To reveal the deep structure of the granitic- pegmatitic type lithium and other rare metal mineral systems, amagnetotelluric (MT) survey was conducted in the Dahongliutan area of the West Kunlun orogenic belt. Through 3D resistivity inversion of the MT data, two high- resistivity bodies were detected within the depth range of 0~20 km, reflecting the large- scale felsic magma and the partially concealed eastern granite basement of Dahongliutan. Additionally, a widespread high- conductivity anomaly observed at depths of 20~80 km reflects the large- scale felsic magma reservoir formed by crustal remelting extending deep into the upper mantle. The mineralization host rocks, the granite basement of Dahongliutan, are shown to be rooted and represent a massive magma reservoir extending deep into the upper mantle, providing the source materials and heat for the formation of the giant Dahongliutan granitic- pegmatitic type lithium deposit. In comparison with the Songpan- Ganzi Jiajika super- large granitic- pegmatitic type lithium deposit, although the exposed granite in Jiajika is limited, the 3D resistivity inversion model of the MT data also reveals a widespread high- conductivity anomaly extending into the upper mantle, indicating the presence of a large- scale felsic magma reservoir. The difference lies in the shallower erosion depth in Jiajika, where the overlying granite intrusion has not been eroded. Therefore, Dahongliutan exhibits a “hot dome” feature with extensive granite outcrops resulting from deep erosional processes, while Jiajika represents a “gneiss dome” feature with the country rocks surrounding the granite subjected to thermal metamorphism. The giant ore belt of rare metal mineralization, including lithium, in Western Kunlun- Songpan- Ganzi, which hosts two super- large deposits of late Triassic age at its ends, is the product of large- scale crustal remelting and felsic magmatism. The saturation of H2O is a key factor in the exceptional enrichment of lithium and other rare metals in the granitic- pegmatitic type lithium deposits. Moreover, the “pre- enrichment” of lithium during different stages of differentiation and evolution in the felsic magma reservoir, intrusive granites, and pegmatites lays an essential foundation for the formation of massive granitic- pegmatitic type lithium deposits.