title: Eruption Dynamics and Hydrological Implications of Basaltic Volcanic Centres at Lake Taupo

authors: Matheson, Maree Annette

subjects: basalt

abstract: The Taupo Volcanic Centre (TVC) is a major rhyolite centre within the Taupo Volcanic Zone, yet a small volume of the centre is comprised of monogenetic basalt volcanoes.  Four TVC basalts that lie north of Lake Taupo have been examined in this study: the tuff deposits of Acacia Bay, Kaiapo and Kinloch, and the scoria cone complex of Punatekahi.  Inferred ages of the basalts range from ~ 200 ky (Acacia Bay tuff) to lt; 9.5 ky (Kinloch tuff).  The particular aim of this study is to determine the volcanological and hydrological controls responsible for the nature of the basaltic deposits through: field description; data on grain size, vesicularity, componentry and clast morphology (including SEM); petrography; and XRF geochemistry of six representative samples.  
The basalts share a similar mineralogy (plagioclase gt; olivine, augite) and geochemistry (low-K volcanic arc magmas), but can be clearly distinguished by their physical characteristics.  The Punatekahi basalt deposit is comprised of thick beds of scoria lapilli, and welded agglutinate, formed by magmatic strombolian and hawaiian eruptions.  The Acacia Bay, Kaiapo and Kinloch deposits are all tuff deposits that have a significant base surge component resulting from phreatomagmatic surtseyan and taalian eruptions.  The Punatekahi scoria deposit has higher vesicularity values and lower lithic abundance than the other three basalt centres, reflecting the difference between magmatic and phreatomagmatic eruption mechanisms, respectively.
All of the four basalt deposits are located in areas that have at one time been covered by Lake Taupo (or its ancestor Lake Huka), and the phreatomagmatic deposits of Acacia Bay, Kaiapo and Kinloch all have evidence of partial subaqueous deposition, suggesting that a lake was present at those sites at the time of eruption.  Explosive interaction of magma with groundwater occurred during all of the four eruptions.  For the eruptions at Acacia Bay, Kaiapo and Punatekahi, Rangatira Ignimbrite is inferred as a likely aquifer source, and either the rhyolite dome or a fault is posited as the water source for the Kinloch basalt eruption. 
The Kinloch tuff deposit is younger than the other TVC deposits by at least ~ 100 ky.  The presence of this much younger basalt volcano indicates that, despite the dominance of rhyolitic eruptions, basalt volcanism has an ongoing presence in the TVC, and a future basalt eruption, with unique hazards, are a real possibility.

text: Eruption Dynamics and Hydrological Implications of Basaltic Volcanic Centres at Lake Taupo The Taupo Volcanic Centre (TVC) is a major rhyolite centre within the Taupo Volcanic Zone, yet a small volume of the centre is comprised of monogenetic basalt volcanoes.  Four TVC basalts that lie north of Lake Taupo have been examined in this study: the tuff deposits of Acacia Bay, Kaiapo and Kinloch, and the scoria cone complex of Punatekahi.  Inferred ages of the basalts range from ~ 200 ky (Acacia Bay tuff) to lt; 9.5 ky (Kinloch tuff).  The particular aim of this study is to determine the volcanological and hydrological controls responsible for the nature of the basaltic deposits through: field description; data on grain size, vesicularity, componentry and clast morphology (including SEM); petrography; and XRF geochemistry of six representative samples.  
The basalts share a similar mineralogy (plagioclase gt; olivine, augite) and geochemistry (low-K volcanic arc magmas), but can be clearly distinguished by their physical characteristics.  The Punatekahi basalt deposit is comprised of thick beds of scoria lapilli, and welded agglutinate, formed by magmatic strombolian and hawaiian eruptions.  The Acacia Bay, Kaiapo and Kinloch deposits are all tuff deposits that have a significant base surge component resulting from phreatomagmatic surtseyan and taalian eruptions.  The Punatekahi scoria deposit has higher vesicularity values and lower lithic abundance than the other three basalt centres, reflecting the difference between magmatic and phreatomagmatic eruption mechanisms, respectively.
All of the four basalt deposits are located in areas that have at one time been covered by Lake Taupo (or its ancestor Lake Huka), and the phreatomagmatic deposits of Acacia Bay, Kaiapo and Kinloch all have evidence of partial subaqueous deposition, suggesting that a lake was present at those sites at the time of eruption.  Explosive interaction of magma with groundwater occurred during all of the four eruptions.  For the eruptions at Acacia Bay, Kaiapo and Punatekahi, Rangatira Ignimbrite is inferred as a likely aquifer source, and either the rhyolite dome or a fault is posited as the water source for the Kinloch basalt eruption. 
The Kinloch tuff deposit is younger than the other TVC deposits by at least ~ 100 ky.  The presence of this much younger basalt volcano indicates that, despite the dominance of rhyolitic eruptions, basalt volcanism has an ongoing presence in the TVC, and a future basalt eruption, with unique hazards, are a real possibility.

year: 2010

title: Effect of manganese on grain refinement of Mg–Al based alloys

authors: Cao, Peng

subjects: Magnesium alloys

abstract: Manganese is a grain refiner for high purity Mg–3%Al, Mg–6%Al, Mg–9%Al, and commercial AZ31 (Mg–3%Al–1%Zn) alloys when introduced in the form of an Al–60%Mn master alloy splatter but the use of pure Mn flakes and ALTAB™ Mn75 tablets shows no grain refinement. Long time holding of the melt at 730 °C leads to an increase in grain size. The mechanism is attributed to the presence of an ε-AlMn phase (hexagonal close-packed) in the master alloy splatter.

text: Effect of manganese on grain refinement of Mg–Al based alloys Manganese is a grain refiner for high purity Mg–3%Al, Mg–6%Al, Mg–9%Al, and commercial AZ31 (Mg–3%Al–1%Zn) alloys when introduced in the form of an Al–60%Mn master alloy splatter but the use of pure Mn flakes and ALTAB™ Mn75 tablets shows no grain refinement. Long time holding of the melt at 730 °C leads to an increase in grain size. The mechanism is attributed to the presence of an ε-AlMn phase (hexagonal close-packed) in the master alloy splatter.

year: 2006-06

title: Māori data governance model

authors: Kukutai, Tahu

abstract: This report describes the Māori Data Governance Model that has been designed by Māori data experts for use across the Aotearoa New Zealand public service. Māori data is a taonga that requires culturally grounded models of protection and care. The Model provides guidance for the system-wide governance of Māori data, consistent with the Government’s responsibilities under te Tiriti o Waitangi. The Model is intended to assist all agencies to undertake Māori data governance in a way that is values-led, centred on Māori needs and priorities, and informed by research. This is important because existing government data processes and practices are failing to meet Māori informational needs.

The Vision, Tuia te korowai o Hine-Raraunga – Data for self-determination, enables iwi, hapū and Māori organisations, businesses and communities to pursue their own goals for cultural, social, economic and environmental wellbeing. Eight Data Pou or pillars define critical areas of data governance and specify the actions that should be undertaken to realise six desired outcomes. The Model does not cover every element of data governance; instead, it focuses on key priorities and actions, against which agencies can assess their level of data maturity. The Model explicitly recognises the need for changes to system leadership, policies and legal settings so that Māori can exercise authority over Māori data to reduce unethical data use and strengthen outcomes for individuals, whānau and communities. The report also identifies the need for strategic investment in a Mana Motuhake data system that sits outside of the public sector to ensure iwi and hapū sovereignty over iwi and hapū data.

text: Māori data governance model This report describes the Māori Data Governance Model that has been designed by Māori data experts for use across the Aotearoa New Zealand public service. Māori data is a taonga that requires culturally grounded models of protection and care. The Model provides guidance for the system-wide governance of Māori data, consistent with the Government’s responsibilities under te Tiriti o Waitangi. The Model is intended to assist all agencies to undertake Māori data governance in a way that is values-led, centred on Māori needs and priorities, and informed by research. This is important because existing government data processes and practices are failing to meet Māori informational needs.

The Vision, Tuia te korowai o Hine-Raraunga – Data for self-determination, enables iwi, hapū and Māori organisations, businesses and communities to pursue their own goals for cultural, social, economic and environmental wellbeing. Eight Data Pou or pillars define critical areas of data governance and specify the actions that should be undertaken to realise six desired outcomes. The Model does not cover every element of data governance; instead, it focuses on key priorities and actions, against which agencies can assess their level of data maturity. The Model explicitly recognises the need for changes to system leadership, policies and legal settings so that Māori can exercise authority over Māori data to reduce unethical data use and strengthen outcomes for individuals, whānau and communities. The report also identifies the need for strategic investment in a Mana Motuhake data system that sits outside of the public sector to ensure iwi and hapū sovereignty over iwi and hapū data.

year: 2023