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Chemical and textural analysis of tube forming lavas at Vesuvius (Italy) by EMPA and 3D X-ray micro-CT

Thomas Lemaire1 , Daniele Morgavi1, Fabio Arzilli2, Sonia Calvari3, Emily Charlotte Bamber4, Giuseppe La Spina3, Ciro Cucciniello1, Marko Prasek5, Lucia Mancini6, Paola Petrosino1

  • Affiliations: 1Department of Earth, Environment and Resource Sciences (DiSTAR), University Federico II, Naples, Italy 2School of Science and Technology, Geology division, University of Camerino, Camerino, Italy 3Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo -- Sezione di Catania, Catania, Italy 4Institute of Science, Technology and Sustainability for Ceramics (ISSMC), National Research Council (CNR), Faenza, Italy 5Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Trieste, Italy 6Department of Materials, Slovenian National Building and Civil Engineering Institute (ZAG), Ljubljana, Slovenia 

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 207

  • Programme No: 3.6.11

  • Theme 3 > Session 6

Abstract

Lava flow emplacement is directly affected by effusion rate, viscosity and topography. The transport of lava within the flows is also enhanced by the formation of lava channels or lava tubes. Indeed, a tube-fed lava flow can emplace over longer distances, due to the insulation of the molten lava by the roof preventing cooling by atmospheric heat exchange. The formation of lava tubes in a lava flow depends on numerous parameters such as eruptive rates, pre-eruptive topography, geochemical composition, vesicles and crystals content, and ultimately, viscosity. Thus, it is crucial to understand the mechanisms governing lava tube formation to improve hazard assessment and crisis response. Here, we examine a lava flow field formed during the 1858-1861 eruption at Vesuvius within which a series of lava tubes were formed. We sampled the 1858 lava flow field and one of its lava tubes, conducted Electron Microprobe Analysis (EMPA) to measure crystal and glass compositions, and performed a 3D morpho-textural characterization using phase-contrast synchrotron X-ray computed microtomography (µ-CT) to retrieve the 3D structure of our samples and characterize the crystal phases. We found variations in Crystal Size Distribution (CSD) within the microlitic matrixes that reflect the cooling conditions of the lavas during emplacement. We also observed variations in the volume fraction of the phases between the samples. These variations in crystallinity within the flow field and lava tube give insights into the conditions of emplacement of the lava flow field and the formation of lava tubes by inflation.