As the map above shows, the airborne geophysical survey will cover a 6,127 square kilometre area stretching from Port McNeill in the north to Tahsis in the south, covering portions of the Regional Districts of Strathcona and Mount Waddington. It will not fly over Woss Lake, Nimpkish Lake or Schoen Lake Provincial Parks.
How will the data be collected and used?
The project was announced in March 2019. Following requests for feedback from the mineral development sector, community leaders and Indigenous groups, work started in July 2019.
The airborne geophysical survey is collecting collect information about the magnetic properties of the rocks below the ground and the radiometric properties of rocks and soils near the surface.
Precision GeoSurveys, the contractor selected to fly the airborne geophysical survey, began flying one helicopter over the survey area during the week of July 29th, 2019 from Port McNeill and from Woss. The helicopter is easily identified by three ‘booms’ containing magnetic sensors – one on each side and one at the front. It will be flying along lines spaced 250 metres apart and at a constant height of 80 metres but will rise to 300 metres over communities. It will not fly over larger parks. Weather permitting, the flights are expected to be complete by September 30th, 2019.
The magnetic survey will map out the rock units below the surface that contain magnetic minerals, mostly magnetite, but also the iron oxide minerals hematite, maghemite, limonite, and some sulphide minerals such as pyrrhotite. These minerals disrupt the Earth’s magnetic field, and the magnetometer connected to the survey helicopter measures these subtle variations in the Earth’s magnetic field.
After this magnetic data is collected and processed, the shapes of these magnetic rock units can help geologists understand the structure of the rocks several kilometers below and identify areas that are worthy of further investigation.
The radiometric survey will map the distribution of naturally occurring radiometric isotopes in rocks and soils within about 30 centimeters of the Earth’s surface. As potassium, uranium and thorium naturally decay, they release gamma rays with characteristic energy signatures that the survey equipment attached to the helicopter detects.
Once processed, the results of the radiometric survey can be used to update geological maps and, in some cases, may be used to directly detect mineral deposits.