Seismic constraints on the magmatic system beneath the Changbaishan volcano: Insight into its origin and regional tectonics

There is a growing concern in recent years about the potential eruption of the Changbaishan volcano (CBV) which is located at the border between China and North Korea, but the magmatic system beneath this volcano remains hotly debated due to the lack of consistent geophysical constraints in the lithospheric structure. In this study, we construct a high-resolution 3-D crust and upper mantle S-wave velocity (Vs) model beneath the CBV and adjacent regions combining ambient noise and earthquake surface wave tomography. Two distinct low Vs anomalies are revealed: one in the lower crust ( 20-40 km) and the other in the upper mantle (>60-70 km). The lower crustal low-velocity body is interpreted to be the main magma reservoir that may feed the shallow localized magma chambers imaged with relatively weak low-velocity anomalies. The upper mantle low-velocity zone is representative of upwelling asthenosphere. The middle-to-lower crust beneath the Longgang volcano (LGV) and the lower crust beneath the Jingpohu volcano (JPHV) are also characterized by low Vs anomalies, might indicating low-degree partial melting. We propose that the intraplate volcanism of the CBV as well as the LGV and JPHV arises from the decompression melting of upwelling asthenosphere, which could further originate from the mantle transition zone as suggested by previous large-scale tomographic studies. Moreover, the geologically identified Solonker-Xar Moron-Changchun-Yanji suture zone is delineated by a prominent high Vs anomaly in the lowermost crust and uppermost mantle, which may be explained by the fossil slab remnants or deformational fabrics resulted from the final closure of the Paleo-Asian Ocean in the Late Paleozoic to Early Mesozoic.