P–T–t evolution of garnet-spinel-corundum pelitic granulite from the Odaesan Complex, Korea: Implications for Permian–Triassic metamorphism along the northeastern Eurasian margin

초록

We reconstruct the pressure–temperature–time (P–T–t) evolution of garnet–spinel–corundum pelitic granulite intercalated between migmatitic gneiss and garnet amphibolite in the Odaesan Complex, eastern Gyeonggi Massif, Korea, using mineral chemistry, phase equilibrium modeling, geothermobarometers, zircon U–Pb and REE analyses. Garnet core isopleths indicate earlier conditions of ∼9.5–11.5 kbar and ∼ 600 °C, followed by decompressional heating to ∼7–9 kbar and 700–760 °C, where garnet, spinel, and corundum were stable. Subsequent near-isobaric cooling at ∼7.5–8.0 kbar and 605–635 °C defines a clockwise P–T path. Low-Th/U zircon overgrowths dated at 253–229 Ma show steep HREE-enriched patterns, indicating growth or recrystallization during Permian–Triassic metamorphic re-equilibration, asynchronous with major garnet growth. The P–T path contrasts with published paths for the migmatitic gneiss and garnet amphibolite, likely reflecting lithology-dependent preservation and re-equilibration, although diachronous metamorphism or cryptic tectonic juxtaposition cannot be excluded. Decompressional heating records hot exhumation of thickened lower crust. This path, spatially heterogeneous metamorphism, Odaesan mangerite–gabbro magmatism, and adakitic magmatism in the northeastern Yeongnam Massif indicate greater tectono-thermal complexity than envisaged by the Hongseong–Odaesan Collision Belt model. These records favor crustal thickening, diachronous exhumation and thermal re-equilibration, and episodic deep thermal input within a regionally extensive, long-lived subduction–arc system along the northeastern Eurasian margin. Within this framework, the Odaesan Complex and Oki Belt in southwest Japan may preserve related records of crustal evolution and Permian–Triassic tectono-magmatic reworking. © 2026 Elsevier B.V.

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