Abstract: The Neoproterozoic magmatic rocks in the northern margin of the Yangtze plate exhibit a wide distribution range and a high degree of diversity, and are significantly affected by multi-stage magmatic-tectonic thermal activities. The tuffaceous rhyolite of the Tiechuanshan Formation exhibits porphyritic and fine structure, developing rhyolite structure in the process. The geochemical characteristics of tuffaceous rhyolite indicate that it belongs to the calc-alkaline series of volcanic rocks, which have undergone a certain degree of differentiation and evolution. The rocks in the magma source area are primarily composed of continental crust. The ΣREE (138 ppm~181 ppm) is in close proximity to the average value of the continental crust, and the range of K₂O is 2.42 wt.%~3.23 wt.%. There is a weak negative Eu anomaly, with an Eu/ Eu^* range of 0.50~0.64, and the Mg^# value is low (36.8~45), which collectively suggests the characteristics of a thickened lower crust source. The ratio of light and heavy rare earth elements varies from 3.61 to 4.23, indicating the presence of notable fractionation between these two groups of elements. The range of (La/Sm)_N is 2.53~4.75, indicating that the degree of fractionation of light rare earth is significant and the degree of enrichment is high. The variation range of (La/Yb)_N is 2.67~3.73, indicating that it is formed in the geological environment of dehydration and melting of rocks in the source area under high pressure at the bottom of the continental crust. The ratio of trace elements suggests that the source is the crust and that the formation is more closely related to the lower crust. In light of the source discrimination diagram of tuffaceous rhyolite in the Shenmen area, it can be posited that the tuffaceous rhyolite was formed as a result of partial melting of the new mafic lower crust, which may have been influenced by fluid metasomatism of the subducted slab. When considered alongside the source discrimination diagram of tuffaceous rhyolite in the Shenmen area, the tuffaceous rhyolite in the Shenmen area evinces the typical geochemical characteristics of island arc granite. This is indicative of the fact that island arc granite is the product of an island arc environment under the background of subduction extrusion.