Crust–Mantle Evolution beneath the Korean Peninsula Constrained by Temperature and Composition Estimated from Uppermost Mantle Tomography

Dynamic processes operating at continental plate margins, including associated igneous activity, lead to progressive reactivation and modification of the lithosphere and are recorded in the evolving structure of the continental crust. Crustal evolution is strongly controlled by crust–mantle interaction at the Moho, where changes in temperature, composition, and density can be induced by underplating or lithospheric destruction. Consequently, the Moho represents a critical interface at which continental growth, mechanical weakening, and lithospheric removal may occur. Seismic imaging of the uppermost mantle therefore provides direct constraints on the processes governing lithospheric evolution. In this study, we present three-dimensional P- and S-wave tomography of the uppermost mantle beneath the southern Korean Peninsula, derived from Moho-refracted waves. The tomographic models are used to estimate thermal and compositional variations by comparing observed seismic velocities with petrological predictions. A basalt–harzburgite mechanical mixture (MM) was adopted as the baseline model, while an equilibrium assemblage (EA) and an orthopyroxene (Opx)-enriched mantle were additionally considered to evaluate the effects of compositional variability on seismic velocities.

The results showed pronounced regional contrasts in seismic velocity, temperature, and composition. The Gyeonggi Massif and Gyeongsang Basin are characterized by relatively low Vp (≈7.65 km/s) and low Vp/Vs (≈1.73), consistent with a hot, harzburgite-rich mantle and a thin lithosphere. In contrast, the Yeongnam Massif exhibits high Vp (≈7.89 km/s) and high Vp/Vs (≈1.76), indicating a relatively cold mantle with a higher basaltic fraction (40%) within a thick lithosphere. These characteristics are consistent with independent constraints on lithospheric thickness. The hot and thinned harzburgite-dominated mantle is interpreted as the result of lithospheric modification by delamination or thermal erosion. In contrast, basaltic components preserved within the cold and thick lithosphere are interpreted as basaltic underplating associated with Mesozoic subduction, maintained by a stabilized lithospheric root. However, the combination of low Vp (≈7.65 km/s) and exceptionally low Vp/Vs (≈1.70) observed in the western Gyeonggi Massif cannot be explained by either the MM or EA models, whose minimum Vp/Vs values are 1.74 and 1.73, respectively. This discrepancy requires anomalous mantle conditions, such as strong Opx enrichment or pronounced seismic anisotropy. Despite their close spatial proximity, these contrasting mantle properties indicate that distinct geological processes operated beneath different regions of the Korean Peninsula during the Mesozoic–Cenozoic, and that the resulting thermal and compositional signatures are preserved in the uppermost mantle.