Rare Earth Element Concentrations Research Articles

Soil Improvement after Reclamation of Rare Earth Tailings in Northeast Guangdong, China

In order to explore the soil improvement effect of guest soil reclamation, the main physical and chemical properties of the soil in-situ extracted rare earth tailings after reclamation in Pingyuan County, Meizhou city were tested. Using 5 point sampling method, soil samples were taken from a 0-20 cm soil layer to detect NH4+ residues, pH value, content of organic matter, available N, available K, available P, and heavy metal in the soil. The results were shown that the NH4+ content in the soil decreased from 96.67 to 15.29 (mg·kg−1) after reclamation, the pH value increased from 4.58 to 5.40, and the organic matter increased from 2.12 to 2.75 (g·kg−1). However, the available N, P, and K decreased, and the soil fertility index also decreased from 0.55 to 0.49. The reclamation did not significantly improve soil fertility. The Nemero comprehensive index of non-rare earth heavy metal elements decreased from 0.58 to 0.44, but the pollution of non-rare earth heavy metals in the soil before and after reclamation was at a clean level, and there was no heavy metal pollution. The total RE (rare earth) content in tailings soil, reclaimed soil, and control soil was higher than the soil environmental background value in Guangdong Province. Heavy RE content in tailings soil exceeded 50% of total RE content, while light RE was mainly in the reclaimed soil. The pollution levels of total RE metals in soil before and after reclamation were non-pollution to moderate pollution level and non-pollution level, respectively. The control soil was the most severely polluted, reaching a strong pollution level. The three RE metals, Y, Sm and Ce, accounted for the highest proportion of the total soil REs, and the pollution levels of the latter two elements were above strong pollution in control soil. After 4 years of land reclamation, the NH4+-N pollution, soil acidification, and heavy metal pollution in the soil of tailings could be significantly improved, but the soil fertility was still low and required a long remediation process. In the future reclamation work, in addition to continuing to pay attention to the improvement of soil environment, the improvement of soil fertility and the control of RE pollution should also be strengthened, and when using foreign soil for reclamation and improvement, the quality of foreign soil, especially fertility, should also be considered.

Первые сведения о редкоземельной минерализации в породах вулкана Эсмеральда (Марианская островная дуга)

The results of the study of rare earth mineralization in the rocks composing the Esmeralda underwater volcano located in the southern part of the Mariana island arc are presented. Despite the fact that the composition and structure of the Esmeralda volcano have been studied by various scientists for 75 years, information about the content of rare earth elements in its rocks is sporadic and is given in only six papers, and two of them present only average values. Our micro-level study of the mineral composition of the basaltic andesite, dissected by a crack, dredged during the 5th voyage of the research vessel «Vulcanologist» in 1978, made it possible for the first time for the Esmeralda volcano to establish the presence of rare earth minerals in its rocks, to determine their composition and formation conditions. The minerals were found to be localized in open crack zones and gas vacuoles.

Mechanical Activation as a Stage of Coal Sample Preparation in the Analysis of Rare Earth Elements Content by Inductively Coupled Plasma Mass Spectrometry

Background: Brown coals are recognized as promising sources of rare earth elements (REEs). Rare earths are present in both the mineral and organic parts of brown coal. Objectives: This study was conducted to investigate the influence of preliminary mechanical activation in the process of sample preparation prior to analyzing the concentrations of rare earth elements in brown coal samples of various origins and compositions Methods: Four coal samples from different deposits in Russia were selected for the study. Samples were treated with mechanical activation, without reagents, or mechanochemical activation, with humic acids added externally as reagents. X-ray phase analysis was carried out with the selected samples. The quantities of rare-earth elements present in the samples were studied by the method of high-sensitivity inductively coupled plasma mass spectrometry (ICP-MS). Results: It was found that the mechanical activation of coal before dissolution in a mixture of nitric and hydrofluoric acids leads to an increase in the determined concentration of rare earth elements. For this study, the expediency of using only nitric acid as an optimal solvent for the elemental analysis of coal samples was shown. The total concentration of all REE after dissolution of nitric acid and mechanochemical activation with humic acid reached 2456 g/t in Vanchin coal, 968 g/t in Azeysky coal, and 24 g/t and 150 g/t in Itatsky and Spetsugli coals, respectively. Conclusion: Mechanical activation and mechanochemical treatment can greatly help to facilitate sample preparation of natural objects, such as coals for elemental analysis, but in some cases, only a change of solvent is sufficient. When developing technology for concentrating rare earth elements from coal involving grinding, it is necessary to take into account the fact that mechanical activation of coal changes its tendency to dissolve, which may affect the results of the analysis and should be taken into account during experiments.

Geochemistry of lanthanides in thermal waters of Issyk-Kul Lake Basin

The distribution and abundance of lanthanides in thermal waters of the northern Tien Shan (Issyk-Kul lake basin) were studied. Waters are represented by three types: Na-Cl-SO4-HCO3, Na-Ca-Cl-SO4 and Na-Ca-Cl, demonstrates alkaline pH (7.3–9.7) and Eh from -260 to +98 mV. Discharge temperature varies from 15 to 50oC, and total dissolved solids from 0.2 to 13.0 g/l. It is established that lanthanides (or rare earth elements, REE) concentrations vary from 0.07 to 0.81 ppb, the maximal concentrations relate to a Na-Ca-Cl water type, which demonstrates the influence of reverse ion exchange. The total concentration of rare earth elements roughly increases as pH decreases, implying that the absolute abundance of REE is totally controlled by pH conditions. The ΣREE concentrations in groundwater exhibit a high positive correlation (R=0.8) with the total dissolved solids contents indicating that ΣREE are well related to the salinity of the thermal water samples. The major ions HCO3, SO4, Ca, K, and Mg have minor associations with REE. The geochemical and geological data suggest that the principal REE source of the thermal waters is bedrock mineralogy and lithology. The distribution and abundance of REE in thermal waters of Issyk-Kul basin were studied for the first time.

Mafic Alkaline Magmatism and Rare Earth Element Mineralization in the Mojave Desert, California: The Bobcat Hills Connection to Mountain Pass

AbstractOccurrences of alkaline and carbonatite rocks with high concentrations of rare earth elements (REE) are a defining feature of Precambrian geology in the Mojave Desert of southeastern California. The most economically important occurrence is the carbonatite stock at Mountain Pass, which constitutes the largest REE deposit in the United States. A central scientific goal is to understand the genesis of the carbonatite ore body in the context of widespread REE‐rich igneous activity. A swarm of mafic alkaline (shonkinite) dikes has been mapped and sampled at Bobcat Hills, 65 km southeast of the Mountain Pass mine. Whole‐rock geochemistry and zircon geochronology demonstrate a clear affinity to the ca. 1.4 Ga Mountain Pass intrusive system. Bobcat Hills dikes have comparably high REE concentrations (La ∼1,000× chondritic) and an error‐weighted mean 207Pb/206Pb zircon crystallization age of 1,426 ± 2 Ma (2σ). Unlike the alkaline intrusions at Mountain Pass, which have abundant inherited zircon from Paleoproterozoic basement rocks and crustally influenced oxygen isotope compositions (δ18Ozircon = 6.5–7.5‰), the Bobcat Hills dikes lack any evidence of crustal assimilation and have oxygen isotope values that overlap a mantle range (Bobcat Hills average δ18Ozircon = 5.6 ± 0.3‰). The dikes were a high‐temperature, early center of mafic alkaline magmatism in the Mojave Desert that serve as a snapshot of melt generation from a spatially extensive, metasomatized mantle source. We propose that modification of the crust over many tens of Myr at Mountain Pass created an environment that favored crustal assimilation and enabled ascent of late‐stage, REE‐rich carbonatite magmas.

Predicting rare earth elements concentration in coal ashes with multi-task neural networks.

The increasing demand for rare earth elements (REEs) makes them a scarce strategic resource for technical developments. In that regard, harvesting REEs from coal ashes-a waste byproduct from coal power plants-offers an alternative solution to conventional ore-based extraction. However, this approach is bottlenecked by our ability to screen coal ashes bearing large concentrations of REEs from feedstocks-since measuring the REE content in ashes is a time-consuming and costly task requiring advanced analytical tools. Here, we propose a machine learning approach to predict the REE contents based on the bulk composition of coal ashes, easily measurable under the routine testing protocol. We introduce a multi-task neural network that simultaneously predicts the contents of different REEs. Compared to the single-task model, this model exhibits notably improved accuracy and reduced sensitivity to noise. Further model analyses reveal key data patterns for screening coal ashes with high REE concentrations. Additionally, we showcase the utilization of transfer learning to improve the adaptability of our model to coal ashes from a distinct source.

Validation of microwave acid digestion, diffusive gradients in thin-film preconcentration and inductively coupled plasma optical emission spectrometry methodology for the determination of REEs in natural zeolites.

The determination of rare earth element (REE) content in different natural minerals is of high interest due to their extensive use in modern and sustainable technologies. The REEs occurring in natural zeolites are specific to each deposit. This study presents the validation and evaluation of the measurement uncertainty for the determination of REEs (Ce, Dy, Er, Eu, Gd, La, Lu, Nd, Pr, Sm, Y, and Yb) in natural zeolites using microwave-assisted acid digestion and inductively coupled plasma optical emission spectrometry (ICP-OES) after diffusive gradients in thin-film preconcentration. A mixture of HNO3 : HCl : HF of 3 : 9 : 2 (v/v/v) and microwave digestion provided suitable recoveries for the analysis of two certified reference materials, CRM BCS-CRM 375/1 and CRM OREAS 460. Good linearity over the calibration range of 0-2 μg mL-1, with correlation coefficients of 0.9995-1.0000, was obtained for each REE by ICP-OES. The limits of quantification (LOQS), calculated considering the instrumental LOQs and the sample preparation by microwave digestion, were in the range of 0.20-0.60 mg kg-1. A supplementary step of preconcentration/matrix separation based on the passive sampling by diffusive gradients in thin-films (DGT) technique improved the LOQs by about 20 times after three days of passive accumulation, allowing the measurement of the concentrations of all studied REEs in natural zeolite samples. The proposed methodology is a suitable approach for the measurement of REEs at low concentrations in natural zeolite samples by ICP-OES, and it can be extended to other geological samples. The measurement uncertainty was calculated based on the validation data. The proposed method provides reliable results for the measurement of REEs in natural zeolites and was used to measure the specific concentrations of REEs in natural zeolite samples from three Romanian quarries. The REE concentration can be used as a fingerprint for each deposit.

Investigating the effect of synthesis parameters on the structure and upconversion luminescent properties of NaYF4:Tm,Yb for anticounterfeiting printing ink

Introduction: In this study, NaYF4:Tm,Yb upconversion microparticles were prepared by a hydrothermal method. Methods: The effects of fabrication parameters such as rare earth concentration, reaction temperature and reaction time on the structure and luminescence properties of the materials were studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). Depending on the reaction temperature and time, the morphology of NaYF4:Tm,Yb is either a nanoparticle or a branched structure. Results: The crystallite size is approximately 70 nm and remains almost unchanged with increasing reaction temperature and time. These NaYF4:Tm,Yb powders strongly emit at 450 nm and 798 nm. In addition, the surface of the UCMPs was also modified with maleic anhydride to improve their dispersibility in solvents and binding to biological molecules. Conclusion: Printing ink based on UCMPs modified with maleic anhydride and polyamide for screen printing was prepared. The printed patterns on paper and polymer substrates glow blue light under LED excitation at 980 nm, and they are completely transparent in daylight.

Dual second harmonic generation and up-conversion photoluminescence emission in highly-optimized LiNbO3 nanocrystals doped and co-doped with Er3+ and Yb3.

Preparation from the aqueous alkoxide route of doped and co-doped lithium niobate nanocrystals with Er3+ and Yb3+ ions, and detailed investigations of their optical properties are presented in this comprehensive work. Simultaneous emission under femtosecond laser excitation of second harmonic generation (SHG) and up-conversion photoluminescence (UC-PL) is studied from colloidal suspensions according to the lanthanide ion contents. Special attention has been paid to produce phase pure nanocrystals of constant size (∼20 nm) thus allowing a straightforward comparison and optimization of the Er content for increasing the green UC-PL signals under 800 nm excitation. An optimal molar concentration at about 4 molar% in erbium ions is demonstrated, that is well above the concentration usually achieved in bulk crystals. Similarly, for co-doped LiNbO3 nanocrystals, different lanthanide concentrations and Yb/Er content ratios are tested allowing optimization of the green and red up-conversion excited at 980 nm, and analysis of the underlying mechanisms from excitation spectra. All together, these findings provide valuable insights into the wet-chemical synthesis and potential of doped and co-doped LiNbO3 nanocrystals for advanced applications, combining both SHG and UC-PL emissions from the particle core.

Role of indigenous microbial communities in the mobilization of potentially toxic elements and rare-earth elements from alkaline mine waste

This study aims to evaluate the role of indigenous microorganisms in the mobilization of potentially toxic elements (PTE) and rare-earth elements (REE), the influence of the bioavailability of carbon sources that might boost microbial leaching, and the generation of neutral/alkaline mine drainage from alkaline tailings. These tailings, with significant concentrations of total organic carbon (TOC), were mainly colonized by bacteria belonging to the genera Sphingomonas, Novosphingobium and Solirubrobacter, and fungi of the genera Alternaria, Sarocladium and Aspergillus. Functionality analysis suggests the capability of these microorganisms to leach PTE and REE. Bio-/leaching tests confirmed the generation of neutral mine drainage, the influence of organic substrate, and the leaching of higher concentrations of PTE and REE due to the production of organic acids and siderophores by indigenous microorganisms. In addition, this study offers some insights into a sustainable alternative for reprocessing PMC alkaline tailings to recover REE.

Effects of CeO2/Y2O3 rare earth oxides on microstructure and properties of in-situ synthesized WC-reinforced Ni-based cladding layer

A novel tungsten carbide (WC)-reinforced nickel (Ni)-based laser cladding layer was prepared through an in-situ synthesis process. The influence of different concentrations of CeO2/Y2O3 on the microstructure, wear, and corrosion resistance of the in-situ synthesized WC-reinforced Ni-based cladding layer was analyzed. The results revealed that the coatings doped with rare-earth oxides exhibited good micro-hardness (660 HV0.2) and wear resistance when the rare-earth oxide content reached 0.75% CeO2 and 1.50% Y2O3. Additionally, the minimum corrosion rates of the coating were measured at 0.002770 mm/a and 0.0022548 mm/a at 1.5% CeO2 and 1.5 Y2O3 doping, with noble Ecorr values ranging from -0.12549 V to -0.49924 V and lower Icorr values ranging from 2.3550?10-7 A?cm2 to 1.9170?10-7 A?cm2. Furthermore, the wear resistance of the cladding layer was significantly higher than that of the substrate. Both the cladding layer and the substrate exhibited a mixed-wear mode, and they exhibit adhesive wear in wet friction environments.

Rare Earth Element Characteristics of Shales from Wufeng-Longmaxi Formations in Deep-Buried Areas of the Northern Sichuan Basin, Southern China: Implications for Provenance, Depositional Conditions, and Paleoclimate.

To explore the sedimentary environment and the background of the source area of organic-rich shales in the Wufeng-Longmaxi Formations in the northern Sichuan Basin, samples from Well XX1 in the area were subjected to geochemical testing and analysis of organic carbon content, trace elements, and rare earth elements (REEs). The results show that the total content of REE (ΣREE) of the shale in the Wufeng-Longmaxi Formations varied from 183.08 to 234.66 μg/g with an average of 212.59 μg/g, which is significantly higher than the content of the North American shale composite. The fluctuations in the total amount of REEs in the shale of the Wufeng-Longmaxi Formations reflect certain differences in the geochemical conditions of the Upper Ordovician-Lower Silurian shale. The ratios of LREE/HREE, LaN/YbN, LaN/SmN, and GdN/YbN and the distribution of normalized REE patterns indicate that the source supply or sedimentary structural background may have changed during the shale deposition period of the Wufeng Formation, while the shale deposition period of the Longmaxi Formation may be in a relatively stable source supply and sedimentary structural background. There is no significant correlation between δCe and ΣREE, and the obviously negative Eu abnormity and the weak Ce abnormity indicated that the diagenesis had a limited impact on REEs. Geochemical parameters such as values of ∑REE, δEu, δCe, Ceanom, and LaN/YbN indicate that the climate during the Wufeng-Longmaxi Formation shale deposition period was warm and humid, and the shale was deposited mainly in the suboxic-anoxic water environment. The deposition rate was stable and slow, providing good conditions for the production and preservation of organic matter. At the same time, this shows that the water environment of Wufeng Formation is more anoxic and reductive than that of Longmaxi Formation, which is more conducive to the preservation of organic matter. The correlation between ΣREE and the content of Sc, Ti, Cr, Co, Zr, Nb, Th, Hf, Ta, and other elements indicates that the sources of REEs in the shale of Wufeng and Longmaxi Formations in the study area are similar, mainly terrestrial clasts, and some may come from the sea. The REE distribution pattern shows that the shale provenance of the Wufeng-Longmaxi Formations mainly comes from the upper crust. The La/Yb-∑REE diagram shows that the sediment-parent rocks are mainly early sedimentary rocks and these sediment-parent rocks have granite provenance characteristics. Compared to La/Yb, LREE/HREE, LaN/YbN, and other REE characteristic parameters, it is inferred that the tectonic background of the study area is dominated by passive continental margin.

Geochemical Study of Rare Earth Elements (REE) Distribution in Jeli, Kelantan, Malaysia: Correlation between Physical Appearance and Geochemical Composition

The application of rare earth elements (REE) in green technology has been rapidly expanded worldwide and demand for REE increased accordingly. Most REEs are mined from ion adsorption clay (IAC) which is claimed can be easily extracted and environmentally safe. REE was released within the soil profile and absorbed on the surfaces of the clay minerals. The aim of the study is to correlate the physical appearance and geochemical composition of REE in soil of Jeli, Kelantan. Petrography and geochemical methods were used to identify the characteristics of IAC samples that have been collected. According to the petrography, REE-bearing minerals such as monazite can be identified in sample JL17 which represents bedrock of granite found in Ayer Lanas. Elemental analysis and mineral identification in soil samples were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD) proving the samples are from clay association. Based on Inductively Coupled Plasma Mass Spectrometry (ICPMS) analysis, JL17, JL2 and JL19 contain high REE concentration ranged from 8000 to 200 ppm. Both samples have shared almost similar physical appearance in terms of reddish colour and fine-grain sized.

Influence mechanism of rare earth (RE) on inclusion modification in non-oriented silicon steel

Effects of rare earth (La+Ce) on inclusions in hot-rolled band of 3.0∼3.3%Si-0.8∼1.0%Al non-oriented silicon steel was studied using industrial trials, scanning electron microscope (SEM) and thermodynamic analysis. Furthermore, combining Heterogeneous Nucleation Theory with Edge-to-Edge Matching (E2EM) model, the formation mechanism of complex inclusions was also investigated. Rare earth (La+Ce) would promote the spheroidization and coarsening of inclusions, and then transform into regular and near circle morphology composite inclusions of rare earth. The low content of rare earth (21 ppm) mainly deoxidized and modified Al2O3 inclusions, and formed (La,Ce)AlO3 inclusions. Increasing of rare earth (29–45 ppm) would promote the formation of (La,Ce)AlO3-(La,Ce)2O2S and (La,Ce)2O2S inclusions, reduce the sulfide precipitation, and promote a gradual transformation of the core of composite inclusions from (La,Ce)AlO3 to (La,Ce)AlO3-(La,Ce)2O2S and (La,Ce)2O2S, which agreed well with the thermodynamic analysis. However, rare earth (29–45 ppm) had a weak metamorphic effect on Al2O3 inclusions generated by temperature drop and secondary oxidation. LaAlO3, CeAlO3, La2O2S and Ce2O2S could be the heterogeneous nucleation core of AlN, Al2O3, MgO-Al2O3, typical composite inclusions with (La,Ce)AlO3 and (La,Ce)2O2S as the core would ultimately form.

Reducing rare earth loss by adding acetic acid in the aluminum removal process of rare earth leaching solution

The ionic-type rare earth ore, abundant in medium and heavy rare earth elements, is a strategic mineral resource. The removal of aluminum from ionic rare earth leaching solution results in over 8% loss of rare earths. Preliminary research has found that adding acetic acid (HAc) during aluminum removal process can effectively reduce the loss of rare earth elements. In this paper, through the calculation of the species distribution in the La2(SO4)3-Al2(SO4)3-HAc-H2O system, it is found that HAc forms an AlOH-Ac+ complex with aluminum ions, with a proportion of up to 70%, which will increase the initial precipitation pH of aluminum hydroxide. Furthermore, HAc and lanthanum form a LaAc2+ complex, and the proportion can reach more than 20%. Moreover, the zeta potential, FT-IR, and XPS tests of aluminum hydroxide, obtained by neutralization precipitation, revealed that the complexation of HAc and aluminum can reduce the precipitation rate of aluminum hydroxide, so that its particle size increases, the specific surface area decreases, and the van der Waals force adsorption sites are reduced. HAc can be chemically adsorbed on aluminum hydroxide, thereby increasing the zeta potential of aluminum hydroxide and ultimately reducing its electrostatic adsorption effect on rare earths. Additionally, the complexation of HAc and rare earth elements can reduce the local supersaturation of rare earth hydroxides and decline the coprecipitation of rare earth elements. Finally, under a precipitation endpoint pH of 5.2, HAc concentration of 0.006 mol/L, aluminum concentration of 0.2 g/L, rare earth concentration of 0.8 g/L, magnesium ion concentration of 0.5 g/L and magnesium oxide slurry concentration of 0.45 mol/L, the aluminum removal efficiency obtained with rare earth leaching solution reached 98.47%, and the rare earth loss efficiency was 2.62%. Compared with the control, the rare earth loss efficiency was reduced by 5.59%. This paper provides guidance for the efficient and green development of ionic-type rare earth ore.

NaGdF4:Yb, Er, Tm Upconversion Nanoparticles for Bioimaging in Shortwave-Infrared Range: Study of Energy Transfer Processes and Composition Optimization

Upconversion nanoparticles are promising for many applications. For triple-doped nanoparticles (NPs), the luminescence intensity shows a non-linear dependence on the rare-earth ion concentration, making it difficult to obtain bright phosphors with high energy output. We investigated the energy transfer processes in β-NaGdF4:Yb-Er-Tm NPs and considered strategies for increasing the thulium luminescence intensity, in particular, the use of core–shell structures. The luminescence spectra were analyzed in the short-wavelength infrared (SWIR) and visible (VIS) regions. The Er3+ and Tm3+ luminescence lifetimes in the VIS region were measured to study the energy transfer processes between the active ions. The quenching of the Tm3+ luminescence in the SWIR region was observed. However, both Er3+ and Tm3+ luminescence bands were observed in the VIS range. We attribute these effects to energy transfer between Tm3+ 3F4 → 3H6 and Er3+ 4I13/2 → 4I9/2, which occurs due to overlap of Er3+ and Tm3+ luminescence bands, and also to competition between Er3+ and Tm3+ for energy transfer from Yb3+. For core–shell NPs, when Tm3+ and Er3+ are separated into adjacent layers, quenching cannot be avoided, likely due to the mutual diffusion of ions during shell synthesis. The most optimal strategy to obtain luminescence in the SWIR range is to use an inert intermediate shell between the layers containing Tm3+ and Er3+.

Impact of Rare Earth Elements on CaCO3 Crystallization: Insights into Kinetics, Mechanisms, and Crystal Morphology.

This study investigated the crystallization kinetics and mechanisms of calcium carbonate (CaCO3) in the presence of rare earth elements (REEs) including lanthanum (La), neodymium (Nd), and dysprosium (Dy). Through a comprehensive approach utilizing UV-vis spectrophotometry, powder X-ray diffraction, and high-resolution electron microscopy, we examined the effects of REEs on CaCO3 growth from solution at varying concentrations and combinations of REEs. Our findings highlight that even trace amounts of REEs significantly decelerate the rate of CaCO3 crystallization, also leading to alterations in crystal morphology and mechanisms of growth. The impact of REEs becomes more pronounced at higher concentrations and atomic mass, although the potential formation of poorly ordered REEs carbonate precursor phases can result in a decrease in the REE3+/Ca2+ ratio, influencing the crystallization rate of CaCO3. Vaterite and calcite were identified as the main crystallized polymorphs, with vaterite exhibiting distinct growth defects and calcite developing complex morphologies at higher REEs concentrations and an internal architecture suggesting a nonclassical growth route. We propose that REEs ions selectively adsorb onto different calcite surfaces, impeding growth on specific sites and resulting in intricate morphologies.

From the cellular to tissue alterations induced by two rare earth elements in the mussel species Mytilus galloprovincialis: Comparison between exposure and recovery periods

The global effort to achieve carbon neutrality has led to an increased demand for renewable energy technologies and their raw materials, namely rare earth elements (REEs). These elements possess unique properties and are used in various applications. However, the increased use of REE-based technologies has resulted in higher amounts of electronic waste, leading to elevated REEs concentrations found in the aquatic environment, with poorly understood threats to wildlife. Praseodymium (Pr) and europium (Eu) are two REEs that, despite their potential environmental risks, have almost unknown effects on aquatic organisms. Therefore, the present study aimed to assess the impacts of different concentrations of Pr and Eu (0, 10, 20, 40, and 80 μg/L) in the mussel species Mytilus galloprovincialis, as well as their ability to recover from exposure to the highest concentration. Mussels accumulated both elements in a dose-dependent manner, with the accumulation of Pr being higher. Accompanying the increase of metabolism, mussels exposed to Pr not only enhanced the activity of the antioxidant enzymes superoxide dismutase (up to 40 μg/L) and glutathione reductase (at 80 μg/L) but also the activity of the biotransformation enzymes carboxylesterases (CbE's) and glutathione S-transferases (GSTs) (at 80 μg/L). Nevertheless, these defence mechanisms were not sufficient to prevent cellular damage. All the Eu concentrations induced cellular damage, despite an increase in the activity of biotransformation enzymes (CbE's and GSTs) in mussel tissue. According to the histopathology assessment, mussels were not able to recover after exposure to both elements and lower concentrations induced higher injuries in digestive tubules. This study highlights that exposure to Pr and Eu had adverse effects on M. galloprovincialis, even at the lowest tested concentration, which may eventually impact mussels' growth, reproductive capacity, and survival.

Hydrothermal monazite and xenotime chemistry as genetic discriminators for intrusion-related and orogenic gold deposits: implications for an orogenic origin of the Pogo gold deposit, Alaska

Attempts to geochemically distinguish between metamorphic-hydrothermal systems that form orogenic gold deposits and both reduced and oxidized magmatic-hydrothermal systems using isotopes or metal associations have proven ambiguous, particularly for orogenic gold and reduced intrusion-related gold systems. The absence of conclusive geochemical discriminators and the overlap in geologic characteristics have led to gold deposit models being potentially incorrectly applied, which in turn negatively affect regional mineral exploration and mine planning. In this study, in situ electron microprobe geochemical analyses of hydrothermal monazite and xenotime crystals associated with different types of gold-bearing deposits are shown to be effective geochemical discriminators. There are notable differences in mineral chemistry such as rare earth element (REE) profiles, total light REE, Dy, Er, Pr, Y, Nd/Sm, and La/Sm that distinguish monazite precipitated from metamorphic-hydrothermal fluids that form orogenic gold deposits and those precipitated from magmatic-hydrothermal fluids that form both porphyry Cu-Mo-Au and reduced intrusion-related gold deposits. Notable differences in overall xenotime abundances and concentrations of heavy REEs, Ca, and Sc are distinctive between the different deposit classes for xenotime. The origin of the controversially classified Pogo gold deposit, Tintina gold province, Alaska, which has been characterized as both a reduced intrusion-related and an orogenic gold deposit, is tested based upon the noted chemical differences associated with these hydrothermal phosphates. The findings of this study have implications for exploration and mine development in the Tintina gold province and other areas that contain deposits that are controversially classified as either orogenic or as magmatic-hydrothermal gold deposits.

Mineralogy and Geochemical Characteristics of Scheelite Deposit at Xuebaoding in Pingwu, Sichuan Province, China

Featuring subtle lithological alterations in the host rocks and containing colossal gemstone crystals, the scheelite deposit at Xuebaoding in the Pingwu region of Sichuan Province exhibits characteristics typical of a vein-like hydrothermal-type deposit. The scheelite from the Xuebaoding region is renowned for its high saturation of color, perfect crystal shape, and pure color. In this study, its crystal structure and mineralogical, geochemical, and in situ Sr-Nd isotope characteristics are all systematically characterized. Our objective is to determine the source of ore-forming materials, the timing of the mineralization, and the chemical composition of scheelite, including major elements, trace elements, and rare earths elements (REE). The scheelite samples were analyzed with a variety of methods such as polarizing microscopy, X-ray powder diffraction (XRD), X-ray fluorescence spectrometry (XRF), electron probing, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In addition, conventional gemological tests were performed using instruments including gemstone microscopes, GI-UVB ultraviolet fluorescent lamps, grating spectroscopy, etc. The results demonstrate that scheelite exhibits a high refractive index, excellent crystallinity, and a granular structure. Clear color bands and ring structures are observed within the minerals, accompanied by interference colors of light blue, blue, and yellow. Additionally, the mineral components are relatively concentrated, with muscovite and illite serving as accessory minerals. Furthermore, the chemical composition of scheelite reveals a WO3/CaO mass ratio that approaches or exceeds the ideal value. Moreover, it exhibits a wide range of variations in total rare earth element (∑REE) content, which is characterized by an enrichment of light rare earths (LREE), significant negative Eu anomalies, and insignificant Ce anomalies. In addition, the metallogenic formation of scheelite can be estimated to have occurred during the Toarcian stage in the Lower Jurassic Epoch period, approximately 183 Ma. The study further revealed that A-type granite serves as the genesis type of scheelite, with most of the ore-forming materials originating from the upper crust and a few derived from younger crustal sources.