AGCOS presented “Optimization of ground electroprospecting techniques for mining exploration” at KEGS Symposium 2014.
Optimization of ground electroprospecting survey techniques for mining exploration
Recent advances in airborne EM geophysics, which confidently explores at the depth range of 0 – 400m, particularized the list of tasks facing ground electroprospecting surveys, which can be summarized in the following main objectives :
- Detallization of anomalies detected during airborne surveys and optimization of borehole coordinates;
- Prospecting and exploration for small objects (dikes, veins, sills, faults, etc.), which cannot be detected by airborne EM surveys;
- Exploration and characterization of deep ore bodies (depth to the upper edge of 300 -400m).
Based on these objectives, an optimal set of electroprospecting methods has been developed. It includes electroprospecting methods AMT – MVP (implemented 5-component measurements AMT (2E +3 H) and one of the IP method modifications. These methods implement different physical characteristics of the ore bodies from the host medium, taking into account parameters of apparent electrical resistivity (ρ) and induced polarization (Δφ, η), that register the presence of a two-phase environment, which is polarized by the flow of an electric current.
Due to recent technological advancements in electronic component base, computer technologies and software, the AMT method (5-component) has become the main tool for finding subsurface objects that differ in apparent resistivity, mainly due to its high portability, high sensitivity, high productivity, depth of investigations (2-3 km), environmental compliance and the ability to carry out all-season field surveys in any terrain or soil conditions.
When combined with AMT data, the MVP method (Hx, Hy, Hz) adds the ability to separate small objects, determine the sensitivity (direction) of objects located far away from the observation profile, rapid assessment at a field camp (without inversion), the total longitudinal conductivity of the object (G), the shape of the body and its depth (H). The total longitudinal conductivity cross-section of the body (G =σ × a1 × a2) depends mainly on the frequency (period extremum Tipper, the real induction vector). The depth of the body is mainly determined by the distance (d) between the two tipper extremes. The ratio of vertical and horizontal dimensions of the anomalous body is determined by the shape of the tipper anomalies. The angle of inclination of the body is also uniquely determined by the form of the tipper anomaly.
Since the beginning of this century, different countries around the world have accumulated positive experience in mining exploration and geological mapping using a combination of AMT (MVP) + IP technology.