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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...

Detecting Deeper Deposits of Uranium

RadonX is a new radon emanometry tool that’s helping to delineate buried uranium mineralization

By Virginia Heffernan

Already among the world’s top uranium producers, Namibia has become a hot spot for uranium exploration after several recent discoveries and expansions in the southwestern African country.

The new wave of explorers is deploying a mix of tools to outline mineralization. But a new radon detection technique adapted from dated technology is proving to be particularly amenable to conditions in Namibia, where radon gas can migrate to surface from buried uranium deposits through permeable cover strata.

“The Namib dune sands are highly porous and permeable. We are seeing radon leaking though to surface from bedrock from depths of up to 120 metres, which is phenomenal given radon’s half-life and that it decays relatively quickly,” says Branko Corner, a geophysicist who helped develop RadonX, a radon emanometry tool based on the Radon-on-Activated Charcoal (ROAC) technique developed by South Africa’s Atomic Energy Board in the 1970s and marketed commercially by Cape Town-based Remote Exploration Services (Pty) Ltd (RES).
 
Radon gas associated with uranium mineralization has a half-life of 3.8 days. About 80% decays within 12 days, and 100% within 30 days.

Radon detection is a common uranium exploration tool for buried deposits that are too deep to be detected by radiometrics, but the RadonX technique is different because it measures the gamma radiation emanating from the daughter products of radon (214Bi and 214Pb), rather than the alpha radiation emanating from the radon itself. As a result, RadonX has proved to be more sensitive and thus better able to highlight anomalies than alpha-sensitive methods.

To measure the gamma radiation, charcoal-filled cartridges are fitted to inverted plastic cups and buried for a period of about 10 days. The radon gas migrates to the surface along with the ground air and is adsorbed onto the charcoal. An on-site gamma spectrometer then measures emissions from radon’s daughter products. A lead castle is used to reduce and correct for background effects.

Corner uses Geosoft Oasis montaj to plot, process and visualize his RadonX data, using the ID FFT Filter add-on to filter and compare profiles.

The technique proved highly effective in a case study conducted at the Rössing South deposit, where Australia-based Extract Resources has outlined enough uranium mineralization to support a 15 million tonne per year open pit operation about 15 km south of the  well-established Rössing uranium mine east of Swakopmund. Extract describes Rössing South as the highest grade granite-hosted uranium deposit in Namibia and potentially one of the largest uranium deposits in the world.

Previous alpha-based radon emanometry trials over the blind deposit had suggested that Rössing South was probably not amenable to detection.  But when RES offered to complete a detailed grid survey using RadonX, there was a strong correlation between the mineralization buried at about 80 m below surface and radon gamma emissions (Figure 1), even though the readings were patchy because of impervious cover in areas.

“The deeper the occurrence, the more devious the pathways to surface,” says Corner. “The radon may reach surface in patches, following fractures in the overlying duricrust or cover sediments. It’s not necessarily a perfect correlation with the mineralization, but does constitute a very clear target anomaly for follow-up drilling.”

A couple of years ago, Cheetah Minerals Exploration - a private company Corner is involved with - decided together with its joint venture partners to dust off the old ROAC radon detection system and try it out on their exploration license. After some tinkering to improve sensitivity, the technique proved to be so effective in detecting uranium mineralization during case study trials, that Corner and his colleagues at RES decided to market the refined technology as RadonX.

RadonX is a qualitative technique best suited to the early stages of exploration, both to identify potential uranium targets and to rule out barren ground. Regional exploration using a relatively coarse grid (e.g. 200 x 500 m) can and should be enhanced by in-filling at closer grid spacing if the regional work warrants follow-up. Because measurements are made in the field, decisions about whether to initiate follow-up and where to place the detailed grid can be made almost immediately.  
   
The survey cost is based on the number of plastic cups used to bury the charcoal-filled cartridges. The basic cost is R325 (about US$44) per cup, including all deployment, collection and measurement, data reduction, grid preparation and report costs.  A discount may be offered depending on the size of the grid, or the need for further surveys.

In the case of palaeo-valley hosted uranium deposits commonly found in Namibia, a radon survey that detects the presence of uranium mineralization can be combined with an electromagnetic survey that effectively delineates the palaeo-valley where the mineralization occurs.

At the Tumas deposit in central Namibia, for instance, uranium mineralization is hosted in calcretized valley-fill sediments associated with a shallow (<25 m) palaeo drainage channel. Figure 2 shows an excellent correlation between the RadonX contours and the mineralized palaeo-channel outlined by resistivity mapping, despite the reconnaissance nature of the 200 x 500 m grid.
 
The latest palaeo-valley deposit to reach production in Namibia is Paladin Energy’s Langer Heinrich, which has a targeted annual production of 2.6Mlb U3O8 and a minimum project life of 17 years.  The deposit was discovered in 1973 during a government-sponsored airborne radiometric survey. Mineralization is near-surface, 1-30m thick and 50m-1100m wide, depending on the width of the palaeo channel.

Now the race is on to find the next Langer Heinrich or Rossing South under the desert sand and calcrete that covers much of the county. Explorers are motivated by the favourable geology and recent exploration successes, a mining friendly regime in Namibia, and the positive outlook for uranium demand.  As of August, 2009, there are 413 new nuclear reactors planned or proposed worldwide, up 30% from the same time last year, according to Resource Capital Research’s most recent quarterly report.

Two more Namibian mines, Areva’s Trekkopje and Forsys Metal's Valencia, are set for commissioning by 2011 and there are several advanced exploration projects that have bulk mining potential.

At Rössing South, Extract Resources has outlined a resource of 108m pounds of uranium oxide grading 0.043% U308.  Southwest of Rössing, Bannerman Resources has outlined 127m pounds grading 0.02% U308. And Deep Yellow is drilling high grade  mineralization in a new skarn-type mineral environment at its Inca project nearby.

The next generation of discoveries could catapult Namibia into first place among global uranium producers. Corner and his RES colleagues hope to play a part in the country’s mining renaissance by using radon gas to detect deeper deposits that previous radiometric surveys may have missed.