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dc.contributor.authorMattsson, Tobias
dc.contributor.authorBurchardt, Steffi
dc.contributor.authorAlmqvist, Bjarne S.G.
dc.contributor.authorRonchin, Erika
dc.identifier.citationMattsson , T , Burchardt , S , Almqvist , B S G & Ronchin , E 2018 , ' Syn-emplacement fracturing in the sandfell laccolith, eastern iceland—implications for rhyolite intrusion growth and volcanic hazards ' , Frontiers in Earth Science , vol. 6 , 5 .
dc.identifier.otherPURE: 271111714
dc.identifier.otherPURE UUID: 3c6451a7-a4fe-413f-a013-ee3fb93a6b64
dc.identifier.otherScopus: 85043603158
dc.identifier.otherORCID: /0000-0003-0717-4014/work/83890081
dc.descriptionField work was funded by Uddeholms travel stipend (Värmlands nation, Uppsala, Sweden), Otterborgs travel stipend and the Swedish Royal Academy of Science (KVA). The research was funded by the Swedish Research Council (VR) grant 2015-03931_VR. ER is funded by the Center of Natural Hazards and Disaster Science (CNDS).en
dc.description.abstractFelsic magma commonly pools within shallow mushroom-shaped magmatic intrusions, so-called laccoliths or cryptodomes, which can cause both explosive eruptions and collapse of the volcanic edifice. Deformation during laccolith emplacement is primarily considered to occur in the host rock. However, shallowly emplaced laccoliths (cryptodomes) show extensive internal deformation. While deformation of magma in volcanic conduits is an important process for regulating eruptive behavior, the effects of magma deformation on intrusion emplacement remain largely unexplored. In this study, we investigate the emplacement of the 0.57km3 rhyolitic Sandfell laccolith, Iceland, which formed at a depth of 500m in a single intrusive event. By combining field measurements, 3D modeling, anisotropy of magnetic susceptibility (AMS), microstructural analysis, and FEM modeling we examine deformation in the magma to constrain its influence on intrusion emplacement. Concentric flow bands and S-C fabrics reveal contact-parallel magma flow during the initial stages of laccolith inflation. The magma flow fabric is overprinted by strain-localization bands (SLBs) and more than one third of the volume of the Sandfell laccolith displays concentric intensely fractured layers. A dominantly oblate magmatic fabric in the fractured areas and conjugate geometry of SLBs, and fractures in the fracture layers demonstrate that the magma was deformed by intrusive stresses. This implies that a large volume of magma became viscously stalled and was unable to flow during intrusion. Fine-grained groundmass and vesicle-poor rock adjacent to the fracture layers point to that the interaction between the SLBs and the flow bands at sub-solidus state caused the brittle-failure and triggered decompression degassing and crystallization, which led to rapid viscosity increase in the magma. The extent of syn-emplacement fracturing in the Sandfell laccolith further shows that strain-induced degassing limited the amount of eruptible magma by essentially solidifying the rim of the magma body. Our observations indicate that syn-emplacement changes in rheology, and the associated fracturing of intruding magma not only occur in volcanic conduits, but also play a major role in the emplacement of viscous magma intrusions in the upper kilometer of the crust.
dc.relation.ispartofFrontiers in Earth Scienceen
dc.rightsCopyright © 2018 Mattsson, Burchardt, Almqvist and Ronchin. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.en
dc.subjectIntrusion emplacementen
dc.subjectMagma degassingen
dc.subjectMagma flowen
dc.subjectStrain localizationen
dc.subjectVolcanic hazardsen
dc.subjectGE Environmental Sciencesen
dc.subjectEarth and Planetary Sciences(all)en
dc.titleSyn-emplacement fracturing in the sandfell laccolith, eastern iceland—implications for rhyolite intrusion growth and volcanic hazardsen
dc.typeJournal articleen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews.School of Earth & Environmental Sciencesen
dc.description.statusPeer revieweden

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