'Super magnetic' rocks generated by shock metamorphism from the centre of the Vredefort impact structure, South Africa

A magnetic anomaly near the centre of the Vredefort impact structure is att ributed to remanent magnetism associated with a large meteorite impact at s imilar to2.0 Ga. The rocks that underlie the anomaly are shocked Archaean g ranites, which have extremely high remanent magnetism. We propose that the high remanence derives from elongated, micron-size single-domain magnetite particles found along shock-induced planar deformation features in quartz. The magnetite particles appear to have preferred magnetic dipole orientatio ns, and are interpreted to have been intruded along the planar deformation features under extreme P-T conditions following the impact event.