The diagenetic processes of volcanic rocks differ markedly from those of clastic rocks. The Mesozoic volcanic rocks in the Zhanxi area underwent multi-phase diagenetic evolution involving tectonic, magmatic, and hydrothermal interactions. Based on structural analysis, hydrothermal filling charracteristics, and diagenetic mineral identification, the diagenetic sequence of these volcanic rocks was reconstructed. During the Yanshanian NW-trending compression along the Tanshu Fault Zone, intense volcanic eruptions formed a complex dominated by dense blocky basalt and porphyritic andesite. Following solidification, the volcanic rocks experienced two stages of hydrothermal activity and one stage of hydrocarbon-induced dissolution and filling. The reservoir properties of these lithologies vary significantly due to their contrasting diagenetic pathways. Andesite underwent a sequence of zeolite filling-calcite precipitation-chloritization-ferrocalcite replacement; basalt experienced chloritization-siliceous filling-ferrodolomite precipitation; and volcanic breccia followed clastic accumulation-chlorite lining-ferrodolomite cementation. Scoria porosity and permeability decreased markedly due to cementation, whereas basalt retained relatively high permeability despite primary porosity loss, and andesite exhibited minimal reservoir alteration. Near the Zhanan Fault, the basalt fracture system serves as a migration pathway for hydrocarbons, while dissolution cavities in andesite provide storage space. Scoria 's poor reservoir quality results from hydrothermal cementation, whereas the composite zone of basaltic fractures and andesitic alteration forms a favorable hydrocarbon enrichment area.