Abstract:

On geological maps of the Dai Tu-Thai Nguyen area, the boundary between the Van Lang Formation (T3n-r vl) and the Nui Chua magmatic complex (vT3n nc) has previously been interpreted as an unconformable stratigraphic contact. However, based on an integrated analysis of topographic, geomorphological, and geological data collected during a scientific and technological project in the Nui Hong coal mine area, this study demonstrates that this boundary is in fact a tectonic fault, designated as F.NH01. Detailed analysis of its spatial distribution, geometry, fault surface scale, kinematics, and displacement magnitude, combined with its tectonic evolution, indicates that the F.NH01 fault was formed during the Late Triassic (T3n) and subsequently underwent significant reactivation during the Jurassic–Cretaceous. The tectonic activity of this fault, together with the western fault system, played a controlling role in the formation of the coal-bearing basin of the Van Lang Formation in the study area. Fault reactivation induced folding deformation of the coal-bearing strata, resulting in the development of a northwest-southeast-trending syncline (Nui Hong syncline), which strictly controls the spatial distribution of coal seams. Notably, the deeper central part of the syncline is assessed to have considerable coal resource potential and should be prioritized for further investigation, evaluation, and exploration to support future mine development.