Sulfide Deposits Research Articles

Characterisation of Five Natural Magnetite Reference Materials for In Situ Iron Isotope Measurement with Application to Magmatic Ni‐Cu Sulfide Mineralisation

Iron isotope ratios in magnetite have been widely used to reveal critical geological and biological processes. Laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (LA‐MC‐ICP‐MS) is ideally suited for measurement of Fe isotope ratios, however the lack of suitable reference materials poses a significant challenge for in situ Fe isotopic measurements in magnetites. In this study, five high‐quality natural magnetite crystals were characterised for Fe isotope ratios using solution nebulisation (SN)‐MC‐ICP‐MS and LA‐MC‐ICP‐MS. The effects of LA‐MC‐ICP‐MS analytical conditions were investigated to obtain precise and accurate Fe isotope ratios. The yielded intermediate measurement precisions for the δ56Fe values in the five investigated magnetites were ± 0.05–0.06‰ (2s) using SN‐MC‐ICP‐MS and ± 0.08–0.14‰ (2s) using LA‐MC‐ICP‐MS. Magnetites with homogeneous Fe isotopic compositions in hand‐specimen measurements and microanalysis can serve as potential reference materials for in situ Fe isotopic measurement. Furthermore, the Fe isotope ratios in the magnetites from the Jinchuan Ni‐Cu‐PGE sulfide deposit were measured using LA‐MC‐ICP‐MS with natural magnetite as the bracketing calibrator. The increase in the Fe isotopic composition with magmatic sulfide evolution was primarily dominated by oxygen fugacity (fO2) and hydrothermal fluids. This finding implies that the Fe isotopic composition of magnetite can serve as a potential geochemical indicator of magmatic Ni‐Cu sulfide mineralisation.

Ore sulfur of Golovnin Volcano, Kunashir Island

Research subject. Hydrothermal deposits of Golovnin Caldera. Aim. To study the epithermal volcanogenic ore formation. Key points. Until now, there has been a consensus on the exogenous sedimentary (colloidal) genesis of sulfur in volcanic lakes. Our observations and microstructure studies indicate the presence of sulfur melt at the bottom of Kipyaschee Lake. Drops of this melt are carried to the surface of the lake as part of a light gray foam. The significant differences of sulfur spherules in the concentration of sulfide mineralization, in its composition, as well as in the presence or absence of numerous opal inclusions are most simply explained by the capture of droplets in various parts of the sulfur melt and their subsequent movement by a gas stream passing through the melt. Elemental sulfur condensate is formed in bottom sediments as a result of forced cooling of endogenous gas flows by lake water. The main condensation of sulfur occurs here (96% or more of the total potential of fluid sulfur). Residual condensation of sulfur occurs in the aquatic environment. Finely dispersed sulfur condensate in a mixture with water is unstable and breaks down over time with the release of hydrogen sulfide and the formation of sulfurous and sulfuric acids. The activity of bottom hydrotherms and coastal unrest prevents the formation of colloidal sulfur sediment at the bottom of lakes. In the crater depressions at the bottom of the lakes of the Golovnin Caldera, sulfidization of its melt occurs simultaneously with the condensation of sulfur itself. Gravitational deposition of sulfides in the sulfur melt leads to their enrichment of the root parts of crater depressions, where pyrite ore bodies are formed in real time. Terrestrial sulfur deposits, together with the modified rocks overlying them, demonstrate the full profile of endogenous apical oxidation under gas-hydrothermal action: sulfur and sulfur-opal rocks up the section are replaced by gypsum-jarosite rocks and, further, by an “iron hat” of limonite-cemented breccias of the dome mantle. Conclusions. Observations, microstructure studies and molecular chemical modeling indicate the endogenous condensate origin of ore sulfur in the Golovnin Caldera and exclude its exogenous sedimentary genesis.

Evolution of volcanism and geodynamic settings in the Sakmara zone of the Southern Urals in the early Paleozoic

Research subject. Northern part of the Sakmara zone of the Southern Urals, represented by the Krakinsko-Mednogorsk paleovolcanic belt, including the Mednogorsk ore district and the Blavinsko-Komsomolskoye ore field. Aim. To reconstruct the paleogeodynamic settings during the Cambrian–Early Devonian in the Sakmara zone. Methods. An analysis of geological, petrogeochemical, structural-tectonical, and paleovolcanological data obtained by the authors and those reported in literature using conventional and new petrogeochemical diagrams. Results. The following stages of tectono-magmatic evolution in the Sakmara zone were distinguished: (1) Cambrian–Early Ordovician, continental rifting; (2) Early–Middle Ordovician, oceanic spreading; (3) Early Silurian, suboceanic rifting, serpentinite protrusions, edaphogenic breccias, siliceous rocks (starting a subduction zone); (4) Late Silurian–Early Devonian, island-arc basalt-rhyolite volcanism and sulfide deposits, volcanism of the shoshonitic and alkaline series, formation of the rear island arc. The Sakmara zone features no analogues of boninite volcanism (D1e2) typical of the West Magnitogorsk zone, which indicates the absence of signs of the volcanogenic strata of the Voznesensk–Prisakmar zone being pushed into the Sakmara structural zone. Conclusions. (1) In the Cambrian–Early Devonian, volcanogenic and volcanogenic-sedimentary formations and strata of the Sakmara zone formed a megacycle, starting with the processes of continental and oceanic rifting, which led to the subduction process and generation of the frontal and rear island arcs. (2) The volcanism in the Sakmara and Voznesensk–Prisakmar zones developed autonomously, without tectonic transfers from east to west. (3) The partial coincidence of the formation age of the Chanchar (D1lh–e1) complex of the Sakmara zone and the Turin complex (S2p–D1lh) of the Tagil zone suggests the presence of a reduced continuation of the western wing of the Tagil zone in the Sakmara zone.

The cobalt and nickel enrichment in base metal sulfides from the Xiarihamu Cu-Ni-Co deposit, China: Constrained by in-situ mineral geochemistry of sulfides

Rapidly growing demand for cobalt and nickel in rechargeable battery industry promotes research on metallogenic theory of magmatic Cu-Ni-Co sulfide deposits. Xiarihamu Cu-Ni-Co deposit, one of the lately discovered Co-rich magmatic sulfide deposits in China, is typical of distribution in orogenic belts, rather than in divergent tectonic settings as many deposits of the same type. In-situ elemental and sulfur isotopic analyses of base metal sulfides (BMS; pyrrhotite, pentlandite, and chalcopyrite) from Xiarihamu were conducted in this study. The strongly negative correlation between Fe and Co + Ni reveals the major occurrence of Co and Ni as isomorphism states in pentlandite and pyrrhotite. The δ34S values of pentlandite and pyrrhotite generally increase with Co contents and Co/Ni ratios, indicating that the Co enrichment within BMS accompanied with enhanced contamination of crustal sulfur. Zinc, Cd, Sb, and Te are significantly and preferentially fractionated into intermediate sulfide solution (ISS) from which chalcopyrite exsolved. The Se contents and Se/S ratios of pentlandite and pyrrhotite in lherzolite/harzburgite are much higher than those of BMS from gabbro, which has systematically higher δ34S values. Combined with the partially overlapped Sb/Se and As/Se ratios of BMS from lherzolite and gabbro, as well as similar calculated R factors of ore-hosting peridotite and gabbro, it is proposed that the studied Xiarihamu gabbro was crystallized from a separate pulse of Co-Ni-enriched, Se-depleted and intensively contaminated mafic parent magma, rather than evolved from ultramafic magma through crystallization fractionation. The lack of olivine and spinel in gabbro also promoted more Co and Ni into sulfide liquid. Based on Se/Te ratios, the pentlandite and pyrrhotite from drill core XH1E01S was originated from sulfide liquid, which suffered higher degree of crystallization fractionation of monosulfide solution (MSS). While pentlandite and pyrrhotite that crystallized from less evolved parent sulfide liquid bear less cobalt, such as those collected from drill core XH1109. This study strengthens the potential importance of crustal contamination and crystallization fractionation of MSS from sulfide liquid during Co enrichment within BMS (pentlandite and pyrrhotite).

Genesis of the Mamuniyeh copper deposit in the central Urumieh-Dokhtar Magmatic Arc, Iran: Constraints from geology, geochemistry, fluid inclusions, and H–O–S isotopes

The Mamuniyeh Cu deposit is located in the central part of the Urumieh-Dokhtar Magmatic Arc (UDMA), 10 km south of the city of Mamuniyeh, Iran. Mineralization is controlled by faults with a NW-SE trend and hosted within an Eocene volcanic sequence and Oligo-Miocene hypabyssal calc-alkaline monzonitic and gabbroic bodies. Quartz + chalcopyrite veins are most abundant and high-grade ore containing up to 5 wt% Cu, although quartz + pyrite veins have the most abundant sulphide content. In addition, quartz + chalcopyrite + specular hematite ± pyrite veins/veinlets are another common mineralized assemblage in the Mamuniyeh copper deposit, with pyrite, chalcopyrite, bornite, and oxide minerals (specular hematite, titanomagnetite, and magnetite) typical of the hypogene stage. Chalcocite, covellite, and dignite also formed at the margins of primary sulphides in the supergene (paleoweathering) stage. The mineralized veins exhibit colloform, crustiform, open space-fillings, replacements, and dissemination textural characteristics associated with mineralizing assemblages with silicification, argillization, chloritization, and sericitization assemblages. The salinity for L > V fluid inclusions is between 1.74 to 11.7 wt% NaCl and for (V > L) inclusions between 1.7 to 11.4 wt% NaCl. The average homogenization temperature and salinity for quartz + chalcopyrite + pyrite veins is 186 °C and 4.9 wt% NaCl. In the quartz + chalcopyrite assemblage an average of 185 °C and 4.5 wt% NaCl and for quartz + chalcopyrite + specularite ± pyrite (QCSP) an average of 195 °C and 5.59 wt% NaCl was determined. In these three vein types, the fluid density has almost identical values ranging from 0.8 to 1.0 g/cm3. The mineralizing system evolved in two-stages; the first metal precipitation occurred at less than 1 km of crustal depths and second metal deposition stage at shallower crustal levels (less than 500 m). Although it appears that the boiling process occurred within the fluids of the area, the primary factor contributing to Cu mineralization was influenced by fluidmixing processes. The δ18O and δD values of ore fluids computed vary from + 6.08 to −0.50 ‰ and −92 to −71 ‰, respectively, indicative of the blending of oxidizing and cooler meteoric waters with primary magmatic fluids. Calculated values of δ34S of H2S in equilibrium with chalcopyrite ranges from −7.6 to −1.9 ‰ and H2S in equilibrium with pyrite ranges from −7.1 to −3.8 ‰, respectively; this is consistent with monzodiorite to gabbro as the magmatic sulphur source for copper mineralizing fluids. Furthermore, the QCSP vein data align more closely with primary magmatic water compared to other veins, suggesting that precipitation occurred mainly from magmatic fluids, which experienced depletion in δ18O due to mixing with meteoric waters (shallow oxygenated ground waters), which caused sulphide deposition. The geochemical features for these magmas show that contamination with crustal materials occurred during the ascent of the parent magma, as well as the role of suprasubduction fluids released from the subducting plate in mantle metasomatism. Based on all evidence, Cu mineralization in the Mamuniyeh deposit has been categorized as a low-sulphidation epithermal-type system, which formed during active magmatism in the central part of UDMA.

Impact of temperature on sphalerite chemistry: Simulation experiments of sphalerite in MVT Zn-Pb sulfide deposits in the Beiba Dome, northern Sichuan Basin, China

Many sedimentary metal deposits are rich in organic matter, and some organic deposits are metal deposits themselves. These metal deposits, represented by MVT Zn-Pb deposits, are widely distributed in the world, and their industrial types (Pb + Zn > 5 %) are also very rich, which has important theoretical and economic significance. However, there is no systematic research on the metallogenic mechanism of MVT Zn-Pb deposits in the participating organic matter. Therefore, geochemical simulation experiments and thermodynamic calculations have been used to examine the role of organic matter in reconstructing the ore-forming process of MVT Zn-Pb sulfide deposits. Additionally, the precipitation chemistry of sphalerite under the mineralization process mediated by organic matter is explained. Guided by the evidence on the homogenization temperature of fluid inclusion, the temperature range, from 60 °C to 200 °C, has drawn a close relationship between the temperature and the ore-forming mechanism. Notably, this reflects sphalerite’s chemical composition and morphology, even assisting in interpreting its chemical formation. The results showed that 80 °C is the beginning temperature for ZnS formation calculated from the inductively coupled plasma mass spectrometry analysis (ICP-MS) under the precipitation simulation experiments with the participation of organic matter. With the increased temperature, the rate of ZnS formation showed a trend of rapid growth in the early stage (80–140 °C) and relatively slow in the later stage (160–200 °C). This finding suggests a closer coupling relationship between metal mineralization and the maturation-genesis of organic matter, mainly the formation of the ancient oil reservoir. Following the continued increase in temperature, the morphology of ZnS was significantly different from that of the scanning electron microscope (SEM), with an apparent fine granular structure at high temperature. Likewise, more ZnO was also found through the X-ray photoelectron spectroscopy analysis (XPS), reducing the purity of the ZnS in sphalerite. Thus, this study helps reveal the metallogenic mechanism of MVT Zn-Pb sulfide deposits from the viewpoint of sphalerite chemistry under the participation of organic matter from temperature change. Furthermore, it provides a valuable theoretical and experimental basis for the later prospecting of the metal deposits.

Trace element and isotope composition of calcite, apatite, and zircon associated with magmatic sulfide globules

AbstractThe formation of volatile-rich phases in magmatic sulfide systems has been interpreted at least in six different ways. The most popular model attributes their origin to secondary processes, mostly due to the presence of serpentine, chlorite, phlogopite, amphibole, and calcite. While chlorite and serpentine are likely to form as alteration products, the other volatile-rich minerals have the potential to originate in a range of ways, including by primary magmatic processes. Based on mineralogical and petrological studies, it was recently suggested that volatile- and incompatible element-rich halos around sulfide globules may form due to the interaction between three immiscible liquids: silicate, carbonate, and sulfide. This hypothesis was confirmed by experimental data revealing the systematic envelopment of sulfide globules by carbonate melt, indicating their mutual affinity. In this study, we present data on isotopic signatures and trace element distributions of three minerals commonly found in spatial association with sulfides—calcite, apatite, and zircon—to address the question of the source and nature of volatiles and other incompatible elements involved in the formation of the halos. Here we compare our new hypothesis with all the previously proposed explanations to show if they can be consistent with obtained results. Our findings indicate that both mantle and crustal sources play a role in the formation of volatile- and incompatible element-rich halos, strongly correlating with sulfur isotope data previously reported for the sulfide globules in the same intrusions. This correlation confirms the shared origin of sulfides, carbonate and fluids during ore-forming processes, ruling out the secondary origin of volatile-rich phases. The isotope and trace element signatures support the newly proposed hypothesis that volatile- and incompatible element-rich halos could have been formed due to the interaction of immiscible sulfide, carbonate, and silicate melts. The volatile-rich carbonate melt could be sourced from the mantle or it could be added from the crust. Regardless of the origin, carbonate melt and sulfide liquid both immiscible with mafic magma tend to stick to each other resulting in the formation of volatile- and incompatible element-rich halos commonly documented in magmatic sulfide deposits.

Enhancing Mineral Exploration Programs Through Quantitative XRD: A Case Study from the Gumsberg Polymetallic Sulphide Deposits, Sweden

As challenges in precious and base metal exploration intensify due to the diminishing availability of high-grade ore deposits, rising demand, energy costs, and stricter regulations towards net-zero carbon activities, advanced techniques to enhance exploration efficiency are becoming increasingly critical. This study demonstrates the effectiveness of quantitative X-ray diffraction (QXRD) with Rietveld refinement, coupled with multivariate statistical analysis (including agglomerative hierarchical clustering, principal component analysis, and fuzzy analysis), in characterizing the complex mineralogy of strata-bound volcanic-associated limestone-skarn Zn-Pb-Ag-(Cu-Au)-type sulphide deposits (SVALS). Focusing on 113 coarse rejects from the Gumsberg project located in the Bergslagen mining district in central Sweden, the research identified five distinct mineralogical clusters corresponding to polymetallic base metal sulphide mineralization, its proximal alteration zones, and variably metamorphosed host rocks. The results reveal significant sulphide mineralization, ranging from disseminated to massive occurrences of sphalerite, pyrrhotite, pyrite, and galena, with trace amounts of secondary minerals like anglesite in certain samples indicating weathering processes. The study also identifies rare minerals such as armenite, often overlooked in traditional geological logging. These findings underscore the potential of QXRD to enhance resource estimation, optimize exploration strategies, and contribute to more efficient and sustainable mineral exploration programs. The accuracy of QXRD was cross-validated with geological logs and geochemical data, confirming its reliability as a mineralogical discrimination tool.

Subsurface Faults and Magma Controls on the Jinchuan Ni-Cu Sulfide Deposit: Constraints from Magnetotelluric Data

The Jinchuan Ni-Cu sulfide deposit in the Longshoushan terrane is among the world’s largest magmatic sulfide deposits. This study uses magnetotelluric (MT) survey data imaging combined with previous geophysical data to investigate Segment III of the deposit. The image of MT data reveals a significant low-resistivity anomaly ~200 m beneath Segment III, aligning with known ore bodies, and an additional anomaly to the north, indicating further exploration potential. These findings highlight the deep-seated intrusions and their connection to surface mineralization, emphasizing the critical role of ultramafic rock encapsulation and fault-controlled morphology in ore body formation. The newly identified northern anomaly, resembling the Segment III ore bodies, suggests a promising target for future exploration. Integrating MT surveys with other geophysical methods enhances the understanding of subsurface structures and mineralization, providing a robust framework for discovering concealed mineral deposits and improving exploration efficiency.

Implementing Antimony Supply and Sustainability Measures via Extraction as a By-Product in Skarn Deposits: The Case of the Chalkidiki Pb-Zn-Au Mines

Antimony is one of the world’s scarcest metals and is listed as a Critical Raw Material (CRM) for the European Union. To meet the increasing demand for metals in a sustainable way, one of the strategies that could be implemented would be the recovery of metals as by-products. This would decrease the amount of hazardous materials filling mining dumps. The present study investigates the potential for producing antimony as a by-product at the Olympias separation plant in Northern Greece. This plant works a skarn mineralization that shows interesting amounts of Sb. Boulangerite (Pb5Sb4S11) reports on Pb concentrate levels reached 8% in the analyzed product. This pre-enrichment is favorable in terms of boulangerite recovery since it can be separated from galena through froth flotation. Boulangerite distribution in the primary ore is quite heterogeneous in terms of the inclusion relationships and grain size. However, a qualitative assessment shows that the current Pb concentrate grain size is too coarse to successfully liberate a good amount of boulangerite. The use of image analysis and textural assessments is pivotal in determining shape factors and crystal size, which is essential for the targeting of flotation parameters during separation. The extraction of antimony as a by-product is possible through a two-step process; namely, (i) the preliminary concentration of boulangerite, followed by (ii) the hydrometallurgical extraction of the antimony from the boulangerite concentrate. The Olympias enrichment plant could therefore set a positive example by promoting the benefits of targeted Sb extraction as a by-product within similar sulfide deposits within the European territory.

Hidden deep sulfide cumulates beneath the Jinchuan Ni−Cu−platinum-group element deposit (China) inferred from Ni−Cu isotopes

The mechanisms that concentrated metals in the world’s single largest nickel−copper−platinum-group element (Ni−Cu−PGE) sulfide deposit, the Jinchuan deposit in northwestern China, remain enigmatic. Nickel and Cu isotopes are novel isotopic systems that may fill this knowledge gap as they are major constituents of sulfide melt, the main carrier of economically important metals. Sulfide ores in the Jinchuan deposit are characterized by systematically high δ60/58Ni and δ65Cu values, which are positively correlated (r2 = 0.84), and show well-defined correlations with PGEs, S, Ni, and Cu contents, and Ni/Pd, Cu/Pd, and Pd/Ir ratios. The isotopic signatures can be best explained by the early segregation of sulfide melt at depth prior to ascent of the parental magmas, storing isotopically light Ni and Cu in deep magma chambers. Subsequent sulfide melt segregation and fractionation in shallow portions of the magmatic conduit generated the currently explored sulfide ores, with heavy and positively correlated Ni−Cu isotopic signatures. Therefore, hidden deep orebodies are promising targets for further exploration beneath the Jinchuan deposit.

Relative timing and controls on advanced argillic and conventional alteration of the Neoarchean Onaman volcanogenic massive sulfide deposit, Ontario, Canada

Relative timing and controls on advanced argillic and conventional alteration of the Neoarchean Onaman volcanogenic massive sulfide deposit, Ontario, Canada

Three-dimensional airborne electromagnetic forward modeling based on multiscale hexahedral finite-element method

Slow forward modeling is the main factor that restricts the practical use of three-dimensional (3D) inversion and interpretation of airborne electromagnetic (AEM) data. To improve the modeling efficiency in 3D AEM, we propose a new multiscale finite-element (MsFE) method based on unstructured hexahedral meshes. Compared with the traditional 3D AEM forward modeling, the main advantage of our newly developed method is that it can simulate complex underground structures in the earth quickly. Since we can fit the earth's topography or the anomalous bodies underground using a small number of hexahedral grids, we can quickly model them using MsFE. The main idea of the MsFE forward modeling method is to construct an interpolation operator between a coarse and a dense mesh and use the interpolation operator to map the conventional FE coefficient matrix to the MsFE coefficient matrix and thus reduce the number of unknowns in the modeling process. This will vastly reduce the scale of the linear equations system. We validate our method by simulating a typical mountain peak model and demonstrate its effectiveness by simulating numerous synthetic models and a model from Voisey Bay's Ovoid sulfide deposit, Canada.

Structural characteristics and biological evaluation of copper coating cotton material obtained by chemical reduction method

The article describes the preparation of new cotton materials obtained by chemical deposition of copper sulfide. This two-stage process consists of chelation of copper sulfate on cellulose chains of cotton (COT → COT-CuSO4) with subsequent precipitation of copper in the form of copper sulfide (COT-CuSO4 → COT-CuS) using sodium sulfide. The obtained COT-CuS composites were characterized physicobiologically. Thus, the structural characteristic of the Cotton-CuS material was determined by microscopy analysis (SEM), Atomic Absorption Spectrometry with Flame Excitation (FAAS), specific surface area and total pore volume analysis (BET). The copper functionalized cotton fabric was subjected to microbial activity tests against colonies of Gram-negative (Escherichia coli) and Gram-positive ( Staphylococcus aureus) bacteria and Chaetomium globosum, Aspergillus niger fungal molds species. Biochemical evaluation includes hematological tests of activated partial thromboplastin time (aPTT) and prothrombin time (PT). The substantial antimicrobial properties of the newly synthesized COT-CuS material with the lack of influence on blood coagulation processes offer prospects of a potential use as applications as an antibacterial/antifungal material.

Petrogenesis and tectonic evolution of mineralized mafic intrusions in the Eastern Desert of Egypt: Implications for gold–sulfide genesis

The whole–rock chemistry, mineral chemistry, and remote sensing data of the Atud–UmKhasila Neoproterozoic mafic intrusions in the Eastern Desert of Egypt show two different mafic plutons: (1) the metagabbro–diorite complex; and (2) the G. Atud gabbros. Both of these contain two types of Cu–Ni–Fe–sulfide mineralizations. Multispectral remotely sensed images of Landsat 8 OLI/TIRS, Sentinel 2–B, and ASTER1T were used to give an overview of hydrothermal alteration signatures and distinguish different lithological units. The G. Atud gabbros are intruded into the metagabbro–diorite complex and consist mainly of olivine gabbros, while the metagabbro–diorite complex comprises metagabbros, diorites, and quartz diorites. They were formed under high fO2 (ΔFMQ= +1.43 to + 0.33) with a higher crystallization temperature (∼ 900–1100 °C) and pressure (∼ 6.0 kbar on average) at 18 km depth relative to associated metagabbros. Like magmatic sulfides in mafic intrusions, the G. Atud gabbros contain disseminated grains of pyrrhotite, pentlandite, chalcopyrite, and pyrite, up to 5 vol%. On the other hand, sulfide deposits (up to 30 vol%) such as pyrite, As–bearing pyrite, arsenopyrite, and gold with minor sphalerite and galena at the Atud gold mine, are related to the metagabbro–diorite intrusion. They are found as disseminations, patches, microveinlets, and bands. The sulfide deposits and economic gold are spatially concentrated in smoky quartz veins (up to 25 g/t) and metasomatic alteration zones, i.e., silicification and hematization of metagabbros (0.32 g/t), phyllic, argillic, and propylitic alteration, and carbonate–silicified zones, along gabbroic intrusive contacts, which all follow the Najd NW–SE shear zone. They are possibly of hydrothermal origin (epigenetic). They are also precipitated by mineralized fluids (rich in Si, K, Fe, Pb, Ag, Au, As, S, Ni, Zn, Cu, CO2, and H2O) that have been derived from a mixed magmatic–metamorphic source. The high Au contents with As–bearing pyrite and arsenopyrite in both Fe–rich and smoky quartz veins are related to the interaction between Fe from metagabbro–diorites and the Au(HS)-2 compound as well as the crystallization of pyrite, which reduced the sulfur contents in the mineralized fluids and hence led to gold precipitation. The late intrusion of G. Atud gabbros into metagabbro–diorite rocks enhanced the circulation of sulfide-gold-bearing hydrothermal fluids towards the contacts of the latter ones. These fluids along the shear zones cause metasomatic alteration in addition to leaching and the collection of sulfides and gold in the metagabbros. The protoliths of metagabbro–diorite rocks have a calc–alkaline nature and were formed in a volcanic arc setting, while the G. Atud gabbros were crystallized from Mg-rich tholeiitic melts in the extensional rift (e.g., rifted arc) setting as a result of asthenospheric upwelling due to the slab detachment and/or lithospheric delamination. The Atud gold–sulfide mineralization was related to the thermal uplifting–extensional tectonism. The enrichment of the G. Atud gabbros in LILE, alongside LREE over HFSE, reflects their derivation from a metasomatized mantle source during a rifted arc following the subduction processes.

Formation of the Lianhuashan Cu deposit in the southern Great Xing’an Range, NE China: Constraints from fluid inclusions, whole-rock geochemistry, zircon U–Pb geochronology, and H–O–S–Pb isotopes

The medium-sized Lianhuashan Cu sulfide deposit is located in the southern Xing’an Range of Inner Mongolia, NE China. The zoned massive sulfide vein ores are hosted mainly in the Permian Dashizhai Formation, and the ore veins are controlled by NW–NNW-trending structures. The ore-forming process comprises four stages: arsenopyrite–quartz (I); chalcopyrite–pyrite–quartz (II); pyrite–chalcopyrite–sphalerite–galena–quartz (III); and ore-barren sulfide–quartz–carbonate (IV). Three types of fluid inclusions (FIs), namely vapor-rich two-phase (LV-type), liquid-rich two-phase (VL-type), and daughter mineral-bearing three-phase (SL-type), are distinguished. Stage I, II and III contain all types of FIs (LV-, VL-, and SL-type), with homogenization temperatures (Th) of 268–462°C, 230–382°C and 180–340°C and salinities of 3.4–52.3, 3.4–44.5 and 3.7–39.9 wt% NaCl eqv., respectively, whereas stage IV has only VL-type FIs, with Th = 152–232°C and salinity = 3.4–7.9 wt%. Fluid geochemical data show that the Lianhuashan ore fluids were of medium–high temperature (236–382 °C), high-salinity (31.5–44.5 wt%), and relatively oxidizing conditions, typical of a NaCl-H2O system. The microthermometric and H–O isotope data (δ18OH2O = − 9.0 to 6.1 ‰; δD = − 149.0 to − 99.0 ‰) indicate that the ore fluids were initially magmatic with later meteoric water incursion. The sulfide S (δ34S = − 2.9–3.8 ‰) and Pb (206Pb/204Pb = 17.954 − 18.492, 207Pb/204Pb = 15.427 − 15.739, 208Pb/ 204Pb = 37.815 − 38.357) isotopes support that the metals were magmatic-derived. Fluid boiling, cooling, and meteoric water mixing were likely the main ore precipitation mechanism at Lianhuashan.We suggest that Cu minerals at Lianhuashan were precipitated with boiling at ∼ 1km depth. For the ore-forming granodiorite porphyry (zircon U-Pb age: 252.8 ± 1.8 Ma), geochemical data indicate that the primary magma was formed by partial melting of the thickened or delaminated lower crust. Integrating the available age, geological, and geochemical evidence, we suggest that mineralization at Lianhuashan is spatial–temporal and genetically associated with the granodiorite porphyry, and was formed in a volcanic arc setting after the Paleo-Asian Ocean closure.

Multi-stage magma emplacement in the western end of the Jinchuan Ni[sbnd]Cu sulfide deposit, NW China, and mineral exploration strategy based on exploration data

The western intrusion of the world-class Jinchuan NiCu sulfide deposit consists of fine-grained and coarse-grained binary lithofacies units. However, recent exploration has revealed two layers of net-textured sulfides in the fine-grained unit at the western end of the Jinchuan intrusion, adding complexity to the genesis of sulfide mineralization. We measured chalcophile elements and collected exploration data on Cu and Ni content to investigate their genesis and prospecting potential. The lower fine-grained subunits, comprising a layer of disseminated sulfides (DS-1) in the bottom and overlain by massive sulfide (MS) and olivine-sulfide cumulates (NTS-1), were overlain by the upper fine-grained subunits disseminated sulfides (DS-2) with a core of net-textured sulfides (NTS-2). The coarse-grained lherzolite with disseminated sulfides (DS-3) sharply cut through the upper subunit. All disseminated samples have Cu/Pd ratios (11,414–128,626) that exceed the mantle range. Additionally, the Pd/Ru ratios of DS-1 (1.26–13.2) are the lowest, followed by DS-2 (3.69–13.5), and highest in DS-3 (2.80–33.6). The exploration data indicate that the Ni and Cu contents and Cu/(Cu + Ni) ratios are significantly higher in DS-3 than in DS-2, while DS-1 shows more dispersed. The NTS-1 exhibits significant Ir and Ru depletion, with Cu/(Cu + Ni) decreasing with depth, eventually encountering Ir and Ru-riched MS. In addition, NTS-2 shows partially Ir depletion but Ru non-depletion, and Cu/(Cu + Ni) increases with depth. These signatures suggest that the lower and upper subunits, along with the coarse-grained unit, formed from platinum-group elements (PGE) in increasingly depleted magma, likely resulting from prior sulfide segregation before emplacement. Furthermore, the differences in Ir and Ru depletion and the variation in the Cu/(Cu + Ni) trend with depth between NTS-1 and NTS-2 were explained by the migration direction of fractional sulfide liquid during sulfide fractionation. We propose that the western end of the Jinchuan intrusion was formed by multi-stage magma emplacement. The strong correlation between exploration data (Ni, Cu, and Cu/(Cu + Ni)) and various sulfide mineralization layers suggests that delineating the spatial range of each sulfide mineralization could provide valuable information for deep mineral prospectivity mapping.

Sulfur and metal mobilization during the life cycle of an oceanic core complex: Implications for seafloor massive sulfide deposits formation at slow and ultra-slow spreading ridges

Seafloor massive sulfide (SMS) deposits at slow and ultra-slow spreading ridges are often spatially related to, or hosted in oceanic core complexes (OCCs). The specific oceanic crust architecture, magmatism, hydrothermal fluid circulation and lithologies at OCCs, however, imply different S and metal (e.g. Cu, Zn, Co, Ni) fluxes relative to well-structured oceanic crust at-fast spreading ridges and which are not yet fully constrained. The study of S and metal distribution in the ODP Hole 735B deep drill core from the Atlantis bank allows to understand these fluxes along detachment faults and to better constrain the source zone of S and metals for OCC-related SMS deposits. Significant depletion of S, Cu, Zn and Ni are observed within the upper 250 m of the drill core where intense deformation and hydrothermal fluid circulation occurred. During the complex tectono-magmatic-hydrothermal evolution of the Atlantis Bank, four important stages are recognized for S and metal mobilization: 1) magmatic stratification leading to a higher proportion of sulfide-rich and S, Cu, Zn and Co fertile oxide gabbros in the root zone of the Atlantis Bank detachment, 2) high temperature ductile deformation leading to magmatic sulfide reworking and onset of sulfide leaching with limited metal mobilization, 3) extensive sulfide leaching and metal mobilization during amphibolite to greenschist facies metasomatism and, 4) late stage secondary sulfide precipitation and S enrichment during low temperature fluid circulation. Mass balance calculations from the source zones of the Atlantis Bank detachment highlights that metal mobilization during hydrothermal alteration of gabbroic rocks along detachment faults can fully account for the formation of OCC-related SMS deposits at slow and ultraslow spreading ridges. The Atlantis Bank detachment system, however, is gabbroic-dominated and represent the magmatic end-member of OCCs and further work is necessary for understanding metal fluxes in ultramafic-dominated detachment systems.

Genesis of the Longfengchang polymetallic sulfide deposit in the southwest Fujian depression, southeast China, with a comparative study of the “Makeng-Type” iron deposit

The Southwest Fujian Depression Belt is a prominent metallogenic zone for skarn-type iron polymetallic deposits in China, with the Longfengchang (LFC) sulfur polymetallic deposit representing a medium-scale, sulfide-dominated deposit in this region. This study conducted a detailed analysis of the LFC deposit, focusing on its mineralogy, mineral composition, and in-situ sulfur isotopes, alongside a comparative study with the “Makeng-type” deposit. The study aims to elucidate the genesis of the LFC deposit, its relationship with the “Makeng-type” deposit, and the factors underlying differences in dominant economic minerals and resource scale. The LFC deposit is hosted within the skarn above the fault contact zone between the Lindi Formation sandstone and the Chuanshan–Qixia Formation carbonate, with mineralization stages classified as skarn-magnetite, quartz-sulfide, and carbonate. LFC garnets are primarily composed of CaO, TFeO, and SiO2, with minor Al2O3 and trace amounts of MgO and MnO, classifying them as distal exoskarn andradite. The presence of Mn3+ substituting for Fe3+ in garnet suggests that the ore-forming fluid during the garnet skarn stage was likely oxidizing and weakly acidic. LFC pyrites exhibit Co/Ni ratios primarily ranging from 1 to 10, decreasing from Py1 to Py3. In-situ sulfur isotope δ34S values range from −1.48 to 3.51 ‰, centering around 0 ‰, and increase from Py1 to Py3, suggesting a magmatic-hydrothermal origin and a cooling metallogenic process. Thus, the LFC deposit is classified as a magmatic-hydrothermal skarn-type deposit, consistent with the genesis of “Makeng-type” deposits. The absence of the Jinshe Formation, and mantle-derived magma contribution, and less developed “Si-Ca” interface may explain the smaller scale and different mineralization type in the LFC deposit compared to the “Makeng-type” deposit. The key prospecting area for large iron-sulfur polymetallic deposits in the Southwest Fujian Depression Belt should feature a nappe structural window, well-preserved Jinshe Formation, developed “Si-Ca” interface, Yanshanian high-K calc-alkaline to shoshonitic intrusions, and coeval mantle-derived magma.

Bio-mediated enhancement of supergene copper mineralization: Evidence from Cu isotope geochemistry

The relationship between microbial activity and the supergene modification of ore systems has been a major subject of debate. Here, we present isotopic evidence of microbial-driven secondary copper mineralization in the active cementation zone of the Las Cruces deposit, a volcanogenic massive sulfide deposit located in Iberian Pyrite Belt, Spain. Copper isotopic data show that the lower isotopic ratios (δ65Cu ≈ −9.2 ± 0.11 ‰, the lowest value measured worldwide in a supergene environment) are found in the upper part of the cementation zone, the same zone where the maximum copper grades are found and where there is direct evidence of extremophilic microbial activity. There is a tendency towards higher values downwards through the cementation zone (−9.2 ± 0.11 ‰ to + 1.67 ± 0.11 ‰ δ65Cu) and upwards into the former Cu-depleted gossan that originally capped the cementation zone (−7.79 ± 0.11 ‰ to −1.32 ± 0.11 ‰ δ65Cu). As microbes preferentially sequester the lighter isotope when incorporating intracellular Cu, this distribution indicates that microbes played a major role in the formation of the high-grade zones. Water arrives to the deposit enriched in isotopically heavy copper, likely because it has leached other ore bodies upstream. δ65Cu values of water currently flowing into the system are remarkably more positive than those in the ore, indicating that microbial activity is a major cause of copper isotope fractionation. At least half of the copper transported by the incoming waters remains within the ore body. Our best interpretation is that the large and high-grade cementation zone at Las Cruces is of biogenic origin, and that the primary mineralization acted as a trap for copper transported by groundwater, leading to the formation of an exotic mineralization distal to sub-eroded massive sulfides located upstream.