2006 IRISH SCIENTIST YEAR BOOK

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Geological Survey of Northern Ireland
Mike Young
New geoscience surveys of Northern Ireland – progress of the Tellus Project

The geophysical survey aircraft passing the Scrabo Tower, County Down.

The Tellus Project at the Geological Survey of Northern Ireland is now in its third year. 2006 saw the successful completion of the rural and urban geochemical surveys and the low-level airborne geophysical survey of Northern Ireland. The Project is funded by the Department of Enterprise, Trade and Investment and the Rural Development Programme for Building Sustainable Prosperity.

Rural areas of have now been covered by three geochemical surveys:

  • Soil sampling at a spacing of one site per 2km2 at two depths, 20cm and 50cm,

  • Sampling of sediments from first and second order streams, at an average interval of one site per 2.16 km 2 of land area,

  • Stream water sampling at the same sites.


Stream sediment sampling in Co Antrim.

Nearly 30,000 samples have been collected and analysed for more than 60 elements and inorganic compounds by XRF, ICP and by fire assay, to the G-BASE standard established by the British Geological Survey (BGS). Trace element distributions broadly correlate with lithologies and reveal anomalies significant for mineral exploration and environmental monitoring. The characteristics of the gold mineralisation trend in Omagh are further defined and anomalous gold concentrations also occur in the soils of Armagh. High nickel values characterise the Antrim volcanics and elevated nickel occurs elsewhere in several locations. Environmental applications of the geochemical results include baseline mapping of trace-element concentrations in rural soils and detecting contamination of soils and streams. The data will contribute to compliance with the monitoring and baseline requirements of EU Framework Directives on soils and water.

The project sampled soils in Belfast and Londonderry at a closer interval of four sites per km2. Additionally in these urban areas, samples for organic analysis were collected at one site per km 2 and analysed for a range of semi-volatile organic carbon compounds, PCBs and other contaminants. These results will reflect the industrial history of these cities and provide baseline data for land-use planning and the prioritization of remediation work.

The low-level regional airborne geophysical survey of Northern Ireland began in July 2005 was completed by May 2006. The operation was flown for Tellus by the Joint Airborne-geoscience Capability, a partnership of BGS and the Geological Survey of Finland. The survey aircraft, a De Havilland Twin Otter, was equipped with two magnetometer sensors, a four-frequency electromagnetic (EM) system and a 256-channel gamma-ray spectrometer. The survey parameters were:

  • ground clearance: 56m over rural areas and 250m over populated areas,

  • line spacing: 200m,

  • line direction: 345° and 165°.


EM apparent conductivity draped on a digital terrain model of part of the Sperrin Mountains. Dalradian formations (low conductivity - grey), bounded by prominent conductive faults, contrast with more conductive Palaeozoic rocks (blue).

The airborne magnetic results refine existing structural mapping, notably by extending the mapping of dyke swarms and delineating regional and local faults. Prominent isolated magnetic anomalies include those of the Antrim basalts, the Slieve Gullion complex, the Tyrone and Newry Igneous Complexes and deep intrusions of as yet unknown provenance. The EM method maps predominantly shallow variations of electrical conductivity, of geological, pedological or anthropogenic origins. Electrical conductivity differences between the Dalradian, Palaeozoic and younger rocks are mapped and the tracks of major fault zones are evident. Areas of shallow soil and groundwater contamination and variations in salinity are detected, if large enough. The results are already being put to use in mapping land-fills and industrial contamination.

Gamma-ray results show gross differences in the radioactivity of different lithologies and soils. The principal isotopes mapped are those of the uranium and thorium series and potassium-40. The data are being used experimentally to improve the mapping of radon potential, radon being a short-lived gaseous isotope in the uranium and thorium series. Reduced gamma radioactivity indicates absorption by water or peat, and there is a very close correlation between the mapped outline of peat and a certain gamma-ray amplitude; the variation in this amplitude may be useful as a means of mapping peat thickness.

Tellus data are available under licence and GSNI wishes promote the widest possible use of this valuable new dataset. Several collaborative research projects have already been initiated and GSNI welcomes further applications and proposals.

Contact: Mike Young or Dr Marie Cowan,
Tellus Project, GSNI, Colby House, Stranmillis, Belfast BT9 5BF;
Tel 028 9038 8462;
E-mail: [email protected] , [email protected] .