Late Mesozoic intraplate rhyolitic volcanism in the North China Craton: Far-field effect of the westward subduction of the Paleo-Pacific Plate

摘要

The Late Mesozoic was characterized by extensive volcanism, crustal extension, lithospheric thinning, and craton destruction in the North China Craton (NCC). Here we investigate the petrology, whole-rock geochemistry, zircon U-Pb geochronology, and Lu-Hf isotope of rhyolitic rocks from the Chicheng region of China along the northern margin of the NCC to constrain their petrogenesis, magma evolution, and associated geodynamic processes. The newly obtained zircon U-Pb age data constrain the eruption age of rhyolitic rocks at ca. 144-114 Ma during the Early Cretaceous with multiple magmatic pulses at ca. 141, ca. 137, and ca. 130 Ma as defined by the age peaks. Zircon Hf isotopic data show markedly negative epsilon(Hf)(t) values of -23.0 to -11.8, and corresponding Hf crustal model ages (T-DM(C)) are in the range of ca. 2650 to 1944 Ma, suggesting magma derivation through melting of Paleoproterozoic crustal materials with minor input of reworked Neoarchean components. Geochemically, the rhyolitic rocks correspond to A-type granites, with a mixed arc- and subduction-related signature, although generated in an extensional intraplate setting through partial melting of the mafic lower crust and upper crustal fractional crystallization. We correlate the late Mesozoic intraplate volcanism to the westward subduction of the Paleo-Pacific Plate and its far-field effect. Lithospheric extension and slab rollback of the Paleo-Pacific Plate are considered as the main triggers for the multiple eruptions. The late Mesozoic vol-canism in the study area and adjacent regions also broadly coincide with the tectonic transition from the Paleozoic Paleo-Asian to Mesozoic Paleo-Pacific subduction realm with concomitant compressional to extensional tectonic regime.