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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

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...

February 10, 2016

Cameco's new uranium discovery revealed

Canada's top uranium producer has a significant new discovery nearby to one of its largest existing mines...

February 9, 2016

NexGen Drills Most Intense Mineralization to Date at Arrow

NexGen announces further results from its on-going six rig 30,000 m winter 2016 drill program on its 100% owned Rook I Property in the Athabasca Basin, Saskatchewan...

February 9, 2016

Rio Tinto scales up its big data ambitions

Rio Tinto is opening its "vast troves" of exploration data to junior explorers in the hopes they will help sift for opportunities and supply ideas and labour...

February 8, 2016

Online portal improves access to geoscience data from Africa

The Botswana Geoscience Institute is launching a Geoscience Portal...

February 8, 2016

5 Best Minerals & Fossils To Buy With Your IRS Tax Refund

You just got your IRS tax refund and now you're presented with some cash to go out and buy one of a kind minerals and fossils from your local...

February 5, 2016

World's largest offshore windfarm to be built off Yorkshire coast

Dong Energy makes final investment decision on 1.2-gigawatt project that will power more than a million UK homes...

February 2, 2016

World's top 10 rookie gold mines

These high-grade mines will soon start competing with gold mining's industry leaders ...

January 25, 2016

Exxon Mobil Corp's defiant outlook predicts Canadian and Venezuelan oilsands output will 'quadruple' over next 24 years

In sharp contrast to the grim medium-term prognosis for the Canadian oilsands, Exxon Mobil Corp. is predicting sunnier times for bitumen in the decades ahead...

January 23, 2016

Magnetic Survey Keeps Cost Down

At a contaminated furniture factory site in North Carolina, a reconnaissance magnetic survey was conducted toward the end of a Phase 2 investigation ...

Steamy Prospects in Ethiopia

Deep magnetotelluric soundings in the East African Rift of Ethiopia reveal geothermal potential

By Graham Chandler

A major geological event that happened in continental Africa somewhere between 15 and 20 million years ago today pleases and fascinates at least two professions: paleoanthropologists and geologists. The African plate and the Somali sub-plate began to spread apart and form a massive rift that stretches some 3,000 kilometres running from the Red Sea in the north clear to the Zambezi River in the south.  Known as the East African Rift System, most of it is graben-like. Over the millennia, volcanic and erosion activity have left it with a lot of volcanic rocks along with sedimentary succession. It's what the process has exposed that interests these professionals.

For paleoanthropologists, it's a delight. The rift has uncovered sites like Olduvai Gorge, Laetoli and Hadar which have revealed early man finds that go back millions of years. Laetoli has human footprints that have shown humans were walking upright as long as 3.5 million years ago. And the well-known 3 million year old "Lucy" skeleton was found at Hadar in the Afar region of northeastern Ethiopia.

It is that region of the East African Rift System that interests geothermal specialist Mohammednur Desissa: the Main Ethiopian Rift, or MER, which covers about 150,000 square kilometres or nearly 15% of his country. The geophysicist from the Geological Survey of Ethiopia is concentrating in particular on the Dabaho rift segment of the MER for his MSc thesis at the University of Edinburgh.

Desissa explains. "It's situated very close to the Afar triple junction within the Afar Regional State, 600 kilometres northeast of Addis Ababa," he says. "The Afar region is an area of active extensional tectonics and volcanism where the Gulf of Aden, the Red Sea and the Ethiopian Rift Systems join." Of these three, he's investigating in the Red Sea arm, which is the southern part of this volcanic segment, around the Tendaho graben; around Lake Afar near the main highway to Djibouti. Desissa explains that each of the three rift arms have different rates of extension and that, coupled with weakening of the lithosphere from the Palaeogene mantle plume beneath Afar may have contributed to making the location of the triple junction unstable.

The instability Desissa speaks of holds great promise for exploration and development of geothermal energy for Ethiopia. While geothermal is not a new field for the country, progress has been slow. The potential has attracted the attention of geologists for a century or so, but serious geothermal exploration has been undertaken only over the past 40 years.

These geological, geochemical and infrared studies have revealed several active hot springs and fumaroles of around 177 degrees C. Desissa says strong thermal indications have been evident from gravity, magnetics and DC resistivity measurements too. Sixteen potential sites have been identified, that could provide 1,000 MW of power.

There's even one in production. "Aluto-Langano is the only locality where electric power is generated using geothermal energy in Ethiopia within the MER," notes Desissa. "It generates about 9MWe and is connected to the existing hydro power grid."

But he thinks there's so much more potential, especially the MER's southern sector around Lake Abaya whose fault centres are expected to be active heat sources. "MER is where the promising geothermal areas are situated," he says. "It's low lying and one of the most accessible areas of the country. The shallow geothermal source has been mapped at depths around 500 metres, while the deepest are below 1500 metres as proved by the magnetotelluric (MT) method and drilling." And the high measured temperatures add to the exciting potential: 250 to 300º C at 500 metres, he says.

It's Desissa's pursuit of the MT method that has upped the ante here—it tends to be more revealing in the MER's geology. "The MT method differs from other electromagnetic (EM) geophysical techniques that require artificial sources of EM energy to probe the earth," he says, and is therefore well adapted to deeper crustal investigations. Around the southern part of the MER in the Lake Abaya prospect area where several faults and volcanic activity are prevalent, a DC resistivity survey had previously been conducted but due to local topology and geography, sufficient information could not be obtained. Long electrode separations are impossible due to the rough terrain, high power generation is needed, and depth penetration is limited due to the upper resistive and conductive layers. "These problems are alleviated or at least minimized by going to the MT method," says Desissa.

He says the MT method became particularly useful in the Lake Abaya area and other parts of the MER because it's where highly resistive volcanic rocks overlay the conductive sedimentary strata. "The depth penetration of conventional DC resistivity methods and shallow seismic waves are not successful compared to the MT sounding due to the consolidated volcanic rocks." So in his project with the Geological Survey of Ethiopia he undertook to use the method to map and delineate the geo-electrical and geologic structures in the area, particularly the lateral and vertical extent of the active hydrothermal zones. His team set up electrodes 50 metres apart in several sections and recorded MT measurements. Electric and magnetic time series were first transformed into frequencies and the data processed to deduce which of the structures control the major thermal activities.

The data correlated well with volcanic remains and currently observed hot springs and smoking fumaroles in the surrounding areas. Building the geo-electrical models for 500 metres and 2000 metre depths, some tantalizing finds were revealed: geological conduits that could flow heat to the surface in more than sufficient amounts for geothermal energy sourcing. Particularly exciting was indication of a hot magma chamber at a shallow depth - less than two kilometres. The project's next step is to carry out further testing: closely spaced long period MT measurements that would further confirm the structure.

Meanwhile, the rift keeps spreading; but at a snail's pace. Geologists have speculated that the East African Rift system will eventually become the boundary of a new detached lithospheric plate and move northeasterly, forming a new ocean basin. That won't happen any time soon - by the time it does, paleoanthropologists and geologists will have entirely new species and structures to study.