Hasil untuk "Mineralogy"

Argyro Tsandalidou, Konstantinos Dogeas, Eleftheria Tetoula Tsonga et al.

Satellite imagery is employed for large-scale prospectivity mapping due to the high cost and typically limited availability of on-site mineral exploration data. In this work, we present a proof-of-concept framework that leverages generative representations learned from multispectral Sentinel-2 imagery to identify gold-bearing regions from space. An autoencoder foundation model, called Isometric, which is pretrained on the large-scale FalconSpace-S2 v1.0 dataset, produces information-dense spectral-spatial representations that serve as inputs to a lightweight XGBoost classifier. We compare this representation-based approach with a raw spectral input baseline using a dataset of 63 Sentinel-2 images from known gold and non-gold locations. The proposed method improves patch-level accuracy from 0.51 to 0.68 and image-level accuracy from 0.55 to 0.73, demonstrating that generative embeddings capture transferable mineralogical patterns even with limited labeled data. These results highlight the potential of foundation-model representations to make mineral exploration more efficient, scalable, and globally applicable.

I. McDonald, A. A. Zijlstra, N. J. Cox et al.

Temperature and luminosity are the two key diagnostics of a star, yet these cannot come directly from survey data, but must be imputed by comparing those data to models. SED fitting offers a high-precision method to obtain both parameters for stars where both their distance and extinction are well known. The recent publication of many all-sky or large-area surveys coincides the publication of parallaxes and 3D extinction cubes from the Gaia satellite, making it possible to perform SED fitting of truly large ($>10^8$) numbers of Galactic stars for the first time. The analysis of this data requires a high level of automation. Here, we describe the ongoing Gaia All-Sky Stellar Parameters Service (GASPS): the fitting of 240 million SEDs from Gaia DR3 and the extraction of temperatures and luminosities for the corresponding stars using the PySSED code. We demonstrate the quality of the initial results, and the promise that these data show, from wavelength-specific information such as the ultraviolet and infrared excess of each star, to stellar classification, to expansion of the project beyond our own Galaxy, and mineralogical mapping of the Milky Way's interstellar medium.

L. S. Morrissey, D. S. Ebel, L. E. J. Eriksson et al.

Coagulation of dust particles in protoplanetary disks is the first step on the journey to the formation of planets. The surface free energy (SFE) of the dust particles determines the effectiveness of particles sticking to each other after collision, as well as the critical collision velocity above which fragmentation will occur. Studies of SFE have focused on the simplest silicate, silica, usually at standard temperature and pressure. However, protoplanetary dust grains have a wide variety of mineralogical compositions, temperatures, and a low-pressure environment lacking in water vapor. We perform molecular dynamics simulations using a ReaxFF-type potential of the SFE of silica, albite, and anorthite at temperatures ranging from 30 to 700 K in a true vacuum. We find that the SFE drops by tens of percent with increasing temperature or shifting to more complex silicate compositions. More dramatically, we find that the values of the SFE in a vacuum are two orders of magnitude higher than those usually measured in terrestrial laboratories. Our results confirm previous work that suggests that hydroxylation by monolayers of water produces this reduction in SFE in experiments. The coagulation of dust grains thus appears to depend critically on the cleanliness of their surfaces, as well as their temperature and composition.

Muhammad Jawad Zeb, Mehboob ur Rashid, Ihtisham Islam et al.

The Michni area within the Warsak complex that is part of the Peshawar plain alkaline igneous province (PPAIP) in NW Pakistan, hosts a diverse suite of alkaline and carbonatitic rocks whose origin and evolution remain poorly constrained. This study focuses on this locality due to its complex lithological assemblage and the first discovery of carbonatite intrusions in the area, which fills a significant gap in the regional petrogenetic framework. Detailed fieldwork, petrographic analysis, and whole-rock geochemistry (XRF-based major and trace elements) were employed to investigate the petrogenesis and tectonic setting of these rocks. The intrusive suite includes pyroxenite, melteigite, ijolite, urtite, nepheline syenite, fenite, and both calcio- and ferro-carbonatites. Geochemical data reveal strong silica undersaturation and systematic fractionation trends, indicating magmatic differentiation from a shared parental magma. Pervasive fenitization and secondary phases such as cancrinite, phlogopite, and carbonate suggest metasomatic alteration driven by late-stage carbonatitic fluids. While petrographic and geochemical coherence supports a potential genetic link between silicate and carbonatite suites. This study enhances understanding of the magmatic and metasomatic evolution in PPAIP and recommends future high-resolution isotopic and mineral chemical analyses to further constrain magma source characteristics and alteration processes.

Jana Fridrichová, Peter Bačík, Olena Rybnikova et al.

Abstract Topaz is frequently subjected to heat treatment and irradiation to enhance colour, particularly to produce the market’s most preferred salmon pink and sky blue varieties. However, an insufficient description of these processes can lead to fraudulent practices. This experimental and forensic mineralogical and gemmological study investigates eighteen heat-treated topaz samples from Ouro Preto (OP) and Caraí (CA), Brazil, using electron microanalysis, LA-ICP-MS, Raman, and optical absorption spectroscopy before and after heat treatment at various temperatures. The most significant optical changes were observed at 300 °C when the CA sample lost its colour from sky blue to colourless, while OP samples retained their imperial orange colour up to 500 °C before transitioning to pink at 700 °C. Chemically, the CA samples are rich in F (> 1.8 apfu) with low trace element concentration (Fe ≤ 125 ppm, Ge ≤ 153 ppm), falling to the pegmatite and greisen field of topaz origin. The OP samples contain less F (1.4–1.5 apfu) but higher trace element contents (Cr up to 204 ppm, Ti up to 115 ppm, Fe, Mn, Ge < 64 ppm), consistent with a hydrothermal origin. Raman spectra show no significant inter-sample variation, but their luminescence spectra feature strong differences: Mn acts as the luminophore in CA samples, while Cr3+ centers dominate in OP samples. The optical absorption spectra reveal distinct thermal responses. The OP samples heated to temperatures ≥ 500 °C developed new absorption bands at 530–532 nm, consequently resulting in a visible pink colour. On the other hand, the CA spectra exhibit strong absorption in the NIR region; the unheated sample has a broad absorption band at 634 nm, responsible for the sky-blue colour of topaz. Heating ≥ 300 °C eliminates the transmission window in the blue to cyan regions, removing blue colouration. These thermal-optical signatures serve as indicators of heat treatment in topaz declared from these two localities. Moreover, the combination of spectroscopic methods, which we successfully applied in recognizing heat treatment on the studied samples, provides a systematic approach for identifying treatment in topaz and potentially other gemstones.

Carmen Alonso-Fernández, Luis Ángel Ortega, Javier Jiménez-Echevarría et al.

The age of the first construction of the churches of Nuestra Señora de las Viñas (Quintanilla de las Viñas, Burgos), Santa María de Rute (Ventas Blancas, La Rioja), and San Juan Bautista (Barbadillo del Mercado, Burgos) of the northern Iberian Peninsula has been subject to debate for decades. Some scholars date the construction of the churches to the Visigothic period (6th and 7th centuries), while others attribute them to the early Middle Ages (9th and 10th centuries). To shed light on this controversy, the ¹⁴C dating of the binder fraction of mortars of the earliest construction phases was carried out. To determine the suitability of the mortars for ¹⁴C dating, the mineral composition of the binder was determined by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Samples were dated using ¹⁴C Accelerator Mass Spectrometry (AMS). Binder mineralogy precludes some samples from radiocarbon dating. Radiocarbon dating of the Nuestra Señora de las Viñas mortars yielded ages of 534–640 cal AD and 584–658 cal AD. Santa María de Rute yielded ages of 564–650 cal AD, corresponding to Visigothic ages. The San Juan Bautista sample yielded an age of 876–995 AD, although a mortar stratigraphically below results was not suitable for dating.

Ye Wu, Qing Zhang, Yishi Wang et al.

Davemaoite, as the third most abundant mineral in the lower mantle, constitutes significant amounts in pyrolite and mid-ocean ridge basalts. Due to its unquenchable nature, measurements by static compression techniques on physical properties of davemaoite at lower mantle conditions are rare and technically challenging, and those are essential to constrain compositions and properties of mineralogical models in the lower mantle. Here, we present Hugoniot equation of state and sound velocity of CaSiO3 glass under shock compression. The CaSiO3 glass transforms into the crystalline phase above 34 GPa and completely transforms into davemaoite above 120 GPa. Thermal equation of state and Hugoniot temperature of davemaoite have been derived from the shock wave data. The CaSiO3 glass under shcok compression has very high shock temperature. Shock wave experiments for sound velocity of CaSiO3 glass indicate that no melting is observed at Hugoniot pressure up to 117.6 GPa. We propose that the melting temperature of davemaoite should be higher than those reported theoretically by now.

Hui Chen, Duncan T. L. Alexander, Cécile Hébert

Energy dispersive X-ray (EDX) spectroscopy in the transmission electron microscope is a key tool for nanomaterials analysis, providing a direct link between spatial and chemical information. However, using it for precisely determining chemical compositions presents challenges of noisy data from low X-ray yields and mixed signals from phases that overlap along the electron beam trajectory. Here, we introduce a novel method, non-negative matrix factorisation based pan-sharpening (PSNMF), to address these limitations. Leveraging the Poisson nature of EDX spectral noise and binning operations, PSNMF retrieves high quality phase spectral and spatial signatures via consecutive factorisations. After validating PSNMF with synthetic datasets of different noise levels, we illustrate its effectiveness on two distinct experimental cases: a nano-mineralogical lamella, and supported catalytic nanoparticles. Not only does PSNMF obtain accurate phase signatures, datasets reconstructed from the outputs have demonstrably lower noise and better fidelity than from the benchmark denoising method of principle component analysis.

Shohei Wakayama, Alberto Candela, Paul Hayne et al.

Autonomous selection of optimal options for data collection from multiple alternatives is challenging in uncertain environments. When secondary information about options is accessible, such problems can be framed as contextual multi-armed bandits (CMABs). Neuro-inspired active inference has gained interest for its ability to balance exploration and exploitation using the expected free energy objective function. Unlike previous studies that showed the effectiveness of active inference based strategy for CMABs using synthetic data, this study aims to apply active inference to realistic scenarios, using a simulated mineralogical survey site selection problem. Hyperspectral data from AVIRIS-NG at Cuprite, Nevada, serves as contextual information for predicting outcome probabilities, while geologists' mineral labels represent outcomes. Monte Carlo simulations assess the robustness of active inference against changing expert preferences. Results show that active inference requires fewer iterations than standard bandit approaches with real-world noisy and biased data, and performs better when outcome preferences vary online by adapting the selection strategy to align with expert shifts.

Shyama Prosad Moulick, Farhana Jahan, Md. Zia Uddin Al Mamun et al.

Since the nutritional makeup of many plants is still unknown, people have historically included them in their diets without even being aware of their health advantages. Therefore, the present study aimed to uncover the proximate composition, minerals, vitamins, amino acids, and fatty acids composition of two locally consumed vegetables, namely Boerhavia diffusa and Coccinia grandis. From the analysis, these vegetables had a significant protein, fat, and carbohydrate content. Regarding mineral contents, both plants had a great amount of potassium, calcium, iron, sodium, and zinc. These vegetables had a remarkable content of vitamins such as B1, B2, B3, B5, B6, and C. The leaves of both plants had important essential amino acids such as leucine, lysine, and phenylalanine, as well as non-essential amino acids. Unsaturated fatty acids such as linolenic acid, linoleic acid, and erucic acid were more prominent in Coccinia grandis than Boerhavia diffusa. In addition, both plants had a significant amount of saturated fatty acids such as palmitic acid, stearic acid, and lauric acid. Thus, it can be concluded that these two vegetables have magnificent profiles of nutrients which could make them as important sources of minerals, vitamins, and fatty acids.

Cem Yücel, Emre Aydınçakır, Abdullah Kaygusuz et al.

The Eastern Pontides host a diverse suite of plutonic rocks spanning a wide range of ages and compositions. Among these, the Middle Eocene Kazıkbeli pluton, located in the Kürtün districtof Gümüşhane, stands out due to its distinctive petrological characteristics. This study aims to unravel the petrological implications of petrographic and mineral chemical data to determine thephysicochemical conditions (temperature, pressure, oxygen fugacity) under which the Kazıkbeli magma crystallized and was emplaced. By integrating mineral chemical data, we seek to quantifyemplacement pressure, crystallization temperature, and oxygen fugacity. A comprehensive understanding of the genetic relationships and physicochemical properties of the Kazıkbelipluton rocks, as determined through geological, petrographic and mineral chemistry, is crucial for elucidating the geological evolution of the Eastern Pontides. The Kazıkbeli Pluton exhibits apredominant NE-SW orientation and encompasses an area of roughly 46 km². Modal mineralogical analysis reveals a compositional spectrum ranging from gabbroic diorite to monzogranite, withgranodiorite and tonalite being the most prominent rock types. Textural variations encompass fineto medium-grained, porphyritic, poikilitic, and occasionally graphic textures. The primary mineralassemblage of the pluton comprises plagioclase, orthoclase, quartz, amphibole, biotite, and Fe-Ti oxides. Accessory minerals include zircon, apatite, sphene, and allanite. Plagioclases are labradorite to oligoclase (An26 to An66) in composition. K-feldspar minerals exhibited an orthoclase composition (Or80 to Or97). All amphiboles belong to the calcic amphibole field and exhibit a magnesio-hornblende (Mg#=0.63-0.73) composition. Biotites crystallized as solidified melt products with compositions between annite and phlogopite endmembers, plotting close to the magnesium-rich (Mg#=0.52- 0.58) end of the phlogopite solid solution series. Calculated crystallization temperatures derived from amphibole and biotite data range from 712°C to 824°C. Pressure estimations calculated using amphibole-plagioclase, amphibole and biotite suggest a range of 0.04 to 2.06 kbar. Oxygen fugacity (ƒO2) values calculated using amphibole and biotite fall between -12.5 and -16.1. Amphibole-based water content estimations indicate a range of 3.7% to 5.7% for the pluton. Biotite compositions within the studied Kazıkbeli pluton rocks exhibit characteristics suggestive of a potential mantle origin. Geobarometric calculations based on mineral chemistry data with geological and petrographic features indicate the emplacement of the Kazıkbeli Pluton at relatively shallow depths within the crust (~1 to 8 km).

Georgios Lazaridis, Emmanouil Katrivanos, Despoina Dora et al.

Caves serve as time capsules, preserving significant markers of tectonic activity and offering insights into geological history. Fault geometries and past activations found in caves can be correlated with known deformational events in the broader area, temporally delimiting the speleogenesis. More specifically, cave passage formation is suggested to be affected by the regional stress-field. The Asprorema Cave in Northern Greece is a typical example of a fracture guided cave, with passage geometry influenced by relative sidewall movements, revealing these discontinuities as faults. This study constructs the timeframe and conceptual model of speleogenesis in relation to tectonic events, geomorphological evolution and hydrological zones, and verifies its relation to the stress-field. Active tectonics, mineralogy and cave geomorphology are investigated. Results suggest syntectonic speleogenesis under phreatic and epiphreatic conditions. The absence of corrosion on fault slip surfaces implies recent activations post cave’s shift to the vadose zone. Structural analysis identifies three main neotectonic phases: NNW-SSE striking faults (oldest group of structures), NE-SW striking faults with dextral strike-slip movement (post-middle Miocene), and NE-SW striking normal faults indicating extensional stress-regime (Quartenary). The last two phases affect cave passage shape causing wall displacement, highlighting passage formation along discontinuities perpendicular to the horizontal minimum stress axis.

Jose Refugio Parga Torres, Nelson Oshogwue Etafo, Gregorio Gonzalez Zamarripa

Mexico is the 9th largest world gold producer with 1016 tonnes in reserves as of 2024. 41 % losses of gold with an average consumption of 40 g/t, is due to the escape of fine AC particles because they do not have the scope to prevent the loss of particles below 0.40 mm. The recovery of gold in Mexico is becoming more important. Given the low quantities of this metal present in the mineral ore and the difficulty of its extraction due to its encapsulation in its mineralogy, recoveries are low. Adsorption processes with activated carbon (AC) in the mining-metallurgy industry include phases that diminish the particle durability, coupled with its nature as organic matter, which tends to deteriorate and disintegrate in the adsorption systems. In this study, Electrocoagulation (EC) technology is shown as a better option to increase the efficient recovery of gold impregnated in extremely fine AC particles, without the use of chemical reagents in the metallurgical systems, by recovering the fine particles loaded with gold, EC tests were done on a batch pilot scale, on AC particles of 0.106 mm and 0.053 mm, using iron and aluminum electrodes with the best variables determined, they were interpolated at an industrial level. The trend that has been noticed is that smaller particles stick together to generate larger particles that contain aluminum hydroxide species. This means that using EC to recover incredibly fine AC particles is viable. Finally, the EC system with aluminum (Al) and iron (Fe) electrodes shows AC recoveries with gold were greater than 96 % and 88 % respectively. This study is a green technology for the effective recovery of gold, and cyanide in activated carbon thereby in increasing gold productivity in Mexico and the global market.

Denton S. Ebel, Richard O. Sack

Djerfisherite is an important carrier of potassium in highly reduced enstatite chondrites, where it occurs in sub-round metal-sulfide nodules. These nodules were once free-floating objects in the protoplanetary nebula. Here, we analyze existing and new data to derive an equation of state (EOS) for djerfisherites of K_{6}(Cu,Fe,Ni)^{B} (Fe,Ni,Cu)^{C}_{24} S_{26}Cl structural formula. We use this EOS to calculate the thermal stability of djerfisherite coexisting in equilibrium with a cooling vapor of solar composition enriched in a dust analogous to anhydrous, chondritic interplanetary dust (C-IDP). We find that condensed mineral assemblages closely match those found in enstatite chondrites, with djerfisherite condensing above 1000 K in C-IDP dust enriched systems. Results may have implications for the volatile budgets of terrestrial planets, and the incorporation of K into early-formed, highly reduced, planetary cores. Previous work links enstatite chondrites to the planet Mercury, where the surface has a terrestrial K/Th ratio, high S/Si ratio, and very low FeO content. Mercury's accretion history may yield insights into Earth's.

Jonah S. Peter, Tom A. Nordheim, Kevin P. Hand

The Cassini spacecraft observed that Saturn's moon Enceladus possesses a series of jets erupting from its South Polar Terrain. Previous studies of in situ data collected by Cassini's Ion and Neutral Mass Spectrometer (INMS) have identified H$_2$O, CO$_2$, CH$_4$, NH$_3$, and H$_2$ within the plume of ejected material. Identification of minor species in the plume remains an ongoing challenge, owing to the large number of possible combinations that can be used to fit the INMS data. Here, we present the detection of several new compounds of strong importance to the habitability of Enceladus, including HCN, C$_2$H$_2$, C$_3$H$_6$, and C$_2$H$_6$. Our analyses of the low velocity INMS data, coupled with our detailed statistical framework, enable discrimination between previously ambiguous species in the plume by alleviating the effects of high dimensional model fitting. Together with plausible mineralogical catalysts and redox gradients derived from surface radiolysis, these compounds could potentially support extant microbial communities or drive complex organic synthesis leading to the origin of life.

Fendy Nur Afikah, Ismail Roniza, Shafiee Nor Shahida et al.

Rare earth element (REE) become the ‘critical metals’ for green technology development that have been rapidly expanded worldwide in these days. REE is mainly originated from granitic rocks. REE in ion adsorption clay (IAC) is the product from weathering of granite. IAC are believed to store high concentration of heavy rare earth element (HREE) and light rare earth element (LREE). Gua Musang is selected for this study because it is located on the three longitudinal belts that composed of acid volcanic igneous rocks from Main Range, Senting and Boundary Range Granites. In this study, the characteristics of ion adsorption clays and REE distribution in Gua Musang have been studied by mineralogy and geochemical analyses. Rocks and soil samples were collected closed to the granite bodies and its surrounding to represent its weathering products. Polarised optical microscopy was used for petrography and mineralogy studies. From fieldwork observation, Gua Musang lithologies composed of carbonate facies, argillaceous facies and pyroclastic facies. X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD) and Inductive Coupled Plasma Microspectrometry (ICP-MS) were used accordingly to characterise the composition of major and trace elements in IAC samples. REE value in Pulai are the highest concentration as iron nodule have been found in the sampling area. Sample from Boundary Range granite also reported store high concentration of REEs in this study.

V.I. Popova, V.A. Popov, I.A. Blinov et al.

The sequence of formation of pyrochlore crystals of various morphology and composition is considered in an aggregate with ilmenite and feldspar from nepheline-feldspar pegmatite at Mt. Dolgaya (Vishnevye Mountains, South Urals): altered yellowish green «uranium pyrochlore» with a UO3 content of 7.62–42.44 wt. % in different parts of the crystal, as well as fluorocalciopyrochlore, fersmite, and associated minerals. The alteration of «uranpyrochlore» includes fersmitization and silicification in contrast to relatively late fluorocalciopyrochlore and fersmite. The compositions and Raman spectra of altered «uranpyrochlore» and later fluorocalciopyrochlore are given.

C. E. Woodward, A. Evans, D. P. K. Banerjee et al.

Luminous Red Variables (LRVs) are most likely eruptions that are the outcome of stellar mergers. V838 Mon is one of the best-studied members of this class, representing an archetype for stellar mergers resulting from B-type stars. As result of the merger event, nova-like eruptions occur driving mass-loss from the system. As the gas cools considerable circumstellar dust is formed. V838 Mon erupted in 2002 and is undergoing very dynamic changes in its dust composition, geometry, and infrared luminosity providing a real-time laboratory to validate mineralogical condensation sequences in stellar mergers and evolutionary scenarios. We discuss recent NASA Stratospheric Observatory for Infrared Astronomy SOFIA 5 to 38 micron observations combined with archival NASA Spitzer spectra that document the temporal evolution of the freshly formed (within the last 20 yrs) circumstellar material in the environs of V838 Mon. Changes in the 10 micron spectral region are strong evidence that we are witnessing a classical dust condensation sequence expected to occur in oxygen-rich environments where alumina formation is followed by that of silicates at the temperature cools.

Ahmed Elshabrawy, Mona Ali

The black crust phenomenon appears clearly in the Bannentiu tomb, an ancient Egyptian tomb back to the 26th dynasty in the Bahariya oasis, one of the main iron ores in Egypt’s western desert. The black crusts are attributed to the high content of Fe and Mn oxides and oxyhydroxides components in the sandstone host rock formation as cement materials. Nondestructive investigations were carried out for the collected samples using optical microscopy, XRD, XRF, and SEM–EDX analyses. The observed results indicate that silica, iron, manganese compounds, clay minerals, and other remaining elements classify the black crusts as one of the rock varnish species. The present study aims to analyze and classify the chemical composition and mineralogy of the black crusts formed on the wall paintings of the Bannentiu tomb. Moreover, the study proposes a model formation for the rock varnish on the Bannentiu tomb wall painting. The proposed simulation relies on high ratios of Fe and Mn in the host rock and the microclimatic factors that cause the migration of these elements to the surface, with the oxidization factors giving rise to oxides and hydroxides low crystallinity.

Taiwo A. Bolaji, Michael N. Oti, Mike O. Onyekonwu et al.

The Niger Delta is one of the most prolific hydrocarbon provinces in the world, but information on basinal hydrogeology is scanty. Oilfield brines from nine producer wells in the Miocene reservoirs (2,472.25–3,532.48 m.b.s.l.), offshore Niger Delta, have been investigated along with two seawater samples to understand their hydrogeochemical characteristics in relation to the host rock mineralogy. Chemical analysis revealed that the waters are slightly alkaline and can be generally classified as saline water of the Na–Cl type based on their total dissolved solids (TDS). On the basis of bicarbonate, chloride, and sulphate ions, they are shown to be of connate origin. Relative abundance of major ions is in the following order: Na > Ca > Mg > K and Cl > HCO3 > SO4. Saturation indices (SI) of selected mineral phases calculated using PHREEQC indicate that the dissolution of iron oxide and carbonate minerals may contribute major ions in the formation water. The preponderance of alkali elements suggests the presence of feldspars, which could have resulted from sediments through which the water flows. An inverse relationship is observed between the resistivity of formation water and its TDS, which could be used to calculate resistivity values of formation waters in the area if the TDS contributions are known. Chemical data suggest that the formation waters were derived from seawater, dominantly altered by reverse ion-exchange processes and subsequently by water-rock interactions. Multivariate statistical analyses (correlation and factor analysis) indicate multiple sources of enrichment of ions in the formation waters.