Pub Date : 2026-02-01Epub Date: 2025-12-03DOI: 10.1016/j.jvolgeores.2025.108506
Orlando Quintela , Steffi Burchardt , Tobias Mattsson , Birgir V. Óskarsson , Iain Pitcairn , Carl T. Stevenson , Robert A. Askew , Catherine R. Gallagher
Shallow-crustal magma emplacement produces characteristic host rock deformation within a “structural aureole”. Two end-member mechanisms of magma emplacement dominate in the brittle crust: roof uplift, involving upward displacement of overlying rocks, and floor subsidence, involving downward displacement of the underlying rocks—either along tectonic faults or ring faults in cauldron subsidence. While these processes are fundamental to crustal growth, heat transfer, and ore formation, their identification in the field is often based on ambiguous criteria such as intrusion geometry or internal fabrics, leading to inconsistent classifications. We propose a robust set of structural criteria for distinguishing emplacement mechanisms of upper crustal (<5 km) intrusions. These are applied to the Slaufrudalur pluton, Iceland's largest exposed granitic intrusion, using structural mapping and photogrammetry. Previous interpretations framed Slaufrudalur as a classic cauldron subsidence pluton or a sill complex. Our results reveal that the pluton formed in a transtensional setting and is bound by strike-slip faults, fundamentally revising its geotectonic interpretation. This study underscores the value of detailed structural investigation of host-rock deformation for resolving emplacement processes and provides a transferable framework to link pluton architecture and tectonic setting in shallow crustal exposures, with implications for understanding magma transport, geothermal systems, and mineralisation.
{"title":"Structural aureoles as proxies for magma emplacement in the brittle crust: Evidence for transtensional pluton formation at Slaufrudalur, Iceland","authors":"Orlando Quintela , Steffi Burchardt , Tobias Mattsson , Birgir V. Óskarsson , Iain Pitcairn , Carl T. Stevenson , Robert A. Askew , Catherine R. Gallagher","doi":"10.1016/j.jvolgeores.2025.108506","DOIUrl":"10.1016/j.jvolgeores.2025.108506","url":null,"abstract":"<div><div>Shallow-crustal magma emplacement produces characteristic host rock deformation within a “structural aureole”. Two end-member mechanisms of magma emplacement dominate in the brittle crust: roof uplift, involving upward displacement of overlying rocks, and floor subsidence, involving downward displacement of the underlying rocks—either along tectonic faults or ring faults in cauldron subsidence. While these processes are fundamental to crustal growth, heat transfer, and ore formation, their identification in the field is often based on ambiguous criteria such as intrusion geometry or internal fabrics, leading to inconsistent classifications. We propose a robust set of structural criteria for distinguishing emplacement mechanisms of upper crustal (<5 km) intrusions. These are applied to the Slaufrudalur pluton, Iceland's largest exposed granitic intrusion, using structural mapping and photogrammetry. Previous interpretations framed Slaufrudalur as a classic cauldron subsidence pluton or a sill complex. Our results reveal that the pluton formed in a transtensional setting and is bound by strike-slip faults, fundamentally revising its geotectonic interpretation. This study underscores the value of detailed structural investigation of host-rock deformation for resolving emplacement processes and provides a transferable framework to link pluton architecture and tectonic setting in shallow crustal exposures, with implications for understanding magma transport, geothermal systems, and mineralisation.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"470 ","pages":"Article 108506"},"PeriodicalIF":2.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737980","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}
Pub Date : 2026-02-01Epub Date: 2025-12-01DOI: 10.1016/j.jvolgeores.2025.108509
Julia Schunke, Fabian B. Wadsworth, Jackie E. Kendrick, Anthony Lamur, Janine Birnbaum, Yan Lavallée
Hot hydrous pyroclasts vesiculate, diffusively outgas, and sinter during deposition which leads to continuous evolution of their porous-permeable networks. Welded ignimbrites, tuffisites, and sintered in-conduit pyroclasts, all exhibit variable degrees of sintering as well as a broad grain size distribution. How this polydispersity in grain sizes influences evolution has not yet been understood. Where polydisperse models for sintering exist, they are limited to relatively small ash particles (1–50 ) and do not account for vesiculation that occurs in relatively larger pyroclasts. Here, we perform high-temperature sintering experiments using relatively coarse ash-to-lapilli (0.5–2.5 mm) clasts. First, we find that polydisperse systems exhibit more efficient initial packing relative to monodisperse systems. Second, polydisperse samples with fine grains between larger grains may undergo differential size-dependent sintering and vesiculation. Third, for larger grains, particle-particle contact areas are enhanced by vesiculation-driven clast expansion onto neighbouring grains, with some contact flattening. Because both sintering and diffusive outgassing are grain-size dependent, any population at a given time will contain grains that differ in internal vesicularity, H2O content, and size; each evolving on different timescales. We compare our results to sintering models which account for H2O loss and we augment these by empirically capturing the effect of a time-dependent particle radius due to vesiculation. To distinguish between the three dominant processes – sintering, vesiculation, and diffusive outgassing – we introduce a regime diagram. Models for sintering that accommodate the complexity of processes occurring in volcanic environments will be particularly impactful for our conceptual understanding of the conditions under which sintering in conduits or tuffisites may influence eruptive behaviour as a whole.
{"title":"Grain size distribution controls sintering of hydrous pyroclasts","authors":"Julia Schunke, Fabian B. Wadsworth, Jackie E. Kendrick, Anthony Lamur, Janine Birnbaum, Yan Lavallée","doi":"10.1016/j.jvolgeores.2025.108509","DOIUrl":"10.1016/j.jvolgeores.2025.108509","url":null,"abstract":"<div><div>Hot hydrous pyroclasts vesiculate, diffusively outgas, and sinter during deposition which leads to continuous evolution of their porous-permeable networks. Welded ignimbrites, tuffisites, and sintered in-conduit pyroclasts, all exhibit variable degrees of sintering as well as a broad grain size distribution. How this polydispersity in grain sizes influences evolution has not yet been understood. Where polydisperse models for sintering exist, they are limited to relatively small ash particles (1–50 <span><math><mi>μm</mi></math></span>) and do not account for vesiculation that occurs in relatively larger pyroclasts. Here, we perform high-temperature sintering experiments using relatively coarse ash-to-lapilli (0.5–2.5 mm) clasts. First, we find that polydisperse systems exhibit more efficient initial packing relative to monodisperse systems. Second, polydisperse samples with fine grains between larger grains may undergo differential size-dependent sintering and vesiculation. Third, for larger grains, particle-particle contact areas are enhanced by vesiculation-driven clast expansion onto neighbouring grains, with some contact flattening. Because both sintering and diffusive outgassing are grain-size dependent, any population at a given time will contain grains that differ in internal vesicularity, H<sub>2</sub>O content, and size; each evolving on different timescales. We compare our results to sintering models which account for H<sub>2</sub>O loss and we augment these by empirically capturing the effect of a time-dependent particle radius due to vesiculation. To distinguish between the three dominant processes – sintering, vesiculation, and diffusive outgassing – we introduce a regime diagram. Models for sintering that accommodate the complexity of processes occurring in volcanic environments will be particularly impactful for our conceptual understanding of the conditions under which sintering in conduits or tuffisites may influence eruptive behaviour as a whole.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"470 ","pages":"Article 108509"},"PeriodicalIF":2.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737983","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}
Pub Date : 2026-02-01Epub Date: 2025-12-05DOI: 10.1016/j.jvolgeores.2025.108507
Khaled Rahimi , Marcus Bursik
Volcano–tectonic processes in extensional settings influence dike emplacement and vent morphology. In this study, we analyze volcanic vents and tectonic structures in the Hat Creek Graben (HCGR), northern California, using drone-based digital terrain models (DTMs) and digital elevation models (DEMs). These datasets enable high-resolution mapping of vent geometry, lava flows, and fault scarps. Two distinct magma types—low-potassium olivine tholeiitic basalt (LKOT) and calc-alkaline basaltic andesite (CAB)—occur in close spatial and temporal proximity within the graben. We compare vent morphology and orientations to evaluate the influence of magma viscosity and tectonic stress. Results show that low-viscosity LKOT dikes tend to erupt within the graben, forming low-relief cones and en-echelon vent patterns, whereas higher-viscosity CAB dikes often deflect toward fault scarps, forming steeper cones. We interpret that viscosity, in combination with local stress fields and topography, controls dike propagation and vent localization. These findings suggest that vent distribution and morphology can be partly forecasted using knowledge of magma rheology and the regional tectonic framework.
{"title":"Inferring magma-feeding fracture geometry through morphological analysis: A volcanotectonic study of Hat Creek Graben, California","authors":"Khaled Rahimi , Marcus Bursik","doi":"10.1016/j.jvolgeores.2025.108507","DOIUrl":"10.1016/j.jvolgeores.2025.108507","url":null,"abstract":"<div><div>Volcano–tectonic processes in extensional settings influence dike emplacement and vent morphology. In this study, we analyze volcanic vents and tectonic structures in the Hat Creek Graben (HCGR), northern California, using drone-based digital terrain models (DTMs) and digital elevation models (DEMs). These datasets enable high-resolution mapping of vent geometry, lava flows, and fault scarps. Two distinct magma types—low-potassium olivine tholeiitic basalt (LKOT) and calc-alkaline basaltic andesite (CAB)—occur in close spatial and temporal proximity within the graben. We compare vent morphology and orientations to evaluate the influence of magma viscosity and tectonic stress. Results show that low-viscosity LKOT dikes tend to erupt within the graben, forming low-relief cones and en-echelon vent patterns, whereas higher-viscosity CAB dikes often deflect toward fault scarps, forming steeper cones. We interpret that viscosity, in combination with local stress fields and topography, controls dike propagation and vent localization. These findings suggest that vent distribution and morphology can be partly forecasted using knowledge of magma rheology and the regional tectonic framework.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"470 ","pages":"Article 108507"},"PeriodicalIF":2.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737982","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}
Kutcharo volcano in eastern Hokkaido, Japan, has experienced multiple caldera-forming eruptions, the latest being the Kp I eruption around 40 ka, after which activity shifted to post-caldera volcanoes. Among these, Atosanupuri volcano produced multiple pyroclastic eruptions (Ap), recorded in distal dacitic and rhyolitic tephra layers. In proximal areas, exposures are limited and correlations with distal tephra have been unclear, leaving the eruption sequence and magnitude poorly understood. We conducted geological surveys, trenching, and drilling in the proximal area to clarify the Ap deposits. Our results reveal multiple large pyroclastic flow units exhibiting facies characteristics of subaqueous deposition. Correlation with distal tephra allowed reconstruction of eruption sequence, distribution, and magnitude. The Ap eruptions occurred between 30 and 19 ka, including at least two events with a volcanic explosive index (VEI) of 6, with a total dense-rock equivalent eruption volume of ∼40 km3. Most pyroclastic flows were confined within Kutcharo caldera, likely due to preexisting caldera walls. Geochemical evidence shows that the Ap magma system was distinct from that of the Kp I eruption. Considering eruption volume and magma renewal, the Ap eruptions should be regarded as the latest caldera-modifying events of Kutcharo volcano, rather than minor post-caldera activity. Following the Kp I eruption, the neighboring Mashu volcano became active, producing a VEI 6 caldera-forming eruption around 7.6 ka. From the perspective of the caldera cycle, these observations suggest that since ∼19 ka, the main focus of volcanic activity may have gradually shifted eastward from Kutcharo to Mashu volcano.
{"title":"Re-evaluation of the Atosanupuri pyroclastic eruptions: Insights into the latest caldera-modifying eruption of the Kutcharo volcano, eastern Hokkaido, Japan","authors":"Akiko Matsumoto , Mitsuhiro Nakagawa , Hiroshi Kishimoto , Kenta Ueno , Takeshi Hasegawa , Kentaro Takeda","doi":"10.1016/j.jvolgeores.2025.108503","DOIUrl":"10.1016/j.jvolgeores.2025.108503","url":null,"abstract":"<div><div>Kutcharo volcano in eastern Hokkaido, Japan, has experienced multiple caldera-forming eruptions, the latest being the Kp I eruption around 40 ka, after which activity shifted to post-caldera volcanoes. Among these, Atosanupuri volcano produced multiple pyroclastic eruptions (Ap), recorded in distal dacitic and rhyolitic tephra layers. In proximal areas, exposures are limited and correlations with distal tephra have been unclear, leaving the eruption sequence and magnitude poorly understood. We conducted geological surveys, trenching, and drilling in the proximal area to clarify the Ap deposits. Our results reveal multiple large pyroclastic flow units exhibiting facies characteristics of subaqueous deposition. Correlation with distal tephra allowed reconstruction of eruption sequence, distribution, and magnitude. The Ap eruptions occurred between 30 and 19 ka, including at least two events with a volcanic explosive index (VEI) of 6, with a total dense-rock equivalent eruption volume of ∼40 km<sup>3</sup>. Most pyroclastic flows were confined within Kutcharo caldera, likely due to preexisting caldera walls. Geochemical evidence shows that the Ap magma system was distinct from that of the Kp I eruption. Considering eruption volume and magma renewal, the Ap eruptions should be regarded as the latest caldera-modifying events of Kutcharo volcano, rather than minor post-caldera activity. Following the Kp I eruption, the neighboring Mashu volcano became active, producing a VEI 6 caldera-forming eruption around 7.6 ka. From the perspective of the caldera cycle, these observations suggest that since ∼19 ka, the main focus of volcanic activity may have gradually shifted eastward from Kutcharo to Mashu volcano.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"470 ","pages":"Article 108503"},"PeriodicalIF":2.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685659","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}
La Vache et Lassolas are two monogenetic cones located in the south of the Chaîne des Puys (France). They formed during a complex trachybasaltic eruption (8.6 ka) marked by a Subplinian, two violent Strombolian and an effusive phase. We combine physical and textural analyses of pyroclasts from the explosive phases to investigate the effect of shallow magmatic processes on the intensity of this eruption. The results highlight the coexistence of four different textural facies: the crystal poor golden facies (Fg, 59 vol% vesicles; 12 vol% crystals), and three crystals rich facies (14 to 21 vol% vesicles; 38 to 56 vol% crystals), the micro-crystallised facies (Fmc), the crystallised facies (Fc) and the dense facies (Fd). Permeability analyses show that Fmc, Fc, Fd are characterised by a low permeability (< 10−12 m2). Conversely, Fg is characterised by a high permeability (> 10−12 m2). Major elements analyses show that the bulk chemical composition of all the facies is identical. We propose that a degassed, crystal-rich magma is mobilised by a gas-rich and crystal-poor magma, from which it derived at shallow depth. This latter acts as an impermeable cap, preventing degassing in the basement. This causes the overpressure of the system, leading to its opening by a violent decompression (0.87 MPa s−1), followed by a Subplinian phase. Overall, the variation in emissions of degassed and crystal-rich magma during the four eruptive phases proves that the formation of this magma can be a cause and/or consequence of multi-phase eruptions.
{"title":"Shallow magma degassing and crystallisation trigger Subplinian basaltic eruption","authors":"Lisa Corrotti , Lucia Gurioli , Carole Berthod , Etienne Médard","doi":"10.1016/j.jvolgeores.2025.108517","DOIUrl":"10.1016/j.jvolgeores.2025.108517","url":null,"abstract":"<div><div>La Vache et Lassolas are two monogenetic cones located in the south of the Chaîne des Puys (France). They formed during a complex trachybasaltic eruption (8.6 ka) marked by a Subplinian, two violent Strombolian and an effusive phase. We combine physical and textural analyses of pyroclasts from the explosive phases to investigate the effect of shallow magmatic processes on the intensity of this eruption. The results highlight the coexistence of four different textural facies: the crystal poor golden facies (Fg, 59 vol% vesicles; 12 vol% crystals), and three crystals rich facies (14 to 21 vol% vesicles; 38 to 56 vol% crystals), the micro-crystallised facies (Fmc), the crystallised facies (Fc) and the dense facies (Fd). Permeability analyses show that Fmc, Fc, Fd are characterised by a low permeability (< 10<sup>−12</sup> m<sup>2</sup>). Conversely, Fg is characterised by a high permeability (> 10<sup>−12</sup> m<sup>2</sup>). Major elements analyses show that the bulk chemical composition of all the facies is identical. We propose that a degassed, crystal-rich magma is mobilised by a gas-rich and crystal-poor magma, from which it derived at shallow depth. This latter acts as an impermeable cap, preventing degassing in the basement. This causes the overpressure of the system, leading to its opening by a violent decompression (0.87 MPa s<sup>−1</sup>), followed by a Subplinian phase. Overall, the variation in emissions of degassed and crystal-rich magma during the four eruptive phases proves that the formation of this magma can be a cause and/or consequence of multi-phase eruptions.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"470 ","pages":"Article 108517"},"PeriodicalIF":2.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840765","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}
Pub Date : 2026-02-01Epub Date: 2025-11-30DOI: 10.1016/j.jvolgeores.2025.108504
E.R. Garcia-Paredes , F.M. van der Zwan , V.R. Troll , S.B. Jägerup , I.N. Bindeman , J.M.D. Day , M. Aulinas , T.H. Hansteen
The term “xenopumice” describes a pumice-like xenolith of low density, frothy, highly vesiculated, partially molten, silicic crustal material found in mafic volcanic eruption products that usually serves as an indicator of magma-crust interaction. In this study we describe the occurrence of xenopumice in Quaternary eruption sequences at Harrat Rahat, in Saudi Arabia. Harrat Rahat is an intraplate volcanic field, whose last eruption was in 1256 C.E. in proximity to the city of Al-Madinah, and is characterized by a range of volcanic products from basalts to trachyte. This chemical variation found in the volcanic field, has been suggested to be reflective of closed system fractional crystallization with little to no crustal influences. To examine whether xenopumice samples collected indicate crustal assimilation and the extent to which open system processes play a role in the compositional diversity of Harrat Rahat magmas, we analyzed the mineralogy, textural features, whole-rock geochemistry and oxygen isotopes of a set of xenopumice samples and their host basalts. Their subalkaline character with high Si-contents, enriched but variable trace element contents and elevated δ18O (>9.8 ‰) values exclude a plutonic cumulate or lower crustal origin for the xenopumice. Instead, their chemistry and textures overlap with metamorphosed granites of upper Arabian crust and/or (meta-)sedimentary rocks of the Proterozoic Arabian Shield. The δ18O-isotopes of host basaltic magmas (5.1 to 6 ‰) document assimilation of xenopumice material by magmas in some cases. The xenopumices found are an indicator of magma-crust interaction in upper crustal magma reservoirs, emphasizing the importance of evaluating the role of crustal assimilation in the Saudi Arabian Harrats.
{"title":"Evidence for Magma-Crust interaction recorded in Xenopumice from Harrat Rahat, Saudi Arabia","authors":"E.R. Garcia-Paredes , F.M. van der Zwan , V.R. Troll , S.B. Jägerup , I.N. Bindeman , J.M.D. Day , M. Aulinas , T.H. Hansteen","doi":"10.1016/j.jvolgeores.2025.108504","DOIUrl":"10.1016/j.jvolgeores.2025.108504","url":null,"abstract":"<div><div>The term “xenopumice” describes a pumice-like xenolith of low density, frothy, highly vesiculated, partially molten, silicic crustal material found in mafic volcanic eruption products that usually serves as an indicator of magma-crust interaction. In this study we describe the occurrence of xenopumice in Quaternary eruption sequences at Harrat Rahat, in Saudi Arabia. Harrat Rahat is an intraplate volcanic field, whose last eruption was in 1256 C.E. in proximity to the city of Al-Madinah, and is characterized by a range of volcanic products from basalts to trachyte. This chemical variation found in the volcanic field, has been suggested to be reflective of closed system fractional crystallization with little to no crustal influences. To examine whether xenopumice samples collected indicate crustal assimilation and the extent to which open system processes play a role in the compositional diversity of Harrat Rahat magmas, we analyzed the mineralogy, textural features, whole-rock geochemistry and oxygen isotopes of a set of xenopumice samples and their host basalts. Their subalkaline character with high Si-contents, enriched but variable trace element contents and elevated δ<sup>18</sup>O (>9.8 ‰) values exclude a plutonic cumulate or lower crustal origin for the xenopumice. Instead, their chemistry and textures overlap with metamorphosed granites of upper Arabian crust and/or (meta-)sedimentary rocks of the Proterozoic Arabian Shield. The δ<sup>18</sup>O-isotopes of host basaltic magmas (5.1 to 6 ‰) document assimilation of xenopumice material by magmas in some cases. The xenopumices found are an indicator of magma-crust interaction in upper crustal magma reservoirs, emphasizing the importance of evaluating the role of crustal assimilation in the Saudi Arabian Harrats.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"470 ","pages":"Article 108504"},"PeriodicalIF":2.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685547","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}
Pub Date : 2026-02-01Epub Date: 2025-12-02DOI: 10.1016/j.jvolgeores.2025.108508
Xavier Bolós , Nicole Lautze , Mario E. Boijseauneau-López , Mattox Telwar
The Hawaiian Islands are characterized by volcanic activity and intricate hydrogeological systems. Given their isolated location and reliance on imported fossil fuels for energy, exploring for geothermal sources is imperative. Simultaneously, understanding freshwater reservoirs is crucial for sustainable water resource management, considering the islands' susceptibility to climatic variations and increasing demands. This study, situated at the intersection between hydrothermal exploration and freshwater reservoir characterization, aims to contribute to sustainable development across the Hawaiian archipelago. Through integrated analysis of geophysical, groundwater, and mineralogical data from Lāna'i Island, we have identified and characterized concealed hydrothermal activity, proposed a hypothesis for its potential magmatic heat source, and examined associated hydrogeological effects, such as the occurrence of brackish groundwater. Correlations between newly acquired self-potential (SP) data and previously published magnetotellurics (MT) data indicate a hydrothermal upflow within the central and southern regions of the Pālāwai caldera, likely originating from deep magma reservoirs, with the latter supported by prior-collected gravity data. Additionally, X-ray diffraction (XRD) analyses reveal varying degrees of hydrothermal alteration in surface rocks located in the Pālāwai caldera and the rift zone, reflecting past interactions with high-temperature fluids. The spatial alignment of these surface alterations with current upflow zones suggests an active hydrothermal system that still utilizes pre-existing caldera faults, potentially dating back to the shield-building volcanic stage and influencing the formation of warm brackish groundwater within the Pālāwai basin. This hydrothermal influence appears to be restricted to the Pālāwai caldera and the Canyon zone, while the Munro Trail ridge contains a cold freshwater source, likely representing an isolated hydrogeological environment with impounded aquifers. In sum, these findings highlight the existence of a potential geothermal resource at depths of >2 km.
{"title":"Exploring concealed hydrothermal activity in Lāna'i (Hawaiian Islands) and its hydrogeological effects through geophysical surveys","authors":"Xavier Bolós , Nicole Lautze , Mario E. Boijseauneau-López , Mattox Telwar","doi":"10.1016/j.jvolgeores.2025.108508","DOIUrl":"10.1016/j.jvolgeores.2025.108508","url":null,"abstract":"<div><div>The Hawaiian Islands are characterized by volcanic activity and intricate hydrogeological systems. Given their isolated location and reliance on imported fossil fuels for energy, exploring for geothermal sources is imperative. Simultaneously, understanding freshwater reservoirs is crucial for sustainable water resource management, considering the islands' susceptibility to climatic variations and increasing demands. This study, situated at the intersection between hydrothermal exploration and freshwater reservoir characterization, aims to contribute to sustainable development across the Hawaiian archipelago. Through integrated analysis of geophysical, groundwater, and mineralogical data from Lāna'i Island, we have identified and characterized concealed hydrothermal activity, proposed a hypothesis for its potential magmatic heat source, and examined associated hydrogeological effects, such as the occurrence of brackish groundwater. Correlations between newly acquired self-potential (SP) data and previously published magnetotellurics (MT) data indicate a hydrothermal upflow within the central and southern regions of the Pālāwai caldera, likely originating from deep magma reservoirs, with the latter supported by prior-collected gravity data. Additionally, X-ray diffraction (XRD) analyses reveal varying degrees of hydrothermal alteration in surface rocks located in the Pālāwai caldera and the rift zone, reflecting past interactions with high-temperature fluids. The spatial alignment of these surface alterations with current upflow zones suggests an active hydrothermal system that still utilizes pre-existing caldera faults, potentially dating back to the shield-building volcanic stage and influencing the formation of warm brackish groundwater within the Pālāwai basin. This hydrothermal influence appears to be restricted to the Pālāwai caldera and the Canyon zone, while the Munro Trail ridge contains a cold freshwater source, likely representing an isolated hydrogeological environment with impounded aquifers. In sum, these findings highlight the existence of a potential geothermal resource at depths of >2 km.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"470 ","pages":"Article 108508"},"PeriodicalIF":2.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737981","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}
Pub Date : 2026-02-01Epub Date: 2025-11-24DOI: 10.1016/j.jvolgeores.2025.108500
Wenjing Yang , Tianshe Cheng , Xuebin Zhang , Xiangqian He , Guoping Wang , Xujiang Cheng , Linhai Wang , Lijun Guo , Xingfang Duo , Hongsheng Gao
<div><div>A newly discovered bimodal intrusions, consisting of gabbro, gabbrodiorite, granodiorite, and monzogranite, have been identified in the Tasensu area, southwest of Xiwuqi, Inner Mongolia, China. Tectonically, this suite is situated within the paleo-Asian Ocean tectonic domain, exposed on the northwestern margin of the Xilinhaote Block in the eastern segment of the Central Asian Orogenic Belt (CAOB), and immediately adjacent to the Hegenshan Suture Zone to the north. It is of great significance for investigating the geodynamic processes and geological evolution of the Hegenshan Oceanic Plate—a branch of the Paleo-Asian Ocean. LA–ICP–MS zircon U<img>Pb dating was performed on this intrusive suite, yielding crystallization ages as follows: gabbro at (310 ± 1) Ma, gabbrodiorite at (310 ± 1) Ma, granodiorite at (305 ± 1) Ma, and monzogranite at (301 ± 3) Ma. These ages confirm the occurrence of bimodal magmatic activity on the northern margin of the Xilinhaote Block during the Late Carboniferous. The gabbro and gabbrodiorite are primarily composed of plagioclase, pyroxene, and hornblende. Their SiO₂ contents range from 48.56 wt% to 55.17 wt%, exhibiting magnesian, metaluminous, and calc-alkaline traits. In terms of trace elements, they are enriched in: (1) large ion lithophile elements (LILEs) including Rb, Sr, Pb, Th, and U; (2) high field strength elements (HFSEs) such as Zr and Hf; and (3) light rare earth elements (LREEs). In contrast, they show depletion in the LILE Ba and HFSEs Nb, Ta, and Ti. Furthermore, they display a weak negative Eu anomaly, alongside high La/Nb ratios (2.09–4.76), Zr/Nb ratios (23.98–73.84), and low Ce/Pb ratios (2.34–6.23). These trace element signatures are analogous to those of typical island-arc basalts, indicating the gabbro and gabbrodiorite likely originated from partial melting of a depleted mantle wedge metasomatized by fluids from the subducted slab.The coeval granodiorite and monzogranite are predominantly composed of quartz, plagioclase, K-feldspar, and biotite. Their SiO₂ contents span 66.37 wt% to 75.67 wt%, with characteristics of high Si, high K<sub>2</sub>O + Na<sub>2</sub>O, low Fe<img>Mg contents, and weak peraluminosity. Geochemically, they are enriched in LILEs Th, U, Rb, Pb and LREEs, while depleted in HFSEs Nb, Ta, Ti and the LILEs Ba and Sr. Notably, they also exhibit a moderate negative Eu anomaly—consistent with the geochemical fingerprint of typical highly fractionated I-type granites. Combined with analyses of their Rb/Ba ratios (0.11–3.61), Rb/Sr ratios (0.07–3.16), and the CaO/Na₂O vs Al₂O₃/TiO₂ discrimination diagram, the granodiorite is inferred to derive mainly from partial melting of crustal basaltic rocks, whereas the monzogranite likely forms from partial melting of crustal clastic rocks. By synthesizing the research findings on Carboniferous–Early Permian bimodal magmatic rocks within the region, it is evident that the discovery of the Tasensu bimodal intrusions further confirm
{"title":"Discovery and implications of the Late Carboniferous Tasensu gabbro–gabbrodiorite–granodiorite–monzogranite bimodal intrusions in Xiwuqi, Inner Mongolia, China","authors":"Wenjing Yang , Tianshe Cheng , Xuebin Zhang , Xiangqian He , Guoping Wang , Xujiang Cheng , Linhai Wang , Lijun Guo , Xingfang Duo , Hongsheng Gao","doi":"10.1016/j.jvolgeores.2025.108500","DOIUrl":"10.1016/j.jvolgeores.2025.108500","url":null,"abstract":"<div><div>A newly discovered bimodal intrusions, consisting of gabbro, gabbrodiorite, granodiorite, and monzogranite, have been identified in the Tasensu area, southwest of Xiwuqi, Inner Mongolia, China. Tectonically, this suite is situated within the paleo-Asian Ocean tectonic domain, exposed on the northwestern margin of the Xilinhaote Block in the eastern segment of the Central Asian Orogenic Belt (CAOB), and immediately adjacent to the Hegenshan Suture Zone to the north. It is of great significance for investigating the geodynamic processes and geological evolution of the Hegenshan Oceanic Plate—a branch of the Paleo-Asian Ocean. LA–ICP–MS zircon U<img>Pb dating was performed on this intrusive suite, yielding crystallization ages as follows: gabbro at (310 ± 1) Ma, gabbrodiorite at (310 ± 1) Ma, granodiorite at (305 ± 1) Ma, and monzogranite at (301 ± 3) Ma. These ages confirm the occurrence of bimodal magmatic activity on the northern margin of the Xilinhaote Block during the Late Carboniferous. The gabbro and gabbrodiorite are primarily composed of plagioclase, pyroxene, and hornblende. Their SiO₂ contents range from 48.56 wt% to 55.17 wt%, exhibiting magnesian, metaluminous, and calc-alkaline traits. In terms of trace elements, they are enriched in: (1) large ion lithophile elements (LILEs) including Rb, Sr, Pb, Th, and U; (2) high field strength elements (HFSEs) such as Zr and Hf; and (3) light rare earth elements (LREEs). In contrast, they show depletion in the LILE Ba and HFSEs Nb, Ta, and Ti. Furthermore, they display a weak negative Eu anomaly, alongside high La/Nb ratios (2.09–4.76), Zr/Nb ratios (23.98–73.84), and low Ce/Pb ratios (2.34–6.23). These trace element signatures are analogous to those of typical island-arc basalts, indicating the gabbro and gabbrodiorite likely originated from partial melting of a depleted mantle wedge metasomatized by fluids from the subducted slab.The coeval granodiorite and monzogranite are predominantly composed of quartz, plagioclase, K-feldspar, and biotite. Their SiO₂ contents span 66.37 wt% to 75.67 wt%, with characteristics of high Si, high K<sub>2</sub>O + Na<sub>2</sub>O, low Fe<img>Mg contents, and weak peraluminosity. Geochemically, they are enriched in LILEs Th, U, Rb, Pb and LREEs, while depleted in HFSEs Nb, Ta, Ti and the LILEs Ba and Sr. Notably, they also exhibit a moderate negative Eu anomaly—consistent with the geochemical fingerprint of typical highly fractionated I-type granites. Combined with analyses of their Rb/Ba ratios (0.11–3.61), Rb/Sr ratios (0.07–3.16), and the CaO/Na₂O vs Al₂O₃/TiO₂ discrimination diagram, the granodiorite is inferred to derive mainly from partial melting of crustal basaltic rocks, whereas the monzogranite likely forms from partial melting of crustal clastic rocks. By synthesizing the research findings on Carboniferous–Early Permian bimodal magmatic rocks within the region, it is evident that the discovery of the Tasensu bimodal intrusions further confirm","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"470 ","pages":"Article 108500"},"PeriodicalIF":2.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645696","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}
Pub Date : 2026-02-01Epub Date: 2025-12-17DOI: 10.1016/j.jvolgeores.2025.108519
Han Zhang , You Tian , Dapeng Zhao , Rui Gao
The Changbai volcano is the most active intraplate volcano in East Asia. However, the spatial distribution and melt fraction of its magma chambers in the crust remain poorly understood. In this study, we investigate the detailed 3-D S-wave velocity (Vs) structure beneath the volcano using high-quality data recorded by a dense seismic array. Distinct low-Vs anomalies are revealed in the shallow and middle crust. The shallow crustal (∼3–5 km depths) and middle crustal (∼8–15 km depths) anomalies directly beneath the Tianchi caldera are interpreted as magma chambers, whereas the low-Vs anomaly at the shallower depths (< 3 km) may be a zone rich in volcanic fluids. From the Vs reductions, the basalt melt fraction of the shallow magma chamber is estimated to be ∼11–19 %. Integrating the distribution pattern of surface basaltic scoria cones and previous results, we deem that a complex multi-stage magma system exists beneath the Changbai volcano.
{"title":"Complex magmatic system and high-melt fraction of the Changbai volcano revealed by ambient noise tomography with a dense array","authors":"Han Zhang , You Tian , Dapeng Zhao , Rui Gao","doi":"10.1016/j.jvolgeores.2025.108519","DOIUrl":"10.1016/j.jvolgeores.2025.108519","url":null,"abstract":"<div><div>The Changbai volcano is the most active intraplate volcano in East Asia. However, the spatial distribution and melt fraction of its magma chambers in the crust remain poorly understood. In this study, we investigate the detailed 3-D S-wave velocity (Vs) structure beneath the volcano using high-quality data recorded by a dense seismic array. Distinct low-Vs anomalies are revealed in the shallow and middle crust. The shallow crustal (∼3–5 km depths) and middle crustal (∼8–15 km depths) anomalies directly beneath the Tianchi caldera are interpreted as magma chambers, whereas the low-Vs anomaly at the shallower depths (< 3 km) may be a zone rich in volcanic fluids. From the Vs reductions, the basalt melt fraction of the shallow magma chamber is estimated to be ∼11–19 %. Integrating the distribution pattern of surface basaltic scoria cones and previous results, we deem that a complex multi-stage magma system exists beneath the Changbai volcano.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"470 ","pages":"Article 108519"},"PeriodicalIF":2.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790846","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}
Pub Date : 2026-01-01Epub Date: 2025-10-31DOI: 10.1016/j.jvolgeores.2025.108481
Alex S. Gold , Madisen Snowden , James D. Muirhead , Pilar Villamor , Genevieve L. Coffey , Colin J.N. Wilson , Regine Morgenstern
Intra-arc rifts are regions of extensional tectonics and magmatic processes, which can interact and lead to both earthquakes and volcanic activity. We examine the temporal and spatial relationships between the ∼35 km3 (magma), caldera-forming, 232 ± 10 CE eruption from Taupō volcano of the Taupō Volcanic Zone and slip on the adjacent Whakaipō Fault. The spatio-temporal distribution of fault throw is examined through paleoseismic trenching coupled with remote and field-based analyses of the fault scarp and deformed post-eruptive paleoshorelines intersected by this structure. Along the Whakaipō Fault, throw increases towards the volcano, reflecting the role of Taupō volcano in localising fault strain. Paleoseismic trenching exposes an un-degraded paleoscarp with a ∼50° slope draped by 232 CE fall deposits, implying that fault slip occurred no more than days to months prior to the eruption. Analysis of fault and paleoshoreline displacements at Whakaipō Bay on the northern Lake Taupō shoreline suggest that two main phases of Whakaipō Fault slip occurred after the eruption: (1) an ‘aftermath’ phase, occurring over a ∼20-year period after the eruption, during which 10 ± 1.2 m of throw was accrued locally on the fault; and (2) a ‘longer-term’ phase through to the present day, during which 2.8 ± 0.3 m of fault throw has accrued. Faulting during the aftermath phase is estimated to account for ∼78% of the total extension accommodated locally (adjacent to the caldera) on the Whakaipō Fault since the 232 CE eruption. Our observations suggest that caldera-forming eruptions in the TVZ can be associated with complex, volcano-tectonic (i.e., rifting) sequences that feature both pre-eruptive and highly localised, post-eruptive, decametre-scale displacement on caldera-adjacent rift faults.
{"title":"Large-scale rift-related faulting linked to a caldera-forming eruption: A case study from Taupō, New Zealand","authors":"Alex S. Gold , Madisen Snowden , James D. Muirhead , Pilar Villamor , Genevieve L. Coffey , Colin J.N. Wilson , Regine Morgenstern","doi":"10.1016/j.jvolgeores.2025.108481","DOIUrl":"10.1016/j.jvolgeores.2025.108481","url":null,"abstract":"<div><div>Intra-arc rifts are regions of extensional tectonics and magmatic processes, which can interact and lead to both earthquakes and volcanic activity. We examine the temporal and spatial relationships between the ∼35 km<sup>3</sup> (magma), caldera-forming, 232 ± 10 CE eruption from Taupō volcano of the Taupō Volcanic Zone and slip on the adjacent Whakaipō Fault. The spatio-temporal distribution of fault throw is examined through paleoseismic trenching coupled with remote and field-based analyses of the fault scarp and deformed post-eruptive paleoshorelines intersected by this structure. Along the Whakaipō Fault, throw increases towards the volcano, reflecting the role of Taupō volcano in localising fault strain. Paleoseismic trenching exposes an un-degraded paleoscarp with a ∼50° slope draped by 232 CE fall deposits, implying that fault slip occurred no more than days to months prior to the eruption. Analysis of fault and paleoshoreline displacements at Whakaipō Bay on the northern Lake Taupō shoreline suggest that two main phases of Whakaipō Fault slip occurred after the eruption: (1) an ‘aftermath’ phase, occurring over a ∼20-year period after the eruption, during which 10 ± 1.2 m of throw was accrued locally on the fault; and (2) a ‘longer-term’ phase through to the present day, during which 2.8 ± 0.3 m of fault throw has accrued. Faulting during the aftermath phase is estimated to account for ∼78% of the total extension accommodated locally (adjacent to the caldera) on the Whakaipō Fault since the 232 CE eruption. Our observations suggest that caldera-forming eruptions in the TVZ can be associated with complex, volcano-tectonic (i.e., rifting) sequences that feature both pre-eruptive and highly localised, post-eruptive, decametre-scale displacement on caldera-adjacent rift faults.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"469 ","pages":"Article 108481"},"PeriodicalIF":2.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145520679","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}
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