Deep electrical characteristics of Mayang Basin，Hunan and its indication to tectonic and geothermal resources
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摘要:
湖南麻阳盆地位于雪峰山隆起区，地热资源丰富。为了解盆地深部结构，分析地热资源的来源，利用区内同点位采集的音频大地电磁及大地电磁剖面开展二维反演。为保证最终获得的电性结构的可靠性，首先基于相位张量对观测数据开展了维性判别、主轴方位角统计等定性分析确定了张量阻抗旋转角度。然后对比了自适应正则和L曲线正则判优2种反演策略，利用简化模型的正反演试算证明了L曲线策略所得结果更客观真实，并通过L曲线策略反演，获得了麻阳盆地的电性结构模型。最后，结合先验地质信息，识别出3条断裂的深部延展情况，并认为麻阳盆地深部高阻隆起区大致反映了盆地结晶基底隆起的范围。反演所得电性模型显示，麻阳盆地深部存在大范围高导区，推测为部分熔融的热物质，作为深部热源向上传递热量，而浅部存在的高阻体作为盖层，为地热的保存提供了有利条件，二者之间的断裂沟通了浅部和深部，最终，在麻阳县形成温泉。研究结果说明，该带还具有较大的地热资源前景。
Abstract:Mayang Basin in Hunan Province is located in the uplift area of Xuefeng Mountain, which is rich in geothermal resources. In order to understand the deep structure of the basin and analyze the source of geothermal resources, we uses the audio magnetotelluric and magnetotelluric profiles collected at the same point in the area to carry out 2D inversion. To ensure the reliability of the final electrical structure, firstly, based on the phase tensor, the qualitative analysis of the observation data, such as dimension discrimination and spindle azimuth statistics, is carried out to determine the tensor impedance rotation angle. Then, the two inversion strategies of adaptive regularization and L−curve regularization are compared. The forward and inversion trial of the simplified model proves that the results obtained by the L−curve strategy are more objective and real, and the electrical structure model of Mayang Basin is obtained by L−curve strategy inversion. Finally, combined with prior geological information, we identify the deep extension of the three faults, and believe that the deep high−resistance uplift area of the Mayang Basin roughly reflects the range of the basin’s crystalline basement uplift. The electrical model obtained by inversion shows that there is a large−scale high−conductivity area in the deep part of Mayang Basin, which is presumed to be partially melted thermal material that transmits heat upward as a deep heat source, and the high−resistance body in the shallow part serves as a caprock, which provides favorable conditions for geothermal preservation. The fracture between the two links the shallow and deep parts. Finally, a hot spring is formed at Mayang County. Our research shows that the belt also has a great prospect of geothermal resources.
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Key words:
- Mayang Basin /
- magnetotelluric /
- electrical characteristics /
- geothermal resources
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