Chiedozie Collins Ogbuagu

The explosive eruption of carbonatite and associated pyroclast textures

Name: Chiedozie Collins Ogbuagu
Primary Supervisor: Prof Silvio De Angelis
Year: 4
Discipline: Earth Sciences 
Presentation type: 6 Minute Talk
Project Title: The explosive eruption of carbonatite and associated pyroclast textures

Abstract:

Explosive eruptions of low-viscosity lava, such as basalts and basanites, are widespread and are a dominant form of volcanism on Earth. They commonly display Hawaiian and Strombolian eruption styles and are relatively well documented. Carbonatite is another magma composition characterised by low melt viscosity. However, carbonatite eruptions are not frequent and documented examples of explosive carbonatite eruptions are minimal. Here, we examined the textural features of carbonatite pyroclasts from the Miocene Kaiserstuhl Volcanic Complex, which hosts both intrusive and extrusive suites of carbonatite rocks. Three pyroclastic rock samples from the Kirchberg and Henkenberg regions of the complex were studied using optical petrography, scanning electron microscopy, and image analysis techniques. Our observations show that the pyroclasts, after primary fragmentation, underwent in-flight deformation and experienced pyroclast-pyroclast collisions to form complex, agglutinated pyroclasts. Further image analysis has enabled us to reconstruct the primary grain size distribution, which represents the primary formation of pyroclasts and their textural features before agglutination. Finally, these data are used to investigate and elucidate the fragmentation processes and provide valuable information on the intensity of explosive carbonatites eruptions.

Keywords: carbonatite, in-flight deformation, agglutination, textural features, grain size distribution