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dc.contributor.authorZernack, Anke V.
dc.contributor.authorPrice, Richard C.
dc.contributor.authorSmith, Ian E.M.
dc.contributor.authorCronin, Shane J.
dc.contributor.authorStewart, Robert B.
dc.date.accessioned2012-03-01T20:52:22Z
dc.date.available2012-03-01T20:52:22Z
dc.date.issued2011
dc.identifier.citationZernack, A.V., Price, R.C., Smith, I.E.M., Cronin, S.J. & Stewart, R.B. (2011). Temporal evolution of a high-k andesitic magmatic system: Taranaki Volcano, New Zealand. Journal of Petrology, 53(2), 325-363.en_NZ
dc.identifier.urihttps://hdl.handle.net/10289/6077
dc.description.abstractTaranaki (Mt. Egmont) in the western North Island of New Zealand is a high-K andesite volcano with an eruptive history extending over more than 200 kyr. In general, petrological research has concentrated on the post-10 ka record of the modern edifice. This study focuses on the earlier history, which is recorded in 11 major pre-7 ka debris avalanche deposits. Each of these formed as a result of a catastrophic collapse of the edifice of the time. The clast assemblages of these deposits provide insights into the chemical compositions of magmas erupted during the earlier stages of activity of the volcano and form the basis for a new chemo-stratigraphic analysis of the pre-10 ka volcanic succession. Sample suites from the studied debris avalanche deposits show a progressive enrichment in K₂O and large ion lithophile elements (LILE), reflecting a gradual evolution to high-K andesite. The early magmatic system (pre-100 ka) produced a wide range of compositions including relatively primitive basalts and basaltic andesites. These rocks contain phenocryst assemblages that indicate crystallization within the lower crust or mantle, including a broad range of clinopyroxene compositions, high-Al₂O₃ hornblende, olivine and phlogopite. A higher proportion of high-silica compositions in the younger sample suites and the appearance of late-stage, low-pressure mineral phases, such as high-TiO₂ hornblende, biotite and Fe-rich orthopyroxene, reflect a gradual shift to more evolved magmas with time. These new data are interpreted to reflect a multi-stage origin for Taranaki andesites. Parental magmas were generated within a lower crustal ‘hot zone’, which formed as a result of repeated intrusions of primitive melts into the lower crust. The geochemical and mineralogical evidence indicates that prior to 100 ka this zone was relatively thin and cold, so that primitive magmas were able to rise rapidly through the crust without significant interaction and modification. As the hot zone evolved, larger proportions of intruded and underplated mafic material were partially remelted, and interaction of these melts with fractionating mantle-derived magmas generated progressively more K- and LILE-enriched compositions. A complex and dispersed magma assembly and storage system developed in the upper crust where the hot-zone melts were further modified by fractional crystallization and magma mixing and mingling.en_NZ
dc.language.isoen
dc.publisherOxford University Pressen_NZ
dc.relation.urihttp://petrology.oxfordjournals.org/content/53/2/325.abstracten_NZ
dc.subjectTaranaki/Egmont Volcanoen_NZ
dc.subjecthigh-K andesiteen_NZ
dc.subjectmagmatic evolutionen_NZ
dc.subjectlower crustal hot zoneen_NZ
dc.subjectdebris avalanche depositsen_NZ
dc.titleTemporal evolution of a high-k andesitic magmatic system: Taranaki Volcano, New Zealanden_NZ
dc.typeJournal Articleen_NZ
dc.identifier.doi10.1093/petrology/egr064en_NZ
dc.relation.isPartOfJournal of Petrologyen_NZ
pubs.begin-page1en_NZ
pubs.elements-id36939
pubs.end-page39en_NZ
pubs.issue2en_NZ
pubs.volume_onlineen_NZ


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