Regional Zoning of a Li-Cs-Ta Pegmatite Field: Insights from Monazite-Cheralite Chemistry, U-Th-Pb and Sm-Nd Isotopes.

This article focuses on the mineralogical, geochronological, and isotopic study of Li-Cs-Ta (LCT) rare-element pegmatites in the Renli-Chuanziyuan pegmatite field, South China, to understand their evolution and rare-metal mineralization. The field exhibits four spatially zoned pegmatite types (K-, K-Na-, Na-, and Na-Li-zones) derived from a chemically zoned parental granitic magma dated at ca. 140 Ma, with monazite and cheralite minerals providing U-Th-Pb and Sm-Nd isotopic ages and geochemical data. Results indicate that the pegmatite zones share a common Neoproterozoic South China crustal source and evolved through Rayleigh-type fractional crystallization, with fluid-aided alteration affecting isotopic systems in some minerals. The study concludes that the regional pegmatite zonation reflects progressive fractionation of a single parental magma rather than multiple sources or melting events.