Search Results (27)

The Kavokta deposit in Russia contains gray and black dolomite-type nephrite, which is in high demand commercially. Although the fact that black nephrite has been found in several deposits, the reasons for its color are not well understood. The present study aims to identify the localization and mineral composition of gray and black nephrite, and to determine the reasons for its dark coloration. The mineral composition of nephrite was studied using a scanning electron microscope with energy-dispersive microanalysis (SEM-EDX) and X-ray phase analysis. Also, the isotopic composition of carbon in graphite in nephrite and in carbonates associated with nephrite in the surrounding strata was determined. The gray–black color in most samples from the southeastern part of the Kavokta deposit (lodes 17 and 28 of the nephrite-bearing zone 4 of the Medvezhy section and lode 6-1 of the nephrite-bearing zone 6 of the Levoberezhny section) is due to the presence of graphite. Syngenetic graphite formed both by the organic matter buried in dolomites and by the decomposition of carbon dioxide that is released during decarbonation under the influence of deep-seated hydrogen. The color of nephrite also depends on the iron content, changing from white to light green as the iron content increases. The gray color of tremolite–diopside nephrite is due to the development of chlorite aggregates that replace diopside and/or tremolite. The gray-green to black color of the nephrite in the northwestern part of the Kavokta deposit (lode 1 of the nephrite-bearing zone 1 of the Prozrachny section) is due to the high iron content in the tremolite–actinolite at the contact with the epidote–tremolite skarn formed after amphibolite. The identified patterns of black nephrite localization can be used in the process of geological exploration of similar deposits elsewhere in Russia and abroad. Full article

Skarn-type iron ore is economically significant, and numerous skarn ore deposits have been identified in the North China Craton. The newly discovered orbicular diorite in this region is distinguished from other analogous rocks due to the accumulation of large magnetite particles, which may shed new light on the genesis of this ore type. The magnetite in different parts of the orbicular structure exhibits distinct compositional differences. For example, magnetite at the edge has a small particle size (200 μm) and is associated with the minerals plagioclase and hornblende, indicating that it crystallized from normal diorite magma. By contrast, magnetite in the core has a relatively large particle size (>1000 μm), is associated with apatite and actinolite, and contains apatite inclusions as well as numerous pores. The size of magnetite in the mantle falls between that of the edge and the core. The syngenetic minerals of magnetite in the mantle include epidote and plagioclase. The magnetites in the cores of orbicules have a higher content of Ti, Al, Ni, Cr, Sc, Zn, Co, Ga, and Nb than those in the rim. The δ⁵⁶Fe value of the core magnetite (0.46‰–0.78‰) is much higher than that of the mantle and rim magnetite in orbicules. Moreover, the δ⁵⁶Fe value of magnetite increases as the V content of magnetite gradually decreases. This large iron isotope fractionation is likely driven by liquid immiscibility that forms iron-rich melts under high oxygen fugacity. The reaction between magma and carbonate xenoliths (Ca, Mg)CO₃ during magma migration generates abundant CO₂, which significantly increases the oxygen fugacity of the magmatic system. Under the action of CO₂ and other volatile components, liquid immiscibility occurs in the magma chamber, and Fe-rich oxide melts are formed by the melting of carbonate xenoliths. Iron oxides (Fe₃O₄/Fe₂O₃₎ will crystallize close to the liquidus due to high oxygen fugacity. These characteristics of magnetite in the Tanling orbicular diorite (Wuan, China) indicate that diorite magma reacts with carbonate xenoliths to form “Fe-rich melts”, and skarn iron deposits are probably formed by the reaction of intermediate-basic magma with carbonate rocks that generate such “Fe-rich melts”. A possible reaction is as follows: diorite magma + carbonate → (magnetite-actinolite-apatite) + garnet + epidote + feldspar + hornblende + CO₂↑. Full article

Although skarn-type deposits represent significant hosts for Co resources, the distribution patterns and enrichment mechanisms of associated Co resources within these deposits have not been systematically investigated. This study summarizes relevant data on Co resources from representative skarn-type deposits in China to comparatively reveal the grade and reserve characteristics, spatiotemporal distribution patterns, and coupled enrichment mechanisms of Co across three principal skarn mineralization subtypes: iron-, copper-, and lead–zinc polymetallic-dominated deposits. Studies demonstrate that Fe-dominated skarn-type cobalt deposits exhibit widespread distribution, high Co grades (100–2000 ppm), and abundant Co reserves (4000–32,000 t), demonstrating significantly superior Co resource potential compared to Cu-dominated (Co grades: 20–200 ppm, Co reserves: 3000–10,000 t) and Pb-Zn polymetallic-dominated (Co grades: 140–853 ppm, Co reserves: approximately 3000 t) subtypes. In these skarn-type cobalt deposits, cobalt is mainly hosted in sulfide minerals. Influenced by tectonic settings, magmatic activity, and hydrothermal fluid evolution, associated Co resources in these skarn-type deposits exhibit both regional zonation and stage-specific differential enrichment patterns. In the formation of skarn-type cobalt deposits, mantle-derived magmas play a critical role in the pre-enrichment of Co. The injection of mafic magmas, assimilation of evaporite sequences, and the dissolution–reprecipitation mechanism of hydrothermal fluids collectively promote the re-enrichment of Co during magmatic evolution. These findings provide a theoretical foundation for targeted exploration, sustainable development, and comprehensive utilization of associated Co resources in skarn-type deposits. Full article

In the absence of appropriate tools and a knowledge base for exploring high-grade metamorphic terrains, felsic gneiss complexes at granulite facies have long been considered barren and have remained undermapped and understudied. This was the case of the Bondy gneiss complex in the southwestern Grenville Province of Canada which consists of 1.39–1.35 Ga volcanic and plutonic rocks metamorphosed under granulite facies conditions at 1.19 Ga. Iron oxide–apatite and Cu-Ag-Au mineral occurrences occur among gneisses rich in biotite, cordierite, garnet, K-feldspar, orthopyroxene and/or sillimanite-rich gneisses, plagioclase-cordierite-orthopyroxene white gneisses, magnetite-garnet-rich gneisses, garnetites, hyperaluminous sillimanite-pyrite-quartz gneisses, phlogopite-sillimanite gneisses, and tourmalinites. Petrological and geochemical studies indicate that the precursors of these gneisses are altered volcanic and volcaniclastic rocks with attributes of pre-metamorphic Na, Ca-Fe, K-Fe, K, chloritic, argillic, phyllic, advanced argillic and skarn alteration. The nature of these hydrothermal rocks and the ore deposit model that best represents them are further investigated herein through lithogeochemistry. The lithofacies mineralized in Cu (±Au, Ag, Zn) are distinguished by the presence of garnet, magnetite and zircon, and exhibit pronounced enrichment in Fe, Mg, HREE and Zr relative to the least-altered rocks. In discrimination diagrams, the metamorphosed mineral system is demonstrated to exhibit the diagnostic attributes of, and is interpreted as, a metasomatic iron and alkali-calcic (MIAC) mineral system with iron oxide–apatite (IOA) and iron oxide copper–gold (IOCG) mineralization that evolves toward an epithermal cap. This contribution demonstrates that alteration facies diagnostic of MIAC systems and their IOCG and IOA mineralization remain diagnostic even after high-grade metamorphism. Exploration strategies can thus use the lithogeochemical footprint and the distribution and types of alteration facies observed as pathfinders for the facies-specific deposit types of MIAC systems. Full article

Metasomatic iron and alkali-calcic (MIAC) mineral systems form district-scale metasomatic footprints in the upper crust that are genetically associated with iron oxide–apatite (IOA), iron oxide and iron sulfide copper–gold (IOCG, ISCG), skarn, and affiliated critical and precious metal deposits. The development of MIAC systems is characterized by series of alteration facies that form key mappable entities in the field and along drill cores. Each facies can precipitate deposit types specific to the facies or host deposits formed at a subsequent facies. Defining the spatial and temporal relations between alteration facies and host rocks as well as with pre, syn, and post MIAC magmatic, tectonic, and mineralization events is essential to understanding the evolution of a MIAC system and to evaluating its overall mineral prospectivity. This paper proposes an ontology for MIAC systems that frames the key characteristics of the main alteration facies described and links it to a taxonomy and descriptive lexicons that allow the user to build an efficient data collection system tailored to the description of MIAC systems. The application developed by the Geological Survey of Canada for collecting field data is used as an example. The data collection system, including the application for collecting field data and the lexicons, are applicable to regional- and deposit-scale geological mapping as well as to drill core logging. They respond to the need for the metallogenic mapping of mineral systems and the development of more robust mineral prospectivity maps and exploration strategies for the discovery of critical and precious metal resources in MIAC systems. Full article

The Huanggang iron-tin deposit, located in the southern Greater Khingan Range, is one of the largest Fe-Sn deposits in Northern China (NE China). Iron-tin mineralization occurs mainly in the contact zone between granitoid intrusions and the marble of the Huanggang and Dashizhai formations. Six mineralization stages are identified: (I) anhydrous skarn, (II) hydrous skarn, (III) cassiterite-quartz-calcite, (IV) pyrite-arsenopyrite-quartz-fluorite, (V) polymetallic sulfides-quartz, and (VI) carbonate ones. Fluid inclusions (FIs) analysis reveals that Stage I garnet and Stage II–III quartz host liquid-rich (VL-type), vapor-rich two-phase (LV-type), and halite-bearing three-phase (SL-type) inclusions. Stage IV quartz and fluorite, along with Stage V quartz, are dominated by VL- and LV-type inclusions, while Stage VI calcite contains exclusively VL-type inclusions. The FIs in Stages I to VI homogenized at 392–513, 317–429, 272–418, 224–347, 201–281, and 163–213 °C, with corresponding salinities of 3.05–56.44, 2.56–47.77, 2.89–45.85, 1.39–12.42, 0.87–10.62, and 4.48–8.54 wt% NaCl equiv., respectively. The H–O–C isotopes data imply that fluids of the anhydrous skarn stage (δD = −101.2 to −91.4‰, δ¹⁸O_H2O = 5.0 to 6.0‰) were of magmatic origin, the fluids of hydrous skarn and oxide stages (δD = −106.3 to −104.7‰, δ¹⁸O_H2O = 4.3 to 4.9‰) were characterized by fluid mixing with minor meteoric water, while the fluids of sulfide stages (δD = −117.4 to −108.6‰, δ¹⁸O_H2O = −3.4 to 0.3‰, δ¹³C_V-PDB= −12.2 to −10.9‰, and δ¹⁸O_V-SMOW = −2.2 to −0.7‰) were characterized by mixing of significant amount of meteoric water. The ore-forming fluids evolved from a high-temperature, high-salinity NaCl−H₂O boiling system to a low-temperature, low-salinity NaCl−H₂O mixing system. The garnet U-Pb dating constrains the formation of skarn to 132.1 ± 4.7 Ma (MSWD = 0.64), which aligns, within analytical uncertainty, with the weighted-mean U−Pb age of zircon grains in ore-related K-feldspar granite (132.6 ± 0.9 Ma; MSWD = 1.5). On the basis of these findings, the Huanggang deposit, formed in the Early Cretaceous, is a typical skarn-type system, in which ore precipitation was principally controlled by fluid boiling and mixing. Full article

This study investigates the mineral chemistry and iron isotope composition of the Pertek Fe-skarn deposit in the Eastern Taurides, Turkey, to elucidate skarn formation and ore genesis through chemical and isotopic parameters. The deposit consists of substantial and dispersed magnetite ores formed by the intrusion of a dioritic suite into marbles. Mineral assemblages, including hematite, goethite, andradite garnet, hedenbergite pyroxene, calcite, and quartz, exhibit compositional variations at different depths within the ore body. Magnetite is commonly associated with hematite, goethite, garnet, pyroxene, calcite, and quartz. Extensive LA–ICP–MS analysis of magnetite chemistry reveals elevated trace element concentrations of titanium (Ti), aluminum (Al), vanadium (V), and magnesium (Mg), distinguishing Pertek magnetite from low-temperature hydrothermal deposits. The enrichment of Ti (>300 ppm) and V (>200 ppm), along with the presence of Al and Mg, suggests formation from high-temperature hydrothermal fluids exceeding 300 °C. Discriminant diagrams, such as Al+Mn versus Ti+V, classify Pertek magnetite within the skarn deposit domain, affirming its medium- to high-temperature hydrothermal origin (200–500 °C), characteristic of skarn-type deposits. Magnetite thermometry calculations yield an average formation temperature of 414.53 °C. Geochemical classification diagrams, including Ni/(Cr+Mn) versus Ti+V and TiO₂-Al₂O₃-MgO+MnO, further support the skarn-type genesis of the deposit, distinguishing Pertek magnetite from other iron oxide deposits. The Fe-skarn ore samples display low total REE concentrations, variable Eu anomalies, enrichment in LREEs, and depletion in HREEs, consistent with fluid–rock interactions in a magmatic–hydrothermal system. The δ⁵⁶Fe values of magnetite range from 0.272‰ to 0.361‰, while the calculated δ⁵⁶Fe_aq values (0.479‰ to 0.568‰) suggest a magmatic–hydrothermal origin. The δ⁵⁷Fe values (0.419‰ to 0.530‰) and the calculated 10³lnβ value of 0.006397 indicate re-equilibration of the magmatic–hydrothermal fluid during ore formation. Full article

The Kaladawan iron deposit is located in the North Altyn Tagh and exhibits occurrences of iron ore bodies at the contact zone between Ordovician magmatic rocks (basalts, rhyolite, and granodiorite) and marble. However, controversy persists regarding the genetic classification and metallogenic mechanism of this deposit. Through a field investigation, single mineral in situ geochemical analysis, whole-rock geochemical analysis, and Fe isotope determination, the following conclusions are made: (1) Ti-(Ni/Cr) and (V/Ti)-Fe diagrams indicate that the magnetite from all studied rocks underwent hydrothermal metasomatism, while (Ni/(Cr + Mn))-(Ti + V) and (Ca + Al + Mn)-(Ti + V) diagrams suggest a skarn origin for these magnetites. Therefore, it can be inferred that the Kaladawan iron deposit is skarn-type. (2) The iron ore exhibits similar rare-earth-element characteristics to the altered basalt. Additionally, the altered basalts (δ⁵⁶Fe = 0.024~0.100‰) are more enriched in light Fe isotopes than the unaltered basalts (δ⁵⁶Fe = 0.129~0.197‰) at the same location, indicating that the ore-forming materials of the Kaladawan iron ore are mainly derived from basaltic rocks. (3) According to the law of mass conservation and the intermediate Fe isotopic composition of the iron ore between the granodiorite and basalt, the hydrothermal fluid for the formation of iron ores was inferred to be derived from the late intrusive granodiorite. Full article

The nephrite belt in the Altun Mountain–Western Kunlun Mountain region, which extends about 1300 km in Xinjiang, NW China, is the largest nephrite deposit in the world. The Qiemo region in the Altun Mountains is a crucial nephrite-producing area in China, with demonstrated substantial prospects for future exploration. While existing research has extensively investigated secondary nephrite deposits in the Karakash River and native black nephrite deposits in Guangxi Dahua, a comprehensive investigation of black nephrite from original deposits in Xinjiang is lacking. Margou black-toned nephrite was recently found in primary deposits in Qiemo County, Xinjiang; this makes in-depth research on the characteristics of this mine necessary. A number of technical analytical methods such as polarizing microscopy, Ultra-Deep Three-Dimensional Microscope, electron microprobe, back-scattered electron image analysis, X-ray fluorescence, and inductively coupled plasma mass spectrometry were employed for this research. An experimental test was conducted to elucidate the chemical and mineralogical composition, further clarifying the genetic types of the black and black cyan nephrite from the Margou deposit in Qiemo, Xinjiang. The results reveal that the nephrite is mainly composed of tremolite–actinolite, characterized by Mg/(Mg + Fe²⁺) ratios ranging from 0.86 to 1.0. Minor minerals include diopside, epidote, pargasite, apatite, zircon, pyrite, and magnetite. Bulk-rock rare earth element (REE) patterns exhibit distinctive features, such as negative Eu anomalies (δEu = 0.00–0.17), decreasing light REEs, a relatively flat distribution of heavy REEs, and low total REE concentrations (1.6–38.9 μg/g); furthermore, the Cr (6–21 μg/g) and Ni (2.5–4.5 μg/g) contents are remarkably low. The magmatic influence of granite appears to be a fundamental factor in the genesis of the magnesian skarn hosting Margou nephrite. The distinctive black and black cyan colors are attributed to heightened iron content, mainly associated with FeO (0.08~6.29 wt.%). Analyses of the chemical composition allow Margou nephrite to be classified as typical of magnesian skarn deposits. Full article

Apatite, as a common accessory mineral found in magmatic–hydrothermal deposits, effectively yields geochemical insights that facilitate our understanding of the mineralization process. In this research, multiple generations of magmatic and hydrothermal apatite were observed in the Hongshan porphyry–skarn Cu–Mo deposit in the Yidun Terrane in SW China. The geochemical compositions of the apatite were studied using in situ laser ablation–inductively coupled plasma mass spectrometry and an electron probe microanalysis to understand the magmatic–hydrothermal processes leading to ore formation. The apatite (Ap1a) occurs as subhedral to euhedral inclusions hosted in the phenocrysts of the granite porphyry. The Ap1b occurs later than Ap1a in a fine-grained matrix that intersects the earlier phenocrysts. Increases in F/Cl, F/OH, and F/S and decreases in ΣREE and (La/Yb)_N from Ap1a to Ap1b suggest the exsolution of a volatile-rich phase from the magma. The skarn hosts three types of hydrothermal apatite (Ap2a, Ap2b, and Ap3), marking the prograde, retrograde, and quartz–sulfide stages of mineralization, respectively. The elemental behaviors of hydrothermal apatite, including the changes in Cl, Eu, As, and REE, were utilized to reflect evolutions in salinity, pH, oxygen fugacity, and fluid compositions. The composition of Ap2a, which occurs as inclusions within garnet, indicates the presence of an early acidic magmatic fluid with high salinity and oxygen fugacity at the prograde skarn stage. The composition of Ap2b, formed by the coupled dissolution-reprecipitation of Ap2a, indicates the presence of a retrograde fluid that is characterized by lower salinity, higher pH, and a significant decrease in oxygen fugacity compared to the prograde fluid. The Ap3 coexists with quartz and sulfide minerals. Based on studies of Ap3, the fluids in the quartz–sulfide stage exhibit relatively reducing conditions, thereby accelerating the precipitation of copper and iron sulfides. This research highlights the potential of apatite geochemistry for tracing magmatic–hydrothermal evolution processes and identifying mineral exploration targets. Full article

The Beizhan iron deposit (468 Mt at an average grade of 41% Fe) is the largest iron deposit in the Awulale iron metallogenic belt of Western Tianshan, northwest China. The high-grade magnetite ores are hosted in the Carboniferous volcanic rocks with extensive development of skarn alteration assemblages. While considerable progress has been made in understanding the characteristics of Beizhan and its genetic association with volcanic rocks, the genetic models for ore formation are poorly constrained and remain controversial. This study combines detailed petrographic investigations with in situ LA-ICP-MS analyses of trace elements and Fe-O isotope compositions of magnetite to elucidate the origin of magnetite and the conditions of ore formation. The trace element concentrations in magnetite unveil intricate origins for various ore types, implying the precipitation of magnetite from both magmatic and hydrothermal fluids. The application of the Mg-in magnetite thermometer (T_Mg-mag) reveals a notable temperature divergence across different magnetite varieties, spanning from relatively higher temperatures in magmatic brecciated magnetite (averaging ~641 and 612 °C) to comparatively lower temperatures in hydrothermal platy magnetite (averaging ~552 °C). The iron isotopic composition in massive and brecciated magnetite grains, characterized by lighter δ⁵⁶Fe values (ranging from −0.078 to +0.005‰ and −0.178 to −0.015‰, respectively), suggest a magmatic or high-temperature hydrothermal origin. Conversely, the heavier δ⁵⁶Fe values observed in platy magnetite (+0.177 to +0.200‰) are attributed to the influence of pyrrhotite, signifying late precipitation from low-temperature hydrothermal fluids. Additionally, the δ¹⁸O values of magnetite, ranging from +0.6 to +4.6‰, provide additional evidence supporting a magmatic–hydrothermal origin for the Beizhan iron deposit. Overall, the identified genetic associations among the three magnetite types at Beizhan provide valuable insights into the evolution of ore-forming conditions and the genesis of the deposit. These findings strongly support the conclusion that the Beizhan iron deposit underwent a process of magmatic–hydrothermal mineralization. Full article

The Makeng iron deposit in southwest Fujian is a significant iron polymetallic deposit containing various types of iron ore, including garnet magnetite, diopside magnetite, and quartz magnetite. The metallogenetic type of the deposit has been a subject of debate, particularly in relation to the genesis of magnetite and the source of iron. In situ microanalysis of trace elements in magnetite from different ores shows relatively low levels of V, Ti, Cu, and Zn, with higher concentrations of Ca and Si, indicating the characteristics of a skarn type deposit. The δ⁵⁷Fe values of the magnetite range from −0.091‰ to 0.317‰. Combining these data, whole-rock iron isotope analyses, including Juzhou and Dayang granites, diabase, and the Lower Carboniferous Lindi Formation sandstone, suggest that Fe in the magnetite primarily originates from granitic pluton, with potential contributions from diabase and the Lower Carboniferous Lindi Formation sandstone. Combined with field work, these results indicate that Makeng iron deposit is a skarn-type magnetite deposit associated with Yanshanian granitic intrusions. Therefore, the initial ore-forming fluid is postulated to be a high-temperature magmatic hydrothermal fluid with high oxygen fugacity. This fluid infiltrates spaces such as interlayer fracture zones between the Upper Carboniferous Jingshe Formation–Middle Permian Qixia Formation carbonate rocks and the Lower Carboniferous Lindi Formation sandstone, resulting in diverse magnetite ores due to metasomatism. The mineralization process of the Makeng iron deposit is basically the same, as it is composed of typical skarn deposits. Magnetite was mainly formed during calcic skarn formation stage, and this process persisted until the initial phase of the retrograde alteration of skarns. In contrast, sulfide minerals, including molybdenite, sphalerite, and galena, precipitated during the quartz–sulfide stage. Full article

The Port Radium U-Cu-Ni-Co-Ag deposit in northwestern Canada is hosted within a mineral system that has generated a variety of mineralization styles from iron oxide-copper-gold to iron oxide-apatite, porphyry, skarn, and epithermal. Their genesis is linked to an extensive subduction-related magmatism that formed widespread dacite-rhyodacite-andesite volcanic and volcanoclastic sequences (~1.87 Ga), which have been intruded by their equivalent intrusive plutons. Pervasive and intensive hydrothermal alterations, including albitic, magnetite-actinolite-apatite, potassic ± albitic, phyllic, and propylitic occurred before the main sulfide, sulfarsenide, and uraninite vein-type mineralization. Although scarce sulfide minerals formed at the beginning of the hydrothermal activity, the main polymetallic arsenide-sulfarsenide-sulfide ± uraninite vein-type mineralization occurred during the epithermal stage. In addition to the common arsenides and sulfarsenides including nickeline, cobaltite, rammelsbergite, safflorite, skutterudite, gersdorffite, and arsenopyrite, three unique sulfarsenides were also found: Co_0.67Ni_0.32Fe_0.02S_0.19As_2.80, which could be a sulfur-rich skutterudite, Ni_0.85Co_0.15S_0.39As_1.60, and Ni_0.69Co_0.31S_0.47As_1.52, which are chemically comparable to the Port Radium rammelsbergite with substantial addition of S and Co; they could be the solid solution product of gersdorffite-cobaltite or safflorite-rammelsbergite. Full article

A comprehensive investigation into the application of machine learning algorithms for accurately classifying mineral deposit types is presented. The study specifically focuses on iron deposits in the Portuguese Ossa-Morena Zone, employing a limited dataset of trace element geochemistry from magnetites. The research aims to derive meaningful methodological and metallogenic conclusions from the obtained results. The findings demonstrate that the combination of a restricted dataset of trace element geochemistry from magnetites with diverse machine learning models serves as a reliable tool for achieving precise classifications of mineral deposit types. Among the machine learning methods evaluated, random forest, naïve Bayes, and multinomial logistic regression emerge as the most accurate classifiers, whereas the support vector machine, the k-nearest neighbour, and artificial neural networks exhibit lower performance scores. By integrating all literature-proposed classifications, and applying them to selected iron deposits, confident classifications were obtained. Alvito and Azenhas are reliably classified as skarns, whereas Monges, Serrinha, and Vale da Arca are classified as either porphyry or a Banded Iron Formation (BIF). Notably, the classification of Orada proves cryptic, encompassing both BIF and volcanogenic massive sulphide (VMS) deposit types. Moreover, the application of machine learning models to pertinent case studies offers valuable insights not only for classifying mineral deposit types but also for discerning mixed or complex origins. This approach provides meaningful results that can aid in the interpretation of mineral deposit types and may facilitate the identification of new mineral exploration targets. The research highlights the robustness of machine learning algorithms in interpreting magnetite data and underscores their potential significance in exploration projects. Full article

The Fanchang volcanic basin (FVB) is located in the Middle and Lower Yangtze Metallogenic Belt (MLYMB) between the ore districts of Ningwu and Tongling. The existing ore deposits in the FVB are relatively small in scale and related to late Mesozoic A-type granites. In this paper, the crystallization age, major and trace element composition, and Sr-Nd and Hf isotope compositions of the A-type granites are summarized from the literature; in addition, the magnetite composition, H and O isotopes of fluid inclusions, and sulfur isotope composition of metal sulfides in some typical ore deposits in the FVB are also summarized to give insights into the petrogenesis and mineralization of the A-type granites intruding into the FVB. The results show that: (1) Orthopyroxene, plagioclase, K-feldspar, and biotite are the main fractionating minerals controlling the evolution of the magmas of A-type granites in the FVB and other areas in the MLYMB. (2) The whole-rock Sr-Nd and zircon Hf isotopic characteristics show that the source of A-type granite magma is complex and includes the enriched mantle, lower crust, and upper crust, probably with stronger participation of Archaean–Paleoproterozoic crustal materials in the FVB granites than in other regions of the MLYMB. (3) The ores in the FVB are dominated by skarn and hydrothermal deposits. H and O isotopes of fluid inclusions indicate that ore-forming fluids have been derived from mixtures of magmatic hydrothermal fluid, meteoric waters, and deep brine related to gypsum layers. S isotopes of metal sulfides indicate that the sulfur may be a mixture of magmatically derived sulfur and sulfur originating from the Triassic gypsum-bearing layers. The deposit and ore characteristics of the main deposits in the FVB are also illustrated, and the evaluation of metal resources indicates that the skarn and hydrothermal iron–zinc ores in the FVB also have potential as sources of Cd, Ga, and Se. In addition, in terms of the oxygen fugacity, rock type, and geochemical characteristics of magmatic rocks, the metallogenic characteristics and potential of the A-type granites in the FVB are evaluated. It is considered that in addition to the dominant constituents of iron and zinc and the minor constituents listed above, the FVB could have the potential for providing copper, gold, molybdenum, uranium, and other metals as well. Full article