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 appearto have preferred magnetic dipole orientations, and are interpreted to have been intruded alongthe planar deformation features under extreme P—T conditions following the impact event.

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