Magmatic differentiation processes at Merapi Volcano: inclusion petrology and oxygen isotopes

Troll, Valentin R.; Deegan, Frances M.; Jolis, Ester M.; Gertisser, Ralf; Harris, Chris; Chadwick, Jane P.; Schwarzkopf, Lothar M.; Borisova, Anastassia Y.; Bindeman, Ilya N.; Sumarti, Sri; Preece, Katie

Abstract

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.

Citation

Troll, V. R., Deegan, F. M., Jolis, E. M., Gertisser, R., Harris, C., Chadwick, J. P., …Preece, K. (2013). Magmatic differentiation processes at Merapi Volcano: inclusion petrology and oxygen isotopes. Journal of Volcanology and Geothermal Research, 261, 38-49. https://doi.org/10.1016/j.jvolgeores.2012.11.001

• Journal Article Type: Article
• Acceptance Date: Nov 2, 2012
• Online Publication Date: Nov 9, 2012
• Publication Date: 2013-07
• Deposit Date: May 30, 2023
• Journal: Journal of Volcanology and Geothermal Research
• Print ISSN: 0377-0273
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 261
• Pages: 38-49
• DOI: https://doi.org/10.1016/j.jvolgeores.2012.11.001
• Keywords: Geochemistry and Petrology; Geophysics
• Additional Information: This article is maintained by: Elsevier; Article Title: Magmatic differentiation processes at Merapi Volcano: inclusion petrology and oxygen isotopes; Journal Title: Journal of Volcanology and Geothermal Research; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.jvolgeores.2012.11.001; Content Type: article; Copyright: Copyright © 2012 Elsevier B.V. Published by Elsevier B.V. All rights reserved.