Recently, Guo Zhen's team, assistant professor of the Department of Marine Science and Engineering, Southern University of Science and Technology, has made important research progress on the genesis of inland volcanoes, and the relevant research results are "Lithosphere-asthenosphere interactions beneath Northeast China and the origin of its intraplate volcanism" The title was published in Geology, a top journal in the field of earth sciences.
Continental volcanic activity is a common geological phenomenon, which is formed by magma erupting from the surface of the earth's crustal weak area, and understanding the causes and distribution of these volcanic activities (especially volcanoes that are still active today) is of great scientific significance for the prevention and control of volcanic disasters and the development of volcanic resources. This study focused on Northeast China, one of the world's largest Cenozoic intraplate volcanic regions, where widely distributed volcanoes are located more than 1,000 kilometers west of the Japanese Trench (Figure 1), so their origin and dynamic mechanisms are difficult to relate to the general mantle melting mechanism at the boundary of plate convergence. Although a large number of geological studies have been carried out here in the past few decades, the origin, spatio-temporal distribution and the diversity of basalt components in the northeast region due to the lack of large-scale, high-resolution mantle thermal/chemical structure comprehensive models are still controversial.
Figure 1. A brief map of the geological structure in Northeast China.
Through joint inversion of the newly obtained seismic surface waves, surface heat flow, geoids and absolute elevation data, the study obtained a high-resolution thermal/chemical structure comprehensive model of the lithosphere and the deep upper mantle in the northeast region, including three-dimensional temperature, density, velocity and mantle component structure. In addition, the study developed a joint inversion method to quantitatively estimate the partial melting of the upper mantle, and speculated on the melt distribution of the mantle and its melt fraction in the area. The predicted hot lithosphere thickness indicates that the lithosphere beneath the Changbai Mountain orogenic belt is thinner (~65 km) and gradually increases to ~95 km in the northwest direction, but there are still areas of thinner lithosphere in the west, such as the Halaha and Abaga volcanic regions (Figure 2a), which reveal the highly varying lithosphere structures in the northeast. In addition, the results also established a complex convection model in the asthenosphere below the zone, and the upwelling of the asthenosphere mantle (Figure 3) and the partial melting of the high mantle (Figure 2b) indicated by high temperature anomalies were well consistent with the Cenozoic basalt distribution independently observed at the surface.
Figure 2. Lithosphere thermal boundaries and melt distributions (a-b) in northeast China, and the relationship between basalt trace element ratios and lithosphere thickness (c-d).
Combined with the geochemical information of basalts under the age of nearly 5 Ma in northeast China, it is found that the ratio of lithosphere thickness to basalt trace element pairs has a good consistency (Figures 2c and d), which supports the influence of lid-effect on basalt components at large scales. In summary, this study confirms that the origin and distribution of volcanic activity within the plate in the Northeast region and its basalt composition are controlled by shallow asthenosphere convection and lithosphere thickness. The simulation methods and correlations between the basalt components of the plate and the state of the mantle found in this study can be applied to assess the origin of the plate volcano in other continental regions on a global scale.
Figure 3.Three-dimensional temperature structure in northeast China.
The first author of the paper is Anqi Zhang, a postdoctoral fellow in the Department of Marine Science and Engineering, and The corresponding author is Guo Zhen, and the collaborators include Chen Yongshun, Chair Professor of the Department of Marine Science and Engineering, Juan Carlos Afonso, Heather Handley, Yang Yingjie, and Doctoral Student Dai Hongkun. SUSTech is the first unit of thesis. The above research is supported by the National Natural Science Foundation of China.
Thesis link: https://doi.org/10.1130/G49375.1
Contributed by; Department of Marine Science and Engineering
Correspondent: Yan Sha
Main image: Qiu Yan
Editor: Zhu Zengguang