Chronology, geochemistry and isotopic compositions of the Cretaceous Zhangjiakou diabase: Magmatic derivation and geodynamic implications

Zircon U–Pb ages, major and trace elements and Sr–Nd–Hf isotope data of the diabase in the Zhangjiakou district were studied to investigate its derivation and tectonic implications. Zircon U–Pb ages indicate that the diabase was emplaced at ~130 Ma or younger, and captured zircons cluster at ~147 Ma, ~240 Ma, ~430 Ma and ~465 Ma. The diabase is characterized by minor variations in SiO2 (49.35–52.10 wt.%), TiO2 (1.65–1.77 wt.%), Al2O3 (17.00–18.26 wt.%), MgO (4.28–4.93 wt.%), CaO (6.69–7.90 wt.%) and Mg# (48–54). It has no significant Eu anomaly and displays enrichment in large ion lithophile elements (Rb, Ba and Sr) and depletion in high field strength elements (Nb, Ta, P and Ti). The diabase exhibits homogeneous Sr ((87Sr/86Sr)i = 0.70606–0.70701) and Nd (εNd(t) =–13.6 to –13.2) isotopic compositions. These features suggest that the parental magma was derived from partial melting of the ancient lower crust, relating to mantle upwelling that triggered by stagnant slabs or lithospheric detachment associated with the westward subduction of the Paleo-Pacific Plate. The Early Paleozoic inherited igneous zircons in the diabase suggest that the northern margin of the North China Craton (NCC) likely underwent southward subduction of the Paleo-Asian Ocean.