Potential HT-UHT metamorphic record of the North Dabie metamorphic belt: implications for the formation of the Dabie orogen

The Dabie orogenic belt (DOB) hosts the world’s largest HP–UHP terrane and records a complete continental deep-subduction process. However, the scale, intensity, and timing of post-peak HT–UHT thermal overprints remain controversial, hindering a comprehensive understanding of the orogen’s geodynamic evolution.We present a case study of calc-silicate granulites and pyroxene-plagioclase amphibolites from the NDMB, to constrain these late-stage events. Integrated field work, petrography, mineral chemistry, phase equilibrium modelling, and REE thermometry reveal three metamorphic stages: M1 (851°C / 1.06 GPa), M2‑UHT (996°C / 0.6 GPa), and M2 (664°C / 0.43 GPa). Combined with zircon and sphene U–Pb dating results, a retrograde P–T–t path has been constructed: M‑peak (900–1000°C / 4.0–5.0 GPa; 223–228 Ma) → M1 (201–204 Ma) → M2‑UHT (134 Ma-145 Ma) → M2 (129 Ma-132 Ma). This path reveals three retrograde processes: ①rapid cooling and decompression, ②pronounced heating with slow decompression, and ③ near-isobaric rapid cooling. Based on the P–T variations, exhumation rates, and tectonic background analyses, we infer that the DOB evolved under two tectonic regimes—Indosinian compression and Cretaceous extension—with the transition likely occurring during the Early Cretaceous.