Airborne Electromagnetic geophysical surveys measuring the electrical resistivity of the earth are conducted from the air using towed EM arrays or EM loops. Airborne EM typically use a transmitter that carries a current that varies in magnitude as a function of time to measure electromagnetic conductors.
In Time domain EM systems, the current is turned on and off in a rapid manner to measure the rate of decay of the primary and secondary field responses in the conductors. Switching is repeated several times a second as the aircraft follow its flight line, so that the signal is essentially continuous. If a conductor is present, a sudden change in the magnetic field intensity can be measured by slower EM decay rates.
Electromagnetic surveys are often used in the search for fresh water aquifers, using methods that can cover a survey area in a few days that would have taken months to cover using ground methods.
In mineral exploration intense direct targeting responses are associated from massive sulphides, uranium deposits and Magmatic Ni-Cu-PGD deposits. They are moderately effective as a geological framework tool for diamond exploration, lode gold, VMS deposits, and Sedex deposits.
Terraquest has developed an innovative helicopter Time Domain EM system, designed by Dr. Petr Kuzmin - the world renowned research engineer and designer of active and passive EM systems.
EM-Power differs from other TDEM systems because:
- it measures very early time gates from 0.4 microseconds to 40 microseconds and
- it is designed to operate over very resistive to moderately resistive ground and
- it is sensitive to the subtle resistivity contrasts in resistive rocks up to the order of 10,000 ohm-metres or even higher and
- It has much higher resolution with an estimated depth of investigation of 70 metres.
The intent of EM-Power is not focused on detecting conductive sulphide mineralization such as the VMS targets typical of standard EM surveys, but to detect more subtle contrasts in highly resistive rocks that standard EM surveys are typically insensitive to. The system also detects very short time constant IP phenomena that cannot be observed on other conventional TDEM systems. Moreover, it is a light weight system that can be towed easily and economically with a ubiquitous 206B Jet Ranger and is designed to explore large areas within a reasonable budget.
Terraquest is offering EM-Power for a number of challenging targets using a wide range of physical properties such as:
- Subtle resistivity contrasts to map
- rock types
- alteration/silicification zones (eg: gold, lithium)
- groundwater studies (contrasts between clay, sand, gravel and freshwater
- IP effects, especially small pore sizes (fine grained disseminated mineralization)
- Short time constants (kimberlite)
If you are looking for challenging targets using EM, then, consider EM-Power for the following:
- Mapping resistivity contrasts (diamonds)
- Detecting silica flooding (gold)
- Differentiating resistive alteration phases (gold)
- Detecting fine-grained, disseminated mineralization
- Locating resistive minerals (lithium)
- Operating at high altitudes / difficult terrain
- Near surface engineering / environmental
- Mapping aquifers
Specialists in Airborne Geophysical Surveys
Terraquest was established in 1984 and since then, our dedicated team has flown over 1,500 airborne geophysical surveys using both fixed wing and helicopter platforms. Our professional crews provide significant experience having carried out airborne magnetic surveys, airborne gravity surveys, airborne radiometric surveys, and airborne electromagnetic surveys on five continents.
Our quality data sets have been utilized in the exploration for base and precious metals, kimberlite, hydrocarbons, uranium, rare earth minerals and water. The company has performed exemplary surveys for both small and large exploration groups as well as many government agencies. References can be provided upon request. Visit
www.terraquest.ca.
Ed. GMH