Designed by Dr. Petr Kuzmin and manufactured by Magenta Geophysics Ltd, HyRez is an innovative new helicopter time domain electromagnetic system offered exclusively by Terraquest Ltd. HyRez differs from most other EM systems in that it is designed to be operated over resistive ground and to be sensitive to weak conductivity contrasts in highly resistive, near surface rocks. Unlike traditional systems which focus on detecting conductive sulphide mineralization such as VMS targets, HyRez is optimized to detect the more subtle contrasts in highly resistive rocks that standard EM surveys may be insensitive to.


Like many other HTDEM systems, HyRez energizes the ground with a pulse. After the pulse is shut off, the decay of the induced electromagnetic field is measured over a series of time gates; the rate of decay in the time gate sequence is directly related to the Earth’s conductivity profile. Most other HTDEM systems acquire data in the time gate range of 20 μsec – 10 millisec and are optimized to detect prominent sulphide conductors at depth. HyRez measures in the time gate range of 0.4 μsec – 40 μsec and is therefore more focused on discriminating subtle conductivity differences in more resistive, near surface rocks.


  • Detect targets containing fine-grained, disseminated sulphide mineralization hosted in resistive rocks.
  • HyRez’s sensitivity to subtle conductivity changes in highly resistive rocks may be further enhanced by the presence of displacement currents. HyRez’s advantage over other HTDEM systems is the more extensive time gate range from 0.4 – 40 μsec.
  • HyRez may be more sensitive to kimberlite intrusions, weak alteration systems, disseminated mineralization in highly resistive rocks, resistive alteration (such as silica flooding) as well as economic mineralization, such as certain types of lead, zinc, tin and iron mineralization that may not generally be targeted with standard EM platforms.
  • HyRez may also respond to fractures and faulting due to the presence of either water or alteration in those structures
  • HyRez in some cases distinguishes skarns from limestones.
  • HyRez may be deployed in arctic regions where overburden is either thin or resistive (frozen), desert areas, or well drained mountainous areas.

HyRez 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
  • it has much higher resolution with an estimated depth of investigation of 70 metres

The intent of HyRez 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 HyRez 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)

HyRez Photo
Photo accreditation: Trudy Hause, Aurora Geosciences