When was the rotorua caldera formed

There are also marked contrasts in the zircon model-age spectra in small- and large-scale eruptive deposits from long-lived silicic centres whether caldera-related or not. For Okataina and Taupo there simply is no relationship between the volumes of the eruptions and the time differences between model-age PDF peaks and eruption ages. Reactivation of a crystal mush and recycling will introduce into the melt-dominant magma body older antecrystic or xenocrystic zircons that cannot be identified on age data alone.

The model ages of these zircons may bear no simple relationship to the residence time of the melt-dominant body itself that eventually is tapped to generate the eruption products. At the voluminous extremes, for super-eruptions of magma volumes of km 3 or more, the ages of the youngest precursor eruptions can be very close to those of the climactic outburst. Annen et al. The latter time-scale will control the periodicity of eruptions, and in areas of active rifting such as in the Taupo Volcanic Zone Rowland et al.

The first reflects the observation discussed in the previous section that larger eruptions are the products of magma chambers with correspondingly large inputs and losses of heat to drive melt generation and differentiation of the magmas. Similar inferences have been made at Long Valley, with an increase in thermal flux and evidence for greater involvement of mantle-derived components in the lead-up to the Bishop Tuff eruption Simon et al.

Thus, in any sample, younger crystals formed in the melt in the immediate lead-up to the eruption will tend to outnumber any older grains, leading to younger average crystal populations and peaks in the PDF curve that are closer to the eruption age than in samples that are just saturated or undersaturated with respect to zircon.

The complexity of the magma storage systems at Okataina, previously recognized from mineralogical and geochemical studies, is reflected in the zircon model-age spectra from the deposits studied here.

Pumices with contrasting mineralogies and compositions in the Rotoiti deposits have different age spectra implying that there was no single melt-dominant body for the caldera-forming event but have similar Sr isotopic characteristics. The rhyolite magma generation zone below Okataina is inferred to be much more heterogeneous than the corresponding volume at Taupo, and there has been no large-scale crystallization thermal event or events comparable with those represented by dominant model-age peaks below Taupo volcano.

Both Okataina and Taupo are at a stage where their post-caldera eruptions represent the generation of small- to moderate-volume magma batches up to 35 km 3 erupted volume from diverse sources, without development of a single coherent magma chamber at either volcano. The University of Auckland Research Committee contributed to the ion-probe costs.

Ilya Bindeman, and two anonymous reviewers are thanked for their helpful comments. Simon Turner is also thanked for editorial handling. Google Scholar. Google Preview. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation.

Volume Article Contents Abstract. Charlier , B. Oxford Academic. Cite Cite B. Select Format Select format. Permissions Icon Permissions. Abstract U—Th disequilibrium model-age data are presented for zircons from four young eruptive units from Okataina volcano, New Zealand.

Open in new tab Download slide. Table 1: Summary of geochemical and isotopic data for the units studied. Sample no. Unit B. Age ka :. Open in new tab. Table 2: Summary of zircon samples analyzed. Eruption unit. Number of. Table 3: Summary of concentration-weighted mean model ages of zircons in the samples analyzed in this study. Age ka. Google Scholar Crossref. Search ADS. On the origin of crystal-poor rhyolites: extracted from batholithic crystal mushes.

Post-caldera volcanism: in situ measurement of U—Pb age and oxygen isotope ratio in Pleistocene zircons from Yellowstone caldera.

Origin and evolution of silicic magmatism at Yellowstone based on ion microbrobe analysis of isotopically zoned zircons. U—Th isotopic constraints on the pre-eruptive dynamics of large-scale silicic volcanism: examples from New Zealand.

Some remarks on U—Th mineral ages from igneous rocks with prolonged crystallisation histories. Methods for the microsampling and high-precision analysis of strontium and rubidium isotopes at single crystal scale for petrological and geochronological applications.

Preliminary assessment of volcanic and hydrothermal hazards in Yellowstone National Park and vicinity. Geochemistry and petrology of the Rotoiti and Earthquake Flat pyroclastic deposits. The petrography of the central North Island rhyolitic lavas. Part 2—regional petrography including notes on associated ash-flow pumice deposits. Magma recharge and crystal mush rejuvenation associated with early post-collapse Upper Basin Member rhyolites, Yellowstone caldera, Wyoming.

Volcanological perspectives on Long Valley, Mammoth Mountain, and Mono Craters: several contiguous but discrete systems. Stratigraphy, dynamics, and eruption impacts of the dual magma Rotorua eruptive episode, Okataina Volcanic Centre, New Zealand.

Basalt triggering of the c. U—Th dating of single zircons from young granitoid xenoliths: new tools for understanding volcanic processes. Extreme U—Th disequilibrium in rift-related basalts, rhyolites and granophyric granite and the timescale of rhyolite generation, intrusion and crystallization at Alid volcanic center, Eritrea.

Berkeley Geochronology Center Special Publication. Residence, resorption and recycling of zircons in Devils Kitchen rhyolite, Coso volcanic field, California. Pre-eruption thermal rejuvenation and stirring of a partly crystalline rhyolite pluton revealed by the Earthquake Flat Pyroclastics deposits, New Zealand. Some studies of the geology, volcanic history, and geothermal resources of the Okataina volcanic centre. Geology of the Okataina Volcanic Centre, scale , Distribution, stratigraphy, and history of proximal deposits from the c.

A discontinuous ca. In situ U—Pb ages of zircons from the Bishop Tuff: no evidence for long crystal residence times. Prolonged residence times for the youngest rhyolites associated with Long Valley caldera: Th— U ion microprobe dating of young zircons.

The petrology of the Rotoiti eruption sequence, Taupo Volcanic Zone: an example of fractionation and mixing in a rhyolitic system. High temperature rhyodacites of the 36 ka Hauparu pyroclastic eruption, Okataina Volcanic Centre, New Zealand: Change in a silicic magmatic system following caldera collapse.

Compositional heterogeneity in tephra deposits resulting from the eruption of multiple magma bodies: implications for tephrochronology. Implications of pre-eruptive magmatic histories of zircons for U—Pb geochronology of silicic extrusions.

Trends in rhyolite geochemistry, mineralogy, and magma storage during the last 50 kyr at Okataina and Taupo volcanic centres, Taupo Volcanic Zone, New Zealand. Geochemistry and magmatic properties of eruption episodes from Haroharo linear vent zone, Okataina Volcanic Centre, New Zealand during the last 10 kyr. Restoration of compositional zonation in the Bandelier silicic magma chamber between two caldera-forming eruptions: geochemistry and origin of the Cerro Toledo Rhyolite, Jemez Mountains, New Mexico.

Phenocryst-poor rhyolites of bimodal tholeiitic provinces: the Rattlesnake Tuff and implications for mush extraction models. An outline geochemistry of rhyolite eruptives from Taupo volcanic centre, New Zealand.

Late Quaternary evolution of a hyperactive rhyolite magmatic system: Taupo volcanic centre, New Zealand. Mechanisms for the generation of compositional heterogeneities in magma chambers. Time scales of magma storage and differentiation of voluminous high-silica rhyolites at Yellowstone caldera, Wyoming. Thermochemical evolution of young rhyolites at Yellowstone: Evidence for a cooling but periodically replenished postcaldera magma reservoir. Zircon saturation revisited: temperature and composition effects in a variety of crustal magma types.

Stratigraphy, chronology, styles and dynamics of late Quaternary eruptions from Taupo volcano, New Zealand. Rapid rates of magma generation from contemporaneous magmatic systems at Taupo volcano, New Zealand: insights from zircon model-age spectra. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals. Issue Section:. Additional details about the 18 September hydrothermal eruption. This report provides more details on the previously reported, small-scale hydrothermal eruption on private property that occurred on 18 September BGVN That report contained an ambiguous statement.

Brad Scott refined the statement that several small-scale hydrothermal eruptions "were reported" in the past year; the passage should have read that such eruptions "have occurred" in the past year.

Scott noted further: "The increase in activity is related to the closure of many geothermal wells within Rotorua City as part of a management scheme designed to preserve the surface geothermal features. Surface features resulting from the eruption can be seen in figure 1. The twisted metal pipes are related to an old bath house, which used to stand near the clothes line mentioned in BGVN The pipes fed water to the bath house and were excavated by the eruption.

The original clothes line was completely removed off site before the eruption occurred. So far, with three or four incidents having occurred, I think that the houses themselves were spared from direct participation in the initial events. With the average craterlet enlarging itself somewhat, there must be a comparable probability that an average sized house would in due course find itself partially overhanging the craterlet.

A search of an index to the Geyser Observation and Study Association GOSA newsletter revealed two articles referring to Rotorua breakouts due to hydrothermal activity see References below. Ashley Cody also discussed Rotorua hydrothermal features Cody, Note that the elevation of Rotorua city is about m; the m stated in the header above refers to the highest point on one of the young domes within the caldera. Rotorua sits in the northern part of the Taupo volcanic zone between Lake Taupo and the Bay of Plenty.

In related hydrothermal activity on Rotorua, the Pohutu Geyser at the active geyser area Whakarewarewa has been in continuous eruption for days, a new and continuing record for New Zealand. Cody, A. VI, p. Scott, B. Hydrothermal eruption on 26 January ejects mud and ballistic blocks. Blocks up to 1 m in diameter were thrown 50 m from the vent, while smaller blocks less than 0. Ejecta reached less than 30 m to the W. The resultant crater had a diameter of m.

Four distinct deposits from the eruption were recognizable on the evening of 26 January. The first unit was a dark gray hydrothermal mud spilt onto an adjacent road W of the vent. This mud appeared to be the pre-eruption contents of Spring A ballistic block bed was the most widely distributed unit, and was composed almost entirely of rocks from the Oranui Formation.

Ballistic blocks were found overlying the mud deposits as well as lower down in the sequence coated by mud with sheltered zones on the leeward sides; this indicated that block ejection was active throughout the eruption. A widespread dark gray mud was deposited SE of the vent with a thickness ranging from mm to only a few millimeters at Ranolf Street. A smaller, slightly darker, gray mud deposit E of the vent, overlayed the prior mud with a maximum thickness of mm.

The main phase of the eruption was inferred to be followed by a smaller mud-rich shower, preceded by distinct ejection of centimeter-sized ballistic blocks that impacted into all of the mud deposits. These blocks extended well beyond the mud NE of the vent, and their relationship to the mud deposits could not be clearly determined.

Mud fallout coated trees and shrubs within the ejecta apron, bending and breaking many of them figure 4. Wilson, C. Two hydrothermal blasts on 6 November send solid material 14 m high. Reported hydrothermal activity at Rotorua on 26 January involved the ejection of mud and ballistic blocks BGVN The New Zealand Institute of Geological and Nuclear Sciences reported that two subsequent hydrothermal eruptions in Rotorua caldera at Kuirau Park on 6 November blasted mud, rock, and ash 14 m into the air.

This compilation of synonyms and subsidiary features may not be comprehensive. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided. The km-wide Rotorua caldera is the NW-most caldera of the Taupo volcanic zone. It is the only single-event caldera in the Taupo Volcanic Zone and was formed about , years ago following eruption of the more than km 3 rhyolitic Mamaku Ignimbrite.

Although caldera collapse occurred in a single event, the process was complex and involved multiple collapse blocks. The major city of Rotorua lies at the south end of the lake that fills much of the caldera. Post-collapse eruptive activity, which ceased during the Pleistocene, was restricted to lava dome extrusion without major explosive activity. The youngest activity consisted of the eruption of three lava domes less than 25, years ago.

The major thermal areas of Takeke, Tikitere, Lake Rotokawa, and Rotorua-Whakarewarewa are located within the caldera or outside its rim, and the city of Rotorua lies within and adjacent to active geothermal fields. The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography.

Monitoring and mapping of hydrogen sulphide emissions across an active geothermal field: Rotorua, New Zealand. Geology , Post-Miocene Volcanoes of the World. The spatial distribution of the geothermal fields in the Taupo volcanic zone, New Zealand.

Bull Volcanol , Mamaku Ignimbrite: a caldera-forming ignimbrite erupted from a compositionally zoned magma chamber in Taupo Volcanic Zone, New Zealand. Structural control of volcanism and caldera development in the transtensional Taupo Volcanic Zone, New Zealand. Caldera volcanism in the Taupo Volcanic Zone. Caldera volcanoes of the Taupo volcanic zone, New Zealand. Res , Hole, J. Maximum lithic size variation shows Rotorua Caldera to be the source of upper Mamaku Ignimbrite.

Gradational contacts between lower, middle, and upper ignimbrite suggest that the ignimbrite was deposited during a single eruptive event from one source. Coexistence of the three pumice types at all stratigraphic levels is further evidence for a single eruptive source.

Variations in lithic content, and coexistence of different pumice types through the ignimbrite stratigraphy, indicate that caldera collapse occurred throughout the eruption, but particularly during the eruption of middle Mamaku Ignimbrite and in later stages of the eruption of upper Mamaku Ignimbrite. Rhyolite domes of Rotorua Caldera can be separated into seven groups, two of which are related to adjacent volcanic centres.

Fragments of rhyolite lava are also a major component of lithic Jag breccias at caldera margin sites. The domes that are related to Rotorua record the eruption of five different rhyolitic magma bodies. The largest rhyolite dome complexes are located around the area of deepest caldera subsidence.

These domes have similar phenocryst assemblages and phenocryst chemistries to silicic Mamaku Ignimbrite pumice clasts suggesting that they are from the same magma. Rhyolite lava fragments in the lag breccias also have similar phenocryst assemblages. All other rhyolite lavas in Rotorua Caldera have different phenocryst assemblages to Mamaku Ignimbrite pumice clasts and are probably not consanguineous with them.

Mokai Ignimbrite outcrops in an 8 km wide east to west band between lakes Taupo and Whakamaru. It has the same unusual paleomagnetic direction as Mamaku Ignimbrite, is the same age, and has similar pumice chemistry. Upper Mokai Ignimbrite is vapour phase altered and has a similar appearance to upper Mamaku Ignimbrite. Three distinct units define Mokai Ignimbrite's stratigraphy, each separated by ash deposits.

Internal variations suggest that Mokai Ignimbrite formed a compound cooling unit. The three flow unit compound cooling unit stratigraphy, phenocryst assemblage of juvenile mafic fragments, presence of mafic blebs at all stratigraphic levels, and thickness of Mokai Ignimbrite suggest that it is distinct from Mamaku Ignimbrite. Rotorua Caldera is described as a rhyolitic, single event, asymmetric, multiple block, single locus caldera on the basis of published geophysical data, caldera geomorphology and geology, location and thickness of Mamaku Ignimbrite and the nature of intracaldera rhyolite domes.