Along a NW-SE profile through the basement core, starting below the sedimentary unconformity and ending in the center of the nearly circular structure, the constituent quartz grains and their fluid inclusions exhibit the following characteristics: In the NW, fluid inclusions composed of CO2 and occasionally up to 50 Vol.% H2O occur along shock-induced planar elements following predominently {0 0 0 1} of coarse, largely unrecrystallized quartz grains. The planar elements are partly still open microcracks, partly they are healed, the fluid inclusions decorating the former sites of the cracks. Along these planar elements recrystallization into fine grained new quartz fabrics starts, this process increasing decidedly towards the southeast; nevertheless fluid inclusions are still retained. — Near and within the center of the dome the formerly coarse quartz grains are completely recrystallized to medium grained annealing fabrics, in which — surprizingly — the fluid inclusions have often retained their original positions relative to the old grains, so that their planar alignment now traverses the new grain boundaries. Here the enclosed fluid is pure CO2 as far as can be determined. On the basis of the homogenization temperatures of the fluid inclusions measured, and of independent petrologic geothermometry of the basement rocks near the center, the fluids trapped after the shock event had exhibited partial pressures of CO2 as high as 3 kbars at temperatures around 850° C. The derivation of these CO2-rich, post-shock fluids is either through release of older fluid inclusions from the lower crustal granulites affected by the catastrophic shattering event, or it is from a direct mantle source that might be genetically connected with the Vredefort event itself.