Gennaio 2022

PubAIV Visite: 517
PubAIV 2022
(aggiornamento Gennaio 2022)
TEMATICHE GENERALI:

1) Magmi e sistemi di alimentazione (3 articoli)
2) Dinamiche eruttive e di messa in posto (0 articoli)
3) Geologia e struttura dei vulcani (1 articolo)
4) Monitoraggio, pericolosità e rischio vulcanico (1 articolo)

Tematica 1: Magmi e sistemi di alimentazione
Mangler M.F., Petrone C.M., Prytulak J. (2022)
Magma recharge pattern control eruption styles and magnitudes at Popocatépetl volcano (Mexico).
Geology
https://doi.org/10.1130/G49365.1
Data di pubblicazione: 05/01/2021
PubAIV-ID-00048 - Articolo in Rivista (open access)

Abstract
Diffusion chronometry has produced petrological evidence that magma recharge in mafic to intermediate systems can trigger volcanic eruptions within weeks to months. However, less is known about longer-term recharge frequencies and durations priming magma reservoirs for eruptions. We use Fe-Mg diffusion modeling in orthopyroxene to show that the duration, frequency, and timing of pre-eruptive recharge at Popocatépetl volcano (Mexico) vary systematically with eruption style and magnitude. Effusive eruptions are preceded by 9–13 yr of increased recharge activity, compared to 15–100 yr for explosive eruptions. Explosive eruptions also record a higher number of individual recharge episodes priming the plumbing system. The largest explosive eruptions are further distinguished by an ∼1 yr recharge hiatus directly prior to eruption. Our results offer valuable context for the interpretation of ongoing activity at Popocatépetl, and seeking similar correlations at other arc volcanoes may advance eruption forecasting by including constraints on potential eruption size and style.
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Nardini N., Casetta F., Ickert R.B., Mark D.F., Ntaflos T., Zanetti A., Coltorti M. (2022)
From the Middle Triassic Cima Pape complex (Dolomites; Southern Alps) to the feeding systems beneath active volcanoes: Clues from clinopyroxene textural and compositional zoning.
Journal of Volcanology and Geothermal Research, 107459
https://doi.org/10.1016/j.jvolgeores.2021.107459
Data di pubblicazione: 23/12/2021
PubAIV-ID-00047 - Articolo in Rivista (non-open access)

Abstract
Crystal zoning plays a fundamental role in modern volcanology as a key to unravel the geometry and the dynamics of plumbing systems. In this study, a detailed textural and compositional study of clinopyroxene crystals entrained in intrusive, hypabyssal and effusive products from Cima Pape (Dolomites) is coupled with thermobarometric-hygrometric models to reconstruct the geometry and evolution of the feeding system beneath Middle Triassic volcanic edifices. Whole-rock major, trace element distribution and Sr-Nd isotopic signature (87Sr/86Sri = 0.7045-0.7050; 143Nd/144Ndi = 0.51223-0.51228) show that the rocks from Cima Pape are SiO2-saturated and have shoshonitic affinity, and likely belong to the acme of the Mid-Triassic magmatism that shaped the Southern Alps between 239 and 237.6 Ma. Highly porphyritic trachybasaltic to basaltic trachyandesitic volcanic rocks contain a large number of concentric-zoned clinopyroxene crystals. Here, high-Mg# and -Cr2O3, REE depleted bands (Mg# 80-91; Cr2O3 up to 1.2 wt%) with variable thickness grew between relatively low-Mg# and -Cr2O3 (Mg# 70-77; Cr2O3 conditions of crystallization, occurring at T of 975-1010°C and P comprised between 50 and 150 MPa. Based on the presence of similar zoning in clinopyroxene phenocrysts, a comparison between the Mid-Triassic Cima Pape and active volcanoes was put forward to highlight the potential of studying ancient, entirely exposed volcanic systems for interpreting the feeding system processes acting beneath active volcanoes. At a regional scale, this approach represents a new, powerful tool for investigating the evolution of the Mid-Triassic magmatism in the Southern Alps and shedding light on the interactions between mantle-derived melts and differentiated batches ponding in the crust.
Tommasini S., Bindi L., Savia L., Mangler M.F., Orlando A., Petrone C.M. (2022)
Critical assessment of pressure estimates in volcanic plumbing systems: the case study of Popocatépetl volcano, Mexico.
Lithos, 408-409, 106540
https://doi.org/10.1016/j.lithos.2021.106540
Data di pubblicazione: 28/12/2021
PubAIV-ID-00045 - Articolo in Rivista (non-open access)

Abstract
Most geobarometers use chemical compositions of minerals and their host melt to estimate crystallization pressures. Crystal structural parameters such as cell and site volumes are not usually considered despite their known sensitivity to pressure. Here, we compare two clinopyroxene geobarometers based upon electron microprobe analysis alone and coupled with single-crystal X-ray diffraction data. The case study is the plumbing system of Popocatépetl volcano (Mexico), which consists of three distinct magma reservoirs in upper, middle and lower crustal depths, represented by three compositionally and texturally distinct clinopyroxene populations (T1, Mg# core 82, and low-Ca with a lower wollastonite component). These clinopyroxenes are augites of limited compositional variability, although yielding a significant increase in cell (V cell) and M1 site (V M1) volumes from low-Ca and T2 core clinopyroxenes to T1 (core and rim) and T2 (rim) clinopyroxenes. This variation is not due to chemical or temperature effects but is linked to their depth of crystallization. The application of the geobarometer based on chemical composition alone is unable to distinguish the three different reservoirs postulated on volcanological and petrological grounds. In contrast, the application of the geobarometer based on both structural parameters and chemical composition yields a remarkable correlation between the calculated cell volume and the estimated depth of crystallization of the different clinopyroxenes, including core to rim differences.

These results have twofold implications. First, the determination of the structural parameters of clinopyroxenes is the only method to resolve the actual distribution of Mg, Fe2+, Fe3+ in the M1 and M2 structural sites and, given the sensitivity of cell and site volumes to pressure, permits to improve geobarometric estimates in volcanic plumbing systems. Second, the quantitative determination of the crystallization depth of the different clinopyroxenes has permitted to rescale the depth of the three different reservoirs in the plumbing system of the Popocatépetl Volcanic Complex located from ~30 km b.s.l. (low-Ca clinopyroxene) to ~18 km b.s.l. (T2 clinopyroxene core) and ~10–0 km b.s.l. (T1 clinopyroxene core and rim, T2 clinopyroxene rim) within the crustal structure of the Morelos platform. This provides further support to the complex plumbing system of the Popocatépetl Volcanic Complex consisting of polybaric storage layers of variable interconnected and interacting transient magma reservoirs.
Tematica 2: Dinamiche eruttive e di messa in posto
Tematica 3: Geologia e struttura dei vulcani
Malaguti A., Rosi M., Pistolesi M., Speranza F., Menzies M. (2021)
The contribution of palaeomagnetism, tephrochronology and radiocarbon dating to refine the last 1100 years of eruptive activity at Vulcano (Italy).
Bullettin of Volcanology, 84(12), 1-19
https://doi.org/10.1007/s00445-021-01515-7
Data di pubblicazione: 01/01/2022
PubAIV-ID-00046 - Articolo in Rivista (non-open access)

Abstract
During the past millennia, several eruptions have occurred within the La Fossa caldera on the island of Vulcano (Aeolian Islands, Italy), some being also described in historical documents dating back to Republican Roman times (first to second century BC). The absolute and relative timing of such activity, however, has remained poorly defined and controversial, due to contrasting ages provided by radiometric and unconventional palaeomagnetic methods. Here, we present a detailed recon- struction of the eruptive history focused on the ninth to fifteenth century AD period that occurred at both La Fossa cone and Vulcanello. This integrated approach involves tephrostratigraphy, standard palaeomagnetic methodology and radiocarbon dating. The new dataset confirms that the lavas exposed above sea level at Vulcanello were erupted between the tenth and eleventh century AD, and not between the first and second century BC as previously suggested. In this same time interval, La Fossa cone was characterized by long-lasting, shoshonitic, explosive activity followed by a discrete, sustained, rhyolitic explosive eruption. Between AD 1050 and 1300, activity was focused only on La Fossa cone, with alternating explosive and effusive eruptions that emplaced four rhyolitic and trachytic lava flows, resulting in significant growth of the cone. After the violent, phreatic event of the Breccia di Commenda (thirteenth century), the eruption continued with a substantial, long- lasting emission of fine ash until activity ceased. Magmatic explosive activity resumed at La Fossa cone at the beginning of the fifteenth century marking the onset of the Gran Cratere cycle. This phase lasted until the mid-sixteenth century and produced at least seven explosive eruptions of intermediate magma composition and a couple of lateral explosions (Forgia Vecchia I and II). During this time interval, a third cinder cone was emplaced at Vulcanello, and the activity produced the lava flows of Punta del Roveto and Valle dei Mostri. From the seventeenth to twentieth centuries, volcanic activity was concentrated at La Fossa cone, where it ended in 1890. This work confirms that Vulcanello island formed in Medieval times between the tenth and eleventh centuries. Moreover, between the tenth and mid-sixteenth centuries, La Fossa caldera was the site of at least 19 eruptions with an average eruption rate of one event every 34 years. This rate makes volcanic hazard at Vulcano higher than that suggested to date.
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Tematica 4: Monitoraggio, pericolosità e rischio vulcanico
Massaro S., Rossi E., Sandri L., Bonadonna C., Selva J., Moretti R., Komorowski J-C. (2022)
Assessing hazard and potential impact associated with volcanic ballistic projectiles: The example of La Soufrière de Guadeloupe volcano (Lesser Antilles).
Journal of Volcanology and Geothermal Research 421, 107453
https://doi.org/10.1016/j.jvolgeores.2021.107453
Data di pubblicazione: 13/12/2021
PubAIV-ID-00049 - Articolo in Rivista (open access)

Abstract
The fallout of ballistic blocks and bombs ejected from eruptive vents has the potential to produce severe injuries to people and damage to infrastructure in areas proximal to volcanoes. The dimensions and dispersions of ballis- tic ejecta from explosive eruptions are pivotal parameters to forecast the potential impact associated with future eruptions based on the compilation of probabilistic hazard maps.
In this study, we propose a new probabilistic hazard quantification strategy to provide the probability of Volcanic Ballistic Projectiles (VBPs) to exceed some critical kinetic energy thresholds, considering a variability on the site of the eruptive vents and the effect of wind. La Soufrière de Guadeloupe (Lesser Antilles) is chosen as a test case, fo- cussing on the most likely explosive scenario associated with the eruption of an active lava dome (including phreatic, Vulcanian and Strombolian eruptions). Sensitivity analyses have guided the optimization of input param- eters to balance the results stability and computational costs, showing that the topography is a pivotal factor when accounting for the spatial uncertainty on vent locations in the proximity of the dome area. Given an eruption within the adopted scenario, we provide maps showing the probability to exceed different energy reference thresholds for roof's perforation if at least one VBP falls in a target area. These maps are then combined with exposed elements to produce a qualitative exposure-based risk map. We compute the overall probability, conditional on the selected scenario, for roof perforation in a given area when a VBP is ejected. Results show probabilities varying from ca. 2% up to 40% within a few km from the volcano, quickly dropping away from the dome. However, when the prob- ability to exceed the energy reference threshold is only conditional on falling of VBPs in a target area, most of Basse- Terre island would be affected by the 20–60% probability of roof perforation. This work confirms how the choice of a probabilistic approach is key to estimate the likelihood of occurrence of VBPs impacts as a first step towards the development and implementation of pro–active risk reduction strategies in volcanic areas.
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