MINERAL EXPLORATION — Termites guide companies to gold

Termites can be a costly nuisance to urban dwellers, but, for companies exploring for gold in Africa, they can be used to save thousands of dollars and point the way to a bonanza.

The tiny, ant-like insects eat cellulose, the main constituent of wood, and are loathed the world over for their tendency to invade and destroy wooden buildings.

It is the relatively semi-arid, sparsely populated regions of Africa, such as the Sahel regions of Senegal, Guinea, Mali, Burkina Faso and Niger, where the concentration of termites has tended to be highest. However, desertification of the Sahel has accelerated in the past few decades, with most of the trees having been felled for fuel and marginal land placed under cultivation to feed a rapidly growing human population. As a result, the termites have all but disappeared, leaving behind mounds of up to several metres high and more than a metre across.

Gold belts underlie much of the Sahel region, which fills the void between the Sahara Desert in the north and the equatorial regions to the south. Companies exploring those belts have saved time and money by putting away their drills and taking advantage of work done in the past by the industrious insect.

Donald Burton, vice-president of exploration with Etruscan Enterprises (eet-v), says each of the 22 gold occurrences found in the Central zone of the Koma

Bangou project in Niger were found as a result of sampling termite mounds.

Termite mounds were ubiquitous at Koma Bangou (in which Etruscan holds 67%, state-owned ONAREM 23%, and the government 10%) and mound-sampling soon became the prospecting tool of choice.

As Burton explains, termites burrow into the ground in search of water, and, depending on the hardness of the rock and the depth of the weathering, can excavate to depths of more than 80 metres. “It’s like having a little drill going for you,” he says. “They’re taking tiny samples of saprolite and bringing them to surface, so if they go through a gold zone in the saprolite, they will also bring gold up.”

“Termite geochemistry,” as Burton calls the sampling method, became feasible when the detection limits of analysis for gold reached the parts-per-billion level in the 1970s. In termite geochemistry, gold levels of 50 ppb or higher are considered significant — some samples at Koma Bangou reached 500 ppb (0.5 gram gold per tonne).

If the termite mounds are sufficiently dense, assay values can be plotted and contoured on a map.

The downside of termite mound-sampling, however, is the problem of determining from what depth or lateral area a grain might have originated before being displaced by the insect. But, as Burton says, the method does “put you in the ballpark.” According to Burton, it is also possible, in certain circumstances, to wash termite mound material in a pan and count the grains of visible gold.

“You just take a shovel and dig out a piece of the mound. You don’t have to be very precise.”

At last report, Koma Bangou contained a resource of 10 million tonnes grading 0.97 gram gold per tonne. The project is considered uneconomic at current gold prices, though Etruscan still plans to build a test leach facility.

For now, the Tiawa project, also in Niger, is Etruscan’s top priority. Placer Dome (PDG-T) can earn a 51% interest in an 81-sq.-km portion of the Tiawa concession, which includes the Samira gold deposit, by paying US$50 million.

In addition, Etruscan has drilled significant gold intersections on a part of Tiawa known as Boulon Djounga West.

Meanwhile, Ashanti Goldfields (AHT.U-T) has used termite mound-sampling at its Bambadji gold project in Senegal, where it holds an option to earn a half interest from Iamgold (IMG-T). As a result of mound-sampling there, the company has concluded that gold mineralization could be closer to the surface than originally believed.

On the N’zima prospect in Guinea, termite mound samples taken in advance of drilling returned grades of up to 5 grams gold.

Last year, Auspex Minerals (APJ-V) employed termite mound-sampling methods in combination with shallow auger-percussion drilling at its Koulbaga gold property in southwestern Niger. As a result, Auspex identified 20 new gold targets, prospecting of which identified gold mineralization in five separate areas.

Although past small gold mining operations at the Ndori gold project of Pan African Resources (PARC-C) in southwestern Kenya centred on high-grade quartz vein systems, the company is using mound-sampling to test a theory that the area has potential for deposits that are low in grade, bulk-minable, hosted by quartz reef and shear zones, and related to intrusives.

At the Sakoira project of First Quantum Minerals (FM-V) in Niger, sampling of termite mounds and rubble was used to confirm the presence of gold over a strike length of more than 1 km.