The Permian Emeishan Large Igneous Province represents the aftermath of the most significant Phanerozoic volcanic eruption in China. Recent petroleum exploration within the middle Permian system of the Sichuan Basin has unveiled novel volcaniclastic architectures in the Chengdu-Jianyang Area, situated at the northernmost edge of the Emeishan Large Igneous Province. This study introduces a comprehensive interpretation of the lithology and petrography of these architectures, identifying three primary lithological series: the ignimbrite series, the autoclastic series, and the agglomerate series within the reservoir section. It is proposed that these series originate from terrestrial pyroclastic flows, autobrecciation of effusive lavas, and Strombolian-Hawaiian fire fountaining spattering, respectively. These mechanisms are conclusively established for the first time in this region. The predominant pore spaces within these lithologies are characterized by dissolved and intercrystalline pores formed during alteration processes. The genesis of these lithologies imposes essential constraints on the formation of pore spaces, primarily due to: (1) the production of significant juvenile clasts by these mechanisms; (2) the clastic support of the volcaniclasts maintaining substantial initial porosity and permeability, facilitating hydrothermal fluid interaction with the clast framework; and (3) their proximity to volcanic vents, suggesting accumulation under atypical thermal gradients, leading to heightened activity of altering fluids. These factors culminate in substantial rock framework alteration, laying the groundwork for the development of extensive volcanic petroleum reservoirs.