Abstract: The monzodiorite in the Tongjingshan area, Chuzhou, Anhui Province, is of great geological significance for unraveling the deep geological processes and crust-mantle interactions in the northern segment of the middle-lower reaches of Yangtze River. Zircon U-Pb dating yields an age of 131 Ma for this monzodiorite, which is comparable to the ages of ore-forming intermediate-acidic adakitic rocks and non-ore-forming intermediate-acidic rocks in the Zhangbaling Uplift Belt of the same area, but slightly younger than those of the Late Mesozoic Cu-Au ore-forming granites in the middle-lower reaches of Yangtze River. Geochemically, the studied samples have relatively high total alkali contents and belong to the high-K calc-alkaline series. They are enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs), yet depleted in high field strength elements (HFSEs).Zircon Hf isotope analyses reveal highly enriched compositions (ε_Hf(t) = −26 ～ −20) and ancient two-stage model ages (2.44～2.82 Ga), indicating that the monzodiorite was derived from the Archean-Paleoproterozoic basic lower crust of the Yangtze Craton. Additionally, the samples exhibit adakitic geochemical signatures (high Sr, low Y), relatively high Mg# values and MgO contents, along with the development of pyroxene core-rim textures. These features collectively suggest that the parental magma experienced a certain degree of contamination by the overlying mantle peridotite during its ascent. Calculations based on oxygen fugacity indices of zircon and apatite further demonstrate that the Tongjingshan monzodiorite formed in a relatively reduced petrogenetic environment, leading to limited mineralization potential. This distinguishes it from the coeval ore-forming granites with high oxygen fugacity in the region. This study provides key constraints on the material sources of intermediate-acidic magmatism and the nature of crust-mantle interaction in the northern middle-lower reaches of Yangtze River during the Late Mesozoic.