Airborne magnetic and radiometric survey, east central Idaho and Montana, 2023-2024

This data release provides digital flight-line and gridded data for a high-resolution airborne magnetic and radiometric survey over parts of eastern Idaho and western Montana. The survey was acquired as part of the UGSS Earth Mapping Resource Initiative (Earth MRI) to improve our understanding of the fundamental geologic framework of the region with applications to evaluating natural resources and geologic hazards. The survey traverses parts of Idaho and Montana counties Lemhi, Custer, Ravalli, and Beaverhead. The survey area includes portions of the Idaho Cobalt Belt and the western edge of the Montana-Idaho porphyry belt, which have the potential to host critical REE, cobalt, titanium, and niobium minerals. Data for this survey were acquired and processed by Sander Geophysics Ltd (SGL) under contract to Dewberry and the USGS. The survey was flown from July 2023 to October 2024, with helicopter coverage due to the mountainous topography. Pre-planned flight lines were flown in an E-W direction with 200-m line spacing; N-S tie-lines were flown with 2000-m line spacing. The nominal flight height of 200 meters (m) above ground, with areas having higher population densities flown at a nominal height of 330 m above ground for safety reasons. A total of approximately 46,000 linear kilometers of data were collected covering an area of approximately 8,200 square km. Following acquisition, SGL also performed extensive post-processing of the data and delivered the final databases, grids, and images. Details regarding the flights and data processing are described in the contractor report provided in this release.