LAUSR

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 sub-continental mantle domains and their geochemical heterogeneities. Basalts with ocean island basalt (OIB)-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 pyroxenitic mantle. NCC rifting stage basalts exhibit anomalously low MgO and Fe2O3T and high SiO2 and Al2O3, as well as low Dy/Yb and Y/Yb and high eHf at a given eNd, as compared to the post-rifting 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 MTZ. Based on the chemical signatures of post-rifting 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.