High temperature in-situ study of radiative properties of basaltic dry magmas

• Main Authors: Biren, Jonas, del Campo, Leire, Cosson, Lionel, Li, Hao, Slodczyk, Aneta, Andújar, Joan
• Other Authors: Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Magma - UMR7327, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Conditions Extrêmes et Matériaux : Haute Température et Irradiation (CEMHTI), Université d'Orléans (UO)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2020
• Subjects: Emissivity; temperature; vibrational spectroscopy; remote sensing; basalt; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Holuhraun; Iceland
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-02569974; https://doi.org/10.5194/egusphere-egu2020-546

International audience Temperature is a key parameter controlling the evolution of lava flows. The hazardous behavior of eruptions prevents direct measurements of hot magmatic bodies. Hence, the temperature of magma is mostly retrieved by using non-contact methods (ground-based or satellite-based thermal cameras) based on measuring the infrared (IR) emission flux (E) of the body [1]. These well-established techniques are however subjected to important errors, ±100°C, related to surrounding environment [2], large temperature gradients of cooling lavas [3], constant changes in composition and texture and especially an apparent lack of radiative emission properties during the lava emplacement. Despite that reducing the uncertainties of environmental and thermal gradients when measuring E is ultimately challenging, our study aimed to minimizing the uncertainty in one of the critical hitherto poorly known oversimplified parameters [3,4,5] namely spectral emissivity. Therefore, we performed optical measurements at relevant magmatic temperatures (up to 1200°C) of representative basaltic dry magmas (MORB, alkaline, calc-alkaline). Emissivity has been systematically determined over a wide spectral (400-15000 cm-1) and thermal range (from room up to 1200°C) using a non-contact in situ IR emissivity apparatus [6]. SEM, EMPA and Raman spectroscopy techniques were also used in order to characterize and understand the complex radiative behavior of these natural magmatic compositions. Emissivity varies accordingly with temperature and wavenumber but our results also show that small changes in bulk-rock composition produce drastic changes in emissivity at given T, with iron content and its oxidation state being the main agents controlling this parameter. Appropriate emissivity values will then help to refine current field or (space) satellite IR monitoring data (i.e. Holuhraun 2014-2015, Iceland; [3]) and to implement the thermo-rheological models of lava flows [7] as to support hazard assessment and risk mitigation.