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© Natural Environment Research Council © Natural Environment Research Council

The Tellus Airborne Geophysical Survey

and Results

Mike Young

The Tellus Conference, Belfast, 17/18 October 2007

Geophysical surveying measures:

• Natural magnetic field• Shallow electrical conductivity variations • Surface radioactivity

• MAP surface and near-surface physical characteristics

• MODEL subsurface geological structure

We use the results for:Exploration for Earth resources• Shallow structural mapping • Basin interpretation• Geothermal sources

Environment management• Natural baselines• Anthropogenic effects• Hydrogeology• Soil carbon and peat• Radon

Geological Survey of Finland

British Geological Survey

Joint Airborne-geoscience Capability


MagnetometerGamma-ray detector

Electromagnetic coil

BGS-GTK geophysical survey aircraft

Aircraft systems• Aircraft De Havilland Twin Otter• Crew Pilot, co-pilot, navigator, engineer• Navigation Visual + real-time differential GPS• Position recovery DGPS + digital video• Altimetry Radar and laser altimeter


Specification

Distance flown 81,000 km

Flying speed ~ 210 km/h

Flight direction 345 degrees

Flying height 56 m rural250 m urban

Line spacing 200 m

Sampling: - Magnetic 6 - 7 m- EM 15 - 17 m- Radiometric 60 - 70 m

Airborne Geophysical Survey

Magnetics

Electrical conductivity

Gamma radiation

New imagery

Magnetic field

Geological mapping

Structural mapping

Regional geology and tectonics

Basin studies

Igneous rocks

Magnetic intensity

Improving quality of mapping

Magnetics

Platinum in Soils Magnetics

Nickel Magnetics

Total magnetic field

Lower Lough Erne

Upper Lough Erne

Total magnetic field & soil nickel

Dykes – outcrop scale

Cavanacaw

Curraghinalt

Magnetic field

Geological mapping

Structural mapping

Regional geology and tectonics

Basin studies


Geological mapping

Characterising soils and glacial material

Salinity

Pollution plumes

Embayment – different lithology

Omagh Thrust

Dalradian – low conductivity

Lack Inlier (Dalradian)

Carboniferous

Inlier Bounding FaultNEW CONDUCTOR

Electrical conductivity and gold occurrences in Co. Tyrone

Cavanacaw

Curraghinalt

Coastal salinity – Magilligan strand

Electrical conductivity –west of Strabane

Possible plume?

Gamma radiation

Geological mapping

Soil characterisation

Radioactivity baseline

Radon

Hot rock geothermal

Magnetics

Electromagnetics

Uranium gamma-ray

Uranium soil geochemistry Gamma radiation - Ternary

0

151 ppm

Magnetic and gamma-ray anomaliesSlieve Gullion

Magnetic Gamma-ray: Potassium-40

Camlough Fault

Newry Fault

Gabbro

Felsic Ring Dyke

Slieve Gullion – from the southeast

5 Km grid – in-house records

In-house radon estimation

Multi-variate analysis

Peat extent and thickness

ESTIMATE OF PEAT THICKNESS

y = 30.459x-0.5255

R2 = 0.8972

0

10

20

30

40

50

60

70

80

90

100

0.00 1.00 2.00 3.00 4.00 5.00 6.00

Peat Thickness in m

Cou

ntra

te -

Han

d Sp

ectr

omet

er

All remaining data after deletion of bogs and editing of outliers (345 data points)

R2 = 0.6143

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00

Peat Thickness in m

Tellu

s To

tal C

PS

Sperrins Type Section:Airborne TC vs Peat Thickness

y = 1202.1e-1.3661x

R2 = 0.8631

0

200

400

600

800

1000

1200

1400

0.00 0.50 1.00 1.50 2.00 2.50 3.00

Peat Thickness in m

Airb

orne

Tot

al c

ps

Magnetics


Gamma radiation


With acknowledgements to:• BGS and GTK survey and processing teams led by David

Beamish and Maija Kurimo

• Interpretation by Chris van Dam, Baz Chacksfield, Adrian Walker, Don Appleton, David Jones, Barry Rawlins and Cathy Scheib