Dispersed elements such as Ge, Ga and Cd attract increasing attention due to their wide use in modern high-tech or emerging industries. These elements are typically enriched in Mississippi valley-type (MVT) Pb-Zn deposits, which have not been well understood for the enrichment mechanisms due to their low-concentration and dispersed features. The Niujiaotang Zn-Cd deposit located at the southwestern China is one of the MVT Pb-Zn deposits extremely enriched in Cd, hosting more than 5000 tonnes of Cd with an average Cd grade of 1.4 wt % in sphalerite. To understand the critical factors controlling the abnormal enrichment of Cd, the elemental compositions and S-Zn-Cd isotopes of Cd-bearing sphalerite were investigated. The results show that the sphalerite in the Niujiaotang deposit can be divided into two generations (Sp1 and Sp2) from the early to the late hydrothermal stage, of which the Sp1 (3208-20521 ppm, mean of 10,812 ppm) has higher Cd concentrations than those of the Sp2 (Cd = 364-13500 ppm, mean of 4222 ppm). The Cd-rich Sp1 is coexistent with bitumen and abundant in organic gas-bearing fluid inclusions (e.g., CH4 and C2H6), suggesting that Cd enrichment might be associated with organic matter involvement. The high delta 34S values (14.0%o to 34.6%o) of sulfides are similar to those of sulfates in the strata, corroborating that TSR (thermochemical sulfate reduction) occurred between sulfates and organic matter. The low delta 66Znsphalerite (-0.27%o to 0.09%o) and delta 114/110Cdsphalerite (-0.72%o to-0.10%o) values, in combination with the widespread paleo-oil reservoirs in the study region, suggest that organic ligands derived from oil-field brines contributed to the transportation of Zn and Cd. The above results support that organic matter played critical roles in both the metal transportation and precipitation, which thus promoted the abnormal enrichment of Cd.

The discovery of altered rock-type gold orebodies in southeastern Guizhou (southwestern Jiangnan orogen) highlights the region's significance as a major gold province. However, the timing and the ore-forming processes remain poorly constrained, hindering a comprehensive understanding of gold metallogenic patterns. The Kengtou gold deposit (>15 tons Au) comprises both quartz vein-type and altered rock-type orebodies. Two types of hydrothermal monazite (Mnz1, Mnz2) were identified in this study. Mnz1, associated with pre-ore ankerite (Ank1) and rutile, occurs within unmineralized metamorphic rocks. In contrast, Mnz2 is spatially associated with auriferous sulfides within gold orebodies. Trace-element analyses show that Mnz1 has significantly higher total rare earth element (Sigma REE) concentrations (430,658-583,738 ppm, mean = 565,224 ppm) than Mnz2 (67,779-172,804 ppm, mean = 137,558 ppm), although both exhibit similar hydrothermal-type chondrite-normalized REE distribution patterns. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb dating yielded lower-intercept ages of 443 +/- 16 Ma (Mnz1) and 410 +/- 13 Ma (Mnz2). These ages constrain two distinct hydrothermal episodes: The earlier episode (ca. 443 Ma) represents a pre-ore stage related to Caledonian regional greenschist-facies metamorphism that triggered widespread sericitization, while the later episode (ca. 410 Ma) marks the main gold mineralization stage during late Caledonian extension, where fluid-rock interaction led to the precipitation of gold-bearing pyrite. Overall, we propose that the recognition of two episodes of Caledonian hydrothermal activity has implications for district-scale gold exploration in the southwestern margin of the Jiangnan orogen.

Dispersed elements such as Ge, Ga and Cd attract increasing attention due to their wide use in modern high-tech or emerging industries. These elements are typically enriched in Mississippi valley-type (MVT) Pb-Zn deposits, which have not been well understood for the enrichment mechanisms due to their low-concentration and dispersed features. The Niujiaotang Zn-Cd deposit located at the southwestern China is one of the MVT Pb-Zn deposits extremely enriched in Cd, hosting more than 5000 tonnes of Cd with an average Cd grade of 1.4 wt% in sphalerite. To understand the critical factors controlling the abnormal enrichment of Cd, the elemental compositions and S-Zn-Cd isotopes of Cd-bearing sphalerite were investigated. The results show that the sphalerite in the Niujiaotang deposit can be divided into two generations (Sp1 and Sp2) from the early to the late hydrothermal stage, of which the Sp1 (3208–20521 ppm, mean of 10,812 ppm) has higher Cd concentrations than those of the Sp2 (Cd = 364–13500 ppm, mean of 4222 ppm). The Cd-rich Sp1 is coexistent with bitumen and abundant in organic gas-bearing fluid inclusions (e.g., CH4 and C2H6), suggesting that Cd enrichment might be associated with organic matter involvement. The high δ34S values (14.0‰ to 34.6‰) of sulfides are similar to those of sulfates in the strata, corroborating that TSR (thermochemical sulfate reduction) occurred between sulfates and organic matter. The low δ66Znsphalerite (–0.27‰ to 0.09‰) and δ114/110Cdsphalerite (–0.72‰ to –0.10‰) values, in combination with the widespread paleo-oil reservoirs in the study region, suggesting that organic ligands derived from oil-field brines contributed to the transportation of Zn and Cd. The above results support that organic matter played critical roles in both the metal transportation and precipitation, which thus promoted the abnormal enrichment of Cd.

The Sichuan-Yunnan-Guizhou Pb-Zn Metallogenic Province is a key component of the extensive low-temperature metallogenic domain in southwestern China. Both the Yamang and Weishui faults act as controlling structures for ore deposition in this region. The Shanshulin deposit is the most representative Pb-Zn deposit in the Weishui fault zone, with a combined 2.7 Mt of sulfide ores. We carried out a detailed geological and geochemical study of the Shanshulin deposit and compared it with the super-large-scale Zhugongtang Pb-Zn deposit in the Yamang fault zone (Pb + Zn approximate to 3.27 Mt). Based on scanning electron, reflected and transmitted light microscopy, we identified three types and two sub-types of sphalerites in the Shanshulin deposit. Laser ablation inductively coupled plasma mass spectrometry revealed distinct trace element signatures in four generations of sphalerite. Sp1 is enriched in Fe-Mn-Pb (Fe up to 54 268 ppm), whereas Sp2-b shows a dominance of Ga. Ge is consistently elevated (average 185 ppm), with Ge-Ag-Cd concentrations increasing from Sp1 onwards. Notably, Fe-Mn-Pb and Ga exhibit antithetic trends: Fe-Mn-Pb concentrations peak in Sp1, then decrease to a minimum in Sp3, whereas Ga progressively increases to Sp3. Ni-Cu-Sb show no stage-dependent patterns and the Co-As-Se-In-Sn-Tl contents are below the detection limit. The earlier stage sphalerite is enriched in Fe and Mn and contains more impurities, whereas the later stage sphalerite is enriched in Cd and Ag. Empirical formula calculations of the trace elements in all the sphalerite generations reveal a progressive decrease in the formation temperature of sphalerite from the early to late stages, with corresponding ore-forming temperatures of Sp1 = 156-280 degrees C (mean 221 degrees C), Sp2-a = 68-288 degrees C (mean 162 degrees C), Sp2-b = 110-223 degrees C (mean 181 degrees C) and Sp3 = 44-239 degrees C (mean 123 degrees C). The trace element features in all the sphalerite generations correspond with those of typical Mississippi valley-type deposits. There is a significant binary correlation between Ge and Ag, indicating that the coupled substitution is 3Zn(2+) <-> Ge4+ + 2Ag(+). The Shanshulin deposit has geological and geochemical signatures comparable with the Zhugongtang Pb-Zn deposit within the same metallogenic belt, suggesting significant exploration potential for Pb-Zn mineralization along the Weishui fault zone.

As an important part of the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic province (SYGMP), the Wuzhishan ore field in Puding, Guizhou, SW China, is situated on the southwestern margin of the Yangtze Block. More than 20 different scale Pb-Zn deposits and occurrences have been explored in the area. Among them, the Nayongzhi deposit represents the first large-scale Pb-Zn deposit identified in the Wuzhishan ore field, with proven Pb + Zn resources exceeding 1.35 Mt. Most Pb-Zn orebodies occur as stratiform and are hosted in dolostone of the Lower Cambrian Qingxudong Formation, and the Dujiaqiao deposit is the only one hosted in dolostone of the Late Ediacaran Dengying Formation in the ore field. Although the Dujiaqiao deposit is medium-sized, its mineral assemblage and wall-rock alteration similar to those of the Yuhe ore block in the Nayongzhi deposit. Establishing a genetic link between the Late Ediacaran-hosted cross-stratal vein-type mineralization at Dujiaqiao and the Cambrian-hosted stratiform mineralization at Nayongzhi is a key scientific problem for understanding multi-stratal Pb-Zn mineralization and further exploration guidance. Moreover, the critical metals, including Cd, Ge, Ga, and In, are mainly recovered as by-product and hold considerable economic significance, and its enrichment characteristics and mechanisms in the Dujiaqiao deposit remain unclear. Sphalerite from the Dujiaqiao deposit was divided into three generations: early-stage black (Sp1), middle-stage reddish-brown (Sp2), and late-stage light-yellow (Sp3). In-situ trace‑element and sulfur-isotope analyses of sphalerite and other sulfides were performed using LA-ICP-MS and LA-MC-ICP-MS, respectively. The results demonstrate that sphalerite from both the Dujiaqiao and Nayongzhi deposits exhibits similar trace-element patterns, with enrichment of low-temperature elements (e.g., Cd, Ge) and depletion in high-temperature elements (e.g., Mn, Co, In, Sn). Concentrations of Ge (0.75–225 ppm, avg. 61.3 ppm, n = 98) and Cd (301–3858 ppm, avg. 1348 ppm, n = 98) meet or exceed the threshold grades for potential by-product recovery. Notably, Ge is enriched in Sp1 and Sp2, whereas Cd is most enriched in Sp2, followed by Sp3. These elements are incorporated into sphalerite by lattice substitution; Ge enters via coupled substitution dominated by 3Zn2+ ↔ Ge4+ + 2(Ag+, Cu+), and Cd via Zn2+ ↔ Cd2+ replacement. Trace-element geothermometry yields ore-forming temperatures of 104.3–231.5 °C (avg. 145.4 °C, n = 71), indicating low‑ to moderate‑temperature hydrothermal conditions, slightly higher than that of the Nayongzhi deposit. Sphalerite δ34S values (+18.0‰ to + 24.7‰, avg. + 21.5‰, n = 49) closely resemble that of the Late Ediacaran marine sulfate, indicating that the sulfur was derived mainly from thermochemical sulfate reduction (TSR) of sulfate hosted in Dengying Formation. Overall, the Dujiaqiao and Nayongzhi deposits share similar geological and geochemical characteristics except for its host rocks. It is suggested that both belong to MVT Pb-Zn deposits formed during the same mineralizing event. The Dujiaqiao deposit represents deeper, structurally controlled channel-facies mineralization, whereas the Nayongzhi deposit records shallower, bedding‑parallel replacement mineralization. The research provides new geological and geochemical constraints on the Late Ediacaran‑hosted cross‑stratal vein‑type Pb‑Zn mineralization in the Wuzhishan ore field and offer implications for future Pb-Zn exploration in the area

Abstract Mississippi Valley-type (MVT) deposits are important sources of Pb, Zn, and critical metals such as Ag, Ga, and Ge. However, their metal sources and the mechanisms behind the formation of giant deposits remain contentious. Here, we address these questions by studying Hg-Pb isotope signatures of MVT sulfides and potential source rocks in the southeastern Yangtze block. These data reveal that the ore metals come from at least two upper-crustal sources: shallower sedimentary rocks and deeper metamorphic basement. The giant deposits show isotopic signatures compatible with increased metal input from the deeper basement. Together with higher ore-fluid temperatures and salinities, as well as preferential localization of larger deposits along major fault intersections, this suggests that large MVT deposits form where specific geological factors coincide during regional orogeny, driving high fluid fluxes and deep fluid circulation. These can efficiently mobilize metals from basement rocks and concentrate them in shallow carbonate traps.

Lithium (Li), a critical material for clean energy technologies, faces escalating global demand driven by the rapid growth of battery-powered industries. Bauxite-associated Li resources are extensively distributed and hold immense potential, offering a promising alternative for countries lacking conventional Li reserves. This study employs unsupervised machine learning-integrating the K-means++ clustering algorithm (KCA) and principal component analysis (PCA)-to investigate the Li distribution and enrichment mechanisms in the Permian karst bauxite-bearing rocks of northern Guizhou, China. KCA-based lithological classification categorized 435 samples into eight geochemically distinct clusters, achieving 65.8 similar to 100% consistency with manual identification. PCA dimensionality reduction revealed that the first three principal components explain 65.9% of the geochemical variance, with weathering processes (governed by SiO2, TiO2, Al2O3 and K2O) identified as the primary control on Li enrichment. Our findings confirm that Li predominantly accumulates in overlying/underlying aluminous rocks, clastic bauxites, and compact bauxites, peaking during weak-to-moderate lateritization. Additionally, the Al/Si and Ti/K ratios are identified as crucial indicators for Li enrichment, with the optimal intervals associated with significant Li enrichment ranging from lg(alpha Al/Si) = -0.08 to 0.75 and lg(beta Ti/K) = 0.5 to 1.5. Overlapping these ranges exhibits the highest Li concentrations (up to 5, 404 & times; 10(-6)). It is further confirmed that moderate clay mineralization and low-grade bauxite formation, coupled with intermediate weathering intensity, create favorable conditions for Li accumulation. This work establishes a machine learning-driven framework for rapid lithological discrimination and resource assessment in complex bauxite systems, providing critical insights for exploration of clay-type Li deposits.

The China Koktokay Pegmatite Group is an important metallogenic region where major rare-metal ores are mined. Here, we present new low-temperature thermochronological data to contribute to the understanding of the Koktokay Pegmatite Group’s exhumation and preservation history. Apatite U–Pb ages of ∼176 Ma, zircon fission-track ages of ∼150 Ma, zircon (U–Th)/He ages of ∼82–52 Ma, apatite fission-track ages of ∼69–49 Ma, and apatite (U–Th)/He ages of ∼90–52 Ma were obtained from three samples of the No. 3 pegmatite and the contemporaneous Aler granitic batholith in the Koktokay area. Our thermochronological data and inverse thermal history modeling reveal a moderate-to-rapid basement cooling phase during the Cretaceous (∼150–65 Ma), with an average cooling rate of ∼1.53 °C–1.06 °C/Ma. It is envisaged that this phase eventually uplifted and exhumed the pegmatite group, with erosion in the Cenozoic era being limited. Combined with previously published geochronological and thermochronological data, a multi-stage cooling history for the pegmatite group can be established. Following its magmatic–hydrothermal formation in the Late-Triassic (∼220–200 Ma), two phases of accelerated regional cooling (i.e., in the late Triassic to Early Jurassic, ∼200–180 Ma; and the mid-Jurassic to Late Jurassic, ∼176–150 Ma) can be recognized. The intense cooling in the Cretaceous is associated with the final exhumation of the pegmatite group to the surface, and some Li–Ru–Cs-mineralized pegmatites formed at the distal end of the Koktokay Pegmatite Group may have been exhumed and denuded. Furthermore, we propose a relatively intense denudation of the Koktokay Pegmatite Group, which is unfavorable for the preservation of rare-metal pegmatite bodies.

The Pingqiao deposit, a newly discovered large-scale fluorite-cookeite deposit in Guizhou, Southwest China, represents a new and unusual type of lithium (Li) mineralization. Recent exploration has identified over 90 kt of Li2O reserves. Using in situ laser ablation-inductively coupled plasma-mass spectrometry to analyze the primary Li bearing mineral, cookeite, and associated minerals, as well as major and trace elements and Li isotopes of the ore-hosted strata, this study investigated the spatial distribution, occurrence, and enrichment mechanisms of Li. The study yielded new geological and geochemical evidence to improve our understanding of Li mineralization. The results indicate that two generations of cookeite (Ckt-I and Ckt-II) and fluorite formed during the same hydrothermal stage, with crystallization temperatures of between 95 degrees C and 270 degrees C. Ckt-I is enriched in light rare earth elements and exhibits a negative Eu anomaly (average of 0.55), which decreases in Ckt-II (average of 0.88). This indicates gradual cooling of the ore-forming fluids, accompanied by the tetrad effect caused by fluorine (F) in the fluid. Nanoscale secondary ion mass spectrometry mapping of pyrite and cookeite suggests a shared Li and F source from the same mineralization event. The ore's Li isotope composition (-4.06%0 to +3.15%0, average of -1.24%0) is slightly negative, with variations implying upward fluid migration from deep Li-rich basement rocks, possibly mixed with basinal fluids. The U-Pb dating results of calcite associated with cookeite (134 +/- 4.5 Ma) and fluorite (Sm-Nd isochron age: 148 +/- 8 Ma) aligning with the regional ages links the mineralization event to medium-to low-temperature basinal fluids of the Yanshanian movement. Based on the research described in the previous paragraph and comparison with other types of Li deposits, a metallogenic model for the Pingqiao deposit is proposed, which offers new insights into this unusual type of Li mineralization.

The Northwestern Guizhou Pb-Zn metallogenic area is a significant part of the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic province. Orebodies of Pb-Zn deposits in this area are hosted in multi-layers of strata, structurally constrained by the thrusting fault-fold system and close spatially related to the Permian Emeishan basalt. However, there are still some controversies on the source of the ore-forming materials and the genesis of those deposits because of relatively limited researches. In this study, taking the Liangyan Pb-Zn deposit in the Northwestern Guizhou as research object, we have carried out the Pb isotopic analysis of sulfide minerals and C-O isotopic analysis and REE elemental analysis of ore-stage calcites from the deposit, aiming to elucidate the source of ore-forming materials and the genesis of the carbonate-hosted lead-zinc deposit in the northwestern Guizhou. The C-O isotopic data of calcites indicate that the carbon of ore-forming fluids was predominantly sourced from the dissolution of the Carboniferous carbonate host rocks with a minor contribution from organic matter within the sedimentary sequences. The oxygen was possibly derived from the hot basinal brine and ore-hosting carbonate rocks. The Pb isotopes of sulfide minerals and the REE compositions of calcites suggest that the ore-forming metals and rare earth elements within the ore-forming fluids were mainly originated from the binary mixture of the Mesoproterozoic Kunyang Group metamorphic basement and the ore-hosting Carboniferous carbonate rock. Combined with geological and geochemical characteristics of the Liangyan Pb-Zn deposit, it is suggested that the Liangyan deposit belongs to a thrusting fault-fold system-controlled MVT Zn-Pb deposit.

Niobium is a strategic critical metal. Its supply is vulnerable to geopolitical instability, which necessitates the development of novel resources. Here, we propose a novel, efficient and clean two-stage leaching process for recovering niobium from clay-weathered crust of the Emeishan basalt in the Sichuan-Yunnan-Guizhou region of southwestern China. The primary leaching involves roasting (600 degrees C)-sulfuric acid (20 %) leaching, which selectively dissolves the aluminium-bearing boehmite and kaolinite to concentrate the niobium-bearing anatase and illite, and simultaneously yield byproducts such as ferric hydroxide, aluminium hydroxide and ammonium sulfate. The secondary leaching utilizes the byproduct ammonium sulfate as an agent for ammonium sulfate roasting (450 degrees C), which couples with sulfuric acid (35 %) leaching to enhance niobium extraction. This gives a maximum extraction efficiency of 91.06 %. Thermodynamic analysis revealed that ammonium bisulfate (thermal decomposition product of ammonium sulfate) can spontaneously decompose niobium-bearing minerals (anatase and illite) (Delta G(theta)<0), thereby releasing niobium to form the soluble niobium trioxysulfate. Subsequent leaching with 35 % sulfuric acid enables highly efficient niobium extraction. Kinetic analysis demonstrated that the niobium leaching process is jointly controlled by interface transfer and diffusion through the inert product layer (E-a = 50.54 kJ/mol). Efficient absorption of exhaust gases with sulfuric acid and ammonia would minimize air pollution, and the final leaching residue comprises mainly ammonium aluminum sulfate dodecahydrate (ammonium alum). This minimizes solid waste production. The technique integrates high extraction efficiency, low environmental impact, and comprehensive resource utilization, which facilitates sustainable development of refractory niobium resource.

Metal zonation patterns are common in Mississippi Valley-type (MVT) deposits but have received compara-tively little attention. The recognition of such patterns can help to fingerprint fluid flow paths and provide valuable vectors for near-mine exploration. The Nayongzhi deposit (30.1 million tonnes [Mt] at 6.57% Zn and 0.91% Pb) exhibits clear lateral and vertical zonation patterns in ore types and metal ratios, making it an ideal case study to explore the behavior of other geochemical zonation markers. In this contribution, we report zona-tion patterns observed in both carbonate C-O isotope compositions and the trace element chemistry of sphal-erite. Ore-related dolomite shows systematically higher delta 13CV-PDB (Vienna-Pee Dee Belemnite) and delta 18OV-SMOW(Vienna-standard mean ocean water) values with increasing distance to the feeder structure, probably reflecting a decrease in the fluid-rock ratios. In addition, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis of sphalerite revealed systematic spatial and temporal variations in trace element con-tents. The contents of Mn, Fe, Cu, Ga, Ge, and In decrease with distance from the feeder fault, whereas the contents of Cd increase. Manganese, Fe, Ge, and Tl are also concentrated in early sphalerite, whereas Ga and Cd are more abundant in later sphalerite. Such variations appear to be predominantly governed by changes in physicochemical parameters, such as temperature, fS2, and fluid composition. Finally, multivariate regression analysis identified three footprint elementsin sphalerite-Mn, Ga, and In-whose combined compositional variations are particularly informative concerning the relative distances of samples to the feeder fault. The application of the resultant sphalerite proximitor to another structurally controlled MVT deposit effectively traced fluid flow paths and identified the relative distances of samples to the fluid influx center. Consequently, our study highlights the potential of sphalerite trace element chemistry, together with C-O isotopes, to serve as a novel exploration tool in MVT deposits. However, our results also demonstrate that the accurate petrologic identification of paragenetic mineral generations will generally be essential for reliably vectoring toward fluid influx centers.

Scheelite is one of the main ore minerals in tungsten deposits, and its geochemical features can be used to examine and constrain tungsten mineralization. The Yangla deposit is one of the most important Cupolymetallic skarn-porphyry deposits in the "Sanjiang" polymetallic metallogenic domain, Southwest China, hosting 150 Mt of Cu ores with economic concentrations of Pb, Zn, and Sb. The newly discovered tungsten mineralization in the Yangla deposit remains poorly understood. Hence, in order to ascertain the timing of tungsten mineralization, investigate its genetic relationship with magmatism and ore genesis, and elucidate the source, nature, and evolution of the ore-forming fluids, we performed a combined study of geochronology, in-situ trace elements, fluid inclusions, H-O isotopes, and in-situ Sr isotopic compositions of scheelite. In-situ U-Pb dating of scheelite showed that the timing of tungsten mineralization was 30 Ma. This mineralization age is significantly later than the published Cu mineralization age (-230 Ma), skarn (-231 Ma), and granitoid emplacement age (-230 Ma) in the Yangla ore district. Insitu trace element analyses revealed that scheelite is depleted in Mo, Mn, and Ta and slight enriched in Sr, Y, REEs, and Au. It is also characterized by HREE-depleted chondrite-normalized patterns with strongly positive Eu anomalies. Our data reveal that 3Ca2+ = (2REE)3++hCa (site vacancy) is the main substitution mechanism that controls REEs in scheelite. The low concentrations of Mo, negative Ce anomalies, and positive Eu anomalies of scheelite indicate a reduced condition. Preliminary REEs features indicate that the genesis of scheelite may be related to vein-type W (Au) deposits. The homogenization temperatures for fluid inclusions present a strongly decreasing trend (328 to 173 celcius), indicate that cooling is the predominant mechanism for the formation of scheelite. The 8D and 818Ofluid values from fluid inclusions of scheelite vary broadly from -161.70 %. to -133.30 %. and from 6.32 %. to 9.80 %., respectively, indicating a mixture of magmatic and meteoric water, with possible involvement of magma degassing and fluid-rock interaction. The initial 87Sr/86Sr ratios of scheelites (0.71931- 0.72117) are significantly higher than those of the granodiorite (0.71149 - 0.71990) and basalt (0.70562 - 0.70995) in the Yangla ore district, indicating that the Oligocene magmatism and Devonian marble with radiogenic Sr isotopic compositions contributed to tungsten mineralization. The fluid-rock interaction between the ore-forming fluids derived from the concealed granitoids and the Devonian wall rocks may play an important role in tungsten mineralization and provide significant Ca for scheelite precipitation. Thus, the tungsten mineralization should be associated with Oligocene magmatism, ruling out the genetic relationship with Late Triassic magmatism and being significantly different from the skarn-porphyry Cu-PbZn mineralization at Yangla. (c) 2023 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Unraveling the precise mineralization age is vital to understand the geodynamic setting and ore-forming mechanism of the sediment-hosted Pb-Zn deposit; this has long been a challenge. The Sichuan-Yunnan-Guizhou (SYG) triangle in the southwestern margin of the Yangtze Block is a globally recognized carbonate-hosted Pb-Zn metallogenic province and also an essential part of the South China low-temperature metallogenic domain. This region has > 30 million tons (Mt) Zn and Pb resources and shows the enrichment of dispersed metals, such as Ga, Ge, Cd, Se, and Tl. During the past 2 decades, abundant data on mineralization ages of Pb-Zn deposits within the SYG triangle have been documented based on various radioisotopic dating methods, resulting in significant progress in understanding the geodynamic background and ore formation of Pb-Zn deposits hosted in sedimentary rocks at SYG triangle. This paper provides a comprehensive summary of the geochronological results and Pb-Sr isotopic data regarding Pb-Zn deposits in the SYG triangle, which identified two distinct Pb-Zn mineralization periods influencing the dynamic processes associated with the expansion and closure of the Paleo-Tethys Ocean in the western margin of the Yangtze Block. The predominant phase of Pb-Zn mineralization at SYG triangle spanned from the Middle Triassic to Early Jurassic (226–191 Ma), which was intensely correlated with the large-scale basin fluid transport triggered by the closure of the Paleo-Tethys Ocean and Indosinian orogeny. The secondary Pb-Zn mineralization phase occurred during the Late Devonian to Late Carboniferous and was controlled by extensional structures associated with the expansion of the Paleo-Tethys Ocean. Further investigation is necessary to clarify the occurrence and potential factors involved in the Pb-Zn mineralization events during the Late Devonian to Late Carboniferous.

Many gold and antimony deposits in the Yunnan-Guizhou-Guangxi region in SW China are characterized with co-occurrence and symbiotic differentiation of Ao and Sb.However,the metallogenic relationship between Au and Sb and the difference between ore-forming processes of Au and Sb need to be further investigated.Fluorite,a common gangue mineral widely occurred in hydrothermal deposits,has been extensively studied to reveal the formation process of ore deposit.The Qinglong antimony deposit and the Nibao gold deposit in the Youjiang basin,with their matching mineralization ages and wallrock alteration characteristics,are selected as ideal objects for investigating the symbiotic differentiation of gold and antimony mineralization.Therefore,in this paper,we have carried out the in situ LA-ICP-MS trace element study of fluorites from the Qinglong antimony deposit and the Nibao gold deposit,in order to reveal the difference between their respective gold and antimony mineralization processes.Mineralogical and cathodoluminescence(CL)studies of fluorites reveal that three different stages of Sb-mineralization related fluorites in the Qinglong antimony deposit have been identified.Specifically,the first-stage fluorites have right-declined REE patterns with LREE-enriched and HREE-depleted characteristics.The second-stage fluorites are characterized by the MREE enrichment.The third-stage precipitated fluorites generally inherited the characteristics of REE distribution patterns of the second-stage fluorites though the third-stage fluorites have relatively low ∑REE contents.In general,the ∑REE values of fluorites are gredually decreased from the first-stage fluorites,second-stage fluorite to the third-stage fluorites.All fluorites have negative Ce anomalies.There are fluorites of two precipitation stages associated with the gold mineralization in the Nibao gold deposit.The first-stage fluorites have right-declined REE patterns,whilst the second-stage fluorites are characterized with MREE-enriched REE patterns.Their REE patterns are generally similar to those of fluorites in the Qinglong antimony deposit.Diagrams of Y/Ho,La/Ho,Tb/Ca,and Tb/La ratios for fluorites at different stages reveal that there are different genetic characteristics between fluorites of the early-ore-stage and those of the late-ore-stage.Especially,the early-ore-stage fluorite is of the dominant hydrothermal fluid filling genesis,while the late-ore-stage fluorite was formed in close association with the water-rock reaction which resulted in the input of a significant portion of host rock components into the late-stage ore-forming fluid,and the gradual increase of pH values and the decrease of total REE contents of the ore-forming fluids from the early-to late-stage.The comprehensive analysis suggested that the antimony mineralization in the Youjiang Basin is associated with the acidic ore-forming fluid which caused the dissolution of carbonate wallrock through the intensive water-rock reaction and thereby resulted in the formation of a significant of fluorite.Moreover,the increase of pH values and the decreaseof temperatures of the evolved ore-forming fluids could be contributed to the extensive precipitation of stibnite in the antimony deposit.Alternatively,the ore-forming fluids of gold deposits are characterized with weakly acidic to neutral nature.They caused the limited decarbonation of carbonate wallrocks and then resulted in the formation of a little fluorite and a large amount of dolomite,which is conducive to the formation of a large amount of Au-bearing pyrite.Based on the statistic analysis of REE data of stibnite and associated ore-related gangue minerals in antimony deposits in the Youjiang Basin,it is believed that the MREE enrichment characteristics for REE patterns of gangue minerals could be resulted from the LREE super-enrichment of a large amount of hydrothermal stibnite of antimony deposits.

Germanium (Ge)is a strategic and critical mineral resource,and an important raw material for many high.tech fields. Germanium is mainly produced as a by.product of hydrothermal base metal deposits such as Zn,Pb and Cu,as well as coal deposits. The Banbianjie Zn deposit (7. 70Mt ores,with an average Zn grade of 5. 1%),which has recently made significant breakthroughs in mineral exploration,is accompanied by ultra large.scale metal Ge (> 900t @ 110 x 10(-6)). However,the mechanism of Ge super. enrichment is unclear. In this study,we used LA.ICPMS to conduct sphalerite in.situ trace elements and mapping analyses,aiming to elucidate the occurrence and substitution of Ge and other dispersed elements. The results reveal that high concentrations (average > 100 x 10(-6))trace elements in sphalerite from the Banbianjie deposit is characterized by Fe,Pb,Ge and Cd,relatively high concentrations (average 100 x10(-6) - 10 x10(-) (6))trace elements are Mn,Ga,Sn and Tl,and the low concentrations (average value < 10 x10(-6))trace elements are Ag,Cu,In and Sb. Compared with other types of Pb.Zn deposits,The sphalerite from Banbianjie shows exceptional Ge enrichment (274 x10 - 6 similar to 1938 x10(-6),average 1055 x10(-6)). LA-ICPMS time.resolved depth profile and micro.area mapping analysis demonstrate that Ge occurs in sphalerite in an isomorphic or nanoparticle manner. Trace element molar correlation diagrams suggest that Ge substitutes Zn predominantly by Ge4+ + Pb2+ <-> 3Zn(2+),followed by nGe(4+) + Mn2+ <-> (2n + 1)Zn2+ and nGe(4+) + 2Tl(3+)<-> (2n + 3)Zn2+. Based on comprehensive analysis,it is believed that the Ge in the Banbianjie deposit may have originated from a relatively Ge rich Precambrian basements;Organic basin fluids play an important role in the transport of Ge;The symbiotic differentiation of rare and dispersed elements such as Ge and Cd restricts the ultimate supernormal enrichment of Ge. Therefore,the supernormal enrichment of Ge in the Banbianjie deposit is the result of the complex process of "source,transport,and accumulation"and the coupling of multiple factors

AbstractMetal stable isotopes (e.g., Zn, Cd, and Cu) have been used to track metal sources in different types of hydrothermal systems. However, metal isotopic variations in sulphides could be triggered by various factors such as mineral precipitation and fluid mixing. Thus, tracking the metal sources of hydrothermal systems is still a big challenge for metal isotopes. In this study, we investigated the Cd isotopic systematics of sphalerite from the Nayongzhi Zn–Pb deposit, which is a Mississippi Valley‐type (MVT) deposit in the Sichuan–Yunnan–Guizhou mineralization province (SYGMP). We reinterpreted the published S isotope data for the SYGMP and found that the large S isotopic variations were controlled by Rayleigh fractionation between sulphide and reduced S. As such, a model that involves mixing of a metal‐rich fluid with a reduced S pool formed by thermochemical sulfate reduction (TSR) can explain the ore formation in the Nayongzhi deposit. Based on this model, no Cd isotopic fractionation was observed due to its low solubility in fluids during mixing, and thus the Cd isotopic variations of sphalerite were inherited from the source rocks. The large range of Zn/Cd ratios and uniform Cd isotopic compositions of the sulphides are similar to those of igneous rocks but different from those of sedimentary rocks, indicating that Zn and Cd were derived mainly from basement rocks (e.g., migmatite, gneiss, and granulite). Our results reaffirm that metal stable isotopes, particularly Cd isotope compositions of sphalerite, are powerful geochemical tracers for investigating the formation mechanisms of ore deposits.

Unraveling the time-space evolution of Mississippi Valley-type (MVT) hydrothermal systems is critically important for understanding ore genesis and exploration. We studied a complete mineral system from conduit-filling to tail-end facies in the world-class Sichuan−Yunnan−Guizhou triangle, South China, via field geology, mineralogy, fluid inclusions, and in situ sulfide S-Pb isotopes to propose an integrated model for the evolution of MVT hydrothermal systems. Geological mapping shows that the mineralization transitions from breccia pipe to stratabound style: high-grade ores occur mainly as open-space infill associated with F12 fault (fluid conduit), while low-grade evaporite-related replacement ores developed distal from the fault. The δ34S value in hydrothermal sulfides shows a wide range (+3.6‰ to +27.9‰), with significant intragrain variation (up to +12.8‰), which suggests a mixture of 34S-rich sulfur produced by thermochemical sulfate reduction of evaporite within the ore host and 32S-rich sedimentary/diagenetic pyrite. In situ sulfide Pb ratios decrease away from the F12 fault, which indicates that metals were sourced from different degrees of mixing between the Proterozoic metamorphic basement and wall rocks. Fluid-inclusion microthermometric data identify two distinct fluids: a hotter (>155 °C), more saline (>18 wt% NaCl equivalent), and metal-rich fluid with a cooler (<90 °C), low-salinity (<4 wt% NaCl equivalent), and reduced sulfur-rich fluid. The mixing of two fluids was responsible for precipitating the high-grade ores near the F12 fault, and the acid-producing (H+) process created new space for stratabound ore distal to the fault. This study highlights that fluid mixing is critical for efficient sulfide accumulation, and the metal zoning pattern provides guidelines for exploration.

Multistage mineralization overprinting is important for the formation of giant hydrothermal gold deposits. The Youjiang basin in SW China has undergone at least three major deformation phases in the Mesozoic, but their relationship with the large-scale gold accumulation in the region remains enigmatic. Here, we study the large Nibao gold deposit (reserve > 70 t Au) in the northern part of the basin, which has both fault-controlled and stratabound orebodies. We identified a pre-ore stage and syn-ore stage including four tectono-hydrothermal (T-H) substages (i.e., T-H stage 1, 2, 3 and 4) for the local mineralization at Nibao. The pre-ore stage is dominated by coarse-grained pyrite coexisting with TiO2 polymorphs in the Middle-Late Permian basaltic rocks. The T-H substage 1 is characterized in that the sedimentary pyrites are brecciated in bedding-parallel faults. Fluorination and silicification occur in the T-H substage 2, which is re-brecciated at the T-H substage 3 forming the highest gold grade ore in high-angle thrust fault. The T-H substage 4 presents as fault reactivation within minor calcite and pyrite deposition. Mineralogy and in-situ trace element analyses reveal that mineral dissolution and reprecipitation (incl. dolomite, auriferous pyrite and TiO2 polymorphs) is ubiquitous during the multistage tectono-hydrothermal process, and the continuous alteration overprinting may have promoted gold accumulation. This replacement process of different generations of auriferous pyrite is also recorded by their inherited sulfur isotopes, giving a narrow delta S-34 (-3.1 to + 2.1 parts per thousand) range. Anatase is the main accessory phase of TiO2 polymorphs, as identified with LA-ICP-MS trace element and laser Raman spectroscopic analyses. Moreover, the anatase can been divided into two types (type-I and II) based on their texture, alteration and chemistry. The type-I anatase commonly occurring in the stratabound ore is characterized by higher Zr (mean 1,730 ppm), V (mean 1,412 ppm), and Cr (mean 110 ppm) contents than type-II that coexists with zoned pyrite in the fault-controlled ore (mean 26 ppm, 187 ppm, and 38 ppm, respectively). Additionally, W (mean 636 ppm) and Mg (10,021 ppm) in type-II are much higher than type-I ones (mean 135 ppm W and 476 Mg). These features show that the sedimentary-stage Zr-V-Cr-rich type-I anatase was dissolved via fluid metasomatism, and reprecipitated as the hydrothermal-stage W-Mg-rich and Zr-poor anatase, with gold gradually enriched. Besides, the anatase phase of TiO2 polymorphs also indicates that the Nibao gold deposit was formed under low pressure-temperature condition. Overall, we propose that the Nibao is a Carlin-type gold deposit, dominated by multistage tectono-hydrothermal events.