Rock Magnetic Properties

Magnetic susceptibility and remanence measurements for ground and aeromagnetic survey interpretation

Recent developments in high-resolution aeromagnetic and gravity data acquisition using advanced marine and airborne techniques have produced dramatic improvements in the quality and useful geological information content of magnetic and gravity anomaly maps, The quality of modern data is such that the influence of intrasedimentary as well as basement structures can now frequently be discerned.

Thus, in addition to its more traditional role in ore mineral prospecting and in reconnaissance surveying for hydrocarbon exploration, magnetic surveying is now being used in all phases of hydrocarbon exploration. It is becoming widely accepted that simultaneous quantitative interpretation of magnetic and gravity data with seismic data, constrained by well-log and core information, holds the key to the full understanding of geological structure in the survey area.

However, quantitative interpretation of magnetic survey data using forward modelling techniques requires accurate specification of relevent physical properties of the anomaly source rocks. The most important of these are the magnetic susceptibility and the intensity and direction of natural remanent magnetism. In the past, little information has been available on remanent magnetism and so this property had often been ignored. Furthermore 'representative' values of magnetic susceptibility have been assumed, often with little justification. It is now apparent that the remanent magnetism often has similar magnitude to the induced magnetism and so cannot be ignored. Instead, it is important to obtain truly accurate measurements on core, or outcrop analogue samples.

Coremagnetics offers a complete service in the acquisition of rock magnetic data for aeromagnetic and ground magnetic surveying, including magnetic susceptibility, intensity and direction of remanent magnetism, Koenigsberger ratio and magnetic polarity determinations. We carry out studies on core samples, drill cuttings, resinated core slabs and outcrop samples and integrate these data with available published information to provide fully representative input parameters for magnetic survey interpretation.