利用多通道瞬变电磁法识别深部矿体——以内蒙兴安盟铅锌银矿为例

多通道瞬变电磁法由于采用伪随机编码发射、最佳匹配相干解码技术,所以相比于传统时间域电磁方法勘探深度大且抗干扰能力强,是目前地面资源勘查领域的研究热点.针对内蒙兴安盟某铅锌银矿埋藏深度大等特点,首先根据矿区资料建立一维以及二维模型,数值计算脉冲响应并分析其特征,说明多通道瞬变电磁对于大埋深低阻异常体有良好的反映,随后通过多通道瞬变电磁技术对矿区进行实例勘查,数据处理过程中利用了反卷积的方法提取大地脉冲响应,根据轴向大地脉冲响应的峰值时刻计算视电阻率,通过对视电阻率进行全波形反演得到解释剖面,与测区钻孔资料对比分析证明,多通道瞬变电磁法是反映深部低阻异常体的有效手段.

Identifying deep ore bodies using the Multi-Channel Transient Electromagnetic Method (MTEM): an example of a lead-zinc-silver mine in Inner Mongolia

The Multi-Channel Transient Electromagnetic Method(MTEM)adopts pseudo-random code transmission and best matching coherent decoding technology, thus its exploration depth is larger and the anti-interference ability is stronger than the traditional time domain electromagnetic method, and it becomes a research focus in ground resource exploration. This paper presents the application of the method to a lead-zinc-silver mine in Xing'an League of Inner Mongolia. In view of its large burial depth, firstly, we establish a one-dimensional and a two-dimensional model based on the data of the mining area. Then we calculate the impulse response and analyze its characteristics. Results show that the MTEM can reflect well the resistance anomalies at large depths. This technology is used to carry out an example survey in the mining area. In the data processing process, the deconvolution method is used to extract the earth impulse response, and the apparent resistivity is calculated according to the peak moment of the axial ground impulse response. The full-waveform inversion of the apparent resistivity yields an explanatory profile. The comparison with the borehole data of the survey area proves that the MTEM is an effective method to reveal bodies with low-resistance anomalies in the deep subsurface.