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Crystal Forensics of Historical Lava Flows from Mt Ngauruhoe

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dc.contributor.advisor Baker, Joel
dc.contributor.author Barton, Sophie Jan
dc.date.accessioned 2012-05-24T04:17:53Z
dc.date.accessioned 2022-11-01T21:35:05Z
dc.date.available 2012-05-24T04:17:53Z
dc.date.available 2022-11-01T21:35:05Z
dc.date.copyright 2011
dc.date.issued 2011
dc.identifier.uri https://ir.wgtn.ac.nz/handle/123456789/27974
dc.description.abstract Mt Ngauruhoe is a 900 m high andesitic cone constructed over the last 2500 yr, and is the youngest cone of the Tongariro Massif. It was previously one of the most continuously active volcanoes in New Zealand, with ash eruptions having occurred every few years since written records for the volcano began in 1839. However, it has now been more than 30 yr since the last eruption. Eruptions in 1870, 1949, 1954 and 1974-1975 were accompanied by lava and block-and-ash flows. Detailed sampling of these historical lava and block-and-ash flows was conducted, including sampling from seven different lava flows erupted over the period June-September 1954 to investigate changes in magma geochemistry and crystal populations over short timescales, and to enable observed changes to be related back to known eruption dates. Mineral major and trace element chemistry highlights the importance of mixing between distinct basaltic and dacitic melts to generate the basaltic andesite whole rock compositions erupted. The basaltic end member can be identified from the presence of olivine crystals with Mg# 75-87, clinopyroxene cores with Mg# 82-92, and plagioclase cores of An80-90. The dacitic melt is identified by SiO2-rich clinopyroxene melt inclusions, clinopyroxene zoning with Mg# 68-76 and plagioclase rims of An60-70. Textural evidence from complex mineral zoning and large variability in the widths of reaction rims on olivine crystals suggests that mafic recharge of the more evolved system is frequent, and modelling of Fe-Mg inter-diffusion applied to the outermost rims of the clinopyroxene crystal population indicates that such recharge events have occurred weeks to months or even shorter prior to each of the historical eruptions, and thus likely trigger the eruptions. en_NZ
dc.format pdf en_NZ
dc.language en_NZ
dc.language.iso en_NZ
dc.publisher Te Herenga Waka—Victoria University of Wellington en_NZ
dc.rights Access is restricted to staff and students only until May 2014. For information please contact the library. en_NZ
dc.subject Volcanology en_NZ
dc.subject Vulcanology en_NZ
dc.subject Taupo en_NZ
dc.subject Tongariro en_NZ
dc.subject Petrology en_NZ
dc.title Crystal Forensics of Historical Lava Flows from Mt Ngauruhoe en_NZ
dc.type Text en_NZ
vuwschema.contributor.unit School of Geography, Environment and Earth Sciences en_NZ
vuwschema.subject.marsden 260103 Vulcanology en_NZ
vuwschema.subject.marsden 260102 Igneous and Metamorphic Petrology en_NZ
vuwschema.subject.marsden 260399 Geochemistry en_NZ
vuwschema.type.vuw Awarded Research Masters Thesis en_NZ
thesis.degree.discipline Geology en_NZ
thesis.degree.grantor Te Herenga Waka—Victoria University of Wellington en_NZ
thesis.degree.level Masters en_NZ
thesis.degree.name Master of Science en_NZ

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