Abstract: Global lithium deposits are primarily categorized into hard rock-type, brine-type, and clay-type, with the latter predominantly formed by weathering or leaching. A recent discovery in Jingde County, Anhui Province, revealed a hydrothermally altered clay-type lithium deposit, expanding the understanding of clay-type lithium mineralization. But the metallogenic process is not yet clear. This study aims to explore the metallogenic process and formation age of the Jingde lithium deposit through field surveys, major and trace element analyses, LA-ICP-MS in situ trace elements, and illite LA-ICP-MS in situ Rb-Sr dating. The findings indicate that the primary minerals in the ore include quartz, fluorite, kaolinite, illite, chlorite, and others, with clay minerals closely associated with fluorite and quartz. The lithium is predominantly hosted in kaolinite and illite with the content ranges from 6644-8265ppm and 5131-7034 ppm. The LA-ICP-MS signal map of kaolinite does not show any abnormal lithium peaks. Furthermore, a negative correlation is observed between the Li+Al content and the Si content, suggesting that lithium is mainly incorporated into the crystal structure of kaolinite and illite. The in situ Rb-Sr dating of Li-rich illite yields an age of 84.7±5.3 Ma, which corresponds to the metallogenic timing of lithium in this deposit. The metallogenic process of the Jingde lithium deposit is as follows: during the Late Cretaceous (84.7±5.3 Ma), the Pacific Plate subducted beneath the South China Plate. This led to the formation of highly differentiated granites that released Li- and F-rich acidic metallogenic fluids. These fluids infiltrated northwest- and northeast-trending faults in the Jingde region, undergoing hydrothermal alteration with granite and diorite. This process caused the breakdown of minerals such as feldspar, hornblende, and biotite, which contributed to the formation of clay minerals like kaolinite and illite, as well as fluorite. And lithium was incorporated into the structures of kaolinite and illite simultaneously. This study provides a crucial metallogenic age constraint for the formation of the Jingde hydrothermally altered clay-type lithium deposit and elucidates the genetic relationship between fluorite deposits and hydrothermally altered clay-type lithium deposits. It is anticipated that further breakthroughs in lithium prospecting could be achieved in fluorite-rich mining areas in the future.