Petrogenesis of the Tailaihua ore-forming granites in the southern Great Xing’an Range, NE China: Implications for magma evolution and Be-Nb-Ta mineralization in Late Mesozoic

• Late Jurassic to Cretaceous highly fractionated I-type granites in the Tailaihua region. • Magmatic volatiles and fractional crystallization led to the enrichment of rare metals • Fluid-melt interactions induced the tetrad effect and large-scale rare metal mineralization. The dynamic interplay between melt evolution and fluid activity plays a crucial role in rare metal enrichment in highly fractionated granites, yet the specific mechanisms remain inadequately understood. This study explores the recently discovered Tailaihua Be–Nb–Ta deposit in the southern Great Xing’an Range (SGXR) to elucidate these processes. By integrating monazite U–Pb geochronology, whole-rock geochemistry, and electron probe microanalysis (EPMA) of major minerals, we establish a comprehensive magmatic-hydrothermal evolution sequence and explores the behavioral dynamics of melt-fluid interactions within highly differentiated granitic systems exhibiting Be-Nb-Ta mineralization. LA-ICP-MS U-Pb dating of Tailaihua ore-forming granite yielded ages of 143.4 ± 1.9 Ma for the monzonitic granite (MG), 142.1 ± 2.3 Ma for the alkali-feldspathic granite (AFG), and 140.0 ± 3.0 Ma for the albite granite (AG). Tailaihua ore-forming granites are characterized by high SiO 2 , Al 2 O 3 , alkalis (K 2 O + Na 2 O), and A/CNK ratios (>1.1), with depleted CaO, MgO, FeO T , indicating high-K peraluminous compositions. Trace elements show Rb-Th-U-Ta enrichment and Sr-Ba-Eu depletion, confirming intense fractionation of I-type magmas, accompanied by REE tetrad effects. Progressive crystal fractionation of biotite, K-feldspar, and plagioclase within the MG-AFG-AG sequence drove magma evolution. Our key finding reveals that extreme rare metal enrichment resulted from a two-stage process: initial magmatic concentration through fractional crystallization, followed by significant hydrothermal remobilization driven by volatile exsolution (H 2 O–F). This second stage induced pervasive metasomatism and characteristic REE tetrad effects. This study quantitatively links magma differentiation to ore formation, offering a robust model for exploring similar rare-metal deposits.