorite minerals in cubic phase are mechanically stable. LO–TO splitting in the phonon dispersion curves indicates that these mineral have ionic bonding. Also, lattice parameter, elastic constants, bulk modulus, Young's modulus, shear modulus, Poisson's ratio, Pugh's ratio and Cauchy pressure for fluorite minerals have been calculated using Voigt–Reuss–Hill approximation, and the results have been analyzed with experimental data.

Mineralogy and Petrology of Carbonatites and Fenites from Khlibodarivka Occurrence

The data of mineralogical studies of carbonatite veins and exocontact fenites in the open pit near the Khlibodarivka occurrence (Donetsk region, Volnovaha district) are presented. The thickness of carbonatite veins is neglegible, rarely exceeding 30 cm, and are mainly composed of calcite, alkaline amphibole and albite are the most common silicate minerals. Accessory minerals are more often represented by monazite, apatite, columbite, minerals of pyrochlore group, zircon, and opaque (ilmenite, rutile, magnetite, sulfides). In addition to the above-mentioned minerals, except for the minerals of pyrochlore group, chlorannite, aegyrine, REE-carbonates, baryte, allanite-(Ce), REE-apatite were found in the fenite haloes and veinlets. The reactionary interaction of the carbonatite melt enriched in alkalis and volatiles with the hosted enderbites caused the appearance of fenite halos both around the veins of carbonatites and the thin "net" of veinlets without a visible connection with carbonatites. The significant thickness of the fenite halos (usually twice as much in comparison to the thickness of the carbonatite veins), albitization of the surrounding rocks and saturation of the alkaline femic minerals of the carbonatite veins and fenites indicate that the initial carbonatite melt contained a significant amount of Na and volatile components (H2O, F, CO2, possibly Cl), and also had a more ferruginous composition of carbonates due to the presence of siderite or ankerite components (in the melt). As a result of the dissociation of primary carbonates, iron, as well as alkalis, was concentrated in the fluid phase and subsequently included in aegirine and alkaline amphiboles. The fenitization of host rocks took place in several stages. At the initial stage, the alkali-enriched fluids, mainly Na, F, and possibly Cl, were separated, while the later ones fluids were Fe-enriched and existing in more oxidized conditions. The fluids genetically related to carbonatites were penetrating into the host rocks caused the redistribution of trace elements. Barium, Th, and partly LREE were carried out from carbonatites most intensively, while Sr, Nb and a significant part of REE remained immobile due to the early crystallization of their host minerals and lack of subsequent autometasomatic alteration. Geochemistry of carbonatite veins (high content of incompatible elements such as Sr (11 7777 ppm), increased REE (1624 ppm), elevated Nb, chondrite-normalized pattern of REE, high (La/Yb)cn = 24.7 and absence of negative Eu anomaly (Eu* = 1.03) and endogenous ratios of isotopes of Sr (0.703), C and, partially, O) testify to their magmatic origin. It is possible that the insignificant thickness of the carbonatite veins and the intensive interaction of juvenile fluids with the host granitoids and meteoric fluids caused the enrichment of carbonatites with 18O (δ18O 8.4÷20), but with the preservation of primary δ13C (–8 ÷ –6.5). Currently, the increased concentrations of rare metals were not found in carbonatites of the Khlibodarivka village. However, the presence of carbonatite veins in association with fenite halo, spatial connection to the Oktyabrsky massif of alkaline rocks, as well as numerous fenite occurrences in this area, increase the prospects of this area for such mineralization.

A snapshot of a representative Brazilian state of illegal mining in indigenous areas during the era of malaria elimination.

Malaria is a public health problem and the cases diagnosed in the capital of Roraima, Brazil, show potential to characterize the burden of the disease in the state. This study aimed to describe the epidemiological, clinical, and laboratory aspects of malaria cases diagnosed in Boa Vista. For this purpose, a descriptive, cross-sectional study was conducted in two health units in the city, with individuals diagnosed and who agreed to respond the questionnaire. Of the total of 206 participants, characterized as men, mixed-race, and young, 96% (198) reported participating in illegal mining activity. Among the group of miners, 66% (131) came from other states of Brazil or other countries. The mines were mainly located in the Yanomami territory in Roraima. Plasmodium vivax infection occurred in 74% (153) of participants. In the miner's group, hospitalizations for severe malaria, previous malaria attacks, and delays in treatment after the onset of symptoms were reported. Although 73% (145) of miners reported knowing how malaria was transmitted, only 54% (107) used mosquito nets or repellents. The use of Artecom and chloroquine by miners is not for the complete treatment but only to relieve symptoms for returning to gold mines, highlighting the importance of molecular surveillance to antimalarial resistance. Indigenous peoples are considered vulnerable to malaria and miners promotes the increase of malaria in Roraima Indigenous Lands. Therefore, access to diagnosis and treatment in Indigenous areas invaded by miners is imperative to confront this disease that ravages Indigenous communities and threatens public health on a large scale to achieve the goal of eliminating malaria in the state.

Does defect configuration affect the outcomes of alveolar ridge preservation? An experimental in vivo study.

The purpose of this study was to compare the bone healing potential of 1-, 2-, and 3-wall defects following alveolar ridge preservation (ARP) treatment, as well as to evaluate the efficacy of ARP as a treatment option for destructive sites. Three groups, characterized by 1-, 2-, and 3-wall defects, were randomly assigned to the maxillary second, third, and fourth premolars in each of 8 beagle dogs. Each defect was created at either the mesial or distal root site of the tooth, which was hemi-sectioned and extracted. The contralateral root was preserved to superimpose with the experimental site for histomorphometric analysis. For each site, either spontaneous healing (SH; control) or ARP (test intervention) was randomly applied. Each group was divided in half and underwent a healing period of either 4 or 12 weeks. The Mann-Whitney U test and Kruskal-Wallis test were used for histomorphometric analyses. Statistical significance was set at P<0.05. Qualitative analysis revealed a higher percentage of new bone in the apical area compared to the coronal area, regardless of defect type and healing period. In quantitative analysis, the 3-wall defect exhibited a significantly higher percentage of mineralization in the ARP group after 12 weeks of healing (ARP: 61.73%±7.52%; SH: 48.84%±3.06%; P=0.029). An increased percentage of mineralization was observed with a greater number of remaining bony walls, although this finding did not reach statistical significance. Within the limitations of this study, ARP treatment for compromised sockets appears to yield a higher percentage of mineralization compared to SH. Although the effectiveness of the remaining bony walls was limited, their presence appeared to improve the percentage of mineralization in ARP treatment.

Migration paths of the Na+-ion diffusion for minerals of the lovozerite group: crystallochemical and DFT modeling

For 11 minerals of the lovozerite group, theoretical investigations of Na+-ion migration were performed.

Influence of the rat diet enrichment with oat β-gucans on the assimilation of B group vitamins, mineral elements and lipid metabolism

Despite the widespread use of oat β-glucans as ingredient of foods and dietary supplements, there is insufficient data on their effect on the metabolism of vitamins and minerals. The purpose of the study was to evaluate the effect of including oat bran with a high content of β-glucans (β-glucan) in the diet on the absorption of micronutrients and lipid metabolism in growing rats deficient in vitamins D, group B and trace elements (iron, copper, zinc). Material and methods. After the development of micronutrient deficiency (for 23 days), in order to assess the effect of oat bran (5%) with a high content of β-glucans on the correction of the micronutrient status of growing male Wistar rats (with initial body weight of 70.7±0.7 g), the missing micronutrients were introduced in the semi-synthetic diet deficient in vitamins D, group B, iron, copper and zinc within 7 days either along with β-glucan (1.47%) or without its addition. Indicators of micronutrient sufficiency (riboflavin serum concentration, daily urinary excretion of thiamine, riboflavin and 4-pyridoxic acid, measured by fluorometric methods; serum concentration and urinary excretion of calcium, magnesium, iron, zinc, copper, phosphorus, measured by the atomic absorption method or using standard methods on a biochemical analyzer) and the biochemical parameters of blood serum were compared with the parameters of rats adequately provided with all micronutrients throughout the experiment. Results. Replenishment of missing micronutrients in the diet of rats with deficiency in vitamins D and group B, iron, copper and zinc for 7 days led to the elimination of deficiency of vitamins B1, B2 and B6, regardless of the presence of β-glucans in the diet. At the same time, against the background of the presence of β-glucans in the feed, an increase in the absorption of iron was observed, as evidenced by an increase by 1.73 times in iron blood plasma level (р<0.05) and a tendency towards its urinary excretion decrease by 1.60 fold (р<0.10) compared to animals from the control group. Adding oat bran with β-glucans to the feed did not lead to a decrease in blood plasma level of total cholesterol and low-density lipoproteins cholesterol. The levels of high-density lipoprotein cholesterol and triglycerides in rats of all three groups did not have statistically significant differences. Conclusion. The presence of β-glucans in the diet had virtually no effect on the absorption of B vitamins and improved the absorption of iron.

Mineralogical and geochemical features of heavy concentrates from creeks of the North-Western end of the Оkhotsk terrane (Khabarovsk Krai)

The work presents the mineralogical and geochemical features of heavy concentrates from eight gold-bearing tributaries of the Anmandykan 2nd Creek in Khabarovsk krai: West otvilok, East otvilok, Somnitelny, Smezhny, Perevalny, Sobol, Vstrechny and Khvory. The mineral composition of heavy concen-trates of the right creeks differs from those of the left ones by a signifcantly higher percentage of minerals of the garnet group, sulfdes and native gold and a lower content of zircon and amphiboles. Garnets in heavy concentrates have different compositions and belong to the almandine and grossular-andradite series. Native gold grains in placers are yellow, small, mostly weak and medium-rounded, often with inclusions of quartz, feldspar, pyrite, iron oxides and hydroxides, and zircon. The native gold grains have low fneness and contain only Ag. The native gold grains are rimmed by thin, intermittent, porous aggregates of high-fneness gold. Two gold placer mineral assemblages are identifed, which include native gold, chalcopyrite, sphalerite and pyrite in assemblage 1 and native gold, scheelite and minerals of the garnet group (mainly of the grossular-andradite composition) in assemblage 2. Our data allow the forecast of the presence of two primary gold sources of gold-quartz-sulfde and skarn types. The comparison of results of mineralogical and geochemical studies showed their suitability and expressiveness for the interpretation of geological and metallogenic features of the studied area.

U–Pb Dating, Gemology, and Chemical Composition of Apatite from Dara-e-Pech, Afghanistan

Minerals of the apatite group commonly occur in granite pegmatites, and their ability to incorporate a wide range of trace elements makes them a good indicator of magma composition and magmatic–hydrothermal processes. Gem-quality purple apatite crystals from the Dara-e-Pech pegmatite field in Afghanistan have rarely been reported. Here, we investigated apatite crystals originated from this locality, using gemological testing, chemical analysis, and in situ U–Pb dating, with the purpose of identifying their origin, the constraints on the magma source in which the apatite crystals were formed, and the timing of the magmatic–hydrothermal activity. Our findings demonstrate that the purple apatite crystals were impure fluorapatite, characterized by heavy rare-earth element (HREE) enrichment, intermediate Eu anomalies, and non-CHARAC Y/Ho ratios. The results showed that these apatite crystals yielded a lower intercept age of 135.8 ± 6.9 Ma. We proposed that the pegmatitic apatite samples formed in a transitional magmatic–hydrothermal pegmatitic system with moderate fO2 in the Early Cretaceous (~135 Ma). Our study helps to constrain the magmatic–hydrothermal activities of the little-known Dara-e-Pech pegmatite field.

Nb-Ta-Sn Oxides from Lithium-Beryllium-Tantalum Pegmatite Deposits of the Kolmozero–Voronja Belt, NW Russia: Implications for Tracing Ore-Forming Processes and Mineralization Signatures

In this paper we present textural and compositional data for columbite group minerals (CGMs) and associated Nb-Ta-Sn oxides from lithium-beryllium-tantalum pegmatite deposits of the Kolmozero–Voronja belt, NW Russia, with the aim of deciphering these characteristics for minerals from deposits with different mineral signatures and lithium ore grade. Minerals from four deposits, including two of world-class (Kolmozero and Polmostundra), are examined. The main controlling factors for CGM compositional ranges are the diversity and rate of magmatic fractionation, hydrothermal overprint and mineral paragenesis, following the specific geochemical signature of the different pegmatite deposits. CGM from Kolmozero include several mineral species (columbite-(Fe), columbite-(Mn), tantalite-(Fe), and tantalite-(Mn)), showing large compositional variations, mainly controlled by Nb-Ta fractionation (Ta/(Ta + Nb) = 0.16–0.70; Mn/(Mn + Fe) = 0.45–0.63). Textural patterns are various (oscillatory, homogeneous, and patchy); spongy domains and overgrowing Ta-rich rims are also observed somewhere. This indicates the involvement of numerous magmatic and hydrothermal processes. The Polmostundra CGMs are represented by columbite-(Fe) with Ta/(Ta + Nb), ranging from 0.05 to 0.39; some crystals are homogenous, and others present normal, oscillatory, mottled and reverse-zoning patterns. The Okhmylk CGMs are irregular normal, patchy and homogeneous columbite-(Fe) and columbite-(Mn), with Ta/(Ta + Nb) = 0.09–0.24 and Mn/(Mn + Fe) = 0.29–0.92, indicating the suppressed magmatic fractionation and iron drop due to precipitation of Fe minerals. Columbite-(Fe) and columbite-(Mn) from the Be-Ta Shongui deposit are less evolved, with Ta/(Ta + Nb) = 0.07–0.23 and Mn/(Mn + Fe) = 0.31–0.55. The minerals are characterized by progressive normal, oscillatory, homogeneous and irregular reverse patterns. Associated pyrochlore minerals occur both as early magmatic (Kolmozero) and late hydrothermal (Polmostundra, Okhmylk). Cassiterite is found only in the Okhmylk dykes, and is apparently of hydrothermal origin. CGM from Li pegmatites have impurities of Ti (0.01–0.05 apfu) and W (up to 0.02 apfu), whereas CGM from Be pegmatites contains elevated Ti (up to 0.09 apfu). The mineral system analysis presented here is relevant for exploration.

The surface characteristics of natural heulandites/clinoptilolites with different extra-framework cations

Abstract Natural tuff samples in western Anatolia (Türkiye) originating from Miocene rhyolitic–pyroclastic rocks with &gt;80 wt.% heulandite/clinoptilolite zeolites were investigated for their surface characteristics determined according to nitrogen adsorption after degassing at 150°C (specific surface area, pore volume and pore diameter). Additionally, these surface characteristics were correlated with the cationic compositions of the heulandite/clinoptilolite group minerals. The examined samples were characterized by two main pore diameters that were not related to specific surface area and pore volume but were partially related to the types and occupancy of extra-framework cations. One set of samples has a pore diameter of ~24 Å, total cation content (Na + K + Ca + Mg) ranging from 3.46 to 4.40 and a (Na + K)/(Ca + Mg) ratio ranging from 0.34 to 0.92. The total cation contents and (Na + K)/(Ca + Mg) ratios of the remaining samples with a pore diameter of ~37 Å are 4.30–5.08 and 1.48–2.85, respectively. After degassing at 300°C, there is a slight difference in the pore diameters of these two sets of samples (~37 and 38 Å). The pore sizes of the samples with a (Na + K)/(Ca + Mg) ratio &lt; 1 (heulandite composition) increased from 24 to 36–38 Å with increasing degassing temperature, whereas the pore sizes of the samples with a (Na + K)/(Ca + Mg) ratio &gt; 1 (clinoptilolite composition) increased from 37 to only 38–39 Å. However, there is no correlation between the Si/Al ratios and the cation-exchange capacities of the samples and their surface characteristics obtained by degassing at the two temperatures.

Applied geochemistry for the discrimination between mafic and ultramafic rocks in Cu-Ni-PGE-bearing layered complexes: A case study at the la Jovita-Las Águilas belt, Sierra Grande de San Luis, Argentina

The Virorco intrusive body is comprised in La Jovita-Las Águilas mafic-ultramafic belt, Sierra Grande de San Luis, Argentina. The ultramafic rocks of this belt carry a base metal sulphide mineralization and platinum group minerals. Macroscopic description of mafic and ultramafic rocks, done by the mining exploration companies, can not differentiate the mineral percentages. Therefore, considering the geochemical composition of the already classified mafic-ultramafic rocks of surface samples from the mentioned belt, we established compositional ranges of geochemical parameters (MgO, Al2O3, Na2O, Sr and Cr) for both mafic and ultramafic rocks. Linking the geochemical data of drill cores made by Castillian Resources Corp. company over the Virorco body, with the mentioned ranges, it was possible to discriminate between mafic and ultramafic rocks present in such drill cores. This provides a useful prospecting tool to identify the mafic and ultramafic units that carry the mineralization and to correlate mineralized units from the different drill cores. This method can be applied, not only on the bodies of the mentioned belt, but in other similar deposits elsewhere. The methodology proposed in the present contribution was validated by the Machine Learning algorithm Random Forrest with a 91% success rate.

Short-wavelength infrared characteristics and composition of white mica in the Demingding porphyry Cu-Mo deposit, Gangdese belt, Tibet: Implications for mineral exploration

The Demingding Cu–Mo deposit, found in the eastern Gangdese metallogenic belt in China, has a significant exploration potential. Detailed field studies coupled with short-wavelength infrared (SWIR) spectroscopy and electron probe micro analyses (EPMA) identified a total of 15 alteration minerals such as white mica group minerals, chlorite, kandite, and smectite groups. The study also discovered the spatial distribution of alteration zone patterns, including phyllic, propylitic, and intermediate argillic alterations. Furthermore, variations were observed in the Al-OH absorption position (Pos2200) of the white mica group with variable Al-Si-Fe-Mg content. Most of the white micas in the ore zone were muscovitic series, whereas the barren zone contained phengitic series micas. Some micas have undergone a transition to illite due to low-temperature alteration overprinting. The western part of the deposit exhibited lower Pos2200, higher SWIR-IC, and higher Dep2200 values, implying an intense phyllic alteration and higher paleotemperatures. These characteristics suggest that the area is in close proximity to the hydrothermal center and fluid channel. Therefore, it was identified as an exploratory target for buried copper ore bodies. The SWIR spectra of the white mica group can be used for exploration in other similar porphyry deposits. Under acidic conditions, shorter Pos2200 and higher SWIR-IC can be used as indicators for hydrothermal or mineralization centers.

Planerite with aheylite and faustite from the Chala deposit, Spahievo Ore Field

Planerite, aheylite and faustite are minerals of the turquoise group. They were found in samples from the Chala deposit, Spahievo Ore Field. The samples consist of a small crystalline mass of the investigated mineral phases among quartz. Single spherulites up to 2 mm in size and aggregates of spherulites with a yellowish-greenish color are observed in small cavities. Transparent, colorless wavellite crystals and aggregates are crystallized on spherulites. For the first time in Bulgaria, the presence of aheylite was established.