RE a search on the web on this TECH:"..Controlled Source Audio-range Magneto Tellurics). This technique, which Zonge recently used to define a blind ore body in the Taxco District, Mexico, uses long wavelength electromagnetic signals to probe deeply beneath the surface to detect features associated with mineral bodies. The Prime Line is designed to be approximately 12,000 feet (3,750 meters) long positioned at right angles to gold bearing fractures which contain up to 1.6 ounces of gold on Gold Ridge, within ..//..""
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Controlled-Source Audio-Frequency Magneto-Tellurics (CSAMT)
Traditional magneto-telluric surveying techniques, such as natural-source magneto-tellurics (MT) and audio-frequency magneto-tellurics (AMT), employ the electromagnetic components of naturally-occurring magneto-telluric fields in the earth to map changes in the sub-surface electrical resistivity to depths of hundreds of kilometres. CSAMT, a derivative of MT and AMT, uses an artificial source for a magneto-telluric field, in addition to those naturally occurring. CSMAT is thus generally more accurate than traditional MT and AMT methods, and allows the imaging of much shallower targets than would be possible with natural magneto-telluric fields alone.
Typical applications for CSAMT surveying include:
Mineral exploration
Petroleum exploration
Groundwater Exploration
Geothermal Exploration
Leachate migration monitoring
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Alluvial Gold and Diamond Exploration
GPR and shallow refraction seismic surveying are now accepted as common practice for reconnaissance alluvial exploration. The resistive soils of most alluvial environments yield impressive penetration depths and profile resolution. Faster and more representative of geology than test pits and boreholes alone, GPR is often used to model the three-dimensional extent of gold and diamond-bearing fluvial sequences. A variety of sediment structures including channel fills, cross-beds and longitudinal bar foresets are commonly identified. In these environments, penetration with the radar is generally excellent and frequently exceeds 50 m, while maintaining decimetre-scale vertical resolution. These data may then be used in a mining package for the 3D reconstruction of the paleochannels system. The data are generally used to delineate the extent of the paystreak, to estimate resource volume and to select strategically placed drilling and exploration targets.
AMCL has conducted numerous alluvial exploration programs using a variety of geophysical methods, including GPR, seismic refraction, frequency-domain electromagnetics, time-domain electromagnetics and electrical imaging. Paleo-channel mapping, although seemingly a simple task for geophysics, requires extensive experience gained in a variety of environments in order to achieve the best results possible. AMCL´s worldwide experience in this field gives it a distinct advantage by being able to offer staff with nearly 30 years of experience using every near-surface geophysical method for a wide variety of paleo-channel mapping projects.
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