Thermal, compositional, and rheological structures of the lithosphere beneath the Changbaishan volcanic field and their controls on volcanic activity

The Changbaishan volcanic field (CVF), situated in the southeastern Central Asian Orogenic Belt, hosts a Cenozoic volcanic group including Changbaishan, Longgang, and Jingpohu volcanoes which exhibit distinct activities and surface rock compositions. To understand factors controlling their different behaviors, it is important to conduct integrated analysis of lithospheric thermal, compositional, and rheological structures. Here, we employ a probabilistic joint inversion incorporating surface heat flow, topography, geoid heights and Rayleigh wave phase and group velocity dispersion data to construct the thermal, compositional, and rheological structures of the lithosphere beneath the CVF. Joint inversion results indicate that lithospheric thickness beneath Changbaishan and Longgang volcanoes (~55 km) is significantly thinner than that beneath Jingpohu volcano (~85 km). In addition, a pronounced ~200 km wide asthenospheric thermal anomaly exists beneath the Changbaishan volcano, while it is absent beneath Longgang and Jingpohu volcanoes. Crustal compositions beneath the Changbaishan volcano are dominated by felsic rocks, while they are restricted to the lower crust beneath Jingpohu. Rheological weakening (viscosity <10²¹ Pa·s) extends from the crust to the upper mantle beneath the Changbaishan volcano, whereas the Jingpohu volcano exhibits weak zones only in the lower crust. We propose that the Changbaishan volcano retains a multilevel magmatic system linking the asthenosphere to the shallow crust, sustaining its high activity and diverse eruptive rocks. In contrast, Longgang and Jingpohu volcanoes lack sustained mantle-crust connectivity, resulting in low activity and predominantly alkali basalt eruptions.