carbon dioxide; lithofacies analyses; Fragmentation; explosive volcanic eruptions; nephelinite; carbonatite; Oldoinyo Lengai; magma mixing; pyroclastic deposits
Bosshard-Stadlin Sonja A., Mattsson Hannes B., Stewart Carol, Reusser Eric (2017), Leaching of lava and tephra from the Oldoinyo Lengai volcano (Tanzania): Remobilization of fluorine and other potentially toxic elements into surface waters of the Gregory Rift, in Journal of Volcanology and Geothermal Research
, 332, 14-25.
De Schutter Ann, Kervyn Matthieu, Canters Frank, Bosshard-Stadlin Sonja A., Songo Majura A.M., Mattsson Hannes B. (2015), Ash fall impact on vegetation: A remote sensing approach of the Oldoinyo Lengai 2007-08 eruption, in Journal of Applied Volcanology
, 4, 15.
Bosshard-Stadlin Sonja A., Mattsson Hannes B., Keller J. (2014), Magma mixing and forced exsolution of CO2 during the explosive 2007-2008 eruption of Oldoinyo Lengai (Tanzania), in Journal of Volcanology and Geothermal Research
, 285, 229-246.
In order to understand carbonatite volcanism, and the genesis of carbonatitic magmas, a wide spectrum of complementary studies needs to be conducted. By combining information retrieved from mineralogy, petrology, isotope geochemistry, with extensive field-based studies a more genuine understanding of how carbonatitic volcanoes work, and how the carbonatitic magmas are linked to the silicate rocks, will emerge. This continuation of SNF project 200021_129985 focuses on pyroclastic deposits generated in recent explosive mixed carbonatite-silicate eruptions of Oldoinyo Lengai volcano in northern Tanzania. This specific volcano is chosen for the present project because there exist abundant petrological, mineralogical and isotopic data in the published literature. However, detailed and systematic studies of its pyroclastic deposits and their field relations are lacking. Therefore, this project will close this informational gap by providing detailed field data that can be easily integrated with the existing studies to better understand carbonatite volcanism and to add constraints on the petrogenesis of the carbonatitic magmas. The project will give insights into the mixing, eruption, and depositional process involving two magmas of widely different chemical compositions and subsequently also very different physical properties. The project will also provide data on how natrocarbonatites and silicate magmas occur within the natural deposits at Oldoinyo Lengai. The pyroclastic deposits generated during the recent mixed eruption of Oldoinyo Lengai in 2007-08 is studied in detail, and the eruption dynamics will be established based on the measured spatial and temporal variations within these deposits. This proposal seeks funding for a 2-year continuation for a currently ongoing PhD-project to complete the field-based stratigraphic logging of the pyroclastic deposits, and the laboratory-based granulometric, petrographic, textural and geochemical analyzes. By combining the results from the field with the laboratory analyzes interpretations of eruption dynamics and fragmentation modes, as well as different emplacement mechanisms can be made. Understanding the past eruptive behavior is an integral part in building a realistic hazard assessment for any volcano.