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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.

Low-level helicopter flights are planned over a broad region in southwestern Colorado to image geology using airborne geophysical technology. The survey will be conducted from late August 2023 for approximately 3 months, then resume in spring 2024 for about 6 months, weather and wildfire restrictions permitting. Flights will cover areas within Chaffee, Gunnison, Saguache, Hinsdale, Ouray, San Miguel, San Juan, Dolores, Montezuma, and La Plata Counties.

The flights will be based out of assorted regional airports, beginning in the southwest survey area and operating out of Durango. The flights could shift with little warning to other parts of the survey area as necessitated by adverse flying conditions.

Image shows a map of southwest Colorado with the survey area marked with purple polygons
A map of the Colorado Mineral Belt geophysical survey area. The survey is divided into southwest and central (Mid) areas within the northeast-southwest trending Colorado Mineral Belt. The irregular outlines come from avoiding areas of restricted airspace, such as Wilderness Areas.

The purpose of the survey is to provide images that expand the fundamental knowledge of geology underpinning a broad series of historic mining districts known as the Colorado Mineral Belt. The belt hosts multiple types of mineral commodities, including critical minerals that are vital to the Nation’s security and economy.

The new geophysical data, along with geologic mapping by the Colorado Geological Survey and USGS, will be combined 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. They also address scientific questions about Colorado’s 2-billion-year-old geologic history and why multiple mineralizing events concentrated in one region over millions of years.

Image shows a helicopter with a boom sticking out front with mountains in the background
This AS350 helicopter is fitted out for an airborne geophysical survey with instruments in a long "stinger" that juts out in from of the helicopter to get the equipment as far from the rotor blades and the electrical instruments in the cockpit of the helicopter. Image courtesy of Erik Keyser of Precision GeoSurveys.

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. Flights will follow north-south lines spaced about 650 feet (200 meters) apart and east-west lines about 3,280 feet (1 km) apart. The USGS is contracting with NV5 GeoSpatial Inc., who has contracted with EDCON-PRJ and Precision GeoSurveys to collect data.

The survey will use a helicopter equipped with an elongated “stinger” mounted to the underside of the cabin extending forward of the helicopter. 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.

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 CGS and many other state geological surveys and other partners, including private companies, academics and State and Federal agencies to modernize our understanding of the Nations’ 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.

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