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The Zhongxingtun area in Inner Mongolia, China, hosts an important copper polymetallic ore field. Surface copper and molybdenum–copper orebodies have been found, without deep drilling. A new round of prospecting is focused on finding deep orebodies. To identify these copper and molybdenum orebodies and the deep structure, the controlled-source audio frequency magnetotelluric (CSAMT) method was implemented in the Zhongxingtun area with a V8 multi-function electrical prospecting system using the continuous profile method with a network density of 100 m × 20 m in the western region and 50 m × 20 m in the east. These measurement densities are different from that used in most other areas, and a dense network is mainly utilised due to the need for mineral exploration. The borehole positions were determined by a comprehensive analysis of the two-dimensional imaging from the collected data, the geological features of the study area, and the physical characteristics of the bedrock. The drilling proved that molybdenum orebodies exist in the deeper regions where the mineralisation is characterised by the predominance of molybdenum followed by copper. The results show that through the analysis of the apparent resistivity obtained by the CSAMT method in the Zhongxingtun area, drilling hole positions are determined, and a deep mineralised body is discovered, showing that the CSAMT method is effective. This method is expected to be widely used in prospecting for copper polymetallic ore deposits. [ABSTRACT FROM AUTHOR]

The electrical resistivity and induced polarization (IP) methods are widely used in geological mapping, prospecting and exploration of mineral deposits, engineering geology, hydrogeology, archaeology, and geotechnical and environmental applications. Historically, these methods have formed the basis of the electrical prospecting technique. In these methods, a DC or low-frequency AC electrical current is introduced into the earth through a grounded transmitter line. The measured quantity is the electric field. However, if the earth’s resistivity or chargeability changes horizontally, this change gives rise to an anomalous magnetic field, which is studied by the magnetometric resistivity (MMR) and magnetic induced polarization (MIP) methods, respectively. Along with advantages, some shortcomings are inherent in the MMR and MIP techniques. Apparently, the main drawback of these methods is that the magnetic fields of both the transmitter line wire and ground electrodes on the surface are several orders of magnitude greater than the anomalous magnetic field response. This introduces a significant “noise” to magnetic-resistivity data. We investigate the potential of using a circular electric dipole (CED) in magnetometric resistivity techniques. It has been found that the application of a CED, instead of a conventional transmitter line, dramatically enhances the signal-to-noise ratio. [ABSTRACT FROM AUTHOR]

exploration area and for building of a detailed hydrogeological model, especially with complex geological models and 3-D structure shapes. Electrical sounding is based on a theoretical assumption of a horizontally stratified earth model, and electrical profiling maps only lateral resistivity changes at the same depth. Two-dimensional (2-D) electrical imaging (or 2-D electrical tomography), that has been introduced recently, can map the both vertical and lateral resistivity changes and provides for building three-dimensional (3-D) resistivity model of the underground. Exploration has been carried out in the area of the Seona spring to investigate the possibility for pumping more water during dry season, from the well located near the spring. The water of the Seona spring emerges from Badenian carbonate aquifer, which shows irregular 3-D shape and heterogeneous lithologic composition. A network consisting of four electrical profiles has been established to acquire a 3-D resistivity model, which can be transformed in a 3-D hydrogeological model. Inverse resistivity model sections revealed high resistivity zone which has been correlated with Badenian limestone by means of existing outcrops. Low resistivity zones point to the marly layers. Exploratory borehole located on the basis of electrical data has confirmed derived hydrogeological model from the electrical imaging data. Heterogeneous limestone aquifer has been uncovered at depth 8.2 – 55 m. The aquifer is weathered and karstificated with two main cavern intervals. Hydraulic connections between the caverns and the spring have been established during drilling, but also in a pump test by means of the airlift method. The presented case demonstrates great possibilities of the electrical imaging method in mapping of irregularly shaped aquifers and building of a precise 3-D hydrogeological model.

Corrosion of steel reinforcement is one of the most common causes of end service life in reinforced concrete structures. Corrosion is initiated and propagates unseen beneath the concrete cover and it is difficult to evaluate the severity of the problem. The most promising electrochemical method is the Linear Polarisation Resistance method which can provide a direct evaluation of the instantaneous rate of corrosion. The main drawback to this technique is that it requires a localized breakout of the concrete cover to provide an electrical connection to the steel reinforcement. This article describes an adaptation of the LPR method and the four-point Wenner resistivity method to give an assessment of the rate of steel corrosion without the requirement for a direct connection to the reinforcement. The measurements have been performed in cooperation with Construction and Infrastructure Group in University of Liverpool. [ABSTRACT FROM AUTHOR]

The goal of this work was to study a contaminated soil due to a gasoline spill produced by fissures in a concrete purge chamber located along a gas transmission line. A monitoring well drilled 16 m down gradient from the purge chamber revealed the presence of a gasoline layer of 0.5 m thick at 1.5 m depth, floating on top of the water table. A second well, drilled 30 m away from the first well, and in the same direction, did not show any evidence of contamination. To investigate this problem, a geoelectrical survey was conducted, combining dipole–dipole and Wenner arrays. First, four dipole–dipole profiles in a direction perpendicular to the longitudinal axis joining the wells were carried out. The electrical tomographies obtained from the 2D inversion of the data showed that the contaminated region was characterized by a resistive plume located at a depth between 1 to 2 m and had lateral extent of about 6–8 m. The longitudinal extension was less than 20 m, since the last profile located 30 m farther from the chamber did not show this kind of anomaly. To better determine the longitudinal extension, we performed a dipole–dipole profile along a line in this direction. The inverse model confirmed that the extension of the contaminated section was about 16 m. To complete the study of the deeper layer, we carried out Wenner soundings. The results of the inversion process indicated that to a depth of 20 m the soil was very conductive, because of the presence of clays as the main constituents, which confine the contaminant within this impermeable surrounding. To improve the inverse model, we performed a joint inversion of dipole–dipole and Wenner data. Analysis of the depth of penetration showed that it increased to 25 m and comparing the resulting model with the ones obtained from each array separately, we concluded that the joint inversion improves the depth obtained by the survey, while maintaining the shallow lateral resolution. [Copyright &y& Elsevier]