Search Results (233)

Gold mineralisation at Ity (Ivory Coast) is spatially associated with skarns formed at contacts between carbonate-rich Birimian volcano-sedimentary rocks and felsic intrusions, whereas at Dahapleu, a nearby skarn-free prospect, gold occurs in structurally controlled shear zones. Gold occurs as native gold in pyrite or as a Bi–Te–Au–Ag telluride assemblage. Fluid inclusion data indicate that Ity formed through a hybrid model: a mesothermal orogenic gold system dominated by CO₂–CH₄ fluids at >350 °C, superimposed on earlier skarn mineralisation characterised by saline fluids. At Dahapleu, no skarn fluids were identified, but volatile-rich inclusions with more variable signatures (CO₂, CO₂–CH₄, CO₂–N₂) indicate metamorphic fluids circulating in convective, fault-related systems and recording distinct fluid–rock interactions. The Ity–Dahapleu mineralising system thus displays fluid inclusion characteristics typical of mesothermal orogenic gold systems, likely at higher temperatures than most West African Birimian deposits. Overall, the Ity system reflects a long-lived thermal anomaly driving fluid circulation and metal deposition, with successive favourable events: rapid exhumation of hot lithospheric crust, granite intrusion, and skarn formation, followed by shear deformation and hydrothermal activity. 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

The Dulong Sn-polymetallic deposit in Yunnan Province of southwestern China serves as a unique case study for unraveling the evolution of skarn systems and tin mineralization. Four distinct garnet types (Grt I to Grt IV) were classified based on petrographic observations. Compositional analysis reveals a progression from Grt I to Grt III, marked by increasing andradite components, and elevated tin concentrations, peaking at 5039 ppm. These trends suggest crystallization from Sn-enriched magmatic-hydrothermal fluids. In contrast, Grt IV garnet exhibits dominant almandine components and minimal tin content (<2 ppm). Its association with surrounding rocks (schist) further implies its metamorphic origin, distinct from the magmatic origin of the other garnet types. Combined with previously published sulfur and lead isotopic data, as well as trace element compositions of garnet, our study suggests that Laojunshan granites supply substantial ore-forming elements such as S, Pb, W, Sn, In, and Ga. In contrast, elements such as Sc, Y, and Ge are inferred to be predominantly derived from, or buffered by, the surrounding rocks. The geochemical evolution of the garnets highlights the critical role of redox fluctuations and fluid chemistry in controlling tin mineralization. Under neutral-pH fluid conditions, early-stage garnets incorporated significant tin. As the oxygen fugacity of the ore-forming fluid declined, cassiterite precipitation was triggered, leading to tin mineralization. This study reveals the interplay between fluid redox dynamics, garnet compositional changes, and mineral paragenesis in skarn-type tin deposits. Full article

The Nanwenhe tungsten deposit is located in the southeastern Yunnan Laojunshan mineral district and is hosted in the Paleoproterozoic Mengsong Group strata. It can be divided into two periods and four stages: skarn (early and late) and the vein type (feldspar–quartz–scheelite–tourmaline and calcite. There are two types of scheelite occurrences: one in skarn (Sch-1) and the other in feldspar–quartz–scheelite–tourmaline veins (Sch-2). The latter is further divided into two types: Sch-2a and Sch-2b. The REE content and Eu anomaly of skarn scheelite (Sch-1) are affected by early mineral crystallization; Sch-2a in feldspar–quartz–scheelite–tourmaline veins forms in a Na⁺-rich environment, and Eu²⁺ released into the fluid through hydrolysis may have largely entered tourmaline, resulting in the weak positive Eu anomaly of Sch-2a; the negative Eu anomaly of Sch-2b is likely inherited from the metamorphic fluid. The mineralization is likely closely related to the metamorphic fluid activity generated by the tensional structural environment at the end and after the regional uplift, forming ore by reducing fluids associated with regional metamorphism. The Laojunshan mineral district hosts several tungsten and tin polymetallic deposits and occurrences that share similar geological characteristics with the Nanwenhe tungsten deposit. No granite bodies related to mineralization have been identified within the mining area. Therefore, research on the genesis of the Nanwenhe tungsten deposit holds significant value for guiding exploration efforts. Full article

Rare earth elements (REYs) are crucial components of billions of products worldwide. Transitioning from foreign to domestic REY sources requires utilizing both primary (i.e., carbonatites, alkaline igneous rocks, pegmatites, skarn deposits) and secondary (unconventional) sources (i.e., ion-adsorption clays, placer deposits, weathered rock, black and/or oil shales). Coal and coal-bearing strata, promising secondary REY resources, are the focus of this study. Understanding REY mineral associations in unconventional resources is essential to quantifying resource volume and identifying viable mineral separation and processing techniques. Highly REY-enriched (>750 ppm) coal or mudstone samples from the Uinta Region, Utah, USA, were selected for scanning electron microscopy (SEM) analysis. Energy dispersive X-ray spectroscopy (EDS)-determined REY enrichment occurs in: (1) a silt-size fraction (5–30 μm) of monazite and xenotime REY-enriched grains, (2) a clay-size fraction (2–5 μm) of monazite REY-enriched grains dispersed in the clay-rich matrix, and (3) organically confined REY domains < 2 μm. Findings suggest possible REY enrichment from multiple sources, including: (1) detrital silt-size grains, (2) volcanic ash fall, largely in clay-size grains, and (3) organic REY uptake in the peat swamp depositional environment. Full article

Hydrothermal scheelite from three Romanian occurrences was analyzed in order to ascertain its structural, physical, vibrational, paragenetic, and crystal-chemical peculiarities as an important tool for characterizing the metallogenetic behavior and facilitating the ore-processing. All three occurrences, i.e., Ciclova and Oravița in Banat and Băița Bihor in the Bihor Mountains, are related to skarn deposits developed at the contact of Upper Cretaceous granodioritic bodies with Mesozoic calcareous deposits. Typical crystals show {001}, {111}, and {101} forms and are up to 15 mm across. The structure was successfully refined as tetragonal, space group I4₁/a, with R₁ = 0.0165 (Ciclova), 0.0204 (Oravița), and 0.0237 (Băița Bihor), respectively. The cell parameters refined for the same samples are a = 5.2459(10) Å and c = 11.3777(5) Å at Ciclova, a = 5.2380(2) Å and c = 11.3679(8) Å at Oravița, and a = 5.2409(2) Å and c = 11.3705(6) Å at Băița Bihor. The multiplicity of bands in both infrared absorption and Raman spectra is consistent with the S₄ punctual symmetry of the tungstate anion, agreeing with the structural data. In all cases, the analyzed scheelite is close to the CaWO₄ end-member. Cathodoluminescence peculiarities at the level of single crystals suggest that they crystallized in a slightly oxidizing to reducing environment from late hydrothermal solutions. Textural and paragenetic peculiarities suggest that scheelite from the three occurrences crystallized from epithermal, low-temperature, fluoride- and boron-bearing aqueous solutions. 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

This study explores the magmatic and hydrothermal evolution of porphyry–skarn–transitional Cu-Mo-W-Au systems within the Nilüfer Mineralization Complex (NMC), located in the westernmost segment of the Eocene Tavşanlı Metallogenic Belt, NW Türkiye. Through integration of field data, whole-rock geochemistry, Re–Os molybdenite dating, and amphibole–biotite mineral chemistry, the petrogenetic controls on mineralization across four spatially associated mineralized regions (Kirazgedik, Güneybudaklar, Kozbudaklar, and Delice) were examined. The earliest and thermally most distinct phase is represented by the Kirazgedik porphyry system, characterized by high temperature (~930 °C), oxidized quartz monzodioritic intrusions emplaced at ~2.7 kbar. Rising fO₂ and volatile enrichment during magma ascent facilitated structurally focused Cu-Mo mineralization. At Güneybudaklar, Re–Os geochronology yields an age of ~49.9 Ma, linking Mo- and W-rich mineralization to a transitional porphyry–skarn environment developed under moderately oxidized (ΔFMQ + 1.8 to +0.5) and hydrous (up to 7 wt.% H₂O) magmatic conditions. Kozbudaklar represents a more reduced, volatile-poor skarn system, leading to Mo-enriched scheelite mineralization typical of late-stage W-skarns. The Delice system, developed at the contact of felsic cupolas and carbonates, records the broadest range of redox and fluid compositions. Mixed oxidized–reduced fluid signatures and intense fluid–rock interaction reflect complex, multistage fluid evolution involving both magmatic and external inputs. Geochemical and mineralogical trends—from increasing silica and Rb to decreasing Sr and V—trace a systematic evolution from mantle-derived to felsic, volatile-rich magmas. Structurally, mineralization is controlled by oblique fault zones that localize magma emplacement and hydrothermal flow. These findings support a unified genetic model in which porphyry and skarn mineralization styles evolved continuously from multiphase magmatic systems during syn-to-post-subduction processes, offering implications for exploration models in the Western Tethyan domain. Full article

The Mazenod Lake region of the southern Great Bear Magmatic Zone (GBMZ) of the Northwest Territories, Canada, comprises the north-central portion of the Faber volcano-plutonic belt. Widespread and abundant surface exposure of several coalescing hydrothermal systems enables this paper to document, without ambiguity, the relationships between geology, structure, alteration, and mineralization in this well exposed iron-oxide–copper–gold (IOCG) mineral system. Mazenod geology comprises rhyodacite to basaltic-andesite ignimbrite sheets with interlayered volcaniclastic sedimentary rocks dominated by fine-grained laminated tuff sequences. Much of the intermediate to mafic nature of volcanic rocks is masked by low-intensity but pervasive metasomatism. The region is affected by a series of coalescing magmatic–hydrothermal systems that host the Sue–Dianne magnetite–hematite IOCG deposit and several related showings including magnetite, skarn, and iron oxide apatite (IOA) styles of alteration ± mineralization. The mid to upper levels of these systems are exposed at surface, with underlying batholith, pluton and stocks exposed along the periphery, as well as locally within volcanic rocks associated with more intense alteration and mineralization. Widespread alteration includes potassic and sodic metasomatism, and silicification with structurally controlled giant quartz complexes. Localized tourmaline, skarn, magnetite–actinolite, and iron-oxide alteration occur within structural breccias, and where most intense formed the Sue–Dianne Cu-Ag-Au diatreme-like breccia deposit. Magmatism, volcanism, hydrothermal alteration, and mineralization formed during a negative tectonic inversion within the Wopmay Orogen. This generated a series of oblique offset rifted basins with continental style arc magmatism and extensional structures unique to GBMZ rifting. All significant hydrothermal centers in the Mazenod region occur along and at the intersections of crustal faults either unique to or put under tension during the GBMZ inversion. 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

As strategic critical metals, tungsten (W) and tin (Sn) require efficient exploration methods for effective resource development. This study implemented an advanced spread-spectrum induced polarization (SSIP) method in the Xitian mining district of southern China. Through optimized survey system configuration (maximum current electrode spacing of 5200 m, 12-channel acquisition, and five discrete frequency points), we achieved significant advancements: (1) a penetration depth of 1200 m, and (2) three- to five-times higher data acquisition efficiency compared to conventional symmetrical quadrupole arrays. Inversion results of resistivity and chargeability profiles from two parallel survey lines (total length 2.4 km) demonstrated an 85% spatial correlation between resistivity and chargeability anomalies, successfully identifying three mineralized veins. Drill-hole verification confirmed the presence of greisen veins (characterized by low resistivity <100 $\mathrm{\Omega }\cdot \mathrm{m}$ and high chargeability > 3%) and skarn veins (moderate resistivity 150–200 $\mathrm{\Omega }\cdot \mathrm{m}$ and chargeability 1.5–2%). The method exhibits a detection sensitivity of 0.5% chargeability contrast for deep-seated W-Sn polymetallic deposits, providing quantitative technical references for similar deposit exploration. Full article

Globally, most skarn deposits show a direct relationship with magmatic activity, indicating a genetic link between the geochemical composition of causative plutons and the metal content of associated skarns. Therefore, this study investigated the Early–Middle Eocene plutonic rocks and their relationship with Fe-Zn skarn deposits in the Esendemirtepe-Koçak and Horoz areas of south-central Türkiye. Despite the regional significance, previous studies have not adequately addressed the petrogenetic evolution of these intrusions and the geochemical characteristics of the related skarns. In particular, the fluid-aided mobility of elements at the contact between the causative plutons and the volcano-sedimentary country rocks remains poorly understood. Therefore, in this study, field studies, petrographic and mineralogical analysis, and whole-rock geochemical analysis were conducted to investigate the genetic link between the plutonic rocks and the skarn deposits. Field studies reveal that the skarn zones are within volcano-sedimentary sequences and marble-schist units intruded by four distinct plutonic bodies: (1) Esendemirtepe diorite, (2) Koçak diorite, (3) Horoz granodiorite, and (4) Çifteköy monzogabbro. These rocks exhibit calc-alkaline, I-type, and metaluminous signatures, except for the Çifteköy monzogabbro, which shows I-type, tholeiitic, and alkaline characteristics. All the plutonic rocks associated with the skarn formation display steep LREE-enriched REE patterns with minor positive Eu anomalies (Eu/Eu* = 0.98–1.35), suggesting a subduction-related volcanic arc setting similar to other granitoids in the Ulukışla Basin. The Horoz skarn exhibits both endoskarn and exoskarn features, while the Esendemirtepe-Koçak deposit is characterized by typical exoskarn features. Dominant ore minerals in both skarn deposits include magnetite, hematite, sphalerite, chalcopyrite, and pyrite, with minor arsenopyrite, galena, and cobaltite. The mineral composition of the skarn also shows the dominance of Na-rich and Mg-rich minerals in both locations. The geochemical compositions of the I-type, metaluminous Esendemirtepe-Koçak, and Horoz plutonic rocks are compatible with Fe-Zn skarn type deposits based on the moderate MgO (0.36–4.44 wt.%) and K₂O (1.38–7.99 wt.%), and Rb/Zr and Sr/Zr ratios. They also show typical volcanic arc features, and the variation in various trace element concentrations shows similarity with Fe-Zn skarn type granitoids. These findings support a strong genetic relationship between the mineralization and the geochemical and mineralogical characteristics of the associated plutonic rocks. Full article

We studied the chemical composition and morphostructural features of micron and submicron-sized particles of native gold in apocarbonate tremolite–diopside skarns of the Ryabinovoye deposit located on the southeastern margin of the Aldan Shield (Far East, Russia). Polished sections of lump ore samples containing native gold were analyzed by scanning electron microscopy in combination with X-ray microanalysis using different modes of visualization and X-ray diffraction methods. Gold particles, clearly visible after etching the surface of some polished sections with acids and partial or complete dissolution of some host minerals, were also examined. Native gold from the studied deposit is of high fineness (above 970‰) and contains (in wt.%) <1.59 Ag and less commonly <0.37 Cu and <0.15 Zn. Native gold is found intergrown with tremolite, diopside, and other magnesian silicates, as well as calcite, fluorite, magnetite, and sphalerite. Rare microinclusions of pyrrhotite, galena, and clinohumite are present in gold grains. It was found that native gold inherits the morphology of tremolite crystals and aggregates, which is determined by the size and shape of the voids bounded by its crystals. Gold localized in the intercrystalline spaces and in the zones of conjugation with remobilized calcite has irregular, lumpy shapes and partially or completely faceted grains with a dense structure. The nature of the localization and distribution of native gold in ores is due to the crystallization of the tremolite component of skarns. Apparently, the processes of gold accumulation are caused by the thermal activation of solid-phase differentiation of the substance of carbonate rocks, in which the processes of destruction of the original minerals and collective recrystallization play a significant role. It is likely that at some gold skarn deposits, carbonate rocks could be the source of gold. Data on the morphology and sizes of native gold segregations, as well as on the intergrown minerals, can be used to improve gold extraction technologies. A specific group of minerals intergrown with native gold in gold skarn deposits can be used as a diagnostic feature in the primary search for placer gold. The obtained results will help to better understand the formation of native gold in apocarbonate tremolite–diopside skarns. Full article

The Kesikköprü iron deposit, located in the Central Anatolian Crystalline Complex, occurs in the triple contact of Kesikköprü granitoid, mafic–ultramafic rocks, and marble. The causative Kesikköprü granitoid, consisting of diorite, granodiorite, and granite, is classified as sub-alkaline, calc-alkaline, and shoshonitic, displaying metaluminous to partially peraluminous properties. Sr-Nd isotope data and the geochemical characteristics of the Kesikköprü granitoid indicate a metasomatized mantle origin, with its ultimate composition arising from crustal contamination and magma mixing along with fractional crystallization in a post-collisional setting. The ⁴⁰Ar/³⁹Ar geochronology reveals a total fusion age of 73.41 ± 0.32 Ma for the biotite of the Kesikköprü granitoid. The alteration pattern in the deposit is characterized by an endoskarn zone comprising garnet–pyroxene (±phlogopite ± epidote) and an exoskarn zone displaying a zoning of garnet (±pyroxene ± phlogopite), pyroxene (±garnet ± phlogopite ± epidote), epidote–garnet, and epidote-rich subzones. Magnetite is extracted from massive lenses within the exoskarn zones and shows vein, disseminated, banded, massive, and brecciated textures. The low potassium content of phlogopites which are associated with magnetite mineralization prevents the determination of a reliable alteration age. δ¹⁸O thermometry reveals a temperature range between 462 and 528 °C for the magnetite mineralization. According to geochemical (trace and rare earth elements), stable (δ¹⁸O, δ²H, δ³⁴S, and δ¹³C), and radiogenic (⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd) isotope data, the hydrothermal fluid responsible for the alteration and mineralization is related to the Kesikköprü granitoid, from which a significant magmatic component originates initially, followed by meteoric fluids at lower temperatures (123 °C) during the late-stage formation of calcite–quartz veins. 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