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The Shapoling Mo deposit is located in the Xiong'er rock mass of the southern margin of the North China Craton. The deposit is hosted in a contact zone between granite and wallrocks of the Taihua Soupergroup, which is a recently found discovered vein dissemination type deposit in East Qinling. The ore-bodies are associated with quartz veins and controlled by subsidiary faults. The mineralization styles include veinlet and disseminated types. In order to determine the age of the Shapoling Mo deposit, Re-Os isotopic dating of molybdenite was conducted. Six molybdenite samples yielded Re-Os ages ranging from 158.3±1.5 Ma to 160.7±1.2 Ma, with a weighted mean age of 160±1 Ma (2σ, MSWD=2.1). The Re-Os age shows that the Mo mineralization occurred during the late Jurassic, earlier than the formation of Huashan rock mass (about 30 Ma). In addition, one molybdenite sample in Huashan rock mass yielded a Re-Os age of 130.5±1.0 Ma, which is in accordance with the age of the Huashan pluton and molybdenite age (125.4-129.4 Ma) reported by a previous study. In conclusion, the Shapoling deposit contains two episodes of Mo mineralization from the early Cretaceous and late Jurassic periods. Combining this with geological characteristics and tectonic-metallogenic evolution, it is suggested that Huashan rock mass, granite porphyry, and related hydrothermal deposits in the Xiong'er terrain are the products of extrusion to extension transition during continent-continent collision in the Qinling orogenic belt.

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] • Mo isotopes variation in both the two Mo deposits may be controlled by Rayleigh and equilibrium fractionation. • The Taihua Soupergroup and the Xiong'er Group would be the main contributor of Mo metal for the Paleoproterozoic Mo mineralization. • The mantle with light isotopically Mo involved into the Mo Paleoproterozoic mineralization in Qinling orogenic belt. Longmendian and the Zhaiwa are the two oldest Mo deposits in the Qinling orogenic belt, China, which is one of the most important Mo provinces in the world with numerous and diverse types of Mo deposits that experienced multistaged mineralization. Here we investigated Mo isotope compositions in molybdenite and rocks from the Longmendian and the Zhaiwa Paleoproterozoic Mo deposits to link Mo isotopes to the sources of Mo metal. The significant Mo isotope variation in the Longmendian and the Zhaiwa Mo deposits (δ98Mo = −0.51‰ to + 1.01‰ and −0.37‰ to +0.53‰, respectively, relative to NIST-3134) may be controlled by Rayleigh and equilibrium fractionation. The different distributions of Mo isotope compositions of molybdenite in the two deposits may be caused by the physiochemical differences in ore-forming systems. The high Mo content of the Taihua Supergroup and the Xiong'er Group, combined mean values of Mo isotopes between molybdenite and whole rocks suggested that the two stratigraphic units would be the main contributor of Mo for the Paleoproterozoic Mo mineralization that mixed with small proportions of isotopically lower values of the mantle. [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]