KIMBERLITE PIPES: GROWTH MODELS AND RESULTING IMPLICATIONS FOR DIAMOND EXPLORATION

1 Figure 1: The figure shows the root zone and the lowest part of the diatreme directly after the previous explosion and eruption (the overlying part of the diatreme and the crater is omitted from the drawing; see also Fig. 5). The country rock is highly brecciated and the explosion chamber is temporarily evacuated by the eruption through the feeder vent. Consequently a shortlived cavity forms at the site of the explosion. The dark grey band represents a hypothetical layer (bed) of a harder rock. Figure 2: The newly formed explosion chamber is filled by rockfalls and rockslides from the unstable brecciated side walls of the cavity and also by material subsiding from higher explosion chamber(s) and the overlying diatreme. Magma intrudes into the contact breccia (and possibly also into the rockfall breccia) and water is seeping and shooting in from the brecciated side walls, the overlying diatreme, and the aquifer or hydraulically active zone of structural weakness on which the volcano is forming. KIMBERLITE PIPES: GROWTH MODELS AND RESULTING IMPLICATIONS FOR DIAMOND EXPLORATION Volker Lorenz and Stephan Kurszlaukis 1 Institut fuer Geologie, Würzburg, Germany; 2 De Beers GeoScience Centre, South Africa