Journal of Volcanology and Geothermal Research最新文献

{"title":"Magmatic evolution of basaltic rear-arc monogenetic volcanism in southern Colombia","authors":"Ana Toro , Hugo Murcia , Laura Sánchez-Torres","doi":"10.1016/j.jvolgeores.2025.108312","DOIUrl":"10.1016/j.jvolgeores.2025.108312","url":null,"abstract":"<div><div>The Guamuez-Sibundoy Monogenetic Volcanic Field is located in the Southern Volcanic Segment of the Central Cordillera of Colombia. The field hosts 19 volcanoes, including scoria cones, maars and lava domes. This volcanism is part of the volcanic arc related to the interaction between the Nazca and South American plates. This interaction has led to a transtensional tectonic environment represented by pull-apart basins linked to the so-called Algeciras Fault System. This study integrates different techniques including field geology, petrography, mineral chemistry, whole-rock chemistry and geothermobarometric analysis in order to know the compositional characteristics and reconstruct the evolution of the magmas that gave rise to several volcanoes in the field: Guayapungo, Yaku, Mujundinoy Sur and Fuisanoy volcanoes. This study is the starting point to understand the possible future activity in the field. The eruptive products associated with these volcanoes correspond to concentrated and dilute pyroclastic density currents and lava flows, the latter predominating throughout the field. Petrographically, all the studied rocks are porphyritic, with olivine (Fo<sub>71–90</sub>), clinopyroxene (Wo<sub>33–48</sub>, En<sub>36–54</sub>, Fe<sub>7–16</sub>), orthopyroxene (Wo<sub>3–5</sub>, En<sub>68–71</sub>, Fe<sub>24–28</sub>), plagioclase (An<sub>26–82</sub>), amphibole (magnesiohastingsite and tschermakite) and Fe-Ti oxides as mineral phases embedded in a microcrystalline, cryptocrystalline and glassy groundmass. They present glomeroporphyritic texture in olivine and pyroxene, zoning in plagioclase, skeletal in olivine and pyroxene, and spinifex-like texture in pyroxene. Fluidal and serial textures are also common. Fe-Ti oxides are present as a minor phase in all volcanoes. Chemically, the volcanoes are basaltic and basaltic andesite in composition and display calc-alkaline affinity, typical of subduction environments. Geothermobarometric analyses indicate that the crystallisation conditions for olivine were 1188–1137 °C, for clinopyroxene 1199–1015 °C and 1.7–0.2 GPa and for plagioclase 1127–1077 °C and 0.6–0.2 GPa. The analyses indicate that the magmas share a common origin at the asthenosphere-lithosphere boundary and that fractional crystallisation was the most important magmatic evolution process during the magma ascent. The crystallisation conditions of the mineral phases indicate olivine, followed by clinopyroxene, as the first to start forming at the mantle-crust boundary (64–7 km), while plagioclase crystallised only at cortical levels (24–7 km). Chemical data and crystallisation conditions indicate that the Guayapungo volcano ascended directly from the mantle and experienced a rapid ascent from 15 km to the surface. The lack of crystallisation, in addition to the presence of amphibole xenocrysts, indicates that the Yaku and Mujundinoy Sur magmas experienced mild assimilation. Crystallisation conditions and further evolution at Fuisano","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"462 ","pages":"Article 108312"},"PeriodicalIF":2.4,"publicationDate":"2025-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143637070","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 characterization and geochemical alteration pathways of drill core from the Humu'ula Groundwater Research Project, Hawaii, USA: I. Pohakuloa Training Area","authors":"Pooja Sheevam,&nbsp;Wendy M. Calvin","doi":"10.1016/j.jvolgeores.2025.108311","DOIUrl":"10.1016/j.jvolgeores.2025.108311","url":null,"abstract":"<div><div>Scientific analysis of the PTA-2 drill core focuses on the investigation of mafic mineralogy through long-wave infrared (LWIR) spectroscopy, laboratory scanning electron microscopy with energy-dispersive spectroscopy (SEM EDS), and bulk X-ray fluorescence (XRF) geochemical analysis. We performed both LWIR and short-wave infrared (SWIR) imaging of thin sections and cut sections at high spatial resolution. These analyses complement prior work and provide additional information in order to understand the mineralogical transformations and geochemical processes that have occurred in the subsurface. LWIR spectroscopy allowed us to quantify specific mineral phases prevalent in shield phase basalts – which are largely comprised of Ca-feldspars, pyroxenes, and olivine. Collected spectra also showed the influence of alteration components on the spectral signatures. New analyses using SEM EDS and bulk XRF geochemistry, augment the spectroscopy and offer valuable insights into the mineralogy and fluid-rock interactions. Petrographic images confirmed the varying mineral textures of basalt, ranging from fine-grained, to more prominent phenocrysts in the form of olivine cumulates. Data acquired from whole rock geochemistry was instrumental in determining fluid-rock interactions by showing that elemental components are not lost with alteration. This study provides the first comprehensive analysis of subsurface drill core away from active margins, and a foundation for further subsurface core logging and research.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"462 ","pages":"Article 108311"},"PeriodicalIF":2.4,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682323","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":"A comparison of volcanic ash source term characteristics estimated by source inversion and plume rise modelling methods: Raikoke 2019","authors":"Natalie J. Harvey ,&nbsp;Michael Herzog ,&nbsp;Helen F. Dacre ,&nbsp;Helen N. Webster","doi":"10.1016/j.jvolgeores.2025.108304","DOIUrl":"10.1016/j.jvolgeores.2025.108304","url":null,"abstract":"<div><div>Predictions of volcanic ash location and concentration following an eruption rely heavily on estimates of source term characteristics including mass eruption rate, vertical distribution of ash and particle size distribution. These characteristics can be provided by several methods including (i) preset values based on historical data, (ii) near-source plume rise model simulations, (iii) a combination of satellite retrievals and long-range dispersion model simulations (known as source inversion). For the first time, this study presents a comparison of source term characteristics from these different methods. The study focuses on the 2019 Raikoke eruption and analysis of the volcanic ash cloud 150 km downwind from the volcano vent, representing an effective source term for the dispersion of ash in the distal volcanic cloud. Results indicate good agreement in the vertical distribution of ash between the plume rise and source inversion methods but large differences in estimates of the horizontal mass flux at this distance. The plume rise model demonstrates the rapid sedimentation and deposition of coarse (<span><math><mo>&gt;</mo><mn>100</mn><mi>μ</mi><mi>m</mi></math></span> diameter) ash particles close to the volcano vent resulting in a particle size distribution comparable to the preset distribution used operationally by the London VAAC at this range. These results suggest that source inversion can provide a computationally cheaper alternative to the 3D plume rise method for estimating the vertical distribution of ash, and that the assumption of near-source fallout of coarse particles in the preset particle size distribution holds fairly well. Further investigations are recommended including particle aggregation effects to understand differences in estimates of the effective mass eruption rate.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"462 ","pages":"Article 108304"},"PeriodicalIF":2.4,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143609611","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":"The crystalline silica respiratory hazard from rhyolitic lava dome eruptions in New Zealand's Taupo Volcanic Zone: A case study from the 1315 CE Kaharoa eruption","authors":"C.J. Horwell ,&nbsp;H.M. Emerson ,&nbsp;P. Ashwell ,&nbsp;D.E. Damby ,&nbsp;S. Self ,&nbsp;C. Nattrass ,&nbsp;R. Carey ,&nbsp;B. Houghton","doi":"10.1016/j.jvolgeores.2025.108309","DOIUrl":"10.1016/j.jvolgeores.2025.108309","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The rhyolitic Kaharoa 1315 CE eruption was a complex, long-lived event from Tarawera volcano, New Zealand. Explosive phases were followed by around 5 years of lava dome extrusion and collapse which produced block-and-ash flows (BAF). Lava domes generate crystalline silica in the form of cristobalite, and rhyolitic magmas often contain quartz phenocrysts. Fine-grained ash containing crystalline silica can be formed through dome collapses or explosions, generating a respiratory health hazard for communities affected by ashfall. The aims of this study are to: i) determine whether the Kaharoa eruption dome-forming phase generated substantial quantities of crystalline silica and, therefore, to determine the potential for future dome-forming eruptions of Tarawera to do the same; ii) consider the potential hazard of the crystalline silica by studying the crystal habit and chemistry compared to other lava domes, globally; and iii) assess the particle size and crystalline silica content of the Kaharoa ash, to inform a respiratory hazard assessment.&lt;/div&gt;&lt;div&gt;Five co-BAF ash samples and one co-ignimbrite (explosive) ash sample from the Kaharoa pyroclastic deposits were analysed for health-pertinent factors: particle size distribution and crystalline silica content. Eight dome-rock samples were collected from the dome complex and associated BAF deposits and groundmass texture (especially forms of crystalline silica) and quantity of crystalline silica were assessed.&lt;/div&gt;&lt;div&gt;Cristobalite was present in the 4 ash samples analysed by X-ray diffraction (XRD; 1.3–3.7 wt%) as was quartz (5.7–12.5 wt%). For the 4 dome samples analysed by XRD, all samples contained quartz (4.1–10.4 wt%) and two contained significant quantities of cristobalite (24.7 and 27.3 wt%). Of the two dome samples with minimal cristobalite (visible as individual vapour-phase crystals by SEM but not quantifiable by XRD), one was from the non-devitrified dome carapace and the other was from the compacted interior but had not undergone devitrification. The two dome samples with substantial cristobalite were from dome interiors and were highly devitrified, with well-developed spherulitic textures. Using energy-dispersive X-ray spectroscopy, cristobalite in all samples contained minor aluminium, as has been seen for volcanic cristobalite from other lava domes, which may ameliorate its toxicity. By laser diffraction, the quantities of ash in the health pertinent size fractions varied, with a range of 1.3–8.1 vol% for particles of &lt;4 μm diameter and 1.7–15.6 vol% for particles of &lt;10 μm diameter, which is lower than measured in ash from large-scale dome collapse events at other volcanoes.&lt;/div&gt;&lt;div&gt;The findings suggest a potential for substantial crystalline silica to be formed in future Kaharoa-style eruptions, but that cristobalite generation is site-specific, depending on location within the dome and whether the dome remains sufficiently hot for spherulite formation and glass dev","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"461 ","pages":"Article 108309"},"PeriodicalIF":2.4,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143580508","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":"Transition from growth to collapse of the Plinian column during the 1783 eruption of Asama volcano, Japan, inferred from rock microtextures","authors":"Tatsuki Mizuno ,&nbsp;Fukashi Maeno ,&nbsp;Atsushi Yasuda","doi":"10.1016/j.jvolgeores.2025.108310","DOIUrl":"10.1016/j.jvolgeores.2025.108310","url":null,"abstract":"<div><div>The 1783 eruption of Asama volcano was the most recent high-magnitude explosive eruption (VEI 4) in central Japan. During the climactic phase, the eruption transitioned from the formation of Plinian columns to the generation of pyroclastic density currents (PDCs). This study identified key differences in pyroclastic deposits across eruption styles, showing that changes in density, porosity, bubble microstructure, and water content. The pyroclastic fall deposits were divided into 14 layers of either pumice or ash, five of which contained silty ash derived from earlier PDCs. The pyroclastic fall deposits were overlain by PDC deposits generated in the climactic phase. Compared to fallout pumice, the PDC pumice had lower vesicularity and bubble connectivity but contained finer bubbles and high bubble number densities, suggesting higher magma decompression rates. Furthermore, the temperature and initial water content of the magma calculated from the compositions of the groundmass glasses and the crystals remained almost unchanged during the 1783 eruption, whereas the groundmass glass of the PDC pumice had a higher water content, indicating that the amount of water exsolved from the rising magma decreased. Based on theoretically predicted changes in vesicularity caused by water exsolution, we estimated that the mass fraction 0.81–0.93 of the initial water content was supplied to the plume during the formation of the climactic Plinian columns, and the mass fraction 0.68 during the PDC phase. The reduction in the water supply might have contributed to destabilizing the eruption column and caused the generation of PDCs.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"462 ","pages":"Article 108310"},"PeriodicalIF":2.4,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682322","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":"In one step: Insights into shallow differentiation from basalt to rhyolite at Cordón Caulle from rhyolite-MELTS simulations","authors":"Anna C. Ruefer ,&nbsp;Liam J. Kelly ,&nbsp;Guilherme A.R. Gualda ,&nbsp;Edgar L. Carrillo ,&nbsp;Sarah Hickernell ,&nbsp;Sarah Ward ,&nbsp;Heather Winslow ,&nbsp;Philipp Ruprecht","doi":"10.1016/j.jvolgeores.2025.108305","DOIUrl":"10.1016/j.jvolgeores.2025.108305","url":null,"abstract":"<div><div>Magma mush systems are commonly invoked as the source from which crystal-melt segregation produces rhyolites, but these systems are rarely observed. The 2011–2012 VEI 4 eruption of Cordón Caulle produced rhyolite lavas which scavenged basaltic enclaves. These enclaves contain interstitial glass similar to their host rhyolitic lava, suggesting that these enclaves offer a window into an active, shallow basaltic mush system. This mush was proposed as the source from which crystallization generates high-silica rhyolite in a single step. Here, we use rhyolite-MELTS to determine whether this is thermodynamically realistic. First, we use melt geobarometry to establish that enclave-derived pressures (∼25–200 MPa) are consistent with those previously determined for the lavas. We then simulate isobaric crystallization using a range of initial starting water concentrations to test if it is possible to generate rhyolites of the appropriate composition, assuming a starting composition which is the same as the basaltic enclave whole-rock. We find that it is possible to produce suitable rhyolitic compositions via fractional crystallization. We then explore the simulated physical consequences of crystallization and fluid exsolution. Lower water simulations (0.5–1.0 wt.% H₂O) at pressures of 100–200 MPa produce changes in volume most consistent with pre-eruptive ground deformation signals. We determine the timescales of heat loss from the crystallizing basaltic magma to be ∼8–25 ka, but it is plausible that heat loss occurred on the order of ∼1–10 ka which is broadly consistent with repose times of the system. The application of rhyolite-MELTS to an actively monitored system offers multifaceted insights into the geochemical, thermal, and physical evolution of magmas.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"462 ","pages":"Article 108305"},"PeriodicalIF":2.4,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143620067","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":"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}