The Yelonggou granite-pegmatite-type lithium deposit in the Ke'eryin orefield, western Sichuan, is situated on the southeastern margin of the Songpan-Ganze orogenic belt. To precisely determine the magmatic-mineralization age and reveal its coupling relationship with the magmatic-fluid evolution, this study conducted systematic microstructure observations, electron probe microanalysis, and U-Pb isotopic dating of coltan (Col) from the No. 25 lithium-rich granite pegmatite. The results indicate that columbite-tantalite can be classified into two types based on mineral structure and composition: (1) Col-Ⅰ, characterized by a homogeneous and unzoned structure, with low Ta# values (Ta/(Nb+Ta), atomic ratio) ranging from 0.19 to 0.31, belonging to the columbite-ferrosanite series and of magmatic origin; (2) Col-Ⅱ, exhibiting complex dissolution, replacement, and embayment structures, composed of Col-Ⅱa domains with darker backscattered electron (BSE) brightness and lower Ta# values (0.13-0.30), and Col-Ⅱb domains with brighter BSE brightness and higher Ta# values (0.27-0.65). Among them, Col-Ⅱa represents the residual parts of Col-Ⅰ after alteration, while Col-Ⅱb belongs to the columbite-tantalite-tapiolite series and is the product of metasomatism of early Col-Ⅰ by F- and Ta-rich fluids during the late stage of granite-pegmatite magma evolution. U-Pb isotopic analysis reveals no significant difference in isotopic composition between magmatic and metasomatic columbite-tantalite, yielding a weighted mean age of 195.1±3.6 Ma. This age constrains the formation of the No. 25 lithium-rich granite pegmatite to the Late Triassic-Early Jurassic, consistent with the formation ages of other rare metal granite pegmatites in the Songpan-Ganze giant rare metal metallogenic belt. Integrated geochemical and geochronological evidence indicates that the formation of the No. 25 lithium-rich granite pegmatite at Yelonggou involved an early magmatic crystallization stage and a late magmatic-hydrothermal alteration stage.