The Dayishan ore field, a significant Sn-polymetallic production area in South China, hosts a variety of tin deposits, including the Lvzi'ao Cu (-Sn) deposit, Zhimashan Sn-Cu deposit, Baishaziling Sn deposit, and Maozaishan Sn (-W) deposit. However, the genetic relationships between the Sn-Cu-W deposits and the Dayishan granitic complexes remain unclear. Here, we present the U-Pb ages from zircon, cassiterite, apatite, and scheelite obtained from different granites and ore types within the Dayishan ore field. The Sn metallogenic age was determined through cassiterite U-Pb geochronology, yielding ages between 150 Ma and 153 Ma, while the Cu metallogenic age was identified through apatite U-Pb dating at 153.5 Ma. These ages are consistent with the zircon U-Pb age of Dayishan granitic complexes (152.37 Ma). In contrast, scheelite U-Pb geochronology provided an age of 133.58 Ma, characterizing the W metallogenic age. Geochemical variations in apatite from diverse deposits reveal systematic trends in F, Cl, and S contents and Cl/F ratios and FREE + Y concentration. The range of Y/Ho ratios in apatite suggests that the ore-forming material source of Sn and Cu deposits originated from a shared magmatic-hydrothermal fluids in Dayishan granitic complexes. Similarly, variations in cassiterite Zr/Hf and Nb/Ta ratios, along with a increasing oxygen fugacity, indicate a progressive decline in fluid temperature as the mineralization evolved. In contrast, the W deposit appear to a distinct magmatic-hydrothermal system associated with a deep concealed pluton formed during the Cretaceous. This suggests that the Sn-Cu mineralization in the Dayishan ore field was derived from a shared magmatic-hydrothermal system, which underwent significant during fluid evolution. Multidisciplinary evidence supports the existence of two stages of superimposed composite mineralization in Dayishan ore field, early Sn-Cu metallogenic stage was followed by a later W metallogenic stage, with the latter superimposed on the former, which together form multiple types of Sn-Cu(W) deposits in Dayishan granitic complexes.

The Longshan deposit, located in the Xiangzhong metallogenic Province (XZMP), South China, is a large-scale SbAu deposit with substantial reserves (Sb: 143,000t, Au: 15.5 t). Despite its economic importance, the genesis of the deposit remains enigmatic and the subject of ongoing debate, primarily due to uncertainties regarding its mineralization age and its link with regional granitic magmatism. Mineralogical investigations have revealed the occurrence of apatite within the Sb ore veins, where it is closely associated with scheelite and stibnite. Apatite displays elevated REE contents, MREE-enriched patterns with positive Eu anomalies, which suggest its hydrothermal origin. Consequently, the apatite U-Pb age provides a robust constraint on the timing of Sb mineralization at the Longshan Sb-Au deposit. Cathodoluminescence (CL) images reveal that apatite typically exhibits a core-rim texture, comprising an early-stage core apatite (Ap1) and late-stage rim apatite (Ap2). U-Pb dating of Ap1 proved unsuccessful due to high common Pb concentrations, while LA-ICP-MS U-Pb dating of Ap2 yielded a Tera-Wasserburg lower intercept age of 159 +/- 13 Ma, which likely reflects the timing of late-stage mineralization at the Longshan deposit. The new data indicate that the Longshan deposit experienced the superposition of Late Jurassic mineralization, in addition to the previously documented Late Triassic mineralization event. In-situ sulfur isotope measurements of stibnite and pyrite from different mineralization periods revealed delta 34S values ranging from -2.37 %o to + 6.04 %o, which indicate that sulfur in the ore-forming fluids at Longshan likely originated predominantly from buried magmas. A weak upward trend in delta 34S values from deeper to shallower levels indicates the minor contributions from host rock sulfur. Integrated with early chronological data and mineralogical observations, these findings suggest that the Longshan is a magmatic-hydrothermal Sb-Au system formed through the superposition of Late Triassic and Late Jurassic mineralization events.

The Late Cretaceous Jiepailing granitoids, located at the central Nanling Range in South China, are closely associated with significant Sn‐Li‐Be‐F polymetallic metallogeny. The Jiepailing granitoids mainly consist of granitic porphyry and zinnwaldite granite. The two granitoids have an A‐type affinity, showing elevated Rb/Sr ratios and significant depletions in Ba, Sr and P. Integrated zircon and monazite U‐Pb dating results suggest that granitic porphyry and zinnwaldite granite were emplaced at ~89 Ma and ~94 Ma, respectively. The low Ce 4+ /Ce 3+ ratios of the Jiepailing granitoids, together with significant negative Eu anomalies of the zircons, indicate that their formation occurred under conditions of reduced oxygen fugacity. Through the analysis of zircon Hf‐O and whole‐rock Nd isotopes, it has been determined that both stages of the Jiepailing granitoids originated in the lower‐middle Mesoproterozoic crustal basement [ ε Nd ( t ) = –5.33 to –4.96, t C DM ( Nd ) = 1289–1234 Ma, ε Hf ( t ) = –4.13 to +2.22, t C DM ( Hf ) = 1418–1015 Ma and δ 18 O Zrc = 6.33‰–7.72‰], with the involvement of mantle‐derived materials. Both granitic porphyry and zinnwaldite granite exhibit elevated concentrations of fluorine (F), with the positive correlation between F and Sn emphasizing the crucial role of high F sources in tin mineralization. Drawing upon the study of the Late Cretaceous magma systems in southern Hunan and through comparison with the mineralized granites observed in coastal regions during the Late Cretaceous, a genetic model for the mineralized granites in the Nanling region is developed. When the Paleo‐Pacific Plate retreated to the coastal region, the continental crust in southern China underwent extensional thinning and asthenospheric upwelling due to gravitational collapse. Such processes resulted in the partial melting of the middle–lower crustal metamorphic sedimentary basement and the subsequent formation of F‐rich granitic magmas, related to tin mineralization.

Multiple phases of tectonic-magmatic-mineralization events occurred in the southern Hunan during the Mesozoic era.Previous studies mainly focused on the Middle Triassic and Jurassic events.A growing number of Late Cretaceous magmatic events have been identified in recent years.The Linwu Basin is a typical Late Cretaceous intracontinental rift basin in which the rhyolitic ignimbrite is in parallel contact with the Cretaceous Nanqiang Formation strata.The ignimbrite provides important evidence for studying the Late Cretaceous magmatic activity in the inland of South China.In this paper,we conducted systematic studies of petrology,zircon U-Pb geochronology,and Hf isotope composition analyses of ignimbrite in the Nanqiang Formation.The results show that the ignimbrite has weighted average zircon U-Pb age of(99.9±0.8)Ma(MSWD=1.5),implying that the ignimbrite was formed in Late Cretaceous.The zircon U-Pb age of ignimbrite is consistent with formation ages of mafic volcanic rocks and Late Cretaceous granites in the region.The εHf(t)values of its zircons range from-4.54 to-10.46,with two-stage Hf model ages(tCDM)varying from 1457 Ma to 1825 Ma,implying that it was mainly sourced from the Mesoproterozoic lower crust,with possible minor added mantle materials.Zircons of ignimbrite samples have crystallization temperatures(tTi)ranging from 810 ℃ to 1018 ℃ and fO2 values varying from-12.63 to-9.57,suggesting that the ignimbrite samples have relatively high crystallization temperatures and relatively low oxygen fugacities comparing with those of the Middle-Late Jurassic granites in the region.Based on the comprehensive analysis,it is believed that the Late Cretaceous magmatic activity occurred within the Linwu Basin,though there are mainly uplifted Middle-Late Jurassic granites in the surrounding areas of the Linwu Basin.It provides indication for studying the tectonic background and magma activity of the region.

Pegmatites are commonly associated with or strongly influenced by the crystallization of magmatic volatile phases (MVP) as ascending magmas undergo differentiation. The mechanism of fractional crystallization, liquid immiscibility, and water-rock interactions that influence the rare metals concentration in pegmatites are still unclear. We analyzed the mineralogy (incl. monazite, garnet, zircon, and muscovite) from pegmatites to unravel the timing and magmatic-hydrothermal processes for the giant Renli-Chuanziyuan pegmatite Li-Nb-Ta mineralization in the Mufushan region (South China). Five types of pegmatites have been identified at Mufushan, i.e., those containing mainly orthoclase (O-pegmatite), microcline (M-pegmatite), albite-orthoclase (AO-pegmatite), microcline-albite (MA-pegmatite), and spodumene-albite (S-pegmatite). Monazites from the Renli high-Th Li-mica pegmatite exhibit magmatic affinity. The similar to 140 Ma age of monazite U-Pb suggests a temporal relationship between the Li-rich pegmatite and its muscovite granite host. Garnet from these pegmatites is magmatic and belongs to the almandine-spessartite series, and contains feldspar and apatite inclusions. Continuous fractional crystallization likely controlled the pegmatite development, as the garnet spessartite content increases with distance from the Mufushan batholith. Garnet in the spodumene-albite pegmatites has very low REE content, and it represents a late stage of crystallization related to magmatic-hydrothermal fluids. Compositional variation in muscovite from all of the pegmatites is negligible. The K/Rb ratio (a proxy for the degree of fractionation) increases gradually from the O- to S-pegmatite, whilst the muscovite F content correlates positively with the degree of magma fractionation. The transformation of muscovite to lepidolite in pegmatites can occu r through magmatic-hydrothermal crystallization or metasomatism. Zircon in pegmatites generally occurs as metasomatic remnants, with uneven zoning shown in cathodoluminescence (CL) images. Hydrothermal zircon U-Pb ages are concentrated in the 140-134 Ma range, consistent with the garnet leucogranite ages. This suggests that pegamtites and the garnet leucogranite were formed in the same magmatic-hydrothermal activity. The accumulated MVP and incompatible elements may have migrated from deeper, more crystal-rich zones under mediu m degree of fractionation. The MVP may contain abundant dissolved melt components as single-phase hydrous silicate liquids, forming typical quartz-/feldspar-dominated pegmatite and the diversity of rare-metal deposits.

The Baiyunxian ore field, a large tungsten ore filed in the Nanling Metallogenic Belt of South China, hosts a variety of tungsten deposits such as the Dapu (quartz wolframite vein type), Chashanjiao (skarn type), Toutianmen (greisen type), and Dashan (quartz scheelite vein type). However, precise mineralization ages of these deposits remain poorly constrained and this has long vexed a better understanding of genetic relationships between diverse W mineralization types and the spatially associated Jiufeng granitic complexes. Here, we report firsthand zircon U-Pb, monazite U-Pb, garnet U-Pb, cassiterite U-Pb, and molybdenite Re-Os ages of different granites and ores from the Baiyunxian ore field. The Jiufeng granitic complexes consists of phase I biotite granite (P1), phase II two-mica granite (P2), and phase III granitic dikes (P3, including greisen W ore). Zircons from P1 granite define a concordant U-Pb age of 166.0 +/- 0.9 Ma (MSWD = 1.1). Monazites from P2 granite yielded a Tera-Wasserburg lower intercept age of 159.2 +/- 0.7 Ma (MSWD = 0.45). In addition, zircons and monazites from P3 granite in the Toutianmen deposit yield a concordant U-Pb age of 154.7 +/- 1.3 Ma (MSWD = 1.3) and a Tera-Wasserburg lower intercept age of 156.6 +/- 1.9 Ma (MSWD = 0.14), respectively, suggestive of multi-stage emplacement processes of the Jiufeng complexes. Ten molybdenite samples from the Dapu deposit generate an isochron age of 156.0 +/- 3.0 Ma (MSWD = 0.93). In situ garnet and cassiterite LA-ICP-MS U-Pb dating results of the Chashanjiao skarn deposit yield lower Tera-Wasserburg intercept ages of 155.3 +/- 1.2 Ma (MSWD = 1.6) and 153.4 +/- 3.7 Ma (MSWD = 1.3), respectively. These dating results indicate that different W mineralization events in the Baiyunxian ore field intensively occurred in the Late Jurassic (similar to 159-153 Ma). Despite a close spatial relationship between various W orebodies and P1 granite, the geochronological results demonstrate that extensive W metallogeny in the Baiyunxian ore filed likely occurred later than P1 granite and contemporaneous with P2-3 granites. In addition, scheelites from the four deposits have similar REE patterns that are characterized by weak MREE enrichment, despite few exceptions being found in scheelites from the Dashan and Chashanjiao deposits. This suggests that the diverse W metallogeny in the Baiyunxian ore field were derived from the same magmatic hydrothermal system and changed as the ore-forming fluid evolved. Multidisciplinary evidence indicates that the Late Jurassic highly evolved P2-3 granites of the Jiufeng complexes were crucial to W mineralization in the Baiyunxian ore field and the lithology of wall rocks exerted first-order control of W mineralization types.

[Objective]The Tongshanling deposit in the western Nanling metallogenic belt of Hunan Province is a skarn Cu polymetallic deposit related to Ⅰ-type granodiorite.Recently,a thick stratiform W-Mo skarn ore body has been found in the limestone of the Qiziqiao Formation far from the granodiorite intrusion.Its geological characteris-tics,mineral assemblages and genetic types are different from those of the ore bodies in the contact zone of the in-trusion.[Methods]In this study,timing and genesis of the Tongshanling stratiform are analysed,through field in-vestigation,microscopic identification,in situ U-Pb dating of garnet,and LA-ICP-MS trace element analysis of scheelite.[Results]The following four stages of mineralization are identified:garnet skarn,epidote and chlorite skarn,quartz sulfide and quartz calcite.The U-Pb concordant age of garnet is(160.4±4.2)Ma(MSWD=0.79),is significantly later than that of the granodiorite(～167 Ma)and similar to that of the granite porphyry(～161 Ma).The total rare earth element(ΣREE)distribution pattern of the garnet core is light rare earth element(LREE)enrichment and heavy rare earth element(HREE)flat and is similar to the whole-rock ΣREE model of granite porphyry.The ΣREE distribution pattern of garnet rims is LREE-depleted and is different from that of garnet in contact zone skarns.Scheelite associated with epidote can be divided into three stages.ΣREE modes of the three stages are all LREE enrichment and HREE depletion,but the ΣREE content decreases significantly from the first stage(Sch1-a,332× 10-6-353× 10-6)to the second stage(Sch1-b,144×10-6-301 × 10-6)and the third stage(Sch1-c,4.05×10-6-31.8×10-6).Scheelite associated with chlorite(Sch2)shows LREE enrichment and HREE depletion,and their ΣREE content is 51.2× 10-6-139×10-6.W-Mo mineralization is mainly concentrated in the retrograde stage.The Sch1-b and Sch2 stages have higher oxygen fugacities are the main stage of W mineralization,while the other stages(Sch1-a and Sch1-c)with lower oxygen fugacities are the main stage of Mo mineralization.Comprehensive analysis reveals that the stratiform skarn and contact zone skarn in the Tongshanling and Weijia de-posits are different metallogenic systems.The stratiform skarn may be related to the granite porphyry with a relative-ly high degree of fractionation.[Conclusion]More attention should be given to the late granite porphyry in deep within and at the edge of the Tongshanling deposit.

The Tongshanling Cu-Pb-Zn deposit, situated within the Qin-Hang intra-continental porphyry-skarn metallogenic belt in South China, presents a valuable case study of intrusion-related ore systems. This deposit is characterized by skarn mineralization closely associated with subsequent quartz-vein sulfide mineralization. While considerable research has been devoted to understanding the origin and evolution of the intrusions and mineralization processes, limited attention has been given to elucidating the relationship between the skarn and quartz-vein mineralization, along with the physicochemical conditions governing their formation. Here, we conducted a comprehensive mineralogical and isotopic investigation of sulfides, and a thorough analysis of fluid inclusion assemblages. We aimed to discern disparities in the sources of ore-forming materials, formation temperature, sulfide fugacity, and precipitation-alteration mechanisms of hydrothermal fluids for these two distinct orebodies. Although same sulfide species including arsenopyrite, pyrite, chalcopyrite, and sphalerite, some silicate minerals such as garnet, chlorite, and epidote are exclusive to the skarn orebodies and absent in the quartz veins. The homogeneous temperatures of fluid inclusions in the skarn orebody, ranging from the early to late stages of evolution, decrease from similar to 310 to similar to 290 degrees C. Simultaneously, salinity varies from 5.5 to 3.1 wt% NaCl eqv. In the quartz vein mineral body, the temperature reduction is more pronounced, decreasing from similar to 270 to 186 degrees C, with salinity ranging from 3.6 to 1.4 wt% NaCl eqv. Sphalerite geothermometer indicates that peak hydrothermal fluid temperature in the skarn orebodies (similar to 300-340 degrees C) was relatively higher than that in the quartz-vein orebodies (<300 C). Nevertheless, temperatures in both hydrothermal fluid systems declined as mineral precipitation proceeded, corresponding to a decrease in sulfur fugacity. The final stage of sphalerite represents the lowest temperature, salinity and sulfur fugacity with associated quartz displaying the lowest salinity across the entire hydrothermal fluid spectrum at the Tongshanling deposit, suggestive of meteoric water incorporation. This study delves into the multifaceted history of mineralization at the Tongshanling deposit, providing a fresh perspective on the origin and evolutionary relationships of Cu-polymetallic deposits associated with intrusions, particularly those involving multiple stages of mineralization in skarns and quartz veins, contributing to a better understanding of similar deposits worldwide.

Garnet is a primary mineral in skarn deposits and plays a significant role in recording copious mineralization and metallogenic information. This study systematically investigates the geochemistry and geochronology of garnet and zircon in the Dafang Au-Pb-Zn-Ag deposit, which represents prominent gold mineralization in southern Hunan, China. Garnet samples with distinct zoning patterns and compositional variations were identified using various analytical techniques, including Backscattered Electron（BSE） imaging, Cathodoluminescence（CL） response, textural characterization, and analysis of rare-earth elements（REE）, major contents, and trace element compositions. The garnet was dated U-Pb dating, which yielded a lower intercept age of 161.06 ± 1.93 Ma. This age is older than the underlying granodiorite porphyry, which has a concordia age of 155.13 ± 0.95 Ma determined by zircon U-Pb dating. These results suggest that the gold mineralization may be related to the concealed granite. Two groups of garnet changed from depleted Al garnet to enriched Al garnet, and the rare earth element（REE） patterns of these groups were converted from light REE（LREE）-enriched and heavy REE（HREE）-depleted with positive europium（Eu） anomalies to medium REE（MREE）-enriched from core to rim zoning. The different REE patterns of garnet in various zones may be attributed to changes in the fluid environment and late superposition alteration. The development of distal skarn in the southern Hunan could be a significant indicator for identifying gold mineralization.

Granitoids are the most important component of continental crust, yet there has been debate regarding the classification and petrogenesis of peraluminous I- and S-type. As a result of fractional crystallizing and crustal contamination, whole-rock geochemistry sometimes fails to accurately reflect the type of primitive magma. Recent studies, however, suggest that the accessory mineral compositions can shed light on the character and petrogenesis of their primitive magma. In this contribution, we use apatite and zircon as indicators to explore the distinctions between peraluminous I- and S-type granitoids, and the petrogenesis of typical peraluminous I-type granitoids (Baoshan granitoids). Apatite trace elements indicate that their initial magma was mafic I-type, even though whole-rock compositions appear to be the hybrids of I- and S-type granitoids. Additionally, we propose that the assimilation and fractional crystallization processes are responsible for the decoupling between the compositions of whole-rock and accessory minerals. The compositions and isotopes of zircon can also reveal the components of the magma source region. The zircons epsilon(Hf)(t) values of the Baoshan granodiorite porphyry and lamprophyre have comparable (Hf)(t) values (-9.5 to -6.2 and -12.5 to -6.2, respectively). Based on the spotting of similar to 900 Ma inherited zircons and enriched epsilon(Hf)(t) values, we propose that the granitoids were formed by the partial melting of felsic Paleoproterozoic crust and a little of Neoproterozoic mafic juvenile crust, while lamprophyre was generated by the cooling of upwelling magma from the same source region as granitoids. According to the apatite trace element ratios (Sr/Th vs. La/Sm), the source region of the Baoshan intrusion is identified to been metasomatized by slab-derived fluid. Our data, in conjunction with previous studies, suggest that the paleo-Pacific slab roll-back triggered the high-temperature asthenosphere mantle upwelling, while the assimilation and fractional crystallization occurring along with the rising melts in route to the surface.

The Shizhuyuan oxidized skarn-greisen W-Sn deposit (South China) has widely developed scheelite in the prograde skarn stage, retrograde skarn stage, oxide stage, sulfide-quartz vein stage, greisen stage, and quartz -calcite-fluorite vein stage that are related to the reduced A-Type Qianlishan granite. In this contribution, we used trace elements, oxygen isotopic compositions, and U-Pb isotopes for tracing the W metallogenic processes in skarn and greisen, and the genesis of the Shizhuyuan W-Sn deposit. The total rare-earth element (FREE) contents of scheelite grains from prograde and retrograde skarn stages to oxide stage show a decreasing frac-tionation trend (means from 1647 to 181 ppm) and the increasing trend in sulfide-quartz vein stage and greisen (mean = 428 ppm and 2074 ppm) indicate multi-stage fluid activities. Scheelites formed in skarn show HREE depletion REE patterns (LaN/YbN values means from 159 to 1.40) which results from paragenetic mineral pre-cipitation (e.g., garnet and diopside), and negative or small positive Eu anomaly. In contrast, scheelite grains from the greisen stage have a flat REE pattern and a pronounced negative Eu anomaly identical to those of the Qianlishan granite that mirror the magmatic-hydrothermal fluid. The MoO3 contents in scheelite decrease from the prograde and retrograde skarn stages through the oxide stage to the sulfide-quartz vein stage (mean = 27.4 wt%, 1.97 wt%, 0.51 wt%, and 0.12 wt%). However a slight rise in MoO3 contents was observed in scheelite grains from the greisen to the latest-stage quartz-calcite-fluorite vein stage (mean = 0.28 wt% and 0.52 wt%, respectively). It is suggested to be the result of a change in fluid fO2 conditions and periodic transition from oxidizing to reducing metallogenic environment. The mean 818OH2O values of the ore-forming fluid in the different mineralization stages as calculated by 818Oscheelite are 7.98 %o (prograde skarn), 6.20 %o (retrograde skarn), 4.96 %o (proximal greisen), 2.83 %o (distal greisen), and 3.29 %o (quartz-calcite-fluorite vein). Scheelite grains formed in the retrograde skarn stage yielded a U-Pb isochron age of 164.4 +/- 7.6 Ma, which is within the uncertainty of the emplacement age of the Qian-lishan granite. Although scheelite grains formed in different stages have different trace elements and oxygen isotope compositions, they are all associated with the Qianlishan granite. We assume that the giant skarn-greisen W-Sn deposit has mainly resulted from multistage fluid activities derived from reduced intrusions and long-term fluid-rock interactions with thick marbleized limestone in an oxidizing setting.

The grossular–andradite garnet is an ideal mineral for indicating the formation age of skarn, which also pretends to constrain skarn processes because of its higher REE (rare earth elements) content. The Tongshanling deposit is a medium-sized reduced skarn Cu–W–Pb–Zn deposit associated with a highly evolved I-type granodiorite intrusion in the Nanling metallogenic belt, South China. Different mineral assemblages, microscopic characteristics, and BSE images distinguish two kinds of garnets in the prograde and retrograde skarn stages. The garnet grains from the prograde skarn stage have a U–Pb isochron age of 165.4 ± 3.8 Ma (MSWD = 0.7) and that from the retrograde skarn stage have a U–Pb isochron age of 159.5 ± 1.7 Ma (MSWD = 1.8), implying that the thermal metamorphism and hydrothermal metasomatism mainly occurred in the middle Upper Jurassic. The total amount of rare earth elements (∑REE+Y) in the garnet gradually decreased and the REE patterns shifted from enriched HREE with Eu negative anomaly to HREE-depleted with Eu positive anomaly. The decreasing U content and increasing Eu anomaly in the retrograde skarn stage indicate a redox environment change from oxidation to reduction. However, garnet from different elevations within the same stage (+90 m, +5 m, −35 m, −200 m, and −400 m) exhibit similar REE patterns, despite weak cooling and significant depressurization processes confirmed by fluid inclusion microthermography. As a result, the REE content and patterns are dominated by the REE species of parent fluids, which are changed over time by symbiotic REE-enriched mineral precipitation and the redox environment, while being slightly affected by the fluid pressure. Grossular garnets, rich in U and REEs, and found in reduced skarn deposits, can constrain chronology and reveal the spatio-temporal zonal characteristics.

Field and microscopic structural investigations, trace element and C–O isotopic analyses of calcite, zircon U−Pb dating of dikes, and wide-field electromagnetic sounding are conjointly conducted in the middle part of the Qin−Hang metallogenic belt to decipher the spatial−temporal evolution and genetic relationship of structure−magma- mineralization. The data reveal four deformation events: D1 is a W-to-E-thrusting event; D2 is characterized by SE-to-NW thrusting; D3 is a NW−SE-oriented extensional event accompanied by large-scale magma intrusion and W–Sn and Cu–Pb–Zn mineralization; D4 is a dextral strike−slip event after mineralization. Two stages of calcite are identified during D3 and Stage II calcite is characterized by LREE-enriched REE patterns, with low δ18OSMOW (from 9.78‰ to 12.3‰), identical to those of calcite in the deposits, confirming that they are closely related to mineralization. Wide-field electromagnetic profiles further display the geometric characteristics of structures, granitic plutons, and orebodies from shallow to deep (~5 km) level. It is believed that some giant concealed W−Sn and Cu−Pb−Zn orebodies are developed in the contact zones between plutons and limestone at a depth of 1.5−4 km. It is reasonable to suggest that this method is feasible for the study on the deep exploration of W−Sn and Cu−Pb−Zn polymetallic deposits.

Pyrite geochemistry is crucial for the discrimination of the types of ore-forming fluids in gold deposits, such as metamorphic–hydrothermal fluids and magmatic–hydrothermal fluids. With the assistance of supervised machine learning algorithms, this application can be leveraged maximally. Here, laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) geochemical data for 4683 pyrite samples worldwide were collected to train seven classification models. The top three algorithms, including Random Forest (RF), Support Vector Machines (SVM), and Multilayer Perceptron (MLP), were used to build classifiers to predict the type of pyrite. The established classifiers were applied to new geochemical data for pyrite samples collected from the Jinkeng and Huanggou gold deposits in the Xuefengshan Orogen (XFSO). The findings suggest that the classifiers are capable of accurately distinguishing between two main types of ore-forming fluids, with good predictive outcomes. This performance surpasses that of traditional, two-dimensional diagram-based methods. The classifiers determined that the geochemical constituents of pyrite from the Jinkeng and Huanggou originated from metamorphic–hydrothermal sources, consistent with geological and geochemical evidence. The results further reveal that the Jinkeng and Huanggou are classified mostly as orogenic gold deposit. This study proves that data-driven methods based on machine learning can provide compelling evidence for distinguishing between the types of ore-forming fluids, understanding deposit genesis, and providing prospecting ideas. Additionally, this research boosts confidence in the use of machine learning to geological classification challenges.

The strategic mineral W-Sn deposits in China are mainly concentrated in South China, and many rare metal mineralizations, such as Li, Rb, Be, Nb, Ta, etc., are often coproduced with them. However, the genetic relationship between them is unclear. Based on the analysis of research data related to granite-related rare metals and W-Sn deposits in South China, we believe that the two types of mineralization have a close spatio-temporal relationship at multiple scales, such as metallogenic belts, ore fields, deposits, and minerals. In addition, the ore-forming material source, mineralization process, and ore-controlling structures are similar, indicating that they may have derived from a same granitic mass and the mineralization usually have close genetic relationship with the high evolved granite. Therefore, the exploration and research data of W-Sn deposits in South China can be used to explore and study rare metal deposits.

湖南邓阜仙矿田是我国华南著名的钨锡多金属矿产地,随着多年的矿山开采,资源已逐渐枯竭,亟需新的找矿突破.近期在矿田西侧发现多处隐爆角砾岩,为钨锡成矿作用和找矿勘查打开了新窗口.本文对该隐爆角砾岩开展了系统地质调查、岩相学、岩石地球化学、锆石年代学与Lu-Hf同位素分析,研究表明:1)隐爆角砾岩筒主要沿茶陵?郴州?临武断裂发育,具有显著分带性,从中心到外围依次为长英质岩脉、隐爆角砾岩带、裂隙带,且存在多期热液活动与矿化;2)长英质岩脉锆石U-Pb加权年龄为(151.9±1.2)Ma,形成时代与矿田成矿高峰期一致;3)岩脉富集Rb、Th和U,亏损Sr、Ba、K和P等元素,具有高的分异指数(DI为94.77～97.11),其锆石?Hf(t)为?6.8～?0.8(均值为?4.7),TDM2为1253～1638 Ma,与矿田成矿花岗岩具有相似的微量元素和Lu-Hf同位素组成,指示二者应为同一岩浆源区.综合分析认为,矿田隐爆角砾岩与钨锡多金属成矿关系密切,尽管目前已发现的钨锡矿床均集中在矿田东部,但是西部同样有较大的钨锡找矿潜力,尤其是茶陵?郴州?临武断裂附近.隐爆角砾岩是寻找钨锡多金属矿床的有利找矿标志,应给予高度重视.

The Tongshanling ore field is one of the most representative W‒Sn‒Cu‒Pb‒Zn polymetallic deposits in the central-western Nanling Ore Belt, which developed multiple mineralization types, including Cu‒Pb‒Zn (Tongshanling), W‒Sn (Weijia), Pb‒Zn (Jiangyong), and Mo (Yulong) deposits. Here, we analyzed apatite from the Tongshanling granodiorite and the Weijia granite porphyry, integrating major and trace elements, U-Pb dating, and Nd isotopic analysis to compare the difference in geochronology, magma source, redox environment, and evolution between the Tongshanling and Weijia deposit. The U-Pb dating of the Tongshanling and Weijia apatite samples yield a lower intercept age of 166.2 ± 11.3 Ma (1σ, MSWD = 0.22) and 160.87 ± 8.92 Ma (1σ, MSWD = 0.44) on Tera-Wasserburg diagrams, respectively. The 147 Sm/ 144 Nd and 143 Nd/ 144 Nd ratios of the Tongshanling apatite samples are 0.136769‒0.182878 and 0.512159‒0.512246, respectively, with corresponding ε Nd (t = 166 Ma) ranging from −8.32 to −6.60, suggesting that the Tongshanling granodiorite was produced by partial melting of metaigneous rocks in the deep crust. The Tongshanling apatite shows a right-inclined REE pattern, while the Weijia apatite displays a “V” type REE pattern. The Tongshanling apatite shows higher Eu/Eu* values, and lower Mn and Ce/Ce* values than the Weijia apatite, indicating that the former formed from in high magmatic oxidation state while the latter formed in more reduced conditions. The granodiorite in the Tongshanling deposit is characterized by a lower degree of fractionation than the granite porphyry in the Weijia deposit, of which the Weijia apatite has lower Sr, Mg contents, and higher Y contents. The combination of Sr/Y and Eu/Eu* values in apatite samples indicates that both the Tongshanling granodiorite and Weijia porphyry granites are non-adakitic rocks. Furthermore, the high Cl contents of apatite suggest that the crust basement of the Tongshanling area was affected by the high Cl fluid derived from the Proterozoic oceanic subduction and remelted to form granite in the Mesozoic. In contrast, the Weijia apatite exhibits high F/Cl ratios, indicating that the Weijia granite porphyry formed from remelting of a sedimentary source. The Tongshanling granodiorite and Weijia granite porphyry with different degrees of fractionation, magma source, and halogens contents can be effectively distinguished by the geochemistry of apatite. The difference in trace elements (Sr, Y, Mg, and REE) and isotopes of apatite can be applied for the identification of different types of ore-bearing granites in the Nanling Range.

地球化学勘探找矿效果较好,但成本高、周期长;遥感地球化学利用遥感技术解决地球化学问题,遥感技术与地球化学方法相结合,可以降低找矿成本,提高效率.以新疆齐石滩金矿为研究区,将金矿成矿相关元素的化探数据与该区的WorldView-2遥感数据相结合进行遥感地球化学研究.采用多元线性回归(MLR)法建立各元素的反演模型,但反演结果精度不高,且异常位置和异常形态也存在一定的偏差,可能是混合像元致使含量与遥感影像呈非线性关系.因此,引入BP神经网络方法建模,反演精度明显提高,各元素反演异常与化探异常吻合很好,异常位置和异常形态更加精确.可见,BP神经网络方法更适合于遥感地球化学建模.

The Qin-Hang Metallogenic Belt (QHMB), an important metallogenic belt in South China, hosts Cu and W–Sn polymetallic deposits. The Tongshanling ore field in the QHMB is characterized by the coexistence of Cu- and W-bearing polymetallic deposits, which are related to granodiorite and granite porphyry. This study examined whole-rock geochemistry, geochronology, and Sr–Nd–Hf isotopes to determine the genetic relationship between diverse ore-related granitoids (i.e., granodiorite and granite porphyry) and Cu–W metallogeny in the Tongshanling ore field. Zircon LA-ICP-MS U–Pb dating shows that the granodiorite and granite porphyry in the Tongshanling ore field were emplaced at 163.7 ± 0.4 Ma to 154.7 ± 0.6 Ma and 161.1 ± 0.3 Ma, respectively. Geochemically, the granodiorites are classified as oxidized I-type, while the highly evolved granite porphyry is reduced A-type. The Lu–Hf isotopic composition of the granodiorites is characterized by εHf(t) values ranging from –10.49 to –4.99 (average = –7.17), with corresponding TDMC ages ranging from 1524 to 1877 Ma (average = 1682 Ma). In contrast, the granite porphyry has higher εHf(t) values (–3.60 to –1.58, average = –2.78) and younger TDMC (1310–1438 Ma, average = 1387 Ma). The εNd(t) values of granodiorite are −8.06 to −7.37 and the two-stage model ages (TDM2) are 1543–1598 Ma, while the granite porphyry has higher εNd(t) values (−3.0 to −3.4) and younger TDM2 ages (1195–1223 Ma). The results show that the granodiorite and granite porphyry were formed from partial melting of different Mesoproterozoic basement rocks under varying degrees of crust–mantle interaction. Granite porphyry underwent well-recorded fractional crystallization. Compared to the Cu-forming granodiorite, the W-forming granite porphyry has a higher differentiation index, higher crystallization temperatures of zircon (average = 708 °C versus 631 °C), and lower oxygen fugacity (median ΔFMQ = –2.21 versus –1.77).