摘要
当前,我国平原及低缓丘陵地区找矿潜力已较为有限,未来重点将转向西部高海拔深切割区。该类区域地形复杂、环境敏感、交通困难,传统地面物探方法受限。时间域航空电磁法作为一种高效探测技术,在此类复杂地区具有重要应用价值。本文基于有限体积法与八叉树网格技术,开展了时间域航空电磁三维正演模拟研究。研究首先通过均匀半空间模型验证了正演算法的正确性,并构建了典型山脊与山谷地形模型以对比分析不同飞行模式下的电磁响应差异。进一步地,通过在起伏地形中设置低阻异常体,研究了地形与矿体响应的耦合机制。最后,基于夏日哈木矿区真实地质剖面进行了正演建模。研究表明:在山脊与山谷的陡变地形区域,早期道响应普遍增强,在山脊顶部晚期道响应显著降低,山谷底部的响应则显著增大,揭示了地形引起的响应畸变特征。其次,地形会对含矿异常体的响应会产生多方面的复杂畸变,早期道和晚期道的响应会被淹没到地形引起的畸变中,但在响应中期阶段由异常体引起的响应变化仍可有效识别。最后,通过真实地质剖面的建模结果验证了该方法在深切割地形与复杂地质条件下的实用性,为时间域航空电磁三维反演提供了可靠的理论支撑。
Currently,the exploration potential for mineral resources in China’s plains and gently undulating hilly areas is relatively limited.Future prospective areas for mineral exploration are mainly distributed in the deeply incised,high-altitude regions of western China.These areas are characterized by rugged topography,challenging accessibility,and sensitive ecosystems,which impose significant constraints on the implementation of traditional ground-based geophysical exploration methods.As an efficient geophysical detection technique,the time-domain airborne electromagnetic(TDEM)method holds great application value for mineral exploration in deeply incised complex terrain.This study conducts three-dimensional forward modeling research for TDEM surveys based on the finite volume method and octree mesh technology.The correctness of the forward algorithm is first verified using a half-space model.Ridge and valley terrain models are constructed to compare and analyze the differences in electromagnetic responses under different flight modes.Furthermore,by embedding low-resistivity anomalous bodies beneath undulating terrain,the coupling mechanism between topographic effects and ore body responses is investigated.Finally,the method is performed to forward modeling based on an actual geological profile from the Xiarihamu area.The research demonstrates that in areas with steep terrain such as ridges and valleys,the early-time responses are generally enhanced,while the late-time responses significantly decrease at ridge tops and increase markedly at valley bottoms,revealing characteristic terrain-induced distortions.Additionally,topography causes complex multi-faceted distortions in the responses of mineralized anomalous bodies:early-time and late-time responses may be obscured by terrain-induced distortions,but the variations caused by the anomalous bodies remain identifiable during the mid-time response stage.Lastly,the modeling results from the real geological profile verify the practicality of this method in deeply incised terrain and complex geological conditions,providing reliable theoretical support for three-dimensional inversion of TDEM data.
作者
邵逸飞
龚启舟
许权
张越
王言章
王世隆
Shao Yifei;Gong Qizhou;Xu Quan;Zhang Yue;Wang Yanzhang;Wang Shilong(State Key Laboratory of Deep Earth Exploration and Imaging(Jilin University),Changchun 130061,China;College of Instrumentation&Electrical Engineering,Jilin University,Changchun 130061,China)
出处
《吉林大学学报(地球科学版)》
北大核心
2025年第6期2120-2131,共12页
Journal of Jilin University:Earth Science Edition
基金
国家重点研发计划项目(2023YFC2907101)
吉林省科技发展计划项目(20240602001RC)。
关键词
时间域航空电磁法
深切割地形
有限体积法
八叉树网格
三维正演
time-domain airborne electromagnetic method
deeply incised terrain
finite volume method
octree mesh
three-dimensional forward modeling
