Airborne EM has been responsible for the discovery of billions of dollars worth of mineral deposits. It is a cost effective method for scanning large areas of ground for conductors for follow up ground targeting or direct target drilling. It is a preferred method for mapping massive sulphides and paleochannels that may contain uranium deposits and/or groundwater.
EM surveys map the three dimensional variation in conductivity, caused by changes in mineralogy, intensity of alteration, water content or salinity. Airborne electromagnetic surveys are useful in investigations of different geological eras. For instance, they can help in locating subglacial valleys, which helps to understand water reservoirs. Electro-magnetic surveys are aimed at conducting a quick and cheap search for metallic conductors. It is also applicable to general geologic mapping and many engineering problems.
GPX Surveys operates a heliborne time-domain electromagnetic systems called XTEM. The system induces an EM response in the ground using a large transmitter coil and measure the EM response using an in-loop receiver coil during the transmission off-time. Airborne magnetic data is also recorded. The results from our surveys can be used to make three-dimensional models of the conductivity and associated geology.
Our airborne EM system has been used for mapping host rocks containing minerals such as gold, copper, iron ore, diamonds and manganese. They can be used to identify geological faults and map geological structures such as paleochannels. Airborne EM has been used extensively for uranium exploration. Please click here for a flyer about our uranium exploration techniques.
The resistivity or conductivity contrast between water and the surrounding geology can map groundwater supplies. Water may also be present in paleochannels.
Airborne EM can used to map dryland salinity and aid salinity management.
There are two types of airborne EM survey - frequency-domain and time-domain. Frequency domain measures the frequencies of the induced EM response whereas time-domain measures the rate of change of the induced EM response. XTEM uses the time-domain technique and has an in-loop geometry (TzRz).
An EM field is created in a transmitter coil which induces a secondary EM response from conductors below the surface. The secondary EM response (dBz/dt) is measured in the off-time by a receiver coil that is coincident with the transmitter coil.
The raw data is processed, binned into 30 channels and modeled using EMAXAir CDI software. Three dimensional models of the conductivity can be created based on the CDI models.
Surveys can be designed to ascertain the general sub-surface
geophysical structures of a regional area or as a highly detailed
study of a target area.
The XTEM system records magnetic data during the off-time.
NEPEAN CASE STUDY
The Nepean test area is an abandoned mine with a known nickel deposit near Kalgoorlie, Western Australia. It has been flown by Hoistem, VTEM and XTEM (August 14 2009). For a summary and comparison of the test results please click here.
For equipment specifications please click here.