Tectonic extension and pre-enrichment of REEs in the southern margin of the North China Craton during late Paleoproterozoic: Evidence from geochemistry and Lu-Hf-Nd isotopes of Longwangzhuang REE-bearing granite

• Precise zircon U-Pb age (∼1.6 Ga) for the Longwangzhuang REE-bearing granite. • Paleoproterozoic pre-enrichment and Devonian hydrothermal remobilization. • A2-type granite derived from ancient crust in an intraplate extensional setting. • Provides new metallogenic insights for REE exploration in the SNCC. The timing, petrogenesis, and tectonic setting of the Paleo–Mesoproterozoic (∼1.6 Ga) alkaline magmatism and associated rare earth element (REE) mineralization in the southern North China Craton (SNCC) remain contentious. The Longwangzhuang (LWZ) deposit is a recently discovered REE deposit in the SNCC. It is hosted within the region’s largest Late Paleoproterozoic granite pluton, namely the LWZ REE-bearing granite. In this study, we present an integrated study of zircon U-Pb geochronology, whole-rock geochemistry, and Sm-Nd and zircon Lu-Hf isotopes on the LWZ REE-bearing granite. Zircon U-Pb dating yields a crystallization age of 1613 ± 6 Ma, implying that the pre-enrichment of REEs occurred in the late Paleoproterozoic. The granite exhibits A-type characteristics, including high SiO 2 , alkalis, and FeO T /(FeO T + MgO) ratios, with strong enrichment in LREEs and strong negative Eu anomalies. Whole-rock ε Nd ( t ) values range from –6.2 to –4.9, and zircon ε Hf ( t ) values vary from –4.8 to +0.8, indicating derivation primarily from the partial melting of ancient Mesoarchean crustal sources (Taihua Group). Geochemical tectonic discrimination diagrams consistently suggest an intraplate extensional setting. We conclude that the LWZ A-type granite formed during the Columbia supercontinent breakup. The primary enrichment of REEs was governed by extensive fractional crystallization of the magma, with late-stage hydrothermal activity contributing to the final ore-grade mineralization. This study not only clarifies the origin of the LWZ granite but also establishes a link between Proterozoic intracontinental rifting and REE metallogeny in the SNCC