Rapid and concentrated magmatism and mineralization of rare-metal granites: Evidence from the Limu deposit, South China

Rare metals, including W, Sn, Nb, Ta, and Li, are strategic resources essential for advanced manufacturing, clean energy, and defense technologies. In-situ isotopic dating of ore minerals directly constrains rare-metal mineralization timing, which could provide essential information for ore-forming process. The Limu rare-metal granite is a representative granite-type Nb–Ta deposit in South China and occurs as several small stocks (∼1 km 2 ), including muscovite granite, Li–phengite granite, and zinnwaldite/lepidolite–albite granite. Previous studies proposed a prolonged magmatic evolution from ∼ 240 to ∼ 200 Ma, longer than that of most batholiths, with controversial ages derived from different methods, leaving its precise chronological framework unresolved. Here we conducted in situ U–Pb/U–Th–Pb dating on zircon, monazite, cassiterite, columbite-group minerals (CGM), and wolframite from 19 granite samples collected from seven localities in the Limu ore field: Paoshuiling, Jinzhuyuan, Xiangtanling, Niulanling, Daqiling, Laohutou, and Shuiximiao. The results constrain the formation of the Limu rare-metal granite to 212.6 ± 4.4 Ma–207.8 ± 2.3 Ma, with a peak at approximately 210 Ma. Integration of new whole–rock geochemical data (n = 17), previously published datasets (n = 51), and zircon trace element analyses shows that granites from Jinzhuyuan, Laohutou, and Shuiximiao are the most evolved, whereas those from Daqiling and Niulanling represent more primitive end-members. These results define a precise temporal framework, indicating that the separate stocks formed within a short interval (∼5 Myr) through fractional crystallization and prompting a reevaluation of the magmatic and metallogenic evolution of the Limu rare-metal granite, with broader implications for dating comparable highly fractionated granites and granite-type rare-metal deposits worldwide.