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The remobilization, migration, precipitation, and enrichment of ore-forming elements are closely related to structures. Therefore, detailed regional and ore-field structural analyses are critical for determining the genesis of a mineral deposit. The Jiangnan Orogenic Belt (JOB) is an important gold polymetallic metallogenic belt in South China, which is characterized by multiple periods of gold mineralization in the Paleozoic and Mesozoic. However, the genesis of these gold polymetallic deposits is still not well understood due to a lack of systematic research on the regional geology, ore-controlling structures and metallogenic mechanism. In this study, a detailed structural survey at the surface and in the subsurface tunnels was conducted on the Woxi Au-Sb-W deposit, the genesis of which is relatively controversial among the gold polymetallic deposits in the JOB due to poor structural constraints. In addition, a wolframite U-Pb dating was carried out to further constrain the relationship between structures and mineralization. Based on the results of these studies, together with those from previous studies, it is proposed that the Woxi deposit and surrounding areas likely underwent six periods of regional deformation, which are constrained in time and geodynamic setting. Furthermore, we present a systematic discussion on the roles of ore-controlling structures in the transportation, distribution, and deposition of ore-forming elements and localization of orebodies. According to the wolframite dating results, structural analyses, and previous data, we propose that the Woxi Au-Sb-W deposit was formed in two stages during the Yanshanian: a W (wolframite)-Au mineralization stage at ca. 140 Ma and an Au-Sb-W (scheelite) mineralization stage at <130 Ma. These mineralizing events are interpreted to have a tight relationship with tectonic reactivation, and the ore-forming fluids were derived from deep sources, including those of magmatic or metamorphic origins. The Woxi deposit can therefore be classified as an "intracontinental reactivation-type", and the mineralization is related to lithospheric extension caused by plate retreat, retention, and delamination following the cessation of westward subduction of the Paleo-Pacific Plate beneath the East Asian continent. [ABSTRACT FROM AUTHOR]

The unconformity-related uranium (URU) deposits in the Proterozoic Athabasca Basin (Canada) represent the richest, and one of the most important, uranium endowments in the world. Most of the URU deposits are associated with pre-existing graphitic basement faults that were reactivated after the formation of the basin. These graphite-rich structures have been widely used as a vector for exploration, but the nature of the association of the URU deposits with graphitic basement faults has been debated for over four decades. Proposed roles of graphite include: (1) as a direct reducing agent to reduce U6+ to U4+ and precipitate uraninite; (2) as a precursor of hydrocarbons (mainly CH4) produced in situ or nearby and then used as a reducing agent for uraninite precipitation; (3) as a precursor of hydrocarbons produced at depth that were remobilized to the site of mineralization and acted as a reducing agent for uraninite precipitation; and (4) as a lubricant facilitating faulting and fluid flow that led to uranium mineralization. This paper uses the Phoenix uranium deposit in the southeastern Athabasca Basin as a case study to address these uncertainties. Petrographic studies indicate that there is no direct contact between graphite and uraninite at microscopic scales, and the content of graphite in the graphitic metapelite along the ore-controlling WS Shear Zone does not show a systematic change with the distance from the unconformity surface. Raman spectroscopic studies of graphite suggest that the degree of structural disorder of graphite, expressed by various parameters related to the D bands and G band ratios, does not change systematically with the distance from the unconformity surface either. The minor irregularities in these parameters near the unconformity are better explained by paleo-weathering related to the unconformity and/or diagenetic processes than by hydrothermal activity related to uranium mineralization. Based on these observations and interpretations, the role of graphite as an in situ reducing agent, either directly or as a provider of hydrocarbons, is discounted. It is proposed that hydrocarbons derived from graphite at depth, tapped by episodic reactivation or seismicity of the basement faults that was facilitated by graphite as a lubricant, were responsible for URU mineralization. [ABSTRACT FROM AUTHOR]

The Alastuo gold deposit, located in the Narati region of the Chinese West Tianshan, is a newly discovered gold deposit within the world-class Tianshan gold belt. The gold mineralization is hosted by an Early Carboniferous granodiorite intrusion and controlled structurally by subsidiary faults of the transcrustal North Narati Fault. The deposit consists of auriferous alteration assemblages and minor vein ores. Field relations and petrographic data suggest four stages of mineralization with gold precipitated coevally with quartz, chlorite, epidote, pyrite, and galena during the second and third stages that are characterized by tectonic transformation from ductile shearing to brittle deformation. The temperature range of gold precipitation is estimated to be 280–330 °C using chlorite geothermometry. Ten auriferous pyrite samples yielded a well-defined Re-Os isochron age of 325 ± 3 Ma and two sericite samples yielded plateau-like 40Ar/39Ar ages of 321.7 ± 3.0 Ma and 321.2 ± 2.8 Ma. These consistent ages suggest that the gold mineralization in the Narati region was emplaced in a transitional regime from subduction to continental collision between the Tarim block and Middle Tianshan terrane (325–310 Ma), rather than during the post-collisional stage as in most part of the Tianshan gold belt. Gold-bearing pyrite has an initial Osi value of 0.7 ± 0.1 and lead isotopes ratios of 17.897 to 18.723 for 206Pb/204Pb, 15.474 to 15.643 for 207Pb/204Pb, and 37.522 to 38.299 for 208Pb/204Pb, while samples of pyrite, galena, and sphalerite have 34SV-CDT of +1.9 to +7.8‰. The isotope data suggest that the sulfur and metals are most likely derived from mixed mantle and crustal sources including metamorphic devolatilization of subducted oceanic slab and overlying sedimentary rocks. The mineralization styles, structural controls, metal and sulfur sources, and the timing of gold mineralization with respect to the orogenic event all suggest that the Alastuo gold deposit represents an orogenic type deposit. This newly recognized Carboniferous orogenic gold mineralization event calls for a re-evaluation of the gold metallogeny in the Middle Tianshan. [ABSTRACT FROM AUTHOR]

Uranium (U) and iron (Fe) are generally considered to have contrasting aqueous geochemical behavior, with U dissolution being favored in oxidizing fluids as oxidized U (U6+) and Fe in reducing fluids as reduced Fe (Fe2+) species. However, high concentrations of both U and Fe have been reported for the ore fluids of uranium deposits, suggesting that the two elements can be co-transported in the same fluid. In this study, geochemical modeling, based on recent thermodynamic and experimental data for U and Fe species and fluid inclusion compositions from two types of hydrothermal U deposits (volcanic-related and unconformity-related), was conducted to investigate the nature and conditions of U Fe co-transportation. The results of the modeling indicate that high concentrations of U (>10, up to >100 ppm) and Fe (>1000 ppm) can be dissolved in acidic aqueous fluids (pH < ∼3.3) of moderate to high chlorinity (∼ 55 to 250 g/L Cl), for a wide range of log f O 2 above and below the magnetite-hematite (MH) buffer (from ∼ MH-5 to MH + 30), at temperatures from 150 to 250 °C. There are four different combinations of dominant dissolved U and Fe species depending on the pH and redox conditions: U6+ and Fe3+ species (UO 2 Cl 2 0 and FeCl 3 0) at relatively high f O 2 , U4+ and Fe2+ species (UCl 4 0 and FeCl 4 2−) at relatively low f O 2 , and U6+ and Fe2+ species (UO 2 Cl 2 0 and FeCl 4 2−) or U4+ and Fe3+ species (UCl 4 0 and FeCl 3 0) at intermediate f O 2 conditions. Because the most important U mineral in hydrothermal uranium deposits is uraninite (UO 2), in which U is present as U4+, a necessary condition for U mineralization is that U is either transported as U4+ species or, if transported as U6+ species, precipitation of uraninite is induced by a reducing agent. The recognition that U6+ and Fe2+ species can be co-transported in the same fluid indicates that uraninite can be precipitated without the need to invoke a reducing agent external to the ore fluid. The driver of uranium mineralization in this case is an increase in pH due to fluid-rock interaction that leads to the alteration of the rocks by clay minerals and associated coupled sorption-reduction. These findings provide for a more extensive range of conditions for U transport and deposition than previously imagined and require that interpretation of the conditions of uranium mineralization consider both oxygen fugacity and pH. This study underscores the potential for uranium deposits to occur in geological settings where reducing agents are either absent or insufficiently abundant to account for the observed mineralization, and the possibility for the transport of U in environments that might otherwise be considered unfavorable. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four types of fluid inclusions were identified in quartz-sulfide veins of Xiaokelehe. • The initial fluid was released by magmas and characterized by high-temperature, low salinity and density. • Fluid immiscibility and mixing of magmatic water with meteoric water control Cu-Mo mineralization. • The lower CO 2 contents in fluid is an important parameter to distinguish porphyry Cu from porphyry Mo deposits. The Xiaokelehe porphyry Cu-Mo deposit in the Great Xing'an Range contains six stages of quartz-sulfide veins (V1 to V6) including potassic (V1 to V4), chlorite-illite (V5) and phyllic (V6). Two to three types of quartz were identified within each stage, of which the V2Q1, V3Q1, V4Q2, V5Q1 and V6Q2 are spatially associated with sulfides. Three types of fluid inclusions were identified in these veins, i.e., type I aqueous inclusions homogenized to liquid, type II aqueous inclusions homogenized to vapor, and type III aqueous inclusions containing halite and homogenized to liquid. Type I and type II primary inclusions occur in all stages, and type III inclusions are developed in V2 to V4 veins. Microthermometric data show that the maximum formation temperatures and pressures of V2-V6 veins of type I inclusions are 353 to 437 °C and 19.0 to 27.6 MPa, 309 to 415 °C and 15.0 to 30.1 MPa, 330 to 365 °C and 16.7 to 27.6 MPa, 243 to 351 °C and 13.9 to 18.9 MPa and 255 to 347 °C and 13.9 to 17.8 MPa, respectively, which show a decreasing trend. Oxygen isotope data show that the δ18O H2O values of V2-V4 veins (5.3 to 10.4 ‰) are consistent with typical magmatic values, whilst the δ18O H2O values of V5-V6 veins (0.2 to 4.6 ‰) are much lower than those of the magmatic water, which is due to involvement of meteoric water. The fluid inclusion microthermometry and O isotope data suggest an evolving magmatic-hydrothermal system with decreasing temperatures, pressures from V2 to V4 veins (potassic stage) to V5 (chlorite-illite stage) and V6 veins (phyllic stage), and an increasing incorporation of meteoric water in V5 and V6. The Xiaokelehe deposit has lower CO 2 contents than the adjacent porphyry Mo deposits formed in the same post-collisional setting, which is mainly due to differences of mineralization depths and magma source. The formation of porphyry deposits with different Mo/Cu ratios highlights the diversity and complexity of the mineralizing systems in post-collisional settings, which has important implications for mineral exploration in such environments. [ABSTRACT FROM AUTHOR]

• Beaverlodge (Canada) and South China granite-related uranium deposits share many similarities. • Uranium mineralization in both areas are associated with red bed basins and mafic magmatism in an extensional setting. • Red bed basins served as reservoirs of oxidizing fluids, and elevated geothermal gradients facilitated fluid circulation. • Coupling of shallow (red bed basins) and deep (mantle-derived magmatism) processes is critical for uranium mineralization. Many uranium deposits are related to granitic rocks, but the mineralization ages are much younger, thus excluding a direct magmatic-hydrothermal link between the mineralization and the granites. Two such examples are the Proterozoic "vein-type" uranium deposits in the Beaverlodge district in Canada and the Mesozoic granite-related uranium deposits in South China. Both areas have been extensively studied, but the critical factors that control the mineralization remain unclear. The uranium mineralization in the Beaverlodge district occurs in quartz – carbonate ± albite veins and breccias developed within and near major deformation zones, and are mainly hosted by ca. 2.33 – 1.90 Ga granitic rocks and ca. 2.33 Ga Murmac Bay Group amphibolite. These rocks are unconformably overlain by the Martin Lake Basin, which was formed during a period of regional extension in the later stage of the Trans-Hudson orogeny and is filled with red beds. A ca. 1820 Ma mafic magmatic event is manifested as volcanic rocks occurring within the Martin Lake Basin and as dikes crosscutting the basement rocks and lower Martin Group strata. Uraninite U-Pb and Pb-Pb ages range from ca. 2290 Ma to <300 Ma, with a peak overlapping the mafic magmatism. The granite-related uranium mineralization in South China occurs mainly as quartz – carbonate ± fluorite veins and as disseminations in the host rocks adjacent to fracture zones. The deposits are hosted by, or occur adjacent to, granitic rocks, and are spatially close to Cretaceous – Tertiary red bed basins that were formed in a Basin-and-Range like tectonic setting related to roll back of the Pacific plate. These red bed basins contain intervals of bimodal volcanic rocks and are crosscut by coeval mafic dikes. Uraninite U-Pb ages dominantly range from 100 to 50 Ma, which is much younger than the host granites (>145 Ma) and broadly contemporaneous with development of the red bed basins and mafic magmatism. Comparison of the two study areas reveals striking similarities in geologic attributes related to uranium mineralization, specifically, the development of large volumes of granitic rocks that are relatively enriched in uranium, and the development of red bed basins with accompanying coeval mafic magmatism in extensional tectonic settings. It is proposed that oxidizing basinal fluids from the red bed basins circulated into the underlying fertile granitic rocks along high-permeability structural zones, acquired uranium in the path through fluid-rock interaction, and precipitated the uranium where they encountered reducing agents. Elevated geothermal gradients associated with the mantle-derived magmatism greatly enhanced the mineralization by facilitating the uranium extraction and transport processes. Thus, it is the coupling of shallow (red bed basin and oxidizing basinal fluid development) and deep-seated (mantle-derived magmatism and related thermal activity) processes, together with the pre-enrichment of uranium in basement rocks (particularly granitic rocks) and pre-existing deformation zones, that controlled the formation of the granite-related uranium deposits in both Beaverlodge and South China, and perhaps elsewhere in the world with similar geologic setting. [ABSTRACT FROM AUTHOR]

The Wangu gold deposit in northeastern Hunan, South China, is one of many structurally controlled gold deposits in the Jiangnan Orogen. The host rocks (slates of the Lengjiaxi Group) are of Neoproterozoic age, but the area is characterized by a number of Late Jurassic–Cretaceous granites and NE-trending faults. The timing of mineralization, tectonic setting and ore genesis of this deposit and many similar deposits in the Jiangnan Orogen are not well understood. The orebodies in the Wangu deposit include quartz veins and altered slates and breccias, and are controlled by WNW-trending faults. The principal ore minerals are arsenopyrite and pyrite, and the major gangue minerals are quartz and calcite. Alteration is developed around the auriferous veins, including silicification, pyritic, arsenopyritic and carbonate alterations. Field work and thin section observations indicate that the hydrothermal processes related to the Wangu gold mineralization can be divided into five stages: 1) quartz, 2) scheelite–quartz, 3) arsenopyrite–pyrite–quartz, 4) poly-sulfides–quartz, and, 5) quartz–calcite. The Lianyunshan S-type granite, which is in an emplacement contact with the NE-trending Changsha-Pingjiang fracture zone, has a zircon LA-ICPMS U–Pb age of 142 ± 2 Ma. The Dayan gold occurrence in the Changsha-Pingjiang fracture zone, which shares similar mineral assemblages with the Wangu deposit, is crosscut by a silicified rock that contains muscovite with a ca. 130 Ma 40 Ar– 39 Ar age. The gold mineralization age of the Wangu deposit is thus confined between 142 Ma and 130 Ma. This age of mineralization suggests that the deposit was formed simultaneously with or subsequently to the development of NE-trending extensional faults, the emplacement of Late Jurassic–Cretaceous granites and the formation of Cretaceous basins filled with red-bed clastic rocks in northeastern Hunan, which forms part of the Basin and Range-like province in South China. EMPA analysis shows that the average As content in arsenopyrite is 28.7 atom %, and the mineralization temperature of the arsenopyrite–pyrite–quartz stage is estimated to be 245 ± 20 °C from arsenopyrite thermometry. The high but variable Au/As molar ratios (>0.02) of pyrite suggest that there are nanoparticles of native Au in the sulfides. An integration of S–Pb–H–O–He–Ar isotope systematics suggests that the ore fluids are mainly metamorphic fluids originated from host rocks, possibly driven by hydraulic potential gradient created by reactivation of the WNW-trending faults initially formed in Paleozoic, with possible involvement of magmatic and mantle components channeled through regional fault networks. The Wangu gold deposit shares many geological and geochemical similarities as well as differences with typical orogenic, epithermal and Carlin-type gold deposits, and may be better classified as an “intracontinental reactivation” type as proposed for many other gold deposits in the Jiangnan Orogen. [ABSTRACT FROM AUTHOR]

Abstract: The Tulasu basin is an important epithermal Au mineralization district in western Tianshan in northwestern China. Geochemical and geochronological studies of the volcanic host rocks (the Dahalajunshan Formation) and associated intrusive rocks, particularly the enrichment of large-ion lithophile elements and depletion of high field strength elements, suggest that the Tulasu basin was located in a magmatic-arc setting from Late-Devonian to Early-Carboniferous, associated with the southward subduction of the North Tianshan Ocean beneath the Kazakhstan–Yili plate. Geologic and geochemical characteristics of the Au Cu–polymetallic deposits in the Tulasu basin suggest that the mineralization is related to the Late-Devonian to Early-Carboniferous arc magmatism, and is mainly of epithermal nature, including both the adularia–sericite type (Axi, Tawuerbieke and Tabei) and alunite–kaolinite or acid–sulfate type (Jingxi–Yelmend and Tieliekesayi). However, some evidence of porphyry-type mineralization has also been found, including the presence of mineralized porphyry enclaves in volcanic rocks hosting the Tawuerbieke Au prospect, and the development of porphyry-style Cu mineralization overprinted by vein-type mineralization at Kexiaxi. Considering the magmatic-arc setting that is favorable for both epithermal and porphyry types of mineralization, and the development of such mineralization systems in other parts of western Tianshan and the Altaid Belt (e.g., Uzbekistan, Kazakhstan and Kyrgyzstan), we suggest that major porphyry Cu Au deposits may have been developed in the Tulasu basin, probably beneath or adjacent to known epithermal Au mineralization. [Copyright &y& Elsevier]

• 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]

• Caledonian veins overprinted by Yanshanian gold mineralization forming the gold deposits. • Metamorphic-derived barren Caledonian veins having H 2 O-NaCl-CO 2 fluids. • Magma and mantle-derived auriferous Yanshanian veins having H 2 O-NaCl fluids. The Jiangnan Orogen, situated between the Yangtze and Cathaysia blocks in South China, is an important gold-polymetallic metallogenic belt in China. Like many gold deposits hosted in Precambrian rocks in eastern China, the timing of gold mineralization in the Jiangnan Orogen, mostly hosted by Neoproterozoic rocks, has been controversial. A number of previous geochronological studies have suggested that mineralization ages range from Neoproterozoic to Cretaceous, with Caledonian (Early Paleozoic) and Yanshanian (Jurassic – Cretaceous) being considered most important. As Caledonian is the most important period of regional metamorphism, and Yanshanian is the most important period of granitic magmatism, the timing of mineralization is closely related to the genetic nature (orogenic versus post-orogenic) of the gold mineralization. This paper addresses these problems by studying the ages and characteristics of ore-forming fluids of two major gold deposits (Wangu and Huangjindong) in the central part of the Jiangnan Orogen, in northeastern Hunan. Muscovite Ar-Ar dating suggests that the bulk of the quartz veins in the Wangu and Huangjindong deposits were formed at ca. > 399 – 397 Ma, i.e., during the Caledonian orogeny, whereas gold mineralization (and associated veining) took place at ca. 142 – 130 Ma, i.e., during the Yanshanian orogeny. Fluid inclusions in the barren "Caledonian veins" are characterized by the H 2 O-NaCl-CO 2 system, homogenization temperatures of 266 – 276 °C and salinities of 5 – 5.4 wt% NaCl equivalent, similar to those found in many orogenic-type gold deposits, whereas the fluid inclusions in the gold-bearing "Yanshanian veins" (with abundant sulfides) overprinting the barren veins have a H 2 O-NaCl composition system, homogenization temperatures of 169 to 256 °C, and salinities from 8.7 to 15.2 wt% NaCl equivalent. It is proposed that both the Caledonian and Yanshanian veining events are controlled by the same fracture systems, with the former being formed in a relatively deep, orogenic deformation-metamorphic environment, and the latter in a relatively shallow, extensional environment accompanied by extensive granitic magmatism. Reactivation of the Caledonian structures during the Yanshanian orogeny, together with availability of sulfur and gold, possibly associated with granitic intrusions, played a key role in the formation of the gold deposits in northeastern Hunan and possibly elsewhere in the Jiangnan Orogen. [ABSTRACT FROM AUTHOR]

[Display omitted] • The predominant alteration characterized with bleaching of host rocks. • Abundant siderite and sericite present in the bleaching zone. • Bleaching alteration formed by water–rock interaction between pre-ore CO 2 -bearing fluid and wall rocks. • Siderite in altered rocks precipitating gold by triggering sulfidation. Hydrothermal alteration commonly occurs in lode gold deposits, and contributes to metal precipitation through water–rock interactions. In the Wangu gold deposit in northeastern Hunan, South China, bleaching of slates enclosing auriferous quartz veins widespreadly occur, with the colour transformed from dark-grey into pale yellow-grey. The bleaching has been used to guide gold exploration, but its nature and genesis, as well as the relationship with gold mineralization, remains unclear. Field and petrographic work, combined with Tescan Integrated Mineral Analyzer (TIMA), demonstrates that the bleaching is mainly caused by the combination of sericitization and carbonatization. Combined with fluid inclusion studies, it is inferred that bleaching is caused by the pre-ore hydrothermal event characterized with CO 2 -bearing fluids. Large amounts of siderite are distributed within the bleaching zones, and they are locally crosscut by sulfides, suggesting that the bleaching happened before gold mineralization. Mass balance calculation and μ-XRF analysis indicate that despite the abundance of siderite, Fe is not gained during alteration. Geochemical path modeling further suggests that siderite is efficient in precipitating Au by decreasing S contents in fluids and destroying Au-bearing complexes. In addition, the siderite contents in altered slates and Au contents in sulfides suggest that the chemical interaction between siderite and ore fluids can produce ores with economic significance. The siderite developed during the pre-mineralization alteration, provided ideal chemical traps and prepared the ground for gold mineralization. When the gold-bearing fluids overprinted the altered rocks, sulfides formed through reaction with siderite. It is concluded that the sulfidation, which resulted in the destruction of Au-S complexes, is the major mechanism for gold mineralization within the bleached slates. [ABSTRACT FROM AUTHOR]

Gold ore deposits in northeastern Hunan Province are hosted within E-W- to ESE-WNW-trending fracture zones in Neoproterozoic meta-sediments of the Jiangnan Orogen. These rocks have been subjected to multiple tectonic deformations, and the nature of structural control on gold mineralization remains poorly understood. It is unclear when the ore-controlling structures were initially formed and why they are favorable for early Cretaceous gold mineralization. We present a systematic structural analysis to establish a structural evolution model and analyze the structural conditions favorable for gold mineralization. Five deformation events (D 1 to D 5) were identified based on crosscutting and/or overprinting relationships of structural elements. It is established that ore-hosting structures were initially formed during early Paleozoic (D 2), and gold mineralization took place during early Cretaceous (late D 4). The reactivation of D 2 structures during the late D 4 tectonic event, when the stress regime transformed from compression to tension, is critical for gold mineralization. It created a structural network linking mineralizing fluids to structural-chemical traps in Neoproterozoic rocks, where fluid-rock reactions and fluid mixing resulted in gold mineralization. This case study provides a typical example of how structural reactivation played a critical role in mineralization, and emphasizes the significance of structural analysis for mineral exploration. [Display omitted] • Reactivation of early Paleozoic structures in early Cretaceous controlled gold mineralization. • Change of stress regime in the transition from compression to tension favored fault reactivation. • Network of reactivated structures linking ore fluids and structural-chemical traps is critical for gold mineralization. [ABSTRACT FROM AUTHOR]