Finding Alaska's Critical Minerals With a New Geospatial Method

In short

• The U.S. Geological Survey devised a new, GIS-based way to find areas with mineral-resource potential.
• Applied to Alaska, it pointed to areas that may hold concentrations of critical minerals.
• It offers a template for assessing other large, little-explored regions.
• The results are meant to inform land management and guide future exploration and research.

Alaska covers more than 663,000 square miles (1,717,000 square kilometres) — more than a sixth of the United States — and much of it has never been systematically studied or sampled for minerals. Many areas are known to be rich in them; the state has six operating mines and many active exploration projects. The USGS and the Alaska Division of Geological & Geophysical Surveys developed a geospatial tool that combines public databases of geological information to estimate the potential for critical minerals, and used it on Alaska. The results pick out areas with known deposits and also areas not previously thought promising for these deposit types.

What critical minerals are

Critical minerals — sometimes called strategic and critical minerals — are those for which the United States imports more than half of its supply, largely from countries that cannot be considered reliable trading partners. They are part of every corner of modern life:

• Rare earth elements and yttrium: recyclable batteries, oil refining, generators, jet engines, semiconductors, computers, smartphones, night-vision goggles, and permanent magnets such as those in MRI machines.
• Platinum group elements: catalytic converters, scrubbers for toxic emissions, electronics, dentistry.
• Germanium and gallium: solar cells, infrared optics, LEDs, semiconductors, smartphones.
• Uranium and thorium: nuclear power, and radioisotopes for medical diagnosis and research.
• Tin and indium: architectural glass, flat screens, solar cells, semiconductors, smartphones, lead-free solder, and tin-niobium alloys for superconductors.
• Tungsten and titanium: high-strength alloys; tungsten also for thermocouples, thermometers and light bulb filaments.
• Gold: radiation-shielding films for spacecraft, dentistry, jewellery.
• Molybdenum, chrome, cobalt, nickel, tantalum and vanadium: superalloys that resist wear and corrosion in pipelines, desalination plants, turbines, missiles and spacecraft.

The minerals and deposit types studied were chosen with federal, state and academic scientists and with federal and state resource managers, because they are known or suspected to occur in Alaska and may contain critical minerals.

U.S. net import reliance in 2016 — imports minus exports, as a share of consumption — for critical minerals found or suspected in Alaska. Gold and molybdenum are net exports but matter to the U.S. and Alaskan economies. Figure by Graham Lederer, USGS National Minerals Information Center.

How the method works

The method combines public USGS and state databases of many kinds: rock types; the chemistry of rocks and stream sediments; minerals found in streams; magnetic and radiometric properties measured from aircraft; and known occurrences of the mineral in question. Each is given a statistically based score — for instance, for how common a suitable rock type is, or how much of an element a rock or sediment contains — and tied, by where the sample was taken, to a subwatershed, the smallest unit in the National Hydrography Dataset. Subwatersheds are used because they are natural boundaries for the rock and minerals that erosion carries into streams, so stream samples are the most efficient summary of what a drainage basin is made of.

Each subwatershed's scores are totalled and compared statewide, and the result is shown in colour: high potential (red), medium (yellow), low (green) or unknown (grey). The shade shows certainty — dark, medium or light for high, medium or low — depending on how many datasets contributed.

What it found

Every one of the six deposit groups has potential in several parts of Alaska. The Seward Peninsula, east-central Alaska, the western Alaska Range and southeast Alaska have clusters of red subwatersheds for most of them. The method found potential in new areas, such as the northern Brooks Range, and widened the areas of potential around known mineralised districts like the Seward Peninsula and east-central Alaska.

Estimated potential and certainty for the six deposit groups and their critical minerals across Alaska. USGS.

The road ahead

The study turned up many high-potential areas not recognised before, showing the method's value for finding underexplored places for any commodity. The most interesting are those with medium to high potential but medium to low certainty (yellow and red in lighter shades), where more data could reveal an economic concentration. The technique is also a new way to analyse large geospatial datasets together, which could lead to new exploration areas and new insight into how ore deposits form.

USGS researchers collect a soil sample for rare earth elements at the Roy Creek prospect, Alaska. Photograph by Susan Karl, USGS.

A drill rig on the Dotson veins at the Bokan Mountain rare earth deposit. Photograph by Susan Karl, USGS.

A gold dredge near Nome, Alaska. Photograph by Doug Yager, USGS.

Sources

• Susan Karl and Keith Labay, Geospatial Analysis Identifies Critical Mineral-Resource Potential in Alaska, USGS Fact Sheet 2017–3012, March 2017. https://doi.org/10.3133/fs20173012
• The full report: Karl, S.M., Jones, J.V., III, and Hayes, T.S., eds., 2016, USGS Open-File Report 2016–1191. http://dx.doi.org/10.3133/ofr20161191