Abstract—In this paper, we review the results of the deep electromagnetic soundings carried out on the Archaean blocks of the Kola Peninsula over the past 40–50 years, describe the main results of the Murman-2018 experiment, and present a critical analysis of the previous studies considering the new data. The first part of the paper addresses the results of the studies with the extremely low frequency (ELF) transmitter “Zevs” and a 40 MW MHD source “Khibiny,” the frequency soundings with a 29 kW ERS-67 car generator, and the DC resistivity soundings with vertical electrical sounding (VES) and magnetotelluric (MT) sounding setups. The review focuses on the controversial issues of the previous results for their subsequent critical analysis based on the data from the Murman-2018 experiment. The second part of the paper describes the technique, procedure, and results of the Murman-2018 experiment. The experiment included distance DC resistivity soundings (DS), controlled-source frequency soundings (Control Source AudioMagnetoTellurics, CSAMT), and audio magnetotelluric soundings (AMT) using natural variations of the Earth’s electromagnetic field. The DS and CSAMT soundings were carried out with axial and equatorial setup configurations using two mutually orthogonal current lines AB1 and AB2 with the lengths of 1.9 and 1.6 km, respectively. The key novelty of the DS measurements was the use of a linear step in changing the distance OO' between the source and receiver (2.5 and 5 km) in the range of spacings from 2.5 to 56 km. The linear step pf change of the OO' distance was used for detecting and correcting the effects of lateral and static distortions in the observation results. The DS measurements were performed along three rays directed towards West, North, and East relative to the current lines AB1 and AB2. The CSAMT measurements were performed at a distance up to 105 km from the source in combination with AMTS. Based on the results of the Murman-2018 experiment, a three-layer model of crustal structure with resistivity increasing in a gradient–stepwise manner down to a depth of 20–30 km was constructed. The resistivity in the upper layer gradually (in a gradient-wise manner) increases with depth from 10³ Ω m on the ground to 10⁴ Ω m at a depth of 1–2 km. The middle layer has a constant resistivity on the order of (1–2) × 10⁴ Ω m in the depth interval from 1–2 to 10 km and is identified as a “compaction” zone. It is detected at spacings from 2–3 to 30–40 km. In this spacing interval, apparent resistivity on the ground sharply varies ​​from 5 × 10³ to 5 × 10⁴ Ω m against the average background 2 × 10⁴ Ω m. The sharp swings are interpreted as the profiling effect and attributed to the influence of the fractured zones and faults intersected by the sounding path. According to the geological estimates, the faults are steeply dipping near the surface and gently dipping at depth. Their overall influence “stabilizes” “flattens” the resistivity of the middle layer at a level of 2 × 10⁴ Ω m and leads to the formation of effect of intermediate conductive layer having a dilatancy-diffusion origin (DD-layer) in the depth interval from 3–5 to 7–10 km (at the base of the second layer) with a longitudinal conductivity on the order of 1 S m and resistivity within 5 × 10³ to 10⁴ Ω m. The third (bottom) layer manifests itself by a sharp stepwise increase in electrical resistivity up to 10⁵–10⁶ Ω m and higher. The top surface of this layer is located at a depth of 10–15 km and is conditionally interpreted as an “impenetrability boundary” for direct current. This boundary marks the Brittle–Ductile Transition Zone (BDT) of the rocks. A critical analysis of the previous results in the light of the new data obtained in the Murman-2018 experiment is conducted in the Discussion section.

摘要—在本文中，我们回顾了过去40至50年间在科拉半岛的太古宙块上进行的深层电磁探测的结果，描述了Murman-2018实验的主要结果，并对这一问题进行了批判性分析先前的研究考虑了新数据。本文的第一部分介绍了使用极低频（ELF）发射器“ Zevs”和40 MW MHD信号源“ Khibiny”的研究结果，使用29 kW ERS-67汽车发电机的频率测深仪和直流电具有垂直电测深（VES）和大地电磁（MT）测深设置的电阻率测深。这篇综述着重于先前结果的争议性问题，并基于Murman-2018实验的数据对其进行后续的批判性分析。本文的第二部分描述了技术，过程，和Murman-2018实验的结果。该实验包括使用地球电磁场的自然变化的距离直流电阻率测深（DS），受控源频率测深（Control Source AudioMagnetoTellurics，CSAMT）和音频大地电磁测深（AMT）。DS和CSAMT测深分别使用两条相互正交的电流线AB1和AB2分别沿长度为1.9公里和1.6公里的轴向和赤道设置进行。DS测量的关键新颖之处在于，使用线性步骤在2.5至56 km的间距范围内更改源与接收器之间的距离OO'（2.5和5 km）。OO'距离的线性阶跃pf变化用于检测和校正观测结果中的横向和静态变形的影响。DS测量是沿着相对于当前线AB1和AB2指向西，北和东的三束光线进行的。结合AMTS，在距震源最远105公里处执行CSAMT测量。根据Murman-2018实验的结果，构造了一个三层地壳结构模型，其电阻率以梯度逐步增加的方式下降到20-30 km的深度。上层的电阻率随着深度从10开始逐渐增加（以梯度方式）构造了一个三层的地壳结构模型，电阻率以梯度逐步增加的方式下降到20-30 km的深度。上层的电阻率随着深度从10开始逐渐增大（以梯度方式）构造了一个三层的地壳结构模型，电阻率以梯度逐步增加的方式下降到20-30 km的深度。上层的电阻率随着深度从10开始逐渐增大（以梯度方式）³在地面上Ωm至10 ⁴在1-2公里的深度Ω米。中间层具有的（1-2）的数量级上的恒定电阻率×10 ⁴在从1-2到10公里深度间隔Ωm和被识别为“压实”区。在2–3至30–40 km的距离内检测到它。在这个间隔时间，在地面上的视电阻率急剧从5×10变化³〜5×10 ⁴ Ω米针对该平均背景2×10 ⁴Ω·米 陡峭的摆动被解释为剖面效应，并归因于断裂带和探空路径相交的断层的影响。根据地质估计，断层在地表附近陡倾，在深处缓慢倾角。它们的整体影响“稳定”，“变平”的中间层的电阻率在2×10的电平⁴ Ωm和引线在深度形成的具有膨胀性扩散原点中间导电层（DD-层）的效果间隔为3–5至7–10 km（在第二层的底部），纵向电导率为1 S m，电阻率在5×10 ³至10 ^4之间Ω·米 第三（底部）层常表现为通过在电阻率高达急剧逐步增加至10 ⁵ -10 ⁶ Ωm和更高。该层的顶面位于10-15 km的深度，有条件地被解释为直流电的“不可渗透边界”。该边界标志着岩石的脆性-韧性转变区（BDT）。在“讨论”部分中，根据在Murman-2018实验中获得的新数据对以前的结果进行了批判性分析。