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• Types and temporal-spatial distribution of W and Sn mineralization in South China are summarized based on over 130 major deposits. • Metallogenic models illustrating the combination of diverse mineralization styles or metal assemblages are proposed for W-Sn deposits in South China. • Fluid and melt inclusion compositions are tested as new index to evaluate W and Sn mineralization potential in granitic system. South China is one of the most important tungsten-tin metallogenic areas in the world. Based on the up-to-date geological and chronological data of more than 130 deposits of economic significance, this paper preliminarily summarized the main types and temporal-spatial distribution characteristics of the large-scale tungsten and tin mineralization related to granite in South China. The statistical results show that skarn and quartz-vein types are the most important tungsten metallogenic styles, while skarn and cassiterite-sulfide types are the most important tin metallogenic styles in South China. Tungsten and tin mineralization related to granite in South China are multi-aged, but the largest scale of mineralization is developed within the Yanshanian period. Tungsten mineralization, the majority of which represented by the Nanling and Ganbei metallogenic belts, mainly formed from the Late Jurassic to Early Cretaceous (160 ∼ 120 Ma), while the most important tin mineralization formed in the Late Cretaceous (110 ∼ 80 Ma, peaking at 90 ∼ 80 Ma) and Late Jurassic (160 ∼ 150 Ma) as represented by the Youjiang Basin and Nanling metallogenic belt, respectively. The combined occurrence of different mineralization styles or metal assemblages in individual deposit and sometimes within the same orefield is the most striking feature of granite-related tungsten-tin deposits in South China, and a comprehensive understanding of their patterns are of great significance to guide ore prospecting. To address this issue, this paper proposed several combined metallogenic models and prospecting directions for tungsten-tin mineralization in South China based on recent researches and exploration progresses from typical examples including the Yaogangxian, Chuankou, Maoping, Shizhuyuan, Dachang and Gejiu deposits or orefields. In addition, conventional petrological and mineralogical characteristics that differentiates tungsten and tin granites are summarized, and on this basis the chemical composition of both melt inclusion and early stage fluid inclusion from granitic magmatic-hydrothermal systems were tested as new index to evaluate the tungsten and tin mineralization potential of granitic system. [ABSTRACT FROM AUTHOR]

In recent years, many concealed skarn-type and porphyry-type deposits have been discovered in Chating area, which shows very good prospectivity to host hydrothermal deposits. In this paper, we carried out the 3D mineral prospectivity modeling for porphyry and skarn-type mineralization of the Chating area. During this study, implicit geological modeling and the "total litho-inversion" method were used to build the 3D geological models and optimize the 3D geological models, various 3D predictive maps were generated by multiple 3D methods according to the exploration model. Finally, we use a 3D convolutional neural network (3D CNN) model to integrate all of the 3D predictive maps and delineate the concealed targets. The results show that the high- prospective areas delineated based on the 3DMPM not only include the deposits which are used as training data, but also the deposits that have already been discovered in the study area. It means that the 3DMPM approach used in this paper has good prediction and generalization ability. Compared with the Logistic Regression model (LR), Support Vector Machines (SVM), and Radom Forest (RF) model, the 3D CNN model can efficiently capture the correlation between various deposit types and 3D predictive information, and has better commendable predictive capabilities. The results of this paper can not only provide some new highly prospective areas for further mineral exploration in Chating area but also can promote the research on 3DMPM with deep learning methods. [Display omitted] • 3D Convolutional Neural Network would provide a new and powerful tool for 3D mineral prospectivity modeling. • The "total litho-inversion" method is a viable tool for the optimization of the 3D geological models which can provide more reliable data for 3D mineral prospectivity modeling. • 3D mineral prospectivity modeling can effectively identify not only the known deposits (not training data), but also delineate several new favorable exploration areas within Chating area at depth. The Chating area is situated within the Middle-Lower Yangtze River Metallogenic Belt, China. Several concealed skarn and porphyry-type deposits have been discovered in this area, indicating high potential for hosting hydrothermal deposits. However, due to the complex geological structure, exploration risks significantly increase with increasing depth. To overcome this challenge, three-dimensional mineral prospectivity modeling (3DMPM) has begun to be widely applied for mapping the prospectivity of deep-seated and concealed mineralization. However, most previous studies on 3DMPM were based on shallow supervised machine learning models and dimensionality-reduced 3D predictive maps. Although these models have shown good results, they may lose spatial correlation within the 3D predictive maps and fail to explore nonlinear correlations between the 3D predictive maps and mineralization. Meanwhile, 3D geological models are the most important basis of the 3DMPM, however, in the past, few studies have incorporated the optimization of the 3D geological models into the process of 3DMPM. Therefore, this paper initially builds and optimizes 3D geological models through implicit 3D geological modeling and "total litho-inversion" approach. Subsequently, the 3D predictive maps are generated by employing various 3D methods, which are further integrated using a 3D convolutional neural network (3D CNN) model to identify highly prospective areas for mineralization. The results show that the highly prospective areas identified by the 3DMPM include not only the training data but also other mineral deposits that have previously been discovered within the study area. In addition, compared with the Logistic Regression model (LR), Support Vector Machines (SVM), and Radom Forest (RF), the 3D CNN performs better prediction capabilities due to its enhanced ability to capture the correlations between 3D predictive maps and multiple types of mineral deposits. It suggests that the 3DMPM based on the 3D CNN model has commendable predictive capabilities in identifying prospective mineralization areas, and some new highly prospective areas can be considered as priority areas for future exploration of concealed mineralization within the Chating Area. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Langwashan iron deposit in submarine volcanic rocks is a Fe-skarn deposit. • Magnetite properties indicate iron mineralization and hydrothermal processes. • Many submarine volcanic iron deposits are likely to be Fe-skarn deposits. Carboniferous submarine volcanic rocks hosting iron deposits are widely distributed in the Tianshan and Beishan orogenic belts. However, the genesis of these deposits remains unresolved, with contrasting magmatic and magmatic-hydrothermal models being proposed. The Langwashan iron deposit (83.18 Mt @ 37% Fe) is one of the largest iron deposits in the Beishan orogenic belt. In this paper, we present detailed textural and trace-elemental properties of magnetite from the Langwashan iron deposit to elucidate the genesis and evolution of iron mineralization hosted in Lower Carboniferous submarine volcanic rocks. The Langwashan iron deposit has various types of iron ore that are closely associated with skarn minerals, including garnet and epidote. Magnetite in these samples can be classified into two distinct types, early-stage mushketovite (Mag1) and late-stage granular magnetite (Mag2), both of which show oscillatory zoning, with low Ti (mean of 0.03–0.07 wt%) and V (mean of 0.03–0.04 wt%) contents, and variable Si contents (mean of 0.74–6.50 wt%). These textural and compositional data classify the Langwashan deposit as a typical Fe-skarn deposit. Results also reveal that iron oxides in the Langwashan deposit underwent a complex evolution comprising three episodes: (1) early-stage influx of low-oxygen-fugacity, calcium-rich hydrothermal fluids, causing the transformation of original hematite to mushketovite (Mag1-1) and the formation of scheelite inclusions; (2) subsequent dissolution–reprecipitation between high-temperature magmatic-hydrothermal fluids and Mag1-1, generating trace-element-rich mushketovite (Mag1-2) and the precipitation of trace-element-rich granular magnetite (Mag2-1) from magmatic-hydrothermal fluids; and (3) final multiple fluid metasomatism under the influence of trace-element-poor hydrothermal fluids, involving dissolution–reprecipitation that produced trace-element-deficient Mag1-3, Mag2-2, and Mag2-3. Results also highlight that the submarine volcanic iron deposits from both the Tianshan and the Beishan orogenic belts were probably formed in a similar geological setting, with similar timing of formation, mechanism of mineralization, and evolution, and they are likely Fe-skarn deposits. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nam Xe REE deposit is of hydrothermal origin. • Nam Xe REE deposit has two episodes of REE mineralization at 45–44 Ma and 35–31 Ma. • Two episodes of REE mineralization coincide with the main- and late-collisional periods of the India-Asia convergence, respectively. Carbonatite-related rare-earth element (REE) deposits are developed in large areas of southwestern China and northwestern Vietnam on the SW margin of the South China block. The ages of REE deposits and their host carbonatite-alkaline rocks in southwestern China have been tightly constrained in the 35–10 Ma interval, but those in northwestern Vietnam remain poorly understood. In this paper, we present new Th–Pb dating results to constrain the timing of mineralization of the Nam Xe REE deposit in northwestern Vietnam, and to reveal its possible relationship to the well-studied REE deposits in southwestern China. The Nam Xe deposit consists of three types of REE ores: Type 1, fine-grained disseminated ores; Type 2, coarse-grained, taxitic ores; and Type 3, REE veinlets. The mineral assemblages and their close relations to hydrothermal alteration, combined with the trace element patterns of the ore minerals, indicate a hydrothermal origin for all the three ore types. Laser ablation-inductively coupled plasma-mass spectrometry Th–Pb dating of monazite yielded weighted-mean Th–Pb ages of 45–44 Ma for type 1 ores and 35–32 Ma for type 2 and 3 varieties, whereas the LA-ICPMS dating of bastnäsite has ages of 35–31 Ma for types 2 and 3, revealing two REE mineralization events at 45–44 and 35–31 Ma in the Nam Xe deposit. The age of type 1 ores overlaps the main-collision period of India-Asia collisional orogeny (65–41 Ma) which confirms carbonatite-related REE mineralization could form in the main-collisional geological setting. The ages of types 2 and 3 ores are consistent with those of the Mianning–Dechang REE metallogenic belt in southwestern China that formed under a late-collision extensional setting (40–26 Ma). Combined with existing geochronological data, results presented here suggest that the Nam Xe REE deposit formed both in the main- and late-collisional settings and represents the southern extension of the Mianning–Dechang REE metallogenic belt. [ABSTRACT FROM AUTHOR]

[Display omitted] • The genesis of the Fenghuangshan gold deposit is considered to be magmatic-hydrothermal. • The Fenghuangshan gold deposit is related to the Paleo-Pacific plate subduction. • The study area is highly prospective for deep-seated gold mineralization. The Jidong area is a vital gold province in North China, including plenty of metamorphic rock-hosted gold deposits. Whether ore-forming fluids are magmatic or metamorphic remains controversial. The genesis for gold mineralization in this gold province is ambiguous. The Fenghuangshan gold deposit lies on the eastern fragment of the Jidong gold province. In this paper, we present a detailed study on ore geology, fluid inclusions, and stable isotopes for the deposit to illustrate the characteristics of ore-forming fluids and ore genesis. The deposit occurs as gold-bearing quartz vein and disseminated- and veinlet-type mineralization. The main orebody named 7# is hosted in migmatitic granite, controlled by NE trending secondary fracture system. Four hydrothermal mineralization stages were identified, including: (Ⅰ) white quartz, (II) pyrite-quartz, (III) quartz-polymetallic sulfide, and (IV) calcite-chlorite-quartz. The Stage II and III belong to main gold mineralization stage. Fluid inclusions from different stages show that a lowering trend of fluid inclusion homogenization temperature was observed. They ranged from 222 °C to 407 °C (early-stage), 144 °C to 375 °C (main-stage), and 86 °C to 174 °C (late-stage), respectively. The salinities of the ore-forming fluids were typically low, ranging from 0.83 to 15.47 wt% NaCl equivalent. On the basis of Laser Raman analysis and fluid inclusion microthermometry, the ore-forming fluids belonged to a low- to moderate-temperature, low-salinity H 2 O-NaCl-CO 2 system. Fluid immiscibility gave rise to rapid gold deposition. The early-stage δD and δ18O H2O values from quartzs ranged from –96.4‰ to –92.5‰ and from 1.74‰ to 2.44‰, whereas main-stage fluids had δ18O H2O values of –4.10‰ to –3.50‰ and δD values of –91.5‰ to –89.5‰. The early- and main-stage sulfide δ34S values varied from –2.0‰ to + 2.2‰, with average values of + 0.4‰. H-O-S-isotope data indicated that the primary ore-forming fluids were magmatic water mixing meteoric water during mineralization, and ore-forming materials were derived from a homogeneous magmatic source. Ore geology, fluid inclusions, and stable isotopes illustrate that the Fenghuangshan gold deposit is a low- to moderate-temperature magmatic-hydrothermal gold deposit. Future deep-seated and surrounding gold exploration should center on this area. [ABSTRACT FROM AUTHOR]

[Display omitted] • In the case of a small number of known deposits and mineral occurrences, the prospecting prediction model based on the Siamese network can extract effective features without relying on prior knowledge to realize supervised prospecting prediction. • On the basis of sliding window data enhancement, this paper generates paired sample data sets by randomly combining deposit samples and non-deposit samples, which can further enhance the data and improve the generalization ability and prediction accuracy of the model to a certain extent. • Compared with the prediction results of the weight of evidence method and the convolutional neural network, the prediction results of the Siamese network are better, and 7 new gold prospecting areas have been discovered in Zhangjiakou, Hebei Province, China. Supervised neural networks constitute an important research area for the intelligent prediction of locations for prospecting mineral deposits. Accurate training of a supervised neural network requires many training samples, something that is often difficult to obtain. This paper reports the use of geological, geochemical, and geophysical data by a Siamese network to overcome the problem of insufficient training samples, and implements a supervised deep learning prospecting prediction method based on the Siamese network. Intelligent prediction for gold deposits prospecting is carried out for the Chongli mineral concentrate area in Zhangjiakou, Hebei Province, China, and compared with the weight of evidence method and convolutional neural network model. The results show that:(a) the performance of the Siamese network model is no less than that of the convolutional neural network (CNN) model and better than that of the weight of evidence (WOE) method; (b) the gold prospective areas differentiated by the established models are strongly consistent with geological and metallogenic characteristics in the study area. This study suggests Siamese network model as an effective mineral prospectivity modeling tool. This method is also suitable for prospecting prediction using geoscience data in other areas. [ABSTRACT FROM AUTHOR]

• Two mineralization stages are recognized in Yaojialing zinc skarn deposit. Cobalt and tellurium minerals deposited in the early sulfide stage, selenium minerals deposited in the late sulfide stage. • The distribution of critical minerals resources in Yaojialing deposit varies spatially and temporally. Late stage sphalerite is more enrich Cd but exceptionally low in Co and Se than in the early stage. • Early stage pyrite is more enriched Co and Se, Se is also enriched in chalcopyrite, Te only occurs in tellurium minerals. • Temperature is the main factor affecting the distribution of these critical minerals resources. Critical minerals resources are widely used in emerging industries, and their mineralization characteristics and metallogenic regularity are of high importance. Skarn deposits are one of the important sources of critical minerals resources. Yaojialing deposit is a typical large skarn zinc polymetallic deposit in Tongling district of the Middle and Lower Yangtze River metallogenic belt. The ore bodies are mainly lenticular and veined occurrence along the proximal skarn zone and structural or lithologic contacts, respectively. We recognize five hydrothermal stages in the deposit: skarn stage, oxide stage, early sulfide stage, late sulfide stage and carbonate stage. The early and late sulfide stages are the main ore-forming stages. In addition to the production of zinc, gold and copper, the deposit also contains critical element resources such as cadmium, cobalt, selenium, and tellurium. Taking the Yaojialing deposit as an example, this paper shows the occurrence and distribution of critical minerals resources in a typical skarn deposit by using scanning electron microscope, TESCAN integrated mineral analyzer (TIMA), and sulfide LA-ICP MS analysis. Although there are no cadmium minerals in Yaojialing deposit, cadmium can incorporated in the sphalerite lattice, and sphalerite in veins has elevated cadmium content (average 5478.78 ppm). Tellurium content in various sulfides is very low, and it does not enter into the sulfide lattice. It mainly forms tellurobismuthite, hessite and tetradymite, which occur in Cu-Zn ore formed in the early sulfide stage, there are 227 tetradymite grains in a single rock section. Selenium occurs as naumannite in vein ore in the distal of the deposit; selenium can also incorporated the lattice of chalcopyrite and sphalerite, and the selenium content is elevated in sphalerite formed in the early sulfide stage (average 226.80 ppm). The cobalt mineral glaucodot is only found in skarn ore; cobalt easily incorporated the lattice of pyrite and sphalerite, and pyrite and sphalerite formed in the early sulfide stage are enriched in cobalt (average 1962.18 ppm). The characteristics of trace elements in pyrite and sphalerite show that temperature is the main factor affecting the distribution of critical minerals resources, high temperature is conducive to the enrichment of cobalt, selenium and tellurium, while low temperature is conducive to the enrichment of cadmium. Cadmium, cobalt, selenium, and tellurium have high content in specific parts of the deposit, which makes them potentially amenable to recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four paragenetic stages are recognized at the Devonian Huodehong sulfide deposit. • The sedimentary pyrite might act as a geochemical barrier for locating hydrothermal Pb-Zn mineralization. • The wide variation of δ34S values of sulfides is ascribed to multiple sulfur sources. The Devonian sedimentary rocks in South China host numerous sulfide deposits (e.g. the Siding and Beishan Pb-Zn sulfide deposits, and the Yingde iron sulfide deposits) that are distinctly characterized by a wide variation of δ34S values in sulfides (−28.7‰ to +42.8‰). Such signature, however, has not been investigated in depth and thus the metallogeny of these deposits remain poorly understood. This paper investigated the Huodehong deposit hosted by sedimentary rocks of the Middle Devonian in the western Yangtze Block, South China. A complex paragenesis has been defined: I) micro-grained pyrite (Py1) associated with organic materials; II) radial and crustiform pyrite (Py2) and marcasite (Mc1) aggregates; III) subhedral-anhedral pyrite (Py3), microcrystal colloform sphalerite (Sp1), and dendritic galena; and IV) coarse-grained euhedral sphalerite (Sp2) occurred as veinlets. The mineralogical evidence shows that the Py1 occurred as syn -sedimentary pyritic stromatolites, which is overprinted by cavity-filling hydrothermal Py2, Py3, Sp1, and Sp2. In situ S isotopes show that the δ34S values of Py1-Py3 and Sp1 range from –22.8‰ to −10.8‰. Such highly depleted heavy sulfur isotopes indicate that the reduced sulfur was mainly derived from bacterially reduced seawater sulfate in an open system. The Sp1 has similar δ34S values to its reworking Py1, implying that part of reduced sulfur was sourced from sedimentary pyrite. Such sedimentary pyrite might act as a geochemical barrier in accelerating sulfate reduction via the hydrolysis of Fe2+ resulting an increase in the H+ concentration and the formation of HSO 4 −. In addition, the Sp2 has slightly depleted heavy sulfur isotopes (δ34S = −9.3‰ to −1.1‰), implying the late input of heavy sulfur isotopes component. Hence, the highly heterogeneous sulfur isotopes at Huodehong likely resulted from bacterial sulfate reduction coupled with reworking sedimentary pyrite, and subordinate incorporation of 34S-rich sulfur. The reduced sulfur of the Huodehong deposit has multiple sources (i.e. sedimentary pyrite and sulfate-bearing evaporites), and the ore formation has experienced the epigenetic hydrothermal mineralization with mixture of metals from the metamorphic basement rocks. The outcomes will have a great implication for understanding the origin and exploration of the Devonian sulfide deposits in South China. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mineralized fluids are characterized by weakly acidic, reduced, and low temperature. • W/R interaction and CO 2 degassing caused the precipitation of carbonate minerals. • Mixing of metals and BSR-originated S2− resulted in the sulfide precipitation. • The origin of the Banbanjie deposit is similar to that of the MVT deposits. This paper investigates the origin of the newly discovered Devonian carbonate-hosted Banbianjie Ge-Zn deposit in South China. This deposit is rich in Ge (>900 t @ 110 ppm Ge) and contains 7.7 Mt of sulfide ores at a mean grade of 5.1 wt% Zn. The mineralization is stratabound or veined and is structurally controlled by the E-W trending Huangsi fault. Sulfide ores are dominated by sphalerite and dolomite with subsidiary pyrite, marcasite, and calcite, and minor galena. The mineralization forms massive, veined, brecciated, and disseminated structures and the hydrothermal minerals present in the deposit have colloform, fibrous, granular, and acicular textures. The hydrothermal dolomite has positive Ce (δCe = 1.13–1.20) and negative Eu (δEu = 0.43–0.68) anomalies that are indicative of formation in a weakly acidic, reduced, and low-temperature environment. The δ13C PDB and δ18O SMOW values of the dolomite range from −0.97‰ to −0.24‰ and +13.89‰ to +21.84‰, respectively, indicating that the dissolution of carbonate wall rocks was involved in the formation of hydrothermal dolomite. Theoretical C-O isotopic calculations further suggest that the hydrothermal dolomite formed as a result of water/rock (W/R) interaction and CO 2 degassing. The δ34S values of the sulfides (−11.23‰ to −4.95‰) are markedly lower than those of the Devonian seawater sulfate and sulfate from evaporates in the Devonian strata (+21.9‰ to +25.9‰), suggesting that the reduced sulfur was derived from evaporates within the ore-hosting sedimentary rocks by bacterial sulfate reduction (BSR). The Banbianjie sulfides have an upper crustal Pb isotopic affinity, as demonstrated by their 206Pb/204Pb (18.335–18.343), 207Pb/204Pb (15.725–15.735), and 208Pb/204Pb (38.288–38.326) ratios, suggesting the metals were derived from metamorphosed basement rocks. These data suggest that: i) the Banbianjie deposit formed as a result of a combination of weakly acidic, reduced, and epigenetic low temperature mineralized fluids, trap structures, and favorable lithologies; ii) W/R interaction and CO 2 degassing caused the precipitation of hydrothermal dolomite, whereas mixing of metals and S2− was the main formation mechanism of the sulfides; and iii) the Banbianjie Ge-Zn deposit is a typical Mississippi Valley-type (MVT) deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • One high-εHf and two low-εHf domains in the Argun massif indicate the Neoproterozoic and Mesoproterozoic to Neoproterozoic crustal zones, respectively. • Transition of magma source from the juvenile crust to ancient crust from south to north during the Mesozoic. • The composition and structure of the crust control the metal associations, deposit types, and localization of ore deposits. The Argun massif is an important micro-continent in the eastern Central Asian Orogenic Belt and hosts a wide variety of Mesozoic hydrothermal Cu(–Mo), Pb–Zn–Ag, and Au deposits such as Wunugetushan Cu(-Mo) and Jiawula Pb–Zn–Ag deposits. In this paper, we integrate geological and zircon U–Pb–Hf isotopic data from Mesozoic Argun igneous rocks to elucidate the crustal architecture, and any spatial–temporal and genetic links with the regional metallogeny. Our results indicate that the porphyry Cu–Mo deposits in the massif were mainly developed in the zones with high-εHf(t) values and Neoproterozoic T DM c ages, representing juvenile lower crustal components. The epithermal Pb–Zn–Ag deposits were mostly developed in zones with variable εHf(t) and Mesoproterozoic to Neoproterozoic T DM c values, representing magma source with reworked ancient or juvenile lower crustal components. In contrast, the major mesothermal and epithermal Au deposits are associated with magmatic rocks emplaced in low-εHf(t) and high-T DM c domains, representing reworked Mesoproterozoic ancient crustal components. [ABSTRACT FROM AUTHOR]

• Pyrite hosting visible gold is low in Au and As. • Gold-bearing pyrite was subject to brittle rather than ductile deformation. • Visible gold in pyrite did not result from remobilization of lattice gold. • Visible gold in pyrite was introduced by evolved ore fluids after host pyrite. Pyrite (FeS 2) is one of the most common hosts for gold (Au) in different types of gold deposits, including visible and invisible gold. For visible gold in pyrite, it remains unclear whether it resulted from remobilization of invisible gold in the gold-hosting pyrite or from external input. This paper reports a case study from the Zhaoxian gold deposit, which is the deep extension of the well-known Jiaojia gold deposit, in the Jiaodong gold province. The texture and composition of Au-bearing pyrite from the Zhaoxian deposit were studied with petrographic, Electron Back-Scattered Diffraction (EBSD) mapping, and Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry (LA-ICP-MS) methods. Four types of pyrite (Py-1 to Py-4), corresponding to four generations of veins, i.e., the pre-ore V1, syn -ore V2 and V3, and post-ore V4, were distinguished. Py-2 is volumetrically the most abundant among the four, and is the main host of visible gold. LA-ICP-MS analyses of pyrite indicate that gold contents in most analysis points are below the detection limit, with measured Au contents ranging from 0.02 to 0.17 ppm (median 0.09 ppm) in Py-1, and 0.03 to 2.45 ppm (median 0.07 ppm) in Py-2. EBSD analyses indicate that pyrite (Py-2) display brittle deformation features including microstructures, lattice dislocation, and grain boundary displacement. Visible gold in Py-2 occurs in micro-fractures, cavities, and grain boundaries. The generally low contents of Au in pyrite, including Py-2, and the brittle deformation features, suggest that the visible gold grains did not result from remobilization of invisible gold from pyrite. Rather, the majority of gold was introduced by fluids after the formation of the gold-hosting pyrite. These fluids were derived from the same sources as those precipitating the gold-hosting pyrite, but were more evolved and enriched in Au. Circulation of these auriferous ore-forming fluids in microfractures of pyrite and interstitial space resulted in precipitation of visible gold. [ABSTRACT FROM AUTHOR]