Abstract: The Yinshan deposit is a typical hydrothermal copper polymetallic deposit in Dexing, Jiangxi Province. The Yinshan volcanic activities are composed of three volcanic eruption cycles, i.e. rhyolitic, dacitic and andesitic assemblages in sequence. LA-ICP-MS zircon U-Pb dating for the three volcanic cycle rocks indicate that they were formed at 168.6~169.9 Ma, 168.5~171.4 Ma and 166 Ma, respectively, which is contemporary with the forming age of the ore-bearing porphyries in the Dexing copper mine, implying the metallogenic epoch of Middle Jurassic. The compositional variation of volcanic rocks from rhyodacite to dacitic and andesitic assemblages resulted from the compositional zonation within the magma chamber before eruption. The Yinshan volcanic rocks in different cycles show similar geochemical characteristics to the typical adakites in northeastern Jiangxi. All of them have high LREEs contents and depletion of HREEs, with low Ti, Na, high K, Al, Sr, Sr/Y and (La/Yb)_N ratios, and slightly negative Eu anomalies. Zircons from the samples have ε_Hf(t) values ranging from -1.98 to +5.49 and t_DM2 model ages from 0.84 to 1.31 Ga, indicating that the magma possibly derived from Meso-to Neo-Proterozoic juvenile continental crust formed by the Neoproterozoic oceanic crust subduction along the Jiangnan Orogen. Based on the geochemical and Hf isotopic data in this study and previous studies, we suggested that the Middle Jurassic adakitic rocks in Dexing and Yinshan might originate from the remelting of Meso-to Neo-Proterozoic arc rocks in the compressional setting. Conversely, Early Jurassic EW direction bimodal volcanic rocks in east section of Nanling Mountains were formed in the strong extensional setting of post-collision, suggesting two distinct tectonic settings of Middle Jurassic magmatism between northeast Jianxi and Nanling, and Early-Middle Jurassic is the critical period to understand the tectonic transition in South China.