Water exsolution in the magma chamber favors effusive eruptions: Application of Cl-F partitioning behavior at the Nisyros-Yali volcanic area

Popa, Răzvan‐Gabriel; Tollan, Peter; Schenker, Vanessa; Ellis, Ben; Allaz, Julien

doi:10.1016/j.chemgeo.2021.120170

Cited by 20 publications

(18 citation statements)

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“…Determining the dissolved water content of the silicate melt is essential to understand the dynamics of the volcanic eruptions (besides other magmatic volatiles, like CO 2 , S, Cl, and F; Cashman, 2004) and to be able to predict the course of future eruptions based on the physical and chemical properties of the magma including its possible ascent rates (Lloyd et al, 2014;Myers et al, 2019;Popa et al, 2019;Tollan et al, 2019;Allabar et al, 2020). Water content of NAMs can be in equilibrium with the dissolved water content of the melt in each level of the magma storage system, so their water content can be a good proxy to estimate the magmatic water content (Wallace, 2005;Portnyagin et al, 2008;Lloyd et al, 2013;Weis et al, 2015;Tollan et al, 2019;Jollands et al, 2020b). While FTIR is a useful tool to measure the water content of different NAMs as was demonstrated above, calculating magmatic water contents requires the application of a partition coefficient (i.e., the quantitative relation between water content of a given nominally anhydrous phase and the melt; Qin et al, 1992;Rossman, 2003, 2013;Hauri et al, 2006;O'Leary et al, 2010;Lloyd et al, 2016).…”

Section: Implications On the Water Content Of The Host Meltmentioning

confidence: 99%

“…Water content significantly affects the physical properties (density, viscosity) of magma and has a large impact on the magnitude and type of the volcanic eruptions especially by moderating explosivity (Sparks, 1978;Dixon and Stolper, 1995;Dingwell, 1996;Popa et al, 2019Popa et al, , 2020Popa et al, , 2021Allabar et al, 2020). Therefore, it is important to find proxies which allow estimation of the original water content of the magma, and for this reason, investigation of the water content of nominally anhydrous minerals (NAMs hereafter) has come to the forefront of this research.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, it is important to find proxies which allow estimation of the original water content of the magma, and for this reason, investigation of the water content of nominally anhydrous minerals (NAMs hereafter) has come to the forefront of this research. For estimating the original magmatic water content, the commonly used NAMs are clinopyroxene (Weis et al, 2015;Lloyd et al, 2016;Turner et al, 2017), olivine (Portnyagin et al, 2008;Kovács et al, 2010;Barth et al, 2019) and plagioclase Rossman, 2003, 2013;Johnson, 2006;Hamada et al, 2011Hamada et al, , 2013.…”

Section: Introductionmentioning

confidence: 99%

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Uniform “water” content in quartz phenocrysts from silicic pyroclastic fallout deposits – implications on pre-eruptive conditions

et al. 2021

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Abstract. Structural hydroxyl content of volcanic quartz phenocrysts was investigated with unpolarized Fourier-transform infrared spectroscopy. The phenocrysts originated from five pyroclastic fallout deposits from the Bükk Foreland Volcanic Area (BFVA), Hungary, and two from the AD 1314 Kaharoa eruption (KH eruption), Okataina Volcanic Complex (Taupo Volcanic Zone), New Zealand. All investigated quartz populations contain structural hydroxyl content in a narrow range with an average of 9.3 (±1.7) wt ppm. The earlier correlated horizons in the BFVA had the same average structural hydroxyl content (within uncertainty). Thus, it can be concluded that the structural hydroxyl content does not depend on the geographical distance of outcrops of the same units or the temperature or type of the covering deposit. The rare outlier values and similar structural hydroxyl contents show that the fallout horizons cooled fast enough to retain their original structural hydroxyl content. The similarity of the structural hydroxyl contents may be the result of similar P, T, and x (most importantly H2O and the availability of other monovalent cations) conditions in the magmatic plumbing system just before eruption. Therefore, we envisage common physical–chemical conditions, which set the structural hydroxyl content in the quartz phenocrysts and, consequently, the water content of the host magma (∼ 5.5 wt %–7 wt % H2O) in a relatively narrow range close to water saturation.

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Section: Implications On the Water Content Of The Host Meltmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Uniform “water” content in quartz phenocrysts from silicic pyroclastic fallout deposits – implications on pre-eruptive conditions

et al. 2021

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“…F − , OH − , Cl − , and CO 3 2− share the channel anion X site (Pan and Fleet 2002 and references therein). The H 2 O content of apatite has been used in the past (e.g., Zhu and Sverjensky 1991) to estimate H 2 O contents in fluids and melts (Stock et al 2018;Popa et al 2021) and recent studies have also aimed at using CO 2 contents of apatite to gain insight into CO 2 contents of igneous systems (Riker et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Measuring in situ CO2 and H2O in apatite via ATR-FTIR

Hammerli

Hermann

Tollan

et al. 2021

Contrib Mineral Petrol

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We present a new approach to determine in situ CO2 and H2O concentrations in apatite via attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Absolute carbon and hydrogen measurements by nuclear reaction analysis (NRA) and elastic recoil detection (ERD) are used to calibrate ATR-FTIR spectra of CO2 and H2O in apatite. We show that CO2 and H2O contents in apatite can be determined via linear equations (r2 > 0.99) using the integrated area of CO2 and H2O IR absorption bands. The main benefits of this new approach are that ATR-FTIR analyses are non-destructive and can be conducted on polished sample material surfaces with a spatial resolution of ~ 35 μm. Furthermore, the wavenumber of the phosphate IR absorption band can be used to determine the crystallographic orientation of apatite, which allows for accurate quantification of CO2 and H2O in randomly orientated apatite grains. The limit of quantification of H2O in apatite is ~ 400 ppm and ~ 100 ppm for CO2. Via two examples, one from a carbonatite and one from a metasedimentary rock, we show that this new technique opens up new possibilities for determining volatile concentrations and behavior in a wide range of hydrothermal, igneous, and metamorphic systems.

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“…Determination of volatile contents also provides insights into the likely hazards associated with volcanic activity, as volatiles are one of the key controls on eruptive style and explosivity (Sparks 1978;Dixon and Stolper 1995;Dingwell 1996;Popa et al 2020Popa et al , 2021. This chapter presents the results of a study into the volatile contents of both sealed and open-ended, quartzhosted melt inclusions from the earliest-erupted explosive products of eight of the nine Rotorua Subgroup rhyolite events at Ōkataina.…”

Section: Introduction To Magmatic Volatilesmentioning

confidence: 99%

Geochemistry, Magmatic Processes and Timescales of Recent Rhyolitic Eruptives of the Ōkataina Volcanic Centre, Taupō Volcanic Zone, Aotearoa/New Zealand

Elms¹

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This thesis investigates the magmatic processes that operated at Ōkataina volcanic centre prior to and during the rhyolitic events of its most recent eruption sequence, the Rotorua Subgroup (erupted since 25.4 ka), with a specific focus on timescales of human interest. Further context is derived with data from the 52.8 ka Rotoiti (caldera-forming) and Earthquake Flat eruptions, and selected Mangaone Subgroup events that occurred between the 52.8 and 25.4 ka. The regular occurrence of these events provides regular snapshots of the magmatic system over this time period. Whole-rock, glass, and mineral compositional data and timescales modelled from diffusion gradients are compared within geographical and physical volcanological contexts. These data provide a picture of the recent evolution of Ōkataina, shedding light on how quickly the volcano could awaken from its current dormancy to produce a new rhyolitic event, and what that event might be like. Geochemical data from Mangaone Subgroup eruptives show that the post-caldera magmatic system recovered over c. 27 kyr, with increasingly evolved and radiogenic compositions erupted during these events. The post-25.4 ka Rotorua Subgroup shows a more steady evolution, trending towards less radiogenic products towards the present day. Modern Ōkataina comprises three vent clusters, the intra-caldera Mt. Tarawera (formed by the 21.9 ka Ōkareka, 17.5 ka Rerewhakaaitu, 14 ka Waiohau and 1314 AD Kaharoa eruptive episodes) and Haroharo Massif (the 25.2 ka Te Rere, 9.4 ka Rotomā, 7.9 ka Mamaku and 5.5 ka Whakatāne), and the Ōkareka Embayment (the 25.2 ka Te Rere, 15.6 ka Rotorua) on the western edge of the caldera. Most eruptions were geochemically complex, with multiple magmas, some of which were repeated between eruptions. Variations in whole-rock and glass geochemistry are controlled by both the dominant mineral assemblage and external inputs, and relate to the geographical region and timing of when each magma erupted. Each vent region shows evidence for distinct features in its shallower magmatism (i.e. that producing the final-erupted magma compositions), super-imposed on temporal trends controlled by the deeper system. This deeper system beneath Haroharo and Tarawera appears to be more unitary or inter-connected. However, the Ōkareka Embayment is unique in that it appears to involve multiple magmatic systems. Back-scattered electron imaging of orthopyroxenes from the Rotorua, Waiohau and Whakatāne eruptives (and selected plagioclase from the Rotorua), coupled with major-element analyses of the orthopyroxenes, imply that open-system processes are common at Ōkataina, at least in the early stages of eruptible magma body assembly. These processes are reflected in diverse core compositions and complex zonation patterns, narrowing to more uniform rims that are in equilibrium with the compositions of the host melts. Not all cores are in equilibrium with the associated whole-rock compositions, but are in equilibrium with whole-rock compositions from other magmas erupted nearby, further demonstrating open-system crystal exchange and the repeated tapping of some magma sources from one event to another. Melt segregation and magma body assembly takes place over decades up to a century or two, with magma residence times on the order of centuries to millennia, or (if prematurely triggered) as short as months. Priming or triggering events such as heating by basaltic injection (common in the Ōkataina rhyolite eruptions) occur over decades prior to eruption. Quartz-hosted, sealed melt inclusions preserve volatile contents of c. 3-6 wt% H2O and c. 15-125 ppm CO2, with values tending to decrease in younger eruptions, although Waiohau samples have relatively low H2O, and the Rotorua samples have relatively low CO2. Overall, the Ōkataina eruptives have remarkably low CO2 contents compared with international datasets. There are weak correlations between H2O and CO2 contents coexisting in magmas within individual vent regions, but little system-wide coherence due to each region having differing trends (a step-wise drop at Tarawera versus a steady decrease in the young Haroharo eruptions). Scatter in data from sealed melt inclusions, and relatively lower H2O contents in open-ended inclusions (embayments) indicate pre-eruptive volatile losses, driven by crystallisation and/or open-system degassing. The H2O contents of the inner parts of embayments suggest an initial slow decompression at the start of the final magma ascent may also play a minor role. Magma ascent rates are low to moderate (0.1-4.4 m.s-1), with the Ōkareka Embayment eruptives having notably faster ascent rates than those from Tarawera or Haroharo. Both the sealed melt inclusion volatile contents and derived magma ascent rates are similar to those observed or inferred from other silicic eruptions worldwide and are notably comparable to those of super-eruptions, indicating that magma volume and overpressure do not influence ascent rate at eruption onset. Current geophysical observations suggest that a viable magma source currently exists under the southwestern end of Haroharo, and that basaltic diking activity is ongoing in the Ōkataina area. While basaltic eruptions can occur with little warning (e.g. Tarawera, 1886 CE), it is more likely that a future Ōkataina event will be prolonged and rhyolitic. The volcano can rejuvenate into an eruption-ready state within human lifetimes (i.e. decades), and final pre-eruptive warnings from geophysical monitoring could be as short as only a few hours. A new rhyolitic episode could have major impacts, lasting several years and involving both voluminous lavas and widespread fall deposition.

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Water exsolution in the magma chamber favors effusive eruptions: Application of Cl-F partitioning behavior at the Nisyros-Yali volcanic area

Cited by 20 publications

References 91 publications

Uniform “water” content in quartz phenocrysts from silicic pyroclastic fallout deposits – implications on pre-eruptive conditions

Uniform “water” content in quartz phenocrysts from silicic pyroclastic fallout deposits – implications on pre-eruptive conditions

Measuring in situ CO2 and H2O in apatite via ATR-FTIR

Geochemistry, Magmatic Processes and Timescales of Recent Rhyolitic Eruptives of the Ōkataina Volcanic Centre, Taupō Volcanic Zone, Aotearoa/New Zealand

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