Integrating field, textural and geochemical monitoring to track eruption triggers and dynamics: a case-study from Piton de la Fournaise

Abstract. The 2014 eruption at Piton de La Fournaise (PdF), la Reunion, which occurred after 41 months of quiescence, began with surprisingly little precursory activity, and was one of the smallest so far observed at PdF in terms of duration (less than 2 days) and volume (less than 0.4 Mm3). The pyroclastic material was composed of spiny-opaque, spiny-iridescent, and fluidal scoria along with golden pumice. Density analyses performed on 200 lapilli reveal that the spiny-opaque clasts are the densest (1600 kg/m3) and richest in crystals (54 vol%), and the golden pumices are the lightest (400 kg/m3) and poorest in crystals (14 vol%). The connectivity data indicate that the fluidal and golden (Hawaiian-like) clasts have more isolated vesicles (up to 40 %) than the spiny (Strombolian-like) clasts (0–5 %). These textural variations are linked to primary pre-eruptive magma storage conditions. The golden and fluidal fragments track the hotter portion of the melt, in contrast to the spiny fragments which mirror the cooler portion of the shallow reservoir. Progressive tapping of these distinct portions leads to a decrease in the explosive intensity from early fountaining to Strombolian activity. The geochemical results confirm the absence of new hot input of magma and confirm the involvement of a single, shallow, differentiated magma source, possibly related to residual magma from the November 2009 eruption. We found that the eruption was triggered by water exsolution, favoured by the shallow depth of the reservoir, rather than cooling and chemical evolution of the stored magma.

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Integrating field, textural, and geochemical monitoring to track eruption triggers and dynamics: a case study from Piton de la Fournaise

Solid Earth ◽

10.5194/se-9-431-2018 ◽

2018 ◽

Vol 9 (2) ◽

pp. 431-455 ◽

Cited By ~ 11

Author(s):

Lucia Gurioli ◽

Andrea Di Muro ◽

Ivan Vlastélic ◽

Séverine Moune ◽

Simon Thivet ◽

...

Keyword(s):

Storage System ◽

Storage Conditions ◽

Magma Ascent ◽

Magma Source ◽

Piton De La Fournaise ◽

Melt Separation ◽

2014 Eruption ◽

Volatile Exsolution ◽

Precursory Activity

Abstract. The 2014 eruption at Piton de la Fournaise (PdF), La Réunion, which occurred after 41 months of quiescence, began with surprisingly little precursory activity and was one of the smallest so far observed at PdF in terms of duration (less than 2 days) and volume (less than 0.4  ×  106 m3). The pyroclastic material was composed of golden basaltic pumice along with fluidal, spiny iridescent and spiny opaque basaltic scoria. Density analyses performed on 200 lapilli reveal that while the spiny opaque clasts are the densest (1600 kg m−3) and most crystalline (55 vol. %), the golden pumices are the least dense (400 kg m−3) and crystalline (8 vol. %). The connectivity data indicate that the fluidal and golden (Hawaiian-like) clasts have more isolated vesicles (up to 40 vol. %) than the spiny (Strombolian-like) clasts (0–5 vol. %). These textural variations are linked to primary pre-eruptive magma storage conditions. The golden and fluidal fragments track the hotter portion of the melt, in contrast to the spiny fragments and lava that mirror the cooler portion of the shallow reservoir. Exponential decay of the magma ascent and output rates through time revealed depressurization of the source during which a stratified storage system was progressively tapped. Increasing syn-eruptive degassing and melt–gas decoupling led to a decrease in the explosive intensity from early fountaining to Strombolian activity. The geochemical results confirm the absence of new input of hot magma into the 2014 reservoir and confirm the emission of a single shallow, differentiated magma source, possibly related to residual magma from the November 2009 eruption. Fast volatile exsolution and crystal–melt separation (second boiling) were triggered by deep pre-eruptive magma transfer and stress field change. Our study highlights the possibility that shallow magma pockets can be quickly reactivated by deep processes without mass or energy (heat) transfer and produce hazardous eruptions with only short-term elusive precursors.

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Evolution in magma storage conditions beneath Kick-'em-Jenny and Kick-'em-Jack submarine volcanoes, Lesser Antilles arc

Journal of Volcanology and Geothermal Research ◽

10.1016/j.jvolgeores.2019.01.023 ◽

2019 ◽

Vol 373 ◽

pp. 1-22 ◽

Cited By ~ 1

Author(s):

Michal Camejo-Harry ◽

Elena Melekhova ◽

Jon Blundy ◽

Richard Robertson

Keyword(s):

Storage Conditions ◽

Lesser Antilles ◽

Magma Storage ◽

Magma Storage Conditions ◽

Lesser Antilles Arc

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Dominica: transcrustal magmatic system and eruptive halogen budgets

10.5194/egusphere-egu2020-13591 ◽

2020 ◽

Author(s):

Thiebaut d'Augustin ◽

Hélène Balcone-Boissard ◽

Georges Boudon ◽

Caroline Martel ◽

Etienne Deloule ◽

...

Keyword(s):

Melt Inclusions ◽

Storage Conditions ◽

Explosive Eruptions ◽

Magma Storage ◽

Equilibrium Data ◽

Order Of Magnitude ◽

First Time ◽

Magma Storage Conditions ◽

Degassing Budget

Dominica island experienced the largest explosive eruptions (ignimbrites) of the Lesser Antilles arc. The recent revised chronostratigraphy of the Morne Trois Pitons &#8211; Micotrin eruptive activity evidenced a series of plinian eruptions that occurred between 18 ka and 9 ka BP. Here we focus on these recent eruptions in order to determine the magma storage conditions at depth and volatile degassing budget. Volatile concentrations (H2O, CO2) in melt inclusions indicate storage conditions of 200 MPa (~6-8 km deep) and 860-880&#176;C in agreement with experimental constraints from phase-equilibrium data. The magmas were thus stored shallower than those involved during the ignimbritic eruptions (~16 km deep). Magma composition and halogen ratios suggest a common magma origin for all eruptions of Morne Trois Pitons Micotrin volcano in the last 60 kyrs. In addition, for the first time, a complete degassing budget including H2O, CO2, SO2, F, Cl, and Br has been established for all these explosive eruptions. The estimation of their eruptive fluxes towards the atmosphere supports the potential important role of halogen elements in the modification of atmosphere chemistry. Br degassing budget was the same order of magnitude as S whereas F and Cl budgets were 1 and 2 orders of magnitude higher than these two species.

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