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Remobilized MIs record storage conditions at Lopevi volcano (Vanei Vollohulu, Vanuatu, SW Pacific)

Kristen R. Lewis1 , Alex Nichols1, C. Ian Schipper2, Darren Gravley1, Shane Cronin3, Takeshi Kuritani4, Akiko Matsumoto4, Georg F. Zellmer5

  • Affiliations: 1School of Earth and Environment, University of Canterbury, Christchurch, New Zealand; 2School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington, New Zealand; 3School of Environment, The University of Auckland, Auckland, New Zealand; 4Department of Earth and Planetary Sciences, University of Hokkaido, Sapporo, Japan; 5Institute of Geosciences, University of Bonn, Bonn, Germany 

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 246

  • Programme No: 1.1.32

  • Theme 1 > Session 1

Abstract

Lopevi is an active basaltic-andesitic stratovolcano in the Vanuatu arc.  Eruptions over the last 100 years have been characterized by near-constant degassing with intermittent explosive sub-Plinian tephra falls and effusive summit/flank lava flows.  Geochemical heterogeneity between historic eruptive episodes (pre-1960, 1960-1980's, 1998-) has been attributed to decompression vs. flux melting in the mantle as well as variable assimilation fractional crystallization (AFC) occurring during transport and storage.  These processes are thought to control magma dynamics and eruptive frequency at Lopevi; however, to date, research has focused on whole rocks/lavas. Melt inclusions (MIs) allow magmatic conditions at the time of entrapment within the host crystal to be determined and thus preserve information that may be lost in whole rocks due to later fractionation, mixing, and/or degassing.  Investigating volatile, major, and trace elements in MIs will better constrain source, storage, and eruption processes at Lopevi.  Here, we present the first analyses of olivine-, plagioclase-, and clinopyroxene-hosted MIs from tephras produced during the 1960-68 and 2002-3 eruptions.  Textural evidence from accompanying lavas indicates that the two eruptive periods remobilized large phenocrysts from storage zones.  Basaltic to andesitic MIs are partly degassed with H2O 1-2.5 wt.%; CO2 (glass) ≤ 480 ppm; S 100-850 ppm; Cl 960-2,350 ppm; and F 800-1,290 ppm.  MI saturation depths of ~1-4 km for the 1960-68 eruption and 0.5-2.7 km for the 2002-3 eruption inferred from volatile solubility modelling suggest that the MIs were remobilized from distinct storage zones during each eruption.