Mineral Occurrences Research Articles

Petrology and Petrochemistry of Basement Rocks in Ila Orangun Area, Southwestern Nigeria

From field studies, six (6) lithological units were identified to be common around the study area which includes quartzites, granites, granite gneiss, porphyritic granites, amphibolite and pegmatites. The results of petrographical analyses show the mineral assemblages of the various rock types in the area which include quartzites as containing quartz, biotite, muscovite and myrmekite. Granite gneiss contains quartz, biotite, orthoclase, myrmekite, microcline, nepheline, hornblende and plagioclase. Pegmatite contains quartz, myrmekite, plagioclase, hornblende, microcline and muscovites. Porphyritic granites were observed to contain quartz, biotite, microcline, orthoclase and tourmaline. Granite contains quartz, biotite, hornblende, plagioclase and orthoclase while Amphibolite schist contains quartz, biotite, hornblende and muscovites. For the purpose of this study twenty (20) pulverized rock samples were taken to the laboratory for geochemical analysis with their results used in the classification as well as suggest the geochemical attributes of the rocks. Geochemical results obtained and interpreted using various geochemical plots or discrimination plots all classified the rocks in the area as belonging to both the peralkaline metaluminous and peraluminous types. Results for the major oxides ratios produced for Na2O/K2O, Al2O3/Na2O + CaO + K2O and Na2O + CaO + K2O/Al2O3 show the excess of alumina, Al2O3 over the alkaline Na2O +CaO +K2O thus suggesting peraluminous rocks. While the excess of the alkali over the alumina suggests the peralkaline metaluminous rock type. The results of correlation coefficient show a perfect strong positive correlation which shows that they are of same geogenic sources while negative correlation coefficient values indicate a perfect weak negative correlation suggesting that they are of heterogeneous geogenic sources. The result of the factor analysis show the elemental association of the trace elements and heavy metals represented as variables in the statistical analysis. Hence, establishing the elemental association of Component 1 as consisting of Ag-As-Ba-Cd-Co, Component 2 as Cr-Cu-Ni, Component 3 as Pb-Rb, Component 4 as Zn-Fe-V and Component 5 as U-Mn. Component 1 suggest the possibilities of sulphide and gold mineralization. Component 2 suggesting pathfinder elements while Components 3, 4 and 5 suggest weathered or dispersed elements. Hence, the occurrence of heavy metallic minerals in the rocks will serve huge economic significance with focus on the pegmatites in the area.

Enrichment characteristics and metallogenic significance of rare elements in Zambia: Based on 1:1,000,000 geochemical mapping

The Sino–Zambian Cooperation Project has filled the gap in Zambia national‐scale geochemical mapping, providing basic geochemical guarantees for Zambia's basic geology, mineral development, environmental protection, agricultural production and other aspects. This article aims to reveal the distribution characteristics of its rare elements (Li, Be, Nb, Rb, Sr). The median value of Li, Be, Nb, Rb and Sr is 4.94 × 10−6, 0.65 × 10−6, 7.50 × 10−6, 33.00 × 10−6 and 21.90 × 10−6, respectively. The median and average values of the Irumide Belt, Zambezi Belt, Choma‐Kalomo Block and Hook Granite Complex are higher than other tectonic belts, showing that rare elements are enriched in those areas. The distribution of element anomaly areas is mainly related to the distribution characteristics of granite type rare metal mineralization occurrences, and a small number of anomaly areas are controlled by salt lake brine‐type mineralization occurrences. A total of five rare metal geochemical anomalies have been delineated respectively based on the 85% cumulative percentage of rare elements (Li, Be, Nb, Rb, Sr). The metallogenic prospective area delineated based on the comprehensive anomaly area of rare elements will provide an important reference for searching for rare metal deposits in this area.

Fertility Indicators for Porphyry-Cu-Au+Pd±Pt Deposits: Evidence from Skouries, Chalkidiki Peninsula, Greece, and Comparison with Worldwide Mineralizations

The research interest for many authors has been focused on the origin, recovery, and exploration of critical metals, including platinum-group elements (PGEs), with the aim of finding new potential sources. Many giant porphyry Cu deposits are well known around the Pacific Rim, in the Balkan–Carpathian system, Himalayas, China, and Malaysia. However, only certain porphyry Cu-Au deposits are characterized by the presence of significant Pd and Pt contents (up to 20 ppm). This contribution provides new analytical data on porphyry-Cu-Au±Pd±Pt deposits from the Chalkidiki Peninsula and an overview of the existing geochemical characteristics of selected porphyry-Cu deposits worldwide in order to define significant differences between PGE-fertile and PGE-poor porphyry-Cu intrusions. The larger Mg, Cr, Ni, Co, and Re contents and smaller LILE elements (Ba and Sr) in fertile porphyry-Cu-Au-(PGE) reflect the larger contribution from the mantle to the parent magmas. In contrast, the smaller Mg, Cr, Ni, Co, and Re contents and larger Ba and Sr in PGE-poor porphyry-Cu-Mo deposits from the Chalkidiki Peninsula (Vathi, Pontokerasia, and Gerakario) and Russia–Mongolia suggest the presence of parent magmas with a more crustal contribution. Although there is an overlap in the plots of those elements, probably due to the evolution of the ore-forming system, consideration of the maximum contents of Mg, Cr, Ni, and Co is proposed. Magnetite which separated from the mineralized Skouries porphyry of Greece showed small negative Eu anomalies (Eu/Eu* ≥ 0.55), reflecting a relatively high oxidation state during the cooling of the ore-forming system. The relatively high, up to 6 ppm (Pd+Pt), and low Cr content towards the transition from the porphyry to epithermal environment, coupled with the occurrence of Pd, Te, and Se minerals (merenskyite, clausthalite), and tetrahedrite–tennantite in fertile porphyry Cu deposits (Elatsite deposit, Bulgaria), reflect a highly fractionated ore-forming system. Thus, in addition to the crustal and mantle recycling, metasomatism, high oxidation state, and abundant magmatic water, other factors required for the origin of fertile porphyry-Cu deposits are the critical degree of mantle melting to release Pt and Pd in the ore-forming fluids and the degree of fractionation, as reflected in the mineral chemistry and geochemical data.

Prediction of gold mineralization zones using spatial techniques and geophysical data: A case study of the Josephine prospecting licence, NW Ghana

In this study, predictive models that characterize gold potential zones within the Josephine Prospecting Licence (PL) Area of Northwestern Ghana have been created by data-driven methods comprising frequency ratio and information value. These predictive models were evaluated using known locations of gold (Au) occurrence datasets and compared to each other. The mineral prospectivity models (MPMs) of gold occurrence areas within the Josephine PL Area were constructed by determining the spatial correlation between known locations of Au occurrences and eight mineralization related factors. The locations of these known Au occurrences, which characterize regions of anomalously high Au geochemical concentration and regions of previous or ongoing artisanal mining operations were identified by using geographic positioning systems (GPS). Eight mineralization related factors (geoscientific thematic layers) over the entire study area composed of analytic signal, lineament density, uranium-thorium ratio, uranium, potassium-thorium ratio, potassium, reduction-to-equator and geology were used to generate the MPMs. The predictive capacity of each of the MPMs generated was determined by employing the area under the receiver operating characteristics curve (AUC). The AUC score obtained for the predictive models produced based on the information value and the frequency ratio approaches were respectively 0.794 and 0.815. The AUC scores generated indicate that the MPMs produced are good predictive models (with an AUC greater than 0.7) and can therefore assist in narrowing down the highly prospective zones of mineral occurrences within the study area. However, the overall predictive potential of the frequency ratio approach was better than the model produced by the information value approach.

Recognizing Geochemical Anomalies Associated with Mineral Resources Using Singularity Analysis and Random Forest Models in the Torud-Chahshirin Belt, Northeast Iran

Identifying the local geochemical anomalies from stream sediment samples is challenging in regional-scale exploration programs. For this purpose, some robust and reliable techniques must be applied to distinguish the geochemical targets from the background values. In this research, a procedure of several tools, including singularity mapping (SM), random forests (RF), success-rate curves, and the t-Student method, were employed to analyze the geochemical anomalies within the intrusive-plutonic Torud-Chahshirin belt (TCB), northeast Iran. In this regard, the success-rate curves were initially applied to extract efficient geochemical signatures. Then, singularity analysis was used on the selected geochemical elements (Au, Cu, Pb, and Zn), which were transformed via centered log-ratio (clr) transformation. In the next step, due to the complexity of the ore-forming processes in the TCB, the structural factors (e.g., fault intersection and faults with different orientations) were determined. Based on the success-rate curves, NE-trending faults and fault density were distinguished as critical structural criteria. Afterward, the RF model as a robust machine learning algorithm was executed on the four efficient SM-based geochemical layers and two efficient structural factors. The anomaly map derived by the RF model (Accuracy = 98.85% and Error = 1.15%) illustrates a very high relationship with Cu ± Au mineral occurrences. Therefore, the RF algorithm assisted by the singularity method is more trustworthy for highlighting the weak geochemical prospectivity areas in the TCB.

Process Mineralogy Assisted Iso-Floatability of Copper-Zinc-Lead Minerals from Iron Tailings at Marcona Iron Ore Mine

ABSTRACT Process mineralogy was applied to design the process circuit of magnetite tailings containing copper, lead and zinc from Marcona Iron Ore Mine. Mineralogy parameters, such as mineral composition, occurrence, and grain size distribution of the main minerals, were investigated in detail. The results showed that the main valuable elements including 41.40 wt.% iron, 0.064 wt.% copper, 0.38 wt.% lead, and 0.96 wt.% zinc, were primarily in the occurrence of magnetite, chalcopyrite, galena, and sphalerite, respectively. In addition, complex interlocking relationships were observed among the copper-zinc-lead minerals. Therefore, a fine grinding process was required for mineral liberation, followed by magnetic separation for magnetite collection. Iso-floatability flotation process was further applied to the magnetic tailings, achieving a copper grade of 28.37 wt.% and a recovery of 25.11% in the copper concentrates. Subsequently, zinc and lead grades of 49.04% wt.% and 8.06% wt.% were obtained in the zinc-lead concentrates, with a recovery of 51.72% and 25.21%, respectively. Therefore, this study provides an available separation of copper-zinc-lead minerals from iron tailings at Marcona Iron Ore Mine based on process mineralogy, thereby giving a prior diagnosis strategy to increase the utilization efficiency of iron tailings.

Origin of Hydrothermal Barite in Polymetallic Veins and Carbonate-Hosted Deposits of the Cyclades Continental Back Arc

Abstract Polymetallic veins and breccias and carbonate-replacement ore deposits in the Cyclades continental back arc, Greece, formed from a range of fluid and metal sources strongly influenced by the dynamics of the late Mesozoic-Cenozoic Hellenic subduction system. These complexities are recorded in the isotopic signatures of hydrothermal barite. We investigated 17 mineral occurrences on four Cycladic islands and from Lavrion on the mainland. Here, barite occurs in almost all deposit types of Miocene to Quaternary age. We used a multiple isotope and geochemical approach to characterize the barite in each deposit, including mineral separate analysis of δ34S and δ18O and laser ablation-inductively coupled plasma-mass spectrometry of 87Sr/86Sr and δ34S. Barite from carbonate-hosted vein and breccia Pb-Zn-Ag mineralization on Lavrion has a wide range of δ34S (2–20‰) and δ18O (10–15‰) values, reflecting a mix of magmatic and surface-derived fluids that have exchanged with isotopically heavy oxygen in the carbonate host rock. Sulfur (δ34S = 10–13‰) and oxygen (δ18O = 9–13‰) values of barite from the carbonate-hosted vein iron and barite mineralization on Serifos are permissive of a magmatic sulfate component. Barite from epithermal base and/or precious metal deposits on Milos has δ34S (17–28‰) and δ18O (9–11‰) values that are similar to modern seawater. In contrast, barite from vein-type deposits on Antiparos and Mykonos has a wide range of δ34S (16–37‰) and δ18O (4–12‰) values, indicating a seawater sulfate source modified by mixing or equilibration of the hydrothermal fluids with the host rocks. Strontium isotope ratios of barite vary regionally, with 87Sr/86Sr ≥ 0.711 in the central Cyclades and 87Sr/86Sr ≤ 0.711 in the west Cyclades, confirming the strong influence of upper crustal rocks on the sources of fluids, Sr, and Ba in the formation of ore.

Occurrence and transformation behaviour of silicon-bearing minerals during high silicon coal combustion from Yunnan Province, China

To understand the mineralogical characteristics and transformation behaviours of silicon-bearing minerals during coal combustion, seven typical high silicon (high-Si) coals and two high-Si fly ashes generated from high-Si coal-fired power plants were chosen. The coals were first treated by a method of low temperature ashing and the float-sink test for heavy minerals separation. Subsequently, low temperature ashes (LTA), light mineral fractions (LM), heavy mineral fractions (HM), and fly ashes from coal-fired power plants were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) combined with energy spectrum analysis (EDX), X-ray fluorescence spectrometry (XRF), and simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC).The results show that The mineral compositions in the LTA and LM are almost the same and majorly composed of quartz, kaolinite, calcite, dolomite, daphnite, chlorite-serpentine, pyrite, and anatase. The mineral compositions identified in the HM are clearly different from those in the LTA and LM. Pyrite, fluorapatite, anatase, siderite, dolomite and a plenty of silicate minerals including quartz, clinochlore, daphnite, chlorite, and chamosite are found in the HM. Chlorite is a quite common mineral in the HM with different shapes, including schistose, long tetragonal prism, cylindrical, block-shaped, and near-spherical, can be identified. The minerals identified in the fly ashes from the high-Si coal-fired power plants include quartz, mullite, and hematite. The mullite in the fly ashes is derived from the transformations of quartz, kaolinite, and chlorite in the coals. The quartz in the fly ash is mainly derived from the unchanged quartz in coal and a secondary origin from the SiO2-Al2O3 phase transformation. The high-Si fly ash with the size fraction of 38.5–74 μm contains the highest SiO2 content.

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.