Reporters learned from the Chinese University of Science and Technology, the university’s Institute of Earth and Space Science, the Institute of Earthquakes and Earth’s Internal Physics Laboratory Professor Zhang Haijiang Research Group and the China Geological Survey Hydrogeological Environmental Geological Survey Center, the use of geomagnetic imaging, for the first time obtained the five Dalian pool volcanic region under the tail mountain volcano 20 kilometers deep three-dimensional high-resolution resistivity structure, and carefully depict the tail mountain volcano crustal magma system distribution pattern, estimated the melting degree of the magma sac. The results of the study are published online in geology, a well-known international journal in the field of geosciences. The results play an important role in the study of volcanoes in northeast China.
Map of magma sac distribution given based on 3D resistivity imaging under the Wudalian Chiwei Mountain volcano in Wudalian, northeast China
Northeast China is the largest region of the new generation of volcanoes in China, including the famous Changbai Mountain volcano region and the Five Dalian Chi volcanic region. The five Dalian Chi volcanic region includes 14 volcanoes, the most recent eruption occurred between 1719 and 1721.
Using dense clothing at the geomagnetic station around the tail volcano cone, the researchers obtained a high-resolution 3D resistivity structure up to 20 km below the volcano using geomagnetic imaging. It was found that there were very significant low resistivity anomalies below the volcanic cone about three or four kilometers. Based on the abnormal distribution of low resistivity, the researchers further described the spatial distribution of magma sacs beneath the volcano. It is found that in the upper and central crusts, there is a magma sac, which is connected by a number of fine vertical channels, i.e. the magma sacs of the central crust transport magma through these channels to the magma sacs of the upper crust. The new 3D resistivity model is a good support for the model of the inter-earth crustal magma system.
At the same time, the team calculated the melting degree of the magma part in the mid-upper crustal magma sac at least 15%, combined with the velocity model obtained by noise imaging and the resistivity model obtained by geomagnetic imaging. The last eruption of the Tailmountain volcano occurred about 500,000 years ago, if there is no magma supply, the lower part of the volcanic cone should be in a cooling state, there is no partial melting state of magma presence, resistivity will correspond to a high resistivity anomaly, but the reality is not so. Therefore, it can be inferred that there is magma resupply under the tail volcano, that is, the tail mountain volcano is in a “charge” active state. By analyzing data from temporary and fixed seismic stations laid around the Tailmountain volcano, the researchers found seismic and volcanic tremor signals around the magma sacs, further confirming the activity of the tail volcano.
The study revealed that while the partial melting degree of the crater magma sac sacs has not yet reached the critical value required for eruptions (about 40%), it is necessary to strengthen volcanic monitoring in the region to better predict the likelihood of future eruptions.