Project

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Fragmentation, eruption dynamics and depositional processes in mixed carbonatite - silicate volcanic eruptions

Applicant Mattsson Bjoern Hannes
Number 144421
Funding scheme Project funding (Div. I-III)
Research institution Institut für Mineralogie und Petrographie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geochemistry
Start/End 01.10.2012 - 30.09.2014
Approved amount 132'274.00
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All Disciplines (4)

Discipline
Geochemistry
Other disciplines of Earth Sciences
Mineralogy
Geology

Keywords (9)

carbon dioxide; lithofacies analyses; Fragmentation; explosive volcanic eruptions; nephelinite; carbonatite; Oldoinyo Lengai; magma mixing; pyroclastic deposits

Lay Summary (English)

Lead
Lay summary
Volcanic eruptions involving mixing of two magmas of widely different characteristics have been occurring on numerous occasions at the Oldoinyo Lengai volcano in northern Tanzania, including a recent eruptive episode in 2007-2008. Eruptions of these mixed magmas have resulted in surprisingly vigorous explosions that predominantly produce fine ash. One goal of this project is to investigate the processes involved in the fragmentation of the magmas, i.e., is the fragmentation process driven by exsolution of volatiles from the magmas themselves, due decreased solubility of CO2 in the hybrid magma, or by explosive interactions with an external water source? This project is based on extensive fieldwork, sampling and mapping of volcanic deposits to detect spatial and temporal variations in magma fragmentation and deposition occurring during the eruptions. The collected material will be subject to laboratory-based analyses in order to characterize their chemistry and mineralogy. The samples will be subject to mechanical sieving to retrieve grain-size distributions, and a variety of imaging techniques will be applied to quantify the shapes of the resulting pyroclasts as well as their vesicle content. In combination, these techniques will allow to constrain the physical mixing, eruption, and depositional processes involving two magmas of distinctively different chemistry and subsequently also different physical properties. Special emphasis is placed on the deposits generated in the most recent eruption of Oldoinyo Lengai, as this volcano is currently active and understanding the past behavior is an integral part of building a realistic hazard assessment for future eruptions.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
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
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.
Ash fall impact on vegetation: A remote sensing approach of the Oldoinyo Lengai 2007-08 eruption
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.
Magma mixing and forced exsolution of CO2 during the explosive 2007-2008 eruption of Oldoinyo Lengai (Tanzania)
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.

Collaboration

Group / person Country
Types of collaboration
Prof. Max W. Schmidt (IMP ETH Zurich) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Dr. Barry Dawson (University of Edinburgh) Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Dr. Eric Reusser (IMP ETH Zurich) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Prof. Dr. Jörg Keller (Albert-Ludwigs-Universität, Freiburg) Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Associated projects

Number Title Start Funding scheme
129985 Fragmentation, eruption dynamics and depositional processes in mixed carbonatite - silicate volcanic eruptions 01.08.2010 Project funding (Div. I-III)
140560 Eruptive history of the Oldoinyo Lengai volcano: Constraints on the stratigraphic record in northern Tanzania with implications for volcanological and anthropological research 01.01.2013 Project funding (Div. I-III)

Abstract

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.
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