Middle–Late Permian E’erdengaobao Granitic Rocks in Damao Area: Constraints on Tectonic Transition Along the Northern Margin of the North China Craton

The timing and nature of the Late Paleozoic tectonic transition along the western northern margin of the North China Craton (NCC) remain debated because arc-related and post-collisional magmatism overlap in the Damao–Siziwangqi region. We present zircon U–Pb ages, in situ Lu–Hf isotopes, and whole-rock geochemistry for the E’erdengaobao granitic rocks in the Damao area. Zircon U–Pb dating yields crystallization ages of 266 ± 3 and 259 ± 2 Ma, documenting Middle–Late Permian granitic magmatism. The rocks are highly evolved, silica-rich, ferroan, weakly peraluminous granites with A-type-like geochemical features. Their A-type-like geochemical affinity occurs within strongly fractionated felsic compositions, as indicated by quantitative fractionation indices and pronounced Sr–Ba–Eu depletion. Predominantly negative zircon εHf(t) values (−11.75 to +1.84; 19 of 20 analyses are negative) and Paleoproterozoic two-stage Hf model ages (1.60–2.04 Ga) indicate substantial involvement of ancient crustal material during magma generation. Together with regional magmatic records, the 266–259 Ma E’erdengaobao granites are consistent with late-orogenic tectono-magmatic reorganization in eastern Damao during the terminal evolution of the Paleo-Asian Ocean. Their ages provide a local temporal constraint on Middle–Late Permian magmatism in this sector of the northern NCC margin, although the precise geodynamic mechanism responsible for this reorganization remains uncertain.