Geologists from NASA and the USGS have converged on a site in California’s high desert to investigate a mineral discovery made by a NASA sensor flying aboard a plane overhead. The team is searching for a cache of topaz, which could hint at a more valuable deposit of porphyry copper below.
What is Porphyry Copper?
Porphyry copper is one of the world’s primary sources of copper, formed when magma and hot water from deep underground course through Earth’s crust, chemically transforming the surrounding rock. This process tends to occur in subduction zones, where one tectonic plate dives below another.
The deposits can hold other critical minerals like molybdenum and tellurium, used in everything from steelmaking to solar panels. Finding these deposits is not easy, and geologists look for topaz because it forms under the same volcanic conditions.
Advanced Airborne Sensing Technology
The sensor that detected the topaz deposit was built at NASA’s Jet Propulsion Laboratory and is called AVIRIS, short for Airborne Visible Infrared Imaging Spectrometer. It analyzes reflected sunlight and can identify chemicals and minerals by their unique spectral fingerprint.
The technology was pioneered in the early 1980s and has been used to explore the Moon, Mars, and other rocky bodies in the solar system. The latest model, AVIRIS-5, recently took to the skies as part of the NASA-USGS Geologic Earth Mapping Experiment (GEMx).
The GEMx Mission
The goal of GEMx is to identify sources of critical minerals across the American West, including in the waste rock of active and legacy mines. The mission is led by the USGS and has covered over 386,000 square miles of American soil since 2023.
Ground-truthing the sensor data requires intensive investigation using ground-penetrating equipment. The team collected samples for lab analysis, which confirmed the topaz discovery. However, determining if the site overlies a porphyry copper deposit will require further investigation.
Enabling Technology: The ER-2 Aircraft
The GEMx mineral mapping campaign is enabled by one of the highest-flying aircraft in NASA’s fleet: the ER-2. The aircraft deployed from NASA’s Armstrong Flight Research Center in Edwards, California, and has completed 26 flights totaling over 125 hours.
The ER-2 can fly at high altitudes, allowing it to collect broad-area, high-resolution spectral measurements in a single pass. The data has contributed to the largest airborne surface mineralogy dataset gathered in a single NASA-USGS campaign.
The GEMx survey is part of the USGS Earth Mapping Resources Initiative, which aims to modernize mapping of the nation’s surface and subsurface to find new, critical, and other minerals. The initiative is a partnership effort with 45 state geological surveys, federal agencies, private industry, tribes, universities, and others.
- The USGS Earth Mapping Resources Initiative will capitalize on both the technology developed by NASA for spectroscopic imaging and the USGS expertise in analyzing datasets and conducting field work.
- The initiative will derive critical mineral information from the datasets, contributing to a better understanding of the nation’s mineral resources.
- The GEMx mission is an example of how advanced airborne sensing technology can be used to identify potential sources of critical minerals, which is essential for the development of new technologies and industries.
The discovery of the topaz deposit in California’s high desert is a significant finding, and the use of advanced airborne sensing technology is a crucial step in the process of identifying potential sources of critical minerals. As the demand for these minerals continues to grow, the importance of initiatives like GEMx will only continue to increase.
Source: nasa.gov.
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