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 Editor: In the public interest and in accordance with Federal Aviation Administration regulations, the USGS is announcing this low-level airborne project. Your assistance in informing the local communities is appreciated. 

RESTON, Va. — Low-level Helicopter flights are planned over a broad region in Idaho and Montana to image geology using airborne geophysical technology. The survey will be conducted from September 25, 2023 for approximately 2 months and resume mid to late Spring of 2024, weather and wildfire restrictions permitting.

Flights will cover an area of more than 3,000 square miles (~ 7,800 square kilometers) and include portions of the following counties: Beaverhead, Custer, Idaho, Lemhi, and Ravalli. 

The flights will be based out of Lemhi County Airport. The flights could shift with little warning to other parts of the survey area as necessitated by adverse flying conditions.  

The purpose of the survey is to provide images that expand the fundamental knowledge of geology underpinning the Idaho Cobalt Belt and the Montana-Idaho Porphyry Belt, two formations that have the potential to host critical minerals like cobalt, niobium, rare earth elements and titanium.

The new geophysical data will be processed to develop high-resolution three-dimensional representations of bedrock composition and structure to depths more than 3,280 feet (1 kilometer) below the surface.  

The 3D models and maps are important for improving our understanding of critical mineral resource potential, water resources, groundwater pathways near legacy mining areas, parameters for infrastructure and land use planning, and potential risks of naturally occurring radon.  

The helicopter will fly along pre-planned fight paths relatively low to the ground at about 300 feet (100 meters) above the surface. The ground clearance will be increased to 1,000 feet (300+ meters) over populated areas and will comply with Federal Aviation Administration (FAA) regulations. Flight line separation will be approximately 200 meters, with 2000 meter tie-line spacing, throughout the survey area.  

The USGS is contracting with Dewberry Engineers Inc., who has subcontracted Sander Geophysics Ltd, to collect data. 

The survey will use an Airbus AS350-B3, or similar, helicopter equipped with an elongated “stinger” mounted to the underside of the cabin extending forward. Instruments in the stinger and inside the cabin will measure variations in the Earth’s magnetic field and natural low-level gamma energy created by different rock types.  

Low-level flight helicopter with  stinger
Helicopter conducting low-level flights. Image courtesy Sander Geophysics Ltd.

The scientific instruments on the helicopter are completely passive with no emissions that pose a risk to humans, animals, or plant life. No photography or video data will be collected. The data collected will be made freely available to the public once complete. The aircraft will be flown by experienced pilots who are specially trained and approved for low-level flying. The company works with the FAA to ensure flights are safe and in accordance with U.S. law. The surveys will be conducted during daylight hours only.  

The survey fits into a broader effort by the USGS, the Idaho Geological Survey, the Montana Bureau of Mines and Geology and many other state geological surveys and other partners, including private companies, academics and State and Federal agencies to modernize our understanding of the Nation’s fundamental geologic framework and knowledge of mineral resources. This effort is known as the Earth Mapping Resources Initiative, and it includes airborne geophysical surveys like this one, geochemical reconnaissance surveys, topographic mapping using LiDAR technology, hyperspectral surveys, and geologic mapping projects.  

More information on USGS mineral resources research can be found here. To stay up to date on USGS mineral resources data and reports, follow us on Twitter.

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