Recycled Oceanic Crust in the Source of the Intraplate Changbaishan-Tianchi Volcano, China/North Korea

Continental intraplate volcano is an ideal probe to unravel the composition and structure of the deep Earth. The intraplate Changbaishan-Tianchi volcano was one of the most hazardous eruptions on the Earth's planet. The long-term activity of this volcano from the Pleistocene to 946 CE has erupted materials with a broad compositional range from basalt to rhyolite, which are expected to be associated with the continuous northeastward subduction of the Pacific plate, but the magma source remains controversial. In this paper, we present a comprehensive data set of in situ zircon Hf and O isotope data, combined with whole-rock element and Sr-Nd-Pb isotope compositions, for selected eruptions of the Changbaishan-Tianchi volcano, aiming to provide new insights into their magma source and the associated geodynamics. Radiogenic isotopic ratios and incompatible trace element compositions indicate that the erupted volcanic rocks at different stages, although with a varied differentiation degree, were derived from a common magma source characterized by a mixture of DM and EM1 end-members. Zircon Hf and O isotopes are both relatively homogeneous for different lithologies and eruption stages, with the ε_Hf(t) values varying between −5 and +5, and δ¹⁸O values between 3.58‰ and 5.97‰. Modeling of source mixing indicates that high-temperature altered oceanic crust materials are an important component in the source of Changbaishan-Tianchi volcano, likely derived from an ancient stagnant slab that has been reactivated by the subduction of the Pacific plate. This study demonstrates that the recycling of deeply subducted oceanic crust is potentially an important source and trigger for continental intraplate volcanism.