Journal of Volcanology and Geothermal Research最新文献

{"title":"What Triggered the 2021 eruption at Nyiragongo volcano (D.R. Congo)? Unraveling the Complex Interplay between tectonism and magmatism","authors":"Thystere Matondo Bantidi ,&nbsp;Takeshi Nishimura ,&nbsp;Kazuyoshi Nanjo ,&nbsp;Bogdan Enescu ,&nbsp;Takeo Ishibe ,&nbsp;Georges Mavonga Tuluka","doi":"10.1016/j.jvolgeores.2025.108429","DOIUrl":"10.1016/j.jvolgeores.2025.108429","url":null,"abstract":"<div><div>After a 20-year repose, Nyiragongo volcano in the eastern Democratic Republic of the Congo experienced a flank eruption on May 22, 2021, claiming over 30 lives and causing substantial economic loss. Despite extensive studies, the eruption's triggering mechanism remains unclear. In this study, we analyze earthquakes beneath the volcano's summit to examine the <em>b</em>-value variations in the Gutenberg–Richter law, which reflects the ratio of small to large earthquakes and inversely correlates with differential stress. Our goal is to track magma system dynamics leading to the eruption and identify its catalyst. We observe notable differences in <em>b</em>-value estimates during the pre- and <em>syn</em>-eruptive phases. First, the <em>b</em>-value consistently increases over 20 % above the background level (<span><math><msub><mi>b</mi><mi>ref</mi></msub></math></span> = 0.94) for a few days, peaking at 1.55 two days before the eruption, then drops to 59 % below the <span><math><msub><mi>b</mi><mi>ref</mi></msub></math></span> during the eruption. In the six hours following the eruption, <em>b</em>-values fluctuate around 90 % of the <span><math><msub><mi>b</mi><mi>ref</mi></msub></math></span>. These elevated <em>b</em>-values likely reflect the activation of small cracks from the influx of magma in the vicinity of the volcano. Additionally, Coulomb stress changes calculated by combining the epidemic-type aftershock sequence (ETAS) model with the rate-and-state model reveal a stress increase of approximately 10.5 MPa just before the eruption. To address the issue of missing events caused by seismic network density incompleteness and short-term aftershock incompleteness, we created a replenished catalog. Analyzing this catalog, we successfully reproduced <em>b</em>-values, demonstrating its reliability for analyzing volcanic seismicity in regions with sparse networks. Our findings underscore the importance of incorporating systematic <em>b</em>-value time series analysis into regular volcano monitoring programs to improve forecasting capability.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"467 ","pages":"Article 108429"},"PeriodicalIF":2.3,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144864731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracing the pre- to post-eruptive crystallization of trachybasaltic melts: insights into the 1651–1654 CE lavas of Mount Etna (Sicily, Italy)","authors":"G. Lanzafame ,&nbsp;S. Peres ,&nbsp;F. Casetta ,&nbsp;R. Abart ,&nbsp;M. Prašek ,&nbsp;S. Portale ,&nbsp;P.P. Giacomoni ,&nbsp;E. Libowitzky ,&nbsp;C. Ferlito","doi":"10.1016/j.jvolgeores.2025.108416","DOIUrl":"10.1016/j.jvolgeores.2025.108416","url":null,"abstract":"<div><div>Understanding the crystallization of silicate melts is key to reconstructing the processes occurring from magma rising to lava emplacement, the latter representing a major hazard for human settlements during effusive eruptions. Crystal growth, along with melt H₂O degassing, strongly influences lava rheology and surface flow behaviour. This study investigates the pre- to post-eruptive crystallization dynamics of trachybasaltic melts from the 1651–1654 CE eruption on Mount Etna's western flank (Sicily, Italy), one of the 17th century's most significant events due to its duration, lava field extent, and reach into inhabited areas. Investigation on different layers of a fractured pressure ridge allowed to reconstruct the crystallization history of a single flow unit, revealing significant textural differences between the inner and outer (crust) portion of the lava, allowing to quantify the extent of crystallization at subaerial conditions. By combining 2D and 3D textural analyses with chemical and mineralogical investigations, the pre-eruptive pressure-temperature (P–T) conditions of crystal formation were constrained. Phenocrysts nucleated in a vertically extended feeding system (down to 23 km below the sea level) at almost stationary condition of <em>T</em> = 1070–1060 °C. In the glass-rich crust, detailed chemical and textural analyses revealed chemical boundary layers around plagioclase microlites, which was used to model a subaerial growth rate of the outermost plagioclase rim in the order of 0.2–4.5 μm/s. These findings enhance our understanding of lava behaviour during flow, offering key insights for improving hazard models, monitoring, and response during effusive volcanic events similar to the 1651–1654 CE eruption.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"467 ","pages":"Article 108416"},"PeriodicalIF":2.3,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144864729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Degassing, porosity and hydration age characteristics of a giant submarine lava dome: Implications for post-caldera volcanism of the Kikai caldera, Japan","authors":"Iona M. McIntosh ,&nbsp;Morihisa Hamada ,&nbsp;Takeshi Hanyu ,&nbsp;Reina Nakaoka ,&nbsp;Maria Luisa G. Tejada ,&nbsp;Takashi Miyazaki ,&nbsp;Kenta Ueki ,&nbsp;Bogdan S. Vaglarov ,&nbsp;Tomoki Sato ,&nbsp;Satoru Tanaka ,&nbsp;Katsuya Kaneko ,&nbsp;Koji Kiyosugi ,&nbsp;Yojiro Yamamoto ,&nbsp;Keiko Suzuki-Kamata ,&nbsp;Nobukazu Seama ,&nbsp;Yoshiyuki Tatsumi","doi":"10.1016/j.jvolgeores.2025.108427","DOIUrl":"10.1016/j.jvolgeores.2025.108427","url":null,"abstract":"<div><div>The mostly submarine Kikai caldera in SW Japan underwent a caldera-forming eruption at 7.3 ka. Its subsequent post-caldera volcanic activity has included subaerial eruptions whose onland deposits have been well studied, and a historical island-forming eruption from a submarine vent. Marine surveys have also documented a giant, 32 km³ submarine dome that has been emplaced on the caldera floor during the post-caldera period, but the timing and style of its eruption is not known. Here we investigate this giant submarine dome using seafloor observations and rock samples collected during dredging surveys. The dome is covered by large blocks; based on porosity, matrix glass volatile contents and thermal demagnetisation data we infer that these are giant pumice that floated hot at the sea surface prior to sinking. Without suitable radiocarbon material we instead use the extent of secondary hydration of giant pumice matrix glasses to estimate eruption age, yielding an age of 13th Century CE or younger. We infer that the dome grew both endogenously under a thin sediment covering and also via exogenous seafloor lava flow, and that the giant pumice formed from a pumiceous carapace on this lava. We also find preliminary textural evidence that this shallow submarine dome was formed by cryptic fragmentation and pyroclast sintering as is proposed for subaerial silicic lavas. Together our findings suggest that the Kikai caldera has a high average eruption rate in its current post-caldera volcanic stage, and that eruptions, potentially explosive, from submarine vents comprise a significant portion of this activity.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"467 ","pages":"Article 108427"},"PeriodicalIF":2.3,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144879257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lithofacies and juvenile clast variations at Ranu Grati Maar, East Java: Insights into eruptive transitions in monogenetic volcanoes","authors":"Muhammad Andriansyah Gurusinga ,&nbsp;Mirzam Abdurrachman ,&nbsp;Tsukasa Ohba ,&nbsp;Takashi Hoshide ,&nbsp;Wildan Nur Hamzah ,&nbsp;Idham Andri Kurniawan","doi":"10.1016/j.jvolgeores.2025.108426","DOIUrl":"10.1016/j.jvolgeores.2025.108426","url":null,"abstract":"<div><div>Maar-diatremes are valuable archives for understanding phreatomagmatic eruption dynamics and associated hazards. Their stratigraphic records often preserve complex eruptive styles and insights into magmatic conditions prior to eruption. In this study, we integrate detailed lithofacies analysis with petrographic and geochemical investigations of pyroclastic deposits from Ranu Grati Maar, East Java, Indonesia, to reconstruct eruptive transitions and pre-eruptive magmatic conditions. A ∼ 15 m thick tephra succession exposed along the southern and eastern crater rims reveals four distinct stratigraphic units (Units 1–4), differentiated by variations in grain size, componentry, and depositional features. These units record oscillations between phreatomagmatic and magmatic eruptive styles during the eruption. Three juvenile pyroclasts, each scoriaceous (black, gray, and golden), are identified based on textural and color differences. Petrographic and geochemical data indicate that these scoria types share similar bulk compositions and mineral assemblages but display distinct textural variations, including microlite content (∼16.3 % in black scoria vs. ∼9.1–9.6 % in gray and golden scoria), microlite number density, and vesicularity (∼55.5 % in black scoria vs. ∼69.7–71.5 % in gray and golden scoria). These differences suggest that black scoria resided longer in cooler conduit margins, allowing for enhanced microlite crystallization and degassing, whereas gray and golden scoria experienced more rapid ascent and sustained vesiculation in the hotter central conduit zone. Despite their textural diversity, the juvenile clasts from Ranu Grati show minimal geochemical differentiation, indicating that they likely originated from a single magma batch, with heterogeneity driven by dynamic conduit processes rather than complex magmatic evolution. This study demonstrates that eruptive transitions and oscillatory eruption styles in monogenetic systems such as Ranu Grati Maar can be governed by shallow-level magmatic processes (including bubble growth, cooling, and crystallization) without requiring external triggers such as new magma input, aquifer fluctuations, or long-term chamber evolution. These highlight the importance of textural monitoring of pyroclasts for interpreting eruptive conditions and improving hazard assessments, particularly in monogenetic volcanic fields where short-lived eruptions can exhibit abrupt changes in explosivity.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"467 ","pages":"Article 108426"},"PeriodicalIF":2.3,"publicationDate":"2025-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144861147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pre-eruptive conditions of Mid-to-Late Holocene eruptions from Lonquimay Volcanic Complex, Southern Andes of Chile","authors":"Matías Poblete ,&nbsp;Angelo Castruccio ,&nbsp;Patricia Larrea ,&nbsp;Francisco Cáceres ,&nbsp;Jorge Romero ,&nbsp;Oscar Bustamante","doi":"10.1016/j.jvolgeores.2025.108425","DOIUrl":"10.1016/j.jvolgeores.2025.108425","url":null,"abstract":"<div><div>Lonquimay Volcanic Complex (38°22′S, LVC) is one of the most active volcanoes in the Southern Volcanic Zone of the Andes. It comprises a main composite volcano and twelve monogenetic cones, and it has erupted since the Upper Pleistocene. Its latest eruption was in 1988–90 and had catastrophic consequences for the human health and environment. Here we estimated and compared key pre-eruptive conditions (pressure, temperature, dissolved H₂O content and crystallinity) from three of the most well-exposed and widespread fall deposits from the composite volcano, and three lavas of the volcanic complex. Magmas that fed the analysed eruptions were basaltic to trachytic in composition and contained a mineral assemblage of plagioclase±olivine±clinopyroxene and minor Fe<img>Ti oxides and apatite. Evolved units contain unique fayalitic autocrysts (as low as Fo₂₁), which are proposed to have formed in a magma (1) under low pressure, (2) with an evolved composition, (3) a high Fe content, and (4) a reducing state. Based on geochemistry and thermobarometric calculations, we suggest two magma storage zones: (1) a deeper hot and mafic storage region (∼12 km) that host basaltic to basaltic-andesitic magmas at 1083–1151 °C, which undergo tholeiitic mafic injections and (2) a cooler and evolved eruption-feeding magmatic system with a major storage region at 5.6 km with magmas at 869–1046 °C, where fractional crystallisation, magma injections, mingling, and convection took place. Although the same magma injection and mingling triggering-mechanism is suggested for explosive and effusive eruptions, we suggest mingling timescale plays a key role in controlling eruptive style, along with volatile composition and microcryst content.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"467 ","pages":"Article 108425"},"PeriodicalIF":2.3,"publicationDate":"2025-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144831497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ultraviolet and visible remote sensing of volcanic gas emissions","authors":"Christoph Kern","doi":"10.1016/j.jvolgeores.2025.108423","DOIUrl":"10.1016/j.jvolgeores.2025.108423","url":null,"abstract":"<div><div>As magma rises in volcanic systems, volatile species exsolve from the silicate melt and are emitted as gases into the atmosphere. Measuring the magnitude and composition of gas emissions from volcanoes provides insights into processes occurring deep within the Earth and helps constrain the impact of volcanic degassing on atmospheric chemistry. Optical remote sensing techniques allow volcanic gas emissions to be characterized without the need to access hazardous areas near active volcanic vents. This paper reviews the state of the art in ultraviolet and visible volcanic gas remote sensing from the ground, air, and space. Special attention is given to discussing the physics of atmospheric radiative transfer on which these techniques are based. The functionality and limitations of different remote sensing instruments are examined, making clear that the ideal choice of instrumentation will depend on the volcanic system to which it is applied and the sought measurement parameters. Common algorithms for determining trace gas column densities, gas burdens, and volcanic emission rates from measurements of spectral radiance are outlined and compared, showing how some algorithms attempt to model the physics of the measurement while others maximize sensitivity. Several examples demonstrate how remote sensing measurements continue to advance our understanding of volcanic systems and their impact on the atmosphere. Finally, a few promising directions of inquiry are suggested that could lead to improvements in remote sensing instrumentation and analysis techniques. By combining spectroscopic and imaging techniques, improving our understanding of atmospheric radiative transfer, expanding the suite of target gases, and increasing the coverage and frequency of observations, we stand to significantly improve our ability to detect and quantify volcanic gas emissions and gain new insights into important Earth-system processes.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"468 ","pages":"Article 108423"},"PeriodicalIF":2.3,"publicationDate":"2025-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145027754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magmatic evolution and timescales of the Naruko caldera system (NE Honshu): Insight from orthopyroxene and quartz mineral zoning","authors":"Alexey Kotov ,&nbsp;Noriyoshi Tsuchiya ,&nbsp;Satoshi Okumura ,&nbsp;Masao Ban ,&nbsp;Masaoki Uno ,&nbsp;Isoji Miyagi ,&nbsp;Kenji Shimizu ,&nbsp;Takayuki Ushikubo ,&nbsp;Geri Agroli ,&nbsp;Shumpei Yoshimura ,&nbsp;Manzshir Bayarbold","doi":"10.1016/j.jvolgeores.2025.108415","DOIUrl":"10.1016/j.jvolgeores.2025.108415","url":null,"abstract":"<div><div>Silicic magmas from large caldera-forming eruptions often represent crystal-poor melts separated from highly crystalline mush zones under the influence of heat and volatiles. The cascade of magmatic processes from the formation of partially molten crustal zones to the extraction of magma from mush and its interaction with hotter intrusions creates intricate chemical zoning and textures in phenocrysts, reflecting diverse magmatic processes. Understanding the mechanisms and timescales of eruptible magma extraction and storage remains a fundamental challenge in the volcanology. To address this, we present diffusion chronometry from Fe<img>Mg in orthopyroxenes and Ti in quartz from two Pleistocene caldera-forming eruptions at Naruko Caldera, Japan with the Nizaka (73 ka, ∼2.5 km³) and Yanagisawa (45 ka, ∼10 km³) Tuffs. Our findings suggest that both eruptions tapped a broadly similar crustal storage zone, but differences in extraction and localization prior to the eruption influenced the mineral assemblages (e.g., amphibole presence in Yanagisawa but not in Nizaka). Olivine and high-Mg pyroxenes, along with widespread reverse zoning, indicate significant mafic recharge during magma extraction and immediately before eruption. We propose that the Nizaka magma was physically separated from the mush, stored under cooler and less oxidized conditions, and experienced less intrusion by hot magmas, whereas the Yanagisawa magma remained in situ, forming a hotter reservoir that preserved amphibole stability. Despite these differences, the Fe<img>Mg interdiffusion in orthopyroxenes suggests that both magmas were generated within ∼300 years, with peak accumulation rates occurring within ∼30 years of eruption. Ti diffusion in quartz has a shorter timescale (&lt;30 years), capturing only the final stages of crystallization. Our results support the notion that eruptible silicic magmas might be assembled over short timescales prior to eruption regardless of their volume, which is consistent with the results of previous studies.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"467 ","pages":"Article 108415"},"PeriodicalIF":2.3,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144864732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-eruptive transients and fluid flow processes driving volcano-tectonic crises at Vulcano, Italy","authors":"Matteo Lupi ,&nbsp;Salvatore Alparone ,&nbsp;Mimmo Palano ,&nbsp;Andrea Ursino ,&nbsp;Tullio Ricci ,&nbsp;Anthony Finizola ,&nbsp;Douglas Stumpp ,&nbsp;Iván Cabrera-Pérez ,&nbsp;Geneviève Savard","doi":"10.1016/j.jvolgeores.2025.108410","DOIUrl":"10.1016/j.jvolgeores.2025.108410","url":null,"abstract":"<div><div>Although not all volcanic unrests lead to eruptions, it is commonly believed that magma rising through the shallow crust drives volcanic awakening. When eruptions do not occur, hydrothermal activity is often claimed to be responsible for inflation and deflation processes. Yet, a causal process explaining long-lasting non-eruptive unrest is still missing. Vulcano, the southernmost island of the Aeolian volcanic archipelago, Italy, entered in unrest in September 2021. The island experienced intense ground deformation, a sustained increase in fumarole temperatures, gas emissions, and shallow seismicity. CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> diffuse soil degassing increased at the foothill of La Fossa cone, causing the evacuation of inhabitants. Very Long Period (VLP) seismic events with a daily rate of up to 450 events/day were found in the seismic records for the first time since the deployment of the broadband network in 2005. With the benefit of hindsight, new VLPs were also discovered hidden in the 2018 seismic records. Geodetic data show inflation occurring in 2021, suggesting the pressurization of the shallow portion of the magmatic plumbing system beneath Vulcano. A similar behaviour occurred also in 2018. However, a few aspects of these unrests are not fully compatible with traditional causative models invoking a shallow dike emplacement or with a hydrothermal scenario. In particular, the long-lasting transient character of VLPs during 2021–22 has never been encountered before in hydrothermal-driven unrests.</div><div>We propose that deep-seated fluid pressure, possibly promoted by a destabilizing event at depth, either of magmatic or tectonic origin, may have driven the unrests and be responsible for a discrete and transient release of lithostatic fluid pressures from the plumbing system. In particular, NE-striking normal faults highlighted by a high-resolution nodal ambient noise tomography seem to play a key role in modulating the transient character of the 2021 unrest. Once released, overpressure fronts travel across a rheologically complex domain causing VLPs. Once entering the hydrothermal system, fluids (e.g. H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O and CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> dominated mixtures) phase-separate and expand. This pressurizes the shallow plumbing system leading to intense shallow microseismicity. Our model is supported by the long-lasting transient character of the VLP events occurring in swarms and reconciles multiple interdisciplinary observations impacting how we understand the interplay between tectonics, volcanism and natural hazards.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"467 ","pages":"Article 108410"},"PeriodicalIF":2.3,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144861148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis and residence times of trachyte magma at Água de Pau volcano (São Miguel, Island, the Azores): insights from the geochemistry of alkali-feldspars and hosted melt inclusions","authors":"Alessandra Correale ,&nbsp;Vittorio Zanon ,&nbsp;Antonio Paonita","doi":"10.1016/j.jvolgeores.2025.108413","DOIUrl":"10.1016/j.jvolgeores.2025.108413","url":null,"abstract":"<div><div>Major and trace element composition of sanidine and anorthoclase minerals and of the hosted melt inclusions (MI) from two important pumice fallout eruptions (Fogo A and AD1563) of Água de Pau volcano (São Miguel island, Azores) were investigated to define the features of the source feeding the volcano and to fix the timescales of petrogenetic processes previous to these eruptions.</div><div>The major element data in minerals and related MI evidenced that Fogo A magma erupted ∼4500 yr BP at 980 °C and contained on average H₂O = 5.2 wt% whereas the 1563 CE magma erupted at 799 °C and contained H₂O = 4.6 wt%. Also, the variable Rb/Sr (2.86–36.97), Nb/Y (3.52‐7.92) and La/Th (2.32–5.77) in melt inclusions of feldspars highlighted the effect of fractional crystallization of a trachytic magma, which periodically mixed with a more mafic component having a composition comparable to that erupted in Água de Pau. The estimated volume of the mafic magma associated with the Fogo A eruption (∼10 %), is larger than that associated with the 1563 CE event.</div><div>Compositional profiles across feldspars revealed magma ponding times of ∼32 kyr and 6–16 kyr for the Fogo A and the 1563 CE eruptions, respectively. These estimations showed that probably these two volcanic events interested two different portions of the same magmatic system, with the oldest eruption involving a deeper and wider magma volume. This is corroborated by the different magnitudes of the two eruptions. Also, the same magma batch has likely fed both eruptions studied in this work and those strictly preceding.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"467 ","pages":"Article 108413"},"PeriodicalIF":2.3,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144738654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rootless littoral hydrovolcanic explosions and deposits, 6 April 2007, Piton de la Fournaise, La Réunion Island","authors":"Daniele Vergani ,&nbsp;Jocelyn McPhie ,&nbsp;Rebecca Carey ,&nbsp;Andrea Di Muro","doi":"10.1016/j.jvolgeores.2025.108412","DOIUrl":"10.1016/j.jvolgeores.2025.108412","url":null,"abstract":"<div><div>The April 2007 basaltic eruption of Piton de la Fournaise began on 2 April at Piton Tremblet on the eastern flank of the volcano, 7 km from the summit. Vigorous fountains fed aphyric lavas that flowed another 3 km then entered the ocean. During the next few days, the olivine content of the lavas increased and by 5 April, the lavas were oceanite with ∼30 vol% olivine crystals. On 6 April, following a significant increase in lava discharge, spectacular hydrovolcanic explosions occurred where the lava in the main channel entered the ocean. Throughout the day, a sustained steam plume, vertical pyroclastic plumes, base surges and tephra jets were generated by the explosions. The products formed a nested littoral cone at the coast that was partly destroyed and almost entirely covered by subsequent lavas. Although lavas of oceanite composition continued to enter the ocean for the next 24 days, the hydrovolcanic explosions ceased after one day. One 7-m-thick exposure of the littoral cone studied in 2013 comprises bedded, poorly sorted combinations of glassy ash and vesicular lapilli and bombs. Three facies have been identified and interpreted to be deposits from base surges, fall and tephra jets. The explosive lava-water interaction coincided perfectly with a period of elevated discharge at Piton Tremblet on 6 April; the discharge rate subsequently declined. The Piton de la Fournaise 2007 littoral cone resembles historic ‘a‘ā-fed littoral cones on Hawaii. On Piton de la Fournaise, lava entering the ocean at high flow rate or following an increase in discharge ought to be considered potentially hazardous for rootless littoral hydrovolcanic explosions.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108412"},"PeriodicalIF":2.4,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144696877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}