The Tunxi Basin in southern Anhui Province, located in the eastern segment of the Jiangnan Orogenic Belt, exposes intermediate—acidic volcanic rocks of the Shiling Formation. The early- stage volcanism is dominated by rhyolitic tuff and trachyandesitic breccia, with zircon U- Pb ages of 150.8 ± 2.8 Ma and 156.1 ± 2.6 Ma respectively, indicating Late Jurassic volcanic rocks and the earliest stage of magmatic activity in the Mesozoic era in southern Anhui. Both types of rocks exhibit rich Si and K and low Mg characteristics, belonging to the high potassium calcium alkaline series. The distribution pattern of rare earth elements is right skewed, showing weak Eu negative anomalies, enriched whit large ion lithophile elements and light rare earth elements, and depleted in high field strength elements. At the same time, the rock mass has high Sr, Sr/Y, and (La/Yb)N values, which are characteristics of adakite. The range of εNd(t) values is -6.36~-4.92. The average formation temperatures of the two types of rocks obtained by zircon Ti thermometers are 763 ℃ and 795 ℃, respectively. Coarse andesite breccia is slightly higher, with a total average temperature of 785 ℃. Based on the geochemical characteristics of rocks and regional geological data, this article believes that the volcanic rocks of the Shiling Formation in the Tunxi Basin originated from a mixture of crustal and mantle magma. The crustal magma is a product of partial melting in the Neoproterozoic sedimentary rock source area, while the mantle magma originates from the mantle that has been replaced by material from subducting plates. It has a synchronous, homologous, and large- scale coupling relationship with the granodiorite in southern Anhui, and belongs to a volcanic intrusive complex system in a broad sense. Based on this, the Mesozoic magmatism in southern Anhui initiated with the Shiling Formation volcanics and minor intermediate—acidic intrusions, followed by large batholithic monzogranites and bimodal volcanics, and culminated with A- type K- feldspar granites. This tripartite evolution reflects the tectonic transition from low- angle subduction through slab rollback to renewed low- angle subduction of the Paleo- Pacific Plate.