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New augite and enstatite pyroxene standards for SIMS oxygen isotope analysis and their application to Merapi volcano, Sunda arc, Indonesia
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(English)Manuscript (preprint) (Other academic)
National Category
Geosciences, Multidisciplinary
URN: urn:nbn:se:uu:diva-267452OAI: oai:DiVA.org:uu-267452DiVA: diva2:873219
Available from: 2015-11-23 Created: 2015-11-23 Last updated: 2016-04-27
In thesis
1. Characterising volcanic magma plumbing systems: A tool to improve eruption forecasting at hazardous volcanoes
Open this publication in new window or tab >>Characterising volcanic magma plumbing systems: A tool to improve eruption forecasting at hazardous volcanoes
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis attempts to develop our understanding of volcanic magma plumbing systems and the magmatic processes that operate within them, such as fractional crystallisation, crustal partial melting, assimilation, and magma mixing. I utilise petrology, rock and mineral geochemistry, and isotope systematics to seek to improve our ability to forecast the eruptive frequency and style of active volcanoes, an aspect often lacking in current volcano monitoring efforts. In particular, magma reservoir dynamics are investigated from a mineral scale at Katla volcano in Iceland, to a sub-mineral scale at Merapi, Kelud, and Toba volcanoes in Indonesia.

The magma plumbing architecture of Katla volcano on Iceland is explored in the first part of this thesis. Crystalline components within tephra and volcanic rock preserve a record of the physical and chemical evolution of a magma, and are analysed through oxygen isotopic and thermobarometric techniques to temporally constrain changes in reservoir depth and decode the petrogenesis of the lavas. We find both prolonged upper crustal magma storage and shallow level assimilation to be occurring at Katla. The results generated from combining these analytical strands reveal the potential for unpredictable explosive volcanism at this lively Icelandic volcano.

The second part of this thesis examines the magma plumbing systems of Merapi, Kelud and Toba volcanoes of the Sunda arc in Indonesia at higher temporal and petrological resolution than possible for Katla (e.g., due to the crystal poor character of the rocks). For this part of the thesis, minerals were analysed in-situ to take advantage of sub-crystal scale isotopic variations in order to investigate processes of shallow-level assimilation in the build-up to particular eruptions. We find that intra-crystal analyses reveal an otherwise hidden differentiation history at these volcanoes, and establish a better understanding as to how they may have rapidly achieved a critical explosive state.

The outcomes of this thesis therefore deepen our knowledge of evolutionary trends in magma plumbing system dynamics, and highlight the importance of understanding the geochemical processes that can prime a volcano for eruption. Lastly, I emphasise the vital contribution petrology can make in current volcano monitoring efforts. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 42 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1325
magma plumbing, oxygen isotopes, thermobarometry, crustal assimilation, Katla, Merapi, Kelud, Toba, volcanic hazards
National Category
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
urn:nbn:se:uu:diva-267473 (URN)978-91-554-9424-7 (ISBN)
Public defence
2016-01-22, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Available from: 2015-12-17 Created: 2015-11-23 Last updated: 2016-01-13

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Deegan, FrancesTroll, ValentinGeiger, Harri
Geosciences, Multidisciplinary

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