Magmatic–Hydrothermal Evolution of Li Mineralization in Leucogranite from the Mufushan Complex, Central China

Leucogranites commonly record the coupled effects of magmatic differentiation and hydrothermal reworking, both of which play critical roles in Li enrichment. To constrain the petrogenesis and Li, Rb mineralization of the Mufushan muscovite monzogranite, a leucogranitic intrusion in central China, we conducted an integrated study of petrography, zircon, monazite, and apatite U–Pb geochronology, whole-rock geochemistry, and mineral chemistry. Magmatic zircon and monazite analyzed by LA-ICP-MS yielded concordant crystallization ages of 134.8 ± 1.7 Ma and 133.9 ± 0.4 Ma, respectively, indicating Early Cretaceous emplacement. U–Pb dating of monazite and apatite from Li-mineralized domains yielded younger ages of 129.5 ± 1.3 Ma and 127.6 ± 9.2 Ma, respectively, which are interpreted as recording a subsequent magmatic–hydrothermal remobilization event. The muscovite monzogranite is characterized by high SiO2 of 73.09%–75.18% and Al2O3 of 14.46%–15.59%, elevated K2O/Na2O ratios of 0.83–1.02, low Mg# values of 11.8–20.7, strong peraluminosity with A/CNK values of 1.20–1.39, and a high-K calc-alkaline affinity. It also displays high differentiation indices (D.I. = 90.85–93.25), pronounced negative Eu anomalies (Eu/Eu* = 0.09–0.38), and enrichment in Rb (439–653 ppm), Ta (4.2–17.2 ppm) and Pb (0.36–28.7 ppm), together with depletion in K, Sr, Eu, P, and Ti. These geochemical characteristics collectively indicate extensive magmatic differentiation. The muscovite monzogranite can therefore be classified as a highly fractionated S-type granite. It was most likely generated by partial melting of argillaceous continental crust and represented a latest-stage, high-SiO2 residual melt extracted from a long-lived granitic magma reservoir after repeated melt segregation. We propose a two-stage genetic model for Li, Rb mineralization involving: (1) fractional crystallization and repeated melt extraction from parental S-type granitic magma, followed by (2) hydrothermal remobilization. Fluorine-rich magmatic–hydrothermal fluids exsolved from highly evolved melts likely played a critical role in Li enrichment.