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A comparative analysis of the carbonate sedimentation conditions in two Paleoproterozoic basins (Onega and Pana-Kuolajarvi), located in the southeastern and northern areas of the Late Archean Karelian Craton is presented. The carbonate accumulation began in both basins during the Late Jatulian. Carbonate rocks in the Onega succession are predominantly dolostones, including stromatolite varieties; in the Pana-Kuolajarvi succession, they comprise both dolostones and limestones. During the Late Jatulian, cyanobacteria thrived in coastal marine settings of the Onega Basin. Some areas of the basin lost connection with the open sea at this time, facilitating the development of evaporation processes. The Pana-Kuolajarvi Basin lacked such diversity of cyanobacterial communities and any evaporitization. The geological and lithological data suggest that shallow, lagoon, playa lake, and sabkha environments existed in the Onega Basin in the Late Jatulian. The Pana-Kuolajarvi Basin was characterized by shallow (with occasional increased water input from the continent) and open marine settings. The geochemical characteristics of carbonate rocks obtained in our work lead to the same facies conclusions. Stromatolites in the Onega Basin were formed mainly in the intertidal zone. Occasionally, the connection of basin with the open sea was reduced and the conditions approached the lagoonal type. The oxic conditions existed for a limited time during the Jatulian only in the Onega Basin. Basically, the oxygen content in both sedimentation basins was close to the disoxic/oxic transition boundary. Fluctuations in the Ce anomaly magnitude in stromatolite laminas reflect changes in the oxygen content in water at immediate contact with the stromatolite buildup, suggesting the existence of oxygen "oases" in the basin with disoxic and oxygen-deficient conditions. Conclusions about redox conditions existing in the basin, based only on geochemical markers, are not sufficient, whereas conclusions about the carbonate sedimentation conditions prevailing in the basin agree maximally with the geological and lithological data based on several geochemical characteristics, such as REE spectra, Ce and Eu anomaly values, and ratios of individual REEs supported by the pair correlations between redox-sensitive elements. [ABSTRACT FROM AUTHOR]

Oncoids, significant sedimentary structures within the Jurassic strata of the Mediterranean Region, serve as valuable indicators of paleoenvironmental conditions during their formation. One of the important examples of oncoids has been discovered in the Pliensbachian (Early Jurassic) Ammonitico Rosso Facies (ARF) of the eastern Sakarya Zone (Eastern Pontides, NE Turkey). This study presents the first comprehensive sedimentological and petrographic (textural and compositional characteristics) examination, as well as geochemical analyses (trace and rare earth elements) of these Fe-Mn oncoids. The oncoids consist of nuclei coated with irregular laminae and exhibit a range of sizes, from 10 to over 45 mm, displaying various colours such as brown, reddish, and metallic-looking. They mostly have a discoidal shape, although some are spherical. The nuclei consist of bioclastic wackestones, containing remnants of ammonoid shells. Some oncoids, especially the discoidal forms, have multiple nuclei. The cortex of the oncoid predominantly consists of wrinkled bands displaying micritic laminae, with an abundance of filamentous bodies and the local presence of encrusting microfossils. In the cortex of the oncoids, iron predominates over manganese, and there are compositional variations within the cortex, especially enriched in Si, Fe, and Ca. They predominantly fall within the region associated with hydrothermal Fe and Mn sediments, as indicated by discrimination diagrams involving Ni, Co, Zn, and plots of Ce/Ce* vs Y/HoN and Nd contents, suggesting a hydrothermal origin. Furthermore, their rare earth elements (REE) chemistry displays distinct Y/Ho, Sm/Yb, Ce/Ce, and Nd values, indicating the presence of seawater mixing with hydrothermal fluids. However, they show relatively low Sm/Yb, Y/Ho, Eu/Sm, Nd/YbN, and La/Yb values, suggesting a limited contribution from hydrothermal sources to the surrounding seawater. Nevertheless, the cortex of the oncoids exhibits a complex and variable mineralogy that changes over short distances, implying the dynamic nature of the depositional environment, characterized by fluctuating hydrological regimes, varying oxygen levels, elemental supply, and the saturation of specific elements in seawater. The increased presence of specific trace elements, including Fe, and REE during this period, is likely linked to hydrothermal fluid input into marine environments, coinciding with intensified syn-sedimentary tectonic activity, where ongoing extensional tectonic movements occasionally influenced paleoenvironmental conditions. In these conditions, the formation of oncoids is influenced by various sedimentary factors, including the availability of metal sources, specific paleoenvironmental conditions, and the presence of microbial organisms, thereby enriching our understanding of palaeogeography during the Early Jurassic period. Additionally, the studied oncoids, with their comparable stratigraphic position and petrographic characteristics to those in both the eastern and western parts of the Tethyan basin, underscore their significance in palaeogeography and stratigraphy. [ABSTRACT FROM AUTHOR]

In this study, we attempt to illustrate fossil vertebrate dental tissue geochemistry and, by inference, its extent of diagenetic alteration, using quantitative, semi-quantitative and optical tools to evaluate bioapatite preservation. We present visual comparisons of elemental compositions in fish and plesiosaur dental remains ranging in age from Silurian to Cretaceous, based on a combination of micro-scale optical cathodoluminescence (CL) observations (optical images and scanning electron microscope) with in-situ minor, trace and rare earth element (REE) compositions (EDS, maps and REE profiles), as a tool for assessing diagenetic processes and biomineral preservation during fossilization of vertebrate dental apatite. Tissue-selective REE values have been obtained using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), indicating areas of potential REE enrichment, combined with cathodoluminescence (CL) analysis. Energy dispersive X-ray spectroscopy (EDS) mapping was also used to identify major elemental components and identify areas of contamination or diagenetic replacement. We conclude that the relative abilities of different dental tissues to resist alteration and proximity to the exposure surface largely determine the REE composition and, accordingly, the inferred quality of preserved bioapatite. [ABSTRACT FROM AUTHOR]

The article presents a mineralogical, petrographic, and geochemical characterization of the rare earth mineralization of the Kotlyarivka ore occurrence, which was discovered by drill hole 114 in the south-western part of the Krynychky plagiogranite-migmatite dome during geological exploration of the southern part of the Verkhivtseve greenstone structure and its granitoid framing. Rare earth elements (REE) are critically important minerals for many countries, including EU, USA, Canada, and Australia, and other developed countries. The Ukrainian Shield is one of the largest REE metallogenic provinces in Europe. In particular, the Middle Dnipro megablock is a prospective but under-explored region for the discovery of new REE deposits. Its prospects are associated with subalkaline and alkaline Mesoarchaean granitoids and metasomatites of the Tokivske, Mokra Moskovka, and Demuryno complexes. Comprehensive studies of core samples from primary and weathered rocks of the Kotlyarivka occurrence have revealed that monazite is the mine mineral concentrator of REE and yttrium. It was determined that monazite underwent two main stages of alterations: endogenic hydrothermal-metasomatic and hypergenic associated with weathering crust formation. Other minerals, such as apatite, zircon, and leucoxene, also contain lanthanides and yttrium. The findings highlight the critical need for the development of the mineral resource base for REE, involving the re-evaluation of known deposits and the search for new ones. This usually requires scientific support and modern laboratory equipment to accurately determine the composition and genetic features of productive mineralization. Despite some challenges, such as the limited number of samples available for study, the research provided new important data that contributed to the understanding rare earth elements mineralization in the studied Kotlyarivka occurrence and the Middle Dnipro region as a whole. Continuing such studies and conducting comprehensive full-scale research on REE mineralization in the Central Dnipro region will yield high theoretical and practical results.

Silica-based adsorbents (Silica gel 60 and Silochrom S-80) chemically modified with aminophosphonic groups with various surface concentrations have been proposed for the preconcentration of rare earth elements (REE). The resulting adsorbents were studied by FT-IR, SEM, TGA and compared with unmodified matrices. Adsorbents quantitatively extracted REE from solutions with pH 1.0–5.0. Solid phase extraction at pH 1.0–2.0 made it possible to quantitatively separate rare earth elements from the predominant amounts of accompanying metal ions. An increase in the concentration of aminophosphonic groups on the silica surface led to an increase in the adsorption capacity of the adsorbent for Gd(III) both in batch and dynamic modes. A technique for solid-phase extraction followed by inductively coupled plasma optical emission (SPE-ICP-OES) determination of REE has been developed; it includes pumping 200 mL of the sample solution (pH 1) through a mini-column with an adsorbent at a flow rate of 1 mL min−1, eluting REE with 10 mL of 1 M HNO3 (preconcentration factor 20), and then determination of the elements in the eluate by ICP-OES. The technique was used for the determination of REE in lignite and coal from the Krasnoyarsk Krai (Russia). The accuracy of the results was confirmed by comparison with ICP-MS determination and by the analysis of certified reference material of coal ash. [ABSTRACT FROM AUTHOR]

The behavior of a number of REE and Am(III) during their extraction from nitric acid solutions with iron and manganese dibutyl phosphoric acid (HDBP) compounds in various diluents was studied. An increase in the concentration of iron and manganese in the organic phase leads to an increase in the REE distribution ratios and, in some cases, to a noticeable change in the element separation factors. The element separation factors significantly differ depending on the diluent. The increase in the separation factors of pairs of elements can reach high values. For example, the Er/Dy separation factor in toluene increases by a factor of 5, and the Dy/Tb separation factor in chloroform, by a factor of 7. The use of decalin as a diluent leads in most cases to a maximum increase in the REE distribution ratios. In the system with an o-nitrotoluene (ONT) diluent, at a certain ratio of HDBP to Fe(III), the separation factors of americium and REE (except cerium) are high enough to allow their separation. The influence of the transition metal and solvent on the distribution and separation of REE is discussed. [ABSTRACT FROM AUTHOR]

Chemical (REE and major elements) and isotope (δ13C, δ18O) composition of carbonate manganese ores and manganese-bearing carbonates of the Usa deposit (Siberia, Russia) were studied. Received data on the composition of REE exhibit both the distinct negative (Ce/Ce*PAAS < 1) and positive (Ce/Ce*PAAS˃1) cerium anomalies and the positive Eu-anomaly (Eu/Eu*PAAS˃1). Negative Eu-anomalies are not observed. The contents of Mn, Fe, REE, and Ce-anomalies show a positive correlation with each other. Ce-anomalies and the amount of manganese and REE in relation to the carbon isotope composition (δ13C) show a negative relationship and indicate that oxidized carbon of organic matter played an important role in the concentration of manganese and REE in manganese ores. The chemical and isotope composition of examined rocks indicates on secondary formation of Mn-ores. Two major phases and sources are distinguished in the ore-forming process characterized by different chemical (REE and ore elements) and isotope composition: (i) high-grade manganese ores (with high contents of REE and light carbon isotope composition) and (ii) low-grade manganese ores (with low contents of REE and heavy carbon isotope composition). [ABSTRACT FROM AUTHOR]

The article presents a mineralogical, petrographic, and geochemical characterization of the rare earth mineralization of the Kotlyarivka ore occurrence, which was discovered by drill hole 114 in the south-western part of the Krynychky plagiogranite-migmatite dome during geological exploration of the southern part of the Verkhivtseve greenstone structure and its granitoid framing. Rare earth elements (REE) are critically important minerals for many countries, including EU, USA, Canada, and Australia, and other developed countries. The Ukrainian Shield is one of the largest REE metallogenic provinces in Europe. In particular, the Middle Dnipro megablock is a prospective but under-explored region for the discovery of new REE deposits. Its prospects are associated with subalkaline and alkaline Mesoarchaean granitoids and metasomatites of the Tokivske, Mokra Moskovka, and Demuryno complexes. Comprehensive studies of core samples from primary and weathered rocks of the Kotlyarivka occurrence have revealed that monazite is the mine mineral concentrator of REE and yttrium. It was determined that monazite underwent two main stages of alterations: endogenic hydrothermal-metasomatic and hypergenic associated with weathering crust formation. Other minerals, such as apatite, zircon, and leucoxene, also contain lanthanides and yttrium. The findings highlight the critical need for the development of the mineral resource base for REE, involving the re-evaluation of known deposits and the search for new ones. This usually requires scientific support and modern laboratory equipment to accurately determine the composition and genetic features of productive mineralization. Despite some challenges, such as the limited number of samples available for study, the research provided new important data that contributed to the understanding rare earth elements mineralization in the studied Kotlyarivka occurrence and the Middle Dnipro region as a whole. Continuing such studies and conducting comprehensive full-scale research on REE mineralization in the Central Dnipro region will yield high theoretical and practical results. [ABSTRACT FROM AUTHOR]

Polymetallic black shale from the Buckton deposit in Alberta, Canada, is an undeveloped resource for V, rare earth elements (REEs), Ni, Li, and a few other metals. In this work, the valuable elements are extracted from the shale using a low-temperature sulfation roasting-water leaching method. Sulfation roasting enables the destruction of mineral phases releasing V ions as well as REEs, Li and Ni. We compare microwave and conventional roasting under varying temperature, sulfuric acid dosage, and time, followed by water leaching, to determine the optimum leaching efficiencies of metals. Microwave roasting consumes less energy than conventional roasting for similar release % of metals in laboratory-scale as well as scaled-up process (5 times larger) with a significant reduction in roasting temperature (by 40 °C) and time (by 30 min). A maximum leaching efficiency of 100% of gadolinium, 85% of ytterbium, 84% of Ce, 76% of Ni, 74% of V, 59% of Li, 34% of neodymium, 21% of yttrium, and 13% of La was achieved. We have identified the host minerals of several of the valuable elements using detailed mineralogical analyses which can be useful in formulating more efficient metal release strategies. [ABSTRACT FROM AUTHOR]

This paper presents the results of research on the possibility to obtain CRMs (REEs) and industrial metals (Zn) from slag as a waste generated as part of zinc and lead extraction processes. Physicochemical methods were used to separate CRM and Zn concentrates: magnetic separation, sintering with NaOH and leaching with selected mineral acids. After analysing the obtained results, it was found that the use of concentrated hydrochloric acid and a temperature of 363 K for leaching was effective in separating REEs from slags obtained from current production. The recovery rate in this case ranged from 83.73% for La to 98.03% for Eu. For slag samples (M1) obtained from current production from ZGH Bolesław S.A.(Poland) as well as HC Miasteczko Śląskie S.A. (Poland) and treated with concentrated HCl, the leaching level of Bi, Zn, Ni, Mn and P exceeded 90% compared to the content in the reference sample. For a historical slag sample from Ruda Śląska (Poland), treatment with concentrated HCl yielded a high leaching level of Cd (70.90%), Pb (78.66%), As (72.49%) and Mo (61.90%). A concentrate containing 1.64% of REEs and 67.1% of Zn was isolated from the solutions obtained after leaching by precipitation. An economic analysis of an REE concentrate extraction facility was also performed. For an operation of 17 years, the calculated NPV was −26,352,644 million EUR. The obtained results indicate that, for the analysed facility, recovering metals and critical raw materials from slag as a waste mass is not economically effective. [ABSTRACT FROM AUTHOR]

The demand for rare-earth elements is expected to grow due to their use in critical technologies, including those used for clean energy generation. There is growing interest in developing unconventional rare-earth element resources, such as coal and coal byproducts, to help secure domestic supplies of these elements. Within the U.S., Appalachian Basin coals are particularly enriched in rare-earth elements, but recovery of the elements is often impeded by a resistant aluminosilicate matrix. This study explores the use of calcination and sodium carbonate roasting pre-treatments combined with dilute acid leaching to recover rare-earth elements from Appalachian Basin coals and underclay. The results suggest that rare-earth element recovery after calcination is dependent on the original mineralogy of samples and that light rare-earth minerals may be more easily decomposed than heavy rare-earth minerals. Sodium carbonate roasting can enhance the recovery of both light and heavy rare-earth elements. Maximum recovery in this study, ranging from 70% to 84% of total rare-earth elements, was achieved using a combination of calcination and sodium carbonate roasting, followed by 0.25 M citric acid leaching. [ABSTRACT FROM AUTHOR]

Porphyry indicator zircons (PIZ) are often used as an exploratory guide to distinguish fertile granitoid-hosted porphyry copper deposits (PCD). Alumina-saturated granitoids with higher zirconium (> 200 ppm) contents are often the hosts of PCD. REE profiling of zircon is used here to evaluate the chemistry of zircon from a blend of I- and A-type granitoids that hosts the 'Kaziranga' porphyry copper mineralization in the Karbi Hills of the Shillong Plateau. Zircon Hf(t) (1.69–9.88; av.4.65) and whole rock 87Sr/86Sr (0.703) of the Kaziranga granitoids suggest magma derivation in an intraplate or primitive island arc tectonic setting, in which the active mechanism of magma derivation was partial melting of a metasomatically enriched lithospheric mantle that was probably fertilized by an intraplate mantle plume. The fertility indicators with PIZ are grouped with respect to the distribution pattern of normalized REEs, as they exhibit low LREE and enriched HREE, large + Ce, and small -Eu anomalies. The hypogene alteration zones have developed on a regular basis, the potassic alteration zone being close to the central zone around Kuthori in the north Karbi Hills. Although the hosts demonstrate expansion and development of the hypogene alteration zones, the zircons from the mineralized granitoids of Kuthori central zone and granitoids of the nearby Panbari–Dallamara shear zone have similar REE pattern. The target zone's zircon has higher values of ΣHREE, U, Th, Y, Nb, and Hf. The admissible range of fertile PCD is matched by the cross plots of critical element ratios, demonstrating high calculated Ti in zircon temperature (up to 828 °C). [ABSTRACT FROM AUTHOR]

This research presents the results of a comprehensive study of mineralogical and geochemical features of REE distribution in coals of Central Kazakhstan deposits—Karaganda coal basin and Shubarkol deposit, which have large hard coal reserves and are industrially important for the coal industry of Kazakhstan; the research is based on 205 samples of clayey interlayers and coal seams. It shows basic patterns of distribution and features of concentration for impurity elements, gives an estimate of the impurity elements concentration, including REE, defines conditions and factors of their accumulation, and studies features of their forms in coal and coal-bearing rocks, which allows estimating the mechanisms of their migration and conditions of accumulation. According to the results of geochemical indicators, the article establishes the factors of REE dislocation, reveals the composition of margin rocks that have influenced REE concentration in coal seams, and the presented latest data on mineralogy allowed to establish the ways of their transportation to the paleobasin during the syn- and epigenetic periods of formation of the coal deposits of Central Kazakhstan being researched. It was found that the coals are insignificantly enriched with heavy lanthanides from Ho to Lu. The distribution curves of UCC normalized REE values in the coals are similar and coincide, but they are less than the average value for world coal, and amount to only one-third of the UCC. It was found that the highest concentrations of all REE are characteristic of clayey interlayers and oxidized coals. The La/Yb ratio in this case increases upwards along the section, indicating mainly clastogenic mechanism of REE delivery to the coals. In coal and clay samples, the predominant mineral form of REE is light lanthanide phosphates. Identified particles of REE from minerals and their composition peculiarities suppose autigene nature of their formation. The formation of the bulk of autigene minerals occurred during the maturation of brown coals and their transformation into hard ones. [ABSTRACT FROM AUTHOR]

[Objective] The aims of this study are to investigate the sediment sources of slope erosion in production and construction projects, and to implement the targeted soil and water conservation measures to mitigate soil and water loss caused by human disturbance. [Methods] Indoor simulated rainfall tests combined with REE tracer technique were conducted to examine the erosion characteristics and contributions from different areas of engineering deposits with varying gravel contents [0 (pure soil), 10%, 20%, 30%] under the rainfall intensity of 90 mm/h. [Results (1) The amount of soil erosion of all areas of different gravel-containing engineering deposits was the largest in the down slope area, while the average erosion contribution of the down slope area (57.40%) was larger than that of the upper slope area and the middle slope area, which indicated that the down slope area was the main source of sediment. (2) The erosion contribution of the middle and down slope areas of the gravel-containing engineering deposits was significantly smaller than that of the pure soil deposits. The erosion contribution of the upper and middle slope areas of the gravel-containing engineering deposits was significantly greater than that of the pure soil deposits, and the erosion contribution of the down slope area of the gravel-containing engineering deposits was significantly less than that of the pure soil deposits. (3) The effect of gravel content on the amount and contribution of erosion at the down slope area was more significant (p<0.05). In the gravel-containing engineering deposits, the amount of erosion at the upper and down slope areas of the 20% gravel content engineering deposits was significantly greater than that of engineering deposits with 10% and 30% gravel contents. The contribution of erosion at the upper slope area of the engineering deposit with 10% gravel content was significantly greater than that engineering deposits with 20% and 30% gravel contents, and the contribution of erosion at the down slope area was significantly less than that engineering deposits with 20% and 30% gravel contents. [Conclusion] Among all the engineering deposits with gravel content, the erosion contribution rate of the down slope area is the largest, which indicates that the down slope area is the main source of sediment on the slope of the engineering deposits, and the protection and treatment of the down slope area should be strengthened. [ABSTRACT FROM AUTHOR]

Rare earth elements (REE) of the host rocks (Fe-siliceous rocks) and manganese ores of the Nchwaning Mine (Hotazel Formation, Kalahari manganese field) were studied. An important feature of manganese ores and host rocks (Fe-silicites) is the presence of negative and positive cerium (Ce/Ce*) and europium (Eu/Eu*) anomalies. This testifies to the complex and long history of the formation of manganese ores. Initial metal-bearing (Mn, Fe) sediments of a shallow-water basin with a negative cerium anomaly (Ce/Ce*) were enriched in europium (positive Eu/Eu*) at different stages of lithogenesis both during sedimentation (underwater discharge of hydrothermal fluids), and subsequent processes of hydrothermal transformation of the ore-bearing strata. The source of manganese could be basaltic andesites of the underlying Ongeluk Formation. [ABSTRACT FROM AUTHOR]

The stratiform and vein-hosted Kapunda Cu deposit in South Australia contains a saprolitized hydrothermal vein with 12.37 wt.% total rare earth oxide (TREO). The vein was analyzed by X-ray diffraction, scanning electron microscopy, synchrotron-based X-ray fluorescence microscopy and electron backscatter diffraction to understand the controls that govern high-grade REE accumulation during periods of intense weathering. Petrological assessments indicate the transformation of an apatite-calcite-aluminosilicate-bearing protolith to a supergene assemblage of Fe-oxides, kaolinite and REE-phosphate minerals that include rhabdophane-(Ce), monazite-(Ce) and florencite-(Ce). This transformation was facilitated by progressive acidification of the weathering fluid, which is indicated by: 1) the increasing crystallinity of authigenic Fe-oxides and kaolinite, which led to REE desorption; 2) the textural evolution and increase in grain size of authigenic REE-phosphates from nanoscopic crystallites, to acicular needles, to micro-scale hexagonal prisms; 3) the late dissolution of REE-phosphates; and 4) the replacement of goethite by jarosite, whose sulfate component originated from the oxidation and weathering of proximal sulfide minerals. Alongside the depletion of pH-buffering carbonate minerals that are indicated by the preservation of calcite menisci, this sulfide dissolution also facilitated acid generation. Results illustrate how highly acidic weathering fluids might facilitate either REE mobilization or REE accumulation in regolith. High-grade REE accumulation under acidic supergene conditions is prioritized when the host-rock contains a significant source of depositional ligands (i.e., phosphate in the form of apatite) that can be readily leached during intense weathering. Exploration companies should therefore assay routinely for REEs in any heavily weathered phosphatic rock, due to the observed efficiency of phosphate minerals as geochemical traps for REE accumulation. [ABSTRACT FROM AUTHOR]

In this study, we attempt to illustrate fossil vertebrate dental tissue geochemistry and, by inference, its extent of diagenetic alteration, using quantitative, semi-quantitative and optical tools to evaluate bioapatite preservation. We present visual comparisons of elemental compositions in fish and plesiosaur dental remains ranging in age from Silurian to Cretaceous, based on a combination of micro-scale optical cathodoluminescence (CL) observations (optical images and scanning electron microscope) with in-situ minor, trace and rare earth element (REE) compositions (EDS, maps and REE profiles), as a tool for assessing diagenetic processes and biomineral preservation during fossilization of vertebrate dental apatite. Tissue-selective REE values have been obtained using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), indicating areas of potential REE enrichment, combined with cathodoluminescence (CL) analysis. Energy dispersive X-ray spectroscopy (EDS) mapping was also used to identify major elemental components and identify areas of contamination or diagenetic replacement. We conclude that the relative abilities of different dental tissues to resist alteration and proximity to the exposure surface largely determine the REE composition and, accordingly, the inferred quality of preserved bioapatite.

Critical minerals are those minerals that are essential for modern technologies, economic development and national security. Resilent acess to critical minerals is required for low carbon technologies in line with India's COP26(COP26 stands for the 26th Conference of the Parties to the United Nations Framework Convention on Climate Change (UNFCCC). The UNFCCC is a treaty that came into effect in 1994. The COP is the supreme decision-making body of the UNFCCC, and all states that are parties to the convention are represented at the COP.) commitemnts. Critical minerals are distinguished by distinctive chemical and physical properties. Apart from geological processes that determine the physical availability of these minerals there are a host of other factors that influence access to the resources on the ground such as quantity of mineral present, its grade, and the assessment of the optimum methods for mining and processing of ore. Therefore, reliable estimates of the total amount of these minerals that may be available in the Earth's crust are difficult to ascertain at preliminary level of exploration. This implies building capacity at each value chain stage (mineral exploration, mineral extractions, intermediate processing, manufacturing, and recycling). India is dependent on import for many critical minerals including lithium, cobalt, and nickel. Thrust has been given in National Mineral Policy 2019 towards exploration of energy critical minerals, for which the country is mainly dependent on imports. To boost the critical minerals supply chain in India, a number initiative that the government has taken will be discussed in this paper. [ABSTRACT FROM AUTHOR]

One of the most prevalent pollutants that pollute the environment is nitrogen oxide (NOx). NO and NO2 gases, which are hazardous to both human health and the environment, are included in NOx. The rare earth element Ce doped metal oxide semiconductor (MOS) ZnO is employed to reveal their NO gas sensing properties. Based on density functional theory (DFT) calculations, the optimized surface of ZnO (0001), Ce‐doped ZnO (0001), adsorbate structure of NO, and adsorbate NO on the modified ZnO (0001) surface are obtained. The gas sensing properties are examined through adsorption energy, Bader charge analysis, charge density difference (CDD), charge transfer, band structure, total density of state (DOS), and partial density of states (PDOS). For the Ce‐doped ZnO (0001) surface the NO adsorption energy is more negative than the bare ZnO. From the observation of Bader charge analysis, the charge transfer value increases from the substrate to adsorbate after doping with Ce, which indicates that the Ce‐doped ZnO (0001) surface is more favorable for NO gas sensing. Favorable electronic properties and suitable adsorption energy of Ce‐doped ZnO can be a potential gas sensor for NO molecule. The obtained DFT results are also compared with the existing experimental results. [ABSTRACT FROM AUTHOR]

The study of Neoproterozoic carbonate sequences is complicated due to several variables influencing the geochemical and mineralogical composition, compounded by the scarcity of environmental analogs. The Tamengo Formation in the Corumbá Group is one of the most extensively studied archives of the Neoproterozoic in South America and encompasses Ediacaran guide fossils of Corumbella werneri and Cloudina lucianoi. This research focused on a marl sample containing well-preserved bioclasts of exoskeletons of Corumbella werneri, which is one of the earliest biomineralizing organisms. By utilizing diverse techniques such as optical and SEM microscopy, QEMSCAN imaging, electron microprobe, in situ ICP-MS, and isotope analyses, this study reveals primary and secondary signals in the bioclastic exoskeletons and the matrix within. These findings shed light on the sedimentary environment and diagenetic history of the Tamengo Formation. It is revealed that Corumbella werneri likely inhabited calm conditions, just below the base of storm waves and above a sharp chemocline at the bottom. In addition, the presence of distinct hydrothermal signals in the composition of REEs indicates a potential magmatic event that occurred in the region after the deposition of the succession. This pilot study highlights that the history recorded in the Neoproterozoic rocks of the Tamengo Formation is complex, and thus more detailed studies integrating lithological, paleontological, and geochemical parameters are necessary to reach a correct interpretation of this sequence. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) are crucial to numerous industries of high-technology as raw materials. The growth of a long-term relationship between REE supply and demand to develop hi-tech industries is becoming tight in the world market, while the mineral supply chain is being distorted by COVID-19. The availability of information and data regarding the REE resource potential and characteristics are interesting research subjects to examine its economic value as alternative sources. This research aims to provide basic information about the existence and characteristics of REEs in cassiterite-associated minerals located in Bangka and Belitung Islands. Fifty-one samples consisting of primary deposits, placer deposits, concentrates, and tailings were collected from the southern Bangka and Belitung region. The samples were analyzed using microscope, x-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and inductively coupled plasma mass spectrometry (ICP-MS). The results show that the REE-bearing minerals comprised monazite and xenotime. Monazite, the most dominant REE-bearing mineral, contains light REEs (Ce-dominant), while xenotime contains heavy REE (Y-dominant). The results of SEM with energy-dispersive spectroscopy show that monazite contains other LREE (La and Nd), and xenotime also contains other HREE (Dy and Yb). Moreover, zircon and ilmenite can be considered as economical cassiterite-associated minerals that have other mineral inclusion, but have no REE contain. [ABSTRACT FROM AUTHOR]

Iron oxyhydroxides extracted from present-day biofilms with the Fe-oxidizing bacteria Arthrobacter spp., Gallionella spp., and Leptothrix ochracea in the northwest of the East European Platform display a significant content of rare earth elements (up to 1100 ppm). The REE concentration in oxyhydroxides produced by active bacterial communities increases by one order of magnitude during 1 yr, suggesting a high sorption capacity of the newly formed iron mineral phases. Values of (La/Yb)N, Ce, and Y anomalies in the iron oxyhydroxides are consistent with the REE distribution in surface waters accommodating the bacterial communities. The Nd isotope composition of the studied bacterial iron oxyhydroxides inherits the isotopic composition in the ambient water; 143Nd/144Nd values in the bacterial iron minerals vary from 0.511570 to 0.512220; and εNd(0) from –21.8 to –9.2. The maximum proportion of radiogenic Nd is typical for the samples taken from areas marked by the presence of Paleozoic carbonate rocks in Quaternary glaciolacustrine sediments. [ABSTRACT FROM AUTHOR]

Rare Earth Elements (REE), also known as Lanthanides (Ln3+), are a group of 17 elements showing peculiar physical and chemical properties. Unlike technological applications, very little is known about the physiological role and toxicity of Ln3+ on biological systems, in particular on microorganisms (e.g., bacteria), which represent the most abundant domains on our planet. Up to now, very limited studies have been conducted due to Ln3+ precipitation with some anions commonly present in the culture media. Therefore, the development of a minimal medium is essential to allow the study of Ln3+-microbial interactions, limiting considerably the precipitation of insoluble salts. In this regard, a new minimal culture medium capable of solubilizing large amounts of Ln3+ and allowing the growth of different microbial taxa was successfully developed. Assays have shown that the medium is capable of solubilizing Ln3+ up to 100 times more than other common culture media and allowing the growth of 63 bacteria and 5 fungi. The kinetic growth of one yeast and one Gram-positive bacterium has been defined, proving to support superior growth and biomass compared to other commonly used minimal media. Moreover, the sensitivity and uptake/absorption of a Bacillus stratosphericus strain were tested, highlighting its capability to tolerate concentrations up to 10 mM of either Cerium, Gadolinium or Lanthanum and accumulate different quantities of the three. [ABSTRACT FROM AUTHOR]

The Gurvunur apatite-magnetite deposit is located within the Ozerny ore cluster in Western Transbaikalia. A peculiarity of this object is the presence of rare-earth mineralization in the ores. The main REE concentrator minerals include monazite, allanite, apatite, and epidote. One of the main concentrators of REE is apatite, where the content of REE sum reaches 2.6 wt. %. The REE are mainly represented by light lanthanides, with La up to 1.8 wt. % and Ce up to 2.08 wt. % predominating. Monazite-(Ce) is formed in the process of apatite refining, leading to the monazite fine-grained dissemination and veinlets occurring. Epidote is found in nests and vein-like formations of skarn aggregates. The mineral mainly contains light lanthanides (La up to 5.11 wt. %, Ce up to 2.47 wt. %) and forms gradual transitions to allanite that, in its turn, is also found in the form of isolated segregations or as a part of aggregates of epidote-allanite composition. Light lanthanides with Ce up to 14.35 wt. % and La up to 9.16 wt. % predominate in the allanite composition. The study of the mineral composition and distribution of REE in ores and minerals allows us to conclude that rare-earth mineralization in the ores of the Gurvunur apatite-magnetite deposit was formed as a result of skarning of the carbonate-bearing volcanogenic-sedimentary rocks, and the source of rare-earth mineralization was granodiorites of the Vitimkan intrusive suite.

The Fe skarn and vein-type Cu mineralization types are common in the Eastern Taurus Mountains. This study aims to determine the U-Pb geochronology of garnets of varying sizes within the skarn zone developed at the quartz diorite–marble contact zone in Ayazpınar, Pertek District, Tunceli Province, Turkey. Additionally, this study aims to determine the age of the skarnization and the types of inclusion minerals in the garnets. Faulting and magma emplacement along the thrust plane caused mineralization in the Eastern Taurus Mountains, especially at the marble and quartz diorite contact zone between the cities of Elazığ and Tunceli. The greenish garnets found in the Ayazpınar deposit are characteristic of distal skarns, while red or brown Pertek garnets are observed in the proximal skarns. The garnets typically feature a core–rim texture. The cores of the garnet crystals are large, reddish in color, and have a high REE (Ce, Pr) content. Moreover, the cores have higher Fe and lower Al ratios, alongside higher La, Ce, and Pr contents, than the rims. We propose that the compositional differences between the rims and the cores reflect the transition from oxidized REE- and Fe3+-rich liquids to liquids with lower REE and Fe3+ contents, producing the differences in the garnet colors. Green garnets show lower REE contents than brown garnets with Fe-rich cores. The skarn under study includes the following successively formed zones: diorite → epidote skarn → garnet–magnetite → pyrite–garnet–magnetite → calcite carbonate. Diopside, magnetite, and hematite, including small grains, are surrounded or enveloped by garnets. The U-Pb age of the mineralization is 74.1 ± 5 Ma, indicating that the mineralization occurred concurrently with the intrusion settlement. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) have recently been classified as critical and strategic metals due to their importance in modern society. Research on the geochemical behaviors and mineralization of REEs not only provides essential guidance for mineral exploration but also holds great significance in enhancing our understanding of Earth's origin and evolution. This paper reviews recent research on the occurrence characteristics, deposit types, and hydrothermal behaviors of REEs, with a particular focus on comparing the complexation and transport of REEs by F, Cl, S, C, P, OH, and organic ligands in fluids. Due to the very weak hydrolysis of REE ions, they predominantly exist as either hydrated ions or free ions in low-temperature and acidic to weakly basic fluids. As the ligand activity increases, the general order of transporting REEs is Cl− ≈ S O 4 2 − > F− ≈ P O 4 3 − > C O 3 2 − > OH− under acidic conditions or OH− > S O 4 2 − ≈ Cl− > F− under alkaline conditions. In acidic to neutral hydrothermal systems, the transport of REEs is primarily dominated by S O 4 2 − and Cl− ions while the deposition of REEs could be influenced by F−, C O 3 2 − , and P O 4 3 − ions. In neutral to alkaline hydrothermal systems, REEs mainly exist in fluids as hydroxyl complexes or other ligand-bearing hydroxyl complexes. Additionally suggested are further comprehensive investigations that will fill significant gaps in our understanding of mechanisms governing the transport and enrichment of REEs in hydrothermal fluids. [ABSTRACT FROM AUTHOR]

The age and depositional environments of Middle Jurassic terrigenous rocks crowning the Mesozoic section on the northeastern flank of the Nagondzha terrane within the Ulakhan-Sis Ridge are discussed. Based on our finds of retrocerams and the analysis of biostratigraphic data of predecessors, the Bajocian–Middle Bathonian age of these rocks is accepted. Three lithologically different sequences are identified in the section. Sandstones from the lower unit belong to feldspathic litharenites; from the upper sequences, to litharenites dominated by extrabasinal carbonate clastics (calclithites). The analysis of structural-textural features, mineralogical-petrographic composition, and distribution of trace elements in litharenites suggests that all these sequences were deposited in the shelf part of paleobasin associated with an active volcanic island arc, which presumably existed since the Early Jurassic on the Omulevka Craton terrane until the termination of the Kolyma–Omolon superterrane formation. [ABSTRACT FROM AUTHOR]

Micro‐X‐ray fluorescence (XRF) screening of 244 glass sherds from Ribe, Denmark, identified 23 wood ash glasses. The closely dated finds pinpoint the arrival of the earliest wood ash glass produced in Western Europe in this important North Sea trading hub. This glass type was absent among glass from 700 to 790 CE but feature strongly from 790 to 810 CE. Electron microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) analysis of 24 glasses show the presence of four types. We show the strengths of classifying wood ash glass based on the glass‐producing sands and conclude that the earliest production took place on a considerable scale and had a major impact on glass circulation in Northern Europe in the ninth century. [ABSTRACT FROM AUTHOR]

Rare earth elements (REE) can be found in expressive contents in different secondary sources, such as acid mine drainage (AMD). This work evaluated separation of light and heavy rare earth elements (REE) from an acid mine drainage (AMD) generated in a former uranium mine in Brazil by using ion exchange. This AMD presents pH 3.50, total REE content of 97 mg L−1 and 1.3 g L−1 of sulfate and was used in the REE loading experiments. Loading experiments were carried out in columns using a commercial strong acid cation (SAC) exchange resin. Elution was performed with 0.01 mol L−1 NH4EDTA in systems with one, two and three columns. Regarding the loading step, the resin presented a total loading capacity of 0.58 mmol g−1. The resin proved to be more selective for light REE with adsorption efficiency of 78% and 48% for heavy REE. Regarding elution, high efficiencies between 90 and 100% were achieved for REE. The final REE solution is approximately 10 times more concentrated in the liquor related to the acid mine water. Better fractionation results were achieved for the system with three columns. Although the complete separation of the REE into pure elements was not possible, two distinct fractions of heavy and light REE could be obtained, and La was completely separated from the other REE. In order to improve fractionation and separate the REE into individual ones, the concentrated fractions can proceed to subsequent ion exchange systems. [ABSTRACT FROM AUTHOR]

Titanites can be excellent markers of element transfer in medium-temperature retrograde metamorphism. Euhedral titanites from several alpine fissures from Mont Blanc, particularly those of Périades and Courtes, crystallised at the end of the main quartz stage and are synchronous with the formation of green biotites and albite before chlorite formation. Micro-XRF, SEM, electron probe, and LA-ICP-MS analyses show that these titanites have a wide range of Al2O3 content from 1 to 8%, are dominated by -OH versus F, and have a wide range of Nb (up to 4500 ppm), Y (up to 3000 ppm), Zr (up to 1800 ppm), and Sn (up to 1400 ppm) concentrations. The allanite from the granite, partly destabilised into epidote, is the most likely source of Nb, Y, Zr, Sn, and REE. Titanites are enriched in HREE and show variations in LREE depending on the studied sites. Like quartz, they formed at around 400 ± 20 °C, which is compatible with the formation of green biotites after the destabilisation of granite Fe-Mg silicates. This early stage of fluid circulation, synchronous with the Mont Blanc massif uplift, is therefore marked by the titanite formation at the transition between the biotite and chlorite stability fields. [ABSTRACT FROM AUTHOR]