'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 attributed to remanent magnetism associated with a large meteorite impact at ≃2.0 Ga. The rocks that underlie the anomaly are shocked Archaean granites, 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 orientations, and are interpreted to have been intruded along the planar deformation features under extreme P-T conditions following the impact event.