Precambrian Crustal Evolution, Lithospheric Mantle Evolution and Crust-Mantle Geodynamics of Western Liaoning-Northeastern Hebei Provinces

Abstract

How the Precambrian lithospheric mantle formed as well as related crust-mantle geodynamic regimes remain hotly debated, which eventually controlled the Precambrian crustal formation and evolution processes. Based on the studies of Archean to Mesoproterozoic geological events in the Western Liaoning-Northeastern Hebei Provinces, the prolonged evolution history of the lithospheric mantle and crust-mantle geodynamic processes are summarized and discussed in this chapter. The Precambrian lithospheric mantle evolution history of the study area is established as follows: (1) the juvenile depleted Neoarchean lithospheric mantle was generated by “lateral” subduction accretion processes along the northern margin of North China Craton, which was gradually evolved to an enriched mantle during Paleoproterozoic; (2) this enriched mantle was further metasomatized by slab-derived materials during late Paleoproterozoic eastward subduction processes of Trans-North China Orogen, resulting in the formation of a potassic and enriched lithospheric mantle; and (3) at ~1671–1625 Ma and ~1230 Ma, this enriched lithospheric mantle witnessed two episodes of “vertical” accretion processes, which were ascribed to asthenospheric mantle upwelling processes triggered by lithosphere delamination and a mantle plume activity, respectively. The Western Liaoning-Northeastern Hebei Provinces experienced prolonged Precambrian crust-mantle geodynamic evolution history: (1) at ~2640–2506 Ma, the depleted lithospheric mantle was initially generated by mid-ocean ridge spreading, yielding mid-ocean ridge basalts (MORBs). This juvenile lithospheric mantle was continuously metasomatized by subduction-related fluids and melts, the partial melting of which generated the island arc tholeiites and calc-alkaline basalts, adakite-like and high magnesium andesites, as well as HMG granitoid gneisses in the Western Liaoning Province. Meanwhile, the underplating of mantle-derived materials triggered partial melting of the metabasaltic rocks at the arc-root, resulting in the formation of LMG TTG gneisses; (2) at ~2495 Ma, partial melting of the metamorphosed felsic and sedimentary rocks was induced by the mantle upwelling in an extensional setting following arc-continent accretion, leading to regional granulite-facies metamorphism and the emplacement of potassium-rich granitoid gneisses; (3) during the Paleoproterozoic, the metasomatized Archean lithospheric mantle was gradually evolved to an enriched mantle source through close-system isotopic evolution, which was further metasomatized by slab-derived fluids or melts during the late Paleoproterozoic Trans-North China Orogen, resulting in the formation of a potassic and enriched lithospheric mantle. At ~1780–1680 Ma, the partial melting of this enriched mantle occurred in response to slab breakoff, yielding voluminous igneous rocks such as JDMSS, AMGRS, and mafic dykes; (4) later at ~1670–1625 Ma, the asthenospheric mantle upwelled and melted following the lithosphere delamination, resulting in the eruption of Pinggu volcanic rocks in the Yanliao rift; and (5) during the early to middle Mesoproterozoic, long-term tectonic quiescence dominated the NCC. However, ~1230 Ma mantle plume triggered the partial melting of asthenospheric mantle with intense asthenosphere-lithospheric mantle interaction, yielding voluminous mafic dykes throughout the NCC.