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Most skarns are found near the pluton or in lithologies containing at least some limestone. However, recent research has shown that neither a pluton nor limestone is necessarily required to form a skarn deposit. The newly discovered Bagenheigeqier Pb–Zn skarn deposit is located in NE China. The skarn and Pb–Zn orebodies occur in volcanic lithologies of the Baiyin'gaolao Formation and are controlled by NE–SW-trending faults. The nearest pluton is a granite porphyry, at a distance of 20–250 m from the orebodies. Five paragenetic stages at Bagenheigeqier are recognized: (I) skarn; (II) oxide; (III) early sulphide; (IV) late sulphide; and (V) late quartz–calcite. The fluid inclusions from stages II to V homogenized at temperatures of 402–452, 360–408, 274–319 and 167–212°C, respectively. The hydrogen and oxygen isotope compositions (δ18OH2O, –12.4‰ to +9.3‰; δDH2O, –156.5‰ to –99.1‰) indicate that the ore-fluids were primarily of magmatic origin, with the proportion of meteoric water increasing during the progression of ore formation. Sulphur isotope values (δ34SVCDT, 1.4–5.5‰), lead isotope values (206Pb/204Pb, 18.184–18.717; 207Pb/204Pb, 15.520–15.875; 208Pb/204Pb, 37.991–38.379) and the initial 187Os/188Os ratios of the pyrite (0.307 ± 0.06) suggest that the ore metals were derived from the granite porphyry and Baiyin'gaolao Formation. Re–Os dating of pyrite intergrown with galena and sphalerite yielded a well-constrained isochron age of 151.2 ± 4.7 Ma, which is coeval with the laser ablation – inductively coupled plasma – mass spectrometry zircon U–Pb age of 154 ± 1 Ma for the granite porphyry. The deposit was therefore formed during Late Jurassic time. [ABSTRACT FROM AUTHOR]

The Meng'entaolegai Ag-Pb-Zn vein-type deposit in Inner Mongolia, NE China is hosted in biotite/muscovite granite. This deposit includes the western (Zn-rich, deepest), middle (Zn-Pb rich) and eastern (Pb-Ag-rich, shallowest) ore-blocks. To better understand the metallogenic processes in ore district, we have undertaken a series of studies including fluid inclusion microthermometry, H-O-S-Pb isotope compositions and thermodynamic modeling. Based on fluid inclusion petrography, microthermometry results and HO isotope compositions, the ore-forming H2O-NaCl fluid inclusions are characterized by medium temperature and medium salinity. And two kinds of fluid processes (boiling in western and middle ore-block and fluid mixing in the eastern ore-block) were identified to explain the ore fluid evolution. More importantly, log ƒO2- pH diagrams of δ34S contours with the stability fields of Fe- and Cu-, Zn-, Pb-, and Ag-bearing minerals were constructed to restore the physicochemical conditions of ore-forming fluid in the western (270 °C and 80 bars), middle (250 °C and 70 bars), and eastern (230 °C and 50 bars) ore-blocks. As a result, the ore-forming conditions in the western and middle ore-block were similar. In the eastern ore-block, the fluids may have changed from acidic, S-poor and δ34S(ΣS)≈2.8 to neutral, S-richer and δ34S(ΣS)≈0.5, which imply that neutral S-rich meteoric water was mixed with the magmatic fluid. Meanwhile, the activity of Ag+ was estimated to be about 10 ppm–9 ppm in the middle ore-block, but in the eastern ore-block it was about ~10 ppm–12 ppm. We proposed that the key for Ag ore deposition was likely to be neutralization led by fluid mixing. [ABSTRACT FROM AUTHOR]

The Hua'naote Ag-Pb-Zn deposit (Inner Mongolia, northern China) is a hydrothermal vein-type deposit in the Erlianhot-Dongwuqi Metallogenic Belt (EDMB), which is situated in the eastern Central Asian Orogenic Belt (CAOB). Mineralization occurs in the contact between monzogranite and the Devonian Angeer Yinwula Formation (Fm.) silty slate, and is also closely related to syenogranite. The mineralization can be divided into three stages: (I) arsenopyrite + pyrite + quartz, (II) pyrite + galena + sphalerite + chalcopyrite + quartz, and (III) galena + sphalerite + calcite + quartz. Fluid inclusions (FIs) from Hua'naote are liquid-rich (L-type), vapor-rich (V-type), CH 4 + CO 2 (C1-type), CO 2 -bearing (C2-type), and daughter-mineral-bearing three-phase (S-type). Laser Raman spectral analysis shows that the gas phase in Stage I and II C2-type FIs is mainly composed of H 2 O, CO 2 , N 2 and CH 4 , while that in Stage III FIs contains predominantly H 2 O. Stage I FIs are of L-, V-, C1-, C2- and S-types. These FIs homogenized mainly at 300–380 °C, and their salinities are bimodal (1.7–8.4 wt% and 35.2–45.8 wt% NaCl eqv.). Our results suggest that Stage I fluids belong to a NaCl–H 2 O–CO 2 ± CH 4 system characterized by medium-to-high temperature and salinity. Stage II FIs are of L-, V- and C2-types, with homogenization temperatures and salinities of 180.4–302.8 °C and 2.23–5.70 wt% NaCl eqv., respectively. Stage II fluids belong to a NaCl–H 2 O–CO 2 system featured by medium-to-low temperature and low salinity. Stage III FIs contain only L-type, with homogenization temperatures and salinities of 125.5–244.6 °C and 2.56–4.94 wt% NaCl eqv., respectively. Stage III fluids belong to a NaCl-H 2 O system characterized by low temperature and salinity. The δ18O fluid and δD fluid values of quartz and calcite are of −4.70 to 5.50‰ and − 144.8 to −121.8‰, respectively, indicating that the Hua'naote early-ore fluids were mainly derived from the magma with minor meteoric water input. The Hua'naote sulfides have δ34S CDT = −0.3 to 8.2‰ (mainly 0–2‰ and 5–8‰), and 206Pb/204Pb = 18.304–18.483, 207Pb/204Pb = 15.552–15.683 and 208Pb/204Pb = 38.104–38.350. The sulfur and lead isotope evidence suggests that the ore metals were sourced primarily from deep-seated magma with minor upper crustal input. We suggest that the Hua'naote Ag-Pb-Zn deposit is best classified as intrusion-related, fractures-controlled medium-temperature hydrothermal vein-type deposit. [Display omitted] • Hua'naote is a Triassic hydrothermal vein-type Pb-Zn deposit in northern China. • Fluid inclusion and H-O isotopes suggest mainly magma and minor meteoric water source for ore-fluids. • S-Pb isotopes indicate that the ore-forming materials were supplied by both the mantle and minor the upper crust. [ABSTRACT FROM AUTHOR]

• The Shenshan deposit is a newly discovered skarn Fe–Cu deposit located in the Great Xing'an Range in Northeast China. • The Shenshan granodiorite is intimately associated with the Shenshan Fe–Cu mineralization in the Jurassic. • The host-rock granodiorite was derived from partial melting of thickened mafic lower crust. • The metals were derived from the granodiorite, whose formation was related to closure of the Mongol–Okhotsk Ocean during the Jurassic. The newly-discovered Shenshan Fe–Cu skarn deposit is located in the southern Great Xing'an Range of northeastern China. The mineralization occurs mainly in the exoskarn or marble wallrocks of the Permian Zhesi Formation, which were intruded by the Shenshan granodiorite and granite porphyry dykes. Molybdenite Re–Os dating yielded a weighted mean age of 160.2 ± 2.4 Ma (MSWD = 0.38), consistent with the LA–ICP–MS zircon U–Pb age of the granodiorite (161.6 ± 2.2 Ma; MSWD = 0.75), but significantly older than the granite porphyry dykes (132.8 ± 1.9 Ma; MSWD = 0.87). This suggests a coeval and causative relationship between the granodiorite and Fe–Cu mineralization. The Shenshan granodiorite has an adakite-like geochemical signature with high Sr contents (704–871 ppm), and high Sr/Y (46.79–80.21) and (La/Yb) N (17.54–31.13) ratios, but low Y (9.7–13.1 ppm) and Yb (0.70–1.18 ppm) contents. The granodiorite has relatively low contents of Mg (1.71–1.94 wt%), Cr (18–23 ppm), and Ni (4.1–9.0 ppm), and positive ε Hf (t) (−0.3 to 3.0, average 1.51), yielding two-stage model ages (T DM2) of 1.38–1.68 Ga (average 1.51 Ga). The results indicate that the parental magmas of the granodiorite were derived from partial melting of juvenile thickened lower crust with minor mantle-derived input. Meanwhile, the Shenshan granite porphyry dykes are high-K calc-alkalic and weakly peraluminous, with low MgO (0.21–0.24 wt%) and Mg# (19–21). The dykes exhibit HFSE (e.g., Nb, Ta) depletions and LILEs (e.g., Rb, K) enrichments, and strong to moderate negative Eu anomalies, indicating major continental crust-derived input in the magma source. Geochemical and Hf isotopic data compilation for granitoids across the Great Xing'an Range indicate that the mineralization at Shenshan was influenced by the south-dipping subduction of the Mongol–Okhotsk oceanic plate. The discovery of adakite-like rocks in the Shenshan Fe–Cu deposit, and the voluminous adakite-like rocks in the region, suggest that the Mesozoic Great Xing'an Range has considerable prospecting potential for Cu–Au–Mo deposits. [ABSTRACT FROM AUTHOR]