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Spinel crystals in tephras preserve heating and cooling pathways during magma ascent and eruption at La Palma, Canary Islands

Samantha Tramontano 1,2,3, Marc-Antoine Longpré3,2, Matthew J. Pankhurst4,5, Franco Cortese2,3, Fátima Rodríguez4, Beverley Coldwell4,6, Alba Martín-Lorenzo4,6, Olivia Barbee7

  • Affiliations: 1Department of Earth and Planetary Sciences, American Museum of Natural History, New York, NY, USA; 2School of Earth and Environmental Sciences, Queens College, City University of New York, New York, NY, USA; 3Earth and Environmental Sciences, The Graduate Center, City University of New York, New York, NY, USA; 4Instituto Volcanológico de Canarias, San Cristóbal de La Laguna, Spain; 5Gaiaxiom, Copenhagen, Denmark; 6Instituto Tecnológico y de Energías Renovables, Granadilla de Abona, Spain; 7Xnovo Technology, Køge, Denmark 

  • Presentation type: Talk

  • Presentation time: Tuesday 11:00 - 11:15, Room R380

  • Programme No: 1.6.3

  • Theme 1 > Session 6

Abstract

Particles ejected from Strombolian jets can be glassy to microcrystalline in texture, can vary as particles recycle within jets, and preserve insight to the conditions of shallow magma ascent and eruption. We focus our study on the composition of spinel crystals (EPMA) in daily-constrained airfall samples from the 2021 Tajogaite eruption, La Palma, Canary Islands, with an aim to constrain conditions of magma ascent and jetting. Applying a Mg-in-magnetite thermometer [1], we observe a wider variation in crystallization temperatures of spinel rims as the eruption progresses. This variability could reflect more diverse fountaining dynamics that followed a major cone collapse in the first week of the eruption. Spinel crystals in glassy (primary juvenile) ash particles record the narrowest range in temperatures (942°C±23°C) and are dominantly unzoned. The lowest (875°C) and highest (976°C) temperatures are recorded in spinel crystals in microcrystalline (recycled juvenile) ash particles. We interpret reverse and normal chemical zones (8-20 µm) across single-crystal traverses to represent pathways of heating and cooling, respectively; however, deciphering where crystallization takes place is a challenge. Crystal growth can occur at depth, during ascent, or at the surface in the hot jets. We argue that the Mg-in-magnetite thermometer may be a useful petrologic tool for estimating temperature conditions beneath and within Strombolian jets and, with continued textural work, may yield important insight for how conduit and jet dynamics produce tephra particles of different morphologies and how these processes may vary over the duration of an eruption. [1] Canil and Lacourse (2020), Chemical Geology