Mineralogical and geochemical features of the Allan Hills tephra, South Victoria Land: Implications for mid-Pleistocene volcanic activity in Antarctica

• Published in: Polar Science
• Main Authors: Borisova, Anastassia, Jochum, Klaus, Gouy, Sophie
• Other Authors: Geology Department, Moscow State University, Moscow 119992, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: [SDU]Sciences of the Universe [physics]; [SDE]Environmental Sciences; Allan Hills; Antarctic; Victoria Land; Antarc*; Antarctica; Polar Science
• Online Access: https://hal.science/hal-02995769; https://hal.science/hal-02995769/document; https://hal.science/hal-02995769/file/Allan%20Hills%20paper_revised_PS_2020_final%20revised_clear_to%20submit.pdf; https://doi.org/10.1016/j.polar.2020.100505

International audience More than 100 volcanoes have been discovered in Antarctica, however, the sources of many Antarctic tephras are not yet constrained. In this study, four tephra samples recovered from the environment of Site 27 on an area of blue ice at Allan Hills, South Victoria Land, provide information on magma and crustal sources for the tephra erupted in Antarctica. We report data on the chemistry of Antarctic tephra glasses and minerals analysed by electron microscopy, electron probe microanalysis and laser ablation inductively coupled plasma mass spec-trometry. The tephra amphibole chemistry indicates magma residence at ~1 GPa and ~1100 °C. Abundant Ca-Al-Si-rich minerals imply that the magma ascended from a reservoir at 29.4 +/- 2.7 km depth was affected by the assimilation of calc-silicate crust. The high Fe and Ti contents in the magmatic minerals and the trace element patterns of the glasses typical of a hydrothermally altered oceanic crust suggest that the Allan Hills tephra originated from a mantle plume-derived magma. The fragmented morphology of the glasses implies that the magmatic activity was associated with explosive eruptions during the mid-Pleistocene. The chemistry of the glasses and the presence of rh€ onite and Al-rich spinel minerals suggest that the magma might be genetically related to the currently active McMurdo volcanic group.