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Earth Explorer is an online source of news, expertise and applied knowledge for resource explorers and earth scientists. Sponsored by Geosoft.

News & Views

News Archive

December 7, 2016

Geosoft introduces IP and resistivity inversion in VOXI Earth Modelling

Geosoft has added induced polarization and resistivity data inversion to its VOXI Earth Modelling 3D inversion software service. Geoscientists are now able to create detailed 3D models of conductivity and chargeability from IP and resistivity survey data with VOXI. The resulting models can assist in interpreting and targeting regions for mineral and environmental applications...

December 5, 2016

Mexico's Deepwater Round Exceeds Expectations

Some of the world's biggest oil companies showed up Dec. 5 and agreed to invest on the Mexican side of the Gulf of Mexico, proving that deepwater exploration still has a pulse despite challenging market conditions...

November 30, 2016

Magnetic inversion results for Ngamiland available for download

A regional-scale geophysical inversion of magnetic field data in the Ngamiland region of northwestern Botswana is now available for download from the Botswana Geoscience Portal, a partnership initiative of the Botswana Geoscience Institute, industry sponsors and Geosoft...

November 30, 2016

LIGO Resumes Search for Gravitational Waves

After a series of upgrades, the twin detectors of LIGO, the Laser Interferometer Gravitational-wave Observatory, have turned back on and resumed their search for ripples in the fabric of space and time known as gravitational waves. LIGO transitioned from their engineering test runs to full science observations at 8 a.m. Pacific Standard Time on November 30...

November 9, 2016

International Volcano Scientists Unite

For the first time, the United States will host the international Volcano Observatory Best Practices workshop, previously held only in Italy. The workshop will take place this month in Vancouver, Washington. It is designed specifically for volcano observatories around the world and their staff to exchange ideas and best practices with each other...

October 4, 2016

USGS Assesses Mineral Potential for Sagebrush Habitats in Six Western States

USGS has completed a comprehensive assessment and inventory of potential mineral resources covering approximately 10 million acres of Federal and adjacent lands in Idaho, Montana, Nevada, Oregon, Utah and Wyoming...

October 3, 2016

Uganda Targets Up to U.S.$100 Million for Mineral Exploration

Uganda is well endowed with mineral resources and, like many naturally-gifted African countries, is becoming keen on ensuring that these resources play a transformative role in its long-term structural transformation dream - the Vision 2040...

September 9, 2016

Small-Scale Fishers Get A Big Boost With First-Of-Its Kind Impact Investment Fund

Conservation organization Rare announces the Meloy Fund for Small-Scale Fisheries at Our Ocean Conference. The Global Environment Facility, one of the largest funders of conservation worldwide, will be investing $6 million into the fund...

September 1, 2016

Scientists take to the skies to track West African pollution

Scientists operating research aircraft over West Africa have detected organic materials in the atmosphere over a number of urban areas, contributing to concerns of the rise in pollution across the region...

August 17, 2016

New IGS Xplore prospectivity maps for Botswana

International Geoscience Services have released a series of base metal prospectivity maps for the Ngamiland District of northwestern Botswana using free geodata available on the recently-launched Botswana Geoscience Portal, hosted by Geosoft. The maps identify favorable areas for copper, zinc and lead mineralization using geological, geochemical and geophysical datasets downloaded directly from the portal.

August 11, 2016

NexGen Makes New High Grade Discovery

NexGen Energy reported the discovery of a new high grade zone of mineralization 4.7 km northeast of the Arrow Deposit as part of an on-going summer drilling program on its 100% owned, Rook I property, Athabasca Basin, Saskatchewan...

August 10, 2016

Rampion UXO Disposal to Take Place This Week

E.ON has confirmed that the two unexploded devices, detected along the Rampion offshore cable route will be safely disposed this week following the consultation with the Marine Management Organisation...

August 9, 2016

Diamonds In The Rough: E&Ps Find New Reserves In Mature Basins

The oil industry’s history demonstrates clearly that new plays and prospects have long been found in mature basins that were thought to be well on the way to being squeezed dry. Through the acquisition of new data, developing new concepts and coming up with fresh interpretations, long-producing basins around the world from the North Sea to Malaysia have continued to reveal new riches...

August 8, 2016

Northern Shield Identifies High Quality VTEM Targets at Séquoi

Northern Shield Resources announced the results of the interpretation and modelling of the VTEM survey from the Séquoi Property in the Labrador Trough of Quebec . Séquoi is owned 100% by Northern Shield and is being explored for Noril'sk style Ni-Cu-PGE massive sulphides. After geophysical modelling and interpretation of the VTEM data from Séquoi, six VTEM anomalies of significant interest have been identified...

August 3, 2016

Rio Tinto tailors big data drive to copper

Rio Tinto will put the weight of an exploration big data push and its newly-formed Growth and Innovation group behind its desire to identify a "tier 1" copper asset. Speaking at the annual Diggers & Dealers conference in Kalgoorlie, Growth and Innovation group executive Stephen McIntosh said Australia was "overdue for a tier 1" mineral discovery of any type...

August 1, 2016

Tetra Tech Awarded $200 Million Navy CLEAN Contract

Tetra Tech announced that it has been awarded a $200 million, single-award contract by Naval Facilities Engineering Command (NAVFAC) Atlantic. Through the Comprehensive Long-term Environmental Action Navy (CLEAN) contract, Tetra Tech will provide environmental engineering support services to installations within the NAVFAC Atlantic Area of Responsibility...

May 3, 2016

NATO Science for Peace and Security (SPS), MODUM Partners announce "Young Scientist Summer School on Sea Dumped Chemical Weapons"

This international project cooperates closely with CHEMSEA (Search and Assessment of Chemical Weapons) Project for and sharing and knowledge transfer...

April 12, 2016

Monday mad rush for gold stocks

Renewed optimism about the outlook for gold saw investors pile back into gold stocks, pushing many stock to 52-week highs in heavy volumes...

April 11, 2016

Medgold Resources: Continues to Expand the Boticas Gold Project, Portugal; Proposes $200,000 Private Placement

Medgold Resources is pleased to announce new assay results from contiguous rock-chip sampling from the Limarinho South zone at its Boticas gold project in Portugal, which include a highlight of 6.0m @ 5.7 g/t Au...

April 8, 2016

De-carbonizing our energy sector

Nuclear energy currently provides around 11 percent of the world's electricity. China, the European Union, the United States, India, Russia, South Korea, and other nations’ have major existing fleets...

April 1, 2016

Follow-Up Drilling Results Indicate Wide Gold Zones at Hendricks Gold Discovery

Gascoyne Resources Limited announced that it has received the final assay results from the 10,000 metre aircore exploration drilling programme...

March 26, 2016

The Oil Market Is Finally Hitting Its Breaking Point

After a significant reduction in investments over the past two years, oil companies can no longer overcome the production declines from legacy wells...

March 15, 2016

N-Sea Expands into the French Offshore Wind Industry

Subsea IMR provider, N-Sea, has signed a letter of intent with CERES Recherches & Expertise Sous-Marine and TechSub Industrie Environement, to provide subsea survey, installation and remediation services to the French offshore wind industry...

March 9, 2016

PDAC 2016 Convention Exceeds 22,000 Attendees

Optimism and opportunity abounded at the PDAC 2016 Convention of The Prospectors & Developers Association of Canada in spite of recent industry challenges...

March 3, 2016

6 Alpha Launches EOD Contracting Division

6 Alpha Associates, a specialist risk consultancy practice, with expertise in the assessment and management of unexploded ordnance, has launched a dedicated explosive ordnance disposal division...

Rare Earth Exploration

Exploration techniques for rare earth element deposits

By Virginia Heffernan

Once considered little more than geological curiosities, rare earth elements (REEs) are beginning to generate media buzz as their role in green applications such as hybrid cars and wind turbines becomes apparent.

China provides about 90% of the world’s REEs but has indicated lately that it would like to keep that supply to itself in future. So the race is on to find alternative sources that can begin producing a few years down the road, when demand is expected to exceed supply by several thousand tonnes annually.

But not all rare earth deposits are created equal and markets for their output tend to wax and wane in step with technological innovation. Some of the most sought after REEs have fairly recent applications. Neodymium, for example, is used in supermagnets for disk drives, hybrid cars and windpower generation and cerium is a key ingredient in automotive catalysts. On the other hand, the market for REEs used in CRTs is shriveling as flat-panel technology transforms the television market.

So the key is to find the kind of rare earth deposit that will be of value to the growing field of green technology and other high-tech applications. Ahead of the pack is Avalon Rare Metals, a Toronto-based company that recently raised $17.5 million in a tight-fisted market to further explore its advanced Thor Lake rare earth deposit in the Northwest Territories.

Thor Lake – discovered in the late seventies - is unique in that it is enriched in “heavy” REEs, which represent only about 1% of the physical weight but about 40% of the value of worldwide REE production. Some of the most valuable of these include dysprosium and terbium.

Unlike gold or base metal deposits whose fate depends on commodity prices, technology will drive mine development at Thor Lake, explains California-based newsletter writer John Kaiser, who is following “rare earth mania” closely and investing in juniors with promising REE deposits.

Avalon is currently outlining a modest 5-10 million tonne high-grade reserve while the market for rare earths remains limited, but the larger resource at Thor Lake represents and an opportunity to develop new technologies that rely on security of supply.

For explorers interested in finding the next Thor Lake, there are several exploration techniques available, from satellite imagery to geochemistry.

Economic concentrations of these REE-bearing minerals are generally hosted in, or associated with, alkaline igneous rocks and carbonatites, so the first step would be to identify environments where these complexes occur. They are generally circular and can be identified by imagery, even in deeply weathered or highly vegetated terrains. They also tend to cluster along linear belts such as the Kapuskasing structural zone in Ontario.
Airborne magnetic, radiometric, and gravity surveys can also be used to delineate host rocks. Because many carbonatite complexes are surrounded by mafic alkaline rocks, they often show up as a magnetic bull’s eye combined with a gravity low and ringed by a gravity high.

“In general, the host rocks to rare earth deposits are good geophysical responders,” says David Trueman, one of the main geological consultants on the Thor Lake project and an expert on REE exploration. “On the ground, geophysics is a secondary tool that might help look for responsive minerals affiliated with the deposit itself.”

Radiometrics, for example, can be an extremely useful technique if the REE deposit is associated with thorium or uranium, as they tend to be. Both Thor Lake and the Mountain Pass carbonatite in California, which has been mined for REEs since 1954, were first discovered during prospecting for uranium.

However, while associated radioactivity can help guide exploration for REE deposits, too much can make a deposit uneconomic. Because the cost to process and sequester radioactive waste is becoming prohibitive, companies worldwide have shifted away from using radioactive REE concentrates, effectively ruling out ores that contain thorium such as monazite, a common REE-bearing placer mineral. The most desirable deposits contain REE-bearing minerals that are relatively easy to break down and concentrate, such as fluoro-carbonates.

Geochemical prospecting is an effective tool because most REE minerals are heavy and resistant. Trueman would start with regional stream sediment or lake bottom sediment geochemical surveys to identify common rare earths such as cerium and yttrium and associated rare metals such as niobium and zirconium.  If the regional surveys proved successful, he would move into higher density soil and lithogeochemical sampling, coupled with ground radiometric and magnetic surveys to pinpoint drill targets.

Trueman notes that geology, in particular mineralogy, can also provide guidance. Greisening in highly altered syenitic rocks or derived pegmatites can indicate the presence of rare earths because the process occurs during the last stages of crystallization when REEs come out of solution. Minerals typically associated with this phase are quartz, albite, lithian mica polytypes, and fluorite.

But with all these tools on hand, where in the world would Trueman start his search? Probably, he says, in an exhumed rifting environment that is underexplored for REEs – the carbonatite and alkaline complexes of Brazil and Nigeria, for example.


Castor, B. and James B. Hedrick. Rare Earth Elements, 2006. Pages 769-792 in Industrial Minerals and Rocks. Edited by Jessica Elzea Kogel, Nikhil C. Trivedi and James M. Barker.  Society for Mining, Metallurgy and Exploration.

Haxel, Gordon B., Hedrick, James B. and Greta J. Orris, 2002. Rare Earth Elements – Critical Resources for High Technology. USGS fact sheet.