Early Paleozoic alkaline magmatism extensively occurred in the South Qingling Block (SQB), forming a NW-SE trending alkaline rock belt composed of basic alkaline and trachytic rocks with elevated high-field-strength element (HFSE) and rare earth element (REE) concentrations. The Shuanghekou niobium (Nb) deposit is one of the trachyte-hosted Nb deposits recently found in the region. This study carried out an integrated investigation of the field geology, chronology, zircon Hf isotope, and whole-rock elemental and Nd isotopic analyses for the Shuanghekou deposit. Combined with compiled datasets for alkaline rocks in the Ziyang-Zhushan area, new results are employed to trace the Nb enrichment and mineralization processes. LA-ICP-MS zircon U Pb isotopic dating yields ages of 433 2 to 432 2 Ma, constraining the early Silurian eruption of the Shuanghekou trachytic rocks. Coupled with compiled eruption/intrusion ages, we recognize a large-scale alkaline magmatic event in the SQB during 440–430 Ma. The close relationship in space and time as well as comparable Nd Hf isotopic characteristics between the trachytic and the basic rocks indicate they are genetically related. The high fractionation of light and heavy REE, enrichment in HFSE, and moderately depleted Nd isotopic compositions indicate the ultimate derivation from a fertilized lithospheric mantle source metasomatized by asthenosphere-derived melts. Thermodynamic modeling using the rhyolite-MELTS program reproduces the evolution process from the basic to the trachytic rocks in the SQB through fractional crystallization of clinopyroxene, orthopyroxene, plagioclase, K-feldspar, magnetite, as well as minor olivine, ilmenite, and apatite. However, trace element modeling also reveals that fractional crystallization alone cannot explain the extreme enrichment of Nb and REE in the rocks. In the mineralized trachytic rocks, pervasive alteration features and the positive correlation between fluorine and Nb imply that hydrothermal metasomatism was the final step of rare metal mineralization. Our modeling indicates that, compared with plutonic systems, fluorine saturation in the melt occurs earlier in alkaline volcanic systems and contributes to a more intense superposition of hydrothermal mineralization. [Display omitted] • A large-scale alkaline magmatic event occurred in South Qingling during 440–430 Ma. • The trachytic and basic rocks derived from metasomatized mantle source. • The Nb-rich trachytic rocks evolved from coeval basic alkaline magma. • Hydrothermal metasomatism was indispensable in the rare-metal enrichment.