The Yanshanian granites widely distributed in Southern Jiangxi serve as important metallogenic hosts for granite-type rare metal deposits. Taking the Jiangkengli Nb-Ta deposit in Shicheng as the research object, this study systematically compares the geochemical differences between mineralized and non-mineralized granites through field geological surveys, petrographic analysis, whole-rock geochemical testing, and U-Pb chronology. The results show that the mineralized granites are predominantly sodic calc-alkaline series, which are significantly enriched in Al₂O₃, ^TFe₂O₃, and MnO compared with non-mineralized granites. They are characterized by low total rare earth elements (ΣREE<20×10^-6), low Nb/Ta (<3), low Zr/Hf (<5), and high Rb/Sr (>150), based on which quantitative discrimination indices for mineralized granites are established. Isotopic chronology reveals that the monazite U-Pb age of zinnwaldite-albite granite is 144.9±0.8 Ma. Combined with regional metallogenic age comparisons, it is inferred that 145~140 Ma represents a unique Nb-Ta mineralization period in Southern Jiangxi. The ore-forming mechanism indicates that the deposit formed through the synergistic evolution of highly differentiated magma and F/Li- rich fluid alteration. This study provides key geological references for rare metal prospecting in Southern Jiangxi.