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.

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