Evolution of the mantle beneath the eastern North China Craton during the Cenozoic: Linking geochemical and geophysical observations. Issue 1 (21st January 2017) - Li, Hong‐Yan
Abstract: Recent discoveries related to the geochemistry of Cenozoic basalts and the geophysics of the deep mantle beneath eastern Eurasia make it possible to place constraints on the relationship between the seismic tomography of subcontinental mantle domains and their geochemical heterogeneities. Basalts with ocean island basalt‐like trace elements erupted during (56–23 Ma) and after (≤23 Ma) rifting of the eastern North China Craton (NCC) show evidence for the mixing of an isotopically depleted source and an EMI (Enriched mantle type I) pyroxenitic mantle. NCC rifting‐stage basalts exhibit anomalously low MgO and Fe2 O3 T and high SiO2 and Al2 O3, as well as low Dy/Yb and Y/Yb and high ε Hf at a given ε Nd, as compared to the postrifting basalts. Temporal compositional variations and their association with basin subsidence indicate that heterogeneity in the eastern NCC asthenospheric mantle is the primary driver for intraplate magmatism in this region. The specific magmatic sources shifted in terms of depth, related to lithospheric thinning and thickening in the eastern NCC. The NCC EMI mantle domain most likely developed due to ancient events, is persistent through time, and is not related to dehydration of the stagnant Pacific slab in the mantle transition zone. Based on the chemical signatures of postrifting basalts, contributions from the Pacific slab are likely to be carbonatite rich. Mantle metasomatism by carbonatite melts from the Pacific slab and the interaction of these melts at shallower depths with EMI pyroxenitic mantle domains to trigger melting are contributors to the observed low P wave velocity zone beneath eastern Eurasia. Key Points: The asthenospheric mantle beneath the eastern NCC is stratified Lithospheric thinning/thickening of the eastern NCC induced shift of magma source The low‐velocity mantle domains beneath the eastern NCC are related to metasomatism by carbonatite