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The Middle Triassic Laojiagou porphyry Mo deposit is located in the Xilamulun metallogenic belt, along the northern margin of the North China Craton (NCC). Molybdenum mineralization is associated with a monzogranite porphyry and occurs primarily in quartz veins and veinlets hosted in wall rocks affected by potassic, silicic, sericitic, and propylitic alteration. The ore-forming process is divided into three stages, characterized by veinlets comprising molybdenite + pyrite + quartz (stage I), pyrite + chalcopyrite + molybdenite + quartz (stage II), and pyrite + quartz (sulfide-poor) (stage III). We identify three fluid inclusion types in quartz grains: carbonic (C-type), liquid-rich two-phase (L-type), and rare vapor-rich two-phase (V-type) inclusions. Microthermometric results indicate that an initial high-temperature (> 350 °C) and low-salinity (< 10 wt% NaCl equiv.) CO2-rich fluid evolved to a low-temperature (< 280 °C) and CO2-poor fluid, comprising dominantly of meteoric water. Hydrogen and oxygen isotopes indicate that initial ore-forming fluids were magmatic and became progressively mixed with meteoric water (stage I δ18OH2O = 4.4–4.8‰ and δDH2O = − 105.8 to − 101.5‰). Zircon U–Pb dating indicates that the monzogranite porphyry formed at 232.2 ± 3.6 Ma (MSWD = 0.88). The porphyry has high SiO2, K2O, and Al2O3 and low MgO and CaO concentrations and is classified as high-K calc-alkaline and weakly peraluminous. All samples are enriched in light rare earth and large-ion lithophile elements and depleted in high-field-strength elements. Our results indicate that the Laojiagou porphyry Mo deposit formed in the Middle Triassic, associated with post-orogenic extension following closure of the Palaeo-Asian Ocean. [ABSTRACT FROM AUTHOR]

The Angeer Yinwula Pb-Zn deposit of Inner Mongolia, China, is located in the Erlianhot-Dongwuqi metallogenic belt, which is considered to be the eastern part of the Central Asian Orogenic Belt. We used the ore geology, fluid inclusion, isotopes, and zircon U-Pb geochronology to elucidate the genesis and tectonic setting of the deposit. The deposit belongs to the moderate-temperature hydrothermal-vein type, and most of the ore bodies occurred in the quartz diorite intrusions and silty slate country rocks of the Devonian Angeer Yinwula Group. Fluid inclusion petrography and microthermometry results show that the inclusions that developed in the different mineralization stages changed from the LV type (vapor-rich two-phase) + S type (daughter-mineral-bearing three-phase) + VL type (liquid-rich two-phase) to the VL type + LV type and eventually evolved into the VL type, and the ore-forming fluids changed from a moderate-temperature and moderate- to high-salinity, boiling fluid system to a low-temperature and low-salinity H2O-NaCl system. The isotope (C, H, O, S) characteristics suggest that the ore-forming fluids were derived from a magmatic source, and the lead was derived from a deep-seated mantle-derived magma and also included some crustal material. The LA-ICP-MS zircon U-Pb age of the quartz diorite is 152.0 ± 1.5 Ma, which is the best estimate for the age of mineralization of the deposit. Overall, we suggest that the deposit formed in a Late Jurassic Paleo-Pacific Plate subduction setting, although this hypothesis needs to be further tested by conducting computational simulations in the field of emerging computational geosciences. [ABSTRACT FROM AUTHOR]