Geochronology and geochemistry of Early Cretaceous volcanic rocks in the Erlian Basin, NE China: implications for the late Mesozoic tectonic transformation of East Asia

Abstract

ABSTRACT The formation and distribution of late Mesozoic volcanic rocks in northeast (NE) China remain unclear due to the superimposed influence of the tectonic regimes of the Mongol–Okhotsk Ocean (MOO) and Palaeo-Pacific Ocean (PPO) in Northeast Asia. This study reports the petrogenesis and tectonic settings of Early Cretaceous volcanic rocks from the Erlian Basin (EB) using petrology, geochronology, whole-rock geochemistry, and Sr–Nd–Hf isotopes. The U–Pb data for the magmatic zircons indicate that the volcanic rocks, including the trachytic rocks and rhyolites, erupted approximately at ~141–135 Ma. Trachytic rocks and rhyolites exhibit comparatively high SiO2 (58.74–65.77 wt. % and 71.35–72.99 wt. %, respectively) and alkali content, low Mg values (mean 25 and 24, respectively), and Cr, Co, and Ni contents, which differ from the geochemical characteristics of mantle-derived magmas. Furthermore, the positive ε Hf(t) (1.7–10.5) and ε Nd(t) (2.4–2.9) values of trachytic rocks and the positive ε Hf(t) values (4.3–6.6) of rhyolites indicate that these rocks were derived from the partial melting of the juvenile crustal materials. The relatively homogeneous zircon Hf isotopes and systematic variation of major and trace elements in these coeval volcanic rocks suggest that they have a common magma source and resulted from the development of the parent magma in the crustal magma chamber. Our results, combined with previous studies, demonstrate that Early Cretaceous volcanism in the EB records an extensional tectonic regime caused by lithospheric delamination after the closure of the MOO. During the Late Cretaceous, NE China was predominantly controlled by the PPO tectonic regime, accompanied by overall uplift and denudation of large-scale faulted basin groups.