One of the major problems of mineral exploration is the ability to reliably distinguish between uneconomic mineral deposits and economic mineralization. While the mining industry uses many geophysical methods to locate mineral deposits, until recently, there was no reliable technology for mineral resources identification and characterization.
Electromagnetic (EM) methods were developed in the 1920s and initially deployed for mineral exploration. Mineral exploration is a specific industrial application of electromagnetic methods. The users of the technology are the exploration companies.
An electromagnetic survey is based on the response of the ground to the propagation of electromagnetic fields composed of an alternating electric intensity and magnetizing force. A primary or inducing field is generated by passing an alternating current through a coil (loop of wire called a transmitter coil) placed over the ground.
The primary field spreads out in space, both above and below the ground, and can be detected with minor reduction in amplitude by a suitable receiving coil in the case of a homogeneous subsurface. However, in the presence of a conducting body the magnetic component of an electromagnetic field penetrating the ground induces alternating currents or eddy currents to flow within the conductor.
Eddy currents generate their own secondary electromagnetic field distorting the primary field. The receiver will respond to the result of arriving primary and secondary fields so that the response differs in phase, amplitude, and direction. These differences between transmitted and received electromagnetic fields reveal the presence of a conductor and provide information on its geometry and electrical properties.
Advanced Geophysical Operations and Services Inc
Advanced Geophysical Operations and Services Inc. (AGCOS) is based in Toronto, Canada and is a leading manufacturer of broadband multifunction ground and marine geophysical EM instruments for mining exploration and geological mapping. Besides equipment, AGCOS provides contract services and has extensive expertise in applying EM methods for wide range of mineral exploration tasks, kimberlites, potash, construction materials, groundwater, oil & gas, geothermal and coal exploration, as well as investigations of Earth deep crust and mantle.
To reduce exploration and drilling costs, AGCOS offers exclusive know-how high-sensitive EM exploration technology for robust assessment of licensed properties which allows to locate and precisely target multiple high and low contrast anomalies in wide depth intervals even in complex geological environments, as well as to detect these located away from measurement profiles. AGCOS also provides geological engineering, hydrogeological and archaeological mapping services and has high-sensitive EM technologies for locating old tunnels, galleries, burial sites, as well as other natural and technological inhomogeneity’s.
Multifunction EM data acquisition system configuration could be customized to customer’s specific requirements, geological task, investigations depth interval, and equipment is supplied turn-key including all necessary hardware – EM receivers, sensors of EM field, current sources, cables, software, and accessories. Broadband EM receivers GEPARD-4 and GEPARD-8 support all-known ground electroprospecting methods (SP, BBMT, AMT, MT, LMT, MVP, TC, EP, VES, DES, Electrotomography, Misse-a-la-masse, TDIP, FDIP, SIP, CSAMT, CSMT, VLF, FDEMS, IEP, TEM/TDEM), have wide frequency band (43,000 – 0.00001Hz), and are equipped with interchangeable electrical and magnetic channels allowing convenient flexibility during field data acquisition with multiple EM methods.
For sensors of EM field, AGCOS supplies several models of non-polarizing low-noise electrodes, as well as wideband and specialized magnetic sensor induction coils and airloops. For control source EM methods, supplied are several specialized and broadband transmitters with 100W to 150kW power and 1mA to 300A current output, powered by either batteries or motor generators. For offshore applications, AGCOS manufactures two and five channel seabed marine EM systems for transition zones and coastal shelf exploration with minimized weight and form factor allowing deployment and recovery from small size vessels.
For all its EM data acquisition systems, AGCOS provides extensive theoretical and practical field training and technical support, as well as assistance with pilot project planning, data acquisition, quality assurance, processing, analysis, quality and quantative interpretation, geological report preparation and optimization of borehole locations for follow-up drilling program.
Application of AGCOS turn-key EM data acquisition systems and know-how exploration technologies allows to expedite exploration project completion, improve quality of acquired response functions, increase accuracy of interpretation and to minimize exploration costs.
