Uncovering the southern Bushveld Complex, using reflection seismic and gravity data

Abstract

Abstract The Bushveld Complex is well explored at shallow mining levels, but the deeper structures of the complex remain unclear. Geophysical studies have been instrumental in shedding light on these deeper regions, including seismic, gravity, and magnetic studies. Reflection seismic line DG326 crosses a largely geophysically unstudied part of the Bushveld Complex, over 160 km. The seismic line starts south of the western limb of the complex and ends in the lower part of the eastern limb. The line covers the possible connection between the southern limb of the complex and the western and eastern limbs. Along the profile (from southwest to northeast), the seismic line crosses outcropping Transvaal Supergroup rocks underlain by Witwatersrand Supergroup rocks; Bushveld granites and granophyres; the large Dennilton Dome and rocks of the Rustenburg Layered Suite. The dome is made up of basement rocks surrounded by Transvaal Supergroup rocks and has brought Rustenburg Layered Suite rocks closer to the surface in the northeast. Connectivity was investigated between the southern and western limbs, however, poor seismic imaging below a strong shallow continuous reflector makes any conclusion impossible. Connectivity is, however, supported by gravity (~15 mGal high, with a width of around 15 km) and kimberlite data.