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Timescales of magmatic processes driving the 2017-2018 Manaro Voui (Ambae, Vanuatu) eruptive crisis: an olivine perspective

Eva Delhaye1,2, Hélène Balcone-Boissard1, Etienne Médard2, Pierre-Jean Gauthier2, Philipson Bani2, Vanuatu Meteorological and Geohazards Department3

  • Affiliations: 1Institut des Sciences de la Terre de Paris, Sorbonne Université, Paris, France ; 2Laboratoire Magmas et Volcans, Université Clermont Auvergne, Clermont-Ferrand, France ; 3Vanuatu Meteorological and Geohazards Department (VMGD), Vanuatu

  • Presentation type: Poster

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

  • Poster Board Number: 65

  • Programme No: 1.2.10

  • Theme 1 > Session 2

Abstract

In 2017-2018, after centuries of quiescence, Manaro Voui, an active volcano on the island of Ambae (Vanuatu arc), experienced a major eruption that forced the evacuation of its 11,000 inhabitants twice. This recent crisis underscores the critical gaps in our understanding of the volcano, despite the substantial hazards it presents. Our study aims to better constrain the pre-eruptive processes and their timescales. Olivine crystals within magma act as natural time capsules, recording variations in magma conditions during growth. By combining systematic crystal analysis with multi-element diffusion chronometry (Fe-Mg, Li, H), the heterogeneous composition of olivine crystals is used to identify eruption triggers and their associated timescales. Systematic chemical analysis of olivines from tephra collected from each eruptive phase enables the characterisation of magmatic environments. The dynamics of the plumbing system are assessed through Fe-Mg diffusion, revealing that the system reactivated less than ten years before the eruption, with the last injection occurring less than one month before the initial activity, marked by phreatic explosions. Li diffusion modelling confirms the timing of the final injection and highlights shorter processes such as degassing. Additionally, H diffusion profiles indicate rapid ascent rates at the eruption's onset, estimated below 6 m s-1. By integrating diffusion modelling of multiple elements in olivines, we unravelled a detailed timeline of magmatic processes leading up to the eruption. This approach brings new constraints on pre-eruptive processes operating at Manaro Voui, providing a foundation for identifying precursory signals crucial for mitigating future impacts on the local population.