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The Zhifang Mo deposit is located in the northeastern Qinling Orogen along the southern margin of the North China Craton. The deposit represents a quartz-vein system hosted in the Mesoproterozoic Xiong'er Group volcanic rocks. We identify three hydrothermal stages (early, middle and late), characterized by veinlets of quartz–pyrite, quartz–molybdenite–pyrite–chalcopyrite–galena–sphalerite, and quartz–carbonate assemblages, respectively. Five molybdenite samples from the Zhifang deposit yield Re–Os ages ranging from 241.2 ± 1.6 Ma to 247.4 ± 2.5 Ma, with an isochron age of 246.0 ± 5.2 Ma (2σ, MSWD = 7.4), and a weighted mean age of 243.8 ± 2.8 Ma (2σ, MSWD = 5.5). The Re–Os age shows that the Mo mineralization occurred during the Indosinian Orogeny, and suggests that the mineralization is unrelated to the Yanshanian magmatism or the Paleo-Mesoproterozoic volcanic–hydrothermal event. This study also reports a new Sr–Nd–Pb isotope dataset from ore sulfides in an attempt to constrain the source of the ore-forming fluids. Ten sulfide samples from middle stage of the Zhifang Mo deposit yield I Sr (t) ratios of 0.710286–0.711943, with an average of 0.711004; ε Nd (t) values between − 19.5 and − 14.8, with an average of − 16.7; and ( 206 Pb/ 204 Pb) i , ( 207 Pb/ 204 Pb) i and ( 208 Pb/ 204 Pb) i ratios of 17.126–17.535, 15.374–15.466 and 37.485–37.848, with averages of 17.380, 15.410 and 37.631, respectively. One pyrite from the early stage yield I Sr (t) of 0.722711–0.722855, with an average of 0.722783, which is higher than those of the middle stage sulfides and suggests equilibration with wallrocks. The ε Nd (t) values are in the range of − 17.3 to − 16.6 with a mean at − 17.0; and ( 206 Pb/ 204 Pb) i , ( 207 Pb/ 204 Pb) i and ( 208 Pb/ 204 Pb) i ratios are 17.386, 15.405 and 37.622, respectively. The ore sulfides show higher Pb-isotope ratios, higher ε Nd (t) and lower I Sr (t) values than the host rocks. The results suggest that the ore-forming fluids had lower I Sr (t), and higher ε Nd (t) values than the ore sulfides, and were possibly sourced from the Dengfeng Complex. The southward subduction of the North China Craton beneath the Huaxiong Block during the Triassic was possibly responsible for the formation of the Waifangshan orogenic Mo system. [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 Waifangshan Mo-quartz vein cluster occurs at the northernmost margin of the Qinling Orogen. The orebodies occur as quartz veins and are controlled by low-angle faults. We identify three hydrothermal stages, characterized by veinlets of quartz–pyrite, quartz–molybdenite–pyrite–chalcopyrite–galena–sphalerite, and quartz–carbonate assemblages, respectively. The early-stage quartz veins were structurally-deformed, brecciated, and filled by non-deformed middle- or late-stage veinlets, suggesting that the mineralization is associated with a tectonic transition from compression to extension. Five molybdenite separates from the Zhifang Mo deposit yield individual Re–Os ages from 241.2 ± 1.6 to 247.4 ± 2.5 Ma, with a weighted mean age of 243.8 ± 2.8 Ma. Individual Re–Os isotope ages of four molybdenite samples from the Badaogou Mo deposit range from 238.9 ± 2.1 to 255.8 ± 2.2 Ma, with a weighted mean age of 246 ± 10 Ma. Four analyses of molybdenite separates from the Xiangchungou Mo deposit yield individual Re–Os isotope ages of 243.8 ± 8.8 to 247.7 ± 4.4 Ma, with a weighted mean age of 246.0 ± 1.1 Ma. All of these data yield a weighted mean age of 241.9 ± 1.9 Ma, coeval with the accretionary orogeny. We thus conclude that the Waifangshan Mo-quartz veins formed during a transition from continental arc to back-arc setting. The Waifangshan Mo-quartz veins share similar geological, geochemical and geochronological features with the orogenic-type systems. We propose that the Waifangshan Mo-quartz veins are an orogenic-type Mo mineralization, and possibly represent the deepest member in the crustal continuum model of the orogenic-type mineral systems. The molybdenite samples from the Mo-quartz veins in the Waifangshan area have low Re contents (1.457 to 39.16 ppm), suggesting a continental crust-dominated source. [ABSTRACT FROM AUTHOR]