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Segmentation of zoned plagioclase crystals from Plinian eruptions of Mont Pelée: Implications for the characterisation of source magmas and understanding of eruption dynamics

Tom Sheldrake1 , Aurélie Germa2, Oliver Higgins3, Hélène Balcone-Boissard4, Sebastian Flöter1, Saskia Erdmann5, Adrien Duvernois4

  • Affiliations:  1Department of Earth Sciences, University of Geneva, Switzerland; 2School of Geosciences, University of South Florida, Tampa, U.S.A; 3School of Earth and Environmental Sciences, University of St Andrews, UK; 4Institut des Sciences de la Terre de Paris, ISTeP, Sorbonne Université, CY Cergy Paris Université, CNRS INSU,  F-75005 Paris; 5Institut des sciences de la Terre d\'Orléans (ISTO). Orleans, France 

  • Presentation type: Poster

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

  • Poster Board Number: 205

  • Programme No: 1.9.12

  • Theme 1 > Session 9

Abstract

The eruptive history of Mont Pelée is interspersed by multiple Plinian events that have been associated with widespread ash and pumice fallout deposits across the north of Martinique. These events represent some of the most explosive eruptions produced by Mont Pelée. Here, we present chemically calibrated maps of plagioclase crystals from six different Plinian events. Major element maps are calibrated using Electron Microprobe analyses of either complete thin sections or epoxy-embedded single crystals. Segmentation of plagioclase crystals identifies distinct zoning groups (spatially constrained regions of similar An#) that are found in multiple crystals and different eruptions. These zones range in composition with median An# between 53 to 88. By quantifying the complexity of the zoning, we can characterise a so-called "genetic profile" for different events. No event contains all zoning groups and, in general, profiles can be distinguished based on whether they contain high An# groups or not. Additionally, if the lowest An# group is present in a sample, it is the most dominant of all zoning groups. By characterising these genetic profiles, we can begin to investigate the links between the intensity and evolution of each eruption, and the regions from where magma was periodically stored and/or erupted. Additionally, the technique allows us to target crystals for more focused trace-element mapping and verify the field-derived correlation of volcanic units.