<p>The Middle Jurassic Shaximiao Formation in the northwestern Sichuan Basin is widely developed with high-quality tight sandstone reservoirs. However, its provenance system has long been controversial, which has hindered the study of the formation mechanism of high-quality reservoirs. In order to clarify the provenance attribution of the tight sandstone in the Shaximiao Formation and reveal the influence mechanism of provenance evolution on the formation and evolution of tight sandstone reservoirs. This investigation focuses on the Shaximiao Formation in Zitong area of northwestern Sichuan Basin, conducting petrological and elemental geochemical analysis, which systematically analyzing the sedimentary provenance attribution and tectonic environment, and exploring the significance of provenance evolution for the formation of high-quality tight sandstone reservoirs. Analytical results demonstrate that the reservoirs are dominated by lithic arkose and feldspathic litharenite, characterized by moderate to well-sorted grains with metamorphic lithic fragments, ultra-low porosity (average 7.89%), and ultra-low permeability (average 0.36 × 10⁻³ µm²), where intergranular dissolution and residual pores constitute the primary storage spaces; Compaction, dissolution, and cementation play a crucial role in the pore structure and reservoir quality of tight sandstone; And the provenance discrimination and tectonic discrimination diagrams further limit that the tight sandstone provenance comes from the intermediate acidic felsic igneous rocks in the continental island arc environment. Therefore, based on the Indosinian-Yanshanian tectonic evolution of the Yangtze Block, it can be inferred that the source system rich in feldspar and metamorphic quartz in the Micangshan uplift dominated the sedimentation of tight sandstone in the Shaximiao Formation of northwestern Sichuan Basin. This provenance system critically influenced reservoir quality by regulating material composition and textural attributes (e.g., sorting, grain contacts), which further dictated porosity evolution and diagenetic pathways. Quartz and laumontite cementation played a pivotal role in preserving primary porosity during the early diagenetic stage, while mesodiagenetic feldspar dissolution (contributing 28.4% of secondary pores) and fracture-enhanced connectivity synergistically amplified permeability (avg. 0.36 × 10^− 3 µm²). These coupled processes, including the composition of detrital components driven by material sources and the evolution of diagenesis, collectively shape high-quality tight sandstone reservoirs in the Sichuan Basin and southern China, providing theoretical references for the study of similar reservoirs in continental arc environments.</p>