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The newly discovered giant Dahutang W–Cu–Mo deposit in the central part of the Jiangnan Orogen hosts an estimated resource of 1.1 million tons (Mt) of WO 3 , plus a proven resource of 0.65 Mt Cu and 0.08 Mt Mo. The Dahutang deposit is temporally and spatially associated with the Late Mesozoic S-type granites emplaced into the Neoproterozoic Jiuling granodiorite batholith and the Shuangqiaoshan Group. Based on petrographic observations, eight hydrothermal alteration/mineralization stages have been recognized, comprising pegmatitic (Stage I), potassic alteration (Stage II), albite alteration (Stage III), greisenization and main mineralization (Stage IV), polymetallic sulfide mineralization (Stage V), late scheelite mineralization (Stage VI), carbonate alteration (Stage VII) and supergene alteration (Stage VIII). Stage IV can be further divided into the early greisenization (Stage IV-A), the main wolframite mineralization (Stage IV-B) and the main scheelite mineralization (Stage IV-C). Fluid inclusion and H–O isotope analyses on nine Stage IV to VII ore/gangue minerals (wolframite, cassiterite, scheelite, sphalerite, fluorapatite, fluorite, quartz, calcite and chlorite) suggest the presence of an early W and a late Cu–Mo ore-forming fluid system. The early ore-forming fluids belong to a medium to high temperature (200°–420 °C), low salinity H 2 O–NaCl–CaCl 2 system. This primary magmatic-hydrothermal fluid (δ 18 O fluid  = 5.4 to 8.8‰ and δD = −102 to −75‰) was likely exsolved from the Late Jurassic granites at Dahutang. Wolframite and scheelite coexist closely with fluorapatite and fluorite, respectively, indicating that the volatile-rich fluids at Dahutang were also rich in tungsten, fluorine and phosphorous. Tungsten was likely transported as tungstate species (e.g., WO 4 2− and HWO 4 − ), oxygen fluorine complexes (e.g., [WO 2 F 4 ] 2− , [WO 3 F 2 ] 2− ) and phosphorous heteropolytungstate (e.g., [P(W 12 O 40 )] 3− ) in the fluids. Fluorapatite and wolframite may have precipitated first when the temperature dropped from 400° to 320 °C (along with pH increase) at an estimated depth of 7.8 km. This was likely followed by the extensive scheelite mineralization (with fluorite precipitation) that formed huge disseminated/veinlet-type W orebodies when the temperature further dropped to 200 °C (along with pH increase). After the W mineralization, extensive Cu–Mo polymetallic mineralization and the associated sericite-chlorite alterations may have formed by the granite porphyry and/or muscovite granite emplacement. The late ore-forming fluids belong to a medium to high temperature (200°–360 °C), low salinity H 2 O–NaCl–CaCl 2 system. Molybdenum was likely transported mainly as Mo complexes (e.g., H 2 MoO 4 /MoO 4 2− ), and copper as Cu–Cl complexes. Molybdenite and chalcopyrite may have begun to precipitate when the fluids ascended and the temperature dropped to 330 °C. Meteoric water incursion may have then occurred (δ 18 O fluid  = 1.9–6.9‰ and δD = −99 to −68‰) and further cooled the fluid system to 250 °C, forming large Cu–Mo orebodies. [ABSTRACT FROM AUTHOR]

This study first described three-dimension images of a fluid inclusion hosted within sphalerite based on transmission nano X-ray tomography. It shows multiple shapes of the fluid inclusion viewed from different angles. This fluid inclusion contains both vapor and liquid phases, with irregular, asymmetry shape and concaved boundary. A reconstructed three-dimension animation viewer makes the shapes clearly. This study offers a technique to penetrate inside the fluid inclusion and calculate the volume of the single fluid inclusion based on the 3D images and animation, which can be applied for the future single fluid inclusion compositional studies. [ABSTRACT FROM AUTHOR]

The Shagou deposit, located in the eastern Qinling orogenic belt, central China and hosted by the Taihua Supergroup, is a large-sized Ag–Pb–Zn deposit and has proven reserves of 1.54million tons of ore with grades of 767g/t Ag, 13.24% Pb and 4.31% Zn. The ore-forming fluids have been previously interpreted as products of direct exsolution of a crystallizing magma or sudden decompression of the fluid exsolved from magma, defining the Shagou deposit as an intrusion-related system. In this study, the Shagou deposit has been identified as an orogenic type mineralization system. The hydrothermal ore-forming process can be divided into the early quartz–pyrite, middle quartz–polymetallic sulfides and late quartz–carbonate stages. Four types of fluid inclusions in quartz can be distinguished between PC, C, W and PW types. The early and middle stage quartz contains the PC, C and W type fluid inclusions, while only W and PW type fluid inclusions can be observed in the late stage quartz. In the early stage, the W type fluid inclusions homogenized at 173–369°C (concentrating at 200–240°C), with salinities ranging from 5.4 to 8.3wt.% NaCl equiv. But in the middle stage, the C and W type fluid inclusions homogenized at 112–313°C (concentrating at 180–220°C), with salinities ranging from 0.7 to 13.6wt.% NaCl equiv. In the late stage, the W type fluid inclusions homogenized at 108–253°C (concentrating at 160–200°C), with salinities ranging from 2.1 to 8.1wt.% NaCl equiv. The fluids may have experienced a boiling process or fluid mixing in the middle stage. The estimated trapping pressures of fluid inclusions in the middle stage ranged from 33 to 211MPa, corresponding to a mineralization depth from 3.3 to 7.7km. For the early stage fluids, the calculated δ18OH2O and δDH2O values are 7.5–9.1‰, −96.2 to −110.5‰, respectively. For the middle stage fluids, these two values are 1.5–5.3‰, −75.6 to −110.7‰ but change to 1.0‰ and −87‰ for the late stage, suggesting an evolution from metamorphic to meteoric in origin. In general, the Shagou Ag–Pb–Zn deposit is similar in many respects to typical orogenic type mineralization systems. [ABSTRACT FROM AUTHOR]

The East Qinling region in central China, hosting several tens of Mesozoic magmatic-hydrothermal Mo deposits, is one of the largest molybdenum belts in the world. The Zhifang Mo deposit is hosted in volcanic rocks of the Xiong'er Group in the Waifangshan area, Qinling Orogen. Previous studies variously correlated the mineralization in this deposit with Yanshanian magmatism or Palaeo-Mesoproterozoic volcanic-hydrothermal events. The orebodies are associated with quartz veins and controlled by subsidiary faults of the Machaoying Fault. The ore-forming process can be divided into the early, middle and late stages and is characterized by quartz-pyrite, quartz-polymetallic sulphide and quartz-carbonate veins, respectively. The early-stage quartz is structurally deformed, suggesting a compressional tectonic regime; the middle-stage sulphides fill the fractures of the early-stage assemblages and show no deformation, suggesting a tensional setting; the late-stage veins mostly infill the open-space fissures. Three types of fluid inclusions (FIs) are identified at the Zhifang deposit: H2O-NaCl (W-type), CO2-rich (C-type) and daughter mineral-bearing inclusions (S-type). Fluid inclusions of early-stage quartz homogenize between 380 and 470 °C, with salinities ranging from 0.4 to 9.6 wt.% NaCl equiv., whereas the late-stage calcite contains only the W-type FIs with homogenization temperatures of lower than 240 °C, and salinities of 0.4-8.7 wt.% NaCl equiv. This indicates that the ore fluid system evolved from CO2-rich, probably metamorphic hydrothermal to CO2-poor, meteoric fluid. All three types of FIs can be observed in the middle-stage quartz, and even in the microscopic domain of a crystal, suggesting that this heterogeneous association was trapped from a boiling fluid system. These FIs homogenized at temperatures ranging from 250 to 360 °C and display two salinity clusters of <18.5 and 29.1-29.9 wt.% NaCl equiv. These results suggest that metal precipitation resulted from fluid boiling. The estimated trapping pressures of FIs range from 101 to 285 MPa, suggesting an alternating lithostatic-hydrostatic fluid system, which was controlled by a fault-valve at the depth of 10 km. The δ34S values of ore minerals from the Zhifang Mo deposit show a range between −11.8‰ and 6.0‰, with a bimodal distribution. The early-stage pyrite has a positive δ34S value of 6.0‰ that is similar to the host rocks of the Xiong'er Group and the Taihua Supergroup, suggesting that the wall rocks contributed much of the sulphur to the early-stage pyrite during fluid-rock interaction. However, the δ34S values of the middle-stage sulphides have negative mean and restricted range from −11.8‰ to −4.5‰. The widespread rutile grains coexisting with molybdenite in the middle-stage correlate the negative δ34S values with relatively oxidized fluids. We consider phase separation as an efficient mechanism for ore-fluid oxidation and molybdenum deposition based on fluid inclusions and sulphur isotope data. Geological, fluid inclusion and sulphur isotope data of the Zhifang Mo deposit suggest that the Mo mineralization is unrelated to the Yanshanian magmatism or the Palaeo-Mesoproterozoic volcanic-hydrothermal event. Here we propose that the Zhifang Mo deposit may be considered as an orogenic mineral system, with its formation in an active continental margin related to the northward subduction of the Mian-Lue oceanic plate during the Triassic. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The East Qinling Molybdenum Belt (EQMB), central China, hosting tens of Mesozoic magmatic hydrothermal Mo deposits, is one of the largest molybdenum belts in the world. Recently, a new type of Mo mineralization characterized by molybdenite-fluorite veins was discovered with ongoing prospecting at the Tumen area in the Huaxiong block, representing the southernmost tectonic unit of the North China Craton. The molybdenite-fluorite veins occur in faults or ductile shear zones cross-cutting the Neoproterozoic Luanchuan Group. At the Tumen deposit, CO2-rich, aqueous and daughter mineral-bearing fluid inclusions are observed in fluorite. These fluid inclusions resemble those reported from magmatic hydrothermal Mo systems formed in intracontinental tectonic settings and yield homogenization temperatures up to 450 °C, with salinities up to 39.8 wt.% NaCl equiv, suggesting that the mineralization resulted from a magmatic fluid system. Seven molybdenite analyses from the molybdenite-fluorite veins yield Re-Os isotope ages ranging from 845.8 ± 7.3 to 965.3 ± 7.2 Ma, with an isochron age of 847.4 ± 7.3 Ma (2 σ, MSWD = 23), marking the timing of mineralization as Neoproterozoic. These ages are broadly comparable with the 844.3 ± 1.6 Ma age reported from the Shuangshan syenite located near the mining area, and the ca. 830 Ma gabbros occurring within the same tectonic unit, indicating that the deposit was possibly related to Neoproterozoic rifting at the southern margin of the North China Craton. The age data correspond to the transition from the culmination of the assembly of the Neoproterozoic supercontinent Rodinia to the beginning of its break-up. Our results provide new insights into the regional tectonics and show that the Mo mineralization is not related to the much younger Mesozoic Yanshanian magmatism as considered in previous studies. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

[Display omitted] • Five ore-forming stages are recognized in the Yechangping porphyry-type orebodies. • Fluid characteristics suggest that Yechangping is a Dabie-type porphyry Mo deposit. • The process of fluid immiscibility, boiling, and mixing cause the mineralization. • Magmatic-hydrothermal system of Yechangping deposit extends to depths of 10 km. Dabie-type porphyry Mo deposits have recently emerged as a distinct subtype of porphyry Mo deposits, but questions remain about the magmatic-hydrothermal fluid evolution in the formation of this type of deposit. Here, well-developed fluid inclusions in quartz phenocrysts, unidirectional solidification textures (UST), and quartz veins in the Yechangping porphyry Mo-W deposit, Qinling Orogen, completely record the magmatic-hydrothermal mineralization process. The characteristics and evolution of the ore-forming fluid in this deposit are investigated through petrography, microthermometry, and laser Raman spectroscopy analysis of fluid inclusions at different stages in order to improve our understanding of the fluid evolution in the genesis of Dabie-type porphyry Mo deposit. The mineralization process in the porphyry-type orebody can be divided into three periods and five stages: (1) magmatic period, including quartz phenocrysts (stage 1); (2) magmatic-hydrothermal transition period, including UST (stage 2); (3) hydrothermal period, including quartz ± K-feldspar veins (stage 3), quartz-molybdenite veins (stage 4), and calcite ± quartz veins (stage 5), where stage 4 is the main ore-forming stage. The fluid inclusions in quartz and calcite can be recognized as pure CO 2 (PC type), CO 2 -H 2 O (C type), daughter minerals-bearing (S type), and H 2 O (WV type and WL type) inclusions. Ore-forming fluid is initially high temperature, high salinity, and CO 2 -rich, belonging to the H 2 O-CO 2 -NaCl (±KCl) system suggested by the fluid inclusions identified in UST. The estimated lithostatic pressures of stage 1 range from 284–362 MPa, corresponding to depths of 10.3 to 13.2 km, which are consistent with the formation depth of the underlying magma chamber. The presence of UST in stage 2 indicates that the magma was saturated with fluid. Due to the fluctuating pressure (123–260 MPa) in UST of stage 2, fluid immiscibility happened soon after the fluid exsolution and is inferred to occur between the CO 2 -rich and aqueous phases. Then, the fluid boiling and mixing occurred in stages 3 and 4, respectively. The estimated pressures of stage 4, which represent the main mineralization stage, range from 45–175 MPa, corresponding to depths of 4.6–6.4 km. The immiscibility of CO 2, along with the fluid mixing-induced cooling and dilution, caused an increase in p H and a decrease in oxygen fugacity, which serves as a crucial mechanism for Mo mineralization at the Yechangping deposit. Stage 5 is characterized by low temperature (185–309 °C) and low salinity (2.9–8.7 wt% NaCl equiv.). The primary high temperature, high salinity, CO 2 -rich fluids, and relatively deep ore-forming depth suggest that the Yechangping deposit is a typical example of a Dabie-type porphyry deposit. The characteristics of fluids and the variation in estimated depth at each stage record the evolutionary process of a magmatic-hydrothermal system extending to depths of nearly 10 km in the Yechangping deposit. [ABSTRACT FROM AUTHOR]