Magnetic fabric and its significance in the 1400 Ma Mealy diabase dykes of Labrador, Canada

Abstract

An anisotropy of magnetic susceptibility (AMS) study of the relatively fresh Mealy diabase dyke swarm indicates a correlation between the AMS and the deformational effects in the rocks. Several AMS components were revealed during experimental work on 211 samples that had been heated to 640°C during a paleomagnetic study and 22 fresh samples progressively treated in alternating fields. Seventeen sites with slight or no deformation have a magnetic fabric composed of two major components. The stable component has minimum and maximum principal susceptibility directions preferentially oriented vertically and along dyke strike (~N 60°E), respectively, suggesting that the dykes have not been tilted since their emplacement. The unstable component, removed by fields up to 250 mT, is attributed to induced (domain) anisotropy produced by mild tectonic stress during the Grenville Orogeny. -from Authors