Spatio-temporal dynamics of the magmatic plumbing systems, towards an « early-warning clock ». Application to Dominica island (Lesser Antilles) and Kamchatka (Russia)

• Main Author: Ostorero, Léa
• Other Authors: Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris Cité, Georges Boudon, Hélène Balcone-Boissard
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2022
• Subjects: Lesser Antilles; Kamchatka; Volcanic eruptions; Magma dynamics; Timescales; Diffusion chronometry; Orthopyroxenes; Magnetites; Petites Antilles; Éruptions volcaniques; Dynamiques des magmas; Échelles de temps; Chronométrie de diffusion; Orthopyroxènes; Magnétites; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences
• Online Access: https://theses.hal.science/tel-04133642; https://theses.hal.science/tel-04133642/document; https://theses.hal.science/tel-04133642/file/vd_Ostorero_Lea.pdf

Volcanic eruptions are among the most devastating events on Earth. In a subduction context, eruptions generally involve differentiated magmas: after long repose times in magma reservoirs, basic magmas resulting from the partial melting of the mantle evolve towards differentiated compositions, thus richer in silica, more viscous and richer in volatile elements. These magmas can give various eruptive styles more or less explosive depending on different parameters such as the composition of the magma, the volume of magma involved, and the behavior of volatile elements during the ascent in the volcanic conduits. Estimating the time between changes in magma storage conditions within a magma reservoir and the onset of an eruption is one of the major challenges in volcanology. A direct observation of the magma storage system under the volcanoes is impossible but this timescale can be accessible thanks to the study of crystals brought to the surface by a past volcanic eruption. Indeed, like tree rings, which can provide information on past events, crystals growing within magma reservoirs feeding volcanoes record changes in magma storage conditions before an eruption. In many large-scale eruptions, it has been shown that magma injections or decompression events can occur in the reservoir and be recorded by the crystals as zonations (i.e., rims of different compositions than the crystal cores). With time, a homogenization of chemical compositions between zonations by diffusion of elements occurs (for example, the diffusion of iron and magnesium for orthopyroxenes or diffusion of titanium in magnetites). During an eruption, the diffusion is frozen by the rapid cooling of the emitted magmas and it is then possible to determine the time between the readjustments in the reservoir and the eruption. Magmatic reactivation timescales have been studied during this thesis for subduction zone volcanoes generating particularly dangerous arc volcanism, focusing on explosive eruptions from a volcano on the island of Dominica as well as ...