Abstract:
Large-area hydrogen escape anomalies were detected during the soil hydrogen geochemical survey in the Zhangbei Basin, making it urgent to apply geophysical methods to understand the basement structures that generate and transport hydrogen. For this purpose, the first gravity and magnetotelluric surveys targeting natural hydrogen were conducted in the Zhangbei Basin, with 1∶50,000 gravity and magnetotelluric surveys performed within the study area. Using the collected gravity and magnetotelluric data, a large-scale gravity-magnetotelluric profile across the study area was inverted, constrained by drilling, geological, and physical property data. The study identified a "two depressions and three uplifts" structural pattern in the basin, with a total Mesozoic-Cenozoic sedimentary thickness ranging from 0.62 to 1.9 km. Four concealed faults were revealed, among which faults F
1 and F
4 can serve as migration pathways and storage channels for natural hydrogen. The inversion results indicate that the two depressions exhibited continuous and stable stratigraphic interfaces and relatively thick sandstone-mudstone assemblage layers, which provide good sealing capacity to reduce hydrogen leakage effectively. These findings on basement structures offer valuable insights for the prospect area evaluation of natural hydrogen and subsequent exploration plans in the area. They also provide a significant basis for establishing a natural hydrogen exploration technology system and selecting optimal exploration targets.