Elaine Smid - Academia.edu (original) (raw)

Papers by Elaine Smid

Presentation by University of Auckland PhD candidate, Elaine Smid

Programme for the 14th Annual DEVORA Research Forum, held on Wednesday, 27 October 2021.

Each year, the DEtermining VOlcanic Risk in Auckland (DEVORA) research programme hosts a research... more Each year, the DEtermining VOlcanic Risk in Auckland (DEVORA) research programme hosts a research forum to present new scientific findings and connect researchers and stakeholders. These are the publicly available presentations from the 2020 DEVORA Forum. Please note that all of the slide decks have been provided by the individual researchers and uploaded without any changes. Each researcher is responsible for their own slides.Please reach out directly to the researcher(s) if you have questions about on comments on their presentations. If no contact information is included, please feel free to reach out to the contact below.

New Zealand Journal of Geology and Geophysics, 2020

Auckland Volcanic Field (AVF) is a basaltic intraplate volcanic field in North Island, New Zealan... more Auckland Volcanic Field (AVF) is a basaltic intraplate volcanic field in North Island, New Zealand, upon which >1.6 million people live. Seismic velocity tomography and geochemistry suggest a primary mantle source region at a depth of 70-90 km. Geochemical analysis indicates a range of magma compositions, and that melts ascend with little crustal interaction. Eruptions generally began with a phreatomagmatic phase forming maar and tuff rings with tephra fall, base surges, and ballistic projectiles as the main hazards. Subsequent magmatic phases formed scoria cones, and sometimes produced lava flows. Ages of 47 of the 53 volcanic centres reveal that the AVF first erupted ∼193 ka, and last erupted ∼500 yrs. BP. These geochronological constraints indicate repose periods ≤0.1-13 kyr, which have decreased since ∼60 ka. From known geological and exposure information, and using an interdisciplinary approach, eight future eruption scenarios have been developed for planning processes. Outstanding questions for the AVF concern the cause of mantle melting, the structure of the underlying lithosphere, magma ascent rates, controls on repose periods and eruptive volumes. Answering these questions may improve our understanding of warning periods, monitoring strategies, spatiotemporal risk profiles, and socioeconomic impacts of volcanism on New Zealand's largest city.

Journal of Volcanology and Geothermal Research, 2017

Abstract The Auckland Volcanic Field (AVF), which last erupted ca. 550 years ago, is a late Quate... more Abstract The Auckland Volcanic Field (AVF), which last erupted ca. 550 years ago, is a late Quaternary monogenetic basaltic volcanic field (ca. 500 km 2 ) in the northern North Island of New Zealand. Prior to this study only 12 out of the 53 identified eruptive centres of the AVF had been reliably dated. Careful sample preparation and 40 Ar/ 39 Ar analysis has increased the number of well-dated centres in the AVF to 35. The high precision of the results is attributed to selection of fresh, non-vesicular, non-glassy samples from lava flow interiors. Sample selection was coupled with separation techniques that targeted only the groundmass of samples with 10 μm wide, coupled with ten-increment furnace step-heating of large quantities (up to 200 mg) of material. The overall AVF age data indicate an onset at 193.2 ± 2.8 ka, an apparent six-eruption flare-up from 30 to 34 ka, and a ≤ 10 kyr hiatus between the latest and second-to-latest eruptions. Such non-uniformity shows that averaging the number of eruptions over the life-span of the AVF to yield a mean eruption rate is overly simplistic. Together with large variations in eruption volumes, and the large sizes and unusual chemistry within the latest eruptions (Rangitoto 1 and Rangitoto 2), our results illuminate a complex episodic eruption history. In particular, the rate of volcanism in AVF has increased since 60 ka, suggesting that the field is still in its infancy. Multiple centres with unusual paleomagnetic inclination and declination orientations are confirmed to fit into a number of geomagnetic excursions, with five identified in the Mono Lake, two within the Laschamp, one within the post-Blake or Blake, and two possibly within the Hilina Pali.

New Zealand Journal of Geology and Geophysics, 2011

Bulletin of Volcanology, 2013

ABSTRACT The Auckland Volcanic Field (AVF) is a dormant monogenetic basaltic field located in Auc... more ABSTRACT The Auckland Volcanic Field (AVF) is a dormant monogenetic basaltic field located in Auckland, New Zealand. Though soil gas CO2 fluxes are routinely used to monitor volcanic regions, there have been no published studies of soil CO2 flux or soil gas CO2 concentrations in the AVF to date or many other monogenetic fields worldwide. We measured soil gas CO2 fluxes and soil gas CO2 concentrations in 2010 and 2012 in varying settings, seasons, and times of day to establish a baseline soil CO2 flux and to determine the major sources of and controlling influences on Auckland's soil CO2 flux. Soil CO2 flux measurements varied from 0 to 203 g m−2 day−1, with an average of 27.1 g m−2 day−1. Higher fluxes were attributed to varying land use properties (e.g., landfill). Using a graphical statistical approach, two populations of CO2 fluxes were identified. Isotope analyses of δ13CO2 confirmed that the source of CO2 in the AVF is biogenic with no volcanic component. These data may be used to assist with eruption forecasting in the event of precursory activity in the AVF, and highlight the importance of knowing land use history when assessing soil gas CO2 fluxes in urban environments.

Chemical Geology, 2020

Abstract The Auckland Volcanic Field (AVF) is one of the most intensively studied monogenetic bas... more Abstract The Auckland Volcanic Field (AVF) is one of the most intensively studied monogenetic basalt fields in the world yet its origin remains enigmatic. Magmatism in the AVF occurred from ~193 ka to 500 years bp. The trace element and isotopic diversity of AVF basalts require “small-scale” compositional heterogeneity in the underlying mantle that is comparable in volume to, or slightly larger than, the scale of individual eruptions in the AVF. Olivine from tephra and lava, representing the range of AVF compositions, was crushed and analysed for 3He/4He, and He and CO2 concentrations in an attempt to further characterize and explain the significance of the AVF “end-members”. AVF basalts show a negative covariation between the amount of CO2 released by crushing of olivine and the whole rock concentrations of highly incompatible trace elements, such as Ba, Rb, Nb, Zr, Ti and K. In contrast, the amount of He released by crushing shows no simple relations with the same incompatible elements or their ratios. This leads to a significant variation in CO2/3He ratios (9.4 × 107–3.5 × 109) that may relate to differences in magma ascent dynamics, as well as to different magma sources. The measured CO2/He ratios may have been influenced by varying amounts of CO2 diffusion into vapour bubbles within melt inclusions that depend on melt composition and magma ascent rate. However, petrographically there is no evidence for systematic differences in the size or quantity of vapour bubbles in olivine-hosted melt inclusions. 3He/4He ratios in 14 AVF samples studied here show a narrow range from 6.57 to 7.26 RA (mean of 7.10 ± 0.26). This may imply a dominance of the mantle helium budget by small-scale heterogeneities. Alternatively, the 3He/4He results suggest that the tectonic and magmatic history of the mantle beneath the AVF has effectively hybridized the 3He/4He ratio to a larger extent than for highly incompatible trace element ratios and Pb-Nd-Sr isotopes. The value of ~7 RA for the mantle source of AVF basalts, in light of other evidence, suggests that there is a relatively homogeneous He isotope composition for the Zealandia-Antarctic mantle domain.

Presentation by University of Auckland PhD candidate, Elaine Smid

Programme for the 14th Annual DEVORA Research Forum, held on Wednesday, 27 October 2021.

Each year, the DEtermining VOlcanic Risk in Auckland (DEVORA) research programme hosts a research... more Each year, the DEtermining VOlcanic Risk in Auckland (DEVORA) research programme hosts a research forum to present new scientific findings and connect researchers and stakeholders. These are the publicly available presentations from the 2020 DEVORA Forum. Please note that all of the slide decks have been provided by the individual researchers and uploaded without any changes. Each researcher is responsible for their own slides.Please reach out directly to the researcher(s) if you have questions about on comments on their presentations. If no contact information is included, please feel free to reach out to the contact below.

New Zealand Journal of Geology and Geophysics, 2020

Auckland Volcanic Field (AVF) is a basaltic intraplate volcanic field in North Island, New Zealan... more Auckland Volcanic Field (AVF) is a basaltic intraplate volcanic field in North Island, New Zealand, upon which >1.6 million people live. Seismic velocity tomography and geochemistry suggest a primary mantle source region at a depth of 70-90 km. Geochemical analysis indicates a range of magma compositions, and that melts ascend with little crustal interaction. Eruptions generally began with a phreatomagmatic phase forming maar and tuff rings with tephra fall, base surges, and ballistic projectiles as the main hazards. Subsequent magmatic phases formed scoria cones, and sometimes produced lava flows. Ages of 47 of the 53 volcanic centres reveal that the AVF first erupted ∼193 ka, and last erupted ∼500 yrs. BP. These geochronological constraints indicate repose periods ≤0.1-13 kyr, which have decreased since ∼60 ka. From known geological and exposure information, and using an interdisciplinary approach, eight future eruption scenarios have been developed for planning processes. Outstanding questions for the AVF concern the cause of mantle melting, the structure of the underlying lithosphere, magma ascent rates, controls on repose periods and eruptive volumes. Answering these questions may improve our understanding of warning periods, monitoring strategies, spatiotemporal risk profiles, and socioeconomic impacts of volcanism on New Zealand's largest city.

Journal of Volcanology and Geothermal Research, 2017

Abstract The Auckland Volcanic Field (AVF), which last erupted ca. 550 years ago, is a late Quate... more Abstract The Auckland Volcanic Field (AVF), which last erupted ca. 550 years ago, is a late Quaternary monogenetic basaltic volcanic field (ca. 500 km 2 ) in the northern North Island of New Zealand. Prior to this study only 12 out of the 53 identified eruptive centres of the AVF had been reliably dated. Careful sample preparation and 40 Ar/ 39 Ar analysis has increased the number of well-dated centres in the AVF to 35. The high precision of the results is attributed to selection of fresh, non-vesicular, non-glassy samples from lava flow interiors. Sample selection was coupled with separation techniques that targeted only the groundmass of samples with 10 μm wide, coupled with ten-increment furnace step-heating of large quantities (up to 200 mg) of material. The overall AVF age data indicate an onset at 193.2 ± 2.8 ka, an apparent six-eruption flare-up from 30 to 34 ka, and a ≤ 10 kyr hiatus between the latest and second-to-latest eruptions. Such non-uniformity shows that averaging the number of eruptions over the life-span of the AVF to yield a mean eruption rate is overly simplistic. Together with large variations in eruption volumes, and the large sizes and unusual chemistry within the latest eruptions (Rangitoto 1 and Rangitoto 2), our results illuminate a complex episodic eruption history. In particular, the rate of volcanism in AVF has increased since 60 ka, suggesting that the field is still in its infancy. Multiple centres with unusual paleomagnetic inclination and declination orientations are confirmed to fit into a number of geomagnetic excursions, with five identified in the Mono Lake, two within the Laschamp, one within the post-Blake or Blake, and two possibly within the Hilina Pali.

New Zealand Journal of Geology and Geophysics, 2011

Bulletin of Volcanology, 2013

ABSTRACT The Auckland Volcanic Field (AVF) is a dormant monogenetic basaltic field located in Auc... more ABSTRACT The Auckland Volcanic Field (AVF) is a dormant monogenetic basaltic field located in Auckland, New Zealand. Though soil gas CO2 fluxes are routinely used to monitor volcanic regions, there have been no published studies of soil CO2 flux or soil gas CO2 concentrations in the AVF to date or many other monogenetic fields worldwide. We measured soil gas CO2 fluxes and soil gas CO2 concentrations in 2010 and 2012 in varying settings, seasons, and times of day to establish a baseline soil CO2 flux and to determine the major sources of and controlling influences on Auckland's soil CO2 flux. Soil CO2 flux measurements varied from 0 to 203 g m−2 day−1, with an average of 27.1 g m−2 day−1. Higher fluxes were attributed to varying land use properties (e.g., landfill). Using a graphical statistical approach, two populations of CO2 fluxes were identified. Isotope analyses of δ13CO2 confirmed that the source of CO2 in the AVF is biogenic with no volcanic component. These data may be used to assist with eruption forecasting in the event of precursory activity in the AVF, and highlight the importance of knowing land use history when assessing soil gas CO2 fluxes in urban environments.

Chemical Geology, 2020

Abstract The Auckland Volcanic Field (AVF) is one of the most intensively studied monogenetic bas... more Abstract The Auckland Volcanic Field (AVF) is one of the most intensively studied monogenetic basalt fields in the world yet its origin remains enigmatic. Magmatism in the AVF occurred from ~193 ka to 500 years bp. The trace element and isotopic diversity of AVF basalts require “small-scale” compositional heterogeneity in the underlying mantle that is comparable in volume to, or slightly larger than, the scale of individual eruptions in the AVF. Olivine from tephra and lava, representing the range of AVF compositions, was crushed and analysed for 3He/4He, and He and CO2 concentrations in an attempt to further characterize and explain the significance of the AVF “end-members”. AVF basalts show a negative covariation between the amount of CO2 released by crushing of olivine and the whole rock concentrations of highly incompatible trace elements, such as Ba, Rb, Nb, Zr, Ti and K. In contrast, the amount of He released by crushing shows no simple relations with the same incompatible elements or their ratios. This leads to a significant variation in CO2/3He ratios (9.4 × 107–3.5 × 109) that may relate to differences in magma ascent dynamics, as well as to different magma sources. The measured CO2/He ratios may have been influenced by varying amounts of CO2 diffusion into vapour bubbles within melt inclusions that depend on melt composition and magma ascent rate. However, petrographically there is no evidence for systematic differences in the size or quantity of vapour bubbles in olivine-hosted melt inclusions. 3He/4He ratios in 14 AVF samples studied here show a narrow range from 6.57 to 7.26 RA (mean of 7.10 ± 0.26). This may imply a dominance of the mantle helium budget by small-scale heterogeneities. Alternatively, the 3He/4He results suggest that the tectonic and magmatic history of the mantle beneath the AVF has effectively hybridized the 3He/4He ratio to a larger extent than for highly incompatible trace element ratios and Pb-Nd-Sr isotopes. The value of ~7 RA for the mantle source of AVF basalts, in light of other evidence, suggests that there is a relatively homogeneous He isotope composition for the Zealandia-Antarctic mantle domain.