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Journal articles on the topic "Taupō volcano"
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Illsley-Kemp, Finnigan, Pasan Herath, Calum J. Chamberlain, Konstantinos Michailos, and Colin J. N. Wilson. "A decade of earthquake activity at Taupō Volcano, New Zealand." Volcanica 5, no. 2 (October 27, 2022): 335–48. http://dx.doi.org/10.30909/vol.05.02.335348.
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Taupō, New Zealand, is an active caldera volcano that in recent times has erupted on average every ~500 years, with the latest explosive eruption in 232±10 CE. Monitoring at Taupō is challenging as there has been no eruptive activity in documented history; however, Taupō does undergo periods of unrest on roughly a decadal timescale, such as in 2019. Key to identifying these unrest periods is understanding what represents 'normal' inter-unrest activity. In this study, we generate an earthquake catalogue for Taupō for 2010–2019 inclusive, consisting of 46,481 earthquakes. This shows that the Taupō region has background earthquake rates of 50–200 earthquakes per month and the 2019 unrest episode was preceded by an exponential increase in earthquake rate. We also show that when attenuation is accounted for there is no evidence for low-frequency earthquakes at Taupō, and that this is an important consideration for volcano monitoring and determining the presence of significant magma movement.
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Hopkins, Jenni L., Janine E. Bidmead, David J. Lowe, Richard J. Wysoczanski, Bradley J. Pillans, Luisa Ashworth, Andrew B. H. Rees, and Fiona Tuckett. "TephraNZ: a major- and trace-element reference dataset for glass-shard analyses from prominent Quaternary rhyolitic tephras in New Zealand and implications for correlation." Geochronology 3, no. 2 (September 23, 2021): 465–504. http://dx.doi.org/10.5194/gchron-3-465-2021.
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Abstract. Although analyses of tephra-derived glass shards have been undertaken in New Zealand for nearly four decades (pioneered by Paul Froggatt), our study is the first to systematically develop a formal, comprehensive, open-access reference dataset of glass-shard compositions for New Zealand tephras. These data will provide an important reference tool for future studies to identify and correlate tephra deposits and for associated petrological and magma-related studies within New Zealand and beyond. Here we present the foundation dataset for TephraNZ, an open-access reference dataset for selected tephra deposits in New Zealand. Prominent, rhyolitic, tephra deposits from the Quaternary were identified, with sample collection targeting original type sites or reference locations where the tephra's identification is unequivocally known based on independent dating and/or mineralogical techniques. Glass shards were extracted from the tephra deposits, and major- and trace-element geochemical compositions were determined. We discuss in detail the data reduction process used to obtain the results and propose that future studies follow a similar protocol in order to gain comparable data. The dataset contains analyses of glass shards from 23 proximal and 27 distal tephra samples characterising 45 eruptive episodes ranging from Kaharoa (636 ± 12 cal yr BP) to the Hikuroa Pumice member (2.0 ± 0.6 Ma) from six or more caldera sources, most from the central Taupō Volcanic Zone. We report 1385 major-element analyses obtained by electron microprobe (EMPA), and 590 trace-element analyses obtained by laser ablation (LA)-ICP-MS, on individual glass shards. Using principal component analysis (PCA), Euclidean similarity coefficients, and geochemical investigation, we show that chemical compositions of glass shards from individual eruptions are commonly distinguished by major elements, especially CaO, TiO2, K2O, and FeOtt (Na2O+K2O and SiO2/K2O), but not always. For those tephras with similar glass major-element signatures, some can be distinguished using trace elements (e.g. HFSEs: Zr, Hf, Nb; LILE: Ba, Rb; REE: Eu, Tm, Dy, Y, Tb, Gd, Er, Ho, Yb, Sm) and trace-element ratios (e.g. LILE/HFSE: Ba/Th, Ba/Zr, Rb/Zr; HFSE/HREE: Zr/Y, Zr/Yb, Hf/Y; LREE/HREE: La/Yb, Ce/Yb). Geochemistry alone cannot be used to distinguish between glass shards from the following tephra groups: Taupō (Unit Y in the post-Ōruanui eruption sequence of Taupō volcano) and Waimihia (Unit S); Poronui (Unit C) and Karapiti (Unit B); Rotorua and Rerewhakaaitu; and Kawakawa/Ōruanui, and Okaia. Other characteristics, including stratigraphic relationships and age, can be used to separate and distinguish all of these otherwise-similar tephra deposits except Poronui and Karapiti. Bimodality caused by K2O variability is newly identified in Poihipi and Tahuna tephras. Using glass-shard compositions, tephra sourced from Taupō Volcanic Centre (TVC) and Mangakino Volcanic Centre (MgVC) can be separated using bivariate plots of SiO2/K2O vs. Na2O+K2O. Glass shards from tephras derived from Kapenga Volcanic Centre, Rotorua Volcanic Centre, and Whakamaru Volcanic Centre have similar major- and trace-element chemical compositions to those from the MgVC, but they can overlap with glass analyses from tephras from Taupō and Okataina volcanic centres. Specific trace elements and trace-element ratios have lower variability than the heterogeneous major-element and bimodal signatures, making them easier to fingerprint geochemically.
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Stirling, M. W., and C. J. N. Wilson. "Development of a volcanic hazard model for New Zealand." Bulletin of the New Zealand Society for Earthquake Engineering 35, no. 4 (December 31, 2002): 266–77. http://dx.doi.org/10.5459/bnzsee.35.4.266-277.
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We commence development of a volcanic hazard model for New Zealand by applying the well- established methods of probabilistic seismic hazard analysis to volcanoes. As part of this work we use seismologically-based methods to develop eruption volume - frequency distributions for the Okataina and Taupo volcanoes of the central Taupo Volcanic Zone, New Zealand. Our procedure is to use the geologic and historical record of large eruptions (erupted magma volumes ≥ 0.01 cubic km for Taupo and ≥ 0.5 cubic km for Okataina) to construct eruption volume-frequency distributions for the two volcanoes. The two volcanoes show log-log distributions of decreasing frequency as a function of eruption volume, analogous to the shape of earthquake magnitude-frequency distributions constructed from seismicity catalogues. On the basis of these eruption volume-frequency distributions we estimate the maximum eruption volumes that Taupo and Okataina are capable of producing at probability levels of relevance to engineers and planners. We find that a maximum eruption volume of 0.1 cubic km is expected from Taupo with a 10% probability in 50 years, while Okataina may not produce a large eruption at this probability level. However, at the more conservative 2% probability in 50 years, both volcanoes are expected to produce large eruptions (0.5 cubic km for Okataina and 1 cubic km for Taupo). Our study therefore shows significant differences in eruption probabilities for volcanoes in the same physiographic region, and therefore highlights the importance of establishing unique eruption databases for all volcanoes in a hazard analysis.
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Johnston, David, Brad Scott, Bruce Houghton, Douglas Paton, David Dowrick, Pilar Villamor, and John Savage. "Social and economic consequences of historic caldera unrest at the Taupo volcano, New Zealand and the management of future episodes of unrest." Bulletin of the New Zealand Society for Earthquake Engineering 35, no. 4 (December 31, 2002): 215–30. http://dx.doi.org/10.5459/bnzsee.35.4.215-230.
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In 1998, changes in a number of indicators (earthquakes and uplift) at two of New Zealand's active volcanic caldera systems (Okataina and Taupo) resulted in increased public, local and central government awareness and some concern about the potential significance of volcanic unrest at a caldera volcano. This paper summarises the episodes of unrest recorded at Taupo caldera since 1895. There have been four significant events (1895, 1922, 1963-64 and 1983) that have included earthquake activity and ground deformation. Caldera unrest is one of the most difficult situations the volcanological and emergency management communities will have to deal with. There is potential for adverse social and economic impacts to escalate unnecessarily, unless the event is managed appropriately. Adverse response to caldera unrest may take the form of the release of inappropriate advice, media speculation, unwarranted emergency declarations and premature cessation of economic activity and community services. A non-volcanic-crisis time provides the best opportunity to develop an understanding of the caldera unrest phenomena, and the best time to establish educational programmes, funding systems for enhanced emergency response and volcano surveillance and to develop co-ordinated contingency plans.
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Barker, Simon J., Michael C. Rowe, Colin J. N. Wilson, John A. Gamble, Shane M. Rooyakkers, Richard J. Wysoczanski, Finnigan Illsley-Kemp, and Charles C. Kenworthy. "What lies beneath? Reconstructing the primitive magmas fueling voluminous silicic volcanism using olivine-hosted melt inclusions." Geology 48, no. 5 (February 27, 2020): 504–8. http://dx.doi.org/10.1130/g47422.1.
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Abstract Understanding the origins of the mantle melts that drive voluminous silicic volcanism is challenging because primitive magmas are generally trapped at depth. The central Taupō Volcanic Zone (TVZ; New Zealand) hosts an extraordinarily productive region of rhyolitic caldera volcanism. Accompanying and interspersed with the rhyolitic products, there are traces of basalt to andesite preserved as enclaves or pyroclasts in caldera eruption products and occurring as small monogenetic eruptive centers between calderas. These mafic materials contain MgO-rich olivines (Fo79–86) that host melt inclusions capturing the most primitive basaltic melts fueling the central TVZ. Olivine-hosted melt inclusion compositions associated with the caldera volcanoes (intracaldera samples) contrast with those from the nearby, mafic intercaldera monogenetic centers. Intracaldera melt inclusions from the modern caldera volcanoes of Taupō and Okataina have lower abundances of incompatible elements, reflecting distinct mantle melts. There is a direct link showing that caldera-related silicic volcanism is fueled by basaltic magmas that have resulted from higher degrees of partial melting of a more depleted mantle source, along with distinct subduction signatures. The locations and vigor of Taupō and Okataina are fundamentally related to the degree of melting and flux of basalt from the mantle, and intercaldera mafic eruptive products are thus not representative of the feeder magmas for the caldera volcanoes. Inherited olivines and their melt inclusions provide a unique “window” into the mantle dynamics that drive the active TVZ silicic magmatic systems and may present a useful approach at other volcanoes that show evidence for mafic recharge.
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Houghton, B. F., J. H. Latter, and W. R. Hackett. "Volcanic hazard assessment for Ruapehu composite volcano, taupo volcanic zone, New Zealand." Bulletin of Volcanology 49, no. 6 (December 1987): 737–51. http://dx.doi.org/10.1007/bf01079825.
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Shane, Philip A. R., and Paul C. Froggatt. "Discriminant Function Analysis of Glass Chemistry of New Zealand and North American Tephra Deposits." Quaternary Research 41, no. 1 (January 1994): 70–81. http://dx.doi.org/10.1006/qres.1994.1008.
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AbstractMajor, trace, and rare earth element analyses of volcanic glass are used separately or in combination for correlating Quaternary tephras, often by graphical or simple comparative methods. We have taken a statistical approach using discriminant function analysis (DFA) to assess the relative discriminating power of the different elements in volcanic glasses from several tectonovolcanic provinces. We found that major oxides are powerful discriminating variables for widespread tephras from the Taupo Volcanic Zone in New Zealand and here they can be more discriminating than trace elements. A wide selection of tephras from the western United States can also be distinguished on major oxides alone, particularly those from Cascade Range volcanoes. For tephras from large intracontinental calderas, such as Long Valley or Yellowstone, REE and trace elements are more effective at discriminating than major oxides. However, tephras erupted from the Long Valley area can be distinguished on major oxide composition by DFA, despite their similar chemistry. The selection and relative significance of different elements for discriminating tephras depends on the total data set being compared, as well as the source volcano and the individual eruptive events. Caution must be exercised in the nonstatistical selection of compositional data for characterizing tephras: DFA is a more powerful and objective tool for the comparison of tephra chemistry.
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Cameron, Errol, John Gamble, Richard Price, Ian Smith, William McIntosh, and Mairi Gardner. "The petrology, geochronology and geochemistry of Hauhungatahi volcano, S.W. Taupo Volcanic Zone." Journal of Volcanology and Geothermal Research 190, no. 1-2 (February 2010): 179–91. http://dx.doi.org/10.1016/j.jvolgeores.2009.07.002.
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Manville, V., D. Johnston, S. Stammers, and B. Scott. "Comparative preparedness in New Zealand and the Philippines for response to, and recovery from, volcanic eruptions." Bulletin of the New Zealand Society for Earthquake Engineering 33, no. 4 (December 31, 2000): 445–76. http://dx.doi.org/10.5459/bnzsee.33.4.445-476.
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New Zealand and the Philippines are two of the most tectonically and volcanically active regions in the world, due to their setting as large island chains on the convergent margin of the Pacific Plate. The Philippines has experienced numerous volcanic disasters over the past 400 years with the loss of over 7000 lives and considerable damage to infrastructure. The 1991 eruption of Mount Pinatubo, after 500 years of dormancy, was the largest volcanic eruption globally in the last 50 years, with serious socio-economic consequences for the Philippines. The 1995-6 eruptions of New Zealand's Mount Ruapehu, were the most serious volcanic activity experienced in the country over the last 50 years, but occurred at a frequently active volcano for which monitoring, hazard assessment, and response systems were already in place. Although the eruptions differ in size by two orders of magnitude, they illustrate how volcanic activity impacts infrastructure and society at different levels of economic development and vulnerability. Two of New Zealand's volcanic centres, Taupo and Okataina, have the potential to generate eruptions of a similar, or even greater, scale than Pinatubo. Therefore, lessons learnt from the Philippine experience will be of vital importance in planning for the mitigation of future volcanic disasters in New Zealand.
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Cole, J. W., C. E. Sabel, E. Blumenthal, K. Finnis, A. Dantas, S. Barnard, and D. M. Johnston. "GIS-based emergency and evacuation planning for volcanic hazards in New Zealand." Bulletin of the New Zealand Society for Earthquake Engineering 38, no. 3 (September 30, 2005): 149–64. http://dx.doi.org/10.5459/bnzsee.38.3.149-164.
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Geographic Information Systems (GIS) provide a range of techniques which allow ready access to data, and the opportunity to overlay graphical location-based information for ease of interpretation. They can be used to solve complex planning and management problems. All phases of emergency management (reduction, readiness, response and recovery) can benefit from GIS, including applications related to transportation systems, a critical element in managing effective lifelines in an emergency. This is particularly true immediately before and during a volcanic eruption.
The potential for volcanic activity in New Zealand is high, with 10 volcanoes or volcanic centres (Auckland, Bay of Islands, Haroharo, Mayor Island, Ruapehu, Taranaki, Tarawera, Taupo, Tongariro (including Ngauruhoe) and White Island) recognised as active or potentially active. In addition there are many active and potentially active volcanoes along the Kermadec Island chain. There is a great deal of background information on all of these volcanoes, and GIS is currently being used for some aspects of monitoring (e.g. ERS and Envisat radar interferometry for observing deformation prior to eruptions). If an eruption is considered imminent, evacuation may be necessary, and hence transportation systems must be evaluated. Scenarios have been developed for many centres (e.g. Taranaki/Egmont and Bay of Plenty volcanoes), but so far the use of GIS in planning for evacuation is limited.
This paper looks at the use of GIS, indicates how it is being used in emergency management, and suggests how it can be used in evacuation planning.
Dissertations / Theses on the topic "Taupō volcano"
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Leonard, Graham S. "The evolution of Maroa Volcanic Centre, Taupo Volcanic Zone, New Zealand." Thesis, University of Canterbury. Geology, 2003. http://hdl.handle.net/10092/5437.
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Maroa Volcanic Centre (Maroa) is located within the older Whakamaru caldera, central Taupo Volcanic Zone, New Zealand. Dome lavas make up the majority of Maroa volume, with the large Maroa West and East Complexes (MWC and MEC, respectively) erupted mostly over a short 29 kyr period starting at 251 ± 17 ka. The five mappable Maroa pyroclastics deposits are discussed in detail. The Korotai (283 ± 11 ka), Atiamuri (229 ±12 ka), and Pukeahua (~229 -196 ka) pyroclastics are all s 1 km3 and erupted from (a) northern Maroa, (b) a vent below Mandarin Dome and (c) Pukeahua Dome Complex vents, respectively. The Putauaki (272 ± 10 ka) and Orakonui (256 ± 12 ka) pyroclastics total ~ 4 km3 from a petrologically and geographically very similar central Maroa source. The ~ 220 ka Mokai pyroclastics outcrop partly within Maroa but their source remains unclear, whereas the ~ 240 ka Ohakuri pyroclastics appear to have come from a caldera just north of Maroa. The ages of the Mamaku, Ohakuri and Mokai pyroclastics are equivocaL The Mamaku and Ohakuri pyroclastics appear to be older (~ 240 ka) than the age previously accepted for the Mamaku pyroclastics.
Maroa lavas are all plagioclase-orthopyroxene bearing, commonly with lesser quartz. Hornblende +/- biotite are sometimes present and their presence is correlated with geochemical variation. All Maroa deposits are rhyolites (apart from two high-silica dacite analyses) and are peraluminous and calcic. They all have the trace element signatures of arc-related rocks typical of TVZ deposits. Maroa deposits fall geochemically into three magma types based on Rb and Sr content: M (Rb 80-123 ppm,
Sr 65-88 ppm), T (Rb 80-113 ppm, Sr 100-175 ppm) and N (Rb 120-150 ppm, Sr 35- 100 ppm). The geochemical distinction of these types is also seen in the concentrations of most other elements. Based on the spatial, chronological and petrological similarities of the MWC/MEC and Pukeahua eastern magma associations (termed (1) and (2)) a further four magma associations are determined ((3) through (6)). These six associations account for almost all Maroa deposits. Two end-member models are proposed for the sources of each of the Maroa magma associations: (a) a single relatively shallow magma source feeding spatially clustered eruptions, and (b) a deeper source feeding multiple
shallower offshoots over a wider area. Sources for the Maroa magma associations probably lie on a continuum between these two model end members. The distinction between Maroa and Taupo Volcanic Centres is somewhat arbitrary and is best considered to be the easting directly north of Ben Lomond, north of which most volcanism is older than 100 ka and M and N type, and south of which most volcanism is younger than 100 ka and T type. The remaining boundaries (north to include Ngautuku, west to include Mokauteure and east to include Whakapapa domes) are arbitrary, and
include the farthest domes linked closely, spatially and magmatic ally, to the other Maroa domes.
From 230 to 64 ka there was a hiatus in caldera-forming ignimbrite eruptions. Maroa and the Western Dome Belt (WDB) constitute the largest concentrated volume of eruptions (as relatively gentle lava extrusion) during this period. The rate of Maroa volcanism has decreased exponentially from a maximum prior to 200 ka. In contrast volcanism at Taupo and Okataina has increased from ~ 64 ka to present. The oldest Maroa dome (305 ± 17 ka) constrains the maximum rate of infilling of Whakamaru
caldera as 39-17 km3/kyr. This highlights the extraordinarily fast rate of infilling common at silicic calderas and is in agreement with international case studies, except where post-collapse structural resurgence has continued for more than 100 kyr. The majority of caldera fill, representing voluminous eruption deposits in the first tens of thousands of years post collapse, is buried and only accessible via drilling. The WDB and Maroa are petrologically distinct from one another in terms of some or all of Rb, Sr, Ba and Zr content, despite eruption over a similar period. Magma sources for Maroa and
the WDB may have been partly or wholly derived from the Whakamaru caldera magma system(s), but petrological distinctions among all three mean that Maroa and the WDB cannot be considered as simple magmatic resurgence of the Whakamaru caldera.
Maroa's distinct Thorpe Rd Fault is in fact a fossil feature which hasn't been active in almost 200 kyr. In addition, the graben across Tuahu Dome was likely created by shallow blind diking. Several recent studies across TVZ show structural features with some associated dike intrusion/eruption. Such volcano tectonic interaction is rarely highlighted in TVZ but may be relatively common and lie on a continuum between dike-induced faulting and dikes following structural features. Although rates of
volcanism are now low in Maroa magmatic intrusion appears to remain high. This raises the possibility of a causative link between faulting and volcanism in contrast to traditional views of volcanism controlled by rates of magmatic ascent. Probable future eruptions from Maroa are likely to be of similar scale (<0.1 km3 ) and frequency (every ~ 14,000 years) to most of those over the last 100 ka. Several towns lie in a range of zones of Maroa volcanic hazard from total destruction to possible ash fall. However, the probability of a future eruption is only ~ 0.6 % in an 80 year lifetime.
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Ritchie, Alistair B. H. "Volcanic geology and geochemistry of Waiotapu Ignimbrite, Taupo Volcanic Zone, New Zealand." Thesis, University of Canterbury. Geological Sciences, 1996. http://hdl.handle.net/10092/6588.
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Waiotapu Ignimbrite (0.710 ± 0.06 Ma) is a predominantly densely welded, purple-grey coloured, pumice rich lenticulite, which is exposed on both eastern and western flanks of Taupo Volcanic Zone. The unit is uniform in terms of lithology and mineralogy over its entire extent and has been deposited as a single flow unit. The unit contains abundant pumice clasts which are often highly attenuated (aspect ratios of c.1 :30) and are evenly distributed throughout the deposit. Lithic fragments are rare, never exceeding 1% of total rock volume at an outcrop and no proximal facies, such as lithic lag breccias, have been identified.
The deposit is densely welded to the base and only in more distal exposure does the ignimbrite become partially welded at the top of the deposit. Post-depositional devitrification is pervasive throughout the deposit, often destroying original vitroclastic texture in the matrix. Vapour phase alteration is extensive in welded and partially welded facies of the deposit.
Pumices within Waiotapu Ignimbrite appear to have been derived from two distinct magma batches, with differing Rb concentrations, that originated along different fractionation trends. Type-A pumices have significantly lower Rb than the subordinate type-B pumices. The presence of the pumices may represent the simultaneous evisceration of two spatially discrete magma chambers or the type-B chamber may have been intruded into type-A body, the magmas subsequently mingling prior to, or during, the eruption.
The source of Waiotapu Ignimbrite is poorly constrained, largely owing to the lack of meaningful maximum lithic data, and poor exposure of the unit. The distribution of the ignimbrite suggests that it was erupted from within Kapenga volcanic centre. If so the most proximal exposures of Waiotapu Ignimbrite are approximately 10km from the vent. Intensive and voluminous silicic volcanism, beginning with the eruption of the 0.33 Ma Whakamaru Group Ignimbrite eruptions, and extensive faulting within Kapenga volcanic centre will have obscured any intra-caldera Waiotapu Ignimbrite. The mechanism of eruption suggests that the source may not have been a caldera in the strictest sense, but instead a series of near linear fissures aligned with the trend of regional faulting.
Waiotapu Ignimbrite was generated in one sustained eruption and produced an energetic and high temperature pyroclastic flow. The lack of any recognised preceding plinian deposit, coupled with the energetic nature and paucity of lithics suggests eruption by an unusual mechanism. The eruption most likely resulted from the large scale collapse of a caldera block into the underlying chamber resulting in high discharge rates, which were no conducive to the development of a convecting column, and minimal vent erosion, resulting in negligible entrainment of lithics.
The density of welding and recrystallisation textures suggest that the flow retained heat to considerable distances which allowed the ignimbrite to weld densely to the base. The deposit was most likely progressively aggraded from the base, with material being supplied from an overriding particulate flow.
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Krippner, Janine Barbara. "Ngauruhoe inner crater volcanic processes of the 1954-1955 and 1974-1975 eruptions." The University of Waikato, 2009. http://hdl.handle.net/10289/2760.
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Ngauruhoe is an active basaltic andesite to andesite composite cone volcano at the southern end of the Tongariro volcanic complex, and most recently erupted in 1954-55 and 1974-75. These eruptions constructed the inner crater of Ngauruhoe, largely composed of 1954-55 deposits, which are the basis of this study. The inner crater stratigraphy, exposed on the southern wall, is divided into seven lithostratigraphic units (A to G), while the northern stratigraphy is obscured by the inward collapse of the crater rim. The units are, from oldest to youngest: Unit A, (17.5 m thick), a densely agglutinated spatter deposit with sharp clast outlines; Unit B, (11.2 m) a thick scoria lapilli deposit with local agglutination and scattered spatter bombs up to 1 m in length; Unit C, (6.4 m thick) a clastogenic lava deposit with lateral variations in agglutination; and Unit D, (10 m thick) a scoria lapilli with varying local agglutination. The overlying Unit E (15 cm thick) is a fine ash fallout bed that represents the final vulcanian phase of the 1954-55 eruption. Unit F is a series of six lapilli and ash beds that represent the early vulcanian episode of the 1974-75 eruption. The uppermost Unit G (averaging 10 m thick) is a densely agglutinated spatter deposit that represents the later strombolian phase of the 1974-75 eruption. Units A-D juvenile clasts are porphyritic, with phenocrysts of plagioclase, orthopyroxene, clinopyroxene, minor olivine, within a microlitic glassy groundmass. Quartzose and greywacke xenoliths are common in most units, and are derived from the underlying basement. The 1954-55 and 1974-75 eruptions are a product of a short-lived, continental arc medium-K calc-alkaline magma. The magma originated from the mantle, then filtered through the crust, undergoing assimilation and fractionation, and evolving to basaltic andesite and andesite compositions. The magma body stagnated in shallow reservoirs where it underwent further crustal assimilation and fractionation of plagioclase and olivine, and homogenisation through magma mixing. Prior to the 1954-55 eruption a more primitive magma body was incorporated into the melt. The melt homogenised and fed both the 1954-55 and 1974-75 eruptions, with a residence time of at least 20 years. The 1954-55 eruption produced alternating basaltic andesite and andesite strombolian activity and more intense fire fountaining, erupting scoria and spatter that built up the bulk of the inner crater. A period of relative quiescence allowed the formation of a cooled, solid cap rock that resulted in the accumulation of pressure due to volatile exsolution and bubble coalescence. The fracturing of the cap rock then resulted in a vulcanian eruption, depositing a thin layer of fine ash and ballistic blocks. The 1974-75 eruption commenced with the rupturing of the near-solid cap rock from the 1954-55 eruption in an explosive vulcanian blast, the result of decompressional volatile exsolution and bubble coalescence, and possible magma-water interaction. The eruption later changed to strombolian style, producing a clastogenic lava that partially flowed back into the crater.
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Karhunen, Ritva Annikki. "The Pokai and Chimp ignimbrites of NW Taupo Volcanic Zone." Thesis, University of Canterbury. Geology, 1993. http://hdl.handle.net/10092/5791.
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Taupo Volcanic Zone (TVZ) is the largest active volcanic belt in New Zealand, and has erupted >10.000 km3 of dominantly rhyolitic magma during the last 1.6 m.y. This study concerns the field relations, volcanology and petrology of two post-Whakamaru (330 ka) - pre-Mamaku (140 ka) ignimbrites, informally named as the Pokai and Chimp ignimbrites, occurring in a ca. 360 km2 area SW and W from Rotorua in the north-western TVZ.
The Pokai Ignimbrite has a minimum volume of ca. 33 km3 DRE, whereas the older Chimp Ignimbrite has a minimum volume of only ca. 5 km3 DRE. Of the two ignimbrites the younger Pokai Ignimbrite is better preserved and is thus the main emphasis in this thesis.
The Chimp Ignimbrite is relatively pumice- and crystal-poor (1-2 vol. % phenocrysts), and the exposed flow units are relatively thin (4-6 m). A short plinian phase preceded the Chimp Ignimbrite, whereas the Pokai Ignimbrite is marked by a number of pre-ignimbrite air-fall pumice and ash layers. The Pokai Ignimbrite represents a multiple flow unit ignimbrite, with single flow units usually ranging from 6-30 m. Thick deposits (>20 m thick) are usually welded in the upper middle part of the deposit. Ground deposits, i.e. layer 1 deposits, are rare. Field evidence suggest that the Pokai Ignimbrite
originated from the Kapenga Volcanic Centre, a multiple caldera structure in the northern central TVZ.
Two pumice types occur in the Pokai Ignimbrite; a crystal-poor type (2-3 % phenocrysts) and a crystal-rich type (6-12 % phenocrysts). Plagioclase is the dominant phenocryst throughout, with minor amounts of orthopyroxene, Fe-Ti oxides and quartz, which occurs in ca. 30 % of the pumices.
Hornblende and clinopyroxene are present occasionally. The Pokai Ignimbrite ranges from mildly to strongly peraluminous, whereas the Chimp Ignimbrite is mildly peraluminous, both coinciding with other TVZ rhyolitic ignimbrites, but clearly differing from the rhyolitic lavas which are usually metaluminous to only mildly peraluminous.
Whereas most TVZ rhyolitic eruptives have been regarded as relatively homogeneous, the Pokai Ignimbrite shows significant geochemical variation. The magma chamber was compositionally
zoned from crystal-poor, high silica, low Sr (77 % SiO2 , 50 ppm Sr) rhyolitic top to more crystal-rich, low silica, high Sr (70 % SiO2 , 130 ppm Sr) rhyolite at the deeper levels. Prior to the eruption vigorous mixing of magma from different levels occurred, producing different pumice types in the airfall deposits, and multiple phenocryst populations in single pumice clasts. As the eruption progressed successively deeper levels of the magma chamber were tapped, the last eruption products representing the less evolved, crystal-rich magma. Least squares and Rayleigh fractionation models indicate that the Pokai, and the Chimp magmas most probably generated by AFC from TVZ andesitic magmas contaminated by Mesozoic basement sediments.
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Ashwell, Paul. "Controls on rhyolite lava dome eruptions in the Taupo Volcanic Zone." Thesis, University of Canterbury. Geological Sciences, 2014. http://hdl.handle.net/10092/8965.
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The evolution of rhyolitic lava from effusion to cessation of activity is poorly understood. Recent lava dome eruptions at Unzen, Colima, Chaiten and Soufrière Hills have vastly increased our knowledge on the changes in behaviour of active domes. However, in ancient domes, little knowledge of the evolution of individual extrusion events exists. Instead, internal structures and facies variations can be used to assess the mechanisms of eruption.
Rhyolitic magma rising in a conduit vesiculates and undergoes shear, such that lava erupting at the surface will be a mix of glass and sheared vesicles that form a permeable network, and with or without phenocryst or microlites. This foam will undergo compression from overburden in the shallow conduit and lava dome, forcing the vesicles to close and affecting the permeable network. High temperature, uniaxial compression experiments on crystal-rich and crystal-poor lavas have quantified the evolution of porosity and permeability in such environments. The deformation mechanisms involved in uniaxial deformation are viscous deformation and cracking. Crack production is controlled by strain rate and crystallinity, as strain is localised in crystals in crystal rich lavas. In crystal poor lavas, high strain rates result in long cracks that drastically increase permeability at low strain. Numerous and small cracks in crystal rich lavas allow the permeable network to remain open (although at a lower permeability than undeformed samples) while the porosity decreases.
Flow bands result from shear movement within the conduit. Upon extrusion, these bands will become modified from movement of lava, and can therefore be used to reconstruct styles of eruption. Both Ngongotaha and Ruawahia domes, from Rotorua caldera and Okataina caldera complex (OCC) respectively, show complex flow banding that can be traced to elongated or aligned vents. The northernmost lobe at Ngongotaha exhibits a fan-like distribution of flow bands that are interpreted as resulting from an initial lava flow from a N – S trending fissure. This flow then transitioned into intrusion of obsidian sheets directly above the conduit, bound by wide breccia zones which show vertical movement of the sheets. Progressive intrusions then forced the sheets laterally, forming a sequence of sheets and breccia zones. At Ruawahia, the flow bands show two types of eruption; long flow lobes with ramp structures, and smaller spiny lobes which show vertical movement and possible spine extrusion. The difference is likely due to palaeotopography, as a large pyroclastic cone would have confined the small domes, while the flow lobes were unconfined and able to flow down slope. The vents at Ruawahia are aligned in a NE – SW orientation. Both domes are suggested to have formed from the intrusion of a dyke.
The orientations of the alignment or elongation of vents at Ngongotaha and Ruawahia can be attributed to the overall regional structure of the Taupo Volcanic Zone (TVZ). At Ngongotaha, the N – S trending elongated vent is suggested to be controlled by a N – S trending caldera collapse structure at Rotorua caldera. The rest of the lobes at Ngongotaha, as well as other domes at Rotorua caldera, are controlled by the NE – SW trending extensional regional structure or a NW – SE trending basement structure. The collapse of Rotorua caldera, and geometry of the deformation margin, are related to the interplay of these structures. At Ruawahia, the NE – SW trending vent zone is parallel to the regional extension across the OCC, as shown by the orientation of intrusion of the 1886AD dyke through the Tarawera dome complex.
The NE – SW trending regional structures observed at both Rotorua caldera and Okataina caldera complex are very similar to each other, but differ from extension within the Taupo rift to the south. Lava domes, such as Ngongotaha, that are controlled by this structure show that the ‘kink’ in the extension across Okataina caldera complex was active across Rotorua caldera during the collapse at 240 ka, and possibly earlier.
This study shows the evolution of dyke-fed lava domes during eruption, and the control of regional structures in the location and timing of eruption. These findings improve our knowledge of the evolution of porosity and permeability in a compacting lava dome, as well as of the structures of Rotorua caldera, the longevity of volcanic activity at dormant calderas and the hazard potential of dyke-fed lava domes.
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Cattell, Hamish. "Volcanic evolution of the Huka Group at Wairakei-Tauhara Geothermal Field, Taupo Volcanic Zone, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2015. http://hdl.handle.net/10092/10850.
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Basin-hosted stratigraphy in volcanic arc settings reflects the interplay between ancient environments, volcanism, magmatism and tectonism. Lithostratigraphic variations within basins can be used to identify the location and timing of the processes contributing to their evolution. However, when deposits are hydrothermally altered, the use of many traditional analytical techniques for assessing their volcanic origin become impracticable, making analysis challenging. Examination then relies on an integrated mix of detailed macroscopic assessment and techniques utilising remaining stable magmatic phases. The Huka Group at Wairakei-Tauhara Geothermal Field (Wairakei-Tauhara) is primarily comprised of volcanic deposits preserving ~300 kyr of evolution in the Taupo Volcanic Zone (TVZ), New Zealand. Intensive geothermal well drilling in the field has identified the distribution and variation comprising its Waiora and Huka Falls Formations. The volcanic, structural and environmental history of the Huka Group, however, remains poorly understood. This thesis is concerned with identifying the stratigraphic and geothermal significance of the Huka Group from recent drill core samples at Wairakei-Tauhara. Drill core facies analysis confirm a spatially and temporally complex depositional history at the site. Deposits forming Waiora Formation were sourced from local explosive and effusive eruptions over ~100 kyrs within extensional basins hosting paleo-Lake Huka. Lacustrine and fluvial deposition prevailed for the following ~200 kyrs, as volcanism ceased, depositing the Huka Falls Formation. Frequent drilling of Huka Falls Formation has identified and thoroughly constrained facies variations of a local pyroclastic member, the Middle Huka Falls Formation. This eruption evolved as a series of water-supported, eruption-fed density currents from a sublacustrine vent in Tauhara transported beneath Lake Huka. Examined Huka Group core samples were hydrothermally altered and required the use of novel assessment techniques for comprehensive stratigraphic assessment. This alteration provided an opportunity to locally date the geothermal system within the Huka Group reservoir. Stratigraphic variations of resistant magmatic phenocrysts (feldspar) and immobile elements (Ti, Zr, V and Y) added new details of depositional processes and lithostratigraphy. Regional magmatic immobile element comparisons identified geochemical similarities within Huka Group ignimbrites that may have implications for the longevity and recurrence of caldera magma systems in TVZ. Geothermal activity in the Waiora Formation reservoir was dated using pristine hydrothermal adularia and 40Ar/39Ar dating methods. Results recognised a young phase of the system’s evolution (<30 ka) and the applicability of 40Ar/39Ar dating for use in geothermal chronology. Lastly, a conceptual evolutionary model for the Huka Group presents ~300 kyr of depositional processes, landscapes and structural events at Wairakei-Tauhara. The long-lived lacustrine setting is recognised to have been continually modified by episodic volcanism and gradual tectonism. Variations in Huka Group stratigraphy between the Wairakei and Tauhara Fields identify contemporaneous, but separate evolution of the underlying controlling horst (ridge) and graben (basin) structure. This study highlights the unique tectonic, magmatic, volcanic and sedimentary processes forming basins in the TVZ and improve our understanding on the geological evolution of geothermal systems. Techniques trialled in the study are demonstrated to be suitable for investigating altered volcanic materials and can be utilised elsewhere in the TVZ or other geothermal settings.
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Rogan, William. "New insights on magmatic processes from trace element zonation in phenocrysts." Thesis, Open University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363965.
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Harrison, A. J. "Crustal and upper mantle structure of the Taupo Volcanic Zone, New Zealand." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603773.
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The Taupe Volcanic Zone (TVZ) is a major Pliocene-Quaternary NNE-SSW orientated volcano-techonic complex, in central North Island, New Zealand. It is a region characterised by voluminous rhyolitic eruptions, high natural heat flow, intense shallow seismic activity and active NW-SE extension. The central portion of the TVZ is regarded as the most frequently active and productive silicic volcanic system on Earth, yet to date no direct evidence for the source for the magmatisim has been found. In February and December 2001, as part of the NIGHT (North Island GeopHysical Transect) experiment, a total of ten 500 kg land slots were fired into an NW-SE array that ran the width of central North Island, New Zealand. An additional passive array of broad-band and short-period instruments centred on the TVZ recorded local and teleseismic earthquakes for six and a half months. Forward and inverse modelling of this active and shallow (< 10 km) earthquake data shows low-velocity (2.0-3.5 km/s) volcanic sediments reaching a maximum thickness of 3 km beneath the central TVZ. Underlying these sediments to 16 km depth are velocities of 5.0-6.5 km/s, interpreted as quartzo-fieldspathic crust. East and west of the TVZ, these velocities are observed to depths of 30 and 23 km respectively. Beneath the TVZ, material with P-wave velocities of 6.9-7.3 km/s are observed to ~30 km depth and are interpreted as heavily intruded or underplated lower crust. Modelling of deep (> 40 km) earthquake events originating near the top of the subducting Pacific plate, reveals a low-velocity region (LVR) (Vp of 7.4-7.8 km/s) overlying a northwest dipping high-velocity structure that coincides with the Wadati-Benioff zone.
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Spinks, Karl D. "Rift architecture and Caldera volcanism in the Taupo Volcanic Zone, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2005. http://hdl.handle.net/10092/4944.
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The Taupo Volcanic Zone (TVZ) is investigated to determine the interaction of regional structure and volcanism. A three-tiered approach is employed involving (i) analysis of rift geometry and segmentation in Modem TVZ(<300 ka) from remote sensing and digital topographic data; (ii) fault kinematic data collected along the length of TVZ; and (iii) combining new and existing volcanological data for TVZ. Modem TVZ is a NNE-SSW trending intra-arc rift zone, subject to dextral transtension, and characterised by a segmented axial rift zone with a number of offset and variably oriented rift segments. These segments are subject to varying degrees of extension, and a general correlation exists between the amount of extension and the volume and style of volcanism in each segment. Segments with the highest degrees of extension correspond to the Okataina and Taupo Caldera Complexes in the central rhyolitic zone of Modem TVZ, while segments with a higher degree of dextral transtension correspond to the volumetrically-subordinate andesitic extremities.
The influence of the structural framework on the shape and formation of calderas in Modem TVZ has been inferred from remote sensing and ground-based structural analysis. Detailed analysis of caldera structure and geometry in Modem TVZ indicates that caldera evolution is largely a function of caldera location relative to the axial rift zone. Calderas peripheral to the rift are simple, single-event structures, while those located within the axial rift zone are multiple-event caldera complexes with geometries dictated by their coincidence with rift faulting. These results show that in Modem TVZ the type, volume, and spatial distribution of magmatic activity is strongly influenced by rift structure and kinematics.
The inter-relationship between rift geometry and caldera-complex development is particularly clear at the intra-rift Okataina Caldera Complex (OCC). OCC is located at a step-over in the rift where local rotation of the extension direction accompanies the development of a major transfer zone. Three main collapse events are spatially concentrated in a zone of orthogonal extension within the transfer zone. The 28 x 22 km OCC is elongate parallel to the extension direction, with a complicated topographic margin largely controlled by regional faulting. Major embayments occur on each side of OCC where it is intersected by adjacent rift segments. These are contiguous with two intra-caldera dome complexes forming two overlapping linear vent zones, which transect the caldera complex. The development of volcanism at OCC records the progressive interaction between offset rift segments and the propagation of overlapping rift segment axes. As rift propagation proceeded, a diffuse zone of volcanism progressively concentrated in the centre of the transfer zone then divided into two spatially restricted eruptive centres as through-going faults became established.
Field investigations at OCC reveal a major revision to the eruptive stratigraphy that has implications for the development of the caldera and for hazard assessment in northern TVZ. Kawerau Ignimbrite is a partially welded pumice-rich ignimbrite that fills Puhipuhi Basin on the eastern side of the caldera complex and forms a thick terrace in and around the Kawerau township area. Within Puhipuhi Basin it is ~100 m thick, exposed on clear-felled knolls and locally forms jointed bluffs in thickest sections where it is valley ponded. Originally mapped as Kaingaroa Ignimbrite, it was subsequently considered distinct and renamed Kawerau Ignimbrite by Beresford & Cole (2000) with an accepted age of 240 ka.
In Puhipuhi basin the Kawerau Ignimbrite overlies both the ~280 ka Matahina and ~65 ka Rotoiti ignimbrites and also the older tephras of the 43-31 ka Mangaone Subgroup. Whole-rock and glass geochemistry tie the ignimbrite specifically to the 33 ka Unit I eruptive phase of the subgroup, vastly increasing the eruptive volume of that unit and implying caldera collapse in this recent phase of OCC activity. Two pumice compositions are identified, reflecting eruption of two distinct magma bodies.
Vertical variation in the ignimbrite records rapid depletion of a subordinate dacitic magma such that pumices of this composition are rare beyond proximal exposures. Lithic and pumice size distribution data indicate a source within OCC to the west of Puhipuhi basin. The residual volume of the ignimbrite is <15 km3, but estimates of the original volume approach 50 km3 when intra-caldera volumes are considered. Kawerau Ignimbrite thus represents the largest eruption from OCC in the last 65 ka since the Rotoiti event, and is the youngest partially-welded ignimbrite in TVZ.
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Beresford, Stephen Willis. "Volcanology and geochemistry of the Kaingaroa Ignimbrite, Taupo Volcanic Zone, New Zealand." Thesis, University of Canterbury. Geological Sciences, 1997. http://hdl.handle.net/10092/5738.
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The 0.23 Ma Kaingaroa Ignimbrite is a composite multiple flow-unit ignimbrite erupted from Reporoa Caldera, Taupo Volcanic Zone (TVZ), New Zealand.
The Kaingaroa Ignimbrite has a complex internal stratigraphy with a complex basal tephra sequence of intercalated fall, surge and flow deposits, and three ignimbrite units, with strikingly proximal to medial facies variation. Proximal facies deposits are dominated by coarse lithic breccias up to 45m thick which are interpreted as co-ignimbrite lag breccias. These lag breccias are-some of the thickest so far documented. Welding and thickness variations in the extensive Old Waiotapu Rd (OWR; kg1) and Webb ignimbrite unit (WIU; kg2) suggests gradual thickening away from source, interpreted to represent ponding in a shallow alluvial lowland or basin.
A detailed lithic componentry study indicates changes in lithic diversity and abundance between stratigraphic units which mark changes in vent conditions, increasing depth of lithic provenance and hence inferred fragmentation level. Lithic fragments reveal aspects of the sub-caldera geology, which is dominated by an andesitic volcano with leuco-gabbroic subvolcanic roots, intercalated welded ignimbrites, rare low-grade metasedimentary basement and meta-rhyolites. Gabbros and meta-rhyolites suggest complex metasomatic and fumarolic processes adjacent to the Kaingaroa magma system. The presence of tourmaline-bearing meta-rhyolites and meta-ignimbrites and tourmalinite is the first documented occurrence of tourmaline and tourmalinite in TVZ.
Four pumice types are defined on pumice chemistry and mineralogy. These pumices are interpreted to represent samples of a weakly continuously zoned magma chamber (70-75% SiO2), which was progressively tapped during the eruption. Trace element and rare earth element systematics are consistent with an origin of type A magma from a type D parent by minor fractionation of plagioclase, zircon, and trace contents of Fe/Ti oxides and orthopyroxene. An additional hornblende-, 2-pyroxene-phyric dacite pumice/bleb (69% SiO2) was sampled from the Tokiaminga sub-unit, but is mineralogically and compositionally different from Kaingaroa pumices. Post-caldera rhyolites are
mineralogically and chemically variable, with broad similarities to Kaingaroa pumices. The Kaingaroa magma components show reverse isotopic zonation i.e. decreasing 87Sr/86Sr and increasing 143Nd/144Nd with differentiation, suggesting syn-eruptive mingling and evisceration of the multiple magma batches occurred during the climactic caldera collapse phase.
The Kaingaroa Ignimbrite has been mis-correlated by previous workers with the Matahina, Mamaku, and Rangatira Point ignimbrites, and three new units described in this thesis; Kawerau ignimbrite, Wheao sheet, and the welded ignimbrite of Wairakei drill holes. It is clear that ignimbrite correlation is difficult in TVZ because of the poor exposure and the limited stratigraphic sections that document multiple units. The Kawerau ignimbrite remains an enigma, largely because of the anomalously high Zr, Hf and Zn contents, suggestive of a relationship to 'alkaline' rhyolites, and the presence of unusual magnesium poor manganoan fayalite of vapour-phase origin. Identification of these units and other
intermediate size ignimbrite in the stratigraphic interval between Whakamaru-group, and Mamaku ignimbrites requires further careful documentation, but suggests a temporal clustering of ignimbrites sourced from throughout TVZ.
Books on the topic "Taupō volcano"
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Wilson, C. J. N. The Taupo eruption, New Zealand. London: Royal Society of London, 1985.
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Active volcanoes and geothermal systems, Taupo volcanic zone: International Volcanological Congress. Lower Hutt, N.Z: New Zealand Geological Survey, Dept. of Scientific and Industrial Research, 1987.
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Frank, Simmons Stuart, and Weaver S. D, eds. Taupo volcanic zone, New Zealand. Amsterdam: Elsevier, 1995.
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F, Houghton B., Weaver S. D, and International Volcanological Congress (1986 : Auckland, N.Z., etc.), eds. Taupo volcanic zone: Tour guides C1, C4, C5, and A2. Lower Hutt, N.Z: New Zealand Geological Survey, Dept. of Scientific and Industrial Research, 1986.
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Mathews, B. Volcanic Trout: A Complete Guide to Fishing the Taupo Region. Shoal Bay Press, 2003.
Find full textBook chapters on the topic "Taupō volcano"
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Wilson, C. J. N., A. M. Rogan, I. M. E. Smith, D. J. Northey, I. A. Nairn, and B. F. Houghton. "Caldera Volcanoes of the Taupo Volcanic Zone, New Zealand." In Collected Reprint Series, 8463–84. Washington, DC: American Geophysical Union., 2014. http://dx.doi.org/10.1002/9781118782095.ch18.
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Healy, J. "Structure and Volcanism in the Taupo Volcanic Zone, New Zealand." In Geophysical Monograph Series, 151–57. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm006p0151.
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Cole, J. W., D. J. Darby, and T. A. Stern. "Taupo Volcanic Zone and Central Volcanic Region Backarc Structures of North Island, New Zealand." In Backarc Basins, 1–28. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-1843-3_1.
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Manville, V., and K. A. Hodgson. "Paleohydrology of Volcanogenic Lake Break-Out Floods in the Taupo Volcanic Zone, New Zealand." In Natural and Artificial Rockslide Dams, 519–41. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-04764-0_21.
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Giggenbach, W. F. "Composition of fluids in geothermal systems of the Taupo Volcanic Zone, New Zealand, as a function of source magma." In Water-Rock Interaction, 9–12. London: Routledge, 2021. http://dx.doi.org/10.1201/9780203734049-3.
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Fox, Caren. "Environmental Guardians." In Oral History and the Environment, 157—C8.N28. Oxford University PressNew York, 2022. http://dx.doi.org/10.1093/oso/9780190684969.003.0009.
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Abstract The Central North Island region of New Zealand has the highest number of geothermal fields in the world, with seventeen in the Taupō Volcanic Zone (TVZ) of the Central North Island. The relationship that Māori people have had with this resource was not provided for during the development of certain fields of the TVZ during the years 1950–1991. The impact of these policies on the sustainability of the resource is explored in this essay and excerpts from interview with Aroha Campbell from Ohaaki near Reporoa, a village south of Rotorua in New Zealand. The Ohaaki power station was commissioned in 1989 by the Power Development Division of the New Zealand Electricity Department.
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SMITH, ROBYN C. M. "LANDSCAPE RESPONSE TO A MAJOR IGNIMBRITE ERUPTION, TAUPO VOLCANIC CENTER, NEW ZEALAND." In Sedimentation in Volcanic Settings, 123–37. SEPM (Society for Sedimentary Geology), 1991. http://dx.doi.org/10.2110/pec.91.45.0123.
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Simmons, Stuart F., Benjamin M. Tutolo, Shaun L. L. Barker, Richard J. Goldfarb, and François Robert. "Chapter 38: Hydrothermal Gold Deposition in Epithermal, Carlin, and Orogenic Deposits." In Geology of the World’s Major Gold Deposits and Provinces, 823–45. Society of Economic Geologists, 2020. http://dx.doi.org/10.5382/sp.23.38.
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Abstract Epithermal, Carlin, and orogenic Au deposits form in diverse geologic settings and over a wide range of depths, where Au precipitates from hydrothermal fluids in response to various physical and chemical processes. The compositions of Au-bearing sulfidic hydrothermal solutions across all three deposit types, however, are broadly similar. In most cases, they comprise low-salinity waters, which are reduced, have a near-neutral pH, and CO2 concentrations that range from <4 to >10 wt %. Experimental studies show that the main factor controlling the concentration of Au in hydrothermal solutions is the concentration of reduced S, and in the absence of Fe-bearing minerals, Au solubility is insensitive to temperature. In a solution containing ~300 ppm H2S, the maximum concentration of Au is ~1 ppm, representing a reasonable upper limit for many ore-forming solutions. Where Fe-bearing minerals are being converted to pyrite, Au solubility decreases as temperature cools due to the decreasing concentration of reduced S. High Au concentrations (~500 ppb) can also be achieved in strongly oxidizing and strongly acidic chloride solutions, reflecting chemical conditions that only develop during intense hydrolytic leaching in magmatic-hydrothermal high-sulfidation epithermal environments. Gold is also soluble at low to moderate levels (10–100 ppb) over a relatively wide range of pH values and redox states. The chemical mechanisms which induce Au deposition are divided into two broad groups. One involves achieving states of Au supersaturation through perturbations in solution equilibria caused by physical and chemical processes, involving phase separation (boiling), fluid mixing, and pyrite deposition via sulfidation of Fe-bearing minerals. The second involves the sorption of ionic Au on to the surfaces of growing sulfide crystals, mainly arsenian pyrite. Both groups of mechanisms have capability to produce ore, with distinct mineralogical and geochemical characteristics. Gold transport and deposition processes in the Taupo Volcanic Zone, New Zealand, show how ore-grade concentrations of Au can accumulate by two different mechanisms of precipitation, phase separation and sorption, in three separate hydrothermal environments. Phase separation caused by flashing, induced by depressurization and associated with energetic fluid flow in geothermal wells, produces sulfide precipitates containing up to 6 wt.% Au from a hydrothermal solution containing a few ppb Au. Sorption on to As-Sb-S colloids produces precipitates containing tens to hundreds of ppm Au in the Champagne Pool hot spring. Sorption on to As-rich pyrite also leads to anomalous endowments of Au of up to 1 ppm in hydrothermally altered volcanic rocks occurring in the subsurface. In all of these environments, Au-undersaturated solutions produce anomalous concentrations of Au that match and surpass typical ore-grade concentrations, indicating that near-saturated concentrations of dissolved metal are not a prerequisite for generating economic deposits of Au. The causes of Au deposition in epithermal deposits are related to sharp temperature-pressure gradients that induce phase separation (boiling) and mixing. In Carlin deposits, Au deposition is controlled by surface chemistry and sorption processes on to rims of As-rich pyrite. In orogenic deposits, at least two Au-depositing mechanisms appear to produce ore; one involves phase separation and the other involves sulfidation reactions during water-rock interaction that produces pyrite; a third mechanism involving codeposition of Au-As in sulfides might also be important. Differences in the regimes of hydrothermal fluid flow combined with mechanisms of Au precipitation play an important role in shaping the dimensions and geometries of ore zones. There is also a strong link between Au-depositing mechanisms and metallurgical characteristics of ores.
Conference papers on the topic "Taupō volcano"
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Pamukcu, Ayla S., Kylie A. Wright, Guilherme A. R. Gualda, and Darren M. Gravley. "Magma Residence and Eruption at the Taupo Volcanic Center (Taupo Volcanic Zone, New Zealand)." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2019.
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Rocco, Nicole, Adam J. R. Kent, Kari M. Cooper, Chad D. Deering, and Darren Gravley. "GEOCHEMICAL EVOLUTION THROUGH A FULL CALDERA CYCLE: TAUPO VOLCANIC ZONE, NZ." In 115th Annual GSA Cordilleran Section Meeting - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019cd-329060.
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Ebinger, Cynthia, Sophie Aber, Andrew Gase, Samia Sabir, Finnigan Illsley-Kemp, Martha Savage, Jennifer Eccles, and John Ristau. "CASCADING EARTHQUAKE SWARMS IN THE NORTHERN TAUPO VOLCANIC ZONE, NEW ZEALAND." In GSA Connects 2022 meeting in Denver, Colorado. Geological Society of America, 2022. http://dx.doi.org/10.1130/abs/2022am-382271.
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Seelig, Laura, Colin Wilson, Isabelle Chambefort, and Michael Rosenberg. "Rare plutonic xenoliths from a monogenetic basalt highlight magmatic crustal roots in the Taupō Volcanic Zone, New Zealand." In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.9827.
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Pamukcu, Ayla, Guilherme A. R. Gualda, and D. M. Gravley. "EXTRACTION TO ERUPTION: COMPARING THE CRUSTAL RESIDENCE OF LARGE-VOLUME MAGMAS AT THE TAUPŌ VOLCANIC CENTER (NEW ZEALAND)." In GSA Connects 2021 in Portland, Oregon. Geological Society of America, 2021. http://dx.doi.org/10.1130/abs/2021am-366782.
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Wigger, Natalie E., James E. Faulds, Samuel J. Hampton, Josh W. Borella, and Isabelle Chambefort. "FAVORABLE STRUCTURAL SETTINGS FOR POTENTIAL GEOTHERMAL UPWELLINGS IN THE CENTRAL TAUPO VOLCANIC ZONE, NEW ZEALAND." In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-324134.
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Harvey, Mark C., and Julie V. Rowland. "CO2 FLUX INVESTIGATION AT WAIRAKEI, A LOW-CO2 GEOTHERMAL SYSTEM IN THE TAUPO VOLCANIC ZONE, NEW ZEALAND." In 113th Annual GSA Cordilleran Section Meeting - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017cd-292857.
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Corella Santa Cruz, Carlos, Georg Zellmer, Claudine Stirling, Susanne M. Straub, Marco Brenna, Karoly Nemeth, Malcolm Reid, and David Barr. "Origin of compositional variations of Taupo Volcanic Zone (TVZ) eruption products: crustal differentiation or subduction mélange diapirism?" In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.10747.
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Farsky, David, Michael Rowe, Isabelle Chambefort, David Graham, Shane Rooyakkers, Kevin Faure, and Simon Barker. "Understanding Sources and Modification of Primary Magmatic Volatiles in the Taupo Volcanic Zone: Evidence from Helium and Oxygen Isotopes." In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.11854.
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Allen, Sydney M., Guilherme A. R. Gualda, and Darren M. Gravley. "MAGMA IN MOTION: DETERMINING VERTICAL MAGMA POSITIONING IN THE MAGMATIC SYSTEM THAT FED THE OHAKURI ERUPTION, TAUPO VOLCANIC ZONE, NEW ZEALAND." In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-323731.
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