Understanding the Yanshan volcano eruption in the Chaihe–Arxan volcanic field, northeastern China

The Chaihe–Arxan volcanic field is situated in the Greater Khingan Range of northeastern China. The volcanic field consists of over 40 monogenetic cones. Yanshan is the youngest volcano in this area, with a reported age of 2 ky BP. The regions surrounding the volcano was subjected to a large fire in 2006, allowing researchers to determine the eruption history of the volcano. During a 2-week comprehensive field investigation, we found Yanshan volcano exhibits three types of eruption products: pyroclastic blanket, multi-crater scoria cone, and lava flow. The eruption process of this volcano has since concluded. Its eruption activity was initially ambiguous Strombolian eruption of the north crater, followed by sub-Plinian eruption of the east crater, and finally lava flow effusive events from the west crater. The Yanshan basalts are composed of trachybasalt and basalt. Geochemical analyses for major and trace elements suggest that the Yanshan basalts do not undergo significant crustal contamination but undergo olivine and pyroxene crystallization. Experimental melt calculations and the La/Yb versus Sm/Yb diagram indicate that the Yanshan basalts are derived from the melting of garnet peridotite. The Sm/Yb versus Na/Ti diagram illustrates that the initial melting depth beneath Yanshan is approximately 140 km, and the lithospheric thickness is approximately 70 km. These results support the existence of a high-temperature and fluid-rich plume at a depth of 10–12 km beneath the youngest volcanic chain where Yanshan is located, indicating the possibility of eruption of this volcano. Therefore, it is necessary to strengthen volcanic monitoring at Yanshan.