Analysis of current crustal movement and strain characteristics of Guangxi ε-type tectonic system based on GNSS observations

The current crustal movement patterns and dynamic mechanisms of the Guangxi ε-type tectonic system remain unclear. Based on data from 128 GNSS observation stations in Guangxi and neighboring areas from 2009 to 2023, this study calculates the regional three-dimensional velocity field and performs an inversion of crustal strain parameters using the Grid-Distance Weighted (GDW) method. This study systematically analyzes the tectonic movement characteristics of the ε-type tectonic system for the first time. The results indicate that, within an Eurasian Plate reference framework, the Guangxi region moves as a whole in an SE-E direction at an average horizontal rate of 6.39 ± 0.16 mm/yr. Vertically, it primarily experiences slow uplift with local subsidence, presenting a “butterfly-shaped” distribution in the spatial variation of vertical displacement. The deformation of the different tectonic units displays distinct characteristics: the backbone unit exhibits bidirectional compression in both NS and EW directions; the horseshoe-shaped betwixtoland and frontal arc units show compressional uplift; the western reflection arc is strongly compressed from the northwest, while the eastern reflex arcs gradually transition from being stretched in the NE direction to being compressed in the EW direction. The spatial distribution of the strain field shows the following: the northern segment of the backbone and the reflection arcs on both the eastern and western sides are high-strain zones, while the southern segment of the backbone and the frontal arc top are low-strain zones, with the two flanks of the frontal arc serving as the transition zones between high and low strain areas. The dynamic mechanism analysis suggests that the northeastward collision of the Indian Plate, the westward subduction of the Philippine Sea Plate, and the mantle plume effect in the South China Sea collectively drive the crustal deformation in the Guangxi region. The findings provide crucial observational evidence and theoretical insights into the tectonic evolution and mineral resource distribution of South China.