Magma system and equilibrium depth of the Cenozoic basalts in the central North China craton

Variations of continental lithosphere thickness through time is crucial for understanding destruction and regrowth processes in the cratonic region. The North China craton (NCC) is well-known for its various degrees of destruction since ∼200 Ma: the eastern portion was significantly thinned to 60–80 km, while the western part remained thick (>160 km). Nevertheless, the variation of lithospheric thickness in the central NCC remains elusive. Here we use thermobarometers of both liquids and minerals (olivine and clinopyroxene) to estimate the equilibrium depths of Hebi alkaline basalts (6.4 Ma) and evaluate the thickness of lithosphere beneath the volcanic fields (with eruption ages of 30–0.1 Ma) of the central NCC. Results show that the lithospheric thickness is ∼90–100 km, thinner than the current estimated by seismic observations (90–130 km). This variation indicates that the central NCC's lithosphere underwent Mesozoic thinning and Cenozoic accretion. Olivine-dominated cumulates in melt pooling close beneath the lithosphere-asthenosphere boundary and the buoyant mantle residues might be key components that have contributed to the re-healing of the thinned lithosphere.