Seismic imaging of the complex geological structures in the southwestern edge of the Western limb, Bushveld Complex through focusing pre-stack depth migration of legacy 2D seismic data

Abstract

We reprocessed a 50-km long legacy 2D reflection seismic profile acquired in 1986, under a project funded by the National Geophysics Program to improve the delineation of complex geological structures that host the platinum-bearing horizons (known as the UG2 reef; a chromitite horizon) on the south-eastern edge of the Western limb of the Bushveld Complex and to investigate the continuity of the reef below the thick cover. The pre-stack seismic data quality was improved through conventional processing steps. We applied standard Kirchhoff pre-stack depth migration as well as advanced coherency migration techniques. Both imaging techniques yielded good structural images of the platinum deposits, their hanging wall and footwall rocks. In particular, the coherency migration technique has provided significantly better images in complex faulted regions, yielding a better understanding of the interrelationship between fault activity and platinum deposit distribution, and the relative chronology of tectonic events. Moreover, the regional geological structures (Crocodile River fault and Chaneng structure) that crosscut the profile are clearly defined.