Multi-stage growth of the trachytic lava dome of the Puy de Dôme (Chaîne des Puys, France). Field, geomorphological and petro-geochemical evidence

• Published in: Journal of volcanology and geothermal research 2020-05, Vol.396, p.106749, Article 106749
• Main Authors: Deniel, C., Boivin, P., Miallier, D., Gerbe, M.C.
• Format: Article
• Language: English
• Subjects: Earth Sciences; French Massif Central; Geochemistry; Multi-stage growth; Petro-geochemical evidence; Petrography; Puy de Dôme volcano; Sciences of the Universe; Trachytic lava dome; Volcanology; Zoned magma reservoir
• ISSN: 0377-0273; 1872-6097
• DOI: 10.1016/j.jvolgeores.2019.106749

Understanding lava dome eruptions is a major concern in volcanology regarding the assessment of associated hazards. This question is usually addressed through the study of active calc-alkaline domes, however, alkaline domes remaining poorly known. The Puy de Dôme is the most prominent volcano of the Chaîne des Puys Quaternary intraplate volcanic field in the French Massif Central. It is a complex trachytic lava dome ca. 11 ka old. Field investigations, geomorphological and petro-geochemical studies were performed to understand the magmatic system of this dome and reconstruct its volcanic evolution. The different lava facies were fully characterised and their relationships with the volcano building stages have been established. A new four-step evolution is proposed for the growth of this edifice. Mineralogical and geochemical variations document magmatic differentiation with self-mixing and minor crustal contamination in a zoned reservoir within the upper crust. Magma mixing and crustal contamination through fluids interactions during magma ascent and the involvement of fumarolic activity throughout the edifice building are also documented. Further, this work highlights the specific features of the Puy de Dôme compared to calc-alkaline domes: lack of lava flows and almost complete magma degassing during ascent, resulting in the lack of significant explosive activity until the last eruption step. •An alkaline lava dome ca. 11 ka old with two lava facies and three pyroclastic units•Differentiation, self-mixing and minor crustal contamination in a zoned reservoir•Magmatic fluids and magma conduit processes, fractures and fumarolic activity•A four-step eruption: cryptodome/cpx-trachyte dome/bi-trachyte dome/explosive event•Almost complete magma degassing during ascent and lack of lava flow