New insights into potassic intraplate volcanism in Northeast China from joint tomography of ambient noise and teleseismic surface waves

Wudalianchi volcano is one of the youngest volcanic groups among the Cenozoic intraplate volcanoes in Northeast China and is notable for its potassium-rich basalts. With newly deployed dense broadband seismic stations, we construct a high-resolution 3-D S-wave velocity model of Wudalianchi volcano and its adjacent region, including the Keluo and Erkeshan volcanoes, using ambient noise and teleseismic surface wave tomography. We find a prominent channel-like low-velocity body that extends from the Moho to a depth of 100 km directly beneath the Wudalianchi, Erkeshan, and Keluo (WEK) volcanoes. This low-velocity anomaly suggests that these three volcanoes may be derived from the same mantle magmatic source. Our model also shows that the prominent low-velocity anomaly is associated with the pervasive low-velocity anomalies at a depth of 100–200 km, which is interpreted as the asthenosphere. We further find that the lithosphere beneath the WEK volcanoes thickens abruptly from ∼80 to ∼110 km. Combining our results with those of other geophysical studies, we propose a geodynamic scenario for WEK intraplate volcanism. When the background asthenospheric flow in Northeast China encounters sharp changes in lithosphere thickness beneath the WEK volcanoes, it produces locally turbulent flow, promotes asthenospheric upwelling, and finally forms volcanoes.