Abstract Central Inner Mongolia is one of the areas with intense volcanic activity in the Cenozoic. In order to better understand the origin of these volcanoes, a study of magnetotelluric sounding (MT) was carried out. This study aims to learn about the mechanism of deep volcanic areas from the electrical point of view. Broadband and long-period MT data were collected on a 500-kilometer section at central Inner Mongolia. Two-dimensional inversion was applied since the data show no obvious three-dimensional effect. Impedance tensor decomposition and phase tensor analysis show that the electric strike angle of the study area is N45°E. A 2-D resistivity model was obtained with a depth range from surface to the uppermost mantle (0–150 km). The resistivity model imaged the ascending channels and the sources of the magma beneath the Abaga and the Dalinor volcanic groups. There are low resistivity anomalies (C1 and C2) related to volcanic activities at depths of 60–100 km below the two volcanic groups. The percentage of melt in the low-resistivity areas below the Abaga volcanic group and the Dalinor volcanic group are as high as 5–10% and 3–5% respectively. This difference in terms of melt fraction explains why the volcanic activity of the Abaga volcanic group is larger than that of the Dalinor volcanic group. Two magma chambers were found in the lower crust of the Dalinor volcanic group, and no magma chamber was found beneath the Abaga group. Based on the resistivity model, it is further speculated that the formation mechanism of volcanic activity in central Inner Mongolia is that the partial molten asthenosphere in an extensive environment flowed up to the surface through structural fissures and formed a large area of basalt platform. The magmatic body imaged at the depths of 60–100 km may be the source of volcanic eruptions of the study area.

中文翻译：

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内蒙古中部阿巴嘎和达里诺火山群形成机制的大地电磁研究

摘要 内蒙古中部是新生代火山活动强烈的地区之一。为了更好地了解这些火山的起源，开展了大地电磁测深 (MT) 研究。本研究旨在从电学角度了解深部火山区的形成机制。宽带和长周期 MT 数据是在内蒙古中部一个 500 公里的路段收集的。由于数据没有显示出明显的三维效应，因此采用二维反演。阻抗张量分解和相位张量分析表明研究区的电走向角为N45°E。获得了深度范围从地表到最上地幔（0-150 公里）的二维电阻率模型。电阻率模型对 Abaga 和 Dalinor 火山群下方的上升通道和岩浆来源进行了成像。在两个火山群下方 60-100 公里深处存在与火山活动相关的低电阻率异常（C1 和 C2）。Abaga火山群和Dalinor火山群下方低阻区的熔体百分比分别高达5%～10%和3%～5%。这种熔体分数的差异解释了为什么 Abaga 火山群的火山活动大于 Dalinor 火山群的火山活动。在达利诺火山群下地壳发现了两个岩浆房，在阿巴加火山群下未发现岩浆房。基于电阻率模型，进一步推测，内蒙古中部火山活动的形成机制是广阔环境下部分熔融软流圈通过构造裂隙向上流动，形成大面积玄武岩台地。60~100 km深度成像的岩浆体可能是研究区火山喷发的源头。