6 results on '"Charlier, Bruce"'
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2. The compositional diversity and temporal evolution of an active andesitic arc stratovolcano: Tongariro, Taupō Volcanic Zone, New Zealand.
- Author
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Pure, Leo R., Wilson, Colin J. N., Charlier, Bruce L. A., Gamble, John A., Townsend, Dougal B., and Leonard, Graham S.
- Subjects
MAGMAS ,CRYSTALLIZATION ,VOLCANOES ,HOLOCENE Epoch ,ZIRCON ,DACITE - Abstract
New geochemical data, including Sr–Nd–Pb isotopes for whole-rock and groundmass samples, are reported for edifice-forming eruptives at Tongariro volcano, New Zealand, which span its ~ 350 ka to late Holocene history. Tongariro eruptives are medium-K basaltic-andesites to dacites (53.0–66.2 wt% SiO
2 ) that evolved via assimilation-fractional crystallisation (AFC) processes partly or mostly in the uppermost 15 km of the crust. When ordered chronologically using a high-resolution40 Ar/39 Ar-dated eruptive stratigraphy, the compositional data show systematic 10–130 kyr cycles. Mafic replenishment events inferred from MgO values occurred at ~ 230, ~ 151, ~ 88 and ~ 56 ka and in the late Holocene, with high-MgO flank vents erupting at ~ 160, ~ 117, ~ 35 and ~ 17.5 ka. Cycles in Sm/Nd,87 Sr/86 Sr,143 Nd/144 Nd and Pb isotopic ratios, which are decoupled from MgO, K2 O and Rb/Sr cycles, indicate periods of prolonged crustal residence of magmas from ~ 230 to ~ 100 ka and ~ 95 to ~ 30 ka. AFC modelling shows that intermediate and silicic melt compositions, with r-values between 0.1 and 1, are needed to reproduce Tongariro compositional arrays. AFC models also indicate that ~ 20% of the average Tongariro magma comprises assimilated (meta)sedimentary basement material. Locally, Tongariro and adjacent Ruapehu volcanoes attain their most crust-like87 Sr/86 Sr and143 Nd/144 Nd compositions at ~ 100 and ~ 30 ka, paralleling with zircon model-age crystallisation modes at the rhyolitic Taupō volcano ~ 50 km to the NNE. These coincidences suggest that the timing and tempo of magma assembly processes at all three volcanoes were contemporaneous and may have been tectonically influenced since at least 200 ka. [ABSTRACT FROM AUTHOR]- Published
- 2023
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3. A sulfur and halogen budget for the large magmatic system beneath Taupō volcano.
- Author
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Sharpe, Max S., Barker, Simon J., Rooyakkers, Shane M., Wilson, Colin J. N., Chambefort, Isabelle, Rowe, Michael C., Schipper, C. Ian, and Charlier, Bruce L. A.
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SULFUR ,GOLD ores ,VOLCANIC eruptions ,HALOGENS ,OZONE layer ,PYRRHOTITE ,ICE cores ,VOLCANOES - Abstract
The transport and degassing pathways of volatiles through large silicic magmatic systems are central to understanding geothermal fluid compositions, ore deposit genesis, and volcanic eruption dynamics and impacts. Here, we document sulfur (S), chlorine (Cl), and fluorine (F) concentrations in a range of host materials in eruptive deposits from Taupō volcano (New Zealand). Materials analysed are groundmass glass, silicic melt inclusions, and microphenocrystic apatite that equilibrated in shallow melt-dominant magma bodies; silicic melt and apatite inclusions within crystal cores inferred to be sourced from deeper crystal mush; and olivine-hosted basaltic melt inclusions from mafic enclaves that represent the most primitive feedstock magmas. Sulfur and halogen concentrations each follow distinct concentration pathways during magma differentiation in response to changing pressures, temperatures, oxygen fugacities, crystallising mineral phases, the effects of volatile saturation, and the presence of an aqueous fluid phase. Sulfur contents in the basaltic melt inclusions (~ 2000 ppm) are typical for arc-type magmas, but drop to near detection limits by dacitic compositions, reflecting pyrrhotite crystallisation at ~ 60 wt. % SiO
2 during the onset of magnetite crystallisation. In contrast, Cl increases from ~ 500 ppm in basalts to ~ 2500 ppm in dacitic compositions, due to incompatibility in the crystallising phases. Fluorine contents are similar between mafic and silicic compositions (< 1200 ppm) and are primarily controlled by the onset of apatite and/or amphibole crystallisation and then destabilisation. Sulfur and Cl partition strongly into an aqueous fluid and/or vapour phase in the shallow silicic system. Sulfur contents in the rhyolite melts are low, yet the Oruanui supereruption is associated with a major sulfate peak in ice core records in Antarctica and Greenland, implying that excess S was derived from a pre-eruptive gas phase, mafic magma recharge, and/or disintegration of a hydrothermal system. We estimate that the 25.5 ka Oruanui eruption ejected > 130 Tg of S (390 Tg sulfate) and up to ~ 1800 Tg of Cl, with potentially global impacts on climate and stratospheric ozone. [ABSTRACT FROM AUTHOR]- Published
- 2022
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4. Taupō: an overview of New Zealand's youngest supervolcano.
- Author
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Barker, Simon J., Wilson, Colin J.N., Illsley-Kemp, Finnigan, Leonard, Graham S., Mestel, Eleanor R.H., Mauriohooho, Kate, and Charlier, Bruce L.A.
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RHYOLITE ,VOLCANOES ,MAGMAS ,CALDERAS ,LANDSCAPES - Abstract
Taupō volcano (New Zealand) is distinguished as the source of Earth's youngest supereruption (∼25.5 ka), with Lake Taupō occupying the resulting caldera. Taupō has also produced eruptions of a wide variety of sizes, styles and associated landscape responses over a ∼350 kyr period. Early Taupō (>54 ka) is poorly demarcated, merging with Maroa to the north, and is represented by widely scattered, geochemically distinct, effusive domes and explosive eruption products from vents all around the modern lake. Taupō had two independent magmatic systems from 54–25.5 ka, one that led to the Oruanui event focussed beneath the area of the modern lake and a second, northeast of the lake that has remained active to the present. Following the Oruanui supereruption, the rebuilt modern hyperactive Taupō magmatic system is primarily focussed beneath the lake and has generated 25 rhyolitic eruptions since ∼12 ka. The young rhyolite magmas come from an evolving silicic magma reservoir, but vary widely in their eruptive sizes and destructive potential. In the modern era Taupō experiences unrest every decade or so, but uncertainties remain over the nature of the magma reservoir and the processes that drive unrest or eruptive activity that require new geophysical data and interpretations. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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5. Crystallisation ages in coeval silicic magma bodies: 238U–230Th disequilibrium evidence from the Rotoiti and Earthquake Flat eruption deposits, Taupo Volcanic Zone, New Zealand
- Author
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Charlier, Bruce L.A., Peate, David W., Wilson, Colin J.N., Lowenstern, Jacob B., Storey, Michael, and Brown, Stuart J.A.
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RHYOLITE , *ZIRCON , *VOLCANOES - Abstract
The timescales over which moderate to large bodies of silicic magma are generated and stored are addressed here by studies of two geographically adjacent, successive eruption deposits in the Taupo Volcanic Zone, New Zealand. The earlier, caldera-forming Rotoiti eruption (>100 km3 magma) at Okataina volcano was followed, within months at most, by the Earthquake Flat eruption (∼10 km3 magma) from nearby Kapenga volcano; both generated non-welded ignimbrite and coeval widespread fall deposits. The Rotoiti and Earthquake Flat deposits are both crystal-rich high-silica rhyolites, with sparse glass-bearing granitoid fragments also occurring in Rotoiti lag breccias generated during caldera collapse. Here we report 238U–230Th disequilibrium data on whole rocks and mineral separates from representative Rotoiti and Earthquake Flat pumices and the co-eruptive Rotoiti granitoid fragments using TIMS and in situ zircon analyses by SIMS. Multiple-grain zircon-controlled crystallisation ages measured by TIMS from the Rotoiti pumice range from 69±3 ka (<63 μm size fraction) to 76±6 (125–250 μm fraction), with a weighted mean of all size fractions of 71±2 ka. SIMS model ages from single zircons in pumice range from 50±24 ka to >350 ka, with a pronounced peak at 70–90 ka. The weighted mean of isochrons is 83±14 ka, in accord with the TIMS data. One glass-bearing Rotoiti granitoid clast yielded an age of 57±8 ka by TIMS (controlled by Th-rich phases that, however, are not apparently present in the juvenile pumices). Another glass-bearing Rotoiti granitoid yielded SIMS zircon model ages peaking at 60–90 ka, having a similar age distribution to the pumice. Age data from pumices are consistent with a published 64±4 ka eruptive age (now modified to 62±2 ka), but chemical and/or mineralogical data imply that the granitoid lithics are not largely crystalline Rotoiti rhyolite, but instead represent contemporaneous partly molten intrusions reflecting different sources in their chemistries and mineralogies. Similarly, although the Earthquake Flat eruption immediately followed (and probably was triggered by) the Rotoiti event, age data from juvenile material are significantly different. A multiple-grain zircon-controlled crystallisation age measured by TIMS from a representative pumice is 173±5 ka, while SIMS model ages range from 70−26+34 ka to >350 ka, with a peak at 105 ka. These age data coupled with previously published geochemical and isotopic data show that the Rotoiti and Earthquake Flat deposits were erupted from independent, unconnected magma bodies. [Copyright &y& Elsevier]
- Published
- 2003
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6. Processes and timescales of magmatic rejuvenation and residence prior to post-caldera rhyolitic eruptions: Ōkataina Volcanic Centre, Aotearoa New Zealand.
- Author
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Elms, Hannah C., Barker, Simon J., Morgan, Daniel J., Wilson, Colin J.N., and Charlier, Bruce L.A.
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VOLCANIC eruptions , *ORTHOPYROXENE , *RHYOLITE , *MINERALOGY , *MAGMAS , *VOLCANOES - Abstract
Understanding the timescales and processes through which magma bodies form and develop in the crust prior to eruption is vital for volcanic monitoring and interpreting future unrest signals, particularly at caldera volcanoes. Here we present the results of a case study on Ōkataina Volcanic Centre, New Zealand, into the timescales of pre-eruptive processes operating during young intra-caldera eruptions, using Fe-Mg interdiffusion profiles in orthopyroxene. Three eruptions covering the three different vent regions, the 15.6 ka Rotorua episode from the Ōkareka Embayment, the 14.0 ka Waiohau episode from Tarawera, and the 5.5 ka Whakatāne episode from Haroharo have broadly similar rhyolitic compositions but show distinctions in their mineralogy and crystal zoning profiles. Back-scattered electron imaging coupled with major-element analyses of orthopyroxene cores and rims imply that open-system mixing and disequilibrium is a common process in the early stages of magma assembly at Ōkataina. Through interpreting mineral chemistry and zoning patterns, we infer that melt segregation, magma body assembly from the source mush and residence in the upper crust takes place on the order of decades up to several centuries, or (if prematurely triggered) as short as months. Priming events such as heating by basaltic injection (common in the Ōkataina rhyolite eruptions) occur over decades prior to eruption. Our findings highlight that multiple processes can dictate the assembly, residence and eruption of melt bodies from the crust and that most magmatic processes occur over timescales that are short enough to be directly relevant to geophysical imaging of magma reservoirs and monitoring initiatives. • Fe-Mg diffusion modelling in orthopyroxenes can indicate the timescales of the pre-eruptive processes driving rhyolitic eruptions. • At Ōkataina, these processes occur on decadal to centennial timescales. • No systematic relationship exists between pre-eruptive timescales and eruption size. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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