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Magmatic differentiation processes at Merapi Volcano: inclusion petrology and oxygen isotopes
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
Dept. of Geological Science, University of Cape Town, Rondebosch 7701, South Africa.
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2013 (English)In: Journal of Volcanology and Geothermal Research, ISSN 0377-0273, Vol. 261, no SI, 38-49 p.Article in journal (Refereed) Published
Abstract [en]

Indonesian volcano Merapi is one of the most hazardous volcanoes on the planet and is characterised by periods of active dome growth and intermittent explosive events. Merapi currently degasses continuously through high temperature fumaroles and erupts basaltic-andesite dome lavas and associated block-and-ash-flows that carry a large range of magmatic, coarsely crystalline plutonic, and meta-sedimentary inclusions. These inclusions are useful in order to evaluate magmatic processes that act within Merapi's plumbing system, and to help an assessment of which phenomena could trigger explosive eruptions. With the aid of petrological, textural, and oxygen isotope analysis we record a range of processes during crustal magma storage and transport, including mafic recharge, magma mixing, crystal fractionation, and country rock assimilation. Notably, abundant calc-silicate inclusions (true xenoliths) and elevated δ18O values in feldspar phenocrysts from 1994, 1998, 2006, and 2010 Merapi lavas suggest addition of limestone and calc-silicate materials to the Merapi magmas. Together with high δ13C values in fumarole gas, crustal additions to mantle and slab-derived magma and volatile sources are likely a steady state process at Merapi. This late crustal input could well represent an eruption trigger due to sudden over-pressurisation of the shallowest parts of the magma storage system independently of magmatic recharge and crystal fractionation. Limited seismic precursors may be associated with this type of eruption trigger, offering a potential explanation for the sometimes erratic behaviour of Merapi during volcanic crises.

Place, publisher, year, edition, pages
Elsevier, 2013. Vol. 261, no SI, 38-49 p.
Keyword [en]
Merapi Volcano; Magmatic and crustal inclusions; Oxygen isotopes; Crustal contamination
National Category
Earth and Related Environmental Sciences Geochemistry
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
URN: urn:nbn:se:uu:diva-188483DOI: 10.1016/j.jvolgeores.2012.11.001ISI: 000324154400004OAI: oai:DiVA.org:uu-188483DiVA: diva2:577895
Available from: 2012-12-17 Created: 2012-12-17 Last updated: 2013-12-18Bibliographically approved
In thesis
1. Magma-Crust Interaction at Subduction Zone Volcanoes
Open this publication in new window or tab >>Magma-Crust Interaction at Subduction Zone Volcanoes
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The focus of this work is magma-crust interaction processes and associated crustal volatile release in subduction zone volcanoes, drawing on rock, mineral, and gas geochemistry as well as experimental petrology. Understanding the multitude of differentiation processes that modify an original magma during ascent to the surface is vital to unravel the contributions of the various sources that contribute to the final magmas erupted at volcanoes. In particular, magma-crust interaction (MCI) processes have been investigated at a variety of scales, from a local scale in the Vesuvius, Merapi, and Kelut studies, to a regional scale, in the Java to Bali segment of the Sunda Arc.

 The role of crustal influences is still not well constrained in subduction systems, particulary in terms of the compositional impact of direct magma crust interplay. To address this shortcoming, we studied marble and calc-silicate (skarn) xenoliths, and used high resolution short timescale experimental petrology at Vesuvius volcano. The marbles and calc-silicates help to identify different mechanisms of magma-carbonate and magma-xenolith interaction, and the subsequent effects of volatile release on potential eruptive behaviour, while sequential short-duration experiments simulate the actual processes of carbonate assimilation employing natural materials and controlled magmatic conditions. The experiments highlight the efficiency of carbonate assimilation and associated carbonate-derived CO2 liberated over short timescales.

The findings at Merapi and Kelut demonstrate a complex magmatic plumbing system underneath these volcanoes with magma residing at different depths, spanning from the mantle-crust boundary to the upper crust. The erupted products and volcanic gas emissions enable us to shed light on MCI-processes and associated volatile release in these systems. The knowledge gained from studying individual volcanoes (e.g., Merapi and Kelut) is then tested on a regional scale and applied to the entire Java and Bali arc segment. An attempt is presented to distinguish the extent of source versus crustal influences and establish a quantitative model of late stage crustal influence in this arc segment.

This thesis therefore hopes to contribute to our knowledge of magma genesis and magma-crust interaction (MCI) processes that likely operate in subduction zone systems worldwide.


Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 40 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1037
magma-crust interaction, stable isotopes (O-C), radiogenic isotopes (Sr-Nd-Pb), calc-silicate xenoliths, HP-HT experimental petrology, crustal volatiles, Vesuvius, Merapi, Kelut, the Sunda arc
National Category
Geology Geochemistry
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
urn:nbn:se:uu:diva-198085 (URN)978-91-554-8648-8 (ISBN)
Public defence
2013-05-24, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 14:00 (English)
Available from: 2013-05-03 Created: 2013-04-08 Last updated: 2013-08-30

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Troll, ValentinDeegan, FrancesJolis, Ester Muños
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