Search Results (245)

The Mianhuakeng deposit, located within the Zhuguangshan batholith in the Nanling area, is currently recognized as the largest granite-related uranium deposit in China. A portion of the uranium ore bodies is spatially associated with NE-trending mafic veins within the granite. In this study, the field investigation, zircon U-Pb dating, S and Pb isotope analysis, and whole-rock geochemical analysis were conducted on these mafic veins to explore their crystallization age, petrogenesis, tectonic setting, and relationships with uranium mineralization. The weighted mean result of zircon U-Pb is 189 ± 3 Ma, suggesting that the mafic dyke was crystallized during the Early Jurassic. The whole-rock geochemistry and isotopes exhibit characteristics of intraplate basalts, suggesting that the mafic dykes originate from an enriched mantle source consisting of garnet–spinel lherzolite, with an estimated partial melting of 1%–5%. Mafic magmas underwent low-degree contamination from the lower crust during upwelling, induced by the extension of the lithosphere during the Early Jurassic. The analyses of pyrite sulfur isotopes in mafic samples vary between −2.9‰ and 1.8‰, significantly different from that of pyrite (−14.4‰ to −7.8‰) formed during the uranium mineralization. Furthermore, the ages of the pitchblende of 127–54 Ma are much younger than the crystallization ages of mafic dykes, indicating that the mafic magmas did not contribute to the uranium mineralization of Mianhuakeng deposit during magmatism. However, the abundant reducing minerals (e.g., pyrite, hornblende, and Fe²⁺-bearing minerals) in the mafic dykes can act as a redox barrier, reducing mobile U⁶⁺ to immobile U⁴⁺ during fluid–rock interaction, thereby facilitating uranium precipitation from the hydrothermal ore-forming fluids. The secondary fractures created by the intrusion of mafic magma probably provided favorable pathways for the movement of hydrothermal fluids. Full article

The Sanjiang Tethys orogenic belt in Southwest China is a globally important polymetallic metallogenic domain, hosting numerous world-class Cu-Pb-Zn deposits. Among these, the Lanping Basin is a typical ore concentration area, characterized by complex tectonic evolution and extensive hydrothermal mineralization. Although numerous vein-type Cu deposits occur in the northern and western parts of the basin, research in the north region remains less comprehensive. This study investigates three typical vein-type Cu deposits (Hetaoqing, Hemeigou, and Songpingzi) in the northern Lanping Basin using rare-earth element (REE) analysis, S-Pb-Sr isotope determinations, and tectonic stress inversion. Results show that ²⁰⁶Pb/²⁰⁴Pb ratios range from 18.374 to 18.691, and δ³⁴S_V-CDT values vary from –11.7‰ to +9.4‰, indicating mixed sources of ore-forming materials dominated by deep magmatic sources, particularly related to alkaline rocks around the basin. Sulfur sources are closely associated with thermochemical sulfate reduction (TSR). Additionally, ⁸⁷Sr/⁸⁶Sr ratios range from 0.710949 to 0.711864, ΣREE values range from 85.87 × 10^–6 to 111.86 × 10^–6, Ce/Ce* ratios range from 0.86 to 0.92, and Eu/Eu* ratios range from 1.06 to 2.99. Fluid inclusion microthermometry yields temperatures of 217–252 °C (average 238 °C), indicating that ore-forming fluids experienced water–rock interaction during migration and ultimately exhibited mixed properties. Tectonic stress field inversion reveals that the structures formed by NE–SW compressive stress field before mineralization stage provided ore-hosting spaces and fluid migration pathways, while a late Cenozoic abrupt stress field change promoted the precipitation of ore-forming materials. Full article

Iron oxide–apatite (IOA) deposits are important for the global supply of iron resources. Currently, there is considerable debate regarding the evolution of their mineralization mechanisms. The Heshangqiao iron deposit is a significant IOA deposit situated within the Ningwu ore district of the Middle–Lower Yangtze River Metallogenic Belt in China. This deposit exhibits distinct characteristics of multi-stage mineralization, forming disseminated ores, brecciated ores, and vein-type ores, from early to late stages. This study undertook a systematic elemental analysis of the magnetite and hematite from three mineralization stages of the Heshangqiao deposit. In the three mineralization stages of the Heshangqiao deposit, the elemental genesis indicators of ore genesis suggest that the hematite and magnetite both have magmatic hydrothermal genesis, characterized by high Ti and low Mg/Al and relatively high Ti and low Ni/Cr, respectively. The Cr and Sn contents of magnetite and hematite exhibit similar variation from the first to third mineralization stage, with an increase followed by a subsequent decrease. Meanwhile, the contents of V, Co, Ni, and Mn in magnetite and hematite exhibited an opposite trend, declining from the first to the second stage but eventually increasing from the second to the third stage. These changes in the genesis indicator also suggest that the multiple mineralization stages of the Heshangqiao deposit are independent of one another. The replacement of magnetite by hematite in each mineralization stage is not caused by the superposition of subsequent fluids, but rather by the residual fluid. It is noted that in the replacement the elements Cr, Co, and Ga were minimally migrated. These elements remained relatively stable and can be considered new potential discriminant indicators for the genesis of iron oxides. Full article

The close spatial and genetic coexistence of Skarn-type and Hydrothermal Vein-type Pb-Zn deposits in the Shanghulin area, Inner Mongolia, poses a significant challenge to conventional “ undifferentiated” prediction models. This study aims to decouple these distinct metallogenic patterns using a data-driven, “type-specific modeling” strategy, establishing separate prediction models for Skarn-type and Hydrothermal Vein-type mineralization. Our workflow first employs Lasso–RFECV for rigorous pre-screening of over 60 geoscience features to identify the optimal predictive subset. Subsequently, an XGBoost model is trained on these selected features, and the SHAP framework is applied to interpret the geological significance of its decision logic. The results confirm two distinct indicator systems. (1) The Skarn-type model is controlled by spatial proximity to a heat source, heavily relying on Distance_to_Volcano and high-temperature indicators (CLR_Mo, CLR_W, CLR_Mn). (2) The Hydrothermal Vein-type model is “chemical fingerprint-driven”, prioritizing CLR_Y and identifying a complex “leaching-enrichment” pattern: mineralization requires simultaneous wall-rock leaching (low CLR_Al₂O₃, low CLR_Y) and specific metal enrichment (high CLR_Co, high CLR_Zn). This study confirms the controlling factors: Skarn-type deposits are governed by magmatic proximity, whereas Hydrothermal Vein-type deposits are defined by specific alteration geochemical signatures. The proposed “Lasso–RFECV → XGBoost → SHAP” workflow successfully decouples these independent, geologically meaningful prospectivity models from complex data, offering a new paradigm for precise exploration. Full article

The Wunuer deposit is an important hydrothermal Zn-Pb-Ag-Mo polymetallic deposit in the central Great Xing’an Range, NE China. The zinc–lead polymetal mineralization is closely hosted by the volcanic rocks of the Manketouebo formation (rhyolite and lithic crystal tuff) and related to the Mesozoic granite porphyry. Field evidence and petrographic observations have identified three mineralization stages within this deposit from deep to shallow: (1) late magmatic stage with vein-type Mo mineralization characteristics and mainly related to the deep granite porphyry; (2) magmatic–hydrothermal transition stage characterized by breccia-type Zn mineralization, which occurred within a steep cryptoexplosive breccia; and (3) hydrothermal stage featured by vein-type Zn-Pb-Ag mineralization hosted by the ore-bearing fractured zone. In this contribution, we present the mineralogy, zircon U-Pb age, sphalerite Rb-Sr dating, whole-rock geochemistry, and Hf-S-Pb isotopes of the Wunuer deposit. LA-ICP-MS zircon U-Pb dating of the ore-related granite porphyry, rhyolite, and lithic crystal tuff suggests that the Mo mineralization from the late magmatic stage occurred between 144.8 Ma and 145.8 Ma. The Rb-Sr isochron dating of sphalerite indicates that the hydrothermal stage Zn mineralization age is 121 ± 2.3 Ma, which is related to the volcanism of Baiyin’gaolao Formation in the Wunuer area. The concentrated and positive δ³⁴S_V-CDT values (0.17‰~5.40‰) of sulfides, as well as uniform Pb isotope compositions of granite porphyry intrusion and galena, jointly imply a magmatic source of metallogenic materials for Pb-Zn mineralization. Whole-rock geochemistry and Hf-Pb isotopes reveal that the granite porphyry and rhyolite both originated from a mantle-derived juvenile component and assimilated by minor ancient crustal material in an extensional setting. Our study demonstrates the prospect of further exploration for two mineralization events in the hydrothermal polymetallic deposits of the central Great Xing’an Range. Full article

In many gold–antimony deposits throughout the world, the sequence of Au and Sb precipitation varies significantly. In high-temperature systems such as hydrothermal Au deposits, gold typically precipitates prior to antimony, whereas in lower-temperature systems (e.g., Carlin-type deposits), no consistent depositional sequence is observed. The Gutaishan Au-Sb deposit, located in the Xiangzhong Basin of the Jiangnan Orogenic Belt, South China, exhibits a distinct spatial segregation within a continuously evolving system of gold and antimony mineralization—a pattern commonly observed in many Au-Sb deposits throughout the region. To elucidate the mechanisms controlling Au-Sb co-occurrence and segregation, we conducted electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) major and trace element analyses of stibnite and pyrite from quartz veins across different ore zones within the Gutaishan deposit. Trace element signatures—such as Cu-Pb correlations and Hg/(Cu + Pb) ratios which classify stibnite into Woxi-type and Xikuangshan-type, and Co/Ni ratios classifies pyrite into magmatic–hydrothermal and sedimentary types—suggest that the ore-forming fluids were predominantly magmatic–hydrothermal in origin, with minor contributions from metamorphic basement fluids. The occurrence of low-temperature trace element signatures in the Au-Sb deposit indicates that temperature is the primary control on Au-Sb segregation. The thermodynamic model further confirms that high-temperature fluids favored the precipitation of Au veins, while lower-temperature fluids facilitated the co-precipitation of stibnite and gold in Sb-Au veins. Therefore, we propose a metallogenic model for the Gutaishan deposit that highlights temperature-driven Au-Sb segregation, resulting from the progressive cooling of the ore-forming fluids. Full article

The Yanlinsi gold deposit, located in the middle section of the Jiangnan Orogenic Belt, is one of the typical gold deposits in northeastern Hunan Province. Diabase dikes are exposed by underground workings and drill holes in the mining area. The dikes strike NW and cut the NE-trending gold ore body. To investigate the petrogenetic age, characteristics of the magmatic source area, and tectonic setting of the diabase dikes in the Yanlinsi gold mining area, northeastern Hunan, and to determine the mineralization age of the deposit, in this paper, diabase dike LA-ICP-MS zircon U-Pb dating, whole-rock geochemistry, and gold-bearing quartz vein LA-ICP-MS zircon U-Pb dating were studied. The results of LA-ICP-MS zircon U-Pb dating indicate that the diabase was emplaced at an age of 219.5 Ma, belonging to the late Indosinian. The investigated diabase dikes are characterized by low SiO₂ (43.68%–46.55%), high MgO (7.78%–9.84%), and high Mg# (65.0–68.7) values, belonging to the alkaline basalt series with high potassium. The chondrite-normalized REEs patterns show highly fractionated LREEs and HREEs ((La/Yb)_N = 11.21–14.82), and the primitive mantle-normalized spider patterns show enrichment in large ion lithophile elements (e.g., Rb, Ba, K and Sr) and relative depletion in high field strength elements (e.g., Nb, Ta, and P), similar to those of ocean island-like basalt (OIB). Rock geochemical characteristics indicate that the magma of the Yanlinsi diabase was formed by partial melting of the enriched mantle (EM II), with the source region being spinel-garnet lherzolite. The degree of partial melting was approximately 10%–15%, and the assimilation and contamination with continental crustal materials were weak. Meanwhile, weak fractional crystallization of olivine, clinopyroxene, and apatite occurred during the magma evolution process. On the basis of a synthesis of previous research results, it is concluded that the Yanlinsi diabase formed in an extensional tectonic setting after intracontinental collisional orogeny. The LA-ICP-MS U-Pb age of hydrothermal zircons from quartz veins in the main mineralization stage of the Yanlinsi gold deposit is 421.9 ± 1.5 Ma. Combined with the cross-cutting relationships between mafic dikes and gold veins (ore bodies), it is determined that the main mineralization stage of the deposit formed during the Caledonian Period. Full article

Thorium-rare earth-iron oxide deposits of the Lemhi Pass district, Idaho and Montana, are enriched in the middle rare earth elements (REE), and particularly neodymium (Nd). Overall, thorium (Th) and total rare earth oxide (TREO) grades of the deposits are sub equal at 0.4 wt. % but locally exceed 1 wt. % TREO. Nd-monazite, the major REE phase (35 wt. % Nd₂O₃) occurs in hydrothermal Th-REE mineralized quartz veins and biotite-rich shear zones of enigmatic origin. Hosted in Mesoproterozoic metasedimentary rocks, the deposits are modest in size but present over a large area with no obvious source pluton exposed. This paper documents the geochemistry of the monazite and provides the first geochronological data to constrain its origin. Elemental mapping and U-Th-total Pb EPMA dating of the monazite and thorite document a Paleozoic age for mineralization centered in the Late Devonian at approximately 355 Ma ± 20 Ma. A second period of volumetrically minor Th and REE remobilization is dated as Mesozoic (ca. 100 Ma). For context, a reactivated passive continental margin was present during the Devonian in eastern Idaho, while the Mesozoic was a time of major accretionary tectonics and arc magmatism further west. Nd and Pb isotopic data require a significant interaction of the fluids with an ancient crustal component represented by regional Mesoproterozoic metasedimentary rocks and granitoids. A source–transport–deposition model is hypothesized with metasomatic fractionation and enrichment of Nd during regional hydrothermal circulation. The aqueous fluids were hot, oxidizing, and likely saline, but the exact source of the Th and REEs and the mechanism of enrichment remains problematic. Additional analytical work and increased knowledge of the regional and district geology will improve this unconventional hypothesis for formation of Lemhi Pass’ unusual Nd-rich Th-REE-Fe mineralization. Full article

The Zhunuo porphyry Cu deposit (2.9 Mt Cu @ 0.48%) in the Gangdese belt, southern Xizang, represents a key Miocene post-collisional system. This study integrates textural, major-, and trace-element analyses of pyrite from distinct alteration zones to unravel its hydrothermal evolution and metal precipitation mechanisms. Our study identifies four distinct pyrite types (Py1-Py4) that record sequential hydrothermal stages: main-stage Py2-Py3 formed at 354 ± 48 to 372 ± 43 °C (based on Se thermometry), corresponding to A and B vein formation, respectively, and late-stage Py4 crystallized at 231 ± 30 °C, coinciding with D-vein development. LA-ICP-MS data revealed pyrite contains diverse trace elements with concentrations mostly below 1000 ppm, showing distinct distribution patterns among different pyrite types (Py1-Py4). Elemental correlations revealed coupled behaviors (e.g., Au-As, Zn-Cd positive correlations; Mo-Sc negative correlation). Tellurium variability (7–82 ppm) records dynamic fO₂ fluctuations during system cooling. A comparative analysis of pyrite from the regional deposits (Xiongcun, Tiegelongnan, Bada, and Xiquheqiao) highlighted discriminative geochemical signatures: Zhunuo pyrite was enriched in Co-Bi-Ag-Pb (galena inclusions); Tiegelongnan exhibited the highest Cu but low Au-As; Xiquheqiao had the highest Au-As coupling; and Bada showed epithermal-type As enrichment. Partial Least Squares Discriminant Analysis (PLS-DA) identified Cu, As, and Bi as key discriminators for deposit types (VIP > 0.8), with post-collisional systems (Zhunuo and Xiquheqiao) showing intermediate Cu-Bi and elevated As versus arc-related deposits. This study establishes pyrite trace-element proxies (e.g., Se/Te, Co/Ni, and As-Bi-Pb) for reconstructing hydrothermal fluid evolution and proposes mineral-chemical indicators (Cu-As-Bi) to distinguish porphyry-epithermal systems in the Qinghai-Tibet Plateau. The results underscore pyrite’s utility in decoding metallogenic processes and exploration targeting in collisional settings. Full article

The Antas North mine, located in the southeastern Amazonian Craton within the Carajás Mineral Province, is hosted by mafic and felsic metavolcanic rocks that have undergone extensive hydrothermal alteration. Field and petrographic data reveal a hydrothermal sequence comprising sodic (albite), potassic (biotite + scapolite), calcic (amphibole + apatite), silicification (quartz), and propylitic (chlorite + epidote + calcite) assemblages. Copper–gold mineralization, spatially associated with calcic alteration, occurs as massive sulfide lenses, breccia zones, and vein networks dominated by chalcopyrite, pyrrhotite, and pyrite. The absence of magnetite/hematite and the dominance of sulfides and ilmenite classify Antas North as an Iron Sulfide–Copper–Gold (ISCG) system, representing a reduced endmember within the broader IOCG spectrum. New U–Pb titanite geochronology yields two concordant age populations at ca. 2476.6 ± 15.9 Ma Ga and 2162.9 ± 28.1 Ma Ga, recording a late Archean mineralizing stage and subsequent Paleoproterozoic reactivation during the Transamazonian orogeny. These ages parallel the multistage evolution recognized in other Carajás IOCG deposits, where copper–gold-related mineralization was repeatedly overprinted by later tectono-hydrothermal events. The reduced character of Antas North, marked by ilmenite and sulfide dominance with scarce magnetite, demonstrates that reduced IOCG styles were already established in the Neoarchean–Paleoproterozoic transition and underscores the diversity of mineralizing processes within the Carajás IOCG–IOA spectrum. Full article

High-purity quartz (HPQ) is a critical raw material for advanced technologies including semiconductors, photovoltaic cells, and optical fibers. This study reviews the geological occurrence, beneficiation routes, and strategic significance of HPQ within the European context. Quartz processing follows a sequential flowsheet of comminution, magnetic separation, flotation, acid leaching, and thermal treatment, designed to remove mineral impurities such as Fe, Al, Ti, and mica. The resulting ultra-high-purity quartz (UHPQ) achieves the chemical and physical specifications required for high-tech industries. Quartz, which is the most common mineral on Earth, can be found in a variety of geological locations such as granitic rocks and pegmatites in the Variscan Belt, metamorphic quartzites, hydrothermal veins, and Pleistocene periglacial and aeolian sediments. Case studies of European deposits demonstrate that geological origin directly influences processing requirements, and that tailored beneficiation strategies are essential to unlock viable resources. To our knowledge, this is the first Europe-focused synthesis that links these findings with the EU Critical Raw Materials Act, the work that emphasizes the potential for domestic HPQ development to strengthen European supply chain resilience, reduce dependence on imports, and support the transition to a green and digital economy. Full article

This study presents experimental and geochemical modeling results that validate a fluid-mixing model for baryte and sulfide mineralization in vein-type hydrothermal systems, with reference to the Mykonos granodiorite, Cyclades. Synthetic Ba-rich hydrothermal fluids, representing those released during retrograde alteration of granitoids, were mixed with SO₄²⁻-bearing solutions, simulating Miocene seawater under controlled conditions (200–300 °C, <100 bars). Baryte precipitated rapidly upon mixing, accompanied by the co-precipitation of sulfides, such as sphalerite, chalcopyrite, galena, and minor native silver. The experiments reproduced key mineral assemblages observed in the Mykonos vein system, emphasizing the importance of a second fluid boiling at 250 °C, and redox shifts as triggers for ore formation. Complementary geochemical simulations (Solveq) constrained the stability fields of Ba–sulfate and base-metal sulfides, highlighting the critical influence of pH (5.0–6.2) and SO₄²⁻/H₂S ratios on mineral precipitation. The integration of experimental and simulation approach supports a robust model for baryte–sulfide deposition in shallow, extensional settings, where fault-controlled fluid flow promotes episodic mixing and boiling of magmatic and seawater-derived ore fluids. Full article

We present the chemical composition and the U-Pb chemical age of the recently discovered uranium mineralisation occurrence in the crystalline Shkhara Massif in the Greater Caucasus. The mineralisation consists of hydrothermal uraninites from veins that intersect into the Late Variscan biotite–plagioclase-rich granite and migmatites. The chemical composition and the Th–U total Pb chemical age of the uraninites were determined. Results show thorium-rich, (∑LREE/∑HREE)_N unfractionated uraninites that had been formed under higher temperatures above 450 ± 50 °C. Fifty-eight measurements on 14 grains revealed homogeneous and unaltered uraninites. Th–U–total Pb ages of the uraninite were calculated from 55 chemical analyses, among which 37 plot between 275 and 305 Ma. The weighted median age of the 55 data points corresponds to 291 ± 14 Ma: the boundary between the Carboniferous and Permian periods. These dates suggest that uraninite mineralisation is related to the late orogenic extensional process of the Great Caucasus structure. During this process, hydrothermal fluids permeated the biotite-+ and plagioclase-rich magmatic rocks of the Main Range zone and formed U- and Th-rich veins and uraninite mineralisation. This study shows that the Shkhara uranium occurrence correlates with most of the late Variscan uranium deposits in Central and Western Europe in terms of geodynamic setting, composition, age and type of mineralisation. Full article

The evolution of ore-forming fluids in gold precipitation is a key aspect in understanding the genesis of orogenic gold deposits. Traditional fluid inclusion analyses are often limited in revealing the fluid property changes during mineralization, leading to significant debates on the mineralization temperature and fluid sources. In this study, we selected the Liba gold deposit in the West Qinling orogen and employed scanning electron microscope–cathodoluminescence (SEM-CL) and laser ablation–inductively coupled plasma mass spectrometry (LA-ICPMS) to analyze the microstructure and trace element characteristics of quartz veins, revealing the multi-stage evolution of ore-forming fluids and the mineralization mechanisms. SEM-CL imaging identified five distinct quartz stages. The pre-mineralization (Qz0) and early-stage mineralization (Qz1) fluids were predominantly magmatic–metamorphic in origin, as indicated by relatively high δ¹⁸O and δD values. During the primary metallogenic (Qz2a, Qz2b) and late-stage mineralization (Qz3), temperatures progressively decreased, and the gradual mixing of meteoric water and formation water was observed, which promoted gold precipitation. And the content of trace elements in post-mineralization quartz (Qz4) is significantly lower and similar to that in the Qz0 stage. Through the analysis of quartz trace elements (e.g., Al/Ti, Ge/Al ratios) and isotope data (δ18O = 8.25‰ to 12.67‰, δD = −119.1‰ to −79.8‰), the results indicate that the Liba gold deposit is a medium- to low-temperature orogenic gold deposit. Furthermore, the gold enrichment process was primarily driven by a hydrothermal system, with variations in the fluid composition during mineralization contributing to the concentration of gold. Full article

The newly discovered Yanshan gold deposit within the Qixia–Penglai mineralization belt is situated within the Daliuhang goldfield of Daliuhang Town, approximately 45 km southeast of Penglai City, the Jiaodong Peninsula. Quartz-vein–type gold orebodies are mainly distributed among the Guojialing granite and are controlled by NNE-trending faults. Native gold primarily occurs within the interiors of pyrite grains, forming inclusion gold and fracture gold. In this study, LA-ICP-MS zircon U-Pb dating and in situ sulfur isotope analysis of gold-bearing pyrite were conducted to constrain the ore genesis of the Yanshan gold deposit. Guojialing monzogranite and porphyritic granodiorite yielded weighted mean ²⁰⁶Pb/²³⁸U ages of 130 ± 2 Ma (MSWD = 1.8) and 131 ± 2 Ma (MSWD = 1.8), respectively, indicating that magmatism and gold mineralization occurred during the Early Cretaceous period. The in situ sulfur δ³⁴S values of euhedral crystalline pyrite (Py1) formed in the early stage ranged from 3.21% to 5.35‰ (n = 11), while the in situ sulfur δ³⁴S values of pyrite (Py2) formed in the later stage ranged from 6.32‰ to 9.77‰ (n = 10), suggesting that the sulfur of the Yanshan gold deposit primarily originates from magmatism, with contamination from stratigraphic materials. Granitoids are highly likely to provide the thermal drive for fluid activity; however, the origins of the fluids and ore-forming materials remain difficult to determine. Based on geological features, geochronological data, and in situ sulfur isotopic analysis, this study concludes that the Yanshan gold deposit is a mesothermal magmatic hydrothermal vein-type gold deposit. The mineralization of the Yanshan gold deposit is related to the subduction of the Mesozoic Paleo-Pacific Plate beneath the Eurasian continent and is mainly controlled by steep dip faults. This study provides theoretical guidance for further exploration and prospecting of the Yanshan gold deposit. Full article