Fracturing and healing of basaltic magmas during explosive volcanic eruptions

Taddeucci, Jacopo; Cimarelli, C.; Alatorre‐Ibargüengoitia, M. A.; Delgado-Granados, Hugo; Andronico, Daniele; Bello, E. Del; Scarlato, Piergiorgio; Stefano, Flavio Di

doi:10.1038/s41561-021-00708-1

Cited by 27 publications

(18 citation statements)

References 86 publications

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“…6d) may either represent entrained crystals, mixed populations of matrix plagioclase, or be the consequence of fragmentation of the more anorthitic phenocrysts. The latter is consistent with both the fragmented nature of pyroclastic rocks in general (Miwa and Geshi, 2012;Taddeucci et al, 2021) and the wide distributions of phenocryst rims (Fig. 6c), potentially reflecting exposure of mantles and cores in disequilibrium with the matrix glass.…”

Section: Whole Rock-anorthite Decouplingsupporting

confidence: 79%

“…This suggests fragments of phenocrysts are producing these tails and that the modal value of An# rather than the range of its distribution is more representative of the matrix plagioclase chemistry. Potential mechanisms of crystal fracturing include a brittle response to stress perturbations in the magmatic system, melt inclusion decrepitation, bubble expansion or shearing in the conduit (Taddeucci et al, 2021;van Zalinge et al, 2018).…”

Section: Integrating Physical Volcanology and Petrology Using Mineral Zoning Patternsmentioning

confidence: 99%

“…Using the method of Sheldrake and Higgins (2021), we quantify the evolution of textural complexity of plagioclase in time. Using this method, we also measure the degree of crystal fracturing with a new textural parameter (fracture index), which has the potential to provide quantitative information on magma decompression rates (Benage et al, 2021;Miwa and Geshi, 2012;Taddeucci et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

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Quantitative chemical mapping of plagioclase as a tool for the interpretation of volcanic stratigraphy: an example from Saint Kitts, Lesser Antilles

2021

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Establishing a quantitative link between magmatic processes occurring at depth and volcanic eruption dynamics is essential to forecast the future behaviour of volcanoes, and to correctly interpret monitoring signals at active centres. Chemical zoning in minerals, which captures successive events or states within a magmatic system, can be exploited for such a purpose. However, to develop a quantitative understanding of magmatic systems requires an unbiased, reproducible method for characterising zoned crystals. We use image segmentation on thin section scale chemical maps to segment textural zones in plagioclase phenocrysts. These zones are then correlated throughout a stratigraphic sequence from Saint Kitts (Lesser Antilles), composed of a basal pyroclastic flow deposit and a series of fall deposits. Both segmented phenocrysts and unsegmented matrix plagioclase are chemically decoupled from whole rock geochemical trends, with the latter showing a systematic temporal progression towards less chemically evolved magma (more anorthitic plagioclase). By working on a stratigraphic sequence, it is possible to track the chemical and textural complexity of segmented plagioclase in time, in this case on the order of millennia. In doing so, we find a relationship between the number of crystal populations, deposit thickness and time. Thicker deposits contain a larger number of crystal populations, alongside an overall reduction in this number towards the top of the deposit. Our approach provides quantitative textural parameters for volcanic and plutonic rocks, including the ability to measure the amount of crystal fracturing. In combination with mineral chemistry, these parameters can strengthen the link between petrology and volcanology, paving the way towards a deeper understanding of the magmatic processes controlling eruptive dynamics.

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Section: Whole Rock-anorthite Decouplingsupporting

confidence: 79%

Section: Integrating Physical Volcanology and Petrology Using Mineral Zoning Patternsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantitative chemical mapping of plagioclase as a tool for the interpretation of volcanic stratigraphy: an example from Saint Kitts, Lesser Antilles

2021

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“…One is the high phenocryst crystal content of the lavas, which is dominated by plagioclase (> 30 wt%) and the common occurrence and textural variety of glomerocrysts as has also been reported in other systems (e.g., Arculus and Wills 1980;Stamper et al 2014;Holness et al 2019;McIntire et al 2019). Another is the presence of phenocrysts with healed microfractures, likely due to deformation and brittle failure of the magma mush (Bindeman 2005;Holness et al 2019;Taddeucci et al 2021), which would not occur in a liquid-dominated system. The orthopyroxene exsolution lamellae and orthopyroxeneolivine-Fe-Ti oxide peritectic textures suggest prolonged storage at near solidus conditions as can be expected in a crystal-rich system.…”

Section: The Plumbing System and Associated Magmatic Processesmentioning

confidence: 77%

“…In many cases, fractures are "in-filled" which provides evidence for post-fracture "healing" at magmatic conditions. These fractures may result from a range of processes including melt inclusion decrepitation, glomerocryst breakup, flow shearing (Bindeman 2005), and brittle fracturing (Taddeucci et al 2021).…”

Section: Whole-rock Petrographymentioning

confidence: 99%

A petrological and conceptual model of Mayon volcano (Philippines) as an example of an open-vent volcano

Ruth

Costa

2021

Bull Volcanol

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Mayon is a basaltic andesitic, open-vent volcano characterized by persistent passive degassing from the summit at 2463 m above sea level. Mid-size (< 0.1 km3) and mildly explosive eruptions and occasional phreatic eruptions have occurred approximately every 10 years for over a hundred years. Mayon’s plumbing system structure, processes, and time scales driving its eruptions are still not well-known, despite being the most active volcano in the Philippines. We investigated the petrology and geochemistry of its crystal-rich lavas (~ 50 vol% phenocrysts) from nine historical eruptions between 1928 and 2009 and propose a conceptual model of the processes and magmatic architecture that led to the eruptions. The whole-rock geochemistry and mineral assemblage (plagioclase + orthopyroxene + clinopyroxene + Fe-Ti oxide ± olivine) of the lavas have remained remarkably homogenous (54 wt% SiO2, ~ 4 wt% MgO) from 1928 to 2009. However, electron microscope images and microprobe analyses of the phenocrysts and the existence of three types of glomerocrysts testify to a range of magmatic processes, including long-term magma residence, magma mixing, crystallization, volatile fluxing, and degassing. Multiple mineral-melt geothermobarometers suggest a relatively thermally buffered system at 1050 ± 25 °C, with several magma residence zones, ranging from close to the surface, through reservoirs at ~ 4–5 km, and as deep as ~ 20 km. Diffusion chronometry on > 200 orthopyroxene crystals reveal magma mixing timescales that range from a few days to about 65 years, but the majority are shorter than the decadal inter-eruptive repose period. This implies that magma intrusion at Mayon has been nearly continuous over the studied time period, with limited crystal recycling from one eruption to the next. The variety of plagioclase textures and zoning patterns reflect fluxing of volatiles from depth to shallower melts through which they eventually reach the atmosphere through an open conduit. The crystal-rich nature of the erupted magmas may have developed during each inter-eruptive period. We propose that Mayon has behaved over almost 100 years as a steady state system, with limited variations in eruption frequency, degassing flux, magma composition, and crystal content that are mainly determined by the amount and composition of deep magma and volatile input in the system. We explore how Mayon volcano’s processes and working model can be related to other open-vent mafic and water-rich systems such as Etna, Stromboli, Villarrica, or Llaima. Finally, our understanding of open-vent, persistently active volcanoes is rooted in historical observations, but volcano behavior can evolve over longer time frames. We speculate that these volcanoes produce specific plagioclase textures that can be used to identify similar volcanic behavior in the geologic record.

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Shallow magmatic processes revealed by cryptic microantecrysts: a case study from the Taupo Volcanic Zone

Lormand

Zellmer

Sakamoto

et al. 2021

Contrib Mineral Petrol

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Arc magmas typically contain phenocrysts with complex zoning and diverse growth histories. Microlites highlight the same level of intracrystalline variations but require nanoscale resolution which is globally less available. The southern Taupo Volcanic Zone (TVZ), New Zealand, has produced a wide range of explosive eruptions yielding glassy microlite-bearing tephras. Major oxide analyses and textural information reveal that microlite rims are commonly out of equilibrium with the surrounding glass. We mapped microlites and microcrysts at submicron resolution for major and trace element distributions and observed three plagioclase textural patterns: (1) resorption and overgrowth, (2) oscillatory zoning, and (3) normal (sharp) zoning. Pyroxene textures are diverse: (1) resorption and overgrowth, (2) calcium-rich bands, (3) hollow textures, (4) oscillatory zoning, (5) sector zoning, (6) normal zoning and (7) reverse zoning. Microlite chemistry and textures inform processes operating during pre-eruptive magma ascent. They indicate a plumbing system periodically intruded by short-lived sub-aphyric dykes that entrain microantecrysts grown under diverse physico-chemical conditions and stored in rapidly cooled, previously intruded dykes. Changes in temperature gradients between the intrusion and the host rock throughout ascent and repeated magma injections lead to fluctuations in cooling rates and generate local heterogeneities illustrated by the microlite textures and rim compositions. Late-stage degassing occurs at water saturation, forming thin calcic microcryst rims through local partitioning effects. This detailed investigation of textures cryptic to conventional imaging shows that a significant proportion of the micrometre-sized crystal cargo of the TVZ is of antecrystic origin and may not be attributed to late-stage nucleation and growth at the onset of volcanic eruptions, as typically presumed.

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Fracturing and healing of basaltic magmas during explosive volcanic eruptions

Cited by 27 publications

References 86 publications

Quantitative chemical mapping of plagioclase as a tool for the interpretation of volcanic stratigraphy: an example from Saint Kitts, Lesser Antilles

Quantitative chemical mapping of plagioclase as a tool for the interpretation of volcanic stratigraphy: an example from Saint Kitts, Lesser Antilles

A petrological and conceptual model of Mayon volcano (Philippines) as an example of an open-vent volcano

Shallow magmatic processes revealed by cryptic microantecrysts: a case study from the Taupo Volcanic Zone

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