The Chaijiagou Mo deposit (0.11 Mt Mo @ 0.07%) is located along the northern margin of the North China Craton. This study integrates ore geology, S–Pb–He–Ar–H–O isotopes, and fluid inclusion (FI) analyses to constrain the sources of ore-forming fluids and metals, as well as mineralization mechanisms. Three principal inclusion types were identified: liquid-rich, vapor-rich, and saline FIs. Microthermometry documents a progressive decline in homogenization temperatures and salinities from early to late mineralization stages: Stage 1 (360–450 °C; 5.3–11.3 and 35.4–51.5 wt.% NaCl equation), Stages 2.1–2.2 (320–380 °C and 260–340 °C; 5.4–11.8 and 33.8–44.5 wt.% NaCl equation), and Stage 4 (140–200 °C; 0.4–3.9 wt.% NaCl equation). Noble gas and stable isotope data reveal that the ore-forming fluids were initially dominated by crustally derived magmatic–hydrothermal components with a minor mantle contribution, subsequently experiencing significant meteoric water input. S–Pb isotopic compositions demonstrate a genetic relationship between mineralization and the ore-bearing granite porphyry, indicating a magmatic origin for both sulfur and lead. Fluid–rock interactions and fluid boiling were the dominant controls on molybdenite and chalcopyrite deposition during Stage 2, whereas mixing with meteoric waters triggered galena and sphalerite precipitation in Stage 3.

Experimental studies have confirmed the permeability reduction of coal samples upon the adsorption of CO₂. However, these studies were carried out under limited experimental conditions. In this study, CO₂ flow behaviors in a macro-scale coal sample were numerically simulated using a coupled gas flow, mechanical deformation, and sorption-induced deformation finite element model. The simulation results show that the effect of the reduction of effective stress on the enhancement of permeability is greater than the negative effect of permeability reduction due to CO₂ adsorption for low injection pressures. CO₂ pressure development in the sample increases with increasing injection pressure due to the enhanced advection flux for sub-critical CO₂ injections, while for super-critical CO₂ injections, CO₂ pressure development, as well as concentrations in the sample, decreases compared to sub-critical CO₂ injections because of greater density and viscosity of super-critical CO₂ as well as coal matrix swelling induced by the adsorption of super-critical CO₂. Increasing axial stress (buried depth) obstructs CO₂ migration in the sample due to the increased effective stress, and this effect is more influential for low injection pressures, which indicates that high CO₂ injection pressures are preferred for CO₂ sequestration in deep coal seams.

Deep coal seams are generally preferred for CO₂ sequestration, during which the saturation fluids and high-stress condition involved can significantly alter the mechanical attributes of coal. To understand the effect of stress conditions on the mechanical properties of coal during CO₂ sequestration, a finite element model was developed and subsequently validated using experimental data. The results indicate that coal strength increases from 10.35% for a 5 MPa CO₂-saturated sample to 114.54% for an 8 MPa CO₂ + water-saturated sample as the confining pressure rises from 0 to 30 MPa, due to reduced porosity. However, this effect diminishes with higher confining pressures as dilation decreases. The critical confining pressure determined in this study is approximately 20 MPa, at which all samples exhibit similar failure strength (around 48.50 MPa). Moreover, the strengthening effect caused by applied stress is especially pronounced in CO₂-saturated samples, particularly in those saturated with super-critical CO₂ and CO₂ + water. This suggests that the reduction in coal strength resulting from the adsorption of saturation fluids can be counterbalanced by the strength gain resulting from applied stress. The aforementioned results highlight the effectiveness of injecting high-pressure super-critical CO₂ into deep coal seams for carbon sequestration purposes.

Sulfide geochemistry has been widely employed to constrain formation processes in various deposit types; however, its use in porphyry W-Mo metallogenic systems is still relatively scarce. The Sansheng porphyry W-Mo deposit (Mo 24,361 t @ 0.226% and WO₃ 17,285 t @ 0.569%), situated in eastern Inner Mongolia, northeastern China, features with quartz vein and veinlet-disseminated W-Mo orebodies primarily localized within the cupolas of an Early Cretaceous granitic intrusion. This contribution provides a comprehensive analysis of the deposit’s geology, in situ sulfur isotopic signatures, and geochemical characteristics of wolframite and sulfides to decipher the formation of the Sansheng deposit. A narrow δ³⁴S range (2.15‰–7.14‰) for sulfides, consistent Y/Ho (5.09–6.23) and Nb/Ta (7.20–19.96) ratios in wolframite, and pyrite Co/Ni (1–10) and As/Ni (>10) ratios collectively point to a shared source—the highly fractionated Sansheng granitic magma. Wolframite, pyrite, arsenopyrite, and chalcopyrite all host significant trace elements, though their enrichment patterns differ considerably among these minerals. Temporal variations in trace element concentrations in wolframite and sulfides reveal a decline in fluid temperature and oxygen fugacity from early to late stages. Greisenization is associated with tungsten mineralization, whereas sericitization facilitates Stage III sulfide precipitation.