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Snooping under Northern Ireland: The Tellus Initiative

Intensive aerial and ground data gathering by the Tellus Project produces extensive multi-use geophysical and geochemical data and collects five awards along the way

By Graham Chandler

When you have to survey 14,000 square kilometres flying straight lines 200 metres apart just 56 metres above the ground—250 over cities—you’re faced with a massive public relations exercise.

The Tellus Project had to do just that; in order to collect the most extensive airborne geotechnical dataset ever forfor Northern Ireland in the UK. The result has been well worth it: matched with two gigabytes of raw geochemical ground data, the ten gigabytes of aerial geophysical data have now been processed and are on the market. Resource companies, government departments and academics have been flocking to it.

Low-flying airplanes attract attention; and two-thirds of Northern Ireland’s population live outside major cities. Many have livestock that could be traumatized. So Tellus engaged a leading PR firm, Weber Shandwick, to handle a heads-up program.

"Public outreach before the airborne survey was substantial," recounts Michael Young of the Geological Survey of Northern Ireland (GSNI) and manager of the Tellus Project. "It included letters to registered landowners, the police, the Coast Guard, district councils as well as special interest groups." These included "horse owners, chicken farmers, deer farmers, riding schools." Posters, notices, presentations, media interviews and airtime rounded out the advance notice. A hot line was set up to field complaints as the flying progressed.

The blitz was effective. Weber Shandwick and the project garnered three PR industry awards for the campaign.

The survey had been long overdue; without it, effective land and resource management in the province would languish. Previous airborne geophysical surveys in Northern Ireland were flown back in the 1960s; since then acquisition, processing and interpretation technologies have advanced by several generations.

From the start, Tellus was designed to be more than the usual airborne geomagnetic resource surveys. "Most intensive airborne surveys worldwide are undertaken for hydrocarbons or minerals," says Young. "The Tellus airborne specifications are equally appropriate for baseline environmental surveys."

The data were collected between 2004 and 2007, with the flight segment from July 2005 to May 2006. Managed by GSNI, the project had logistical input from the British and Finnish Geological Surveys who jointly operated the survey airplane, a De Havilland Twin Otter equipped with two magnetometers, a four-frequency electromagnetic system and a 256-channel gamma-ray spectrometer.

The low-level flight plan gathered magnetic, electromagnetic and radiometric data flying alternating parallel legs in opposite headings of 165° and 345°. For the ground program, multi-element geochemical data were obtained from stream water, sediments and soils. Soils were analyzed for organic and inorganic compounds.

On board the Twin Otter, magnetic data went through a MAGCOR software package, which applied a diurnal and several other corrections. The data were then imported into Geosoft Oasis montaj which corrected for all remaining errors such as spikes and VHF communications interference, then used MAGLEV for data leveling. Geosoft was also used to process the Caesium-137 radiometric data from the spectrometer.

All of which attracted yet another award. "Our results with Geosoft helped Tellus win the 2008 Innovation & Best Practice award from the UK Association for Geographic Information," says Young.

There’s a global warming aspect to the Tellus project. As soils are a significant store of carbon, integrating radiometric and soil survey data can improve estimates of soil organic carbon. "BGS soil scientists are using geostatistics to combine Tellus airborne radiometric potassium data with ground measurements of organic carbon to improve our estimation of carbon stocks in soils," says Young. He adds that reporting soil carbon stock is a requirement in the European program to establish national carbon stock levels in order to manage carbon sequestration.

Another environmental aspect was to examine radioactivity over the province. The Tellus project extrapolated radon levels from both the geochemical and the geophysical data, as there is strong correlation between uranium in soil samples and uranium measured radiometrically. The Palaeogene intrusives of the Mourne Mountains are the most radioactive rocks in Northern Ireland, so pulling together this dataset presents an opportunity to inform the public of the risks of radon exposure.

Which is important. "Radon is the second biggest cause of lung cancer and is thought to account for 1,100 deaths in the UK annually," says Young. He says they used multivariate geostatistical analysis to improve estimates of radon risk "We have been able to produce a more scientific risk map; previous maps only involved contouring in-house radon measurements, which are very sparse." Indeed, the Journal of Environmental Radioactivity last October reported a program examining the use of Tellus project airborne gamma-ray spectrometer and soil geochemical data to supplement in-house measurements and predict the probability of houses in Northern Ireland having high indoor radon concentrations.

"We also mapped Caesium-137, a wholly artificial isotope produced by nuclear weapons testing and the Chernobyl 1986 accident," says Young. "Current levels are low but we see clear associations with rainfall patterns and elevation." He says these levels provide a useful baseline dataset for mapping any future incidents.

An October 2007 story in the Belfast Telegraph even reported Tellus had discovered an underground hot springs near Larne that "could have the potential to provide heat and electricity for several of Northern Ireland’s towns and cities." It was reported that hot rocks 3,000 metres under the surface had heated the natural groundwater at the site to about 90 degrees C, and private sector companies could soon tap into this natural energy source. 

But Young says that was a bit optimistic. "The Larne thermal anomaly was discovered by previous drilling," he says. He explains the Tellus data did provide improved information to support structural mapping in this area but couldn’t directly detect geothermal resources. However further geophysics and drilling planned for the next phase of Tellus this year will further elucidate "this low-enthalpy geothermal resource," he says.

No alarming geohazards were detected by the survey. "The most striking results were the magnetic images and the great detail shown on dykes, faults and intrusives," says Young. "All of which will significantly improve our geological map revisions."

However some toxic findings had pause for concern. "The main toxic element anomalies are high nickel and chromium over the Antrim lavas, which significantly exceed the Soil Guideline Values (SGVs) for residential development," says Young. "And high arsenic values are associated with mineralized areas in the west and south." He says high values of nickel and chromium in the Belfast urban surveys are due to the naturally high soil levels. Other elements in the urban results like arsenic and lead, due to past industrial activity, were also found to be higher than the SGVs at isolated spots. But, "on the whole, says Young, "Belfast appears significantly cleaner than other UK industrial cities surveyed."

The digital data are now available in along-line or gridded formats, according to the GSNI website. Who have been the biggest customers so far? "Mining companies," says Young. But academia isn’t far behind. "Some 25 university researchers and MSc or PhD students have licensed the data for various projects," he says. "Geochemistry of soils, agriculture, highway planning, roadstone mapping, peat mapping, water catchment chemistry, geostatistics, etc." He says local planners have been relatively slow to take up the data but "we expect these data to provide this sector with essential environmental baseline data in the future." Of government departments, the largest user may be the Department of the Environment where the geochemical baseline will be used to meet several EU directives.

Commercial use of the data blooms. Three companies are exploring for potential natural gas storage in Permian salt beds. Resource corporations interested in gold and base metals have shown much interest in the new data, says Young. "Gold shows are widespread—the Tellus geochemical surveys have detected numerous anomalies in soils and stream sediments in rocks of the Neoproterozoic Dalradian Supergroup," he says. "Companies active here include Dalradian Gold and Toronto-based Galantas Gold Corporation’s Omagh Minerals." And prominent gold anomalies detected in the Lower Palaeozoic rocks of the southeast across the border from the Republic of Ireland’s million-ounce deposit at Contibret have sparked some excitement from Conroy Diamonds and Gold Ltd, which hold several licenses in Northern Ireland, he says. Young adds that the world’s third largest platinum producer, Lonmin plc, is pleased about clusters of platinum anomalies overlying the Palaeogene Antrim lavas too.

"Since the results were released the area of land licensed for [mining exploration] in Northern Ireland has increased from 15% to 70%," says Young, "and £15 million has been committed in exploration license agreements." Recognizing the country that has done most to promote mineral development, along came yet another award: Northern Ireland and the Tellus project were presented with the Mining Journal’s 2008 Outstanding Achievement Award.

All these awards don’t mean Tellus will sit back on its laurels. There’s more to do with the data. The Northern Ireland government has allocated £2 million for further follow up. Young says it will be spent on things like developing web-accessible indexes and value-added reports and products, 3D regional and urban geological modeling and a 3D visualization suite. And the airborne data, which have so far been interpreted only at a regional scale, will be interpreted at the 1:50,000 scale and used to revise the 1:50,000 geological maps and to map environmental effects in detail. This is to include prospectivity analysis and mapping as well as targeted research on specific mineralization. Research in geochemistry for agriculture and survey and basin interpretation for geothermal resources will round out the future of this intensive data-gathering exercise.