Mineral Occurrences Research Articles

Source of inorganic components in the Middle Jurassic inertinite-rich coals of the Southern Ordos Basin, China: With emphasis on formation of Sr- and Ba-bearing minerals

The Middle Jurassic coal seams located in the southern Ordos Basin display notably high concentrations of barium (Ba) and strontium (Sr). To acquire a comprehensive understanding of the source and occurrence of the elevated contents of Ba- and Sr-bearing minerals and their formation mechanism in the coal, a suite of petrological, mineralogical, and geochemical analyses was conducted on the Middle Jurassic coals of the Gaojiapu mine (No. 4 Coal) from the Binchang mining area, using optical microscopy, field emission-scanning electron microscopy, X-ray diffraction, X-ray fluorescence, and inductively coupled plasma mass spectrometry. The results indicate that the No. 4 Coal is a high volatile B bituminous coal, which is characterized by low ash, medium sulfur, and high inertinite contents. The modes of occurrence of minerals identified in the coal, including calcite, dolomite, pyrite, quartz, kaolinite, anatase, barite, and celestine, indicate that the No. 4 Coal may have been subjected to multiple stages of solutions injection. Barium and Sr in the investigated coals are significantly enriched, exhibiting maximum values of 19738 μg/g and 9932 μg/g, respectively, while concentrations of other trace elements are generally depleted. Barite and celestine, generally coexisting with carbonate minerals, commonly occur as cell- and fracture-fillings. Furthermore, the strong correlation coefficients (r) for Ba vs. Ca + Mg and Sr vs. Ca + Mg (0.78 and 0.61, respectively) indicate that most barite and celestine have a close association with carbonate minerals of epigenetic origin. The highly elevated concentrations of Ba and Sr are thought to be primarily derived from solutions leaching barite deposits developed in the Qinling Orogenic Belt, which is located in the south of the Ordos Basin. When mapped spatially, the distributions of Ba and Sr concentrations are fan-shaped, decreasing from the NW to the SE of the mining area. Meteoric water containing dissolved CO2 induced partial dissolution of carbonate rocks, and during this process, selected metal ions (e.g., Ca2+, Mg2+, Al3+, Si2+, Fe2+, Ba2+, and Sr2+) were redistributed and subsequently migrated along fracture zones to the coal seam. The fracture systems and abundant cavities within inertinite in the coal provided sufficient space and conduits for solutions migration.

Geology, mineralogy and occurrence of gold minerals in oxide part of the Shadan copper-gold mine, Southern Khorasan

Geology, mineralogy and occurrence of gold minerals in oxide part of the Shadan copper-gold mine, Southern Khorasan

Occurrence and magmatic origin of platinum-group minerals in the Hongge layered intrusion, SW China

Occurrence and magmatic origin of platinum-group minerals in the Hongge layered intrusion, SW China

Multiscale multimodal characterization and simulation of structural alterations in failed bioprosthetic heart valves.

Calcific degeneration is the most frequent type of heart valve failure, with rising incidence due to the ageing population. The gold standard treatment to date is valve replacement. Unfortunately, calcification oftentimes re-occurs in bioprosthetic substitutes, with the governing processes remaining poorly understood. Here, we present a multiscale, multimodal analysis of disturbances and extensive mineralisation of the collagen network in failed bioprosthetic bovine pericardium valve explants with full histoanatomical context. In addition to highly abundant mineralized collagen fibres and fibrils, calcified micron-sized particles previously discovered in native valves were also prevalent on the aortic as well as the ventricular surface of bioprosthetic valves. The two mineral types (fibres and particles) were detectable even in early-stage mineralisation, prior to any macroscopic calcification. Based on multiscale multimodal characterisation and high-fidelity simulations, we demonstrate that mineral occurrence coincides with regions exposed to high haemodynamic and biomechanical indicators. These insights obtained by multiscale analysis of failed bioprosthetic valves serve as groundwork for the evidence-based development of more durable alternatives. STATEMENT OF SIGNIFICANCE: Bioprosthetic valve calcification is a well-known clinically significant phenomenon, leading to valve failure. The nanoanalytical characterisation of bioprosthetic valves gives insights into the highly abundant, extensive calcification and disorganization of the collagen network and the presence of calcium phosphate particles previously reported in native cardiovascular tissues. While the collagen matrix mineralisation can be primarily attributed to a combination of chemical and mechanical alterations, the calcified particles are likely of host cellular origin. This work presents a straightforward route to mineral identification and characterization at high resolution and sensitivity, and with full histoanatomical context and correlation to hemodynamic and biomechanical indicators, hence providing design cues for improved bioprosthetic valve alternatives.

A Pore-Scale Model for Electrokinetic In situ Recovery of Copper: The Influence of Mineral Occurrence, Zeta Potential, and Electric Potential

Electrokinetic in-situ recovery is an alternative to conventional mining, relying on the application of an electric potential to enhance the subsurface flow of ions. Understanding the pore-scale flow and ion transport under electric potential is essential for petrophysical properties estimation and flow behavior characterization. The governing physics of electrokinetic transport is electromigration and electroosmotic flow, which depend on the electric potential gradient, mineral occurrence, domain morphology (tortuosity and porosity, grain size and distribution, etc.), and electrolyte properties (local pH distribution and lixiviant type and concentration, etc.). Herein, mineral occurrence and its associated zeta potential are investigated for EK transport. The new Ek model which is designed to solve the EK flow in complex porous media in a highly parallelizable manner includes three coupled equations: (1) Poisson equation, (2) Nernst–Planck equation, and (3) Navier–Stokes equation. These equations were solved using the lattice Boltzmann method within X-ray computed microtomography images. The proposed model is validated against COMSOL multiphysics in a two-dimensional microchannel in terms of fluid flow behavior when the electrical double layer is both resolvable and unresolvable. A more complex chalcopyrite-silica system is then obtained by micro-CT scanning to evaluate the model performance. The effects of mineral occurrence, zeta potential, and electric potential on the three-dimensional chalcopyrite-silica system were evaluated. Although the positive zeta potential of chalcopyrite can induce a flow of ferric ion counter to the direction of electromigration, the net effect is dependent on the occurrence of chalcopyrite. However, the ion flux induced by electromigration was the dominant transport mechanism, whereas advection induced by electroosmosis made a lower contribution. Overall, a pore-scale EK model is proposed for direct simulation on pore-scale images. The proposed model can be coupled with other geochemical models for full physicochemical transport simulations. Meanwhile, electrokinetic transport shows promise as a human-controllable technique because the electromigration of ions and the applied electric potential can be easily controlled externally.Graphical abstract

The features of the placement of gold deposits in Algeria

Relevance and purpose of the work. In the world market of precious metals, the value of gold is constantly growing, which determines the increase in production volumes and the need to increase resources through the search and exploration of new deposits. Te famous gold deposits in the Algerian People’s Democratic Republic are concentrated in its southern part, known as the In-Uzzali gold mining district. Te search for new deposits can be carried out afer understanding the geological features of the structure of the territory and establishing patterns of the occurrence of gold mineralization to certain geological elements. Research methods. Te research is based on the analysis of the published works of the predecessors. Te paper provides an analysis of the geological structure of the Akhaggar shield region, within which the In-Uzzali gold ore district is located. Results of the work. Te structural and tectonic structure of the district is considered. Te main features of gold-ore objects of the southern part of the Algerian Sahara (Hoggar Shield) were revealed, which allow to attribute the known deposits to three trips by association with groups of rocks: mylonites and ultramylonites (Tirek, Amesmessa); granites and syntectonic granites (Tekoyat); meta-sedimentary rocks (Tiririn, Abeggi). Tey were found to be confned to greenstone belts of Proterozoic age and belonging to the gold-quartz-sulfde formation. Recommendations for further study are given. Conclusions. Gold mineralization was detected in the objects of the In-Uzzali region in the area of the Hoggar shield. Based on the geological structure of the area, its study and conditions of localization of gold mineralization, the investigated area can be considered promising enough for the discovery of gold ore objects and replenishment of the mineral resource base of Algeria.

Prospectivity modelling of critical mineral deposits using a generative adversarial network with oversampling and positive-unlabelled bagging

The demand for critical minerals is rapidly increasing worldwide, yet future global supply remains uncertain due to the difficulty in discovering new deposits using traditional methods. To increase the success rate of exploration projects for these vital resources, the use of artificial intelligence is continuously increasing for big and complex data analysis. This study proposes a new machine learning-based framework that tackles common problems associated with exploring critical mineral deposits, such as the shortage of known mineral occurrences, challenges in selecting negative samples in barren regions, and unbalanced training data. Our framework combines an improved generative adversarial network with positive and unlabelled learning to enhance efficiency. To test the performance of the framework, we create prospectivity maps of mafic–ultramafic intrusion-hosted mineralisation for cobalt, chromium, and nickel in the Gawler Craton, South Australia. The models are trained on a carefully selected set of independent features based on a conceptual model derived from open-access exploration data, resulting in high and stable performance. The prospectivity maps show a strong spatial correlation between high probabilities and known mineral occurrences and predict potential greenfield regions for future exploration. Our models demonstrate a significantly higher accuracy compared to a conventional approach using a standard random forest classifier and reveal that geophysical features play a crucial role in mapping prospective regions of critical minerals. Overall, our framework has the potential to significantly enhance critical mineral exploration by providing a more accurate and efficient approach to identifying prospective regions for future mining operations.

Neoproterozoic potassic andesitic and lamprophyric rocks in the tupanci area, southernomost Brazil: Petrology and associated mineralization

Au and sulfide mineralizations occur in the Sul-Rio-Grandense Shield, and important occurrences of these metals are reported and attributed to the Lavras do Sul Shoshonitic Association (LSSA). Several authors point to a significant participation of andesitic and lamprophyric rocks in the formation of these deposits. The Tupanci area has the presence of andesites and lamprophyres, stratigraphically correlated to LSSA volcanic rocks (Hilário Formation), representing the northernmost exposures of this magmatism. The LSSA is one of the most complete Neoproterozoic Shoshonitic associations (ca. 592-590 Ma) in southern Brazil, containing plutonic, volcanic and hypabyssal rocks, related to the post-collisional stage of the Brasiliano/Pan-African orogeny. The andesitic rocks of the Tupanci area occur in the form of the lava flows, overlayed by volcanoclastic deposits, product of the reworking of the volcanic unit. Lamprophyres occur in the form of dykes, with N-NW direction, which are intruded in rocks of the metamorphic basement and in andesitic lava flows, being texturally separated and classified as spessartite and lamprophyric lapilli-tuff. The singular occurrence of the lamprophyric lapilli-tuff stands out, is analogous to Kimberley-type pyroclastic kimberlitic intrusions, depicting explosive manifestations linked to LSSA lamprophyres. The andesites and lamprophyres that ocour in Tupanci area show characteristics of high-K calc-alkaline or shoshonitic rocks, evidenced by LILE and LREE enrichment, negative Ti and Nb anomalies, plus positive Pb anomalies and the absence of Eu anomalies. These attributes reinforce the relationship of andesitic and lamprophyric rocks with related LSSA rocks. The presence of Au and Pt grains in the matrix of lamprophyric lapilli-tuff, highlights the economic importance of these rocks for the mineral occurrences in the region, where future studies can better define the metallogenetic potential for the rocks of the Tupanci area.

Mantle hydration initiated by Ca metasomatism in a subduction zone: An example from the Chandman meta-peridotite, western Mongolia

Fluids in subduction zones contain various aqueous species and cause metasomatic reactions as well as hydration (i.e., serpentinization) at the slab–mantle interface. However, the nature of elemental transfer during fluid infiltration into the dry mantle in the subduction zone is poorly understood. In this study, we describe novel textures related to orthopyroxene (Opx) pseudomorphs and antigorite veins in the Chandman meta-peridotite body in the Alag Khadny accretionary wedge, western Mongolia. This body consists mainly of meta-harzburgite and meta-dunite, and hydration proceeded pervasively within olivine domains associated with the development of antigorite vein networks. Pseudomorphs after orthopyroxene consist of secondary clinopyroxene (S-Cpx) + tremolite (Tr) ± [secondary olivine (S-Ol) + antigorite (Atg)] whereas the primary clinopyroxene (P-Cpx) is almost unaltered. The pseudomorphs after Opx are rarely cut by Atg veins. The mineral occurrences indicate two main stages of mantle alteration: (1) Opx replacement (Ca-metasomatism) and (2) Atg formation induced by Si-bearing fluid infiltration (i.e., the main hydration event), followed by low-temperature (T) alteration that formed lizardite, chrysotile, and brucite. The mineralogical sequence (S-Cpx + Tr ± S-Ol ± Atg) related to Opx replacement can be explained by replacement at 550–650 °C (assuming a pressure of 1.0–2.0 GPa), which is broadly consistent with temperatures experienced by eclogites in the Chandman area during exhumation. Atg in P-Ol domains could have formed at lower temperatures (<500 °C; assuming a pressure of 1.0–2.0 GPa). Mass balance calculations show that Opx replacement was characterized by gains of Ca and a small amount of H2O, whereas Ol hydration was characterized by gains of Si and H2O. A modeled slab-derived fluid, which was calculated to be in equilibrium with basaltic crustal rocks, indicates the time-integrated fluid flux required for Ca metasomatism of the Chandman meta-peridotite body, with an assumption of the alteration thickness of L = 1000 m, was 0.18–1.5 × 106 m3 fluid m−2 rock, whereas the time-integrated fluid flux required for Si metasomatism was 0.3–1.7 × 103 m3 fluid m−2 rock, which is 102–103 lower than that of the Ca metasomatism. The characteristics of the Chandman meta-peridotite body suggest that: (1) the alteration type and trapped elements in the mantle derived from slab-derived fluids vary with temperature and local Si activity; and (2) intense fracture networks facilitated extensive serpentinization related to the Si metasomatism.

Prospective assessment of the associated minerals complex in the Konksky and Bilozersky iron ore districts from the Middle-Dniprean mega-block of the Ukrainian shield

Purpose.To determine the material composition, formational types and justify the prospects for the development of metallic and non-metallic minerals complex accompanying ore occurrences and iron deposits in the Konksky and Belozersky iron ore regions of the Middle Dnieper megablock of the Ukrainian Shield. Methods.In the process of carrying out research tasks, traditional methods of studying the material composition of minerals were used - petrographic, mineragraphic, interpretation of X-ray diffraction, thermal, and chemical analyzes were carried out. An ore formation analysis of ore occurrences of minerals accompanying iron in the Konksky and Belozersky iron ore regions was carried out. Findings.The features of the geological structure, material composition, and the influence of secondary alterations of rocks and ores on the prospects for the ore content of associated minerals accompanying iron deposits and occurrences in the study areas are characterized. The ore formation types, the genesis of ore occurrences are substantiated, and the prospects for the integrated use of raw materials accompanying iron ore deposits in the Konksky and Belozersky regions are determined. The originality.The systematic generalization of factual material regarding geological and ore formations in the Konkskaya and Belozerskaya greenstone structures, the substantiation of the possibility for using the results for metallogenic forecasting, in particular, hidden ore and the substantiation of the possibility of integrated use of the subsoil of the study areas. Practical implementation is justified by the possibility of using research results in the process of exploration and development work for a complex of associated minerals within the research area. An assessment of the prospects for the use of minerals accompanying deposits of strategically important iron ore raw materials will make it possible to ensure the comprehensive use of the subsoil of iron ore areas.

INVESTIGATION OF MINERAL DEPOSITION IN IJEDA, OSUN STATE SOUTHWESTERN NIGERIA USING GROUND MAGNETIC DATA

A geophysical ground magnetic survey method was used to investigate the presence and depths of magnetic minerals at Ijeda, Oriade Local Government area of Osun-State Nigeria. A G856AX Proton precession magnetometer was used to acquire 122 magnetic data points partitioned into 11 profiles. The station intervals and spacing were 10 m and 5 m respectively between each profile. Regional gradient and the effect of a geomagnetic reference field were removed from the observed survey data, the residual anomalies obtained were plotted against distance using Microsoft excel. Analytic Signal Method (ASM) and Peter’s Half Slope Method (PHSM) were utilized in estimating average Magnetic Source Depths. The Obtained magnetic data were plotted as 1-grid vector map, 2-D contour map and 3-D surface distribution map using surfer application to produce the qualitative analysis. The maximum and maximum magnetic intensity values obtained were 25.0 nT and -41.8 nT respectively, which suggested the area of magnetic mineral occurrences. The depths to the magnetic sources were calculated for 11 profiles and the average depth values ranged from 3.93 m ± 1.22 to 7.34 m ± 1.55 using both the ASM and the PHSM. The results showed that the study area holds a very good potential for magnetic mineral exploration.

A Spatial Data-Driven Approach for Mineral Prospectivity Mapping

Mineral prospectivity mapping is a crucial technique for discovering new economic mineral deposits. However, detailed knowledge-based geological exploration and interpretations generally involve significant costs, time, and human resources. In this study, an ensemble machine learning approach was tested using geoscience datasets to map Cu-Au and Pb-Zn mineral prospectivity in the Cobar Basin, NSW, Australia. The input datasets (magnetic, gravity, faults, electromagnetic, and magnetotelluric data layers) were chosen by considering their association with Cu-Au and Pb-Zn mineralization patterns. Three machine learning algorithms, namely random forest (RF), support vector machine (SVM), and maximum-likelihood (MaxL) classification, were applied to the input data. The results of the three algorithms were ensembled to produce Cu-Au and Pb-Zn prospectivity maps over the Cobar Basin with improved classification accuracy. The findings demonstrate good agreement with known mineral occurrence points and existing mineral prospectivity maps developed using the weights-of-evidence (WofE) method. The ability to capture training points accurately and the simplicity of the proposed approach make it advantageous over complex mineral prospectivity mapping methods, to serve as a preliminary evaluation technique. The methodology can be modified with different datasets and algorithms, facilitating the investigations of mineral prospectivity in other regions and providing guidance for more detailed, high-resolution geological investigations.

Comparative Study of Random Forest and Support Vector Machine Algorithms in Mineral Prospectivity Mapping with Limited Training Data

This paper employs two data-driven methods, Random Forest (RF) and Support Vector Machines (SVM), to develop mineral prospectivity models for an epithermal Au deposit. Four distinct models are presented for comparison: one employing RF and three using SVM with different kernel functions—namely linear, Radial Basis Function (RBF), and polynomial. The analysis leverages a compact training dataset, encompassing just 20 deposits, with deposit and non-deposit locations chosen from known mineral occurrences. Fourteen predictor maps are constructed based on the available data and the exploration model. The findings indicate that RF is more stable and robust than SVM, regardless of the kernel function implemented. While all SVM models outperformed the RF model in terms of classification capability on the training dataset achieving an accuracy exceeding 89% versus 78% for the RF model, the success rate curves suggest superior predictive abilities of RF over SVM models. This implies that the SVM models may be overfitting the training data due to the limited quantity of training deposits.

Brief historical review of the geological cartography in Ecuador.

Since 1892, seven versions of the national geological map of the Republic of the Ecuador have been published. In 1892, Dr. Theodor Wolf, of the German Scientific Mission, published the 1st map which included a preliminary geomorphological description. Later, Dr. Walther Sauer with the support of the Universidad Central del Ecuador (Central University of Ecuador), published a 2nd version in 1950, and then an update in 1970, both included oil wells information. In 1969, the Servicio Nacional de Geología y Minería del Ecuador (National Service of Geology and Mining of Ecuador), and Institut Français du Pétrole (French Petroleum Institute), published the 3rd version which included a mineralogical index. The 4th version was developed by the Dirección General de Geología y Minas del Ecuador (General Directorate of Geology and Mines of Ecuador) and Institute of Geological Sciences &amp; Natural Environment Research Council, and was published in 1982, it included a geological model from a plate tectonics approach. Later, in 1993, the Corporación de Desarrollo e Investigación Geológico Minero y Metalúrgica del Ecuador (Geological, Mining and Metallurgical Research and Development Corporation of Ecuador) and the British Geological Survey published a 5th version, which included an overview of mineral occurrences on the Ecuadorian Andes. On the 21st. century, in 2001 was published the 6th version, that consisted of a reviewed national geological map, which included data transferring to the geographical information system ArcGis. Ultimately in 2017, the Instituto Nacional de Investigación Geológico Minero Metalúrgico (National Institute of Geological-Mineral-Metallurgical Research), published the 7th version, incorporating the last updated geological results of previous campaigns. Every version contributed to the understanding of the regional geodynamic framework. Nevertheless, in the last two decades, informal coding of units for the geological cartography, thrived, involving a lack of characterization and descriptions of representative outcrops, along with uncertainties on geochronological control for newly mappable defined units, reduce reliability on the national geological cartography, increasing the uncertainties for the understanding the regional geodynamic framework.

The deep rare metal metallogenic characteristics of the Jiajika lithium polymetallic deposit in Sichuan Province, China: Revealed by the Jiajika Scientific Drilling

Jiajika, located in the Songpan–Ganzi orogenic belt in western Sichuan Province, is the largest pegmatite-type lithium polymetallic deposit in China. Nanjing University has completed a 3211.21 m scientific drilling (JSD-1) in the Jiajika lithium polymetallic deposit. Pegmatite samples from core of this hole were investigated with the aim of decreasing the bottleneck of upstream exploration and development of lithium resources. Base on the JSD-1 drill core, the pegmatite is poorly zoned, but mineral assemblages reflect a gradual evolution from bottom to top. The dominant feldspar in pegmatites evolve from microcline to albite, and the content of biotite decreases. Muscovite and tourmaline are present in the pegmatite at various depths. Spodumene is the only primary lithium mineral observed in the drill core samples, and is present at 1123 m to 56 m, especially near the surface in albite-spodumene pegmatites. U–Pb dating of columbite in pegmatites, indicate that the main ore-forming age of Jiajika pegmatites is 213.0 ± 1.6 Ma. In addition to lithium, beryllium, niobium and tantalum elements are also enriched in the drill core. Beryllium is dominantly contained in beryl and occurs mainly in pegmatites at depths of 863 m to 56 m. Niobium and tantalum are mainly enriched in columbite-group minerals, and can also occur in Nb–Ta-rich rutile associated biotite. Columbite-group minerals were observed at depths of 1728 m to 56 m. An addition intersection of columbite-group minerals mineralization occurred at a depth of 3186 m. U–Pb dating of the deeper occurrence of columbite minerals yielded a mineralization age of 190.6 ± 2.5 Ma. There are variable concentrations of lithium in muscovite, tourmaline and beryl in the drill core. However, there is a clear negative correlation of lithium concentrations with the depth, indicating the progressive lithium enrichment in the granitic magma. Although the main rare metal mineralization of Jiajika occurred at 213.0 ± 1.6 Ma, another niobium and tantalum mineralization event (190.6 ± 2.5 Ma) in-depth, which is discovered for the first time in this area, deserves also further attention.

A newly-developed multi-algorithm integration technique for mapping the potentially mineralized alteration zones

The present work introduces a newly-developed mathematical-based Multi-Algorithm Integration (MAI) technique, GIS weighted overlay model, and field investigations for delineating the potentially mineralized alteration zones. The introduced technique was tested on Semna area in Egypt as a case study. Three different algorithms were utilized to map the abundance of six alteration indicator minerals. The introduced MAI technique enabled combining the outputs of the utilized mapping algorithms allowing the delineation of only the localities that were successfully mapped as the potential for alteration zones occurrence by all the three algorithms together. Localities delineated by only one or even two techniques are not included in the output of the MAI technique, giving rise to a higher accuracy than that of individual techniques. The structural linear features were automatically depicted from a hill-shade image generated from a high-accuracy Digital Elevation Model (DEM). A Geographic Information System (GIS) Weighted Overlay Model (WOM) was then implemented to integrate the alteration maps resulting from the MAI technique with the density map of lineaments. A final hydrothermal-related mineralization potentiality map was obtained and validated through fieldwork and spectral analyses for confirming the occurrence of alteration indicator minerals. Samples were collected from the delineated potentially mineralized localities. The spectral signatures of the collected samples were measured, and spectral analyses were performed to reveal the identity of the existing alteration minerals. Various index alteration minerals were recorded in the measured samples including; kaolinite, montmorillonite, sericite, chlorite, carbonates (dolomite), and iron oxides/hydroxide minerals.

Assessment of image ratio technique: Targeting structural features and mineralization characteristics in the southwestern part of the Sokoto Basin in Nigeria using Landsat 8 imagery

Landsat 8 used multispectral images to map surface structures and validate the existence of suspected mineral alteration zones in the southwestern part of the Sokoto Basin in Nigeria. The area falls within contrasting sedimentary, metasediment, metamorphic, and older granitoid lithologies. The processing and analysis of the Landsat 8 imagery involving false color composite (FCC), band ratio, and principal component analysis (PCA) were implemented in the visible near-infrared and short-wave infrared bands of Landsat 8. PCA highlighted areas with high concentrations of clay minerals and iron oxides using RGB composite bands 7, 5, and 3. Moreover, PCA enhanced iron oxide, hydroxyl-bearing minerals, and likely prospective zones mainly constrained in amphibolite, phyllite, quartzite, and alluvial deposits that have undergone metamorphism and metasedimentation within Yegiwa and Kurege. It identified iron ore and clay mineral alteration, suggesting the occurrence of manganese, goethite, and carbonate minerals around Maburo and Derrena. The observed alteration zones and their associated quartz veins are usually consistent with the main NE–SW provincial structural trend dipping to the northwest zone. However, field verification validates rock units typically consisting of muscovite, hornblende, manganite, tourmaline, quartz vein, and granitic rocks. Accordingly, remote-sensing and field verification served as a guide for future subsurface structural investigation and in-depth geophysical exploration.

Structural framework and timing of the Pahtohavare Cu ± Au deposits, Kiruna mining district, Sweden

Abstract. As part of the larger mineral systems approach to Cu-bearing mineralization in northern Norrbotten, this study utilizes structural geology to set the classic Pahtohavare Cu ± Au deposits into an up-to-date tectonic framework. The Pahtohavare Cu ± Au deposits, situated only 5 km southwest of the Kiirunavaara world-class iron oxide–apatite (IOA) deposit, have a dubious timing, and their link to IOA formation is not constrained. The study area contains both epigenic Cu ± Au (Pahtohavare) and iron oxide–copper–gold (IOCG; Rakkurijärvi) mineral occurrences which are hosted in bedrock that has been folded and bound by two shear zones trending northeast to southwest and northwest to southeast to the east and southwest, respectively. Structural mapping and petrographic investigation of the area reveal a noncylindrical, SE-plunging anticline. The cleavage measurements mirror the fold geometry, which characterizes the fold as F2 associated with the late phase of the Svecokarelian orogeny. Porphyroclasts with pressure shadows, mylonitic fabrics, and foliation trails in porphyroblasts indicate S0/S1 is a tectonic fabric. The epigenetic Pahtohavare Cu ± Au mineralization sits in brittle–ductile structures that cross-cut an earlier foliation and the F2 fold, indicating that the timing of the deposits occurred syn- to post-F2 folding, at least ca. 80 Myr after the Kiirunavaara IOA formation. A 3D model and cross-sections of the Pahtohavare–Rakkurijärvi area and a new structural framework of the district are presented and used to suggest that the shear zones bounding the area are likely reactivated early structures that have played a critical role in ore formation in the Kiruna mining district.

The Characteristics of Doğanşehir (Malatya-Turkey) Bauxite Mineralization in the Eastern Taurus Orogenic Belt Using Scanning Electron Microscopy (SEM)

The Taurus Orogenic Belt in Turkey is a prominent tectonic zone where significant occurrences of bauxite mineralization are observed. The bauxite deposits in Doğanşehir, located in Malatya, Turkey, are found as extensive bodies and lenses within the carbonate rocks of the Permian-Triassic Malatya Metamorphics, situated in the Eastern Taurus Orogenic Belt. The geological foundation of this region consists primarily of lithologies attributed to the Malatya Metamorphics. This unit mainly comprises schists, calc-schists, and marble, overlain by the Berit Metaophiolite of the Late Cretaceous-Eocene, the Maden Complex of the Eocene, the Doğanşehir Granitoid of the Early-Middle Eocene, and the Plio-Quaternary cover sedimentary units. Bauxite mineralization of oolitic and pisolitic nature is present within the Permian-Triassic carbonate rocks of the Malatya Metamorphics. These mineralizations occur in carbonate rocks containing fossils and are observed in the form of lens-shaped bodies. The bauxite lenses are covered by relatively thin, intermediate layers of Permian-Triassic carbonate rocks of the Malatya Metamorphics. With the advancement of technology, Scanning Electron Microscopy (SEM) has been utilized to analyze bauxite ores and determine the presence of elements within their crystal lattice structure. The point analysis and mapping technique were employed to identify the elements that might be present within the crystal lattice structure of the bauxite ores. SEM analysis of the samples using the mapping method revealed the distribution of elements such as Fe, Ti, Si, Al, and O, both before and after activation. The images indicate that bauxite exhibits a wide grain distribution, both below and above 50 µm. The elemental spectrum diagram demonstrates the presence of O, Al, and Si in the sample, and the detection of Fe, Ti, C, K, and Mg as well. By employing SEM analysis and the mapping method on the same samples, the distribution of Fe, Ti, Si, Al, and O elements within the structure was examined before and after activation. The images reveal that the elements Al, O, and Si display high density in specific regions before activation but show a more uniform distribution and similar structures after activation. Fe, Mg, and K exhibit a similar distribution pattern, while Ti and C exhibit different characteristics.

Boron-bearing skarn-magnetite mineralization of the Mingbulak ore field, Eastern Uzbekistan

Spatial distribution of skarn-magnetite deposits in the Tien Shan region is closely related to gabbroid magmatism that accompanies wide fault zones bordering the South Tien Shan folded system from the north and south and extending as a latitudinal belt towards the Middle and Southwestern Tien Shan.Studies fulfilled during recent decades in the Karzhantau Ridge area have quite clearly demonstrated its gold-copper-bismuth metallogenic specialization with the leading role of gold. The most promising position is characteristic of the Aktash group ore occurrences (Aktam-I, Aktam-II, and Yuzhnoe).Within the studied Mingbulak area of Karzhantau, the most widely distributed are mineral occurrences of iron ore, lead and zinc, gold, and copper, and less developed boron-bearing, tungsten, and fluorite ones. Most of the mineral occurrences in the area formed as a result of magmatic-hydrothermal activity and are confined to fault zones characterized by long duration and complexity of the formation. The mineralization is usually localized in the crush zones and feathering fractures of the faults. The skarn type includes ore occurrences of iron, a metal that is currently strongly deficient for mining enterprises in the Tashkent region.