Search Results (253)

The Eastern Kazakhstan Gold Belt is a major black-shale-hosted gold province in Central Asia where the main types of deposits comprise mineralized zones with auriferous sulfides (micro- and nano-inclusions of gold and refractory gold) and quartz veins with visible gold. The quartz vein deposits are economically less important but may potentially represent the upper parts of bigger ore systems concealed at depth. In this work, the mineralogy of the quartz vein deposits and related wall rock alteration zones was studied using microscopy and SEM-EDS analysis, and the geochemical dispersion of the ore elements in primary alteration haloes was documented utilizing spatial distribution maps and statistical treatment methods. The studied auriferous quartz veins are classified as epizonal black-shale-hosted orogenic gold deposits. The veins generally have linear shapes with an average width of ca. 1 m and length up to 150 m and contain high-grade native gold with minor amounts of sulfides. In supergene oxidation zones, the native gold is closely associated with Fe-hydroxide minerals cementing brecciated zones within the veins. The auriferous quartz veins are usually enclosed by the wall rock alteration envelopes, where two types of alteration are distinguished. Proximal phyllic alteration (sericite-albite-pyrite ± chlorite, Fe-Mg-Ca carbonates, arsenopyrite, and pyrrhotite) develops as localized alteration envelopes, and pervasive carbonation accompanied by chlorite ± sericite and albite is the dominant process in the distal alteration zones. The rocks within the alteration zones are enriched in Au and chalcophile elements, and three groups of chemical elements showing significant positive mutual correlation have been identified: (1) an early geochemical assemblage includes V, P, and Co (±Ni), which are the chemical elements characteristic for black shale formations, (2) association of Au, As, and other chalcophile elements is distinctly overprinting, and manifests the main stage of sulfide-hosted Au mineralization, and (3) association of Bi and Hg (±Sb and U) includes the chemical elements that are mobile at low temperatures, and can be explained by activity of the late-stage hydrothermal or supergene fluids. The chalcophile elements show negative slopes from proximal to distal alteration zones and form overlapping positive anomalies on spatial distribution mono-elemental maps. Thus, the geochemical methods can provide useful tools to delineate the ore elemental associations and to outline reproducible anomalies for subsequent regional gold prospecting. Full article

Due to the rapid advancement of technology, lithium carbonate has become a crucial raw material for battery storage applications. Brines remain the primary source, while lithium carbonate production from ores is limited. Therefore, expanding resources, identifying potential deposits, and characterizing existing sources are essential. Direct lithium detection via MLA is challenging due to its atomic number being below 6; however, it can be indirectly identified through lithium-bearing biotite. This study characterizes lithium-bearing biotite in nepheline syenite ore, considering biotite as the primary lithium source. Analytical methods included MLA, modal mineralogy, XRD, ICP-OES, XRF, SEM-BSE, and EDS. The ore contained 4% biotite, with a liberation degree exceeding 70% in particles finer than 500 µm. Biotite formed binary, ternary, and complex associations with K-feldspar, nepheline, and albite. Finer particle sizes increased biotite liberation while reducing associations; no binary biotite–nepheline associations were detected below 75 µm. EDS spectra confirmed biotite as the sole lithium-bearing mineral. Full article

Zircon is one of the most common accessory minerals in all types of granitoids. Due to its resistance to secondary processes, it preserves information about the composition of magma and conditions at the time of crystallization. Madeira albite granite, Brazil, offers optimum conditions for the study of chemistry and shape of zircon and the relation between the contents of particular trace elements in magma vs. in crystallizing zircon. Textural and chemical zircon data obtained using scanning electron microscopy (BSE) and cathodoluminescence (CL) imaging, automated mineralogy by TESCAN Integrated Mineral Analyzer (TIMA), and electron probe microanalyses (EPMA) enabled us to define four albite granite facies containing zircons of specific structures and chemistry. Zircon in the Madeira albite granite was formed during several, largely temporally and spatially independent episodes. During the crystallization of the common facies, occupying most of the intrusion volume, Zr/Hf value in zircon decreased from 40 to 20. This zircon, in some episodes, incorporated a higher amount of Th, which was later unmixed in the form of thorite inclusions. The pegmatoidal facies, representing crystallization of residual magma, contains zircon without thorite inclusions with a Zr/Hf value from 35 to 5. The Th/U and Y/Yb values during this evolution scattered but generally evolved to Th, Yb-enriched compositions (Th/U up to >10, Y/Yb down to 0.1). The Li-poor facies, located in the center of the stock near the cryolite deposit, contains zircon with comparatively high Zr/Hf = 45–70 and higher U and Y contents. Later, part of the common facies was hydrothermally altered to border facies, but zircon did not change noticeably during this process. The contents of minor elements in all zircon varieties are generally low (U + Th + Y + REE ˂ 0.05 apfu); Y and REE are incorporated exclusively in the xenotime component. Many crystals have low analytical totals, down to 95 wt%, and are enriched in Al, Fe, Mn, Ca, and F but this process does not influence the primary Zr/Hf, Th/U, and Y/Yb ratios. Zircons from other Madeira granite facies, including the neighboring Europa pluton, differ mainly in much higher Y/Yb values and in having (Y + REE) >> P, indicating a different than xenotime substitution mechanism. Zircon from the Madeira albite granite differs from zircons from many metaluminous rare-metal granites in low contents of minor elements and a common assemblage with thorite, instead of forming Zrn–Thr–Xnt solid solutions. Full article

A 3D model integrating mineralogical, petrological, and geostatistical resource estimation was developed for Zone C of the Kofi Birimian gold deposit in Western Mali. Petrographic analysis identified two forms of gold mineralization: (i) native gold or electrum inclusions within pyrite, and (ii) disseminated native gold along pyrite fractures. Four types of hydrothermal alteration–epidotization, chloritization, carbonatization, and albitization were observed microscopically. Statistical analysis of geochemical data classified five lithologies: mafic dyke, felsic dyke, diabase, faulted breccia, and intermediate quartz diorite. Minerals identified petrographically were corroborated by multivariate correlations among elements (Cr, Fe, Ni, Al, Ti, Na, and Ca), as revealed by Principal Component Analysis (PCA). A 3D borehole-based model revealed spatial correlations between hydrothermal alteration zones and associated geochemical anomalies, notably tourmalinization (B) and albitization (Na), with the latter serving as a key indicator for new exploration targets. The spatial associations of anomalous Ag, B, Hg, As, and Na commonly linked to tourmalinization suggest favorable zones for gold and silver mineralization. Geostatistical analysis identified isotropic continuous mineralized structures for most elements, including gold. Spherical isotropic variograms with ranges from 35 to 75 m were fitted for in situ resource estimation (e.g., silver ≈ 40 m; gold ≈ 60 m). The resulting estimated resources (indicated + inferred), based on a 1.0 g/t Au cut-off, are 2.476 Mt at 3.5 g/t Au indicated (0.278 Moz or 8.67 t), and 1.254 Mt at 2.78 g/t Au inferred (0.112 Moz or 3.49 t). This study provides a framework for identifying new mineralized zones, and the multidisciplinary approach demonstrates the connections between mineralogy and the information embedded in geochemical datasets, which are revealed through appropriate tools and an understanding of the underlying processes. Full article

An advanced alkali-acid (NaOH-HCl) chemical method was used to deash aluminum-rich coals (ARCs) with a high ash content of 27.47 wt% to achieve a low ash content of 0.46 wt%. In the deashing process, aluminum in the coal ashes was dissolved in both alkali solutions and acid solutions. The deashing alkali solutions with dissolved coal ashes were regenerated by adding CaO, and the resulting precipitates were added with sodium bicarbonate for aluminum extraction. High temperatures increased aluminum extraction, and excessive sodium bicarbonate addition decreased aluminum extraction. The deashing acid solutions were concentrated by evaporation, and silica gels formed during the process. The obtained mixtures were calcinated at 350 °C for the decomposition of aluminum chlorides, and soaked with water at 60 °C to remove the soluble chlorides. For the insoluble oxides after soaking, diluted alkali solutions were used to extract the aluminum at 90 °C, and aluminum extraction failed due to the formation of albite in the presence of sodium, aluminum and silicon elements as proved by XRD and SEM/EDS. When silica gels were separated by pressure filtering, aluminum extraction greatly increased. Aluminum extractions were accordingly made in the form of sodium aluminate from the deashing solutions of coals, which could be advantageous for sandy alumina production. Full article

Barite, a mineral composed of barium sulphate, holds global significance due to its wide range of industrial applications. It plays a crucial role as a weighting agent in drilling fluids for the oil and gas industry, in radiation shielding, and as a filler in paints and plastics. Although there are significant deposits of the mineral in commercial quantities in Nigeria, the use of barite of Nigerian origin has been low in the industry due to challenges that require further research and development. This research employed nanoindentation experiments using a model Ti950 Tribo indenter instrument equipped with a diamond Berkovich tip. Using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), we gained information about the structure and elements in the samples. The load–displacement curves were examined to determine the hardness and reduced elastic modulus of the barite samples. The SEM images showed that barite grains have a typical grainy shape, with clear splitting lines and sizes. XRD and EDX analysis confirmed that the main components are chlorite, albite, barium, and oxygen, along with small impurities like silicon and calcium from quartz and calcite. The average hardness of the IB3 and IB4 samples was 1.88 GPa and 1.18 GPa, respectively, meaning that the IB3 sample will need more energy to crush because its hardness is within the usual barite hardness range of 1.7 GPa to 2.0 GPa. The findings suggest further beneficiation processes to enhance the material’s suitability for drilling and other applications. Full article

Between approximately 725 and 518 Ma, a suite of specialized felsic plutons and granitic stocks were emplaced across the Arabian Shield, many of which are now recognized as highly mineralized prospects enriched in rare earth elements (REEs), rare metals, and radioactive elements bearing mineralizations. The current investigation focused on the radiological and geochemical characterization of naturally occurring radionuclides, specifically ²³⁸U, ²²⁶Ra, ²³²Th, and ⁴⁰K, within three strategically selected granitic prospects, namely, J. Tawlah albite granite (TW), J. Hamra (HM), and J. Abu Al Dod alkali feldspar syenite and granites (AD). Concerning the radioactivity levels of the investigated granitic stocks, specifically the activity concentrations of ²³⁸U, ²²⁶Ra, ²³²Th, and ⁴⁰K, the measured average values demonstrate significant variability across the TW, HM, and AD stocks. The average ²³⁸U concentrations are 195 (SD = 38.7), 88.66 (SD = 25.6), and 214.3 (SD = 140.8) Bq/kg for TW, HM, and AD granitic stocks, respectively. Corresponding ²²⁶Ra levels are recorded at 172.4 (SD = 34.6), 75.62 (SD = 25.9), and 198.4 (SD = 139.5) Bq/kg. For ²³²Th, the concentrations are markedly elevated in TW at 5453.8 (SD = 2182.9) Bq/kg, compared to 77.16 (SD = 27.02) and 160.2 (SD = 103.8) Bq/kg in HM and AD granitic stocks, respectively. Meanwhile, ⁴⁰K levels are reported at 1670 (SD = 535.9), 2846.2 (SD = 249.9), and 3225 (SD = 222.3) Bq/kg for TW, HM, and AD granitic plutons, respectively. Notably, these values exceed the global average background levels, indicating an anomalous enrichment of the studied granitic occurrences. The mean radiological hazard indices for each granitic unit generally exceed global benchmarks, except for AEDE_out in the HM and AD stocks, which remain below international limits. The geochemical disparities observed are indicative of post-magmatic alteration processes, as substantiated by the interpretation of remote sensing datasets. In light of the significant radiological burden presented by these granitic stocks, it is essential to implement a rigorous precautionary framework for any future mining. These materials must be categorically excluded from uses that entail direct human exposure, especially in residential construction or infrastructure projects. Full article

As one of the important lithium resource sources, lepidolite has become a new energy strategic resource research hot spot. The efficient flotation of lepidolite directly affects the recovery and economic value of lithium resources. This paper systematically reviews the flotation research progress of lepidolite, focusing on the influence of the type of capture agent and process parameters (pH, activator, and depressant) on flotation. In view of the separation problems caused by the similarity of the surface properties of lepidolite and its associated gangue minerals (albite, feldspar, and quartz), the strategies for regulating the crystal structure of the minerals and their surface properties are analyzed. In addition, the lepidolite flotation process and its challenges are summarized, including poor selectivity of chemicals, fine mineral embedded size, easy to form sludge, and insufficient environmental friendliness, etc. The future development direction of lepidolite flotation technology is also prospected, which provides theoretical support and reference for the efficient recovery of lepidolite. Full article

The rocks of the Burpala alkaline intrusion contain a wide range of rare minerals that concentrate rare earth elements (REEs), Nb, Th, Li, and other incompatible elements. One of the examples of the occurrence of such mineralization is albite–aegirine rocks located at the contact zone between the intrusion and the host terrigenous–sedimentary rock. In albite–aegirine rocks, cubic crystals of “metaloparite”, partially or completely substituted by bastnäsite-(Ce) and polymorphic TiO₂ phases (anatase and rutile) mainly represent the rare metal minerals. In albite–aegirine rocks, trace element minerals are predominantly represented by cubic crystals of “metaloparite”, which are partially or completely replaced by bastnäsite-(Ce) and polymorphic TiO₂ phases such as anatase and rutile. Additionally, Th-bearing zircon (up to 17.7 wt% ThO₂) and a variety of unidentified minerals containing REEs, Th, and Nb were detected. The obtained data indicate that bastnäsite-(Ce) is the result of the recrystallization of “metaloparite” accompanied by the formation of Th-bearing zircon and Nb-bearing rutile (up to 9.9 wt% Nb₂O₅) and the separation of various undiagnosed, unidentified LREE phases. Our studies show that remobilization of LREEs, HFSEs, and local enrichment of rocks in these elements occurred due to the effects of residual fluid enriched in fluorine and carbon dioxide. Full article

The Kalba–Narym metallogenic belt is located in East Kazakhstan, which displays rare metal mineralization. The Kvartsevoye rare metal Li–Ta–Nb deposit is located in the north-western ore district. This study presents the results of geological, mineralogical, geochemical, and geochronological analyses of rare metal granite pegmatites. Rare metal mineralization belongs to a field of variably differentiated pegmatites, including barren, quartz–albite–muscovite, muscovite, and muscovite–quartz–albite microcline mineral associations. This study established that the rare metal mineralization is localized in the quartz–albite–muscovite zone. The main concentrator minerals of rare metals are spodumene for Li and tantalite–columbite for Ta and Nb. Ar/Ar dating of the muscovite allowed us to establish the age of mineralization during the period of 288–285 Ma. The present study enabled the linkage of rare metal mineralization with the differentiation processes of the granites of the Kalba complex. Full article

The hydrochemical characteristics and evolution mechanisms of groundwater are critical for accurately understanding the input–output budget of hydrochemical constituents in pristine groundwater. However, few studies have analyzed the changes in mineral precipitation and dissolution equilibrium along the groundwater flow path, especially in arid regions. This study integrated hydrochemical analysis, stable isotopes, and inverse hydrochemical modeling to identify groundwater recharge sources, hydrochemical evolution, and controlling mechanisms in an arid endorheic watershed, northwestern China. A stable isotope signature indicated that groundwater is primarily recharged by high-altitude meteoric precipitation and glacial snowmelt. The regional hydrochemical type evolved from HCO₃·Cl-Ca·Mg·Na types in phreatic aquifers to more complex HCO₃·Cl-Ca·Mg Na and HCO₃·Cl-Na Mg types in confined aquifers and a Cl-Mg·Na type in high-salinity groundwater. The dissolution of halite, gypsum, calcite, K-feldspar, and albite was identified as the primary source of dissolved substances and a key factor controlling the hydrochemical characteristics. Meanwhile, hydrochemical evolution is influenced by cation exchange, mineral dissolution–precipitation, and carbonate equilibrium mechanisms. Inverse hydrochemical modeling demonstrated that high-salinity groundwater has experienced intensive evaporation and quantified the transfer amounts of associated minerals. This study offers deeper insight into hydrochemical evolution in the Golmud River watershed and elucidates mineral transport and enrichment mechanisms, providing a theoretical basis for investigating hydrochemical metallogenic processes. Full article

The Eastern Carpathians are thrust to the east and north over their Eastern European foreland, tectonically covering it over an area several hundred kilometers across. Information about the nature of the underthrust part of the Carpathian foreland can be obtained from the rock fragments preserved in the sedimentary successions of the Carpathian fold and thrust belt, specifically in the Outer Dacides and the Moldavides. Fragments of felsic rocks occurring within the sedimentary units of the Upper Cretaceous successions of the Moldavides have long been attributed to the Cuman Cordillera—an intrabasinal ridge in the Eastern Outer Carpathians. This work is the first complex geochemical and geochronological study on the exotic igneous clasts of the Cuman Cordillera. Igneous clasts from the southern part of the Moldavides (Variegated clay nappe/formation) are investigated here. They include mainly granites and rhyolites. Phaneritic rocks are composed of cumulus plagioclase, albite, amphibole and biotite, and intercumulus quartz and potassium feldspar, with apatite, magnetite, sphene, and zircon as main accessories, while the porphyritic rocks have a mineral assemblage similar to that mentioned above, displayed in a porphyritic texture with a usually crystallized groundmass. SHRIMP U-Pb zircon dating indicated the 583–597 Ma age interval for magma crystallization. Based on calcareous nannofossils, the depositional age of the investigated igneous clasts is Cenomanian to Maastrichtian, implying that the Cuman Cordillera was an emerged piece of land, herein an active source of sediments in the flysch basin for at least 40 Ma, from the Early Cretaceous (Aptian) to the Late Cretaceous (Maastrichtian). The intrusive and subvolcanic rocks show similar trends for trace and major elements, evincing their comagmatic nature. The enrichment in LILE and LREE relative to HFSE and HREE, as well as the element anomalies (e.g., negative Nb, Ta, and Eu and positive Rb, Ba, K, and Pb) suggest a convergent continental plate margin tectonic setting. Mineral chemistry suggests magma crystallization in relatively oxic conditions (magnetite series), during ascent within a depth of 15 km to 5 km. The igneous rocks attributed to the Cuman ridge display compositional and geochronological features similar to Brno and Thaya batholiths in the Brunovistulian terrane, which could be a piece of the Carpathian foreland not covered by the Tertiary thrusts. Our data confirm the non-Carpathian origin of the igneous clasts, revealing a Neoproterozoic history of the Carpathian foreland units, which include a Cadomian/Pan-African continental arc, exposed mainly during the Late Cretaceous as an intrabasinal island of the Alpine Tethys, traditionally known as the Cuman Cordillera. Full article

This work investigated the structural response and phase transformation dynamics of silica-bearing cherts subjected to high-temperature processing (up to 1400 °C) and prolonged mechanochemical activation. Through a combination of X-ray diffraction (XRD) with Rietveld refinement, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and transmission electron microscopy (HRTEM), we trace the crystallographic pathways of quartz, moganite, tridymite, and cristobalite under controlled thermal and mechanical stress regimes. The experimental results demonstrated that phase behavior is highly dependent on intrinsic properties such as initial phase composition, impurity presence, and crystallinity. Heating at 1400 °C induced irreversible conversion of quartz, moganite, and tridymite into cristobalite. Samples enriched in cristobalite and tridymite exhibited notable increases in crystallinity, whereas quartz-dominant samples showed either stability or a decline in structural order. Rietveld analyses underscored the critical influence of microstrain and crystallite size on thermal resilience and phase persistence. Thermal profiles revealed by DSC and TGA expose overlapping processes including polymorphic transitions, minor phase dehydration, and redox-driven changes, likely associated with trace components. Mechanochemical processing resulted in partial amorphization and the emergence of phases such as opal and feldspar minerals (microcline, albite, anorthite), interpreted as the product of lattice collapse and subsequent reprecipitation. Heat treatment of chert leads to a progressive rearrangement and recrystallization of its silica phases: quartz collapses around 1000 °C before recovering, tridymite emerges as an intermediate phase, and cristobalite shows the greatest crystallite size growth and least deformation at 1400 °C. These phase changes serve as markers of high-temperature exposure, guiding the identification of heat-altered lithic artefacts, reconstructing geological and diagenetic histories, and allowing engineers to adjust the thermal expansion of ceramic materials. Mechanochemical results provide new insights into the physicochemical evolution of metastable silica systems and offer valuable implications for the design and thermal conditioning of silica-based functional materials used in high-temperature ceramics, glasses, and refractory applications. From a geoarchaeological standpoint, the mechanochemically treated material could simulate natural weathering of prehistoric chert tools, providing insights into diagenetic pathways and lithic degradation processes. Full article

B₄C is beneficial for forming a glassy film that is effective at impeding oxygen diffusion and improving the oxidation resistance of coatings at high temperature. The effect of B₄C content on the oxidation resistance of a B₄C-SiO₂–Albite/Al₂O₃ (BSA/AO) double-layer coating by the slurry brushing method at 900 °C was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and differential scanning calorimetry (DSC) with thermogravimetric analysis (TGA) in this work. It is indicated that the composite coating with 20 wt% B₄C exhibits excellent oxidation resistance at high temperature, which shows a mass loss of only 0.11% for the coated carbon block after being exposed to 900 °C for 196 h. This is attributed to the in situ formation of a thin, dense glass layer with good self-healing ability at the interface of the B₄C-SiO₂–Albite/Al₂O₃ composite coating within 1 h and the persistence and stability of the dense glass layer during exposure. The mechanism is discussed in detail. Full article

In this study, we performed microtextural, major/minor element, and Sr-isotope analyses on hornblende and plagioclase (as phenocrysts, groundmass, or inclusions) from the Early Cretaceous Jiagou pluton (eastern North China Craton), to elucidate the magma source, possible magma mixing process, and the transition from low-Mg to high-Mg adakitic magmas. Petrographic study and electron microprobe (EMP) analyses reveal well-defined compositional zoning in hornblende and plagioclase phenocrysts. Outward from the core (first zone), the second and third zones show pronounced oscillatory zoning and significant variations in Mg# and An%, while the fourth zone is relatively homogeneous. A corroded albitic plagioclase core with sieve texture is enclosed in the first zone and locally intergrows with worm-like quartz streaks and fine hornblende inclusions, featuring Mg# = 81 (core) and 62 (rim). The new plagioclase infill has An% = 14–41. The corroded plagioclase has an initial ⁸⁷Sr/⁸⁶Sr = 0.7074, while that of zoned phenocrystic plagioclase ranges from 0.7068 to 0.7079, suggesting EMI and EMII mantle input. Inclusion hornblende is low in Ti and Cr, while phenocrystic hornblende shows higher Cr in the first zone and lower Cr in the outer zones. The newly discovered mafic microgranular enclaves (MMEs) and regional geochemical data suggest three major magma mixing events. The felsic parental magma was likely originated from a mixed EMI–EMII mantle source before mixing with a mafic magma derived from the partial melting of, successively, a low-Cr and a high-Cr peridotite. Our findings support a petrogenetic model of lower crustal delamination and highlight the critical role of repeated mafic injections in generating high-Mg adakitic magmas. Full article