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Earth Explorer is an online source of news, expertise and applied knowledge for resource explorers and earth scientists.
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News & Views

News Archive

August 25, 2014

Exploration in the Tintina Gold Belt of Alaska & Yukon

Stretching in an arc almost 2000 km long across Alaska and the Yukon is the rich Tintina Gold Province (TGP) where over 50 million ounces of lode gold resources have been defined in the last 20 years...

August 20, 2014

Mining M&A activity jumps YOY in H1'14

There were considerably more mining project and company acquisitions announced in the first half of 2014 compared with the same period in 2013, although the averages of price paid and value of acquired commodities per deal were lower, SNL Metals & Mining data shows...

August 6, 2014

Fugro Survey to search Indian Ocean for missing Malaysian jet

Fugro Survey Pty. Ltd. will use two vessels towing underwater vehicles equipped with side-scan sonar, multi-beam echo sounders and video equipment to search for the missing Malaysian Airlines Boeing 777...

August 4, 2014

Why explorers have stopped exploring

Australia’s most successful mining prospector has warned juniors face unprecedented hurdles to bring projects to market as excessive regulation and high start-up costs threaten to derail the next leg of the resources boom...

August 1, 2014

Queensland prepared for uranium mining

The government of the Australian state of Queensland says it is now ready to accept applications for uranium mining projects following its announcement of a new regulatory framework. The state lifted its long-standing ban on uranium mining in 2012...

July 30, 2014

In Quebec, the energy future of the North is blowing in the wind

An ambitious multi-year trial is set to begin on what promoters are calling Canada’s first industrial-scale wind power and energy storage facility - a wind turbine generation and stockpiling system that will help power Glencore Plc’s Raglan nickel-copper mine on the Ungava Peninsula...

July 28, 2014

These New Gravity Maps Give Us An Entirely New Understanding Of The Moon

In 2012, NASA rang in the New Year with a fresh mission - sending the Gravity Recovery And Interior Laboratory, also known as GRAIL, spacecraft to the moon. As the first endeavor intended to study lunar gravity, its findings would help scientists better understand how rocky planets, like Earth, formed...

July 21, 2014

HPC's Role in Energy Exploration

How high-performance computing helps companies track down hidden fields of oil and natural gas. The easy oil and gas has already been extracted, and sophisticated discovery and extraction techniques are needed to extend production...

July 20, 2014

ENI signs deal to expand oil, gas exploration in Congo

Italian oil and gas group Eni said it signed a deal to explore for hydrocarbons in the Republic of Congo's coastal basin, expanding its foothold in sub-Saharan Africa's No. 4 oil producer...

July 20, 2014

Cameco: Light At The End Of The Japanese Tunnel?

Declining Japanese bond spreads bode well for the supply/demand dynamics of the uranium market and uranium stocks such as Cameco...

July 20, 2014

The tiger roars as the dragon sleeps

India's coal demand could hit 787 million t this year, according to coal and power minister, Piyush Goyal, with imports required to make up a more-than 200 million shortfall in domestic production...

July 14, 2014

Geosoft previews new Voxel Assisted Layered Earth Modelling technology for imaging base of salt

Geosoft previewed new Voxel Assisted Layered Earth Modelling (VALEM) technology at the EAGE 2014 in Amsterdam. Delivered within Geosoft’s GM-SYS 3D gravity and magnetic modelling environment, VALEM is a cloud-based gravity inversion service that improves imaging of base of salt and sub-salt regions...

June 30, 2014

Digital Tools for Mines Help Maintain a Competitive Edge

Many mining executives are convinced there’s really no alternative: either join the industry’s quickening interest in digital technology or risk losing ground...

June 24, 2014

Hottest lava eruption linked to growth of first continents

A collaborative research team has discovered an important link between the eruption of Earth's hottest lavas, the location of some of the largest ore deposits and the emergence of the first land masses on the planet - the continents - more than 2500 million years ago...

June 16, 2014

Drilling activity near Chibougamau: More than just Monster Lake

Quebec's historical Chibougamau mining district, located within the prolific Abitibi Greenstone Belt, is attracting renewed attention. Against a background of lackluster gold prices and generally low levels of exploration activity worldwide, one of the most recent market-dominating announcements came from the Monster Lake joint venture among IAMGOLD Corp. (50%), TomaGold Corp. (45%), and Quinto Real (5%)...

Where there is one VMS, there is usually another

by Virginia Heffernan on June 24, 2013 Applied

Panoramic view of the El Roble project site in Columbia. Atico Mining’s exploration program for El Roble is focused on discovering several million tonnes of high grade copper – gold ore.

In the high-stakes game of mineral exploration, companies that can test their model at an operating mine before venturing into the surrounding district are at a distinct advantage. It’s an approach that is paying off for Vancouver-based Atico Mining as the junior searches for volcanogenic massive sulphide (VMS) deposits near the El Roble copper-gold mine in Colombia.

“Having access to the mine workings helps us understand the geological and structural controls on mineralization,” says Atico CEO Fernando Ganoza, “and that in turn is helping us find additional resources.”

Atico uses the data collected from ongoing brownfields exploration combined with historical data to create 3D models using Geosoft’s Target and Geochemistry for ArcGIS. The models help guide exploration below the current workings and within the prospective host horizon that extends along strike from the mine.

“We input all of the geophysical and geochemical data into ArcGIS and then, based on the understanding of the geology, set parameters in the software,” explains Senior Exploration Manager Joseph Salas. “That’s how we generate targets.”

In early 2011, Atico signed a deal to earn a 90% interest in El Roble in return for paying its Colombian owners US$2.25 million in cash over two years plus a lump-sum payment of US$14 million due in January 2014.  Over a production history of roughly 22 years, the underground mine has turned out 1.5 million tonnes grading an average of 2.5% copper and 2.5 grams gold per tonne.

Field geology discussion.

“Having access to the mine workings helps us understand the geological and structural controls on mineralization and that in turn is helping us find additional resources.”
- Fernando Ganoza

Although most of the historical resource, consisting of several VMS lenses, has been mined, Atico has found more ore at depth. These new targets were established by mapping the geology both at surface (1:5,000 and 1:10,000 scale) and underground (1:250 scale), following structural controls and mineral zoning patterns typical of VMS deposits.

Geophysics and Geochemistry Zero in on Targets
On of the most significant conclusions from the surface mapping program is that the mineralized contact between basaltic volcanic rocks and black and grey cherts extends for 10 km across the El Roble concessions. Follow-up prospecting has confirmed that resistivity lows and chargeability highs can be used as indicators of the favourable chert horizon.

However, additional geophysical tools were needed to distinguish between conductive graphite in the chert and VMS mineralization. So Atico launched a ground magnetic orientation survey around the mine and reprocessed about 40 line-km of ground magnetic data collected in the mid-1980s by Nittetsu Mining, a former joint-venture partner on the property. The reprocessed magnetic map shows a weak magnetic anomaly over the El Roble mine and four stronger magnetic anomalies to the north.

In the air, Atico ran a 500-km versatile time-domain electromagnetic survey to cover the trend with lines every 100 m and a spacing of 50 m between stations. (Time-domain EM surveys are often effective in pinpointing VMS mineralization above a depth of 200 m.) A follow-up ground gravity survey further refined drill targets by identifying several anomalies that could represent pockets of VMS mineralization.

[Click to enlarge]

El Roble – Geology Section 20 South.

Although drilling along the trend has yielded little of interest so far, underground drilling is showing that a gold-silver halo in the black chert is a significant geochemical indicator that can be used for both brownfield and greenfield exploration. Results from the northern end of the operating mine include 119 m of 6.9% copper and 6.3 grams gold per tonne.

The host rocks at El Roble are part of the Cretaceous Cañasgordas Group, which can be traced for more than 800 km along the western cordillera of Colombia. Locally, mafic volcanic rocks include pillow basalts, tuffs, hyaloclastites, and agglomerates, while pelagic sedimentary rocks consist of chert, siltstone, and minor limestone.

The VMS mineralization is dominantly pyrite and chalcopyrite, mostly fine-gained and showing little internal structure or banding. Underground drilling between the 2,000- and 1,980-metre levels has identified stockwork mineralization consisting of chalcopyrite with subordinate pyrite in massive veins and patches in a gangue of stockwork quartz and chlorite veins.

Since VMS deposits tend to occur in clusters and the mined-out zones at El Roble represent only about half of what an average VMS cluster would yield, there’s a good chance Atico will find more ore along the 10-km trend as it uses information from the mine to seek out economic mineralization.

 


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