Mesozoic magmatism in the eastern North China Craton: Insights on tectonic cycles associated with progressive craton destruction

Abstract

The North China Craton (NCC) provides a classic example for lithospheric thinning associated with craton destruction (or decratonization) through multiple tectonic events. The peak of craton destruction is considered to have occurred during Mesozoic, especially in Early Cretaceous, linked to the subduction/collision between the NCC and Yangtze Craton during the Triassic in the south and the Paleo-Pacific plate subduction during Early Cretaceous in the east. Here we investigate a suite of intrusive and volcanic suites including granite, gabbro, diorite, basalt, andesite, volcanic tuff, agglomerate, siliceous tuff and trachyte from the southern Yishui and Juxian domains to gain insights into the Mesozoic tectonic evolution of the eastern NCC in relation to decratonization. Zircon U-Pb data from basalt show multiple populations with xenocrystic grains ranging in age from Paleoproterozoic (2457–1940 Ma), through Neoproterozoic (896–559 Ma), to Paleozoic (442–380 Ma) and Mesozoic (204–122 Ma). Inherited grains from the granite and gabbro yield weight mean 206Pb/238U ages of 650.0 ± 13 to 773.4 ± 2.6 Ma suggesting the involvement of components from the Yangtze Craton. Magmatic zircons from diorite show weight mean 206Pb/238U ages of 121.5 ± 1.2 Ma representing the emplacement age of this rock. Magmatic zircon grains from the volcanic suite (andesite, volcanic tuff, agglomerate, siliceous tuff and trachyte), show weighted mean 206Pb/238U ages of 132.4 ± 1.4 Ma, 123.02 ± 0.71 Ma, 122.97 ± 0.69 Ma, 121.96 ± 0.49 Ma, and 124.6 ± 1.1 Ma respectively, corresponding to the timings of their eruption. The Paleoproterozoic zircon grains correspond to xenocrysts captured from the NCC basement rocks, whereas the Neoproterozoic and Paleozoic grains were inherited from the Yangtze Craton. The Late Triassic to Jurassic zircon grains can be correlated to delamination of the thickened continental crust during deep subduction of Yangtze continental crust and the continent-continent collision between NCC and the Yangtze Craton. The Early Cretaceous population can be linked to the subduction of the Paleo-Pacific plate from the east and related extensional setting. The geochemical data display significant enrichment in LREE along with negative Eu anomalies, with high Th/Ta and La/Nb ratios, negative Nb–Ta anomalies, and high concentration of LILE (K, Rb, Ba and Pb) than HFSE (Nb, Ta and Ti), suggesting subduction-related arc magmatic setting in an active continental margin. Zircon Lu-Hf data from these rocks display dominantly negative εHf(t) values ranging from −36.8 to −3.1, TDM in the range of 1105–2572 Ma, and TDMC between 1785 Ma and 3776 Ma, indicating that the magma sources involved Paleoproterozoic components with minor input of reworked Archean crust through different degrees of enrichment with crustal material and minor input from extension-related mantle melting. In conjunction with the results from previous studies in the eastern NCC, we propose that the late Paleozoic southward subduction of the Paleo-Asian Ocean, the Triassic northward subduction and collision of the Yangtze Craton with the NCC, and the Early Cretaceous westward subduction of the Paleo-Pacific plate jointly contributed to the cratonic destruction of NCC. The Paleo-Pacific plate subduction beneath the NCC (major contributing mechanism) with the slab rollback induced lithospheric extension likely facilitated back-arc spreading, asthenospheric upwelling resulting in lithospheric thinning including delamination, melting of lithosphere mantle, and underplating of the modified mantle beneath the lower crust of the NCC during the Early Cretaceous.