Geochemistry and groundmass crystallinity controls on lava dome stability at Mount Taranaki, New Zealand

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dc.contributor.advisor Rowe, M en
dc.contributor.advisor Cronin, S en Zorn, Edgar en 2017-05-31T21:29:57Z en 2017 en
dc.identifier.uri en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract The study of lava domes and their properties is inherently important as their collapses pose a significant hazard to infrastructure, human lives and the environment. Mount Taranaki on the west coast of the North Island of New Zealand provides an excellent case study as a large part of the summit lava dome is currently exposed due to a partial collapse. Here, a detailed investigation into the groundmass crystallinity and chemical composition of the Taranaki lava dome is described, with dome samples taken from the current summit dome and several older BAFs. Rock properties are compared to the compressive and tensile strength in deformation experiments, simulating low temperature and low confining pressure conditions. Other parameters such as porosities and densities were also investigated. Porosity is determined to be the main control on rock strength and mode of failure. The groundmass crystallinity does show a relation to rock strength, but a direct control on rock strength cannot be proven as it is linked to a coupling of groundmass crystallinity to porosity. The composition of the rocks did not show any significant impact of the rock strength or any other physical parameters. The results imply that the crystallisation of the groundmass significantly impacts both porosity and density of the dome rocks depending on the resultant groundmass crystal content. Higher crystal content results in less pores, reflecting a slowly undercooled magma experiencing rheological stiffening deeper within the conduit under higher pressure conditions. This is linked to a slower magma ascent rate and results in a lava dome with higher rock strength. On the other hand, a less crystallised rock is more porous and represents magma with a faster ascent rate, resulting in stronger undercooling and solidification under lower pressures, presumably close to the surface. These rocks develop low groundmass crystallinity with high porosities and lower rock strength. The exception to this are low rock strength coulees, which show high groundmass crystallinity with higher and likely shear induced porosities. This implies, that the stability of the dome might shift significantly due to varying ascent rates and the developing rock strength. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof Masters Thesis - University of Auckland en
dc.relation.isreferencedby UoA99264921810902091 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
dc.rights.uri en
dc.rights.uri en
dc.title Geochemistry and groundmass crystallinity controls on lava dome stability at Mount Taranaki, New Zealand en
dc.type Thesis en Earth Sciences en The University of Auckland en Masters en
dc.rights.holder Copyright: The author en
pubs.elements-id 628002 en
pubs.record-created-at-source-date 2017-06-01 en

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