RADIOMETRI

As an addition to NGU’s general geophysical mapping in Trøndelag, NGU conducted a high-resolution airborne geophysical survey in Meråker area in Trøndelag County on request of Norra Metals. This report describes and documents the acquisition, processing and visualization of the acquired datasets and presents them in maps. The geophysical surveys consist of 1054 line-km data, covering an area of 219 km2 flown on July 21st, 2021.
The NGU modified Geotech Ltd. Hummingbird frequency domain electromagnetic system supplemented by an optically pumped Cesium magnetometer and the Radiation Solutions 1024 channels RSX-5 spectrometer mounted on a AS350-B3 helicopter was used for data acquisition.

As an addition to NGU’s general geophysical mapping in Nordland, NGU conducted a high-resolution airborne geophysical survey in Bleikvasslia area in Nordland County on request of Norra Metals. This report describes and documents the acquisition, processing and visualization of the acquired datasets and presents them in maps. The geophysical surveys consist of 326.7 line-km data, covering an area of 59.3 km2 flown on August 21st, 2021.
The NGU modified Geotech Ltd. Hummingbird frequency domain electromagnetic system supplemented by an optically pumped Cesium magnetometer and the Radiation Solutions 1024 channels RSX-5 spectrometer mounted on a AS350-B3 helicopter was used for data acquisition.

As an addition to NGU’s general geophysical mapping in Agder, NGU conducted a high-resolution airborne geophysical survey in Evje & Hornnes and Iveland area in Agder county on request of Norse Minerals AS.
This report describes and documents the acquisition, processing and visualization of the acquired datasets and presents them in maps. The geophysical surveys consist of 301 line-km data, covering an area of 31.5 km2 flown on June 12th, 2021.
The NGU modified Geotech Ltd. Hummingbird frequency domain electromagnetic system supplemented by an optically pumped Cesium magnetometer and the Radiation Solutions 1024 channels RSX-5 spectrometer mounted on a AS350-B3 helicopter was used for data acquisition.

NGU conducted an airborne geophysical survey in Selbusjøen area, in Klæbu, Trondheim, Malvik and Selbu municipalities in Trøndelag County, as part of NGU’s general airborne mapping program. The data acquisition was carried out from August 10th to September 9th, 2023.
This report describes and documents the acquisition, processing and visualization of the acquired datasets and presents them in maps. The geophysical survey consists of 2841 line-km data, covering an area of 591 km2, flown from the base at Vassfjellet ski centre. The last flight consisting of re-flown lines to improve the magnetic data was flown from the base in Okkenhaug near Levanger.
The NGU modified Geotech Ltd. Hummingbird frequency domain electromagnetic system supplemented by an optically pumped caesium magnetometer and the Radiation Solutions 1024 channels RSX-5 spectrometer mounted on a AS350-B3 helicopter were used for data acquisition. The data collected were processed at NGU using Geosoft Oasis Montaj software. Raw total magnetic field data were corrected for diurnal variation and levelled using Geosoft micro-levelling algorithm. Radiometric data were processed using standard procedures as recommended by International Atomic Energy Association (IAEA). Electromagnetic data were filtered and levelled using both automated and manual levelling procedures. Apparent resistivities were calculated from in-phase and quadrature data for three coplanar frequencies (880 Hz, 6.6 kHz and 34 kHz), and for two coaxial frequencies (980 Hz and 7 kHz) separately using a homogeneous half-space model. All data were gridded using cell size of 50x50 meters and presented as 40% transparent grids on top of topographic maps.

Following a short historical review of uranium prospecting in Norway, most of which has been done by the Geological Survey of Norway, a simplified description is given of radioactivity, radiation, instruments and methods of measurements, and the dangers to health from naturally occurring radioactive sources. The main part of the paper concerns a description of uranium prospecting in Norway. The different methods used by the Geological Survey and the areas surveyed by each method are described, comments are given on each prospecting method used. Geological modelling in prospecting is based on a knowledge of the geological environment of known deposits and on parallels drawn with known uranium provinces, especially those in the Nordic countries Sweden and Finland. Only a few per cent of Norway's land area has been covered by radiometric airborne (helicopter) surveys of sufficient quality. More than half of the country has been surveyed by car, i.e. areas where measurements have been made along all the available roads. Geochemical methods have been used, mainly stream sediment sampling, with reasonably good results. Extensive areas have been covered but with uneven and mostly low ampling densities. All work up to 1983 is included in the overview. A short description of the main uranium mineralizations, including literature references, is presented.

NGU conducted an airborne geophysical survey in Forollhogna area, in Rennebu, Midtre
Gauldal and Holtålen municipalities in Trøndelag County, and Tynset, Tolga and Os
municipalities in Innlandet County, as part of NGU’s general airborne mapping program. The
data acquisition in Forollhogna area was carried out from June 23rd to July 20th, 2021.
This report describes and documents the acquisition, processing and visualization of the
acquired datasets and presents them in maps. The geophysical survey consists of 8214 linekm data, covering an area of 1609 km2, flown from the base near Orvos (Flight 1-38) and from
the base near Frigården (Flight 39).
The NGU modified Geotech Ltd. Hummingbird frequency domain EM system supplemented
by an optically pumped Cesium magnetometer and the Radiation Solutions 1024 channels
RSX-5 spectrometer mounted on a AS350-B3 helicopter were used for data acquisition.
The data collected were processed at NGU using Geosoft Oasis Montaj software. Raw total
magnetic field data were corrected for diurnal variation and leveled using Geosoft microlevelling algorithm. Radiometric data were processed using standard procedures as
recommended by International Atomic Energy Association (IAEA).
EM data were filtered and leveled using both automated and manual levelling procedures.
Apparent resistivity was calculated from in-phase and quadrature data for three coplanar
frequencies (880Hz, 6.6kHz and 34kHz), and for two coaxial frequencies (980Hz and 7kHz)
separately using a homogeneous half space model.
All data were gridded using cell size of 50x50 meters and presented as 40% transparent
grids with shaded relief on top of topographic maps.

NGU conducted an airborne geophysical survey in Røros, Trøndelag county as part of
NGU’s general airborne mapping program in 2020.
This report describes and documents the acquisition, processing and visualization of the
acquired datasets and presents them in maps. The geophysical surveys consist of 2584 linekm data, covering an area of 523 km2 flown between June 15th to June 22nd, 2020.
The NGU modified Geotech Ltd. Hummingbird frequency domain EM system supplemented
by an optically pumped Cesium magnetometer and the Radiation Solutions 1024 channels
RSX-5 spectrometer mounted on a AS350-B3 helicopter was used for data acquisition.
The survey was flown with 200 meters line spacing, azimuth 90o
. Average speed was
95 km/h, and average height clearance of the EM bird was 47 m and 77 m for the
spectrometer.
Collected data were processed at NGU using Geosoft Oasis Montaj software. Raw total
magnetic field data were corrected for diurnal variation and levelled using standard levelling
algorithm. Radiometric data were processed using standard procedures recommended by the
International Atomic Energy Association (IAEA).
EM data were filtered and levelled using both automated and manual levelling procedures.
Apparent resistivity was calculated from in-phase and quadrature data for three coplanar
frequencies (880 Hz, 6.6 kHz and 34 kHz), and for two coaxial frequencies (980 Hz and 7 kHz)
separately using a homogeneous half space starting model of 1000 ohm-m.
All data were gridded using cell size of 50x50 meters. Magnetic and radiometric data is
presented as 40% transparent grids with shaded relief on top of topographic maps. EM data is
presented as 30% transparent grids on top of topographic maps.

Oppdraget inngår som del av den flymagnetiske kartplan for Norge. Det ble også utført radiometriske målinger. Målingene ble utført 1961. Prosjektleder I. Aalstad, H. Håbrekke.

Som et forsøk ble det foretatt en magnetisk, radiometrisk og elektromagnetisk måling fra fly over et ca. 400 km2 stort område nordvest for Røros. Hensikten var å utprøve det elektromagnetiske måleutstyr bygget av Geofysisk Malmleting over et område med kjente indikasjoner på elektriske ledere. Under målingene opptrådte en del feil og forstyrrelser med E.M. utstyret og denne rapport om- handler bare de magnetiske og radiometriske målinger. En omtale av de elektro- magnetiske målingene er senere gitt i BVLI's Tekniske rapport nr. 45, "Geofysikk i malmleting" side 73-77. De radiometriske målinger ga ingen anomalier.

Målingene dekket hele Østfold fylke og søndre del av Akershus. Oppdraget inngår som del av den flymagnetiske kartplan for Norge. Det ble samtidig utført elektromagnetiske og radiometriske målinger. Målingene ble utført 1961 og 1962. Prosjektleder I. Aalstad, H. Håbrekke.