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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
© Natural Environment Research Council © Natural Environment Research Council
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
© Natural Environment Research Council © Natural Environment Research Council
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
Electrical conductivity
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
Electrical conductivity
Gamma radiation
© Natural Environment Research Council © Natural Environment Research Council
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