IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

3W_2G-P2

Date/Time: July 23 Poster

Volatile and light lithophile trace element geochemistry of the 2010 eruption of Merapi
volcano revealed by melt inclusions
Katie Preece1 , Ralf Gertisser2 , Kim Berlo3 , Jenni Barclay1 , Richard Herd1
1

School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK, 2 School ofPhysical and Geographical Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK, 3 Departmentof Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK
E-mail: K.Preece@uea.ac.uk

The 2010 eruption of Merapi (VEI 4) was the volcano’s largest since 1872. In contrast to recent prolonged
and effusive dome-forming eruptions at Merapi, such as the previous eruption in 2006, the 2010 eruption began
explosively, before a new dome was rapidly emplaced between 30 October and 4 November 2010. On 5 November,this new dome was destroyed by explosions, generating pyroclastic density currents (PDCs), predominantly
consisting of dark-coloured, glass-rich, dense blocks of basaltic andesite dome lava, which travelled ~16 km fromthe summit, immediately followed by PDCs characterised by scoriaceous and pumiceous clasts.
In this paper, we present volatile and light lithophile element data of clinopyroxene-hosted melt inclusions fromsamples of the dense dome lava, scoria and pumice from the PDCs generated during the peak of the 2010eruption. SIMS analysis of volatiles (H2 O and CO2 ) and light lithophile elements (Li, B, Be) are augmented byelectron microprobe analysis of major elements and volatiles (Cl, S) in the same melt inclusions and groundmass
glass.
The melt inclusions are dacitic to rhyolitic in composition (63.3-71.8 wt.% SiO2 ) and have variable contents ofH2 O and CO2 , ranging between 0.1-3.8 wt.% and up to ~2500 ppm, respectively. The highest H2 O contents
are preserved in melt inclusions from scoriaceous and pumiceous clasts. Some melt inclusions from the pumicepreserve evidence of relatively high CO2 contents at medium (~2 wt.%) H2 O contents. Chlorine contents range
from 2000-5000 ppm and S is present in quantities up to 500 ppm in the melt inclusions, with the groundmass glassof pumice characterised by higher volatile concentrations than the groundmass of the dense dome. Light lithophileelement analyses show a moderate range in concentration in the melt inclusions of Li (15-68 ppm) and B (25-84ppm) and uniform Be concentrations (1-2 ppm).
Our data suggest that a simple model of equilibrium decompression-driven degassing cannot explain the H2 O andCO2 concentrations in the analysed melt inclusions. Instead, melt inclusion data record a complex pre-eruptive
storage and ascent history of the 2010 magma, highlighting open-system processes, including entrapment of melt
at multiple levels within the crust, enrichment of CO2 in some inclusions, and the influx and exsolution of Li-richvapours at shallow depths. Despite the more explosive nature of the 2010 eruption, melt inclusions reveal a similar
pre-eruptive volatile content to the 2006 eruption, suggesting that degassing behaviour rather than higher initial
volatiles contents, contributed to the paroxysmal 2010 eruption.

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