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APPLICATION OF GEOELECTRIC METHODS USING BURIED ELECTRODES IN EXPLORATION AND MINING1
- Source: Geophysical Prospecting, Volume 40, Issue 5, Aug 1992, p. 573 - 586
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- 27 Apr 2006
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Abstract
Various geoelectric methods which have been developed and applied in the last 10–20 years in ELGI are discussed. These methods which use buried electrodes are: hole‐to‐surface gradient mapping to detect bauxite deposits in sinkholes below a resistive screening layer; in‐mine gradient profiling to map the basement topography below galleries; and the hole‐to‐surface version of geoelectric layer tracing to find outcrops of mineralized zones penetrated by drillings.
Data processing procedures have been developed on the basis of common concepts and hypotheses to link theoretical models with geological structures. The objects investigated are determined as the difference between the theoretical models and geological structures. The predominant part of the real electric field measured above the geological structures is the theoretical field related to the theoretical model. The effects of the objects (the anomaly) are superposed on the theoretical field but their extent is small compared with the values of the latter. The theoretical field and the anomaly depend strongly on the separation from the sources. For this reason the anomalies are difficult to recognize. Therefore the ratio of the theoretical field to the measured one is computed, since σa, the apparent specific conductivity, is proportional to this ratio.
It is demonstrated that since the changes in the σa curve depending on the location of the observation point are small, the anomalies can easily be recognized on the curve. The σa, curve computed in the above way reflects the objects better than the originally measured electric fields.
Examples illustrate the solution of the above‐mentioned geological problems by the practical application of adequate geoelectric methods using buried electrodes.