Deep geophysical anomalies beneath the Changbaishan Volcano

Abstract

Subsurface imaging is key to understanding the origin of intraplate volcanos. The Changbaishan volcano, located about 2000 km away from the western Pacific subduction zone, has several debated origins. To investigate this, we compared regional seismic tomography with the electrical resistivity results and performed high-resolution 1D and quasi-2D velocity-depth profiles. We show that the upper mantle is characterized by two anomalies exhibiting distinct features which cannot be explained by the same mechanism. We document a localized low-velocity anomaly atop the 410-km discontinuity, where the P-wave velocity is reduced more than that of the S-wave (i.e., low Vp/Vs). We propose that this anomaly is caused by the reduction of the effective moduli during the phase transformation of olivine. The other anomaly, located between 300 km and 370 km depth, reveals a significant reduction of the S-wave velocity (i.e., high Vp/Vs), associated with a reduction of the electrical resistivity, altogether consistent with partial melting.

Deep Geophysical Anomalies Beneath the Changbaishan Volcano

“…Seismic stations used in this study are described in Zheng et al. (2010), https://doi.org/10.1785/0120090257, and the waveform data are freely accessible in the Zenodo repository (https://doi.org/10.5281/zenodo.7102579) (Li, Li, et al., 2022).…”

Seismicity and Magmatic System of the Changbaishan Intraplate Volcano in East Asia

“…In contrast, V s is mostly affected by the fluid phase or partial melts. Therefore, a large amount of partial melts and high‐temperature zones in the magma chamber would significantly influence the shear strength of surrounding rocks but affect the compressive strength modestly due to the hydration of crystal lattices or grain boundaries (Kasatkina et al., 2014; Koulakov et al., 2021; Li et al., 2023; Toomey et al., 1998). In addition, the high‐ V p anomaly might indicate that the magma chamber has been partially crystallized, which is similar to a high‐velocity layer revealed beneath the Datong volcano (He et al., 2021).…”

Upper mantle melt caused by a subducted slab in the Indian-Eurasian continental subduction zone

“…The LVLs are characterised by thicknesses of 56-94 km and P-wave velocity drops of −2.8 to −4.7%. This cannot be explained by the phase transition of serpentine into dense hydrous magnesium silicate 35 , nor can it be explained by the phase transformation of olivine 36 . Similar LVLs are found worldwide [5][6][7][8][9][10][11][12][13][14][15] , and these results are usually explained as being caused by partial melting induced by water and/or other volatiles (i.e.…”