Ore-forming process of the Zhengchong lithium deposit, Nanling Range: constraints from geochronology and mineral chemistry

• The Li content in micas is positively correlated with the evolutionary degree of granites. • The evolutionary degree of granitic magma controls Nb-Ta mineralization in the Nanling Metallogenic Belt. • The magma source region and its evolution jointly control W-Sn mineralization in the Nanling region. The Zhongchong lithium deposit, located within the Jinjiling pluton, is a representative large greisen-type lithium deposit in the Nanling metallogenic belt. To constrain its metallogenic age, we obtained 40 Ar– 39 Ar plateau and isochron ages of zinnwaldite (Fe–Li mica) of 152.1 ± 1.4 Ma and 151.6 ± 1.8 Ma, respectively, and a concordant cassiterite U–Pb age of 151.3 ± 2.6 Ma. These results are consistent, within error, with the emplacement age of the fine-grained porphyritic monzogranite (154–150 Ma), indicating that Li–Sn polymetallic mineralization in the Jiuyishan area occurred during the Early Yanshanian period. Two main granite types are developed in the Zhongchong deposit: medium- to coarse-grained porphyritic-like syenogranite and fine-grained porphyritic monzogranite. Geochemical analyses show that both granites are silica- and alkali-rich but depleted in Ca and Mg, with peraluminous to weakly peraluminous compositions (A/CNK = 0.98–1.19). The syenogranite contains significantly higher total REE contents than the monzogranite, with LREE-enriched, right-inclined patterns, whereas the latter exhibits a pronounced tetrad effect. Both granite types are enriched in Rb, K, Th, U, Nd, and Hf but depleted in Ba, Sr, Nb, and Ti, with the fine-grained monzogranite showing stronger enrichment–depletion signatures. These characteristics suggest that the syenogranite and monzogranite represent cumulates and residual melts derived from a common parental magma, with the latter showing higher degrees of differentiation and stronger rare-metal enrichment, thereby possessing greater metallogenic potential. Electron microprobe analyses of zinnwaldite from greisen ores in the Zhongchong deposit are presented in this study. The results show that micas from the medium- to coarse-grained syenogranite, fine-grained monzogranite, greisen, and quartz veins display consistent geochemical trends: SiO 2 correlates positively with Al 2 O 3 , MnO, and K 2 O, but negatively with TiO 2 , FeO, MgO, and Na 2 O, indicating progressively enhanced magmatic differentiation. Trioctahedral micas dominate the assemblage and define an evolutionary sequence from annite → ferroan biotite → siderophyllite → protolithionite → zinnwaldite → lepidolite, reflecting a clear trend toward lithium enrichment. In addition, mica compositions reveal that the magmatic–hydrothermal system evolved toward higher oxygen fugacity from early to late stages, which facilitated the migration and re-enrichment of multivalent elements. By integrating geological, geochronological, and geochemical evidence, we propose a genetic model for the Zhongchong lithium deposit, providing important guidance for rare-metal exploration in the Nanling region.