Evidence from the Vredefort Granophyre Dikes points to crustal relaxation following basin-size impact cratering

The timescale of the modification stage basin-sized impact structures is not well understood. Owing to ca. 10 km erosion since its formation, Vredefort structure, South Africa, an ideal testing ground for deciphering post-impact modification. Here, we present geophysical and geochemical evidence from Granophyre Dikes, which were derived - now eroded melt sheet. dikes have been studied mostly in terms their composition, while timing duration emplacement remain controversial. We examined modern depth extent five dikes, with three inner crystalline core central uplift, two boundary between supracrustal collar using two-dimensional electrical resistivity tomography. found that terminate near surface (i.e., <5 m depth). In contrast, at core-collar extend a ≥ 9 m. These observations suggest are exposed lowermost terminus. addition, obtained bulk composition finding andesitic phase dikes. presence this indicates episodic into subvertical crater floor fractures. conclude dike formation was protracted occurred over time span least 104 years. sequential Dikes points horizontal extension crust below sheet above kinematic velocity discontinuity, crustal instability resulting dynamic collapse transient cavity.