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

Abstract

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.

Control of source fertility on the eruptive activity of Piton de la Fournaise volcano, La Réunion

“…The volume of mantle melt (V melt ) is derived from the volume of lava (V lava ) through three corrections. First, the dense rock equivalent volume (V DRE ) is inferred from: where ϕ is lava porosity, close to 50% on average for lava flows 46 . Then, the volume corrected for olivine fractionation and/or accumulation (V 12.5 ) is obtained by normalizing V DRE to primitive melt MgO content of 12.5 wt% 25 : where olivine MgO content is 43 wt% on average 22 .…”

Magma Propagation at Piton de la Fournaise From Joint Inversion of InSAR and GNSS

“…After a series of small summit eruptions and noneruptive intrusions in 2008-2009, the volcano remained quiet for 3.5 years. But from 2014 to September 2018, activity picked up, with 14 further eruptions, which alternated between north and south flanks location (Figure 1c; Coppola et al, 2017;Gurioli et al, 2018;Peltier et al, 2016Peltier et al, , 2018.…”

Textural, thermal, and topographic constraints on lava flow system structure: the December 2010 eruption of Piton de la Fournaise

“…In other flows, near-vent crystallinities of 50-70 vol% (Fig. 8) likely indicate that magma was extracted from a heterogeneous, stratified magma chamber, with the crystal-rich material from the base of the shallow reservoir being erupted last (Gurioli et al 2018). In comparison, the 2007 flow of Piton de la Fournaise (Rhéty et al 2017) has a near-vent crystallinity of 55 vol%, increasing to 75 vol% at the flow front due to microlite crystallization.…”