Abstract: Siliceousrocks of the Middle Permian Chetou Formation in Qianshan County, Jiangxi Province, are found to host several layers of tuff. By studying the zircon U-Pb age andLu-Hf isotopic compositions of tuff, this paper discussed the time of submarinevolcanic eruption, and diagenetic environment and diagenetic provenance. LA-ICP-MS zircon U-Pb weighted average age of tuff is 264.8±4.4Ma, indicating thatitformed in the extensional platform-basin environment of continental margin. This can serve as the direct proof to illustrate the occurrence of submarine volcanic eruption during this period. Two-phase Lu-Hf isotopic model age of tuff is1170～1670 Ma(average 1320 Ma), suggesting the Proterozoic age and representing that the diagenetic source may be associated with regional crustal remelting hyperplasia.