Search Results (44)

The Huize Ge-rich Pb-Zn deposit is an important part of the Sichuan–Yunnan–Guizhou carbonate-hosted Pb-Zn metallogenic area and is one of the most representative super-large deposits in the northeastern Yunnan Pb-Zn ore concentration area. The orebodies mainly occur in NE-trending interlayer fault zones. The Pb-Zn mineralization process of this deposit can be divided into the dolomite stage (I), sphalerite-galena stage (II), galena-sphalerite stage (III), and pyrite-calcite stage (IV). Based on a study of the deposit geology, we utilized LA-ICP-MS for in situ microanalysis of trace element compositions and element mapping of sphalerite from different stages to reveal the characteristics of the sphalerite trace element composition and occurrence mechanisms, understand the mineralization process, and constrain the genetic type of the deposit. This research shows that sphalerite color variations result from the multi-factor coupling of multiple trace element contents, element associations, and isomorphic substitutions among elements. Trace elements such as Mn, Fe, Cu, Ga, Ge, Ag, Cd, In, Sn, Sb, and Hg occur in the sphalerite lattice in the form of isomorphic substitutions or nanoscale mineral inclusions, whereas Pb occurs mainly as microscopic mineral inclusions (galena) in sphalerite. From the early to late stages of mineralization (SpI → SpII → SpIII), the mineralization temperature (132–205 °C) and sulfur fugacity (log₁₀ fS₂ = −15.29 to −19.89) both show a gradual decrease. During sphalerite crystallization in different stages, multiple trace elements exhibit coupled multi-element substitutions at the microscale: SpI: Zn²⁺ ↔ (Fe²⁺, Mn²⁺, Cd²⁺), 2Zn²⁺ ↔ 2Ag⁺ + Ge²⁺; SpII: Zn²⁺ ↔ (Fe²⁺, Cd²⁺), 2Zn²⁺ ↔ 2Ag⁺ + Ge²⁺, 3Zn²⁺ ↔ 2Cu²⁺ + Ge²⁺, 3Zn²⁺ ↔ 2(Cu, Ag)²⁺ + Ge²⁺, 2Zn²⁺ ↔ Ga³⁺ + Cu⁺, 2Zn²⁺ ↔ Ga³⁺ + (Cu, Ag)⁺; and SpIII: Zn²⁺ ↔ (Fe²⁺, Mn²⁺), 3Zn²⁺ ↔ 2Cu²⁺ + Ge²⁺, 3Zn²⁺ ↔ 2(Cu, Ag)²⁺ + Ge²⁺). Mn, Fe, and Ge are mainly enriched in SpI; Ga and Ag are mainly enriched in SpII; and Cd is mainly enriched in both SpI and SpII. By comparing the sphalerite trace elements signature of the Huize Ge-rich deposit with those of global typical MVT, SEDEX, VMS, epithermal, and skarn-type Pb-Zn deposits, and considering the deposit’s geological and geochemical characteristics, we suggest that the Huize Pb-Zn deposit is best classified as a medium- to low-temperature, carbonate-hosted Pb-Zn deposit. Full article

The Sichuan–Yunnan–Guizhou (SYG) metallogenic belt hosts numerous carbonate-hosted Pb-Zn deposits, yet the genesis of lead-dominated deposits remains poorly understood. This study investigates the Wuyi Pb deposit, a representative lead-dominated deposit in the SYG belt, through an integrated approach including field geology, fluid inclusion microthermometry, and C-H-O-S-Pb isotope geochemistry. The ore bodies occur as stratoid and lenticular lenses within the dolomitic limestone of the Ordovician Dajing Formation, controlled by both lithology and the Wuyi composite fold structure. Mineralization is divided into two stages: (I) pyrite–sphalerite–dolomite–calcite, and (II) galena–calcite–quartz–anhydrite. Fluid inclusion studies reveal that the ore-forming fluids are of the NaCl-H₂O system, characterized by moderate-low temperatures (Stage II, average 201 °C) and moderate-low salinities (Stage II, average 5.35 wt% NaCl eq.). Hydrogen and oxygen isotopes (δD = −100.97 to −76.33‰; δ¹⁸O_fluid = 7.09 to 12.10‰) indicate that the ore-forming fluids were predominantly meteoric in origin. Carbon isotopes (δ¹³C = −4.45 to 0.75‰) suggest that carbon was derived mainly from dissolution of the host carbonate rocks. Sulfur isotopes show a significant shift from Stage I (δ³⁴S = −12.40 to −3.00‰) to Stage II (δ³⁴S = −8.20 to −0.10‰ for sulfides; 25.00–29.40‰ for sulfates), indicating a transition from bacterial sulfate reduction (BSR) to thermochemical sulfate reduction (TSR) as the dominant sulfur reduction mechanism, with sulfur derived from Ordovician seawater sulfate. Lead isotopes (²⁰⁶Pb/²⁰⁴Pb = 18.10–25.37, ²⁰⁷Pb/²⁰⁴Pb = 15.50–21.72, ²⁰⁸Pb/²⁰⁴Pb = 38.29–53.90; μ = 9.30–21.05) demonstrate that metals were sourced predominantly from the Proterozoic basement rocks (Kunyang and Huili groups). Integration of geological, geochemical, and isotopic evidence indicates that the Wuyi Pb deposit formed during the Indosinian post-collisional intracontinental orogeny (ca. 230–200 Ma), when topography-driven meteoric water circulation extracted metals from the Precambrian basement and sulfur from Ordovician strata. Metal precipitation under the reduced sulfur model is caused by decreases in temperature and pressure and the water–rock reaction. This study establishes the Wuyi deposit as an MVT Pb deposit and provides a genetic model for lead-dominated mineralization in the SYG belt. Full article

The Beni Snassen belt (northeastern Morocco) hosts several Mississippi Valley-type Pb-Zn ± Cu occurrences localized along the Variscan basement/Lower Liassic carbonate interface within the Atlasic foreland system. This study integrates geological observations with organic petrography and C-O-S-Pb isotopic systematics to constrain the origin of mineralizing fluids, metal source, and ore-forming processes within a basin-scale metallogenic system. The host sequence consists of unmetamorphosed, dolomitized Pliensbachian carbonates with marl interbeds and organic-rich black shales. Mineralization is structurally focused along ENE-WSW and E-W faults and occurs as massive calcite-galena veins, “en échelon” tension gashes, vug fillings, and solution-collapse breccias. Ore-stage calcite exhibits restricted isotopic variability (δ¹³C = −4.7 to +1.2‰; δ¹⁸O = 14.9 to 19.7‰), consistent with rock-buffered basinal fluids and extensive fluid–carbonate interaction. Calculated δ¹⁸O_H2O values indicate precipitation from evolved saline brines variably mixed with meteoric waters. Galena δ³⁴S values (−20.9‰ to +10.3‰) reflect thermochemical sulfate reduction (TSR) under fluctuating redox conditions. Pb isotope compositions define a tight linear cluster between upper crust and orogene growth curves, indicating a predominantly upper crustal metal source, notably Triassic dolerite–diabase lithologies, with a possible contribution from organic-rich black shales. High-reflectance pyrobitumen (VR₀ up to 4%) indicates thermal conditions exceeding those predicted by local burial history, supporting long-distance migration of hydrocarbon-bearing metalliferous fluids from overpressured basin compartments, most plausibly the adjacent Neogene Guercif Basin. Fault reactivation during Late Miocene transtension fostered basin-scale fluid focusing and ore deposition. Hence, the Beni Snassen district represents a basin-integrated MVT system involving crustal metal leaching, organic-assisted metal transport, TSR-mediated sulfur reduction, and structurally focused fluid flow. These results refine metallogenic models for the Atlasic belts and highlight the exploration potential of structurally reactivated foreland basins hosting coupled hydrocarbon-hydrothermal systems. Full article

The Kocayayla Pb–Zn ± Cu vein-type mineralization is located in the Biga Peninsula, northwestern Türkiye. This study aims to constrain the geological, geochemical, and isotopic characteristics of the mineralization and to clarify its genetic classification. The deposit is hosted mainly by andesitic and basaltic andesitic rocks as well as schists and is structurally controlled by E–W-trending strike-slip faults. Mineralogical and petrographic identifications, XRD analyses, whole-rock geochemistry, and sulfur isotope data were integrated to evaluate ore-forming processes. Mineralization is temporally and spatially associated with propylitic and phyllic to argillic alteration and is concentrated within zones of intense silicification and chloritization, accompanied by quartz, sericite, kaolinite/nacrite, chlorite, and carbonate assemblages. The ore assemblage is dominated by galena, sphalerite, and subordinate chalcopyrite, with minor fahlore-group minerals. Rare earth element patterns of ore samples (whole rock) overlap with those of the wall rocks, whereas Pb–Zn enrichment reflects selective hydrothermal metal transport. Sulfur isotope compositions show limited internal variation and indicate sulfur derived predominantly from H₂S-dominated magmatic–hydrothermal fluids. Regional comparison of δ³⁴S datasets and reported Au contents across the Biga Peninsula indicates that Au-rich intermediate-sulfidation epithermal systems exhibit broader and more variable sulfur isotope ranges, whereas Au-poor intermediate-sulfidation epithermal systems show relatively restricted and near-zero δ³⁴S values. These features collectively support the classification of the Kocayayla mineralization as an Au-poor intermediate-sulfidation epithermal Pb–Zn system. Full article

Jurassic–Cretaceous marine–continental carbonate–evaporitic sequences in the Neuquén Basin of Argentina host numerous stratabound Ba–Sr deposits. Mineralization (Sr–barite, Ba–celestine, and minor Pb–Zn–Cu–Fe sulphides) occurs as bedding parallel lenses and crosscutting veins. The stratiform mineralization is formed by replacements of carbonate and gypsum beds and often exhibits typical zebra textures. Dissolution processes associated with Neogene regional uplift produced karstic cavities where a new generation of barite was deposited. Regionally, W to E distribution of carbonates/evaporites and that of Ba–Sr deposits is coincidental. Lower Cretaceous Sr–Ba deposits are spatially related to large N-S reverse faulting, frequently limited to the eastern limb of the folded structures. Average δ¹⁸O and δ³⁴S of stratiform and crosscutting vetiform mineralization do not differ significantly, suggesting a common source of sulphate and cations. Deposits spatially linked to areas with magmatic activity and those that are not have similar isotopic values, compatible with bacterial and/or thermochemical reduction of contemporaneous seawater sulphate, although sulphides only occur in deposits with evidence of nearby magmatic activity. Thermal convection of basinal brines leached metals from the Mesozoic sedimentary pile; Ba and Sr were extracted from siliciclastic and carbonate rocks, and sulphur from evaporite layers. Fluids related to Tertiary magmatism helped producing an epithermal mineral association composed of barite, quartz, adularia, and minor sulphides/sulphosalts hosted by veins. Arroyo Nuevo mine (Ba) is different, as it seems to be the product of hydrothermal SedEx deposition onto the anoxic seafloor. Full article

The Qingshan lead–zinc (Pb–Zn) deposit in northwestern Guizhou Province is a structurally controlled, carbonate-hosted system formed from basin-derived hydrothermal processes. Geology, fluid inclusion, and isotopic data reveal a multi-stage hydrothermal circulation after Emeishan Large Igneous Province (ELIP, ~260 Ma) tectono-thermal reactivation within the Sichuan–Yunnan–Guizhu triangle (SYGT) area. Fluid inclusion microthermometry indicates that ore-forming fluids were derived from deep sources influenced by enhanced crustal heat flow linked with possible thermal input from Indo-Caledonian tectonic activity after ELIP. Ore-stage calcite records mixed carbon derived from marine carbonates with additional inputs from organic matter and deep-sourced fluids, reflecting carbonate dissolution and fluid–rock interaction. Sulfide, together with fluid inclusion temperatures > 120 °C, indicates sulfur derived from evaporitic sulfate reduced by thermochemical sulfate reduction (TSR); the heavy sulfur signature and partial isotopic disequilibrium among coexisting sulfides reflect dynamic fluid mixing during ore deposition. Lead isotopes indicate metallogenic metals were leached mainly from Devonian–Permian carbonates with subordinate basement input. Ore precipitated by cooling, depressurization, and mixing of metal-rich, H₂S-bearing fluids in structurally confined zones where the carbonate–clastic interface effectively trapped ore-forming fluids, producing high-grade sphalerite–galena mineralization. Collectively, these data support a Huize-type (HZT) carbonate-hosted Pb–Zn genetic model for the Qingshan deposit. Full article

This study critically examines the early Cretaceous carbonate-hosted Zn-Pb (±Ba±Cu) deposits of the Malayer-Esfahan (MEMB) and Yazd-Anarak (YAMB) metallogenic belts in Iran, which have been inaccurately classified as Mississippi Valley type (MVT) deposits by Nejadhadad et al. (2025). Our findings reveal significant differences in mineralogy, fluid inclusion characteristics, and geochemical signatures compared to typical MVT deposits. These deposits are more akin to Irish-type Zn-Pb mineralization and formed in extensional and passive margin environments around the Nain–Baft back-arc basin. The normal faults in this back-arc rift can transform significantly during inversion and compressional tectonics, reactivating to behave as reverse faults and leading to new geological structures and landscapes. Our study highlights barite replacement as a crucial factor in forming sediment-hosted Zn-Pb (±Ba±Cu) and barite-sulfide deposits. Based on textural evidence, fluid inclusion data, and sulfur isotope analyses, we propose that barite plays a fundamental role in controlling subsequent Zn-Pb (±Ba±Cu) mineralization by serving as both a favorable host and a significant sulfur source. Furthermore, diagenetic barite may act as a precursor to diverse types of sediment-hosted Zn-Pb (±Ba±Cu) mineralization, refining genetic models for these deposits. Sulfur isotope analyses of Irish-type deposits show a broad δ³⁴S range (−28‰ to +5‰), indicative of bacterial sulfate reduction (BSR). Nevertheless, more positive δ³⁴S values (+1‰ to +36‰) and textural evidence in shale-hosted massive sulfide (SHMS) deposits suggest a greater role for thermochemical sulfate reduction (TSR) in sulfide mineralization. Full article

The Bushy Park Pb-Zn deposit, hosted in unmetamorphosed carbonates of Neoarchean age, displays similarities to Phanerozoic Mississippi Valley-type (MVT) and Irish-type deposits. Mineralization is dated, by radiogenic methods, to Paleoproterozoic time. As such, Bushy Park is one of the oldest mineral deposits of this type in the world. Synsedimentary silicification and dolomitization preserve sedimentary fabrics, including microbial laminates, stromatolites, and oolites. Dolomitization likely was by evaporated seawater, as in Phanerozoic analogs. Structural control on mineralization, particularly solution collapse breccias, is similar to many Phanerozoic MVT and Irish-type deposits. Fluid inclusion data indicate three fluid endmembers involved in mineralization: a high-temperature, moderate-to-high salinity fluid; a low-temperature, moderate-to-high salinity fluid; and a moderate-to-low temperature, low salinity fluid. Saline fluids may have been sourced by evolved, evaporated seawater, and dilute fluids by meteoric and/or normal seawater. The fluids repeatedly mixed during ore and gangue mineral formation. Compositional zoning in gangue dolomite cement indicates that mineralizing fluid chemistry fluctuated over time. Petroleum inclusions and solid bitumen indicate that petroleum (oil) was an important fluid component at Bushy Park. Petroleum may have played a critical role in sulfur availability, addressing the issue of limited oceanic sulfate prior to and during the Great Oxidation Event. Full article

The Zaghouan Fluorite Province (ZFP) encloses F-Ba(Pb-Zn) ores hosted within Jurassic carbonate series, in northeastern Tunisia. Critical breakthroughs on the Jebel Stah fluorite deposits, an MVT-style F-mineralization, have been made within the Lower Jurassic limestones along the Zaghouan Fault, which is a major target for mineralization. This study presents the first REE-Y analyses conducted by LA-ICP-MS on fluorites in Tunisia, and specifically on the fluorites of Jebel Stah deposit. This analytical technique provides highly accurate insights into the geochemical regime of mineralizing fluids and the related scavenging sources. Distinct geochemical characteristics between two fluorite generations (G1 and G2) were revealed. Fluorites (Fl2) from the early generation (G1) showed low ΣREE + Y (36.3 and 39.73 ppm, respectively). When normalized to chondrites, early fluorite G1 displayed a bell-shaped REE + Y pattern with a depletion in LREE relative to HREE and a slight MREE hump. Late fluorite (Fl3) generation (G2) displayed higher ΣREE + Y concentrations (77.43 ppm), but an almost similar REE pattern. Ce/Ce* ratios demonstrated strong negative Ce anomalies in all fluorites, while Eu/Eu* ratios indicated weak negative Eu anomalies. The positive Y anomaly observed in the REE + Y patterns of fluorites G1 and G2 suggests Y-Ho fractionation in the fluid system. Moreover, significant degrees of differentiation between terbium (Tb) and lanthanum (La) have been observed in all fluorite samples. The plot of fluorites from both fluorite generations on the Tb/La–Tb/Ca diagram gives evidence of the sedimentary hydrothermal origin of the ore-forming fluids in the Jebel Stah F-deposit. Sr isotopes show that the mineralizing fluids are radiogenic and deeply sourced basinal brines, whereas the small variation in ⁸⁷Sr/⁸⁶Sr ratios suggests a similar source for Sr in fluorites G1 and G2. These results allow us to conclude that the economic fluorite (G1) ore of Jebel Stah was deposited due to the interaction of the deeply sourced hydrothermal fluid with the carbonated host rocks (dolomitization, an increase in pH, and Ca activity), whereas the late fluorite (G2) is an accessory and could have resulted from the mixing of the hydrothermal fluid with shallow meteoric waters. Full article

Hydrothermal alteration provides critical information for both the exploration and scientific research of hydrothermal uranium deposits. The Xiangshan uranium ore field, the largest volcanic-hosted uranium deposit in China, is characterized by different alterations, including hematitization, illitization, sericitization, chloritization, carbonation and silicification. However, the mineralogical and geochemical characteristics of hydrothermal alterations and their relationships with uranium mineralization remain unclear. In this study, we conducted detailed petrography, TIMA mapping, μ-XRF analyses, mass balance calculations and thermodynamic modeling on the hematitized and illitized porphyritic lava from the Zoujiashan deposit in the Xiangshan ore field. During hematitization, hematite and albite are produced, while quartz, K-feldspar, chlorite, sericite and biotite are consumed, consistent with the increase in Na₂O, Al₂O₃, Fe₂O₃-T, U, As, Pb, Cu, Sc, V, Zr, Y, Hf and Th and the loss of K₂O, MgO, Li, Zn, Ni and Ba. The production of hydrothermal hematite, illite and sericite indicates that the ore fluids are acidic and oxidized. Such physiochemical conditions are favorable for uranium transport as UO₂Cl₂(aq), UO₂SO₄(aq) and UO₂OH⁺. Geological processes such as fluid–rock interactions, fluid mixing and fluid boiling could cause fO₂(g) decrease, pH increase and temperature decrease and therefore result in the decrease in uranium solubility and mineralization. Full article

The large-scale vein-type Zn-Pb-Ag deposit in the Eastern Qinling Orogen (EQO) has sparked a long-standing debate over whether magmatism or metamorphism was the primary control or factor in its formation. Among the region’s vein-type deposits, the large-sized Bailugou deposit offers a unique opportunity to study this style of mineralization. Similar to other deposits in the area, the vein-type orebodies of the Bailugou deposit are hosted in dolomitic marbles (carbonate–shale–chert association, CSC) of the Mesoproterozoic Guandaokou Group. Faults control the distribution of the Bailugou deposit but do not show apparent spatial links to the regional Yanshanian granitic porphyry. This study conducted comprehensive H–O–C–S–Pb isotopic analyses to constrain the sources of the ore-forming metals and metal endowments of the Bailugou deposit. The δ³⁴S_CDT values of sulfides range from 1.1‰ to 9.1‰ with an average of 4.0‰, indicating that the sulfur generated from homogenization during the high-temperature source acted on host sediments. The Pb isotopic compositions obtained from 31 sulfide samples reveal that the lead originated from the host sediments rather than from the Mesozoic granitic intrusions. The results indicate that the metals for the Bailugou deposit were jointly sourced from host sediments of the Mid-Late Proterozoic Meiyaogou Fm. and the Nannihu Fm. of the Luanchuan Group and Guandaokou Group, as well as lower crust and mantle materials. The isotopic composition of carbon, hydrogen, and oxygen collectively indicate that the metallogenic constituents of the Bailugou deposit were contributed by ore-bearing surrounding rocks, lower crust, and mantle materials. In summary, the study presents a composite geologic-metallogenic model suggesting that the Bailugou mineral system, along with other lead-zinc-silver deposits, porphyry-skarn molybdenum-tungsten deposits, and the small granitic intrusions in the Luanchuan area, are all products of contemporaneous hydrothermal diagenetic mineralization. This mineralization event transpired during a continental collision regime between the Yangtze and the North China Block (including syn- to post-collisional settings), particularly during the transition from collisional compression to extension around 140 Ma. The Bailugou lead-zinc-silver mineralization resembles an orogenic-type deposit formed by metamorphic fluid during the Yanshanian Orogeny. Full article

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. Full article

Mississippi Valley-type (MVT) Pb-Zn deposits are a subtype of sedimentary-hosted mineralization. These deposits are hosted by carbonate sequences in passive-margin tectonic settings. This paper uses the Fry technique and distance distribution analysis to model the spatial distribution pattern of MVT Pb-Zn deposits in the west of Semnan province (Iran) and their association with some geological features, aiming at mapping mineral prospectivity in the area. The modeling results reveal that NE–SW trending faults and Permian-Cretaceous dolomites and limestone are, respectively, major structural and lithological controlling factors of mineralization that operate as conduits and physicochemical subsystems of ore formation. The integration of the corresponding evidence maps of the controlling factors with a model of the geochemical signature of MVT Pb-Zn deposits through a supervised random forest approach, a machine learning technique, gains an exceptional prospectivity map predicting 100% of the known MVT Pb-Zn deposits in only 15% of the study area, which is an achievement. The recognized targets can be planned for further exploration. Full article

Iran hosts more than 350 Precambrian to Cenozoic sediment-hosted Zn-Pb±Ba and barite-sulfide deposits, including shale-hosted massive sulfide (SHMS, also called SEDEX) and Irish-type and Mississippi Valley-type (MVT) mineralization, and barite is a common mineral in these deposits. In the SHMS deposits, barite is typically found as fine-grained disseminations in thin laminae. In these deposits, the sulfide laminae often occur as diagenetic replacements and as bands containing authigenic and diagenetic barite and pyrite framboids. In the Irish-type Zn-Pb-Ba and stratabound barite-sulfide deposits, barite exhibits various textures, including fine-grained disseminated barite, banded zebra textures, veins, and massive barite lenses. In some of the giant Irish-type deposits, as well as in the stratabound barite-sulfide mineralization, the main stratabound sulfide ore is developed within a barite envelope and is characterized by the replacement of barite and pyrite by chalcopyrite, galena, and sphalerite. In the MVT deposits, the formation of barite is often related to dolomitization, and sulfide mineralization involves the replacement of the dolomitized carbonate rocks, as well as associated barite. Fluid inclusion studies on the Irish-type deposits indicate that the temperatures and salinities of the sulfide-forming fluids are higher compared to those of the barite-forming fluids. Fluid inclusion analyses of coarse-grained barites from Irish and MVT deposits reveal their hydrothermal origin. The δ³⁴S values of sulfide minerals (pyrite, sphalerite, and galena) in Irish-type deposits exhibit a broad range of low values (mostly −28 to +5‰), primarily revealing a process of bacterial sulfate reduction (BSR). However, the textures (replacement, colloform, and banded) and more positive sulfur isotope values (+1 to +36‰) in the SHMS Zn-Pb deposits suggest that bacterial sulfate reduction (BSR) plays a less significant role. We suggest that thermochemical sulfate reduction (TSR) connected to the direct replacement of barite plays a more relevant role in providing sulfur for the sulfide mineralization in the SHMS, barite-sulfide, and MVT deposits. Based on the textual evidence, sulfur isotopic data, and fluid inclusion studies, barite has been identified as a key controller for the subsequent Zn-Pb mineralization by providing a suitable host and significant sulfur contribution in the sediment-hosted Zn-Pb and stratabound barite-sulfide deposits. This implies that diagenetic barite might be a precursor to all types of sediment-hosted Zn-Pb mineralization. Full article

The Fuli Pb-Zn deposit is situated at the southwestern margin of the Yangtze Block in Yunnan. The deposit, which is hosted in the Permian Yangxin Formation dolomite, is a recent discovery. Our study indicates a significant presence of fluid inclusions in sphalerite from the Fuli Pb-Zn deposit, with fewer inclusions observed in dolomite and calcite. We conducted comprehensive petrographic, microthermometric, and laser Raman analyses on the inclusions within sphalerite and dolomite. Additionally, six samples of dolomite from the mineralization period were selected for H-O isotope analysis. The results of our study reveal the characteristics of ore-forming fluids and explore the mechanisms of ore formation. The study results indicate that the Fuli Pb-Zn deposit is a low- to medium-temperature hydrothermal deposit with fluid inclusions mainly composed of two-phase gas-liquid inclusions. Salinity and homogenization temperature analyses affirmed that there are two types of fluids present, one with low salinity and the other with high salinity. Laser Raman tests demonstrated the presence of CH₄, N₂, and CO₂ in the gas phase of the inclusions. Microthermometric analyses indicated that the sphalerite ore-forming fluids consist of a multicomponent system of Mg²⁺ and Ca²⁺ enriched fluids. The features of the ore-forming fluids in the Fuli deposit arise from a blend of high-temperature, low-salinity metamorphic fluids and low-temperature, high-salinity basin brines. The basin brines in question have the potential to emanate from the Youjiang Basin. The formation of the ore is ascribed to the TSR and the mixing of fluids. The combination of these processes provided the requisite materials (SO₄²⁻), catalysts (Mg²⁺), and reducing agents (organic matter, CH₄, and H₂S) required to initiate the thermochemical sulfate reduction (TSR). As the TSR proceeded, it caused a shift in the pH of the fluids, thus promoting the precipitation of metal sulfides. Full article