title: The anatomy of an andesite volcano: a time-stratigraphic study of andesite petrogenesis and crustal evolution at Ruapehu Volcano, New Zealand

authors: Price, Richard C.

subjects: andesite

abstract: Ruapehu, New Zealand’s largest active andesite volcano, is located at the southern tip of the Taupo Volcanic Zone (TVZ), the main locus of subduction-related volcanism in the North Island. Geophysical data indicate that crustal thickness increases from <25 km within the TVZ to 40 km beneath Ruapehu. The volcano is built on a basement of Mesozoic meta-greywacke, and geophysical evidence together with xenoliths contained in lavas indicates that this is underlain by oceanic, meta-igneous lower crust. The present-day Ruapehu edifice has been constructed by a series of eruptive events that produced a succession of lava flow-dominated stratigraphic units. In order from oldest to youngest, these are the Te Herenga (250–180 ka), Wahianoa (160–115 ka), Mangawhero (55–45 ka and 20–30 ka), and Whakapapa (15–2 ka) Formations. The dominant rock types are plagioclase- and pyroxene-phyric basaltic andesite and andesite. Dacite also occurs but only one basalt flow has been identified. There have been progressive changes in the minor and trace element chemistry and isotopic composition of Ruapehu eruptive rocks over time. In comparison with rocks from younger formations, Te Herenga eruptive rocks have lower K₂O abundances and a relatively restricted range in major and trace element and Nd–Sr isotopic composition. Post-Te Herenga andesites and dacites define a Sr–Nd isotopic array that overlaps with the field for TVZ rhyolites and basalts, but Te Herenga Formation lavas and the Ruapehu basalt have higher ¹⁴³Nd/¹⁴⁴Nd ratios. The isotopic, and major and trace element composition of Te Herenga andesite can be replicated by models involving mixing of an intra-oceanic andesite with a crustal component derived from a meta-igneous composition. Post-Te Herenga andesites show considerable variation in major and trace element and Sr and Nd isotopic compositions (⁸⁷Sr/⁸⁶Sr ranges from 0•7049 to 0•7060 and ¹⁴³Nd/¹⁴⁴Nd from 0•51264 to 0•51282). The range of compositions can be modeled by assimilation–fractional crystallization (AFC) involving meta-greywacke as the assimilant, closed-system fractionation, or by mixing of intra-oceanic andesite or basalt and a meta-greywacke crustal composition. Plagioclase and pyroxene compositions vary over wide ranges within single rocks and few of these have compositions consistent with equilibration with a melt having the composition of either the host-rock or groundmass. The ⁸⁷Sr/⁸⁶Sr compositions of plagioclase also vary significantly within single whole-rock samples. Glass inclusions and groundmasses of andesitic rocks all have dacitic or rhyolitic major and trace element compositions. The application of various mineral geothermometers and geobarometers indicates pre-eruption temperatures between 950 and 1190°C and pressures ranging from 1 to 0•2 GPa. These pressure estimates are consistent with those obtained from xenolith mineral assemblages and geophysical information. Plagioclase hygrometry and the paucity of amphibole are indications that melts were relatively dry (< 4 wt % H₂O). Magmas represented by Ruapehu andesites were dacitic or rhyolitic melts carrying complex crystal and lithic cargoes derived from the mantle and at least two crustal sources. They have evolved through a complex interplay between assimilation, crystal fractionation, crustal anatexis and magma mixing. Parental magmas were sourced in both the mantle and crust, but erupted compositions very strongly reflect modification by intracrustal processes. Geochemical variation in systematically sampled lava flow sequences is consistent with random tapping of a complex plumbing system in which magma has been stored on varying time scales within a plexus of dispersed reservoirs. Each magma batch is likely to have had a unique history with different sized magma storages evolving on varying time scales with a specific combination of AFC and mixing processes.

text: The anatomy of an andesite volcano: a time-stratigraphic study of andesite petrogenesis and crustal evolution at Ruapehu Volcano, New Zealand Ruapehu, New Zealand’s largest active andesite volcano, is located at the southern tip of the Taupo Volcanic Zone (TVZ), the main locus of subduction-related volcanism in the North Island. Geophysical data indicate that crustal thickness increases from <25 km within the TVZ to 40 km beneath Ruapehu. The volcano is built on a basement of Mesozoic meta-greywacke, and geophysical evidence together with xenoliths contained in lavas indicates that this is underlain by oceanic, meta-igneous lower crust. The present-day Ruapehu edifice has been constructed by a series of eruptive events that produced a succession of lava flow-dominated stratigraphic units. In order from oldest to youngest, these are the Te Herenga (250–180 ka), Wahianoa (160–115 ka), Mangawhero (55–45 ka and 20–30 ka), and Whakapapa (15–2 ka) Formations. The dominant rock types are plagioclase- and pyroxene-phyric basaltic andesite and andesite. Dacite also occurs but only one basalt flow has been identified. There have been progressive changes in the minor and trace element chemistry and isotopic composition of Ruapehu eruptive rocks over time. In comparison with rocks from younger formations, Te Herenga eruptive rocks have lower K₂O abundances and a relatively restricted range in major and trace element and Nd–Sr isotopic composition. Post-Te Herenga andesites and dacites define a Sr–Nd isotopic array that overlaps with the field for TVZ rhyolites and basalts, but Te Herenga Formation lavas and the Ruapehu basalt have higher ¹⁴³Nd/¹⁴⁴Nd ratios. The isotopic, and major and trace element composition of Te Herenga andesite can be replicated by models involving mixing of an intra-oceanic andesite with a crustal component derived from a meta-igneous composition. Post-Te Herenga andesites show considerable variation in major and trace element and Sr and Nd isotopic compositions (⁸⁷Sr/⁸⁶Sr ranges from 0•7049 to 0•7060 and ¹⁴³Nd/¹⁴⁴Nd from 0•51264 to 0•51282). The range of compositions can be modeled by assimilation–fractional crystallization (AFC) involving meta-greywacke as the assimilant, closed-system fractionation, or by mixing of intra-oceanic andesite or basalt and a meta-greywacke crustal composition. Plagioclase and pyroxene compositions vary over wide ranges within single rocks and few of these have compositions consistent with equilibration with a melt having the composition of either the host-rock or groundmass. The ⁸⁷Sr/⁸⁶Sr compositions of plagioclase also vary significantly within single whole-rock samples. Glass inclusions and groundmasses of andesitic rocks all have dacitic or rhyolitic major and trace element compositions. The application of various mineral geothermometers and geobarometers indicates pre-eruption temperatures between 950 and 1190°C and pressures ranging from 1 to 0•2 GPa. These pressure estimates are consistent with those obtained from xenolith mineral assemblages and geophysical information. Plagioclase hygrometry and the paucity of amphibole are indications that melts were relatively dry (< 4 wt % H₂O). Magmas represented by Ruapehu andesites were dacitic or rhyolitic melts carrying complex crystal and lithic cargoes derived from the mantle and at least two crustal sources. They have evolved through a complex interplay between assimilation, crystal fractionation, crustal anatexis and magma mixing. Parental magmas were sourced in both the mantle and crust, but erupted compositions very strongly reflect modification by intracrustal processes. Geochemical variation in systematically sampled lava flow sequences is consistent with random tapping of a complex plumbing system in which magma has been stored on varying time scales within a plexus of dispersed reservoirs. Each magma batch is likely to have had a unique history with different sized magma storages evolving on varying time scales with a specific combination of AFC and mixing processes.

year: 2012

title: Enabling seamless market-orientated supply chains

authors: Childerhouse, Paul

subjects: vision-principles-toolkit model

abstract: A decade after the publication of the concept of smooth material flow via four fundamental principles related to the work of Jay Forrester and John Burbidge (FORRIDGE) the influence of this work on academe and industry is discussed. We show that by extension of their principles via a three-level model which includes the vision and the toolkit, substantial contributions have been made towards new management theory. The associated 12 simplicity rules and uncertainly circle concepts have been exploited within the structured framework provided by the quick scan audit methodology. This generates value stream classification ranging from baseline to exemplar, and a design procedure aimed at material flow best practice. A detailed case study demonstrates the improved industrial performance achievable by this means.

text: Enabling seamless market-orientated supply chains A decade after the publication of the concept of smooth material flow via four fundamental principles related to the work of Jay Forrester and John Burbidge (FORRIDGE) the influence of this work on academe and industry is discussed. We show that by extension of their principles via a three-level model which includes the vision and the toolkit, substantial contributions have been made towards new management theory. The associated 12 simplicity rules and uncertainly circle concepts have been exploited within the structured framework provided by the quick scan audit methodology. This generates value stream classification ranging from baseline to exemplar, and a design procedure aimed at material flow best practice. A detailed case study demonstrates the improved industrial performance achievable by this means.

year: 2006

title: Colouring in the White Spaces: Reclaiming Cultural Identity in Whitestream Schools

authors: Milne, Beverley Ann

subjects: Maori education

abstract: If we look at a child’s colouring book, before it has any colour added to it, we think of the page as blank.  It’s actually not blank, it’s white.  That white background is just “there” and we don’t think much about it.  Not only is the background uniformly white, the lines are already in place and they dictate where the colour is allowed to go.  When children are young, they don’t care where they put the colours, but as they get older they colour in more and more cautiously. They learn about the place of colour and the importance of staying within the pre-determined boundaries and expectations. 

This thesis argues that this is the setting for our mainstream, or what I have called, whitestream New Zealand schools — that white background is the norm.   When we talk about multiculturalism and diversity what we are really referring to is the colour of the children, or their difference from that white norm, and how they don’t fit perfectly inside our lines.  If the colour of the space doesn’t change schools are still in the business of assimilation, relegating non-white children to the margins, no matter how many school reform initiatives, new curricula, strategic plans, or mandated standards we implement.  What the schools in this study have tried to do is change the colour of the space – so that the space fits the children and they don’t have to constantly adjust to fit in.  

New Zealand’s education system has been largely silent on the topic of whiteness and the Eurocentric nature of our schooling policy and practice. However, when I talk to senior Māori and Pasifika ‘warrior-scholars” in Te Whānau o Tupuranga and Clover Park Middle School about “white spaces” they have encountered in their schooling experience they can identify them all too easily.  “White spaces,” they explain, are anything you accept as “normal” for Māori – when it’s really not,  any situation that prevents, or works against you “being Māori” or who you are, and that requires you to “be” someone else and leave your beliefs behind. White spaces are spaces that allow you to require less of yourself and that reinforce stereotypes and negative ideas about Māori.  Most telling of all was the comment from a Māori student that goes straight to the root of the problem, “White spaces are everywhere,” she said, “even in your head.”

This thesis describes the 25 year journey of two schools and their community’s determination to resist and reject alienating school environments in favour of a relevant culturally-located, bilingual learning model based in a secure cultural identity, stable positive relationships, and aroha (authentic caring and love).  While the research design is a case study, in terms of western, “white space” academic tradition, it is also a story in terms of kaupapa Māori and critical race methodology. More importantly, it is a counter-story that chronicles the efforts of these two schools to step outside education’s “white spaces” to create new space.  This counter-story is juxtaposed against pervasive, deficit-driven whitestream explanations of “achievement gaps” and the “long tail” of Māori and Pasifika “under-achievement” in New Zealand schools.  In the process of this research the focus shifted from how could Māori and Pasifika learners develop secure cultural identities in mainstream schools, to examining what barriers exist in schools that prevent this from happening already?  As these issues became clear the language of the thesis shifted accordingly; “developing” a cultural identity was reframed as a reclamation of educational sovereignty — the absolute right to “be Māori” or “be Pasifika” in school — and “mainstream” schooling became better understood as the “whitestream.” 

The study hopes to contribute to the journey other schools might take to identify and name their own white spaces, and to make learning equitable for indigenous and minoritised learners.

text: Colouring in the White Spaces: Reclaiming Cultural Identity in Whitestream Schools If we look at a child’s colouring book, before it has any colour added to it, we think of the page as blank.  It’s actually not blank, it’s white.  That white background is just “there” and we don’t think much about it.  Not only is the background uniformly white, the lines are already in place and they dictate where the colour is allowed to go.  When children are young, they don’t care where they put the colours, but as they get older they colour in more and more cautiously. They learn about the place of colour and the importance of staying within the pre-determined boundaries and expectations. 

This thesis argues that this is the setting for our mainstream, or what I have called, whitestream New Zealand schools — that white background is the norm.   When we talk about multiculturalism and diversity what we are really referring to is the colour of the children, or their difference from that white norm, and how they don’t fit perfectly inside our lines.  If the colour of the space doesn’t change schools are still in the business of assimilation, relegating non-white children to the margins, no matter how many school reform initiatives, new curricula, strategic plans, or mandated standards we implement.  What the schools in this study have tried to do is change the colour of the space – so that the space fits the children and they don’t have to constantly adjust to fit in.  

New Zealand’s education system has been largely silent on the topic of whiteness and the Eurocentric nature of our schooling policy and practice. However, when I talk to senior Māori and Pasifika ‘warrior-scholars” in Te Whānau o Tupuranga and Clover Park Middle School about “white spaces” they have encountered in their schooling experience they can identify them all too easily.  “White spaces,” they explain, are anything you accept as “normal” for Māori – when it’s really not,  any situation that prevents, or works against you “being Māori” or who you are, and that requires you to “be” someone else and leave your beliefs behind. White spaces are spaces that allow you to require less of yourself and that reinforce stereotypes and negative ideas about Māori.  Most telling of all was the comment from a Māori student that goes straight to the root of the problem, “White spaces are everywhere,” she said, “even in your head.”

This thesis describes the 25 year journey of two schools and their community’s determination to resist and reject alienating school environments in favour of a relevant culturally-located, bilingual learning model based in a secure cultural identity, stable positive relationships, and aroha (authentic caring and love).  While the research design is a case study, in terms of western, “white space” academic tradition, it is also a story in terms of kaupapa Māori and critical race methodology. More importantly, it is a counter-story that chronicles the efforts of these two schools to step outside education’s “white spaces” to create new space.  This counter-story is juxtaposed against pervasive, deficit-driven whitestream explanations of “achievement gaps” and the “long tail” of Māori and Pasifika “under-achievement” in New Zealand schools.  In the process of this research the focus shifted from how could Māori and Pasifika learners develop secure cultural identities in mainstream schools, to examining what barriers exist in schools that prevent this from happening already?  As these issues became clear the language of the thesis shifted accordingly; “developing” a cultural identity was reframed as a reclamation of educational sovereignty — the absolute right to “be Māori” or “be Pasifika” in school — and “mainstream” schooling became better understood as the “whitestream.” 

The study hopes to contribute to the journey other schools might take to identify and name their own white spaces, and to make learning equitable for indigenous and minoritised learners.

year: 2013