Helicopter-borne magnetic, electromagnetic and radiometric geophysical survey at Andøya, Nordland County

Abstract

NGU conducted an airborne geophysical survey in Andøya area in August - September 2012. This report describes and documents the acquisition, processing and visualization of recorded datasets. The geophysical survey results reported herein are 2614 line km.The Geotech Ltd. Hummingbird frequency domain system supplemented by optically pumped Caesium magnetometer and 1024 channels RSX-5 spectrometer was used for data acquisition. The survey was flown with 200 m line spacing, line direction of 90\u00B0 W-E with the average speed 90 km\/h. The average terrain clearance of the bird was 56 m.Collected data were processed by AR Geoconsult ltd. using Geosoft Oasis Montaj software. Raw total magnetic field data were corrected for diurnal variation and levelled using standard micro levelling algorithm. EM data were filtered and levelled using both automated and manual levelling procedure. Apparent resistivity was calculated from in-phase and quadrature data for each of the five frequencies separately using a homogeneous half space model. Apparent resistivity dataset was levelled and filtered. Radiometric data were processed using standard procedures recommended by International Atomic Energy Association.All data were gridded with the cell size of 50 m and presented as a maps at the scale of 1:50 000.