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In this contribution, the largest porphyry Mo deposit in NE China, Chalukou, is selected to provide insights into the tectonic evolution of NE China. The deposit was considered to be rift-related (or Climax-type) porphyry Mo deposit developed in an extensional setting, while other researchers attributed its formation to the subduction of the Paleo-Pacific Ocean. In view of different granite petrogenesis between rift-type and subduction-type porphyry Mo deposits, geochronological and zircon Lu–Hf isotope studies have been carried out on granitic rocks associated with the Chalukou deposit. Zircon grains from the ore-host monzogranite and ore-causative granite porphyry yield weighted mean 206 Pb/ 238 U ages of 166 ± 2 Ma and 152 ± 2 Ma, with molybdenite samples yielding a Re–Os isochron age of 150 ± 2 Ma, indicating a Jurassic age for both granitic intrusion and Mo mineralization. Zircon εHf(t) values of monzogranite and granite porphyry range from 0.9 to 3.0 and from − 1.4 to 0.5, respectively. When integrated with published zircon Lu–Hf isotopic data, our data suggest that the barren granites (both pre- and post-ore) were mainly derived from mantle-derived juvenile rocks, whereas the syn-ore granite requires additional involvement of old continental crust. Thus, a contribution of continental crust to Mo mineralization is suggested. The petrogenesis and geochemical data reveal that the Chalukou deposit is a subduction-related porphyry Mo deposits and not rift-related. Integrated evidence links its formation to the southeastward subduction of the Mongol–Okhotsk Ocean, instead of the westward subduction of the Paleo–Pacific Ocean. [ABSTRACT FROM AUTHOR]

[Display omitted] • Taishanmiao was constructed by three pulses of magmatism at 125, 123 and 116 Ma. • The latest porphyritic syenogranite induced Mo mineralization at Zhuyuangou. • The highly fractionated I-type granite results from partial melting of ancient crust. • Small porphyry can concentrate Mo from batholith and then effectively deposit it. The Qinling Orogen is well known for its huge Mo resource. The porphyry Mo deposits are associated with small granite porphyries, albeit great batholiths accommodate limited Mo mineralization. In this study, detailed geochemical, isotopic, and geochronological studies were carried out to constrain the petrogenesis of the Taishanmiao batholith and time framework of magmatism and associated Mo mineralization at Zhuyuangou. Zircon geochronology reveals gradually decreasing emplacement ages, from 124.8 ± 1.0 Ma for the medium- to coarse-grained syenogranite, through 122.8 ± 1.4 Ma for fine- to medium-grained syenogranite, to 115.1 ± 0.95 Ma for porphyritic syenogranite. The last two phases hosted the Zhuyuangou Mo mineralization with a molybdenite Re-Os isochron age of 117.7 ± 1.0 Ma. Major and trace element features support highly fractionated I-type affinity for Taishanmiao. Zircon Lu-Hf isotopic studies yield ε Hf (t) values of −19.6 − -8, and two-stage Hf model ages (T DM2) of 1679–2408 Ma. It thus supports ancient continental crust, especially Taihua Supergroup and Xiong'er Group, as the primary source. Compared to the source rock, the low Mo concentrations of the batholith are attributed to the massive fluid flux that contributes to the formation of the Zhuyuangou and Donggou deposits. Small porphyries can effectively concentrate exsolved fluids and metal compared with great batholith. Their shallow emplacement depths result in greater temperature/pressure/composition gradient with the wall rocks, higher cooling rate, more fractures or even breccia, and fluid boiling and mixing, facilitating intensive hydrothermal alteration and mineralization. [ABSTRACT FROM AUTHOR]

Abstract: Mesozoic granitoids are widespread in the southern margin of the North China Craton, and of particular geological interests because of their indication for lithospheric evolution and close association with porphyry Mo mineralization. In this contribution, in situ LA-ICP-MS U–Pb, Hf isotope and trace element analyses of zircon crystals have been combined to constrain the emplacement time and petrogenesis of the Heyu granitic batholith which hosts the Yuchiling porphyry Mo system, Henan Province, China. As inferred from field investigations, the concentrically zoned Heyu batholith mainly consists of four texturally distinguishable phases, and displays a pattern of monotonically decreasing U–Pb age from 143.0±1.6Ma for Phase 1, through 138.4±1.5Ma for Phase 2, through to ca. 135Ma for Phase 3, and to 133.6±1.3Ma for the Mo-mineralized Yuchiling granite porphyry (Phase 4). The εHf(t) values (−27.7 to −3.4) and the two stage Hf model ages (1403 to 2924Ma) of zircon grains, together with the ages of local strata, suggest that the magmas forming the Heyu batholith were dominantly sourced from the crust, with input of a mantle component. The higher Ce/Ce* ratios of the zircon crystals in the mineralized Yuchiling porphyry compared to those in the Mo-barren phases suggests that fluids exsolved from oxidic magmas might be more favorable for Mo enrichment. A regional synthesis suggests that intensive lithospheric thinning in the southern margin of the North China Craton should not be earlier than 130Ma. [Copyright &y& Elsevier]

Abstract: The Xiaoqinling terrane in central China is the second largest gold producing area in China. Previous application of age constraints has yielded ages for the gold mineralization ranging from Paleoproterozoic, through Triassic (Indosinian), to Jurassic and Cretaceous (Yanshanian). SHRIMP U–Th–Pb dating of hydrothermal monazite in a Mo-mineralized quartz vein from the Dahu Au–Mo deposit in the northern Xiaoqinling terrane identifies two mineralization episodes. Hydrothermal monazite intergrown with molybdenite yields an initial precipitation age of 216±5Ma, which is identical to, but more precise than, the molybdenite Re–Os isochron age of 218±41Ma. A younger generation of monazite is distinguished by data falling on a mixing array. It is inferred that the younger monazite was formed at the expense of the older ones during the Yanshanian, probably during a single event that occurred at ~125Ma. Combining these results with available geochronological data and geological evidence, we conclude that molybdenum mineralization accompanied by monazite deposition took place in the Indosinian, followed by a Yanshanian tectono-hydrothermal event that resulted in large-scale gold mineralization in the Xiaoqinling terrane. Our observation demonstrates that monazite is sensitive to hydrothermal overprint, and thus is useful for dating fluid infiltration event. [Copyright &y& Elsevier]

The widely distributed Devonian granitoids comprise a significant part of the crust in the Chinese Altai, although their petrogenetic implications remain debated. The Habahe Intrusion, comprising biotite granite batholith, gabbroic diorite dikes, and biotite granite hosted-enclaves, is a key magmatic unit to understand the extensively developed magmatism in the Chinese Altai. To investigate their petrogenesis and tectono-magmatic significance, this study presents comprehensive petrological, geochronological, and geochemical studies on the Habahe Intrusion. The geochronological results indicate that the enclaves and the host biotite granite share similar ages (395.1 ± 3.7 Ma, MSWD = 4.5 and 395.1 ± 2.5 Ma, MSWD = 0.21, respectively), and slightly older than the gabbroic diorite dikes (378 ± 4 Ma), suggesting the Devonian magmatism. The biotite granite (SiO 2 = 73.9%–76.4%) is amphibole-bearing and shows I-type granite affinity. The enriched zircon Hf (εHf(t) = +2.5 to +5.4), near zero whole-rock Nd (εNd(t) = −1.0 to −0.3) and intermediate Sr isotopes (Isr = 0.7058–0.7072) suggest their generation from the partial melting of the lower crust. The enclaves display variable mineral proportions (amphibole dominated to quartz dominated), major (SiO 2 = 48.6%–62.4%, Mg# = 34.3–67.0), trace element compositions (ΣREE = 20.0–194.5 ppm) and Sr Nd isotopes (εNd(t) = −0.6 to +4.1, Isr = 0.7023–0.7055), indicating their hybrid nature. Together with the acicular apatite and quenched rims of the enclaves, they show a magma mixing event. Nevertheless, the biotite-rich rims of the enclaves and the homogenous compositional and isotopic characteristics of the host biotite granite suggest limited mixing/mingling. The gabbroic diorite dikes (SiO 2 = 48.8–52.4%), consisting of amphibole and plagioclase, display E -MORB-like trace and rare earth element patterns and have depleted Hf (εHf(t) = ∼ + 9), Nd (εNd(t) = +1.7 to +7.3) and low Sr (Isr = 0.7045–0.7089) isotopes, pointing to an asthenosphere mantle origin. Combining these, we propose a model suggesting that the biotite granite was generated by melting of the lower crust, trigged by upwelling of the asthenosphere mantle during subduction. The mafic magma, derived from the partial melted asthenosphere mantle, mixed weakly with the felsic magma from the partial melted lower crust, thereby supplied limited mantle materials for the generation of the biotite granite batholith. This study offers important insights into the extensive Devonian tectono-magmatic processes in the Chinese Altai. [Display omitted] • The gabbroic diorite dikes were derived from the partial melting of asthenosphere mantle in hydrous condition. • The biotite granite crystallized from a common magma derived from the partial melting of the lower crust. • Limited mixing/mingling occurred between mantle-derived mafic magma and crustal-derived felsic magma. • Habahe Intrusion traces the extensive magmatism during the subduction in the Chinese Altai. [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]

The Luoboling Cu–Mo deposit in the Zijinshan Orefield, Fujian province, southeastern China, is a large porphyry deposit hosted by the Sifang granodiorite and the Luoboling granodiorite porphyry. The largest Cu–Mo orebody is saddle-shaped with various types of hydrothermal veinlets. Intensive hydrothermal alteration in the deposit is characterized by outward zoning from potassic, overprinted by phyllic alteration, to phyllic and alunite–dickite alteration. Based on the mineral assemblages and crosscutting relationships of veins, the ore-forming process can be divided into three stages, namely: an early-stage K-feldspar+quartz±magnetite±molybdenite veins associated with potassic alteration; a middle-stage quartz+molybdenite+chalcopyrite+pyrite veins in phyllic zone; and a late-stage quartz±gypsum veins in the phyllic and alunite–dickite alteration zones. Six molybdenite separates yield a Re−Os isochron age 104.6±1.0Ma, which is identical to the age of emplacement of the Sifang and Luoboling granodiorite porphyries. Three types of fluid inclusions (FIs) were observed at the Luoboling deposit: 1) NaCl–H2O (aqueous), 2) daughter mineral-bearing and 3) CO2–H2O fluid inclusions. FIs of the early and middle stages are predominantly vapor-rich aqueous and daughter mineral-bearing inclusions, together with minor CO2-rich and liquid-rich aqueous inclusions; whereas the late-stage minerals only contain liquid-rich aqueous inclusions. Homogenization temperatures and salinities of FIs trapped in the early-stage minerals range from 420 to 540°C and 0.4 to 62.9wt.% NaCl equiv., respectively. FIs of the middle-stage yield homogenization temperatures of 340 to 480°C and salinities of 0.5 to 56.0wt.% NaCl equiv. CO2 content and the oxygen fugacity (indicated by daughter minerals) of FIs trapped in middle-stage minerals are lower than those in the early stage. The liquid-rich aqueous inclusions of the late-stage homogenize at temperatures of 140 to 280°C, yielding salinities of 0.4 to 8.4wt.% NaCl equiv. The minimum estimated pressures of the three stages are 30–70MPa, 10–40MPa and 1–10MPa, respectively, corresponding to minimum ore-forming depths of 1–2.8km. Fluids trapped in early, middle and late stages yield δD values of −67‰ to −54‰, −54‰ to −70‰, and −62‰, and δ18O values of 5.4‰ to 6.7‰, 2.8‰ to 4.2‰, and −2.1‰, respectively. Fluid boiling, which resulted in the formation of stockworks and the precipitation of sulfides, occurred in the early and middle stages. The fluids subsequently evolved into a low temperature, low salinity system in the late stage, along with an input of meteoric water. The Luoboling porphyry Cu–Mo system was developed in a transition from continental arc to back-arc extension region, which was related to the westward subduction of the paleo-Pacific plate beneath the Huanan Orogen. [ABSTRACT FROM AUTHOR]