Paleo- to Mesoproterozoic Magmatic Rock Assemblage and Crust-Mantle Geodynamic Processes

Abstract

The late Paleoproterozoic to Mesoproterozoic crust-mantle geodynamic evolution of North China Craton remains hotly debated, which have largely hampered our further understanding of the Precambrian tectonic evolution of North China Craton as well as the reconstruction of this ancient craton within global Columbia supercontinent. In this chapter, whole-rock geochemical and zircon U–Pb and Lu–Hf isotopic studies are conducted on the late Paleoproterozoic magmatic rocks in the Western Liaoning-Northeastern Hebei Provinces, particularly the Jianping diorite-monzonite-syenite suite (JDMSS) and the Pinggu K-rich volcanic rocks within the Changcheng Group, as well as the newly discovered ~1.23 Ga mafic dykes. It is suggested that the JDMSS suite were emplaced during ~1721–1696 Ma, and they were generated by the partial melting of an amphibole-bearing enriched subcontinental lithospheric mantle, with the parental magmas subjected to different degrees of fractional crystallization. In comparison, the Pinggu K-rich volcanic rocks in the Tuanshanzi and Dahongyu Formations of Changcheng Group were erupted during ~1671–1625 Ma, and they were considered to have been derived dominantly from the partial melting of a depleted asthenospheric mantle, with the melts interacted with the lithospheric mantle components at diverse extents. These late Paleoproterozoic extension-related magmatism occurred later than the final amalgamation between the Eastern Block and Western Block (~1.85 Ga) along the Trans-North China Orogen, suggesting that they may have in turn evolved under post-collisional to post-orogenic settings. The newly discovered ~1.23 Ga mafic dykes occur widely in Western Liaoning, Eastern Hebei, and Northern Liaoning. Together with coeval mafic dykes identified in other areas of the North China Craton, these mafic dykes constitute a Mesoproterozoic large igneous province (LIP) covering an area of at least 0.6 × 106 km2. It is suggested that they were generated by extensive asthenosphere-lithospheric mantle interaction processes, possibly linked to a mantle plume event that triggered the final breakup of global Columbia supercontinent. Importantly, the late Paleoproterozoic enriched lithospheric mantle beneath the North China Craton witnessed at least two major episodes of intense erosion and rejuvenation by the upwelling asthenospheric mantle during the Proterozoic time.