On the first experimental phreatomagmatic explosion of a kimberlite melt

Detailed field investigations of kimberlite pipes of the Upper Cretaceous Gibeon Kimberlite Field in southern Namibia revealed geologic features which do neither agree with extensive nor with explosive vesiculation. In the pipe Hanaus 2, vesicle-free magmatic kimberlite intruded the diatreme as a plug. Here we report on the first experiments in which phreatomagmatic explosions were produced with remolten natural, non-fragmental magmatic kimberlite from the Hanaus 2 central plug as a best fit model kimberlite magma system. After water was injected into the melt under controlled conditions, the resulting water-melt mix was triggered by a low-energy shock wave (<1 J) and a violent explosion was obtained: High-energy shock waves of several 1000 J were generated and pyroclasts were ejected with a maximum speed > 400 m/s. (C) 1998 Elsevier Science B.V.