In this session, we invite multidisciplinary contributions that investigate various ore deposits and their associated formation dynamics, using fieldwork, microstructural and petrographic analyses, geochemistry, machine learning, thermodynamic and numerical modeling. Case studies of economic ore deposits are welcomed.
Orals: Mon, 4 May, 08:30–12:25 | Room 0.96/97
The Tepeköy Au prospect within the Melendiz volcanic suite (southern Central Anatolian Volcanic Province, central Türkiye) preserves a high-sulfidation (HS) epithermal alteration system hosted by andesite porphyry and basaltic–andesite volcanic rocks. Alteration is spatially zoned from an inner vuggy silica–Fe-rich domain outward to an alunite-rich halo and a distal kaolinite-rich zone, with gold concentrated mainly in the inner two zones. This framework and mineral association (dominantly pyrite ± arsenopyrite ± magnetite with supergene/oxidation products such as limonite, hematite, and goethite) are consistent with established HS epithermal model in which acid–sulfate fluids generate advanced argillic assemblages and residual/precipitated silica near the hydrothermal ascending core.
To quantify element mobility and bulk-rock modification across the alteration gradient, mass-balance calculations were evaluated using isocon methods, treating TiO2–Nb–Zr as immobile indicators. The vuggy silica–Fe-rich zone records the most extreme open-system behavior, defined by substantial gains in SiO2, Fe2O3, sulfur (S, SO3) and LOI, accompanied by enrichment in As–Co–Ni–Mo–V–Cr (locally ±Sc). These increases occur alongside pronounced depletion of major base cations (Na2O–K2O–CaO–MgO) and marked loss of several chalcophile elements (Cu–Zn–Sn–Sb). Isocons indicate that both bulk mass and volume changes exceed the reference frame, implying high fluid/rock ratios and strong permeability focusing within the inner zone. The alunite-rich halo shows similarly robust additions of SiO2–Fe2O3–SO3–LOI and systematic pathfinder enrichment (notably As ± Mo ± V ± Pb ± Co–Ni), while maintaining persistent base-cation depletion; additional gains in Cl, Sr, and Ba and overall mass/volume increase suggest continued influx of sulfate-bearing fluids and deposition of hydrated sulfate phases. In contrast, the kaolinite-rich zone displays net mass/volume loss, relative SiO2 depletion, and more mixed gains (Fe2O3, SO3, LOI, As ± Ba–Sr), consistent with distal buffering and/or dilution of the reactive acidic fluid. A coupled P2O5–Sr enrichment in the alunite halo supports stabilization of aluminum phosphate–sulfate (APS) minerals during apatite breakdown under advanced-argillic conditions, offering an additional geochemical vector toward the hydrothermal center.
Finally, the mass-balance results demonstrate that fluid-driven addition and leaching dominate within the vuggy silica core and alunite halo, while distal kaolinitization indicates reduced mass transfer. These patterns offer quantitative criteria for identifying High Sulfidation influx zones and their associated Au enrichment at Tepeköy.
Keywords: Mass-balance calculation; alteration geochemistry; Tepeköy high sulfidation epithermal Au mineralization; Melendis volcanic suite; Central Türkiye
How to cite: Bakkalbasi, H. N., Kumral, M., Abdelnasser, A., and Bakkalbasi, A. E.: Isocon mass-balance constraints on element mobility in the Tepeköy high-sulfidation epithermal Au system within Melendiz volcanics, Central Türkiye, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14660, https://doi.org/10.5194/egusphere-egu26-14660, 2026.
A significant part of gold production in Canada is associated with orogenic-style quartz veins. However, some critical parameters – the timing of mineralization, the source and transport of gold, and the gold precipitating mechanisms – remain enigmatic in several districts. The Bonnefond deposit, located in the southeastern Abitibi Subprovince, Québec, is part of the world-class Val-d’Or vein field (VVF). Gold mineralization is associated with pyrite in quartz-tourmaline-carbonate (QTC) veins that cut a subvertical tonalitic plug. Near-infrared imaging and trace element mapping of this Au-bearing pyrite show complex chemical zoning. An inclusion-richer core (Py1) is overgrown by a euhedral, oscillatory-zoned domain (Py2). A sharp front delineates a final pyrite generation (Py3), barren of gold. Highest trace element contents are recorded in Py1 (Co ~ 2000 ppm, Ni ~ 1500 ppm, As < 60 ppm) whereas Py2 displays lower contents (Co < 1750 ppm, Ni < 1000 ppm, As < 50 ppm). The Py1 shows δ34S = -7.7‰ to -2.2‰ and Δ33S = -0.04‰ to 0.04‰; Py2 displays δ34S = -4.7‰ to 4.0‰ and Δ33S = -0.15‰ to 0.08‰; and Py3 shows δ34S = -1.6‰ to 4.7‰ and Δ33S = -0.06‰ to 0.03‰. Gold is found as Au ± Te inclusions in Py2 (Au1), as trapped inclusions at Py2-Py3 border (Au2), and at pyrite margins and in microfractures (Au3). Trace element contents and multiple S isotopes suggest that fluid-rock interactions drove a coupled fO2, fS2, and fTe2 decrease in the auriferous fluid which precipitated Au1. The dissolution-reprecipitation (DR) textures and the multiple S isotopes suggest that pyrite DR triggered gold remobilization (Au2). In situ U-Pb xenotime geochronology yields a QTC mineralization age of ca. 2663 Ma whereas a ca. 2608 Ma age indicates gold remobilization. The proposed multi-stage mineralizing process supports recent studies in the VVF, suggesting that fluid-rock interactions and gold remobilization via DR are key mechanisms to orogenic gold mineralization.
How to cite: LaFlamme, C., Bonin, F.-X., Beaudoin, G., Rottier, B., McFarlane, C., and Martin, L.: Evidence of multi-stage orogenic gold mineralization at the Bonnefond deposit, Val-d’Or, Québec, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1472, https://doi.org/10.5194/egusphere-egu26-1472, 2026.
The Arabian Nubian Shield is a massive juvenile accretionary orogenic belt formed due to the assembly of Gondwana. It is exposed along the margins of the Red Sea and hosts hundreds of gold prospects as well as a limited number of operating gold mines. Until recently, the widespread occurrence of gold across the shield was thought to be exclusively the result of Neoproterozoic Gondwanan tectonics and related ore-forming processes. This proposal suggests that the shield contains gold mainly in older volcanogenic massive sulfide (VMS) deposits and younger orogenic gold deposits. This widely accepted proposal complies with the geological history of the shield, but it remains unproven, given that most prospects are still understudied, with only a handful having ore-stage geochronological constraints.
The Hamama polymetallic gold prospect in Egypt hosts a Zn-Pb rich stratabound ore with inferred gold and silver resources of 230 koz and 7836 koz, respectively. The prospect area is mainly covered by submarine metavolcanics-metavolcaniclastics assemblage, and the ore has been long classified as a syngenetic Au-bearing VMS based on the general geologic setting and old literature data. Interestingly, modern exploration activities confirmed the absence of massive sulfide lenses at depth and elucidated that the ore in Hamama is hosted exclusively in an oxidized horizon composed essentially of carbonates, silica and barite. The oxidized gossan cap extends between the metavolcanics-metavolcaniclastics for 3.2 km in a NE-ENE direction. Boreholes penetrate the oxidized cap usually to ~30 m depth, beneath which the unoxidized host rock occurs. The mineralized host, as whole, is intersected in the boreholes at an average depth of 120 m. It is intensely brecciated and fractured, and has been previously described as an exhalite or a carbonatized felsic volcanic rock.
Our detailed petrographic study on deep drill cores retrieved from two representative diamond drillholes supported by frequent field campaigns reveals that the mineralized horizon is a dolomitic formation representing the base of the sedimentary cover in the region, which is reported for the first time in this study. Based on its fossil content and local paleogeography, we reinterpret this ore-bearing formation as a part of the Late Cenomanian-Early Turonian carbonate platform of NE Africa deposited in a paleovalley between the Neoproterozoic basement. The structural complexity of the shield, the thick oxidized cap, and the diagenetic and hydrothermal processes played a major role in the previous misinterpretation of the host rock. This finding refutes the Neoproterozoic VMS deposit model in Hamama area and introduces a new sedimentary formation of economic potential to the Egyptian stratigraphic sequence, which we call Abu Garida dolostone. As a starting point, this study provides the first evidence for the presence of significant Late Phanerozoic gold inside the shield. Finally, this interesting case study elucidates that the history of gold precipitation across the shield is more complex than previously thought.
How to cite: E. Morad, A. and Wagner, T.: Hamama polymetallic Au prospect in the Egyptian part of the Arabian Nubian Shield: How a single occurrence can improve the knowledge of a gigantic metallogenic province., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-653, https://doi.org/10.5194/egusphere-egu26-653, 2026.
The Niğde Massif is a metamorphic core complex located at the southernmost of the Central Anatolian Crystalline Complex (CACC) and is productive in terms of metamorphic-hosted Au-Sb, Au-As mineralization. It is bordered by the Ecemiş fault zone to the east and the Celaller thrust to the south. South-to-north lower-grade metamorphosed units cover ductile deformed high-temperature metamorphic levels on the massif. The massif is mostly composed of the Upper Devonian Gümüşler Formation, Carboniferous-Lower Permian Kaleboynu Formation, and Mesozoic Aşıgediği Formation, which occur unconformably. The Üçkapılı Granodiorite and Sineksizyayla Metagabbro in the Upper Cretaceous cut metamorphics, while post-Paleocene sedimentary deposits in the south and Neogene volcanic deposits in the north cover the entire sequence. Gümüşler, Kaleboynu, and Aşıgediği formations contain gneiss, schist, amphibolite, marble and quartzite units. This study examines the Çamardı region in the southeastern part of the Niğde Massif and the Au-As and Au-Sb mineralizations in this region. In the Çamardı Region, thrusted Gümüşler Formation over the younger Kaleboynu and Aşıgediği metamorphics are in NE-SW direction. This thrust forms the sub-formation which is known as SE Gümüşler, and the average dip- dip direction of the metamorphics forming the base of this formation has been measured as 150/40. Gold mineralization in ductile cataclastic breccia and schists is related with pyrite-arsenopyrite mineralizations. However, gold is related with siliceous-rich matrix with well-developed stibnite crystals in marble-schist contacts at the upper levels. W-E and NW-SE faults have been identified; it has been determined that the NW-SE faults generally intersect the W-E faults. These fault zones may be transfer zones for metamorphic-derived fluids to generate Au-As cataclastic breccias in deep cataclastic zones and Au-Sb mineralized brittle silica-rich breccia in marble-schist contacts at higher levels. It is considered that the Üçkapılı granodiorite and associated aplitic dikes intruding into the schists cut by NW-SE faults in the southwest of the field play a role in the transport and remobilization of Au-As-Sb mineralization observed both within the schists and in the marble-schist contacts. Gold values in rock samples in the field ranged from 0.3-6.7 ppm, while antimony values ranged from %0.3- 1. arsenic values ranged from %0.1-1 in gold-antimony rich samples. In polished sections, gold, arsenopyrite, stibnite, realgar, and marcasite are identified as ore minerals; and quartz, sericite, and rutile as gangue minerals. Gold grains generally range in size from 30-100 µm and are mostly found within pyrite and arsenopyrite. Deformation textures developed by cataclastic processes are present in arsenopyrite, pyrite, and stibnite minerals. Realgar-quartz fillings through fractures, tetrahedrite/tennantite veins cutting deformed pyrite crystals and the marcasite that replaces arsenopyrite and pyrite represent late-stage hydrothermal components. In certain samples, gold fills the discontinuities between pyrite and arsenopyrite alongside stibnite. The findings collectively impose significant early-stage constraints on the structural, mineralogical, and hydrothermal development of gold mineralization in the southern part of the Niğde Massif. All these observations indicate that gold mineralization occurred in at least two phases; may have associated with the arsenopyrite-pyrite paragenesis, and may also have been transported through discontinuities in later stages with stibnite.
How to cite: Bakkalbasi, A. E., Kumral, M., and Oyman, T.: Metamorphic hosted Au-Sb mineralizations in the Nigde Massif (SE Çamardı Region), Central Anatolia: field and ore microscopy studies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22679, https://doi.org/10.5194/egusphere-egu26-22679, 2026.
Tibet in SW China hosts numerous Sb mineralization, with a number of Sb-only and Sb-polymetallic ore deposits and occurrences distributed across both southern and northern parts. Here we present in-situ Sb isotope compositions of stibnite from multiple ore deposits in this region, spanning Sb-only, Sb–Au, and Sb–Pb–Zn ore systems across seven deposits and mineralizations. The principal Sb-bearing mineral in all deposits is stibnite. Mineralogical determination and Sb isotope composition of stibnite have been performed on well selected samples. Antimony isotope composition has the potential to record variability in Sb source reservoirs and the evolution of mineralizing fluids. Measurements were performed in-situ at Leibniz University Hannover using deep UV-fs laser ablation system coupled to MC-ICP-MS, following Kaufmann et al. (2021).
Obtained stibnite δ¹²³Sb values range from -0.69 to +0.81‰ (relative to NIST SRM 3102a). Evident isotope fractionation of 0.94 ‰ measured in stibnite is observed in Sb–Pb–Zn ore deposit, which may indicate several episodes of stibnite formation. In general, other ore deposits show limited antimony isotope fractionation (< 0.45 ‰) within deposit, which is consistent with the well-established Rayleigh crystallization model of fluid evolution. While the maximum deviation within an Sb-Au deposit is ~0.25 ‰, with an average value of -0.07±0.14 ‰ (2SD), the range among Sb-only deposits is much greater, exceeding 1.2 ‰, with the mean of ~0.05±0.67 ‰ (2SD). In one of the Sb-only deposits in northern Tibet, the most negative δ¹²³Sb value of -0.69±0.46 ‰ and a deviation of 0.7 ‰ were observed, while the other deposits in southern Tibet show an intra deposit range below 0.44 ‰ and the lowest values of -0.06 ‰. According to the well-known Sb isotope variations during ore formation, our new data reveal that the metal sources for Sb mineralization in northern and southern Tibet might have been distinct. This may further indicate that the Sb isotopes can be used to constrain metal sources and metallogenic domains at a large scale across the Tibetan Plateau.
Kaufmann, A.B., Lazarov, M., Kiefer S., Majzlan, J., Weyer S. (2021): In-situ determination of antimony isotope ratios in Sb minerals by femtosecond LA-MC-ICP-MS, JAAS 36(7).
How to cite: Jiang, L., Zhai, D., and Lazarov, M.: A newly discovered low Sb isotopic endmember in global Sb ore deposits, evidence from Tibet (SW China), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20372, https://doi.org/10.5194/egusphere-egu26-20372, 2026.
The Jahaz area belongs to the Mesoproterozoic metamorphic rocks of the North Delhi Fold Belt, India, and is composed of garnetiferous quartz biotite schist (GQBS), amphibolite, graphite schist, and quartzite (Jain et al., 2016). It lies within the well-known Na-metasomatic uranium deposits along the “albitite line” of the Khetri Belt, Rajasthan (Ray, 1987). This work involves the whole-rock geochemical analysis of major, trace, and rare-earth elements in less to moderately altered (LTMA) and albitized host rocks, using XRF and ICP-MS. The alteration box plot and isocon analyses were attempted to quantify the exchange of chemical components during fluid-rock interaction. The alteration box plot corroborated the intensity of alterations such as albitization, chloritization, calcitization, actinolitization, sericitization, and linked to the Na-K-Ca-Mg metasomatism, which was responsible for the formation of various altered minerals in the metasomatic rocks (Mishra et al., 2022). The correlation coefficient plots indicated that elements such as Zr, Nb, Hf, and Tiwere less mobile during fluid-rock interaction. Isocon analysis supports the enrichment a positive correlation exists between U and Na, Mo, Cu, Th, Zr, LOI, and LREEs in the zones of intense rock alteration (Grant, 2005). The low Th/U ratio of albitized GQBS indicates that the albitized rocks are significantly enriched in uranium. Therefore, uranium enrichment is positively correlated with Na, Mo, Cu, Th, Zr, LOI, and light rare-earth elements in albitized GQBS, as well as amphibolite, in the Jahaz U-deposit. These enrichment and depletion trends match with the Kirovograd and Novoukrainka (Ukraine), Lagoa Real (Brazil), Valhalla (Australia), Longshoushan (China), Aricheng (Guyana), and Coles Hill (USA) Na-metasomatic Uranium-deposits. The outcome of the present work can be useful to exploration agencies in targeting Na-metasomatic U-deposits more precisely in other areas.
How to cite: Mishra, P., Krishnamurthi, R., Kushwaha, A. P., and Jagadeesan, P.: Quantification of mass transfer during fluid-rock interaction at the Jahaz uranium deposit, North Delhi Fold Belt, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1606, https://doi.org/10.5194/egusphere-egu26-1606, 2026.
Mississippi Valley-type (MVT) deposits are vital sources of lead and zinc, crucial for the energy transition. Giant MVT deposits often occur in fold-thrust systems within collisional orogens, but the processes driving mineralizing fluids remain unclear. Here, we investigate a deep seismic reflection profile and broadband magnetotelluric survey traversing the world-class Jinding MVT deposit in the Sanjiang belt of Tibetan-Himalayan orogen. Our results reveal an upper-crustal fold-thrust system with a deep décollement underlain by a thermal dome at a depth of ~20-40 km that is likely caused by ponding and degassing of hydrous potassic magmas. We suggest that rock dilatancy along the décollement during compressive deformation provided a pathway for the lateral migration of regional ore-forming fluids. Heat, provided by the underlying thermal dome, together with fault channels caused by a transition from regional compression to extension, drove the upward discharge of fluids from the décollement and led to mineralization in the overlying fold-thrust belt. Although MVT deposits have classically been considered unrelated to magmatic activity, our revised model of deposit genesis suggests that intra-crustal magma chambers may drive fluid circulation and make important contributions to the timing and spatial localization of MVT ores in collisional orogens.
How to cite: Liu, Y., Xiong, X., Yu, N., Hoggard, M., and Hou, Z.: Key to formation of Jinding world-class Mississippi Valley-type lead-zinc deposit in the Tibetan-Himalayan orogen, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4166, https://doi.org/10.5194/egusphere-egu26-4166, 2026.
The formation of porphyry Cu–Mo deposits in continental crust frequently encounters the "Cu paradox", where magmas exhibiting the strongest indicators of ore potential (e.g., high Sr/Y) possess the lowest bulk copper concentrations due to early sulfide saturation. This study investigates the magmatic evolution of the Permian–Triassic Oyut Cu–Mo deposit in Central Mongolia to clarify the mechanisms driving magmatic fertility and metal enrichment. Zircon U–Pb geochronology identifies two distinct magmatic stages: a pre-ore barren stage (256–240 Ma) and a subsequent fertile stage (240–227 Ma). Whole-rock data from the ore-bearing suite display typical “fertile magma” signatures, including high Sr/Y ratios and spoon-shaped REE patterns with depleted heavy REEs (HREE). However, Zircon trace element chemistry records a significant redox change: pre-ore suites were more reduced (≈ FMQ buffer), while strong positive Ce anomalies in zircon reflect elevated oxidation state during the emplacement of fertile magmas (log fO₂ ≈ NNO buffer). Zircon εHf(t) values (+0.1 to +10) indicate constant addition of juvenile source, suggesting that high fO₂ was attained during differentiation rather than inherited. Moreover, the high content of HREE suggests that deep crustal garnet fractionation was not the primary driver. Instead, elevated ΣMREE/ΣHREE ratios through time confirm that differentiation was dominated by amphibole fractionation. We propose that water-saturated conditions promoted highly oxidizing conditions and extensive hornblende crystallization, depleting Fe from the melt, lowering sulfide saturation capacity, and triggering early sulfide sequestration as well as apparent Cu depletion. In contrast to the pre-ore reduced magmas, this amphibole-mediated pathway and oxidizing conditions maintained metals in high-solubility sulfate complexes, concentrating the volatiles and chalcophile elements necessary for large-scale Cu–Mo mineralization. These findings highlight hydrous magma and an amphibole fractionation as a key discriminator between barren and fertile magmas in the Central Asian Orogenic Belt.
How to cite: Mueller, T., Ganbat, A., Baatar, M., Bayaraa, B., Dandar, O., Bayarbold, M., Dorjyunden, A., Ochir, G., Genge, M., Long, C. T., Newby, S., Zuo, J., McKenzie, R., and Sorger, D.: Amphibole-driven redox evolution and magmatic fertility at the Oyut Cu–Mo Deposit, Mongolia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19346, https://doi.org/10.5194/egusphere-egu26-19346, 2026.
The previously mined Viscaria Cu-Fe deposit consists of three stratabound orebodies, named the A, B and D zone. Historic copper mining focused on the highest-grade A zone. Sulfide mineralization is distributed within several ore zones of a 1 km thick sequence of steeply tilted volcano-sedimentary Paleoproterozoic greenstones. The deposit was originally interpreted as a syngenetic exhalative deposit, which was partially enriched and altered during subsequent footwall alteration (Martinsson, 1997). Recent exploration with deep drilling by Gruvaktiebolaget Viscaria AB was undertaken with the purpose of restarting copper production and unlocking the exploration potential of the broader mineral system. This work has shone a new light on the deposit by redefining the spatial relations of the alteration zones and uncovering new mineralized lenses at depth, including a mineralized body between the A and B zone, aptly named the ABBA zone. In combination with the proximity to the world-class Kiirunavaara Fe deposit, and its location within a broader metasomatic iron alkali-calcic (MIAC) mineral province, the Viscaria Cu deposit has been reinterpreted by some as an epigenetic IOCG-style deposit (Imaña et al., 2023).
This study investigated the recently discovered ABBA zone to chime in on this ongoing debate. The evolution of the mineral system was first constrained through detailed study of drill core, petrography, mineral geochemistry and lithogeochemistry. These results provided the boundaries in which the geochemical modelling work was fitted by first constructing a detailed mineral paragenesis and conceptual fluid evolution model. Alteration zones in and around the ABBA zone are dominantly replacive, developing into more vein-hosted mineral assemblages over time. The replacive alteration assemblages are well-suited to geochemical modelling, as they indicate pervasive fluid-rock interaction.
Geochemical modelling was performed using the Gibbs Energy Minimization Selektor (GEMS) code package with the MINES 2023 thermodynamic database. A combination of titration, flush and flow-through model set-ups were used to constrain both the influence of the fluid-rock ratio and fluid evolution through fluid-rock interaction. Physiochemical fluid conditions were derived from previous work on the Viscaria deposit, from regionally similar deposits and further constrained by equilibrium with the Viscaria alteration assemblage. The influence on alteration of the diverse volcano-sedimentary host rock sequence, consisting of black schists, basic tuffs and carbonates, was tested. Geochemical fluid-rock interaction modelling shed light on some key ingredients of the Viscaria Cu-Fe mineral system, including host rock composition, physiochemical fluid characteristics, fluid-rock ratios and fluid evolution. The results of this study support an epigenetic origin by fluid-rock interaction with MIAC-style fluids for the Viscaria Cu-Fe deposit.
How to cite: Hegeman, P. and Imaña, M.: Fluid-rock interaction constraints from geochemical modelling of the mineral paragenesis and system of the Viscaria Cu-Fe deposit, Kiruna district, Northern Sweden, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1189, https://doi.org/10.5194/egusphere-egu26-1189, 2026.
The Takab (NW Iran) BIF consists of alternating iron- and silica-rich layers. It formed ca 560 Ma in a back-arc basin from a mixing of seawater and hydrothermal fluids with incorporation of ca. 20% of terrigenous material [1]. The ore bodies are composed of magnetite with various textures (disseminated, banded, lenticular, nodular, and massive) mainly hosted in folded micaschists. The magnetite and/or the matrix may contain accessory minerals, monazite, barite, scheelite, and Fe-Mn-carbonates in nodular magnetite. In this study we show that the different types of magnetite layers recorded a variety of fluid-rocks interactions that occurred at moderate temperature (200-300°C) under variable but mostly reduced fO2.
All magnetite types have low Ni and Cr (10-30 ppm) and V (< 100 ppm), and high Mn (1800-2600 ppm; up to 1% in nodular magnetite), characteristics of hydrothermal magnetite. Ti concentration is also low (15-200 ppm) except in disseminated magnetite, in which Ti (up to 1940 ppm) is correlated with Al and Mg. Moreover, all magnetite types show positive Eu and Y anomalies plus a negative Ce anomaly in nodular magnetite, typical for mixed seawater/hydrothermal fluid precipitation. The negative Ce anomaly of nodular magnetite is similar to that of the calcschist laminates.
The disseminated magnetite shows highly positive ∂56Fe (+1.4 ‰) and ∂18 values (+2.2 ‰) testifying for a magmatic/high-T hydrothermal origin, also suggested by the trace element behavior.
The banded magnetite also shows mostly positive ∂56Fe (up to +1.1 ‰) values, but a lighter oxygen isotopic composition (∂18 values=-2.5 to +1 ‰). This suggests that banded magnetite did not preserve the magmatic/high-T hydrothermal signature unlike disseminated magnetite, and was further affected by a hydrothermal alteration or re-equilibration with low-T fluids.
The nodular magnetite shows important differences from the other two types: mostly light ∂56Fe values, indicative of a low-T hydrothermal fluid signature, and heavy ∂18O (+4 to ‰) values consistent with a magmatic/high-T hydrothermal origin. Decoupling of the Fe and O isotope signature suggests a more complex hydrothermal history. The presence of Cl-bearing apatite inclusion in the nodular magnetite supports the precipitation of low ∂56Fe magnetite from a Cl-bearing hydrothermal fluid. Furthermore, the high ∂18O values possibly suggest a re-equilibration of a magmatic-hydrothermal fluid with carbonate rocks or mixing with fluid in equilibrium with the carbonate in the host rock. A likely scenario is the involvement of CO2-bearing hydrothermal fluids produced during the decarbonatization of the close-by calcschist.
In conclusion, the most characteristic feature of the Takab BIF is the large predominance of the hydrothermal overprint on the volcano-sedimentary sequence throughout the formation and the evolutionary history of the iron ore deposit. The varied chemical and isotopic composition of the different magnetite types and the presence of accessory minerals point out both the variety of the fluids involved and the degree of the Sfluid-rock interactions [2, 3].
[1] Honarmand et al., Precambrian Research, 2024; [2, 3] Wagner et al., Minerals, 2023, 2025.
How to cite: Wagner, C., Rividi, N., Villeneuve, J., Boudouma, O., Nabatian, G., Honarmand, M., Orberger, B., and Monsef, I.: Decoding multistage fluid-rock interactions in the Takab Iranian iron-ore deposit., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6819, https://doi.org/10.5194/egusphere-egu26-6819, 2026.
Savage River is one of the largest iron ore deposits in Australia, yet its genetic classification remains debated. It occurs in the Proterozoic Arthur Metamorphic Complex in northwest Tasmania. Mineralisation dominantly consists of magnetite – an important petrogenetic indicator used for a wide array of applications. This research presents the first study of the paragenesis and composition of magnetite from Savage River, integrating field observations, core logging, petrography, micro-texture and geochemistry. Results indicate four distinct generations of magnetite that give insights into the ore-forming history. Analysis of the results and comparison to published data suggest an iron oxide-apatite (IOA) type genetic affinity for Savage River. Testing was carried out on 40 samples collected from two drill holes in the North Pit of the deposit. Graphic core logging, hyperspectral logging, magnetic susceptibility, backscattered electron imaging (BSE) and automated mineralogy data were used to: (1) identify different magnetite generations based on texture and cross-cutting relationships; (2) differentiate lithologies and host rocks; and (3) understand associated alteration minerals. Trace elements of the four identified magnetite generations were measured using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Magnetite I is massive to semi-massive, with well-developed ulvöspinel/ilmenite exsolution lamellae and it is highly fractured and inclusion poor, with highest Ti (< 1 wt%), V (up to 0.8 wt%) and lowest Ni (up to 378 ppm) concentrations. These characteristics record high-temperature magmatic crystallisation and rapid cooling and represent the earliest iron enrichment in the system. Magnetite II forms euhedral to subhedral grains and show moderately reduced Ti (up to 670 ppm), V (up to 4000 ppm), and increased Ni (up to 637 ppm) contents. Magnetite II partially overgrows Magnetite I, indicating precipitation during an early hydrothermal overprint, marking a transition from magmatic to magmatic–hydrothermal fluid regimes. Magnetite III occurs as subhedral to anhedral grains that are inclusion rich, highly porous, and mostly have hematite replacement on the rims. Its low Ti (up to 670 ppm) and V (up to 234 ppm), elevated Ni (727 ppm), and strongly depleted Cr (up to 0.6 ppm) trace-element signature indicate extensive re-equilibration with evolving lower-temperature fluids. This generation is interpreted to correspond to a major hydrothermal alteration phase involving fluid rock reaction with mafic host rocks. Magnetite IV occurs as fine disseminated subhedral to anhedral grains that are comparatively pristine, and inclusion poor. It exhibits the lowest Ti (up to 426 ppm), V (up to 3000 ppm), and the highest Ni (up to 899 ppm) concentrations, consistent with its precipitation from a highly evolved, oxidised hydrothermal fluid. In addition to Ti and V, other discriminatory trace element (like Mn, Ga, Cr) systematics define a clear vector from high temperature magmatic to low temperature hydrothermal conditions accompanied by increasing oxygen fugacity. Comparisons of Savage River magnetite with magnetite from other deposit types shows the most similarities in texture and magnetite chemistry to those of IOA-type deposits. Collectively, these findings suggest that the four magnetite generations at Savage River deposit record a complete magmatic to hydrothermal continuum.
How to cite: Mondal, P., Missen, O. P., Zhang, L., Hunt, J., Lygin, A., Fathi, M., Belousov, I., and Hill, R.: Magmatic to Hydrothermal Evolution: Insights from Savage River Magnetite Deposit, Tasmania, Australia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-581, https://doi.org/10.5194/egusphere-egu26-581, 2026.
Tungsten (W) is a highly incompatible element enriched in the crust through time and closely associated with granitic magmatism. While reduced-conditions have long been emphasized as the critical control, many reduced granites are barren, indicating redox alone is insufficient. Here we examine the giant Hukeng W deposit in the Wugongshan Complex in South China to identify the fundamental factors controlling W-fertility. Integrated zircon geochronology, Lu–Hf isotopes and trace element data, wolframite geochronology, and whole-rock geochemistry of the W-related Hukeng and barren Caledonian–Jurassic granites demonstrate that Hukeng formed at ~150 Ma. The Hukeng granite, derived from Paleo-Proterozoic metasedimentary crust, had underwent extreme differentiation (DI ≈ 95) and fluid–melt interaction. It exhibits strong Ba–Sr–Eu–Ti depletion, high Rb/Sr (~18) and K/Ba (~740), low K/Rb (~79), La/Ta (<2.1), (La/Yb)N (<3.6), Zr/Hf (~18) and Nb/Ta (~7.6), significantly negative Eu anomalies ((Eu/Eu*)N <0.12), and pronounced lanthanide tetrad effects (TE1,3 ≈ 1.19). Zircons display decreasing negative Eu and increasing positive Ce anomalies through advanced magma fractionation and fluid–melt interaction under reduced conditions. In contrast, barren granites, though more reduced, display weaker differentiation and minimal fluid signatures. We conclude that the combination of fertile-crust source, extreme differentiation, and vigorous fluid exsolution—rather than oxygen fugacity—was decisive in concentrating and precipitating W. A discriminant model based on DI >88, TE1,3 > 0.96, (Eu/Eu*)N <0.4, K/Rb <105, Rb/Sr >7, La/Ta < 6, (La/Yb)N <6, Zr/Hf < 38, and Nb/Ta <10 provides refined exploration criteria for W-related granites in South China and globally.
How to cite: zhang, Y. and he, X.: Magma Source, Differentiation, and Fluid-Melt Interaction as Controls on W Fertility: Insights from the Hukeng W Deposit, South China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8428, https://doi.org/10.5194/egusphere-egu26-8428, 2026.
The reported coexisting Cu and W mineralization of economic significance in single ore deposit worldwide is rare. However, both Cu and W mineralization have been discovered in the giant Zhuxi W‒Cu deposit in South China. To address the genetic relations between the shallow Cu and deep W mineralization in this giant ore system, here we report U‒Pb dating, trace element and Hf isotope data of zircon from the Cu-related granodiorite porphyry, U‒Pb dating and trace element data for hydrothermal titanite and S isotopic data for sulfide related to Cu mineralization. The U‒Pb ages of zircons from two granodiorite porphyry samples are 155.7 ± 0.8 Ma and 152.5 ± 0.7 Ma, respectively, which are consistent with the U‒Pb age of the hydrothermal titanites of 154.5 ± 5.0 Ma, suggesting that the shallow Cu mineralization formed in the late Jurassic and was simultaneously associated with the deep giant W mineralization at Zhuxi. Trace element composition of titanites favor a high fH2O and relatively low fO2 environment for Cu formation. Sulfides exhibit δ34S values ranging from –0.9‰ to 3.5‰, indicating a magmatic origin. Zircons from the granodiorite porphyry present εHf(t) values of −9.9 to 1.3, suggesting that the Cu ore-related granodiorite magmas were derived mainly from the partial melting of Cu-enriched metavolcanoclastic rocks with minor mantle sources. Trace element composition of zircons indicate a magma mixing process with high-temperature melts >750°C that are relatively rich in Y, Th and rare earth elements but with lower Hf concentrations, being added to relatively low-temperature ~700°C crustal-derived granodiorite magmas. Combining the above data and previously determined zircon Lu–Hf isotopes, we propose that the Cu and W in Zhuxi may have been derived mainly from the partial melting of Cu-enriched metavolcanoclastic rocks and W-enriched metasedimentary sequences of the Neoproterozoic juvenile crust, respectively. The intrusion of the Cu-related granodiorite porphyry should have been triggered by the upwelling of heated mafic magmas from the asthenospheric mantle during the Late Jurassic lithospheric compressional–extensional conversion stage.
How to cite: He, X.: How can Cu-W mineralization be economically co-enriched in single deposits?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8677, https://doi.org/10.5194/egusphere-egu26-8677, 2026.
Cassiterite (SnO₂) is the main tin ore mineral. Hence, understanding the controlling factors for cassiterite crystallization/precipitation are a crucial basis for developing ore deposit models for exploration and mining.
The precipitation of cassiterite is inherently linked to a change in Sn speciation, from Sn²⁺ in silicate melts or hydrothermal fluids to Sn⁴⁺ in the oxide mineral. The preferential enrichment of heavier Sn isotopes in oxidized Sn⁴⁺ species makes variations in Sn isotope ratios a promising tool allowing to constrain redox conditions during transport, concentration, and deposition. To better understand Sn-isotope fractionation in ore-forming environments, we examined cassiterite from a magmatic and magmatic-hydrothermal occurrence: the Argemela rare-metal granite system in Portugal and the Sadisdorf greisen system in Germany, because they represent different environments of Sn mobilization and deposition, namely mainly melt-driven at Argemela (magmatic cassiterite) and fluid-driven at Sadisdorf (hydrothermal cassiterite). High-resolution, in situ measurements of Sn isotopes and trace elements were carried out on distinct growth zones within individual cassiterite crystals using UV femtosecond laser ablation multi-collector ICP-MS. The results reveal clear contrasts between magmatic and hydrothermal cassiterite. Hydrothermal cassiterite from Sadisdorf commonly displays elevated W contents and an increase in δ124/117Sn values from core to rim, suggesting that oxidation occurred during precipitation. At Sadisdorf, vein-hosted cassiterite shows a spatial trend from positive δ124/117Sn values in proximal greisen to negative δ124/117Sn values in more distal veins. This systematic difference suggests progressive reduction along the fluid flow path, recorded in the Sn isotope signatures. In contrast, cassiterite crystals from Argemela are enriched in Nb and Ta, and some grains show decreasing δ124/117Sn values toward their crystal rims, which can be explained by Rayleigh crystallization.
These preliminary findings indicate that Sn isotopes are a suitable tracer of redox conditions and processes during Sn transport and cassiterite crystallisation. Ongoing Li isotope analyses of Li-bearing micas will provide additional constraints on the nature of the fluid and ore-forming conditions in both granitic systems.
How to cite: Ebert, K., Michaud, J. A.-S., Holtz, F., Leopardi, D., Wiegel, P., Horn, I., Burisch, M., and Weyer, S.: Contrasting Sn isotope signatures in cassiterites of melt- and fluid-dominated granitic ore systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19489, https://doi.org/10.5194/egusphere-egu26-19489, 2026.
Lithium-rich pegmatites and granites are commonly thought to form either by extreme fractionation of granitic magmas or low-degree crustal melting. Yet, decades of debate leave striking questions unresolved. What are the mechanisms of Li release during crustal melting? Can crustal melting alone ever produce Li concentrations high enough to matter economically? These questions are particularly timely, as the idea that crustal anatexis alone can generate melts with sufficient Li to form economically viable ore deposits has gained renewed attention. Here, we present the first comprehensive database of Li concentrations in anatectic melt inclusions (i.e., melt inclusions hosted in perictectic minerals of migmatites and granulites), providing direct empirical constraints on the Li budget of primary crustal melts formed under common mid- to lower-crustal P–T–Xbulk conditions.
Lithium concentrations in these melts reach a maximum of ~600 μg/g during the earliest stages of fluid-absent biotite melting at 750–800 °C in cordierite-free metasedimentary rocks. Although these values are two to three times higher than those of typical S-type granites, they overlap the range of barren pegmatites and remain far below those of Li ore-forming systems. Integration of this dataset with thermodynamic and geochemical modelling shows that melting of Li-enriched sources or multi-stage melting can locally enhance melt Li contents, but are unlikely to directly generate high-grade Li deposits without subsequent melt differentiation. Without compelling evidence that strongly pre-enriched sources can preserve extreme Li anomalies (10 to 200 times crustal values) up to anatectic conditions, extreme post-anatectic differentiation emerges as a necessary condition for generating economically viable Li deposits. Nature demands more than a melting source: high-grade Li deposits of anatectic origin are earned in the details of differentiation.
Melt inclusions in anatectic rocks thus represent robust quantitative tracers of critical metal mobility, opening new avenues for future interrogation of fertile anatectic systems.
How to cite: Bartoli, O., B. Carvalho, B., Acosta-Vigil, A., Petrelli, M., Tacchetto, T., D. A. Rickard, W., and Wälle, M.: Rewriting Lithium’s Anatectic Narrative: A Hierarchical Framework for Mobility and Enrichment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3441, https://doi.org/10.5194/egusphere-egu26-3441, 2026.
South China is a globally significant concentration area of fluorite deposits. Significant genetic differentiation is observed in fluorite deposits across different tectonic units due to variations in their associated mineral assemblages, yet their metallogenic dynamic settings and material sources remain unclear. A research team investigated typical fluorite deposits in the western margin of the Sichuan Basin (associated with lead-zinc deposits), its eastern margin (associated with barite), and the Zhejiang-Jiangxi region (associated with quartz). The research team, by integrating Sm-Nd geochronology, microthermometry of fluid inclusions, H-O-S-Sr-Pb isotopic tracing, and in-situ LA-ICP-MS trace element analysis, aimed to reveal why large-scale fluorite mineralization occurred in South China.
In the Zhejiang-Jiangxi region, fluorite is often associated with quartz, and the mineralization age is concentrated in the Late Cretaceous to Early Cenozoic. The ore-forming fluids were predominantly meteoric water, characterized by low temperature and low salinity. Rare earth elements and isotopic signatures indicate that the ore-forming materials were mainly derived from water-rock reactions involving fluorine-rich volcanic rocks and basement metamorphic rocks. Mineralization was controlled by extensional faults triggered by the retreat of the Pacific Plate. The eastern margin of the Sichuan Basin hosts widely developed MVT-type barite-fluorite deposits, which formed mainly during the Late Cretaceous. The tectonic setting is related to regional extension caused by the subduction of the Paleo-Pacific Plate. The ore-forming fluids were a mixed system of basin brines and meteoric water. Sr isotopes and rare earth elements suggest that the ore-forming materials were derived from Cambrian carbonate rocks, black shales, and Ordovician limestones. The western margin of the Sichuan Basin is a key area where fluorite is associated with lead-zinc deposits. Mineralization occurred mainly during the Late Triassic, related to the Indosinian orogeny following the closure of the Paleo-Tethys Ocean. The ore-forming fluids exhibited medium-low temperature and medium-low salinity characteristics. The coexistence of high- and low-salinity fluid inclusions, along with H-O isotopic data, indicates that the fluids were a mixture of basement metamorphic water, basin brines, and meteoric water. Sr-Pb isotopes and rare earth element characteristics show that the ore-forming materials were mainly sourced from Precambrian basement rocks and Cambrian sedimentary strata (e.g., black shales).
In summary, fluorite deposits in South China mainly formed during the Mesozoic–Cenozoic, with mineralization ages generally exhibiting a trend of being older in the west and younger in the east. The ore-forming fluids were dominated by meteoric water or basin brines, and the ore-forming materials were derived from fluorine-rich volcanic rocks and sedimentary strata, respectively. Tectonically, mineralization was controlled by two major dynamic systems: the closure of the Paleo-Tethys Ocean (western margin) and the subduction of the Paleo-Pacific Plate (eastern margin and Zhejiang-Jiangxi region).
How to cite: Zou, H., Liang, S., and Cao, H.: The reasons for large-scale fluorite mineralization in South China during the Mesozoic-Cenozoic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2137, https://doi.org/10.5194/egusphere-egu26-2137, 2026.
The middle-Miocene volcano-sedimentary succession of Akita Prefecture, Northeast Japan, hosts a well-studied example of felsic volcanic-hosted massive sulphide deposits, known as “Kuroko”, which represent the type locality for this type of deposits worldwide. These have long been used as a model for understanding similar ore deposits occurring in other localities and across the geological time. The main commodities extracted from this type of ore are Zn, Cu and Pb, with locally significant amounts of Au and Ag as by-products.
In this study, we combine major and trace element analyses (including Au and Ag) with high-precision Pb isotope analyses of ore samples from Akita Prefecture and evaluate their co-variations in order to understand the source of base and precious metals in these deposits. We also compile previous Pb isotope analyses to obtain a wider view of the isotopic value distributions at the district scale. Lead isotope maps based on this dataset were compared with geological features, such as the orientation of main Miocene faults and basement depth to assess the possible effects of such features on Pb isotopic composition of hydrothermal deposits.
The highest values of Au (up to ca. 120 ppm) and Ag (up to ca. 7000 ppm) were observed in sphalerite-rich “black ore” samples from Matsumine and Shakanai deposits. Petrographic observations and mineral analyses in these samples indicate that the main host for precious metals are sulfosalts, such as tennantite-tetrahedrite and pearceite [Cu (Ag,Cu)6 Ag9 As2 S11]-polybasite [Cu (Ag,Cu)6 Ag9 Sb2 S11]. Electrum occurs at Au-Ag hosts phase of Nurukawa and Furutobe deposits, along with tennantite-tetrahedrite. In Matsumine and Shakanai samples, positive correlations in plots of Pb isotopic ratio 207Pb/204Pb vs Zn, Pb, Au and Ag point to contributions of these metals mostly from isotopically evolved sources (the pre-Miocene basement). Anticorrelation between 207Pb/204Pb and Cu indicates a relatively unradiogenic source for Cu (the Miocene volcanic rocks). The maps of 207Pb/204Pb and 206Pb/204Pb indicate a prominent N-S distribution of values, parallel to the orientation of the main Miocene faults and the elongation of Miocene rifts, reflecting the paths of hydrothermal fluid circulation. The Cretaceous Pb model ages of ore samples (ca. 80–140 Ma) are significantly older than the middle-Miocene formation age, and overlap with the ages of basement granites. In addition, a comparison of the map of Pb model ages at the district scale with the map of the basement depth indicates progressively older model ages occurring to the northeast, in areas where the basement becomes shallower. Lead with such “old” isotopic ratios was likely preserved in feldspar of Cretaceous basement granites, and remobilised during fluid circulation in the middle-Miocene. We propose a model that involves an isotopically juvenile source (the Miocene volcanic rocks) providing Cu and an isotopically evolved source providing much of Zn, Au and Ag to the mineralising fluids.
How to cite: Agangi, A., Nopeia, M., Didari, A., Takahashi, R., Manalo, P., Ueckermann, H., and Iaccheri, L.: The sources of base and precious metals in Kuroko deposits of NE Japan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10358, https://doi.org/10.5194/egusphere-egu26-10358, 2026.
The Tizi-n-Isdid manganese deposit, located along the western margin of the Ouzellarh Precambrian promontory in the western High Atlas, represents a key example of hydrothermally stratiform-type manganese ore deposit formed during the late Ediacaran to early Cambrian transition. This study integrates field observations, petrography, SEM-EDS analyses, automated mineralogical mapping and whole-rock geochemistry to reconstruct the mineralogical evolution and origin of the deposit. Macroscopic observations reveal massive, banded and brecciated Mn-rich bands hosted within lower Cambrian claystones (Adoudou Formation), with MnO contents ranging from 21 wt.% to 49 wt.%. The ore is dominated by braunite, piemontite, hollandite-group minerals, cryptomelane, pyrolusite, and subordinate amounts of barite and carbonate minerals. Textural relationships identify four successive stages: a detrital pre-ore stage; an early hydrothermal silicification stage; a carbonatation stage marked by brecciation and barite–carbonate veining; and a final near-surface oxidation stage.
Mn mineralization is closely related to hydrothermal fluid–rock interactions involving a mixed magmatic–meteoric fluid system. Meteoric waters infiltrated through permeable fault zones and sedimentary units, were progressively heated at depth by interaction with magmatic heat sources, and evolved into reactive hydrothermal fluids. During their ascent along fault-controlled pathways, these fluids efficiently leached Mn from the volcanic and crystalline basement rocks. Subsequent changes in temperature, redox conditions and fluid composition during discharge onto a shallow marine platform promoted Mn precipitation and the development of stratiform mineralization within clay-rich sediments.
Major and trace elements (Mn/Fe, Co/Ni, Co/Zn) consistently indicate a hydrothermal origin, while REE patterns, characterized by low ΣREE, strong negative Ce anomalies, positive Eu anomalies, HREE enrichment and high Y/Ho ratios, reflect the mixing of Mn-rich hydrothermal fluids with oxic seawater on a shallow platform. Structural and tectonic evidence links ore formation to late Ediacaran N–S extension, fault-controlled hydrothermal circulation and early Cambrian marine transgression. These combined mineralogical, geochemical and geological data support a genetic model in which Mn was leached from volcanic and basement rocks, transported upward along normal faults and precipitated syngenetically with clay-rich sediments in an oxygenated marine environment.
How to cite: Aflla, I., Ilmen, S., Souhassou, M., Dekoninck, A., Jabbour, M., El Ouad, Z., Zouhair, M., Maacha, L., and bouskri, I.: Hydrothermal fluid–rock interactions and subsurface Mn leaching controlling stratiform Mn mineralization in the Tizi-n’Isdid district (Western High Atlas, Morocco): insights from ore mineralogy, paragenesis, and geochemical evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2628, https://doi.org/10.5194/egusphere-egu26-2628, 2026.
Abstact：The Qaidam Basin is a large-scale Cenozoic intermontane closed fault-depression basin in the northern part of the Qinghai-Tibet Plateau. Controlled by the plateau uplift and the dry-cold, cool-humid, dry-cold climatic cycles, it has formed lithium-rich salt lakes through arid evaporation and concentration, and possesses favorable conditions for salt formation in "high mountain and deep basin" settings.
In terms of geological background, the basin is an irregular rhomboidal water-collecting graben basin extending in the NW-SE direction, covering an area of approximately 255,000 km², with 12 types of proven minerals. Regarding spatiotemporal distribution, halite and gypsum are present in the Shizuigou structural area during the Oligocene; potassium-rich deep brines developed in areas such as Nanyishan during the Pliocene; and thenardite, halite, and potassium-magnesium salts formed in the Early Pleistocene.
In terms of mineralization units and mineral resources, the formation of the basin can be traced back to the Mesozoic Era, and it is currently divided into 5 mineralization units (e.g., the Boron-Potassium-Magnesium Salt-Oil Fault Step Zone in the Northern Margin of Qaidam). There are 33 salt lakes of varying sizes in the basin, with key development areas including Chahan, East and West Taijinar-Yiliping. The cumulative proven salt lake resources amount to approximately 400 billion tons, and 55 ore deposits (31 of which are large-scale or above) have been discovered, involving 12 types of minerals such as lithium (brine), strontium, and potash. A mineralization model has also been established.
The division of mineralization series adheres to the principles of sedimentary basin evolution, geological process correlation, and reflection of the latest exploration results. Two mineralization series and 5 sub-series have been identified, including the Paleogene-Neogene potassium-lithium-boron-strontium-gypsum ore deposit series related to deep fluid and sedimentary superposition, and the Quaternary potassium-sodium-magnesium-lithium-boron-strontium-halite-trona and clay-lithium ore deposit series related to sedimentation.
The conclusions point out that 55 ore deposits and 12 types of minerals have been discovered in the basin; the piedmont glutenite-type potassium-rich deep brines and the mid-western anticline zone fracture-cave-type lithium-rich deep brines have huge reserves and are key breakthrough areas for ore prospecting; the first division of 2 mineralization series and 5 sub-series has improved the mineralization theory and provided guidance for subsequent exploration.
Keywords：Qaidam Basin; Potash； Mineralization Characteristics;Prospecting Potential; Salt Lakes
How to cite: Pan, T., Zhu, C., zhang, J., zhang, S., and chen, X.: Mineralization Characteristics and Prospecting Potential of Potash in the Qaidam Basin，Qinghai Province, China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-368, https://doi.org/10.5194/egusphere-egu26-368, 2026.
In peraluminous, rare-metal granites associated with tungsten (W) mineralization, greisen alteration is common. However, the economic locus of wolframite [(Fe,Mn)WO4] varies between endogreisen within the granite and quartz-dominated vein systems hosted by granite and/or country rocks. This study evaluates how feldspar availability, halogen-controlled melt–fluid evolution, and Fe–W mass transfer govern the degree of endogreisen development and wolframite localization. We compare two Neoproterozoic granite-associated ore systems from the W (±Sn) province of NW India: Degana and Balda. At Degana, the abundance of magmatic topaz indicates an F-rich late-magmatic evolution and high effective F activity in the melt–fluid system. We interpret Na–F (±Na–Al–F) complexing to have reduced early albite saturation, favouring a sodic, albite-rich residual granite. Metasomatic textures record pervasive potassic overprinting along feldspar-rich reaction fronts, which pre-conditioned the granite for subsequent low-pH greisen alteration. Feldspar-destructive reaction fronts then produced pervasive quartz–muscovite endogreisen with secondary topaz and fluorite, within which wolframite precipitated. Isocon-based whole-rock mass-balance constraints indicate net Fe addition and strong alkali loss (ΔCi/Ci0 ≈ +0.82 for Fe; ≈ –1.32 for Na+K), together with enrichment of W and granitophile elements (Li, Sn, Rb). These gains and losses are consistent with their transport by granite-derived magmatic–hydrothermal H2O–CO2 brines of moderate–high salinity (~12–22 wt% NaCl equiv.).
Balda represents a contrasting end-member in both melt evolution and hydrothermal halogen budget. Magmatic topaz is scarce, implying lower effective F activity during late differentiation than at Degana; early feldspar stability and fractionation yielded a comparatively feldspar-poor granite. Reduced feldspar buffering capacity, together with limited F-assisted feldspar hydrolysis, restricted both potassic and subsequent greisen overprinting, producing discontinuous, weakly developed tourmaline-rich endogreisen that lacks hydrothermal topaz and fluorite. Despite this, Balda endogreisen records pronounced Fe addition and rare-metal enrichment relative to unaltered granite, with Fe and associated metals (W–Sn–Li) hosted in Fe-rich micas and tourmaline. Wolframite is not observed in either endogreisen within the granite or exogreisen developed in metapelitic country rocks; instead, it is confined to metapelite-hosted quartz–tourmaline veins, where decompression-driven immiscibility of H2O–CO2 fluids and wall-rock buffering likely increased pH and promoted wolframite saturation. Together, Degana and Balda demonstrate that Fe and rare-metal enrichment in endogreisen is common but not sufficient for wolframite precipitation. Economic endogreisen-hosted wolframite mineralization requires concurrence of F-assisted feldspar destruction with adequate feldspar buffering capacity—conditions better expressed in the F-dominant Degana system than in the tourmaline-rich (B-dominant) Balda system.
How to cite: Bhattacharya, S. and Roy, J. K.: F-dominant versus B-dominant granite–greisen systems of Degana–Balda, NW India: controls on endogreisen development and wolframite deposition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18314, https://doi.org/10.5194/egusphere-egu26-18314, 2026.
How to cite: Fatzaun, M.: Spatio-temporal scales of fluid transport and reaction during ore formation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20701, https://doi.org/10.5194/egusphere-egu26-20701, 2026.
The Akbaştepe Au–Ag mineralization is located in the Söğüt district (Bilecik, NW Türkiye), within the Sakarya Zone on the northern margin of the İzmir–Ankara–Erzincan Suture Zone. The deposit is hosted by greenschist-facies schists of the Nilüfer Formation and occurs as a steeply dipping, N70W-trending quartz vein system extending for approximately 2 km with an average thickness of ∼5 m. The geometry and orientation of the vein system indicate strong structural control related to late-stage orogenic deformation.
This study integrates ore petrography, alteration mineralogy, whole-rock geochemistry, and sulfur isotope data to constrain the role of fluid–rock interaction and metal mobilization during the formation of the Akbaştepe mineralization. Reflected-light microscopy reveals a multi-stage paragenesis dominated by pyrite, arsenopyrite, scheelite, Hg–Te minerals (coloradoite), and Au–Te phases, with native gold occurring both as free grains (15–95 µm) and as inclusions within fractured and oxidized pyrite. Multiple generations of pyrite indicate episodic fluid flow and repeated mineralizing events within structurally prepared zones.
Hydrothermal alteration is characterized by silicification, carbonatization, and Fe-oxidation, overprinting the primary greenschist assemblage. Alteration mineralogy records progressive fluid–rock interaction, marked by a systematic transition from chlorite-dominated greenschist facies toward smectite-, kaolinite-, and illite-bearing assemblages localized along mineralized and shear zones. The inverse relationship between chlorite and smectite reflects increasing chemical re-equilibration between hydrothermal fluids and reactive host rocks, emphasizing the role of alteration processes in controlling metal precipitation.
Whole-rock geochemical data show Au contents up to 10 ppm and consistently high Au/Ag ratios, reflecting gold-dominated mineralization. Gold exhibits strong positive correlations with As, Hg, W, and Sb, whereas base metal concentrations remain low. This elemental association is characteristic of orogenic gold systems and indicates efficient metal mobilization controlled by fluid chemistry and wall-rock interaction. The presence of scheelite and Hg–Te phases further supports a chemically reactive ore-forming system.
Sulfur isotope compositions of pyrite and arsenopyrite range between –2.1‰ and –8.8‰ (δ³⁴S), suggesting a sedimentary sulfur source, most likely related to devolatilization of subducted marine sediments. The close mineralogical association between gold and Fe-sulfides highlights the key role of sulfide precipitation during fluid–rock interaction.
The integration of ore petrography, geochemical signatures, and sulfur isotope data indicates that the Akbaştepe Au–Ag mineralization represents a structurally controlled orogenic gold system formed during crustal-scale fluid flow. Gold deposition was governed by chemical reactions between metamorphic fluids and reactive host rocks, leading to efficient metal precipitation along shear zones. These results provide new insights into orogenic gold metallogeny within the Sakarya Zone and contribute to a broader understanding of fluid–rock interaction processes in convergent tectonic environments.
How to cite: Toygar Sagin, O. and Cesur, D.: Chemical Fingerprints of an Orogenic Gold System: Fluid–Rock Interaction and Metal Mobilization in the Akbaştepe Au–Ag Deposit (Bilecik, NW Türkiye) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10674, https://doi.org/10.5194/egusphere-egu26-10674, 2026.
The Qinglonggou gold deposit is a largescale deposit located within the Tanjianshan gold orefield on the northern margin of the Qaidam Basin. Recent exploration has achieved significant breakthroughs at depth and along its periphery; however, the occurrence of gold in deep ores and the evolution of the oreforming fluids remain debated. This research methodology integrated detailed field investigations and drill core logging with systematic mineralogical and geochemical analyses. These included electron probe microanalysis (EPMA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for in-situ trace elements, and laser ablation multi-collector ICP-MS (LA-MC-ICP-MS) for in-situ sulfur isotope analysis of pyrite, arsenopyrite, and native gold from the main mineralization stages (III–V).
The results indicate that gold primarily occurs as nanoscale inclusions within main-stage pyrite (Py3, Py4, Py5) and arsenopyrite, with minor amounts found as native gold filling fractures in pyrite or calcite. Geochemical data from pyrite reveal an evolution in fluid composition from Stage III to Stage V, marked by systematic variations in Co/Ni ratios, As content, and trace elements (e.g., Au, Ag, Cu, Sb). This reflects a transition from moderate-temperature to higher-temperature conditions. Stage IV witnessed intense fluid boiling, which was a critical mechanism for the large-scale precipitation of gold. In-situ sulfur isotope analyses demonstrate a multi-sourced sulfur system: Stage III sulfur is predominantly magmatic-hydrothermal (δ³⁴S: +5‰ to +20‰), Stage IV shows significant seawater influence (δ³⁴S up to +25‰), and Stage V indicates a mixed source. Furthermore, platinum-group element (PGE) signatures and high Bi contents suggest a potential contribution of mantle-derived or deep magmatic components to the ore-forming materials.
In conclusion, the Qinglonggou deposit formed through multiple overprinting hydrothermal events. Early mineralization (Stage III) produced As-rich, Au-poor pyrite in an island-arc setting. The main gold mineralization (Stage IV) was triggered by fluid boiling accompanied by seawater mixing, leading to gold enrichment in arsenopyrite and native gold. A later fluid pulse (Stage V), possibly involving new As-rich fluid and mantle-derived components, further complicated the system. This study provides key geochemical constraints on the metallogenic processes in the Tanjianshan area.
How to cite: Chen, M., Wang, G., Zhao, W., and Xie, H.: Gold Occurrence and Evolution of OreForming Fluids of the Qinglonggou Gold Deposit, Northern Margin of Qaidam Basin, Qinghai Province, China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15997, https://doi.org/10.5194/egusphere-egu26-15997, 2026.
The Tongbai Orogen, located in the Qinling–Tongbai–Dabie orogenic belt, contains numerous lode Au–Ag deposits, yet the relative roles of Paleozoic orogenic processes and Mesozoic magmatism in their formation remain controversial. In the Weishancheng ore field, Au–Ag mineralization is spatially associated with structures formed during Paleozoic deformation, but available age constraints suggest a much younger mineralization event.
We conducted an integrated study combining in situ U–Pb dating of titanite from metamorphic rocks and xenotime from ore veins, petrography and LA–ICP–MS trace-element analysis of pyrite and marcasite, in situ S–Pb isotopes, and EPMA/TOF-SIMS element mapping. Titanite records two Silurian–Devonian metamorphic events, indicating prolonged Paleozoic tectonometamorphism. Pyrite related to these events locally contains elevated Au, suggesting that early metamorphism was capable of mobilizing gold from the sedimentary sequence and modifying the chemical conditions of the host rocks.
In contrast, xenotime from ore-stage veins yields consistent Early Cretaceous U–Pb ages of ~125 Ma, directly constraining the timing of lode Au–Ag mineralization. Ore sulfides show a systematic chemical evolution from Co–Ni-bearing pyrite to As-rich pyrite with invisible Au–Ag, followed by Ag–Sb-enriched pyrite and late marcasite. Their restricted sulfur isotope compositions and uniform Pb isotopic signatures differ from those of the ore-host strata and regional basement, indicating that the ore-forming fluids were not dominated by metamorphic devolatilization. Instead, the geochemical and geochronological data are consistent with a magmatic–hydrothermal origin related to Early Cretaceous intrusions.
These results suggest that Paleozoic orogenesis primarily established favorable structures and locally redistributed gold, whereas Early Cretaceous magmatism provided the heat and fluids responsible for economically significant Au–Ag mineralization. The Tongbai Orogen therefore represents a case where mineralization reflects the superposition of multiple orogenic processes rather than a single tectonic event.
How to cite: Zhou, J.-J. and Li, Z.-K.: Regional Metamorphism, Magmatism and Lode Au–Ag Mineralization Controlled by Composite Orogenesis in the Tongbai Orogen, Central China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6131, https://doi.org/10.5194/egusphere-egu26-6131, 2026.
The study area is located in southern Switzerland and forms part of the pre-Alpine basement of the Southern Alps. It is situated within a tectonically and structurally complex setting at the frontal zone of the south-verging thrust of the Upper Orobic Nappe over the Varesotto slices. The area is bounded to the west by the Variscan or post-Variscan Val Colla Fault and to the east by the Lugano Fault, which formed during Jurassic extension and was later reactivated during Alpine compression. The exposed lithologies are dominated by paragneisses, schists, and orthogneisses affected by Variscan amphibolite-facies metamorphism, locally preserving mafic relics recording eclogite-facies conditions. During the Alpine cycle, including Jurassic extension and Cenozoic collision, these rocks likely remained at temperatures below ca. 180 °C. Heavy-metal mineralisation, including gold occurrences, has traditionally been associated with the Val Colla Fault; however, its age remains poorly constrained and may be Permian, Jurassic, or Cenozoic.
Here, we present new geological and structural maps and cross-sections, combined with petrological investigations, whole-rock geochemical analyses (major and trace elements), and electron-microprobe data, to characterise heavy-metal mineralisation along a transect between the Val Colla and Lugano faults, where a new motorway tunnel is planned. Our results show that heavy-metal enrichment along the future tunnel trace is not pervasive, but rather localised and strongly structurally controlled. Mineralisation is preferentially associated with (i) NE–SW-striking faults with left-lateral strike-slip kinematics and a normal component, and (ii) NW–SE-striking normal faults. Enrichment is concentrated within ductile–brittle fault zones, particularly in dark cataclasites, locally graphite-rich, and in mylonitic gneisses, whereas light-coloured gneisses and porphyrites are largely barren.
Elevated concentrations of As, Sb, and Zn are linked to fine-grained sulfides (<100–200 µm), including arsenopyrite, bournonite, boulangerite, and sphalerite, hosted in intensely deformed rocks and carbonate veins formed during the circulation of alkaline, carbonate-rich fluids. Microprobe analyses indicate that vein carbonates are commonly iron-rich dolomite–ankerite and, locally, magnesium-rich siderite. Overall, our findings highlight deformation zones as the primary pathways and traps for heavy metals. Finally, we provide first-order estimates of heavy-metal concentrations in tunnel excavation waste to evaluate its potential as a source of sub-economic raw materials after selective treatment and enrichment aimed at increasing metal concentrations and reducing environmental risk.
How to cite: Schenker, F. L., Grisgnaschi, A., and Casale, M.: The Heavy-Metal Enrichment in Fault Zones of the South Alpine Basement: Implications for Excavation Waste Valorisation , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21759, https://doi.org/10.5194/egusphere-egu26-21759, 2026.
Uranium is a strategically important metal with applications in nuclear energy, medicine, radiometric dating, food processing, industrial radiography, material sciences, and catalysis. This study presents a detailed microtextural and geochemical investigation of uranium mineralization from the Bodal uranium mine, Mohla-Manpur-Chowki, Central India. Uranium occurs as both crystalline and colloidal precipitates, with coffinite [U(SiO4)1-x(OH)4x] and gummite representing the dominant uranium-bearing phases. The mineralization is spatially and genetically associated with altered metabasalts. Petrographic and geochemical evidence indicates that late-stage hydrothermal alteration played a crucial role in uranium remobilization and ore enrichment. Sulphide minerals, including cobaltite (CoAsS), galena (PbS), arsenopyrite (FeAsS), and chalcopyrite (CuFeS2), are intimately associated with uranium phases and likely acted as effective reductants and sorption substrates, facilitating uranium precipitation under reducing conditions. The ore assemblage is accompanied by abundant accessory minerals such as zircon, allanite, and apatite. Substitution of U4+ for Zr4+ in zircon locally records uranium-rich hydrothermal fluids and contributes to zirconium enrichment. Collectively, these observations suggest that hydrothermal fluid–rock interaction and redox-controlled precipitation were the dominant processes responsible for uranium enrichment at the Bodal mine.
Keywords: Uranium mineralization; Hydrothermal alteration; Redox-controlled precipitation; Bodal mine; Central India
How to cite: Ganveer, S., Mallick, S. P., and Pruseth, K. L.: Hydrothermal remobilization and redox trapping of uranium in metabasalts of the Bodal mine, Central India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11094, https://doi.org/10.5194/egusphere-egu26-11094, 2026.
The Brabant Mckenzie (BMK) Cu, Zn, VMS deposit is hosted within a package of highly deformed and high grade metamorphosed bimodal volcanics, likely representing a backarc basin setting, inverted during the Trans Hudson Orogeny. Mineralization comprises massive to semi massive sphalerite-pyrrhotite-pyrite and chalcopyrite contained within two major zones up to 18 m in width and part of a regional prospective trend.
VMS associated chlorite-sericite hydrothermal alteration protoliths are defined by coarse anthophyllite-cordierite-biotite-garnet assemblages in both the hangingwall and footwall of the sulphides. Detailed structural mapping and 3D modelling support a complex structural history with at least 5 deformation events (D1 to D5). Significant VMS remobilization, with durchbewegung texture, occurred during D2, synchronous with peak metamorphism, anatexis, and the pervasive syn-migmatitic S2 foliation. S2 is folded by D3, F3 folds with a scatter of F3 orientations suggesting either progressive D2-D3 noncylindrical ptygmatitc folds or subsequent refolding of F3 axes. Mineral stretching lineations are locally developed and parallel the F3 fold axes. Late stage D4 brittle ductile shears were synchronous with pegmatite emplacement. Pegmatites subparallel and transgress the dominant S2 foliation and remobilized sulphides resulting in sphalerite, chalcopyrite and lesser gahnite spots, and locally coarse galena. Final D5 brittle faulting is associated with minor offsets.
How to cite: Uken, R., Shmyr, J., Cawood, T., and Abebe, B.: Sulphide Remobilization, Deformation and Durchbewegung: The BMK deposit, Saskatchewan, Canada, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16375, https://doi.org/10.5194/egusphere-egu26-16375, 2026.
Distinguishing magmatic from hydrothermal processes in rare-metal granite systems is critical for understanding ore formation; however, zircons in these rocks are commonly affected by fluid-mediated modification, complicating the interpretation of both geochronological and geochemical signatures. We investigated zircon crystals from the Janchivlan rare-metal granite complex (Central Asian Orogenic Belt, Mongolia), a highly fractionated peraluminous system evolving from biotite-granite through graphic granite, amazonite-bearing to albite-lepidolite granite, with potential for Sn, W, Ta, and Li mineralization, as well as associated pegmatites. These lithologies record successive stages of magmatic differentiation and increasing fluid involvement.
Zircon U-Pb dating yields concordant ages of 290 ± 2.1 Ma for pegmatite and 195 ± 2.1 Ma for biotite-granite, indicating that the pegmatites formed from a different magmatic event. Zircon single-grain ages from biotite and lepidolite granites define a discordia with lower intercepts at 220 ± 2.1 Ma and 195 ± 2.1 Ma, respectively, interpreted as Pb loss during hydrothermal alteration. This interval overlaps with the apatite U-Pb age of 213 ± 3.7 Ma, supporting hydrothermal activity at this time.
Zircon REE patterns show a systematic evolution from biotite granite, characterized by (1) high ΣREE, moderate Eu/Eu* (~0.1–0.2), through graphic and amazonite granites with variable REE distributions and weak tetrad effects, to (2) lepidolite granite marked by LREE depletion, very low Eu/Eu* (<0.05), and pronounced tetrad effects. These trends document progressive melt fractionation accompanied by increasing melt-fluid interaction. Whole-rock geochemistry shows element-specific decoupling from zircon fertility: biotite-granite displays high Ta–W–Li–Rb concentrations, reflecting accumulation in biotite and accessory phases before fluid exsolution; amazonite granite records Sn and Pb enrichment during an intermediate fractionation window; and albite-lepidolite granite exhibits extreme Li and Rb enrichment but no corresponding enrichment of Ta, W, or Sn despite representing the most evolved stage. This pattern indicates that exsolution of fluids selectively redistributed fluid-compatible metals, while Li and Rb were mostly retained in late-crystallizing mica phases, producing distinct metallogenic stages within the granite system. These findings show that rare-metal mineralization in highly fractionated granites results from a multi-stage process where magmatic differentiation establishes initial metal budgets, but subsequent fluid exsolution and melt-fluid partitioning govern the ultimate distribution and concentration of specific ore metals.
How to cite: Ganbat, A., Genge, M., Chimidtseren, A., Webb, A. G., Cogné, N., Long, C. T., McKenzie, R., Sorger, D., and Mueller, T.: Tracing magmatic and hydrothermal processes in rare-metal granites using zircon geochemistry: the Janchivlan pluton, Central Mongolia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20133, https://doi.org/10.5194/egusphere-egu26-20133, 2026.
Rare earth elements (REE) are commonly enriched in alkaline magmatic systems and may be further redistributed by late-stage hydrothermal processes. This study focuses on REE-bearing mineralization in post-orogenic alkaline rocks and hydrothermal veins of the Amram Massif and Ramat Yotam volcanic complex, at the northernmost Arabian-Nubian Shield (Eilat area, southern Israel). These late Neoproterozoic (600-580 Ma) rocks record shallow emplacement of alkaline magmas followed by prolonged, possibly multi-stage, hydrothermal activity.
Fieldwork targeted late-stage silicic alkaline rocks, which often show intense alteration, and associated calcite, barite, and manganese-oxide veins. Whole-rock REE concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS) and mineralogical assemblages were defined using X-ray diffraction (XRD) and scanning electron microscopy combined with energy dispersive spectroscopy (SEM-EDS). Oxygen and hydrogen isotope ratios of calcite-hosted fluid-inclusions and oxygen and carbon isotope ratios of host vein calcite were measured using cavity ring-down spectroscopy (CRDS) and isotope-ratio mass spectrometry (IRMS).
Total REE concentrations in Amram alkaline rocks range from 100 to 700 ppm and are generally higher than those of other basement rocks in Israel (≤300 ppm). The LREE are enriched over HREE in all the magmatic rocks studied. Primary magmatic monazite is locally replaced by REE-F carbonates, recording remobilization of REE from phosphates into secondary phases during hydrothermal alteration.
Calcite veins provide an additional REE reservoir, with total REE ranging from 100 to 800 ppm, comparable to the host magmatic rocks, yet significantly higher than any other calcite veins recorded in Israel. Most calcite veins are LREE-enriched while some, from Amram Massif, are equally enriched in LREE and HREE. Stable isotope ratios of calcite and hosted fluid-inclusions indicate relatively high temperature (120-150°C) calcite precipitation from fluids of meteoric-origin, suggesting that REE were first concentrated in shallow alkaline magmas and subsequently redistributed into veins by later hydrothermal circulation in post-orogenic setting.
How to cite: Moller, U., Morag, N., Teutsch, N., Levy, E. J., and Katzir, Y.: Post-orogenic alteration and rare-earth elements mineralization in the northernmost Arabian-Nubian Shield (southern Israel), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20726, https://doi.org/10.5194/egusphere-egu26-20726, 2026.
With the accelerated upgrading of China's fluorine chemical industry, the gap in domestic fluorite resources is expected to widen in the future. Therefore, there is an urgent need to increase investment in the exploration of new fluorite mineral resources. Fluorite deposits occur either as independent vein-type fluorite-quartz orebodies or as associated or coexisting minerals in deposits of rare earth elements, barite, tungsten, tin, lead, zinc, iron, and other polymetallic ores. Accordingly, fluorite deposits can be classified into two types: independent vein-type fluorite deposits and associated/coexisting-type fluorite deposits. Currently, the fluorite resources developed and utilized in China mainly come from independent vein-type fluorite deposits.
Based on differences in the origin of metallogenic hydrothermal fluids and major ore-controlling factors, fluorite deposits in China can be categorized into two major groups: meso-epithermal deposits and magmatic hydrothermal deposits. Taking both genetic and industrial types into consideration, they can be further divided into three main categories: hydrothermal filling-type, sedimentary reworking-type, and associated/coexisting-type.
Hydrothermal filling-type deposits are the predominant type, mainly distributed in provinces such as Zhejiang, Fujian, and Jiangxi. The orebodies are controlled by fault zones, with their occurrence and morphology consistent with the fault zones. The main host rocks are Yanshanian magmatic rocks and pyroclastic rocks. The ore-forming materials primarily originate from magmatic hydrothermal fluids or heated groundwater. Sedimentary reworking-type deposits are mainly found in Inner Mongolia, Guizhou, Yunnan, and western Zhejiang. The fluorite orebodies exhibit a stratiform-like occurrence, consistent with the bedding of the strata, but are also disrupted and controlled by faults, resulting in significant variations in their occurrence and morphology. The ore-forming materials mainly derive from heated groundwater and thermal brines. Associated-type fluorite deposits are characterized by low fluorite grades but substantial resource volumes, allowing for comprehensive recovery and utilization. They are primarily distributed in regions such as Inner Mongolia, Hunan, and Yunnan. The ore-forming materials are mainly related to magmatic hydrothermal activities.
Hydrothermal filling-type vein-like independent fluorite deposits, controlled by fault structures, are currently the main type of fluorite deposits being mined in China. The formation ages of vein-type fluorite deposits in China are primarily the Yanshanian period, followed by the Variscan and Caledonian periods. Most vein-type fluorite deposits in China are closely genetically related to mid-to-late Yanshanian granites and volcanic rocks, with the typical characteristic of fluorite orebodies occurring in intermediate-acid magmatic rocks and their surrounding host strata.
How to cite: Cao, H.-W., Chen, H.-R., and Zou, H.: Characteristics of Major Types of Fluorite Deposits in China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2134, https://doi.org/10.5194/egusphere-egu26-2134, 2026.
The formation of hydrothermal deposits of strategic metals such as gold and uranium involves complex, multi-stage processes coupling fluid–rock interaction, structural dynamics, and chemical evolution across scales. This study integrates structural and micro-textural analysis with multi-scale chemical kinetic investigations to elucidate the dynamics of element enrichment and ore formation. We focus on bridging the dynamic linkages between micro- to nano-scale textures and the larger-scale chemical evolutionary processes in complex natural systems, aiming to decode the kinetic mechanisms governing element migration and mineralization. Modern analytical approaches, including machine learning–assisted data interpretation, are explored for their potential to resolve the spatio-temporal evolution of mineralization.
Using representative hydrothermal gold deposits from the Jiaodong region and uranium deposits from the Bashibulake district (Xinjiang) in China as case studies, we investigate the micro-textures and in-situ trace element and oxygen isotopic compositions of hydrothermal quartz. Cathodoluminescence (CL) zoning and cross-cutting relationships reveal multiple generations of quartz, corresponding to discrete fluid infiltration events. The CL intensity correlates positively with Al content but not with δ18O, indicating differing controls on trace element incorporation versus isotopic fractionation. Elevated trace elements (e.g., Al) in quartz are attributed to intensified fluid–rock interaction, which mobilized lithophile elements. Seismically induced fluid fluctuations are shown to enhance compositional variability in quartz by affecting fluid chemistry and pH.
Oxygen isotope analyses of successive quartz generations yield distinct δ18O ranges. Calculated fluid δ18O values evolve from mantle-like signatures (≥7‰) in early stages toward progressively lower values, reflecting increasing meteoric water input in later stages. Water–rock reaction is identified as a key process modifying fluid O isotopic composition. Remarkably, mineral-scale near-constant δ18O values suggest effective isotopic buffering by the host rock despite episodic fluid fluctuations.
Our results demonstrate that micro-textural and geochemical signatures in quartz serve as effective tracers for quantifying water–rock interaction intensity and fluid fluctuation history. The study highlights the value of combining micro-analytical techniques (e.g., LA-ICP-MS, SIMS) with macro-structural analysis and emerging data-science methods to unravel the kinetic pathways of strategic metal mineralization in hydrothermal U-Au systems.
Keywords: Quartz geochemistry; Strategic metal deposits; Fluid–rock interaction; Multi-scale chemical kinetics
How to cite: Song, H., Li, Q., Qiu, K.-F., Xu, Z., Yu, H., and Deng, J.: Micro-textural and geochemical constraints on fluid–rock interaction and fluid fluctuation in hydrothermal strategic metal mineralization systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22630, https://doi.org/10.5194/egusphere-egu26-22630, 2026.
Posters virtual: Thu, 7 May, 14:00–18:00 | vPoster spot 3
EGU26-2923 | ECS | Posters virtual | VPS25
Structure-controlled Uranium + REE mineralization in low temperature basinal brine hydrothermal system at the contact of Kaladgi Basin and Peninsular Gneissic Complex, South IndiaThu, 07 May, 14:45–14:48 (CEST) vPoster spot 3
The Kaladgi Basin, an E–W trending intracratonic basin in the northern part of the Dharwar Craton, preserves favourable structural and stratigraphic conditions for sandstone-hosted and unconformity-related U–REE mineralization. In the study area, the Neoproterozoic Cave Temple Arenite (CTA) of the Badami Group unconformably overlies deformed Mesoproterozoic rocks of the Bagalkot Group. The crystalline basement of the Kaladgi Supergroup comprises Meso- to Neoarchaean Peninsular Gneiss and the Chitradurga Greenstone Belt. This association of cratonic basement, schist belt, and basin-margin fault and fold systems provides an excellent structural framework for hydrothermal fluid circulation and mineralization.
Detailed thematic mapping at 1:25,000 scale in the Ramdurg–Suriban sector reveals that NNW–SSE–oriented Dharwarian stress generated a series of anticlines and synclines involving the Saundatti Quartzite, Malaprabha Phyllite, and Yaragatti Argillite, as constrained by conjugate fracture analysis and S–C fabric development. An E–W trending tectonic fault defines the contact between the Peninsular Gneissic Complex and Saundatti Quartzite, with comparable faulted contacts also developed within the Bagalkot Group. Intense faulting resulted in silicification, chalcedonic brecciation, and pervasive hydrothermal alteration along these contact zones. Transverse normal faults with associated brecciation accommodate strain related to the main E–W structure and indicate episodic reactivation of the basin architecture.
Fusion ICP–MS analysis of 20 bedrock samples collected proximal to these fault zones shows U238 concentrations exceeding twice the threshold values of National Geochemical Mapping (NGCM) stream sediment sample. Uranium enrichment is spatially associated with Malaprabha Phyllite, first-cycle CTA, and silicified banded hematite quartzite veins of the Hiriyur Formation. Chondrite-normalized (La/Yb)n versus (Eu/Eu*)n systematics indicates a dominantly low-temperature basinal brine hydrothermal system characterized by low (La/Yb)n <25 and negative Eu anomalies. Redox-sensitive (Ce/Ce*)n versus (Eu/Eu*)n plots further indicate reducing fluid conditions. In contrast, quartz–chlorite veins developed within sheared Malaprabha Phyllite and younger dolerite record comparatively higher-temperature fluids, marked by Eu2+ mobilization ((Eu/Eu*)n > 0.8) and negative Ce anomalies. These results suggest that reactivated, structure-controlled tectonites acted as effective fluid pathways, with the TTG-dominated Peninsular Gneissic Complex serving as a likely uranium source and contributing to localized U–REE mineralization along the basin margin.
How to cite: Mahanandia, A., Lal, M. M., Singh, T. G., Nandhagopal, N., and Singh, S.: Structure-controlled Uranium + REE mineralization in low temperature basinal brine hydrothermal system at the contact of Kaladgi Basin and Peninsular Gneissic Complex, South India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2923, https://doi.org/10.5194/egusphere-egu26-2923, 2026.
EGU26-13014 | ECS | Posters virtual | VPS25
Epigenetic Cu-Zn Mineralization in the Yığılca Formation Tuffs of Kuzuluk (Sakarya), Western Pontides, Turkey: Insights from Sulfur Isotope Analysis and Hydrothermal ProcessesThu, 07 May, 14:48–14:51 (CEST) vPoster spot 3
The Cu-Zn mineralization in the Kuzuluk (Sakarya) region has hosted within the tuffaceous rocks of the Eocene Yığılca formation along the fault zones in the Western Pontides. The study area is made up of the Permian-Triassic Sultaniye Metamorphites, Upper Cretaceous Abant formation, Early-Middle Eocene Çaycuma and Yığılca formations, and Pliocene Örencik formation. It is characterized by significant tectonic activity represented by dip-slip fault zones, particularly within the tuffaceous rocks of the Yığılca formation. The ore zone occurred within the fracture zone in the tuffaceous rocks of the Yığılca formation represented by an epigenetic mineralized vein-type structure including pyrite, chalcopyrite, sphalerite, bornite, quartz, and calcite. The geochemical studies indicated that this ore zone contains approximately 2620 ppm Cu and 1440 ppm Zn concentrated within the fracture zone. Carbonatization is the main hydrothermal alteration in the study area. To assess the sulfur origin in the mineralization, ten sulfide samples from pyrite and chalcopyrite minerals were analyzed for sulfur isotopes. Their δ34S data vary from +28.56 to +29.52 ‰, which shows that the enrichment is due to the vigorous interaction between hydrothermal fluids and sedimentary sulfate reserves. Additionally, this reflects the impact of hydrothermal fluid and organic matter dissolution in the area, in contrast to magmatic sulfur sources. Therefore, circulation of the hydrothermal fluids along fault zones played a crucial role in the formation of the ore zone, facilitating the precipitation of Cu-Zn minerals and gangue minerals (quartz and calcite). These findings suggest that the geological processes that lead to the formation of the Cu-Zn Kuzuluk mineralization contribute to clarifying hydrothermal mineralization within Western Pontides fault zones.
How to cite: Yalçın, C. and Kaya, M.: Epigenetic Cu-Zn Mineralization in the Yığılca Formation Tuffs of Kuzuluk (Sakarya), Western Pontides, Turkey: Insights from Sulfur Isotope Analysis and Hydrothermal Processes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13014, https://doi.org/10.5194/egusphere-egu26-13014, 2026.
