Revealing Alaska's critical minerals
USGS, DGGS develop tool to help guide geologists, explorers
Last updated 7/10/2020 at 1:55pm
Geologists familiar with Alaska already know the Far North State is a great place to explore for critical minerals and metals such as graphite, rare earths, platinum metals, cobalt and tin. A new report published by the U.S. Geological Survey, however, indicates that Alaska may be richer in these and other minerals and metals vital to the economy and security of the United States than previously realized.
Working alongside the Alaska Division of Geological & Geophysical Surveys, USGS developed a new geospatial tool that integrates and analyzes a massive load of geologic information and applies this data to estimating the resource potential for six deposit types that host a large array of critical minerals.
After crunching all the data, this new tool has turned up new and expanded areas of Alaska with the potential for a wide array of minerals and metals vital to modern living – many of which are not currently mined in the United States.
"Some of the areas that showed high potential were already known, but many of these areas had not previously been recognized," explained Sue Karl, an Alaska-based USGS research geologist and lead author of the study. "Areas identified by this method that have high resource potential based on limited data indicate both understudied and underexplored areas that are important targets for future data collection, research investigations and exploration."
New REE hunting grounds
The new geospatial tool worked particularly well for identifying new areas of Alaska to explore for rare earth elements, or REEs, a group of 17 minerals that possess unique characteristics that make them important ingredients to many high-technology devises used by both civilians and the military.
While high-tech applications make rare earths vital to America's strategic and economic security, the fact that more than 90 percent of these metals used by manufactures in the U.S. every year come from China elevates their status to critical.
Ucore Rare Metals' Bokan Mountain project at the southern tip of Prince of Wales Island in Southeast Alaska has already been identified as one potential domestic source of rare earths. The USGS geospatial tool, however, has identified eight large swaths of the Far North State worth checking out.
One such region extends 200 miles northwest from Bokan Mountain and encompasses other known rare earth prospects such as Dora Bay and Salmon Bay, both also on Prince of Wales Island. While this region is worthy of additional exploration, it does not light up USGS's Alaska REE potential map like some other areas of the state.
A 15,000-square-mile region at the west end of the Alaska Range, however, did light up the map with high-potential areas.
The few small REE occurrences previously identified in this area, which covers Mount Estelle and the Revelations Mountains, do not account for the high potential the USGS geospatial tool has given to a large portion of this region – a sign that this area is exceedingly underexplored and a great place to hunt for rare earths.
• The other regions were the USGS identified high REE potential are:
• Northern Alaska Range, an area arcing about 220 miles west from Tok;
• Yukon-Tanana, a large swath of Interior Alaska extending from the Yukon-Alaska border to the Roy Creek REE prospect north of Fairbanks;
• Kuskokwim-White Mountains, which stretches about 500 miles southwest from Yukon-Tanana;
• Kokrines-Hodzana, a 200-mile-long area of Interior Alaska just north of the Yukon River that includes known REE hunting grounds like Ray Mountains and Kokrines Hills;
• Darby Hogatza, an area of know uranium and REE occurrences that arcs 200 miles east from the Seward Peninsula; and
• Porcupine, an area centered on Spike Mountain in far northeastern Alaska.
• The same areas that show promise for REEs are also great places to look for uranium, according to the data churned out by the new USGS geospatial tool.
Critical mineral-bearing granites
For the most part, specialized granites containing tin, indium, tungsten, titanium, tantalum, and fluorspar can be found in the same regions of Alaska as you would seek REEs.
The United States is near 100 percent import-reliant on all of these critical metals except for tin, in which case it imports roughly 80 percent of what it needs.
Tin and indium are important ingredients for architectural glass, flat screens, solar cells, semiconductors, smartphones, lead-free solders and alloys for superconductors.
Tungsten and titanium are primarily used for high-strength metals alloys.
Tantalum is an important ingredient for automotive electronics, mobile phones, personal computers, and light but high-performance glass lenses.
Fluorspar is used to make specialty glass, ceramics, and enamelware.
The geospatial tool developed by USGS and DGGS found that the specialized granites that host tin and its associated critical minerals are found in the same areas of Alaska that are good hunting grounds for rare earths.
Beyond the REE prospective areas, the USGS geospatial tool identified the Lost River-Kougarok region on the Seward Peninsula and a stretch of the central Brooks Range as other good places to look for the granites that host this group of critical minerals.
The geospatial tool also proved to be effective in turning up new areas of Alaska to explore for the elusive platinum group metals – platinum, palladium, rhodium, iridium and ruthenium.
The largest use for this suite of metals, especially palladium and platinum, is as a catalyst to help scrub harmful emissions from internal combustion automobiles and petroleum refineries. These metals also are used in modern electronics, such as increasing storage on computer hard disks, and as an alloy for restorative dentistry. Platinum, palladium, and rhodium are used as investments and are commonly minted into physical bars and coins.
The United States currently relies on foreign sources for about 90 percent of these critical metals.
Though an economic lode-source of PGMs has yet to be discovered in Alaska, about 650,000 ounces of these obscure metals have historically been mined from Salmon River placer deposits in the Goodnews Bay area. This region of Southwest Alaska continues to be an intriguing place to look for PGMs, according to the USGS geospatial tool.
Other areas of the state, however, show higher potential. The best known of these is the Wrangellia terrane, a distinct belt of rocks along much of the southern slopes of the Alaska Range eastward through southern Yukon and into western British Columbia. While intriguing signs of rich deposits of PGMs are found in the Alaska portion of the Wrangellia, such as the Man property about 165 miles southeast of Fairbanks, an economic deposit has yet to be identified here.
The other regions where the USGS identified high PGM potential are:
• Angayucham terrane, a belt of rocks found along the northwestern slopes of the Brooks Range and south of the Brooks Range;
• Peninsular terrane, which stretches along the Chugiak Mountains in Southcentral Alaska; and
• most of the Southeast Alaska panhandle.
Carbonate-hosted critical minerals
As part of its critical minerals and metals investigation, USGS also looked at carbonate-hosted copper deposits, which often also host the critical minerals cobalt, germanium and gallium.
Cobalt is an important ingredient of super-alloys used to make aircraft turbine engines. This application makes up nearly half of the United States consumption of this critical mineral.
Germanium and gallium have properties that make them important minerals in a number of modern applications including solar cells, infrared optics, LEDs, semiconductors and smartphones.
The best known carbonate-hosted copper deposit in Alaska is Bornite, also known as Ruby Creek, in the Ambler Mining District along the southern slopes of the Brooks Range. While renowned for its high copper grades, Bornite also hosts significant quantities of cobalt and potentially other critical minerals.
To gain a better understanding of the distribution of cobalt at bornite and to study the carbonate-hosted deposit's potential for gallium, germanium and rhenium, USGS has entered into a technical assistance agreement with Trilogy Metals.
Interestingly, the USGS geospatial tool found that almost the entire length of the Brooks, especially the underexplored northern slopes of this range that stretches the entire width of Alaska, is prospective for the style of copper deposits known to host cobalt, germanium and gallium.
In addition, the USGS study identified two areas of the Seward Peninsula and a long stretch of the Wrangellia terrane as prospective for carbonate-hosted copper deposits that may have associated critical minerals.
Gold as critical mineral pathfinder
The USGS also applied the geospatial tool to the rich placer gold deposits Alaska is renowned for.
While gold itself is not a critical mineral, the erosion process that deposited gold into streams across Alaska also happened to concentrate other heavy critical minerals into placer deposits.
USGS points out that in addition to gold, these alluvial deposits in Alaska sometimes hosts valuable concentrations of platinum group elements, tin, tungsten, silver, rare earths and titanium.
Having the material already broken down to sands and gravels and concentrated into stream beds or other placer deposits means nature has completed the first stages of mineral processing, making the recovery of the precious and critical metals easier and less expensive.
The best known critical minerals bearing placer deposits in Alaska may be found along the Tofty tin belt, a 12-mile-long area of tin- and gold-bearing gravels in Interior Alaska's Manley Hot Springs district. Other gold mining districts in Alaska also have interesting quantities of tin, as well as tungsten.
When it comes to a wide array of critical minerals, the Ray Mountains area about 50 miles north of the Tofty belt may be the richest.
Ucore Rare Metals holds mining claims covering placer deposits in this area with potentially economic concentrations of REEs, tin, tungsten, tantalum and niobium.
Using gravity methods, Ucore concentrated placer samples from the property.
Assays of these concentrates returned up to 50 percent tin; as much as 10 percent rare earths; and 0.01 to 1 percent tungsten, tantalum and niobium.
USGS and DGGS identified 17 major areas of Alaska to seek the placer deposits that host gold, many of which could also carry critical minerals.
Overall, the geospatial tool seems to have broadened Alaska's critical mineral potential, while narrowing the search to the hottest areas across the 663,000-square-mile minerals-rich state.
"Using this process, we have identified the potential for critical minerals in new areas such as the northern Brooks Range, and have expanded the area with potential for resources around known mineralized areas like the Seward Peninsula and east-central Alaska," the authors of the study wrote in a summary of their findings.
For explorers, the new and under-explored areas turned up by the geospatial tool may provide enough data to make critical mineral discoveries in areas where no one has thought to look.
The authors of the report offer a tidbit of advice for such intrepid explorers: "Future geologic investigations should focus on areas that have relatively high potential scores but for which available data are limited."
Given the results of the critical minerals investigation, USGS believes the geospatial tool shows promise for identifying other deposits across the expansive Far North State.
"This study will help guide our minerals-focused geologic investigations for many years to come. We have so much left to learn about the basic geologic framework of Alaska, and now we have a great new geospatial tool to help make our research efforts more efficient and effective," said Jamey Jones, research geologist, USGS, and co-author of the study.
The full report – complete with source information, datasets and maps – can be found under the title "GIS-based identification of areas that have resource potential for critical minerals in six selected groups of deposit types in Alaska" in the publications section of the USGS website.