Journal of Volcanology and Geothermal Research最新文献

{"title":"Evolution of the eruptive activity at Stromboli (Aeolian Islands - Italy) during the last 4 millennia. A tephrostratigraphic investigation on the early-phase of Recent Stromboli Eruptive Epoch","authors":"G. Re,&nbsp;Di Roberto Alessio,&nbsp;Del Carlo Paola,&nbsp;Pompilio Massimo","doi":"10.1016/j.jvolgeores.2025.108308","DOIUrl":"10.1016/j.jvolgeores.2025.108308","url":null,"abstract":"<div><div>Stromboli is famous for its persistent explosive activity that has been studied from various perspectives over the last century. By contrast, there is controversial information about the volcanic history regarding the period between 6000 years ago and the onset of the present-day activity.</div><div>Here, we present a comprehensive tephrostratigraphic investigation of the pyroclastic sequences that predate the onset of the present-day activity. This study integrates field observations, sedimentological analyses and radiometric ¹⁴C dating, together with detailed textural, petrographic and geochemical characterisation of juvenile clasts. Specifically, we document two superimposed volcaniclastic sequences, Member A and Member B, consisting of sub-conformable pyroclastic beds of lapilli and ash, interspersed with massive epiclastic deposits. While these sequences exhibit similar lithological features, indicating comparable eruptive dynamics, they are distinguishable for glass composition and chronostratigraphic framework.</div><div>In particular, a major change in the glass composition of the magma occurred after 1780 years ago, with a shift from high-K calc-alkaline (HKCA) to shoshonitic (SHO) affinity, composition that still persists in the present-day. We recognise four distinct eruptive periods with HKCA composition within Member A and two eruptive periods with SHO composition within Member B, both predating the onset of the present-day activity. Also, within Member A, we observed the earliest coexistence and mingling of two end-members with different texture and composition. This suggests that the feeding system of Stromboli could have been very similar to the present-day since at least 3200 years ago. It likely comprises two distinct magma bodies at different depths containing magmas with different compositions and porphyritic characteristics that occasionally interact prior to eruptions.</div><div>Our findings contribute to a comprehensive reconstruction of Stromboli's volcanic history and hold practical significance for anticipating and mitigating potential future volcanic events.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"462 ","pages":"Article 108308"},"PeriodicalIF":2.4,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143704582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gravity modeling of a prospective geothermal field of a hot spring in Western Saudi Arabia","authors":"Konstantinos Chavanidis ,&nbsp;Alexandros Stampolidis ,&nbsp;Ahmed Salem ,&nbsp;Abdul Latif Ashadi ,&nbsp;Abid Khogali ,&nbsp;Panagiotis Kirmizakis ,&nbsp;Pantelis Soupios","doi":"10.1016/j.jvolgeores.2025.108307","DOIUrl":"10.1016/j.jvolgeores.2025.108307","url":null,"abstract":"<div><div>The present study focuses on the geothermally prospective area of Wadi Al Lith (Western Saudi Arabia), which is expressed by the presence of hot springs. With a surface temperature that exceeds 80 °C, the Ain Al Harrah hot spring presents the most promising area for geothermal energy production. The Wadi Al Lith prospective geothermal field was generated by tectonic processes involved in the evolution of the Red Sea Rift. A land gravity survey of the area around the hot spring was conducted to develop a comprehensive model of the subsurface. The data were processed using the standard correction methods to construct the Bouguer anomaly map of the area, and the reservoir's 2D and 3D subsurface geometry was estimated. Our analysis revealed low gravity values at the hot spring site and high values in areas where the basement rocks are exposed. The 2D and 3D models were constrained and interpreted using available information from a shallow borehole and other geophysical methods (MT, TEM, and refraction seismic) that have been conducted in the area. The models suggest the possible existence of a geothermal reservoir by highlighting the tectonic structures and the fracture systems that facilitate the transport of thermal fluids to the surface. By reconstructing a detailed subsurface model of the Ain Al Harrah hot spring's surrounding area, the study highlights the potential of the Wadi Al Lith for renewable energy production. An exploratory and production drilling program is suggested, based on the interpretation of the geophysical data.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"461 ","pages":"Article 108307"},"PeriodicalIF":2.4,"publicationDate":"2025-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143549851","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":"Viscosity of bubbly magmas from torsional experiments on pumice","authors":"Gaetano Ferrante ,&nbsp;Helge Gonnermann ,&nbsp;Céline Fliedner ,&nbsp;Thomas Giachetti ,&nbsp;Amy G. Ryan","doi":"10.1016/j.jvolgeores.2025.108297","DOIUrl":"10.1016/j.jvolgeores.2025.108297","url":null,"abstract":"<div><div>Bubbles in magma affect its viscosity, one of the most important properties for modeling volcanic eruptions. We performed new viscosity measurements on rhyolitic magma with bubble volume fractions, <span><math><mi>ϕ</mi></math></span>, between 0.15 and 0.80. Pumice samples from Medicine Lake Volcano, California, were deformed in torsion-compression experiments at a temperature of <span><math><mn>975</mn><msup><mspace></mspace><mo>°</mo></msup><mi>C</mi></math></span>, and strains up to ∼3. Capillary numbers during the experiments were large and viscosity, <span><math><mi>η</mi></math></span>, decreased with increasing <span><math><mi>ϕ</mi></math></span>. The experiments have coherent trends in <span><math><mi>η</mi></math></span> vs. <span><math><mi>ϕ</mi></math></span> with little scatter. We define a new constitutive relation for the relative viscosity of bubbly rhyolitic melt, <span><math><msub><mi>η</mi><mi>r</mi></msub><mo>=</mo><mo>exp</mo><mfenced><mrow><mn>5.5</mn><mspace></mspace><mi>ϕ</mi><mo>/</mo><mfenced><mrow><mn>2</mn><mo>−</mo><mi>ϕ</mi></mrow></mfenced></mrow></mfenced><mo>,</mo></math></span> and for bubbly suspensions at high Capillary numbers in general, reducing the uncertainties associated with scatter among the the body of prior experiments. Our results are useful for more robust modeling of volcanic eruptions.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"461 ","pages":"Article 108297"},"PeriodicalIF":2.4,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143549852","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":"Progressive drying of the hydrothermal system of La Soufrière de Guadeloupe (French West Indies) revealed by multi-year monitoring of chlorine isotopic composition of fumarolic HCl","authors":"Étienne Le Glas ,&nbsp;Magali Bonifacie ,&nbsp;Roberto Moretti ,&nbsp;Vincent Robert ,&nbsp;Pierre Agrinier ,&nbsp;Jabrane Labidi ,&nbsp;Gérard Bardoux ,&nbsp;Laëtitia Pantobe ,&nbsp;Arnaud Burtin ,&nbsp;Élodie Chillin-Eusebe ,&nbsp;Tristan Didier ,&nbsp;Manuel Inostroza","doi":"10.1016/j.jvolgeores.2025.108306","DOIUrl":"10.1016/j.jvolgeores.2025.108306","url":null,"abstract":"<div><div>Closed-conduit volcanoes develop hydrothermal aquifers where infiltrating waters dissolve magmatic gases such as SO₂, HCl, and HF. The extent of this “scrubbing effect” is traditionally tracked using CO₂/SO₂ or CO₂/S_Total, but these ratios can also be modified by secondary processes. Given the high solubility of gaseous HCl_(g) into aqueous water, we assess here chlorine isotopic compositions (δ³⁷Cl) in fumarolic HCl_(g) as a potential quantitative index of scrubbing.</div><div>We present three years and a half (January 2018 to May 2021) of δ³⁷Cl and chlorine concentrations [Cl] data from fumarolic gases at La Soufrière de Guadeloupe, alongside traditional geochemical tracers in volcanology. Our data show strong negative correlation between δ³⁷Cl and [Cl] values, suggesting variable extents of HCl dissolution into the hydrothermal aquifer through time. High δ³⁷Cl values associated to low [Cl] indicate intense ³⁵Cl loss into the aquifer, while low δ³⁷Cl values with high [Cl] likely reflect more pristine magmatic signatures with minimal extents of scrubbing.</div><div>The observed δ³⁷Cl–[Cl] trends suggest Cl isotopic fractionation factors between gas and liquid Δ_g-l varying between +2.5 and +5 ‰. These values are higher than expected at equilibrium, suggesting kinetic fractionations likely resulting from rapid gas flow (preventing isotopic equilibration with liquid water). The fact that comparable δ³⁷Cl–[Cl] trends are found at Poás (Costa Rica) and Vulcano (Italy) suggests that such kinetic fractionations during HCl scrubbing may be widespread.</div><div>Comparisons between δ³⁷Cl and CO₂/CH₄ ratios and the modeled groundwater level within the dome suggest that variations in scrubbing at La Soufrière are primarily driven by varying magmatic inputs. The progressive decrease in δ³⁷Cl, associated with increasing [Cl] from 2019 to 2021, likely reflects long-term aquifer drying, predating the observed rise in fumarolic temperatures above 150 °C in mid-2023.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"462 ","pages":"Article 108306"},"PeriodicalIF":2.4,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143628377","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":"Geological history of Samodiva Mons shield volcano, and surrounding area, Quadrangle V-29, Venus","authors":"D.G. Malyshev ,&nbsp;R.E. Ernst ,&nbsp;H. El Bilali ,&nbsp;M.A. Ivanov ,&nbsp;C.H.G. Braga ,&nbsp;V.E. Rozhin ,&nbsp;A.S. Shimolina","doi":"10.1016/j.jvolgeores.2025.108296","DOIUrl":"10.1016/j.jvolgeores.2025.108296","url":null,"abstract":"<div><div>Samodiva Mons is a large shield volcano (∼240 km in diameter, centered at 13.6° N, 291.0° E) located 1500 km ESE from Beta Regio. Detailed mapping (1:500,000 scale) using radar image and altimetry data from the Magellan mission was used to investigate the geological history of the volcano and its surrounding area. The study area is located in Quadrangle V-29, which extends from 11° to 16° N, 289° to 294° E and covers approximately 291,000 km² of which ∼80,000 km² is occupied by Samodiva Mons volcanic materials. Seven geological units were defined, mapped, and characterized: Samodiva Mons lava flows, small shield volcanoes, coronae material, plains material, tesserae, densely lineated plains, and impact craters. Also, we distinguished two structural units: graben-fissure systems (interpreted as dike swarms) and wrinkle ridges. Three geological stages of evolution of the study region are recognized, with Stages 1–2 being pre-Samodiva Mons and Stage 3 that is associated with Samodiva Mons activity. This stage largely postdates the emplacement of regional plains and was culminated by the formation of the Samodiva Mons volcanic construct.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"461 ","pages":"Article 108296"},"PeriodicalIF":2.4,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143463861","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":"Dynamics of tephra fallout and column collapse during Plinian eruptions of Mt. Pelée volcano (Lesser Antilles): The 2.5 ka cal BCE P5 eruption","authors":"Guillaume Carazzo ,&nbsp;Audrey Michaud-Dubuy ,&nbsp;Vincent Bellier ,&nbsp;Benoit Vittecoq","doi":"10.1016/j.jvolgeores.2025.108295","DOIUrl":"10.1016/j.jvolgeores.2025.108295","url":null,"abstract":"<div><div>Mt. Pelée volcano in Martinique (Lesser Antilles) has undergone volcanic unrest since 2019 and an increase of alert level to yellow (vigilance) in 2020. Historical records and field studies show that this volcano has produced numerous dome-forming and sub-Plinian to Plinian eruptions over the last 25 kyr. The 2.5 ka cal BCE P5 eruption dispersed lapilli and ash across the northern part of Martinique. Here, we present field data on tephra dispersal and grain-size distribution to estimate the eruption source parameters and reconstruct the dynamical evolution of the eruption. Our results show that after a short opening phase, the P5 Plinian eruption formed a 26 km-high stable column with a northeastern dispersal axis. The total volume of the eruption is estimated to be 0.39 ± 0.03 km³ DRE making P5 a VEI 4 event. The mass eruption rate increased from ≈ 1.1 × 10⁸ kg s⁻¹ to ≈ 4.8 × 10⁸ kg s⁻¹ leading to column collapse and the formation of pyroclastic density currents on the flanks of the volcano. The transition from stable column to collapse occurred at conditions well predicted by a 1D model of volcanic plumes and confirms that this eruptive scenario is recurrent at Mt. Pelée volcano over the last 5 kyr. The tephra dispersal of the P5 eruptive products reinforces the accuracy of the current hazard map and provides volcanological constraints to better assess volcanic hazards in the Lesser Antilles.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"461 ","pages":"Article 108295"},"PeriodicalIF":2.4,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143453023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comprehensive orientation method using cross-line laser: A case study of paleomagnetic analysis on pyroclastic deposits from Asama Volcano (Japan)","authors":"Tatsuo Kanamaru ,&nbsp;Kuniyuki Furukawa ,&nbsp;Akari Maki","doi":"10.1016/j.jvolgeores.2025.108293","DOIUrl":"10.1016/j.jvolgeores.2025.108293","url":null,"abstract":"<div><div>Accurate orientation of terrestrial materials is essential in earth sciences, particularly in structural geology and paleomagnetic studies. In this study, we present a novel and versatile sample orientation method utilizing commercially available cross-line lasers. This method address challenges in collecting oriented geological samples caused by factors such as sample size, fragility, rough surfaces, and local magnetic anomalies that complicate the use of magnetic compasses. To evaluate the effectiveness of this method, paleomagnetic measurements were performed on juvenile clasts from pyroclastic density current deposits and the pyroclastic fall deposit of the 1783 eruption of Asama Volcano. The result coincides within error limits with the geomagnetic field predicted by a paleosecular variation curve, demonstrating the potential of our orienting method. However, further experiments are required to quantify the precision of our orienting method and to assess its dependence on factors such as clast size and shape. Preliminary paleomagnetic analyses of the pyroclastic fall deposit suggest a complex emplacement history and indicate a surprisingly high-temperature emplacement. These findings offer new insights into the emplacement processes and thermal history of pyroclastic deposits. This innovative method enhances the capability to collect and analyze oriented geological samples, providing significant contributions to volcanological and structural geological research.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"461 ","pages":"Article 108293"},"PeriodicalIF":2.4,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421907","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":"The spatiotemporal development of downsag and trapdoor structures during caldera subsidence with 1–10 km in diameter in analogue sandbox experiments","authors":"Ryuhei Sanjo ,&nbsp;Toshihiko Sugai","doi":"10.1016/j.jvolgeores.2025.108294","DOIUrl":"10.1016/j.jvolgeores.2025.108294","url":null,"abstract":"<div><div>Calderas are volcanic depressions formed when the roof of a magma chamber collapses due to the depletion of magma within the chamber. Investigating the development of caldera boundary faults that accommodate chamber-roof subsidence is crucial for understanding caldera collapse events and predicting contemporaneous and subsequent volcanic eruptions. Because subsurface structures in natural calderas are difficult to observe, analogue sandbox and numerical experiments, and inversions of geodetic data are often used to reconstruct caldera structures. Recent experimental and analytical studies have revealed localized downsag during the upward propagation of caldera boundary faults and that the fault structures of trapdoor calderas are highly variable. However, how downsag becomes localized during upward boundary fault propagation, and when and why trapdoor structures originate during caldera collapse remain open questions. Here, we performed analogue sandbox experiments in a transparent sandbox and used image analysis techniques to provide insights into these questions. Calderas with 1–10 km in diameter are more favorable than larger ones (tens of kilometers in diameter) for assessing downsagging and trapdoor subsidence, because these volcanic deformations may be masked by crustal deformation due to regional tectonics controlling large caldera subsidence. We therefore focused on calderas with 1–10 km in diameter, and excluded some factors such as pre-existing stress regimes, faults and magma flow, in order to evaluate the development of downsag and trapdoor subsidence themselves. Despite these experimental limitations, our experiments are in agreement with natural calderas and show that as caldera subsidence increases, downsag and trapdoor faulting evolve in four stages. (1) At the beginning of downsag, the horizontal displacement velocity is greatest along the edge of the downsagging region. (2) As the outward-dipping reverse faults nucleate at depth and propagate upward, the peak of horizontal displacement velocity localizes along the surface projection of the concealed faults. (3) Caldera collapse blocks then undergo trapdoor subsidence when the outward-dipping reverse faults reach the surface. (4) Finally, a second episode of trapdoor subsidence of the collapse block occurs when inward-dipping normal faults nucleate beyond the outward-dipping reverse faults. The first and second stages suggest that the existence and location of concealed caldera boundary faults can be predicted from the downsag deformation pattern. The third and fourth stages explain temporal and structural variations observed in trapdoor calderas in the context of caldera boundary fault development. Our model will improve the resolution of caldera structural reconstructions and associated inferences regarding magma chamber dynamics.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"461 ","pages":"Article 108294"},"PeriodicalIF":2.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microearthquakes identification based on convolutional neural networks and clustering techniques","authors":"Fernando Lara ,&nbsp;Román Lara-Cueva ,&nbsp;Felipe Grijalva ,&nbsp;Ana Zambrano","doi":"10.1016/j.jvolgeores.2025.108282","DOIUrl":"10.1016/j.jvolgeores.2025.108282","url":null,"abstract":"<div><div>Microearthquakes are critical for understanding volcanic activity, leading to monitoring many volcanoes worldwide with seismic sensor networks. These networks generate a substantial amount of data, making visual analysis challenging. Consequently, researchers have focused on developing automatic microearthquake recognition systems over the past decades. A primary challenge with these systems is their reliance on labeled databases for training supervised learning models, where the output labels depend on the database labels. We propose using clustering algorithms in conjunction with a Fine-tuned Convolutional Neural Network (CNN) as a feature extractor to identify overlapping microearthquakes, and other types of microearthquakes withoutneeding labeled datasets. This methodology has two stages: The First stage relies on Transfer Learning, to specialize the CNN in microearthquake recognition. The Second stage uses the Fine-tuned CNN as a feature extractor. This methodology is applied to the Cotopaxi Volcano and validated in the Llaima Volcano. It uses unsupervised databases to find clusters of isolated events with similar characteristics to Long Period (LP), Volcano Tectonic (VT), Tremor (TRE), among others. Additionally, it identifies a cluster with overlapping microearthquakes. In the validation stage, 79 % of the VT events are associated to the same cluster without the need to adjust the Fine-tuned CNN. This test is performed on a dataset of a volcano never seen by CNN or Clustering algorithms. Normalized Entropy is used as a metric to verify the generalization of knowledge, the proposed work is compared with Uniform Manifold Approximation and Projection for Dimension Reduction (UMAP). The proposed work obtains 0.04 lower uncertainty with respect to UMAP.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"460 ","pages":"Article 108282"},"PeriodicalIF":2.4,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378816","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":"Development of permeable networks by viscous-brittle deformation in a shallow rhyolite intrusion. Part 2: Microstructural analysis","authors":"Taylor Witcher ,&nbsp;Steffi Burchardt ,&nbsp;Tobias Mattsson ,&nbsp;Michael J. Heap ,&nbsp;Anne Pluymakers ,&nbsp;Kai Li ,&nbsp;Peter Lazor","doi":"10.1016/j.jvolgeores.2025.108278","DOIUrl":"10.1016/j.jvolgeores.2025.108278","url":null,"abstract":"<div><div>Volcanic and magmatic outgassing mechanisms can determine eruptive behavior of shallow silicic magma bodies. Most outgassing mechanisms proposed take place along conduit margins, where the highest strain rates drive ascending magma to brittle failure. However, these mechanisms do not account for outgassing large volumes of magma away from the conduit walls. Here, we present a continuum of porosity preserved in the microcrystalline rhyolitic Sandfell laccolith, Eastern Iceland. Three stages in the continuum are described: porous flow bands, pore channels, and fracture bands. These deformation features are present throughout the entire exposed volume of the Sandfell laccolith in meter-long band geometries, ranging from mm- to dm-scale thickness, and interlayered with coherent, undeformed rhyolite. Using microstructural analytical methods and drawing on the result of previous experimental studies, we show that emplacement-related deformation induced strain partitioning around a crystal content of 45 % that resulted in the segregation of melt-rich and melt-poorer flow bands. Subsequent deformation induced by continued magma emplacement caused strain partitioning in the melt-rich flow bands. Depending on strain rate, different types of deformation features developed, through dilation or porosity redistribution (porous flow bands), cavitation (pore channels), or tensile fracture (fracture bands). Porous flow bands have permeability values ∼4 orders of magnitude higher than undeformed rhyolite. Pore channels and fracture bands have much larger length scales, and so permeability increases dramatically in those systems. Hence, the abundance and interconnectivity of deformation features preserved in the Sandfell laccolith provided an efficient outgassing mechanism for the bulk of the intrusion. Outgassing due to viscous-brittle magma deformation during magma emplacement should therefore be considered for crystal-rich magmas, e.g., during effusive lava dome extrusion.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"461 ","pages":"Article 108278"},"PeriodicalIF":2.4,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}