Mineral Composition Research Articles

Seeds of Hyoscyamus muticus L. subsp. falezlez: Morpho-Anatomical Features, Phytochemical Investigation and Evidence for Antioxidant Activities.

This work aims to describe the morpho-anatomy and determine the mineral composition of H. muticus L. subsp. falezlez seed, and investigate the influence of extraction solvents (hexane, petroleum ether, chloroform and methanol) on contents of total phenolic (TPC) and flavonoid (TFC) and the antioxidant activity (DPPH, ABTS, reducing power and phenanthroline). The mineral content analysis revealed the presence of different elements. The results indicated that the seed extract obtained by methanol exhibited the highest yield and TPC (82.07 % and 27.14±2.2 μg GAE/mg), while the chloroform extract had the maximum TFC (24.63±0.4 μg QE/mg). In addition, all seed extracts showed excellent performances on DPPH scavenging activity. However, methanolic extract was the most effective extraction solvent for scavenging ABTS free radicals (IC50<12.5 μg/mL). Chloroform and petroleum ether extracts were the most potent in phenanthroline activity. GC-MS analysis identified 28 phytochemical compounds in all extracts and 16 compounds were identified by HPLC/DAD analysis of the methanolic extract. The multivariate analysis results highlighted the influence of solvents on the phenolic composition and antioxidant activity of seed extracts. The results suggest that H. muticus L. seeds can be a promising source enriched with bioactive constituents for application in the pharmaceutical industry.

Effect of different types of fine aggregates on fatigue resistance and self-healing of fine aggregate asphalt matrices

Fatigue cracking is one of the most common types of distress in asphalt pavements. Each asphalt concrete (AC) constituent and its interactions are relevant to characterize the resistance to fatigue cracking of the ACs. Also, for the selection of materials, it is essential to consider not only the capacity of the material resist to fatigue cracking but also its ability to heal. Materials owning self-heal properties can enlarge the ACs fatigue life. Many former studies investigated the self-healing of bituminous materials at the binder level. However, this material property can be dependent on the binder-aggregate interactions. Thus, the current work aims to evaluate the influence of using different fine aggregates on the fatigue cracking resistance and self-healing capacity behavior of fine aggregate matrices (FAMs). First, granite, basalt, and mica schist aggregates were subjected to physical, morphological, and mineralogical characterization. Then, three FAMs were fabricated with the same asphalt binder and these different fine aggregates. To evaluate the fatigue cracking resistance and self-healing capacity of the FAMs, frequency sweep and time sweep tests were conducted. The simplified viscoelastic continuum damage (S-VECD) theory was used to interpret the results of those tests. The mineral composition of the aggregates impacted the stiffness and the fatigue life of the FAMs. However, there was no significant influence of the aggregates on the self-healing capacity of the FAMs, since there was no significant increase in the fatigue life of the materials after the resting periods in the time sweep tests.

SYNTHESES AND CHARACTERISTICS OF CALCIUM-BASED GEOPOLYMER FROM SOLAR-CELL PANEL-GLASS WASTE BY HYDROTHERMAL METHOD

A calcium-based geopolymer was synthesized using a blend of recycled glass powder from solar panels (PV glass waste), limestone, and a sodium silicate solution, which underwent hydrothermal autoclaving at 180 °C for varying durations. This material is regarded as environmentally friendly and has garnered research attention worldwide. In this investigation, limestone served as the calcium source, while recycled glass from solar panels provided the SiO2 necessary for producing calcium-based geopolymer materials. Currently, solar-panel waste poses a significant environmental challenge that requires attention. The objective of this research was to develop a sustainable and high-performance calcium-based geopolymer using waste materials, specifically recycled glass from solar panels and limestone. The study aimed to evaluate the effects of hydrothermal autoclaving on the compressive strength, volume weight, porosity, and water absorption of the synthesized geopolymer, as well as to understand the microstructural transformations involved. The results revealed a remarkable 430 % increase in the compressive strength of the specimens following hydrothermal autoclaving for 24 to 96 hours compared to the unautoclaved samples. Concurrently, the volumetric weight had a substantial rise from 1.54 % to 2.31 g/cm3, with corresponding decreases in the porosity and water absorption from 38.1 % to 16.9 % and 10.26 % to 5.08 %, respectively. An X-ray diffraction (XRD) analysis of the mineral composition and a scanning electron microscope (SEM) examination of the microstructure demonstrated a transformation of all samples from an amorphous gel structure to needle- or spike-shaped fibrous, and then sheet-like CSH structures. These new structures exhibited dimensions of less than 10 µm in length, less than 2 µm in width, and less than 400 nm in thickness. The resulting CSH products constitute calcium silicate hydrate minerals, characteristic of calcium silicate materials, which are synthetic products arising from chemical reactions among SiO2, CaO, and H2O under hydrothermal conditions. This study underscores the potential of using recycled materials to produced high-strength geopolymers, offering a promising solution to the environmental challenge of solar-panel waste.

Pore evolution modeling in natural lacustrine shale influenced by mineral composition: Implications for shale oil exploration and CO2 storage

Pore evolution modeling in natural lacustrine shale influenced by mineral composition: Implications for shale oil exploration and CO2 storage

Exploring the potential of wild leafy vegetables widespread in European Alps as functional food

Wild leafy vegetables, historically vital for Alpine biodiversity and nutrition during hardship, are regaining importance due to the demand for healthy and sustainable food. This study evaluated mineral and phytochemical compositions of eight species: Achillea millefolium, Alchemilla xanthochlora, Bistorta officinalis, Blitum bonus-henricus, Phyteuma betonicifolium, Plantago lanceolata, Silene vulgaris, Taraxacum sect. Taraxacum. Total trace element concentrations ranged from 26 mg kg−1 (T. officinalis) to 92 mg kg−1 (B. officinalis), and potential toxic elements were below legal limits. The sum of the phenolic compounds analysed ranged from 155.30 mg GAE 100 g−1 FW (A. millefolium) to 1200.38 mg GAE 100 g−1 FW (A. xanthochlora). Flavanols were the most abundant phenolic class, but cinnamic acids, flavonols, benzoic acids and vitamin C also showed high values in the analysed species, contributing to high antioxidant activity (from 0.59 μmol TE g−1 FW in A. millefolium to 149.39 μmol TE g−1 FW in A. xanthochlora for DPPH). Overall, A. xanthochlora stood out for its richness in phenolic compounds. These findings underscore wild vegetables potential as functional foods, offering bioactive compounds comparable to or exceeding cultivated plants. Emphasizing preservation of traditional diets and rural innovation, this research supports the integration of wild leafy vegetables into contemporary nutrition strategies.

Audio magnetotelluric view of the giant carbonatite-hosted Bayan Obo REE deposit, Inner Mongolia, northern China

As critical minerals in low-carbon economies, rare-earth elements (REEs) are crucial for modern industry, technology, and medicine. The largest known REE resource in the world is the Bayan Obo (BO) deposit in northern China. However, BO features as complicated mineral compositions and has experienced several geological events. As a reuslt, controversy remains about the BO REE genesis and enrichment mechanism, and debates are also ongoing about the controlling structure of this giant deposit. We carried out an multiscale electromagnetism study on BO mineral deposits. The multiscale study consists a microscale on samples, a small scale targeting mineral deposits and a mid scale concerning the mine field. The small and mid scale study were conducted using audio-magnetotelluric (AMT). This study revealed the controlling structure using geoelectrical characteristics. AMT data were acquired from more than 590 stations, and the petro-electromagnetism of several samples was analyzed to understand the geoelectrical features of the ore deposits and their surrounding rocks. The data were interpreted using Bostick transformation and generalized least-squares inversions. We obtained the geoelectrical structure of the BO complex down to a maximum depth of 3500 m, and we present two-dimensional imaging based on the AMT conversion results. The results show that the BO deposit developed at the transition of the high- and low-resistivity geoelectrical structure from south to north. Our AMT results indicate that the tectonic setting of the BO deposit is the transition zone between the rift edge and craton margin slope. The ore geology is presently controlled by the complex slope and the rift remnant, the ore-bearing dolostone in the profiles is Y-shaped. It goes downward from south to north and potentially features a great mineral prospect deep in the BO deposit.

Applicability of Na/K geothermometer to the metapelitic non-volcanic geothermal fields in the Taiwan orogenic belt

Taiwan is situated at one of the world's most active orogenic belts with arc-continent collision. This event resulted in the burial and uplift of mudstones along the continental margin, transforming them into metapelitic mountains. These mountains intercept rainfall and serve as the driving force for deep water circulation, enabling meteoric fluids to carry residual heat to the surface, thus giving rise to hot springs. The Taiwan orogenic belt is home to over 100 hot springs, and some of the hot spring reservoir temperatures such as Chingshui, Tuchang-Jentse, Lushan, Chihpon, and Chinlun exceeds 160 °C. Geothermal development in Taiwan has been carried out in such hot spring areas without any volcanic activities.In order to assess reservoir temperatures and confirm the applicability of the Na/K geothermometer to such high temperature hot spring system, the concentrations of Na+, K+, and SiO2 were analyzed from geothermal wells. Considering the mineral composition of metapelitic host rock, a new Na/K geothermometer is proposed based on equilibrium between albite and illite:T>180∘C,T(∘C)=2474log(NaK)+3.73−273.15This formula is only applicable in a reducing fluid and does not involve the formation of clay minerals except illite. It also requires several years to reach equilibrium. When using this formula to estimate reservoir temperatures, careful consideration of various conditions is necessary. It is advisable to incorporate both quartz geothermometer and down-hole temperature measurements for a more accurate assessment. Combining the Na/K geothermometer with the quartz geothermometer, along with other geochemical data such as Cl−concentrations and δD and δ18O of fluid, helps to understand whether hydrothermal fluids have undergone evaporation, dilution, and/or mixing processes.

Improving the accuracy of density logging results considering mineral composition for evaluation of high-level radioactive waste disposal sites

ABSTRACT Site selection and characterisation are key factors influencing the safe, stable disposal of spent nuclear fuel. Site selection can be based on geophysical surveys, and geophysical well logging is performed at the detailed survey stage. Typically, gamma – gamma density logging is conducted to continuously obtain in situ density information regarding the well depth. However, gamma – gamma density logging is often influenced by the geological characteristics of the site. The ratio of atomic number to atomic weight is required to convert the electron density obtained through density logging counts into bulk density. Because it is difficult to calculate these ratios for the entire depth, an equation based on water-filled limestone is typically used for conversion. Therefore, as the difference in the ratio of the atomic number and atomic weight increases relative to that of limestone, the difference between the converted bulk density and the actual bulk density increases. In this study, equations were derived for various mineral compositions and applied to the density logging results. Matrix density was analyzed using a pycnometer, and the ratio between the atomic number and weight was calculated according to X-ray fluorescence analysis results. This approach improved the accuracy of the density logging data and reduced density errors. The proposed method is expected to be particularly useful for estimating in situ density at high-level radioactive waste disposal sites without complex geological formations.

Valorization of lithium containing slags from pyrometallurgical recycling route of spent lithium-ion batteries: The enrichment of γ-LiAlO2 phase from thermodynamic controlled and modified slags

Pyro-metallurgical processing technology is widely used in the spent lithium-ion batteries recycling to recover valuable metals such as cobalt, nickel and copper, while lithium primarily remains in the slag. The effective valorization of slag, especially lithium recovery, constitutes a significant issue in contemporary pyrometallurgical processes due to the paucity of studies. This paper proposes a novel perspective by defining slag as an aggregate of engineered artificial minerals. Thus, not only the parameters of the beneficiation process can be studied to optimize the separation efficiency during treatment, but also the slag can be re-designed to optimize the carrier minerals of target elements and gangue mineral composition in the initial step with thermodynamic tools. In this paper, the engineering of artificial minerals (EnAM) method was applied to the slag design of the Li2O-CaO-Al2O3-SiO2-MnO system, and an initial attempt was made to apply EnAM method to the flotation study. A flotation study on enrichment effect of the target phase γ-LiAlO2 from thermodynamic controlled slags is conducted.

Multi-Proxy Environmental Reconstruction of the Covacha de los Zarpazos in Galería Site (Atapuerca, Spain)

Magnetic properties of iron oxides provide invaluable data for environmental reconstruction during sediment deposition. Encouraged by the results of our previous studies in the near Gran Dolina site, we investigate the GI waterlain facies sediments that fill Galería Complex cave (Sierra de Atapuerca, Spain), in particular the Covacha de los Zarpazos cave considering two vertical profiles at different walls and comparing them with two profiles previously analysed. For the first time in this cave, we propose a correlation among these two walls based on the low field susceptibility values. An environmental reconstruction is proposed based on the pedogenesis and weathering processes, and water activity influencing the composition, concentration and grain size of magnetic minerals. In order to have a more comprehensive interpretation, elemental geochemistry was also analysed. The results allow to identify three different sections with the alternation of environmental characteristics.

Effect of elemental composition and phase transformation on lithium leaching behavior of micas in calcination-acid leaching process

Lithium (Li)-bearing clays have emerged as new types of Li resources. The structure and elemental composition of clay minerals play a crucial role in determining the Li leaching efficiency. The elemental composition and structural transformation of Li-bearing mica from Inner Mongolia (IMS) and Jiangxi (JS), China, were studied during the calcination-leaching process by using X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and electron microprobe analysis (EMPA). The findings indicate that Mica is the predominant Li-bearing mineral in both IMS and JS. Notably, the IMS mica contains a significantly higher concentration of fluorine compared to the JS mica. Fluorine exerts a minor inhibitory effect on Li leaching, whereas the hydroxyl group (OH) significantly inhibits the leaching of Li from mica. The removal of residual oxygen atoms post-dehydroxylation is crucial to extract Li from mica. Both defluorination and dehydroxylation reactions occur within the temperature range of 800 °C to 900 °C. When calcined at 900 °C, the IMS mica was transformed into sanidine, while the JS mica was transformed into microcline. The acid leaching of products calcined at this temperature represents a process that further disrupts the residual mica structure and facilitates a cation exchange reaction.

Properties, Treatment and Resource Utilization of Bauxite Tailings: A Review

A substantial amount of bauxite tailings (BTs) at abandoned mine sites have been stored in waste reservoirs for long periods, leading to significant land occupation and environmental degradation. Although many studies of the resource utilization of BTs were conducted to address this challenge, there is still a lack of efforts to systematically review the state of the art in BTs. In the present paper, a systematic literature review was carried out to summarize and analyze the properties, treatment, and resource utilization of BTs. Physical characteristics and the mineral and chemical composition of BTs are introduced. The efficacy of physical, chemical, and microbial treatment methods for BTs in terms of dehydration are outlined, and their respective benefits and limitations are discussed. Moreover, the extraction process of valuable elements (e.g., Si, Al, Fe, Li, Na, Nd, etc.) from BTs is examined, and the diverse applications of BTs in adsorption materials, ceramic materials, cementitious materials, lightweight aggregates, foamed mixture lightweight soil, among others, are studied. Finally, an efficient and smart treatment strategy for BTs was proposed. The findings of the present review provide a scientific basis and reference for future research focusing on the treatment and resource utilization of BTs.

Low Resistivity Pay Zone Detection in Hydrocarbon Formation: The Feasibility of the Spectral Induced Polarization Method

Summary Identifying and characterizing low resistivity pay (LRP) zones within hydrocarbon-rich formations has long been challenging in the petroleum industry due to their complex mineral composition, microporosity, and diminished resistivity contrasts. Traditional methods, such as resistivity measurements, struggle to effectively pinpoint LRP zones, prompting the need for innovative approaches in reservoir evaluation. This paper explores the feasibility of using the spectral induced polarization (SIP) method for detecting LRP zones. The SIP method measures complex conductivity across a frequency range from 1 mHz to 10 kHz. While this technique has been widely used in mining and environmental studies, its potential for petrophysics applications in the oil and gas sector remains largely unexplored. This study acts as a proof of concept, demonstrating the capability of SIP for detecting LRP zones. Laboratory experiments utilized dual-porosity silica gel samples with controlled micro- and macroporosity fractions and added pyrite content. Despite a high crude oil saturation of approximately 60%, the presence of brine in continuous micropores resulted in low resistivity readings (0.7 Ω·m) at low frequencies, as conventionally measured by direct current resistivity tools. However, at higher frequencies (&amp;gt;100 Hz), the study observed high average resistivity values (82 Ω·m), indicating a frequency-dependent behavior in electrical measurements. This behavior is attributed to polarization mechanisms, including the electrical double layer (EDL). This study’s findings propose the SIP method’s potential effectiveness for detecting LRP zones, paving the way for future research to delve deeper into the application of SIP in petrophysics.

Comparative experimental study of ash formation behaviors during the fixed-bed gasification of coal water slurry and dry pulverized coal prepared from Shenmu coal

The mechanism of ash formation during coal gasification is very important for the safety and stability of gasifier operation. This study comparatively investigated the ash formation behaviors during the gasification of coal water slurry and dry pulverized coal. Shenmu coal was gasified in a CO2 atmosphere at 900 °C using a fixed-bed reactor to prepare chars and ashes. Computer-controlled scanning electron microscopy was employed to characterize the compositions and particle sizes of minerals in the raw coal, coal water slurry gasification ash, and dry pulverized coal gasification ash. Morphological characteristics reveal that, during gasification, coal water slurry gasification char exhibits obvious agglomeration compared to the dry pulverized coal gasification char. The changes of mineral compositions indicate that, during both coal water slurry and dry pulverized coal gasification, minerals follow nearly identical transformation pathways, but the degrees of transformation are different. The influence of char agglomeration on heat transfer may be the reason for the less transformation of K Al-silicate and kaolinite during the coal water slurry gasification. Furthermore, in comparison to dry pulverized coal gasification, more Ca in calcite and S in pyrite transfer into gypsum during the coal water slurry gasification. The results from thermodynamic equilibrium calculations indirectly suggest that this may be attributed to the limited internal diffusion of CO2 within coal water slurry gasification char resulting from char agglomeration during gasification. Overall particle size distributions of minerals in raw coal, coal water slurry gasification ash, and dry pulverized coal gasification ash demonstrate that the degrees of mineral fragmentation are almost consistent during both coal water slurry and dry pulverized coal gasification. However, differences in the degrees of mineral transformation led to different particle size distributions of various minerals between coal water slurry gasification ash and dry pulverized coal gasification ash. This study mainly focuses on the influence of water in coal water slurry on ash formation, and it has not considered the influence of other factors, such as ash content, hydrophilicity, caking property, and gasification reactivity of coal, which need further research to explore.

Profiling of Tayammum Clay Product in Malaysia by Spectroscopic-Chemometric Approach

Tayammum is a dry purifying method that uses earthen materials, mostly clay. The technique is applied when there is no access to water or in specific circumstances, such as when a person has susceptible skin on water. In tayammum, Islamic law describes clay as pure dust or soil used as a cleansing agent. Nevertheless, no scientific report examined the components of clay present in tayammum clay. Therefore, this study aimed to characterise and profile the mineral composition of tayammum clay, which is a commercially available product in Malaysia. Twelve commercial clay samples and one representative sample were analysed by ATR-FTIR spectroscopy in the range of 4000 to 600 cm-1. PCA exploratory analysis clearly demonstrated the differentiation of the tayammum clay product into seven groups according to its functional group. Following the FTIR analysis, the samples underwent examination using X-ray diffraction (XRD) and X-ray fluorescence (XRF) spectrometers further to identify the mineral and element composition of the clay, respectively. The XRD analysis indicated that there were possibly four types of mineral powder commonly distributed in the market for Tayammum purposes which are three types of clay: palygorskite, kaolinite, and phengite, and another one is zeolite-type: Na-heulandite. All four of them are common materials used for adsorbent and cleansing purposes.

A New Brittleness Evaluation Index for Reservoir Rocks Based on Fuzzy Analytic Hierarchy Process and Energy Dissipation

Summary Accurate and quantitative evaluation of rock brittleness is essential for optimizing hydraulic fracturing parameter design. Specific aspects of rock brittleness can be characterized based on mineral composition, strength parameter, stress-strain, and elasticity parameter. However, in characterizing the effect of high confining pressure on rock brittleness, these advantages have not been shown for various reasons. The essence of rock fracture resides in the accrual and dissipation of energy, concomitant with the transformation of three distinct energy modalities: elastic energy, dissipated energy, and post-peak release energy. In this study, we proposed a new brittle index for reservoir rocks considering the interactions of the energy evolution process in different stages. The associated Bii values are computed through the analysis of energy evolution based on the fuzzy analytic hierarchy analysis process (FAHP) method. Tri-axial compression tests were conducted on granite, shale, and sandstone specimens under different confining pressures for the validation of the proposed brittleness evaluation (BE) index. The results indicate a decreasing trend in the brittleness index with increasing confining pressure. Comparative analysis with other existing brittleness evaluation indexes demonstrates that the new brittleness evaluation index offers a more precise evaluation of the brittleness of various rock types.

Characterization and origin of high-Al chromitites: A case study of chromite deposit in the Kudi ophiolite in the NW Tibetan Plateau

Chromitite occurrences in ophiolites are commonly classified into high-Cr (Cr# > 60) and high-Al (Cr# < 60) varieties. High-Cr chromitites have been extensively studied, whereas the origin of high-Al chromitites remains enigmatic mainly due to strong alteration of the relevant rocks. This study undertook a comprehensive examination of alteration-free high-Al chromitites and their hosting peridotites from the Kudi ophiolite in the NW Tibetan Plateau, complemented by a synthesis of global data of high-Al and high-Cr chromite deposits. Our results reveal that harzburgites, hosting both types of chromite deposits, exhibit similar major oxide compositions in their constituent minerals. In contrast, the constituent minerals in the dunite envelopes and chromitites display distinct major and trace element compositions, which are probably controlled by the compositions of infiltrating melts. For both chromite deposits, the forsterite (Fo) contents of olivine increase from harzburgite (90.0–91.6) to dunite (89.9–94.6) and chromitite (90.0–97.2). Mineral compositions of olivine show significant variabilities at the contact boundaries between densely disseminated and sparsely disseminated chromitites. These features suggest that fluid immiscibility plays an important role in the formation of high-Al chromitite. A continuous spectrum of major oxide compositions of chromite from high-Al to high-Cr chromitites suggests a progressive shift in the parental magma compositions from mid-ocean ridge basalt-like to boninitic melts, implying a rapid tectonic transition during subduction initiation.

EXPERIMENTAL MODELLING OF HYPERGENE PROCESSES FOR BALEY ORE FIELD AS AN EXAMPLE

Samples of primary low-sulphide gold-quartz ore and oxidised host rock containing up to 10 wt% sulphides and 5 wt% their oxidation products were investigated to reveal the relationship between the migration of elements during the hypergenic transformation of ores and rocks and their mineral composition. Mineralogical studies employed optical and electron microscopy to identify the shapes and sizes of mineral individuals and aggregates and to determine their chemical composition. It is determined for major element content that the oxidised host rocks contain significantly more iron, sulphur, aluminium, potassium and phosphorus than primary low-sulphide quartz gold ores, while silicon and calcium content is lower. This is due to the removal of sulphur and iron into the near-vein rocks with the formation of primarily pyrite and arsenopyrite, and the presence of aluminosilicates (feldspars and layered silicates) in them. The same applies to arsenic and antimony, as their concentrations are higher in the host rocks than in the ores. The rates of lithophile elements recovery from primary gold-quartz ores are much higher than those from oxidised host rocks. Сhalcophile elements, on the contrary, are more intensively transferred to the solution from host rocks. Thus, the complex of elements extracted from ore suspensions is directly determined by their mineral composition. The main carrier of gold is native gold and its tellurides. Silver is associated with low-grade gold, copper and silver sulphosalts, and also tellurides.

Assessment of mineral compositions on geo-mechanical time dependent plastic creep deformation

Understanding rock mechanical time-dependent plastic deformation enables the researchers to accurately predict rock responses during loading and unloading. This research focuses on the geomechanical aspects of hydrogen storage, particularly rock resistance to creep deformation under varying stresses and pressures. Modelling creep deformation in underground storage mediums has been overlooked and requires further consideration, as it is a critical, cyclical, time-dependent phenomenon essential for hydrogen containment. The study's novelty is demonstrated in its focus on geomechanical properties of rock minerals, providing insights that aid in site-selection criteria for hydrogen storage A creep deformation model with varying mineral compositions is used to assess creep deformation strain. In homogenous cases, calcite showed the highest resistance to creep deformation after three loading cycles, primarily due to its high Young's Modulus. As for the heterogenous cases, the results indicated that the mixture of calcite and quartz was the most creep-resistant rock composition. In terms of rock types, basalt samples demonstrated the highest resistance to creep deformation, while siltstone exhibited the highest susceptibility to deformation. It was observed that as the number of cycles increase, the rock mechanical stability decreases, hence optimizing the number of cycles is a must to ensure hydrogen geo-containment.

LEAD-LEAD DATING REVEALS PERMIAN REMOBILIZATION OF NIOBIUM MINERALIZATION AT BAYAN OBO

Abstract The Bayan Obo deposit hosted by the H8 unit is a world-class rare earth element (REE) deposit with considerable niobium (Nb) and iron (Fe). Permian granites are widely exposed in the mining area and have a close spatial association with the Nb mineralization. Whether the granites contributed Nb or only remobilized existing mineralization is important for understanding the controls of ore formation. Previous studies have mostly focused on the REEs, whereas research on Nb has been limited. This is due mainly to the difficulty of accurately determining the age of the Nb mineralization because of the fine-grained and texturally complex nature of the Nb-bearing minerals and their exceptionally low U content. Although microbeam techniques show promise in tackling the aforementioned challenges, their application is hampered by matrix effects caused by the diverse composition of Nb-bearing minerals. Here we report the application of a high-precision secondary ion mass spectrometry (SIMS) Pb-Pb isochron approach that enables young samples (i.e., &amp;lt;500 Ma) to be dated without matrix-matched reference materials. A variety of Nb-bearing minerals from eastern Bayan Obo were analyzed, yielding Pb-Pb isochron ages of 276 ± 10 Ma (pyrochlore, 394–6,864 ppm U in the rim and 6,563–19,858 ppm in the core), 277 ± 36 Ma (fersmite, 18–61 ppm U; fergusonite-Ce, 45–95 ppm U), and 257 ± 46 Ma (aeschynite, 342–1,006 ppm U). In combination with the deposit geology and petrographic observations, these ages link the Nb mineralization to ~270 Ma granites. As these granites are not particularly rich in Nb, skarn formation during granite emplacement is interpreted to have remobilized the existing Nb mineralization, which increased the grain size of the Nb-bearing minerals—a key factor facilitating their extraction. Our study shows that high-precision SIMS Pb-Pb analysis holds promise for directly dating mineralization without matrix-matched reference materials. It also emphasizes the need to consider the role of the Nb remobilization at Bayan Obo and elsewhere.