Rare Earth Elements and Rare Metals of Central Asia: A USGS Inventory

By Mark J. Mihalasky and others, U.S. Geological Survey. Fact Sheet 2017–3089, March 2018.

Why rare earths matter

Rare earth elements (REE) have unusual physical and chemical properties that make them essential to modern life — in computing and communications, clean energy and transportation, medicine, glass and ceramics, aerospace and defense, and metallurgy and chemical refining.

The rare earth elements — light (lanthanum to gadolinium) and heavy (terbium to lutetium, plus yttrium) — and the rare metals beryllium, scandium, niobium and tantalum, sometimes counted with them in central Asia. USGS.

• The U.S. position: about 10 percent of world REE reserves, but no production; the country imports its REE, mainly from China.
• Why concern has grown: soaring demand from new technologies; uncertain supply, with China producing over 95 percent of the world's REE; and REE's electronic, optical and magnetic properties, which nothing else matches.
• So: new sources outside China need finding and testing.

Central Asia re-emerging

Along the old Silk Road, central Asia has long moved people, energy and minerals between Europe and Asia. Once part of the Soviet Union, it produced REE and still supplies base, precious and rare metals (RM).

After REE prices jumped in 2007 and 2009 and spiked in 2011, Kazakhstan, Kyrgyzstan and Tajikistan revived interest in REE and reformed their mining sectors to attract investment. Good geologic information lowers risk for investors, so in 2012–13 the USGS evaluated the region's REE-RM resources, built an inventory of occurrences, and studied local capacity-building needs.

How the deposits formed

The deposits come from magmatic, metamorphic and sedimentary processes during repeated cycles of mountain building and later weathering, erosion and deposition. Between Precambrian cratons and blocks, younger mountain belts were welded together from continental and oceanic fragments through subduction, accretion, collisions and closing ocean basins in the Paleozoic and Mesozoic. The two largest:

1. the Central Asian Orogenic Belt — the Kazakh Steppe, Kazakh Uplands and Tien Shan of Kazakhstan, Kyrgyzstan and easternmost Uzbekistan;
2. the Tethys Orogenic Belt, including the Pamir Mountains of Tajikistan.

The inventory

384 occurrences, from showings to previously developed deposits:

• Recorded: location, geologic setting, deposit type, size, commodities, grade, minerals and age.
• Deposit types: at least 16, in 5 classes — igneous, metamorphic/metasomatic, sedimentary, surface weathering/erosion and uncertain.
• Host rocks: mostly alkaline igneous rocks, their weathered products, and metamorphic/metasomatic rocks; carbonatite and alkaline igneous deposits tend to be richer.
• Minerals: most often monazite, zircon, apatite, xenotime, pyrochlore, allanite and columbite.
• Ages: Cambrian to Quaternary, clustered at about 570–408, 360–248 and 144–38 million years ago.

Where undiscovered deposits may lie

The USGS mapped areas of interest — where alkaline igneous rocks and carbonatites occur, and prospects identified by state agencies and presented by geologists from Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan at a USGS workshop in Bishkek on September 16–17, 2013. They fall in six belts:

1. Uraltides — mainly weathered-crust occurrences, such as the large Kundybai deposit.
2. Kazakh Steppe — peralkaline, carbonatite and granitoid-related prospects, with related metamorphic and weathering occurrences.
3. Kazakh Uplands — peralkaline and granitoid occurrences, including the Verkhne Espe deposit.
4. North Tien Shan — many deposit types, and the best prospects for production: the Aktyuz cluster, including Kutessay II, which once supplied heavy REE and rare metals to the Soviet Union.
5. South Tien Shan — the most occurrences and types: igneous prospects in the east, pegmatites and sandstone-hosted uranium in the west.
6. Pamir — pegmatite, peralkaline and weathered-crust prospects, including Sungat in the west and Agadjan and Agandzhan in the east, tied to the Dunkeldyk and Pamir Pipes carbonatites.

Sources

Based on Rare Earth Element and Rare Metal Inventory of Central Asia, USGS Fact Sheet 2017–3089, U.S. Geological Survey; text by Mark J. Mihalasky, with the USGS Central Asia REE-RM team (Robert D. Tucker, Karine Renaud and Ingrid M. Verstraeten), funded by the U.S. Department of State; a work of the United States government in the public domain. The inventory is the USGS data release by Mihalasky and others (2017). The periodic table is taken from the fact sheet's PDF; its maps are left out because they include an Esri data layer.