We present a helicopterborne transient electromagnetic survey from a region at the North Sea coast in western Jutland, Denmark, carried out at a seriously polluted site with the dual purpose of assessing the extent of the pollution and mapping the coastal hydrogeology to provide data for remediation activities.

In this paper, we derive the staggered-grid finite-difference coefficients of arbitrary even-order accuracy for the first-order spatial derivatives by the dispersion relation and the least squares method, which can satisfy the specific numerical solution accuracy of the derivative on a wide frequency zone for elastic wave numerical modelling.

This paper introduces exploration clues for orogenic gold prospecting in the north-west of the Sanandaj-Sirjan metamorphic zone, north-west Iran. These are derived based on processing and interpreting airborne magnetic and radiometric data in order to identify favourable host rocks, and surface and subsurface structures.

Assuming without evidence that magnetic sources are magnetised parallel to the geomagnetic field can seriously mislead interpretation and can result in drillholes missing their targets. This paper reviews methods that are available for estimating the natural remanent magnetisation and total magnetisation of magnetic sources, noting the strengths and weaknesses of each approach.

The measurement of magnetic susceptibility, magnetic remanence and Königsberger ratios can be made in the field, either using a total field magnetometer or a new portable fluxgate device that is described. Various problems of using a magnetic susceptibility meter on non-ideal rock, core and chip samples can be avoided.

The resultant magnetisation vector of a compact magnetic source can be obtained through simultaneous inversion for geometry and magnetisation. The resultant magnetisation vector and induced field vector lie on a plane that intersects the transformed apparent polar wander path to provide estimates for magnetic remanence, susceptibility and age.