Zhang Mengli, Perkovich Noah, Li Yaoguo, Weihermann Jessica, Crummett R Nate
Center for Gravity, Electrical, and Magnetic Studies, Department of Geophysics, Colorado School of Mines, Golden, USA.
Sci Rep. 2025 Jul 1;15(1):22344. doi: 10.1038/s41598-025-07335-5.
Fairy circles are subcircular surface depression features that are widely distributed all over the world and they are commonly considered as a potential indicator to the presence of subsurface geologic hydrogen. Understanding the relationship between fairy circles and geological structures could assist in understanding potential hydrogen migration pathways and accumulations. We have carried out an integrated geophysical investigation over a group of such circles in the central U.S. We integrate digital elevation model (DEM), airborne gamma-ray spectrometry (AGRS) data, and ground electrical resistivity data to understand the connection between the surficial expressions and the underlying geology of the fairy circles. The study has shown that correlation between the locations of the fairy circles with either radiometric data or subsurface mafic or ultramafic rocks cannot be established. Meanwhile, the imaged geo-electrical structure within 500 m depth from the surface shows that the rim of the studied circle is directly above a ring of more resistive gap in a conductive layer. The low water saturation or lower salinity imaged by the high resistivity in this ring would allow the subsurface H2 to seep through more easily and, therefore, can explain the elevated H concentration from soil gas sampling.
仙人圈是呈亚圆形的地表凹陷特征，广泛分布于世界各地，通常被视为地下地质氢气存在的潜在指示标志。了解仙人圈与地质构造之间的关系有助于理解潜在的氢气运移路径和聚集情况。我们在美国中部的一组此类圆圈区域开展了综合地球物理调查。我们整合了数字高程模型（DEM）、航空伽马射线能谱测量（AGRS）数据和地面电阻率数据，以了解仙人圈的地表表现与地下地质情况之间的联系。研究表明，无法确定仙人圈位置与放射性数据或地下镁铁质或超镁铁质岩石之间的相关性。同时，从地表起500米深度范围内成像的地电结构显示，所研究圆圈的边缘直接位于导电层中一个电阻更大的间隙环的上方。该环中高电阻率成像所显示的低含水饱和度或低盐度会使地下氢气更易渗出，因此可以解释土壤气体采样中氢气浓度升高的现象。
