JMDMT #2100 Microfossils of Cyanobacteria in Carbonaceous Meteorites

The James M. DuPont Meteorite Collection - suggests that the unit probably does not represent an impact melt sheet topped by sedimentary and volcanic layers formed during crater modification [see also 17]. The presence of calcalkaline and tholeiitic volcanic units in the lower Rooiberg suggests that petrogenesis of the interval might be related to both subduction processes and plume magmatism. Calcalkaline and tholeiitic rocks may have resulted from melting of underplated and mantle rocks, respectively, by a short-lived mantle plume [2,8]. However, volcanic strata in the underlying Pretoria Group also include both calcalkaline and tholeiitic units and suggest that processes responsible for these rocks may have been active well before extrusion of the Rooiberg.