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Graphical abstract Highlights • The Bianbianshan deposit is a typical Cu-polymetallic deposit of the CMB. • Ore-forming fluids are attributed to a moderate T, ρ and moderate-low S NaCl system. • Cu mineralization occured in the deposit during the Early Cretaceous. • Fluid boiling and local mixing with meteoric water drove Cu precipitation. Abstract The Bianbianshan Cu-polymetallic deposit is located in the Xilamulun Cu-Mo belt of Inner Mongolia, NE China, and occurs within Late Jurassic andesite, rhyolite and tuff. Cu mineralization is observed in various types of hydrothermal disseminated veins exhibiting siliciification, sericitization and chloritization. The ore-forming process occurred in four stages: (1) chalcopyrite-pyrite-quartz, (2) pyrite-chalcopyrite-quartz-vein, (3) sphalerite-galena-quartz-vein, (4) and quartz-calcite-vein. Three types of fluid inclusions were identified in the deposit, including C-type (CO 2 -NaCl-H 2 O) as well as V- and L-type (NaCl-H 2 O) inclusions, where only L-type inclusions are observed in the fourth stage. Homogenization temperature of fluid inclusions in the four stages are 325–365 °C, 282–335 °C, 268–312 °C, and 195–259 °C, respectively, all of which exhibit salinities lower than ∼ 13 wt% NaCl equiv. Trapping pressure estimated from C, V- and L-fluid inclusions are between 550 and 900 bars, corresponding to minimum depths of 2.5–3.7 km. Hydrogen and oxygen isotopic compositions of quartz from different stages (δD = −109.7 ~ –107.6‰, δ18O = 7.6–9.6‰, V-SMOW) suggest that the mineralizing fluid gradually evolved from a magmatic to a meteoric origin. Sulfur (δ34S V-CDT = −0.7 to 0.4‰) and lead isotopes (208Pb/204Pb = 37.746–38.137‰; 208Pb/204Pb = 15.52–15.56%; 206Pb/204Pb = 17.75–18.36%) indicate that ore-forming materials were derived from mantle with minor additional participation of crustal reservoirs. Our data suggests the ore-forming fluids of the Bianbianshan Cu-polymetallic deposit are attributed to a moderate temperature, moderate-low salinity, and moderate density system, where decreases in pressure, phase separation and local mixing with meteoric water drove precipitation of metals. [ABSTRACT FROM AUTHOR]

[Display omitted] • Superimposing mineralization (480 Ma for Cu and 246 Ma for Au-Zn) occurred at Zhengguang. • Ore fluids of both events were magmatic-sourced with meteoric water input. • Metal source for the two events was magma and magma-wallrock mixed, respectively. The Duobaoshan orefield is located in the eastern part of the Central Asian Orogenic Belt (CAOB) and underwent multiphase magmatism and mineralization. The Zhengguang deposit in the orefield is characterized by porphyry copper mineralization and intermediate-sulfidation (IS) epithermal gold mineralization. The porphyry-type veinlet-disseminated sulfide mineralization (~480 Ma) is hosted in granodiorite/tonalite porphyries and hydrothermal breccias, and is associated with widespread potassic (K-feldspar and biotite) alteration. Three porphyry-type mineralization stages have been identified: (I-1) quartz + medium-fine grained pyrite, (I-2) quartz + pyrite + chalcopyrite, and (I-3) quartz + calcite + minor pyrite. The IS epithermal vein/veinlet-disseminated mineralization occurs in andesite porphyry and fractures of the Duobaoshan Formation volcanic rocks, and is associated with extensive silicic, sericitic, and pyrite-sericitic-silicic alterations and minor propylitic alteration. Three IS epithermal-type mineralization stages are identified: (II-1) quartz + coarse-grained pyrite, (II-2) quartz + polymetallic sulfides, and (II-3) quartz + calcite + barren sulfides. Five stage II-2 pyrite samples yielded a Re-Os isochron age of 246.0 ± 6.4 Ma (MSWD = 0.85), suggesting a Triassic Au mineralization event after the Ordovician Cu mineralization. Stage I-1 fluid inclusions (FIs) are predominantly of VL- and LV-type and minor SL-type, with homogenization temperatures (T h) of 283–359 ℃ and salinities of 0.3–35.1 wt%. Stage I-2 is characteristically composed of VL- and LV-type inclusions with T h of 193–296 ℃ and salinities of 0.8–14.2 wt%. Only VL-type inclusions occur in stage I-3, II-1, II-2, and II-3 with T h of 149–216 ℃, 213–285 ℃, 169–236 ℃, and 125–176 ℃, and salinities of 2.4–7.9 wt%, 6.5–12.2 wt%, 3.4–8.8 wt%, and 2.1–6.3 wt%, respectively. H-O isotopic compositions for the mineralization (Ordovician: δ18O H2O = -9.9 to −0.5‰, δD = -86 to −75.6‰; Triassic: δ18O H2O = -8.4 to −2‰, δD = −134.1 to −88.5‰) indicate two different evolving fluid systems, both with an initial magmatic source and a later meteoric water incursion. Sulfur and lead isotope (Ordovician: δ34S (−3.1 to −0.7‰), 206Pb/204Pb (17.570–17.613), 207Pb/204Pb (15.427–15.441), 208Pb/204Pb (37.258–37.294); Triassic: δ34S (-5.4 to −2.5‰), 206Pb/204Pb (17.627–17.965), 207Pb/204Pb (15.466–15.534), 208Pb/204Pb (37.468–37.703)) values suggest a dominantly magmatic and a mixed magmatic-sedimentary source for the Ordovician and Triassic mineralization, respectively. [ABSTRACT FROM AUTHOR]