Distinctive heavy rare earth element enrichment in granites of South China: Perspectives from geochemical signatures of Chinese granitoids

Heavy rare earth elements (HREEs) are critical metals that face significant supply risks, with current production dominated by ion-adsorption−type HREE deposits (IAHREDs) in South China. A fundamental prerequisite for IAHRED formation is HREE enrichment in parent granites, yet whether granites in South China are distinct from those elsewhere remains unclear. Here we address this question by analyzing the chemical compositions of 762 granites across China. Spatial analysis reveals that HREE enrichment is overwhelmingly concentrated in South China, particularly in the Nanling region, and coincides closely with known IAHREDs. The HREE-rich granites are peraluminous, high-K calc-alkaline, and characterized by low CaO/Na2O ratios as well as elevated Rb/Ba and Rb/Sr ratios, indicating derivation from partial melting of clay-rich metasedimentary protoliths. Low Nb/Ta and Zr/Hf ratios and pronounced negative δEu anomalies document extensive magma evolution, during which fractional crystallization of LREE-rich minerals progressively enhanced HREE enrichment in late-stage melts. The extensional setting in South China facilitated crustal melting and prolonged differentiation. We propose that the unique combination of favorable source composition, extensional tectonics, and sustained differentiation—converging in South China—produced the distinctive HREE-rich granites that serve as protoliths for IAHREDs. This study demonstrates that South China’s exceptional HREE mineralization is not coincidental, and the resulting geochemical signatures provide robust criteria for identifying granites with high IAHRED potential, offering a predictive framework for exploring critical HREE resources globally.