Nature, composition, enrichment processes and its mechanism of the Mesozoic lithospheric mantle beneath the southeastern North China Craton

Abstract

This paper aims to constrain the nature and composition of the Mesozoic lithospheric mantle beneath the southeastern North China Craton on the basis of a systematic review on the temporal and spatial distribution and geochemical features of Mesozoic mantle-derived magmatism in the region, and to further understand the temporal and spatial evolution, enrichment processes and its mechanism of the lithosphere through the comparison with the Mesozoic lithospheric mantle beneath the central, i. e. Luzhong region. Sr-Nd-Pb isotopic features of mantle-derived rocks imply that apparently temporal and spatial heterogeneity of the Mesozoic lithospheric mantle existed beneath the eastern North China Craton, the mantle under the central North China Craton, i. e the Luzhong region was dominantly slightly enriched and that under the southeastern North China Craton such as Luxi and Jiaodong region was EM2-like ( 87Sr/ 86Sr i up to 0. 7114). It is also apparent that the Mesozoic lithospheric mantle beneath the southeastern North China Craton evolved with time. These geochemical features of mantle-derived rocks and compositional and textural characteristics of the basalt-borne mantle xenoliths (peridotites and pyroxenites) and xenocrysts (olivine and pyroxene) demonstrate that the Mesozoic lithospheric mantle beneath the southeastern North China Craton was severely affected by the silica-rich melts. Reaction between lithospheric peridotite and infiltrated melt was considered to be an important type of lithospheric reconstruction and transformation, which led to the transformation of the Paleozoic high-Mg # peridotite to late Mesozoic low-Mg # peridotite and pyroxenite. Influx of melts into the lithospheric mantle, which had the geochemical characteristics of partial melting of the lower/middle crust, resulted in rapid enrichment of the late Mesozoic lithospheric mantle beneath the southeastern North China Craton. Relevant scientific issues such as the timing, processes and its mechanism of Mesozoic lithospheric thinning and reconstruction of the eastern North China Craton have also been discussed.