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3D visualisation of nanolite aggregation in basaltic magmas using X-ray ptychography: Implications for magma rheology

Emily C. Bamber1, Fabio Arzilli2, Silvia Cipiccia3, Darren J. Batey4, Giuseppe La Spina5, Margherita Polacci6, Ali Gholinia7, Heath Bagshaw8, Danilo Di Genova1, Richard Brooker9, Daniele Giordano10, Pedro Valdivia11 and Mike R. Burton6

  • Affiliations:  1 Institute of Science, Technology and Sustainability for Ceramics (ISSMC), National Research Council (CNR), Faenza, Italy; 2 School of Science and Technology, Geology Division, University of Camerino, Camerino, Italy; 3 Department of Medical Physics and Biomedical Engineering, University College London, London, UK; 4 Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK; 5 Istituto Nazionale di Geofisica e Vulcanologia - Osservatorio Etneo, Sezione di Catania, Catania, Italy; 6 Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK; 7 Department of Materials, The University of Manchester, Manchester, UK; 8 School of Engineering, The University of Liverpool, Liverpool, UK; 9 School of Earth Sciences, University of Bristol, Bristol, UK; 10 Department of Earth Sciences, University of Turin, Turin, Italy; 11 Bayerisches Geoinstitut, University of Bayreuth, Bayreuth, Germany 

  • Presentation type: Poster

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

  • Poster Board Number: 214

  • Programme No: 3.2.37

  • Theme 3 > Session 2

Abstract

Nanoscale crystals, or 'nanolites', are becoming increasingly recognised in natural volcanic clasts and experimental run-products, spanning a wide range of magma compositions and explosivity. Nanolite crystallisation can increase magma viscosity, through the rheological impact of the nanoparticle suspension, by increasing melt polymerisation, inducing chemical and structural changes in the residual melt and facilitating heterogeneous bubble nucleation. Furthermore, due to their large surface area, nanolites may be prone to agglomeration, increasing their impact on magma rheology. However, their morphology, spatial distribution and interaction have yet to be investigated using a three-dimensional (3D) approach.  Here we present an innovative 3D reconstruction and visualisation of nanolites in basaltic volcanic scoriae, acquired using X-ray ptychography, an X-ray microscopy technique with nanoscale resolution. Our 3D images illustrate that Ti-magnetite nanolites agglomerate in basaltic magmas. Their agglomeration entraps interstitial melt, increasing their effective volume and their impact on magma viscosity. We support our 3D nanoscale observations with images acquired using SEM and STEM, utilising multi-scale imaging methods to visualise nanolite crystallisation in basaltic magmas. We use our data in viscosity models to evaluate their impact on magma rheology, finding that the rheological changes associated with their crystallisation may promote magma fragmentation during ascent. Our results not only provide insight into the rheology of nanoparticle suspensions, but also the driving mechanisms of highly explosive, Plinian activity at basaltic volcanic systems.