Petrogenesis and uranium metallogenic potential of Caledonian and Indosinian granites from the Jinguanchong uranium deposit in Mingyuefeng area, eastern Hunan, South China Block

• Late Ordovician (444.2 ± 4.9 Ma) S-type granites found in Mingyuefeng, eastern Hunan. • Caledonian & Indosinian granites derived from metapelite-rich crust with minor mantle input. • Indosinian granites have higher U (8.40-21.88 ppm), lower Th/U, better for uranium. • Target Indosinian intrusions in SCB for uranium exploration. The Jinguanchong U deposit in eastern Hunan, South China Block (SCB), represents a critical locality for investigating granite-related uranium mineralization. This study integrates zircon U-Pb geochronology, whole-rock geochemistry, and Lu-Hf isotopes to characterize Caledonian and Indosinian granites and assess their uranium metallogenic potential. LA-ICP-MS zircon U-Pb dating reveals two distinct granitic suites: (1) Late Ordovician Caledonian biotite granite (444.2 ± 4.9 Ma), exhibiting strong peraluminosity (A/CNK = 3.1–3.42), high SiO 2 (avg. 75.42 wt%), and weak negative Eu anomalies (Eu/Eu*=0.74–0.88, avg. 0.82); and (2) Late Triassic Indosinian biotite monzogranite (234.5 ± 2.1 Ma), characterized by elevated alkalis (Na 2 O + K 2 O = 6.22–8.27 wt%), moderate peraluminosity (A/CNK = 1.08–1.56), and pronounced negative Eu anomalies (Eu/Eu*=0.24–0.54, avg. 0.31). Both suites are classified as S-type granites derived from partial melting of metapelite-dominated crustal sources with subordinate metagreywacke components, as evidenced by CaO/Na 2 O and Rb/Sr ratios and Paleoproterozoic zircon Hf model ages (T DM2 = 1479–1729 Ma and 1516–2577 Ma, respectively). Minor mantle input is suggested for both suite. Comparative analysis with known uranium-bearing granites in the SCB demonstrates that the Indosinian granite possesses superior uranium fertility, evidenced by significantly higher U contents (8.40–21.88 ppm, avg. 12.67 ppm), lower Th/U ratios (0.50–1.47, avg. 0.95), and favorable mineralization indices (e.g., L 1 , L 2 , X). In contrast, the Caledonian granite shows lower U content (3.05–3.63 ppm) and higher Th/U ratios (5.69–6.29), indicating limited uranium potential. Field relationships confirm uranium mineralization is spatially associated with the Indosinian granite. This study identifies the Indosinian granites as the primary uranium source in the Mingyuefeng district and highlights their exploration significance in analogous geological settings within the SCB.