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The Tudigou porphyry Cu deposit is located in the central part of the southern Qinling belt. Copper mineralization is closely associated with monzogranite porphyry. Zircon LA–ICP–MS U–Pb dating of monzogranite porphyry suggests that the ages of magmatism at Tudigou vary between 150 ± 1 and 148 ± 1 Ma and overlap with the molybdenite Re–Os age of 150–148 Ma, indicating that the Tudigou intrusion and associated mineralization formed during the Late Jurassic. The enrichment in large‐ion lithophile elements, depletion in high‐field‐strength elements, high Ba/Th and La/Yb ratios, and negative correlation between Dy/Yb and La/Sm ratios, together with narrow ranges of εHf(t) values (εHf(t) = −4.0 to +1.4) suggest monzogranite porphyry was derived from a metasomatized lithospheric mantle with minor crustal components contribution, which is also evidenced by the lead isotopic result. The La/Yb ratios of 30 Mesozoic plutons in the southern Qinling belt were used to calculate the Moho depth, which suggests that the magmatism and mineralization in the region occurred during lithosphere thinning in response to the tectonic transition from compression to extension transitional regime. The calculated oxygen fugacity of the Late Mesozoic porphyry deposits in the Qinling–Dabie orogen have identical ΔFMQ values (averaging +1.4 to +2.4). However, the V/Sc ratios (the proxy for water content) are distinct among different deposit sizes, indicating that the dissolved water in the magma plays a critical role in porphyry‐type mineralization. [ABSTRACT FROM AUTHOR]

Qinling orogenic belt hosts many porphyry Mo deposits, which were formed by ore-forming fluids exsolved from oxidized magmas. Detailed processes of ore fluids evolution and metal deposition mechanisms of porphyry Mo deposits remain unclear. The quartz solubility model and cathodoluminescence (CL) images combined with fluid inclusions (FIs) and isotope analyses at the Nantai Mo deposit provide new insights into processes and physicochemical conditions for Mo mineralization. Based on field and microscopy of ore and alteration assemblages together with CL images, four types of hydrothermal veins (i.e., A, B, C, and D veins) have been identified. The quartz in A veins intergrown with K-feldspar precipitated from high-temperature and low- to intermediate-salinity fluids under near-lithostatically conditions. B vein comprises quartz and K-feldspar and forms at 336–466 °C, pH from 6.30 to 11.02, and oxygen fugacity (f O2) of −30.81 to −24.26. Hydrothermal fluids during this stage underwent phase separation under ductile to brittle transition. C veins include muscovite and most molybdenite without quartz, indicating that they formed in the retrograde quartz solubility field at 353 to 398 °C. Thermodynamic calculation suggests molybdenite mainly precipitated under f O2 from −32.37 to −29.05 and pH from 2.68 to 6.54. Quartz in D veins formed from low-temperature and low-salinity fluids. Sulfur isotopic analyses suggest that the ore components are derived from the old crust. The main factors controlling Mo mineralization at Nantai are the decreases in f O2 and pH values of hydrothermal fluids. [Display omitted] • The ore-forming components were sourced from magma that derived from an old crust. • The mark of ore-forming fluids is high-temperature, low- to intermediate-salinity, and intermediate-density. • The decrease in f O2 and pH of the hydrothermal fluids lead to molybdenite formation. [ABSTRACT FROM AUTHOR]

• Ore-forming fluids were dominant by magmatic water which were diluted by later meteoric water. • Ore-forming metals were sourced from mantle with minor crustal components. • Decreases in temperature and Oxygen fugacity, and the fluid boiling contributed to precipitation of sulfides. The Chigou porphyry Cu deposit is located in eastern segment of the Southern Qinling metallogenic belt, on the southern margin of the Central China Orogenic Belt. Copper mineralization is associated with quartz diorite, quartz diorite porphyry and granite porphyry, and occurs as veins, veinlets, disseminations, or veinlet-disseminations within host porphyries. Ore-forming process could be divided into three stages: stage I quartz + K-feldspar + pyrite ± chalcopyrite, stage II quartz + chlorite + chalcopyrite ± molybdenite and stage III quartz + calcite + pyrite. Four types of fluid inclusions (FIs) were distinguished in quartz-bearing veins, including vapor-rich two-phase (V-type), liquid-rich two-phase (L-type), hypersaline (H-type), and CO 2 -rich (C-type) inclusions. The FIs were homogenized at temperatures of 330–473 °C for stage I, 174–345 °C for stage II, and 128–272 °C for stage III, with corresponding salinities of 3.8–53.6 wt% NaCl equiv., 1.4–15.1 wt% NaCl equiv., and 0.4–7.7 wt% NaCl equiv., respectively. Hydrogen and oxygen isotope data indicate that the ore-forming fluids have a dominant magma signature and were diluted by meteoric water during the late stage. Chalcopyrite and pyrite from different stages record a narrow range of δ34S values from −0.2 to −2‰, consistent with the sulfur isotopic values of typical magmatic-hydrothermal system. Chalcopyrite has similar 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios to those of porphyry intrusions. All stable and radiogenic isotope results reveal that the ore-forming components (i.e. metal and sulfur) were sourced from a magmatic reservoir with some crustal materials. Laser Raman micro spectroscopy data and fluid inclusion analytical results suggest that the Chigou deposit was formed by an initially high- to intermediate-temperature, high-oxygen fugacity (f O2) and CO 2 -rich fluid system at an estimated depth of 0.7–2.1 km. Decreases in temperature and f O2 as well as fluid boiling were critical factors controlling sulfide precipitation at Chigou. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two distinct geological ages of molybdenite are determined at Sanchakou. • Decreased temperature and f O2 contributed to porphyry-style ore formation. • High grade copper was likely attributed to overprinting mineralization event. • Identification of an old deformation-related porphyry Cu deposit in Xinjiang is helpful for guiding ore exploration. The Sanchakou Cu deposit is located in the eastern section of the Dananhu arc belt in Eastern Tianshan, Xinjiang, and recorded multiple magmatic-mineralization events. The porphyry-style mineralization period produced disseminated, sulfide-dominant veined, and patchy sulfides containing chalcopyrite ± bornite ± carrolite ± molybdenite (Mol-1), which was associated with magnetite ± biotite ± chlorite ± sericite alteration in a suite of quartz diorite intrusions. The overprinting mineralization period contributed to minor Cu and Mo mineralization, featured by later disseminated molybdenite (Mol-2), chalcopyrite, and widespread low-temperature (<280 °C) vein-type stellerite assemblages. Two distinct geological ages of molybdenite (including Mol-1 and Mol-2) from Sanchakou have been determined in this study. The old 187Re/187Os isochron age for euhedral Mol-1 represents the timing of original porphyry-style mineralization (386 ± 16 Ma), in agreement with LA-ICP-MS zircon U-Pb age of dark diorite dykes (390 ± 11 Ma). The young 187Re/187Os age for fine-grained Mol-2 is interpreted to be a maximum age of sulfide formation or remobilization (364 ± 15 Ma), most likely associated with the emplacement of Late Devonian gneissic granite intrusions. Fluid inclusion microthermometry, mineralogy, and physicochemical calculations for the porphyry-type mineralization period (including four stages) at Sanchakou suggest that earlier magmatic fluids have evolved from high T (310–460 °C), high log f O2 (−22 to − 26), and alkaline condition during stage I to low T, low log f O2 (−3 4), and acidic condition during stage II. The decrease of oxygen fugacity caused by abundant deposition of magnetite in stage I produced large-scale Cu and Mo precipitation. Stage II to IV fluids have gradually decreasing temperatures and salinities, due to involvement of meteoric water that also facilitates the ore deposition. This result is consistent with the evolution of O isotope compositions of the fluids (δ18O fluids = − 9.3 to 4.3), further implying the significance of fluid mixing instead of fluid boiling that caused ore deposition. Locally high-grade copper concentrations at Sanchakou are likely attributed to the overprinting modification event on the original ore bodies. All of these observations indicate that the Paleozoic Sanchakou ore-forming system is similar to other deformed porphyry Cu systems in the Central Asian orogenic belt (CAOB) and worldwide. The Cu mineralization and modification event at Sanchakou is coincident with the second peak productivity in CAOB. We further suggest that the Paleozoic diorite complex and stellerite alteration can be as a significant exploration target for porphyry-style Cu mineralization in the Eastern Tianshan. [ABSTRACT FROM AUTHOR]

[Display omitted] • The f O2 of ore-forming magma at Nantai is suitable for forming a porphyry Mo deposit. • Nantai granitoids are derived from partial melting of lower crust with mantle contribution. • Nantai deposit formed in a compression to extensional transition regime. Late Mesozoic Nantai porphyry Mo deposit is located in the Northern Qinling terrane, eastern China. The intrusions at Nantai include lamprophyre, quartz porphyry, and granite porphyry. Among them, molybdenum mineralization is associated with quartz porphyry and granite porphyry. The ore-bearing porphyries and ore-barren lamprophyres emplaced at ca. 155–146 Ma and ca. 156–146 Ma, respectively. The calculated zircon ΔFMQ values for Nantai felsic and mafic intrusions are –5.0 to +9.1 (an average of + 2.2) and –6.7 to +5.0 (an average of +1.2), which are similar to those of contemporaneous giant Mo deposits in the south margin of the North China Block. The quartz porphyry and granite porphyry are characterized by relatively high SiO 2 (73.39–75.49%), K 2 O (4.24–9.61%), and Rb (291–552 ppm) contents, but low total Fe 2 O 3 (0.13–0.83 wt%), MgO (0.1–0.3 wt%), P 2 O 5 (0.01–0.04 wt%), Sr (22.4–141.0 ppm) and Ba (79.8–1757 ppm) concentrations. These granitic samples have T DM C ages of 2204–1592 Ma, corresponding to negative ε Hf (t) values of –15.8 to –6.2. Geochemical and zircon Lu-Hf signatures as well as lead isotopic analyses for Nantai granitoids suggest that they belong to the high-fractionated I-type granites and were derived from partial melting of lower continental crust with coeval mantle-derived magma contribution. The lamprophyres show low SiO 2 (47.59–49.08%) and Rb (96–120 ppm) contents, whereas they have high Ba (1598–2236 ppm), and Sr (771–990 ppm) concentrations, as well as a lack of negative Eu anomalies. The concentrated ε Hf (t) values (–0.6 to + 3.3), high (Hf/Sm) PMN and La/Sm ratios, as well as Pb isotopic features, indicate that they were derived from an enriched lithospheric mantle that had been metasomatized by subducted components with some crustal material contribution. Combined with our datasets and previous studies, we suggest that the Nantai porphyry Mo deposit formed in a post-orogenic setting. [ABSTRACT FROM AUTHOR]