伟晶岩型锂矿人工源电磁勘探可行性研究

Detectability of pegmatite lithium deposits by controlled-source electromagnetic methods

锂矿可为电动汽车、手机等可充电锂电池提供原材料,伟晶岩型锂矿约占全球锂资源的1/4。但是对于高阻伟晶岩型锂矿床电磁探测的可行性一直缺乏系统性研究。伟晶岩脉整体上呈现高阻特征,虽然围岩电阻率已普遍达到上千欧姆米,但含矿伟晶岩的电阻率接近上万欧姆米,不含矿的伟晶岩电阻率更高。如何在高阻背景中有效识别更高阻的伟晶岩脉成为电磁方法亟待解决的关键技术问题。本文提出利用人工源电磁横磁场探测方法解决高阻目标的探测问题,并开展传统人工源电磁法和新研发的横磁场探测方法的对比性研究,从响应特征、分辨率等角度对不同方法、不同分量进行系统性对比分析。通过均方根误差的计算,双线源电磁水平电场显示出相较于传统接地导线源更强的高阻目标分辨能力。

Lithium-bearing minerals are used as raw materials for rechargeable lithium batteries on electric cars,cell phone,etc.,while pegmatite lithium deposits account for about a quarter of the world’s lithium resources.However,the effectiveness of electromagnetic exploration methods for high-resistivity pegmatite Li-Be deposits has not been systematically studied.Pegmatite dikes generally have high resistivity—it is close to 10000 ohms for ore-bearing pegmatites,and higher for common pegmatites.Whilst the resistivity of the host rock is generally up to several thousand ohms.Thus how to effectively identify high-resistivity ore-bearing pegmatites under resistive background has become an urgent technical problem.Here,we use transverse magnetic field to solve the detection problem for high-resistivity targets,and the effectiveness of the newly developed detection method is evaluated over the traditional single-line controlled-source method.We systematically compare different components of electromagnetic response from different configurations in terms of response characteristics and resolution,and calculate the root mean square misfit.We find the horizontal electric field component from double-line source shows higher resolution for high-resistivity targets over the traditional single-line source.