Volcanic Field Research Articles

CatVolc: A new database of geochemical and geochronological data of volcanic-related materials from the Catalan Volcanic Zone (Spain)

The Catalan Volcanic Zone (CVZ) (NE Spain) consists of an intraplate alkaline volcanic zone associated with the opening of the Western Mediterranean and the development of the European Rift System. Volcanic activity in the CVZ started in the L'Empordà area (ca. > 12–8 Ma), extended to La Selva (7.9–1.7 Ma), and finally migrated to the Garrotxa Volcanic Field (< 0.7–0.01 Ma). Despite the scientific interest in the CVZ since the early 19th century, certain aspects remain poorly constrained. These include a full understanding of the spatial and temporal evolution of the magma plumbing system(s) and ascent mechanisms, as well as the chronology of volcanism across the CVZ. Addressing these unresolved questions requires geochemical, petrological, and geochronological data, which, in the case of the CVZ, are scattered and have never been integrated or analysed within a unified framework. Here, we present the CatVolc (Catalan Volcanism) database, which compiles available geochemical and geochronological data of volcanic-related materials from the CVZ. The current version of the database contains geochemical analyses from 405 rock samples (296 juvenile magmatic rocks -including lavas and pyroclasts- and 109 xenoliths), and radiometric/thermoluminescence dating data from 57 rocks (55 volcanogenic and two dykes), 4 paleosols samples developed between volcanic deposits and 1 sample from sediments. For each sample, the CatVolc database lists general information about the sampling site, sample lithology, whole-rock analyses (including major and trace elements), isotopic ratios, mineral chemistry, and radiometric/thermoluminescence dating information, if available. A preliminary analysis of the information contained in the CatVolc database highlights the critical limitations of the current state of knowledge and allows suggesting potential future directions for volcanic-driven investigations in the CVZ. Additionally, the results obtained validate the CatVolc database as a key tool for comprehending the spatial and temporal evolution of the magmatic system(s) and volcanic activity in the CVZ, particularly in the Garrotxa Volcanic Field. This aspect is critical for advancing in the assessment of the volcanic hazards in the region and for gaining a comprehensive understanding of future volcanic activity.

Evolution of a large Quaternary monogenetic field; the multifaceted volcanism of the Serdán-oriental basin, México

The intermontane Serdán-Oriental basin (SOB), located in the Trans-Mexican Volcanic Belt, records a highly contrasting volcanic field with nearly 166 monogenetic volcanoes, including cones, maars, tuff rings, domes, and lava flows, with basaltic to rhyolitic compositions and from effusive to explosive, and magmatic to phreatomagmatic eruptive styles. Even when this volcanic field has been the focus of several volcanological studies, an evolutive model of its volcanism and its implications has not been reported. This is a geological study of SOB volcanism based on the spatio-temporal evolution and characteristics of its volcanoes. For this, new and published data is integrated, including chronostratigraphic, geochemical, and petrological observations, which were further processed and analyzed by GIS tools. The resulting model indicates that volcanism has been continuous from the middle Pleistocene to the Holocene. Based on parameters such as erupted magma chemistry and volcanic landforms, it can be classified into the following volcanic groups: Group 1 is mafic in composition, forming cones and lava flows during the middle Pleistocene (490 to 190 ka). Group 2 comprises predominantly andesitic volcanism characterized by cones and dome clusters erupted during the middle Pleistocene (250 to 200 ka), partially coeval with Group 1. Group 3 is characterized by rhyolitic volcanism associated with the emplacement of domes in the central part of the SOB during the middle to upper Pleistocene (220 to 24.5 ka). Group 4 includes a predominantly basaltic to andesitic volcanism with minor rhyolitic composition, with a characteristic occurrence of phreatomagmatic and magmatic activity, forming maars and tuff rings, scoria cones, and lava flows during the middle Holocene (12.2 to 6.25 ka). The youngest Group occurs in the upper Holocene (<7.5 ka), and it is marked by mafic volcanism in the form of cones and lava flows, as well as by the emplacement of the voluminous Las Derrumbadas rhyolitic twin domes. Overall, the geochemical data shows a bimodal compositional character with a gap of dacitic magmas, compatible with a general scenario dominated by felsic melt extraction from highly crystalline magma reservoirs. Eruptive rate calculations indicate a general increase with time, which goes from <0.18 km3/ky in the first three groups to 1 and 2.9 km3/ky in groups 4 and 5, respectively. Lastly, density maps and lineaments of the eruptive vents, together with crater elongations, allowed the identification of the spatial trends of the SOB volcanism and a comparison with the existing regional major tectonic structures characterizing the local basement. These findings are relevant to understanding the eruptive nature of this active volcanic field and its highly contrasting and multifaceted volcanism.

Big Mantle Wedge and Intraplate Volcanism in Alaska: Insight From Anisotropic Tomography

AbstractWe determine high‐resolution tomographic models of isotropic P‐wave velocity (Vp) and tilting‐axis anisotropy of the Alaska subduction zone using a large number of local and teleseismic data recorded at many portable and permanent network stations in and around Alaska. We find a flat high‐Vp slab in the mantle transition zone (410–670 km depths) beneath western Alaska, which is connected with the subducting Pacific slab at 0–410 km depths, suggesting that a big mantle wedge has formed under western Alaska. Our tilting‐axis anisotropy model reveals complex mantle flows in the asthenosphere. Corner flow in the mantle wedge above the subducting Pacific slab and toroidal flow in the big mantle wedge are revealed, which may cause the Cenozoic intraplate volcanoes in western Alaska and the Bering Sea. In central Alaska, the mantle wedge beneath the Denali volcanic gap is characterized by high‐Vp and subhorizontal fast velocity directions normal to the volcanic arc, which may reflect a remnant of the subducted Yakutat slab. In SE Alaska, the shallow subduction of the Wrangell slab is visible above 150 km depth, and hot mantle upwelling through the Wrangell‐Yakutat slab gap may contribute to the Wrangell volcanic field.

Figurative representations of the Pali Aike volcanic field (Santa Cruz, Argentina - Magallanes, Chile) in comparative perspective with the southern extreme of Patagonia

This paper aims to make a comparison of the figurative representations of the Pali Aike volcanic field (province of Santa Cruz, Argentina – province of Magallanes, Chile) with those registered in other sectors of southern Patagonia, such as the southern shore margin of Lake Argentino (Argentina), the Morros area and the Cerro Benítez-Lago Sofía locality (Chile) during the middle and late Holocene. This analysis was based on integrating background and new information related to different areas. The goal is to evaluate the existence of diverse patterns of representation, considering the morphologies, technical treatment, frequencies, relative abundance of types of motifs in each area, distribution within the space, and temporality of figurative motifs. From this, it is expected to advance the discussion of information exchange among hunter-gatherer groups through figurative representationson a macroregional scale.

Precursors to a continental-arc ignimbrite flare-up: Early central volcanoes of the San Juan Mountains, Colorado, USA

Abstract Our newly acquired and recently published map, geochronologic, and compositional data for early intermediate-composition central volcanoes in the northeastern San Juan Mountains provide insights about the broad magmatic precursors to the large continental-arc ignimbrite flare-up in the mid-Cenozoic Southern Rocky Mountain volcanic field (SRMVF). Initial volcanism migrated from central Colorado to northern New Mexico ca. 40–29 Ma, as part of a more regional trend of southward-progressing mid-Cenozoic magmatism in the U.S. segment of the North American Cordillera. Within the San Juan locus, which represents the largest preserved erosional remnant of the SRMVF and site of most intense eruptive activity, new 40Ar/39Ar and U-Pb zircon ages show that eruptions at many individual edifices began nearly concurrently, at ca. 35 Ma, with peak activity at 34–32 Ma. Broadly similar precursor effusive volcanism characterizes other major loci of continental-arc ignimbrite magmatism along the western American cordilleras, but none of these sites records early volcanism as voluminous, spatially widespread, well exposed, or compositionally diverse as the San Juan locus in Colorado. Early San Juan volcanism was larger in volume than the later ignimbrites, constituting about two thirds the total erupted. Early lava and breccias are as much as 700–900 m thick where exposed along eroded flanks of the San Juan Mountains; drill holes have penetrated sections as thick as 2600 m. The early volcanoes were dominantly andesitic, with lesser dacite and minor rhyolite. Such volcanism is widely interpreted as initiated by basaltic magma from the mantle, but mid-Cenozoic basalt is almost nonexistent at the San Juan locus—an absence inferred to be due to extensive lower-crustal assimilation and fractionation. The early volcanic rocks are calc-alkaline and typical of high-K continental-arc volcanism; they become modestly more alkalic and enriched in trace elements such as light rare earth elements, Zr, Nb, and Th from the San Juan locus northeastward into central Colorado. Such variations may reflect synmagmatic crustal thickening and deeper levels of primary magma generation concurrent with assembly of upper-crustal magma bodies that could support large ignimbrite eruptions. Substantial uncertainties remain for growth histories of the early volcanoes, however, because of unexposed lower parts of edifices, eroded upper parts, and limited availability of mineral phases that could be dated reliably. Although the early volcanoes are widely distributed within the SRMVF, many are clustered at sites of subsequent ignimbrite calderas. The precursor edifices are inferred to record incubation stages in construction of overall translithospheric batholithic-scale magmatic systems. Prolonged processes of incremental magma generation, accumulation, fractionation, and solidification intermittently generated sufficient liquid to erupt large ignimbrites. Maturation of focused eruptions and intrusions was prolonged, 5 m.y. or more, prior to the culminating ignimbrite at some centers in the San Juan Mountains. Some large-volume ignimbrites and related calderas, including the ~5000 km3 Fish Canyon Tuff and associated La Garita caldera, formed as much as several million years later than peak growth of associated precursor volcanoes, recording a sustained interval of diminished eruptive activity as the magma reservoir increased in volume and evolved to more silicic compositions capable of supporting a subsequent large ignimbrite eruption. Dike configurations at early volcanoes that were active nearly concurrently in the SRMVF vary from symmetrically radial to more parallel trends. The contrasting dike geometries are inferred to record possible multiple fluctuations from compressive to weakly extensional regional stress, concurrent with destabilization of the prior flat-slab plate configuration that triggered mid-Cenozoic ignimbrite flare-ups along the Cordilleran margin of the North American plate. These apparent fluctuations in regional stress preceded development of substantial extensional strain in the Southern Rocky Mountain region; outflow ignimbrite sheets of the SRMVF spread across subsequent horst-and-graben structures of the Rio Grande rift without complementary thickness variations.

Deep-sourced CO2 emissions from the Eastern Himalaya Syntaxis and the Tengchong Volcanic Field, southeast Tibet

The India-Asia collision zone is believed to play a central role in Earth's geological carbon budget. The processes controlling soil CO2 flux and mechanism at this continental subduction zone margin remain however poorly constrained. Here, we focus on hydrothermal CO2 emissions from southeast Tibet, specifically from the Eastern Himalaya Syntaxis (EHS) and the Tengchong Volcanic Field (TVF), with the twin goals of informing models of carbon cycling and ascertaining the source of hydrothermal degassing systems. In-situ measurements of soil CO2 flux from the Aqiong, Caquka, Nongchaka, Rongduo, and Woka hydrothermal fields of the EHS yield average soil CO2 fluxes of 72, 5, 13, 66, and 10 g m−2 day−1, respectively. Regional heat flow, tectonic regimes, and CO2 content in the spring gas are plausible controlling factors for soil CO2 flux, which is crucial to quantifying total CO2 output in continental collision zones. The compositions and He-C-N isotopes of hydrothermal volatiles from two study regions are reported here as well. Analysis of the He-C-N isotopes in terms of distances to the Jiali fault and the nearest Holocene volcano confirms that the Jiali fault and Holocene volcanoes have a significant impact on discharging deep-sourced CO2 from the EHS and TVF hydrothermal systems to the surface. The 3He/4He values of EHS hydrothermal volatiles (92 to 98°E), combined with previous data (82 to 92°E), show a clear increasing trend from south to north. Thus, we propose an updated model of enriched mantle wedge source for the EHS hydrothermal volatiles, based on multi-component mixing calculations of the He-CO2 systematics. The EHS hydrothermal volatiles exhibit systematics spatial variations from the core location to the bilateral segments, suggesting the highest 3He/4He ratio and carbonate-rich characteristics at the core location possibly controlled by the asthenosphere upwelling caused by the deep fragmentation structure.

A three-dimensional Moho depth model beneath the Yemeni highlands and rifted volcanic margins of the Red Sea and Gulf of Aden, Southwest Arabia

Knowing Moho discontinuity undulation is fundamental to understanding mechanisms of lithosphere-asthenosphere interaction, extensional tectonism and crustal deformation in volcanic passive margins such as the study area, which is located in the southwestern corner of the Arabian Peninsula bounded by the Red Sea and the Gulf of Aden. In this work, a 3D Moho depth model of the study area is constructed for the first time by inverting gravity data from the Earth Gravitational Model (EGM2008) using the Parker-Oldenburg algorithm. This model indicates the shallow zone is situated at depths of 20 km to 24 km beneath coastal plains, whereas the deep zone is located below the plateau at depths of 30 km to 35 km and its deepest part coincides mainly with the Dhamar-Rada’a Quaternary volcanic field. The results also indicate two channels of hot magmatic materials joining both the Sana’a-Amran Quaternary volcanic field and the Late Miocene Jabal An Nar volcanic area with the Dhamar-Rada’a volcanic field. This conclusion is supported by the widespread geothermal activity (of mantle origin) distributed along these channels, isotopic data, and the upper mantle low velocity zones indicated by earlier studies.©2023 China Geology Editorial Office.

The geodynamic origin of Los Humeros volcanic field in Mexico: insights from numerical simulations

Compared to normal arc-related volcanic eruptions, the formation of a volcanic caldera is a relatively atypical event. During caldera formation a series of large volumes of magma are erupted, reducing the structural support for the rock above the magma chamber and creating a large depression at the surface called caldera. Los Humeros volcanic field (LHVF) represents one of the largest volcanic calderas in Mexico. It is located some 400 km from the trench at the eastern edge of the Trans Mexican Volcanic Belt where the depth to the Cocos slab is more than 300 km. In this study we employ high-resolution two-dimensional thermomechanical numerical simulations of magma intrusions and a horizontal tectonic strain rate to better understand the influence of crustal deformation for the formation of Los Humeros caldera. A minimum number of three thermal anomaly pulses of hydrated mantle material (with diameter of 15 km or more) and a regional strain rate of 7.927 × 10–16 s−1 are required for magma to reach the surface. Modeling results show that regional extension coupled with deep thermal anomalies (with a temperature excess of ΔT ≥ 100 °C) that come in a specific chain-type sequence produce surface deformation patterns similar to LHVF. We propose an asthenospheric sub-slab deep source (> 300 km depth) for the thermal anomalies where previous studies showed the existence of a gap or tear in the Cocos slab.

Crustal root shapes the plumbing system of a monogenetic volcanic field as revealed by magnetotelluric data

The plumbing systems of subduction-zone volcanoes consist of magma reservoirs with different degrees of evolution at multiple depths. The geometries of plumbing system of intraplate monogenetic volcanic fields are generally characterized by basaltic magma ascending from the mantle and/or a shallower reservoir along dikes. However, the shape and vertical extent of these plumbing systems are largely unknown due to the rareness of robust geophysical data. The possible role of faults and mountain chains in controlling the geometry of magma reservoirs is also poorly understood. To address these limitations, we present a three-dimensional resistivity structure beneath the Holocene Jingpohu Monogenetic Volcanic Field (JMVF) in the Zhangguangcai Range (ZGC), northeastern China. The resistivity model was derived from the magnetotelluric data in a dense net-like array. We identified an inverted cone-shaped high-resistivity (∼10,000 Ω m) anomaly below the ZGC. This anomaly traverses almost the entire crust. We interpret this high-resistivity anomaly to be the stiff basement of the ZGC. At the base of the resistive volume, we resolved a sill-like, low-resistivity anomaly that occurs at the top of the lithospheric mantle. Sheet-like low-resistivity anomalies surrounding the high-resistivity body depart from the lithospheric mantle. We interpret these sill- and sheet-like anomalies as a trans-crustal saucer-shaped magma plumbing system beneath the JMVF. This system involves multi-level magma reservoirs, including basaltic magma at its base, basaltic dikes/sills swarms in the middle and sill intrusions in the upper crust. We propose that the stiff crustal root and the topographic loading of the ZGC work together to deflect the upward magma propagation towards the edges of the ZGC. The magma ascent to the surface is probably controlled by pre-existing, lithospheric faults. Our data show how mountain chains, together with the crustal structure, play a key role in controlling the geometry of multi-level plumbing systems of intraplate monogenetic volcanic fields.

Lithospheric Sill Intrusions and Present‐Day Ground Deformation at Rhenish Massif, Central Europe

AbstractThe Rhenish Massif in Central Europe, which includes the Eifel Volcanic Fields, has shown ongoing ground deformation and signs of possible unrest. A buoyant plume exerting uplift forces at the bottom of the lithosphere was proposed to explain such deformation; the hypothesis of (possibly concurrent) melt accumulation in the crust/lithospheric mantle has not been explored yet. Here, we test deformation models in an elastic half‐space considering sources of varying aspect ratio, size and depth. We explore the effects of data coverage, noise and uncertainty on the inferred source parameters. We find that the observed deformation would require melt accumulation in sub‐horizontal sill‐like structures expanding at the rate of up to ∼0.045 km3/yr. We discuss feasibility, limitations and possible interpretations of our resulting models and elaborate on further observations which may help constrain the structure of the Rhenish Massif magmatic system.

The role of the Red Sea rift and the inherited geological structures in the seismo-volcanic activity along the rift flanks

The role of the Red Sea rift on the development and the discrepancy of the seismo-volcanic activity along its flanks is still a debate. Here we tried to resolve this debate by a high-resolution tomographic imaging of the northern Red Sea subsurface structures. For the first time, a large number of arrival time data from the Saudi and Egyptian seismic networks were used. The area comprises the Lunayyir volcanic field in the Saudi Arabia, the Abu-Dabbab seismogenic zone in the Egyptian Red Sea coast, and the Zabargad Shear Zone in the Red Sea. This study revealed clear images of the Red Sea rift-related structures along its flanks. The subsurface extension of the different shear and suture zones existing in the Arabian Nubian shield are well imaged. It is found that the Lunayyir seismo-volcanic activity is possibly controlled by the reactivation of the Yanbu suture zone that is associated with steeply northwestward dipping structure. The suture detachments were observed and identified across the Red Sea as low-V channels. The Egyptian Eastern Desert is found to be highly deformed with crustal-scaled low-V structures which were inherited from the early period of Gondwana collision. The NE-SW strike slip faults along the Red Sea were found to be a part of this deformation that are extended deeply in the crust. The Abu-Dabbab and Marsa-Alam areas were strongly influenced by this deformation with possible magma intrusions. This study provides new insights on the role of the Red Sea in the seismo-volcanic activity along its flanks.

The temporal evolution of monogenetic volcanism in the Central Andes: 40Ar/39Ar geochronology of El Negrillar volcanic field, Chile

The temporal evolution of monogenetic volcanism in the Central Andes: 40Ar/39Ar geochronology of El Negrillar volcanic field, Chile

Geodynamic Controls on Basaltic Volcanism in the Arabian Peninsula: Evolution of Harrat Uwayrid, Saudi Arabia

AbstractBasaltic lavas from Harrat Uwayrid, Saudi Arabia, record the evolving magmatic and tectonic context of the Arabian Peninsula from at least the mid‐Miocene to the present day. New 40Ar/39Ar ages spanning from the mid to late Miocene reveal that mid‐Miocene mafic volcanism formed a large, subalkaline volcanic plateau parallel to Red Sea rifts. Subsequent volumetrically subordinate late Miocene‐Quaternary alkaline volcanism erupted monogenetic cinder cones roughly orthogonal to the earlier volcanic field. The source region for all samples was affected by both fluid and silicate metasomatism; inferred mantle mineral assemblages include amphibole for mid‐Miocene lavas and phlogopite for late Miocene‐Quaternary samples. Calculated melting depths become shallower with time across the Miocene volcanic episode (∼20–15 Ma) but become deeper in the late Miocene to Quaternary (∼10–0 Ma), indicating melting pressures and temperatures significantly higher than those recorded in Miocene lavas despite progressive lithospheric thinning. We offer a two‐stage model for the formation of Harrat Uwayrid: (a) Early‐ and mid‐Miocene rifting associated with the Red Sea opening facilitated adiabatic melting of uppermost mantle lithosphere to form the early volcanic plateau and (b) Plate motion changes in the mid‐ and late‐Miocene initiated the Dead Sea Fault and destabilized a dense pyroxenitic lower lithosphere leading to foundering or lithospheric drip beneath Harrat Uwayrid that allowed deep lithospheric melting and formed the young volatile‐rich eruptives.

Magma storage conditions over the past 4 Ma on Martinique Island, Lesser Antilles

We constrain, for the first time, the storage conditions beneath recent (<5 Ma) volcanic edifices in Martinique Island, combining petrography, geochemistry, and thermobarometry. Specifically, we investigate Morne Jacob volcano (5.2–1.5 Ma), Pitons du Carbet complex (998 ka – 322 ka), Trois Îlets Volcanic field (2.35 Ma – 346 ka), and Mt. Conil – Mt. Pelée system (<550 ka). Lava samples range in composition from basalt to dacite, and in age from 4.1 Ma (Morne Jacob) to 1929 CE (Mount Pelée). For the last ∼5 Ma, the volcanoes in Martinique were fed by andesitic to dacitic magma stored in the upper 6 km of the crust, at temperatures between 900 and 1100 °C. These shallow reservoirs were frequently replenished and remobilized by basaltic and basaltic-andesite magmas originating from the lower crust with temperatures as high as 1200 °C. Erupted products contain simple to more complex mineral assemblages, and plagioclase phenocrysts exhibit textures and compositional profiles typical of antecrysts, identified as (1) normal, (2) oscillatory, (3) sieved, (4) resorbed core, and (5) resorbed rim. All complexes also show a crystallization gap in the middle crust (10–18 km). Trois Îlets, a distributed volcanic field, is the only complex that shows continuous crystallization through the entire crust, distinct magma batches and storage regions for each individual volcano. More importantly, we see drastic changes in terms of rock composition, storage conditions, and crystal populations in pre - and post – collapse lavas. Large flank collapse (> 5 km3) can induce decompression as large as 5 MPa in the upper crust and as low as 0.1 MPa down to 10–12 km. Such decompression magnitudes might be sufficient to enhance ascent of basaltic magma from depth, initiate dike intrusions in the mid to upper crust, and remobilize shallow silicic reservoirs. Such events are likely to initiate magma mixing in shallow reservoirs. This noteworthy eruption-triggering mechanism may lead to the incorporation of distinct crystal populations and subsequently contribute to heightened rates of eruption. In summary, the magma storage conditions and plumbing system architecture for the recent volcanoes in Martinique closely resemble those observed in other volcanoes within the Lesser Antilles Island Arc, such as Soufriere Hills Volcano or La Soufriere de Guadeloupe. These newly established correlations offer valuable insights that can aid in the assessment of potential future volcanic eruptions.

The dynamic nature of aTiO2: Implications for Ti-based thermometers in magmatic systems

Abstract In recent decades, new Ti-based thermometers have found widespread use in geosciences, providing a convenient and powerful tool for investigating the crystallization temperatures of quartz and zircons in magmatic systems. However, a commonly overlooked aspect is the constraint of TiO2 activity (aTiO2liquid–rutile). Many studies assume aTiO2 to be constant or equate the presence of Ti-rich phases, such as ilmenite, with fixed activity levels. Using solubility models and data from natural systems, we demonstrate that aTiO2 is a dynamic parameter, influenced by temperature, mineral assemblage, and TiO2 content in the melt. Focusing on examples from several volcanic fields (Bishop Tuff, Fish Canyon Tuff, Yellowstone, and Shiveluch), we discuss the impact of these factors on aTiO2 and highlight how inadequate constraint of aTiO2 can lead to erroneous interpretations of magma storage conditions.

Decoding subcontinental lithosphere processes: The key role of fractional crystallization in Central Andes monogenetic volcanism - Insight from El Negrillar volcanic field, Chile

Subduction zones are complex geodynamic settings in which volcanic arcs form due to the interaction between subducting slabs, water, and continental materials. Investigating this extensive Earth recycling system offers valuable insights into the exchange of materials between the crust and mantle. While previous research has primarily focused on analyzing polygenetic volcanoes to explore this interaction, monogenetic volcanic fields (MVF) present an opportunity to delve into the mechanisms operating within the upper and lower mantle. Monogenetic volcanoes are a class of volcanoes that are typically smaller in size but showcase a range of eruptive styles and compositions. These volcanoes can be found in various locations along the arc, including the main Central Volcanic Zone (CVZ) (arc-front volcanoes), and even far from the tectonic plate boundaries in the back-arc region (intraplate volcanism).We carried out a detailed geochemical study of El Negrillar (EN) MVF, located in the Central Andes main-arc, on the Altiplano-Puna Plateau's southwestern border. The volcanic field has 35 eruptive centers and a total of 86 eruptive phases originating from its three clusters: Northern, Central, and Southern. EN magmas range in composition from basaltic andesite to dacite and have produced over 6.8 km3 (DRE) of lava and pyroclastic material, which makes it the most voluminous volcanic field in the Central Andes, and therefore, an excellent example to study MVF in arc-systems. We have conducted an extensive study encompassing major and trace elements, as well as isotopic analysis using whole rock Sr-Nd-Pb. We also present an analysis of our results with available geochemical data from the back-arc and main-arc volcanoes, including other monogenetic volcanoes near EN (<80 km, EN's neighbors). The results revealed that EN magmas and their neighbors are strongly related and exhibit a clear similarity in major and trace element compositions and isotopic ratios, indicating a common source and origin of their melts. Our comparison across the arc surprisingly reveals similarities between EN and back-arc monogenetic volcanism. Both regions indicate geochemical signatures that do not support melting via slab metasomatism, typical of subduction zones. Instead, they show low Th/Ce (<0.1 ppm) and Ba/La (<30 ppm) and high Ce/Pb (>6 ppm), Ba/Th (>100 ppm), high 143Nd/144Nd > 0.51240, and La/Yb ratios at a given La/Sm compared to the main-arc polygenetic volcanoes. Interestingly, EN also exhibits adakite-like signatures with increasing SiO2 content (high Sr > 600 ppm, Sr/Y > 40, and high La/Yb > 20), a term used for igneous rock suites with chemical characteristics that are identical to those of adakites but produced through petrogenetic processes that do not include a slab component. We explore how fractional crystallization and crustal assimilation participate in the development of monogenetic volcanoes, and our findings underscore the significant influence of fractional crystallization on the monogenetic volcanic processes in the Salar de Atacama region. The geochemical changes observed in this area can be attributed to a combination of varying degrees of fractional crystallization within magmas generated through the partial melting of a garnet-enriched environment, which could be primary lower crust or partial melting of a peridotite mantle that has later equilibrated with garnet-bearing crustal melts.

The effect of fault systems on volcanic activity: Insights from the subduction-related, Quaternary Villamaría-Termales monogenetic volcanic field in Colombia

Structural control of volcanic activity is a topic of great significance around volcanic fields, mostly associated with risk management near cities. Structural geology provides valuable information for understanding the magmatic processes associated with the rise of magma and the presence of volcanoes. The Villamaría-Termales Monogenetic Volcanic Field (VTMVF) is a group of Quaternary monogenetic volcanoes settled in an active fault system, which allows us to propose the role that these faults play in the volcanic activity. The field is located near the city of Manizales (∼475.000 inhabitants), Colombia, on an active fault system at the western flank of the Cordillera Central in the northern Andes. The VTMVF is characterized by andesitic lava domes and flows, which individually reach volumes of up to 2.5 km3. This work uses 1) geometry and kinematics of the faults that affect the VTMVF to define the structural features associated with the emplacement of the volcanoes, and 2) new and published ages to evaluate periods of volcanic activity. Three trends of fault systems associated with the location of the volcanoes were identified: 1) NW-SE (Villamaría-Termales), 2) NE-SW (Sancancio, El Perrillo, Santa Rosa and Palestina), and 3) N-S to NNE-SSW (San Jerónimo and Samaná-sur). The fault kinematics are dominantly normal, with dextral (NE) and sinistral (NW) movements. Analysis of ages shows that the field has temporally evolved since 2 Ma in different time intervals (2.0–1.2 Ma, 0.18–0.045 Ma, and 0.045 Ma – Present). This supports the presence of different emplacement mechanisms related to both the movement in the strike of some faults and the intersection between faults. The pauses of volcanic activity could coincide with the absence of structural conditions (interseismic cycles for faults, where the sealing of the faults is generated) to facilitate the rise of magma; this is related to temporary compressive conditions. Despite the apparent structural controls, there is no clear spatial or temporal pattern of volcano distribution within the field. There is evidence of seismic activity in the area. Thus, the future formation of dilatating zones that allow the magma to rise and the emplacement of new monogenetic volcanoes is feasible not only in the area defined for the volcanic field but also in the continuation of the fault lines around it.

Characteristics of ash particles from the maar complex of Lamongan Volcanic Field (LVF), East Java, Indonesia: How textural features and magma composition control ash morphology

The Lamongan Volcanic Field (LVF), East Java, Indonesia, has experienced numerous maar eruptions, producing varied properties and morphologies of ash particles. This study conducted textural, morphometric, and geochemical analyses of the juvenile particles to elucidate the factors governing their heterogeneous characteristics. Two distinct types of juvenile ash were identified: A (black and brown ash) and B (orange-brown ash), reflecting different fragmentation processes. The blocky to slightly elongate shapes of juvenile A across heterogenous basaltic compositions (resulting in variable textures, rheological properties, and/or cooling histories) highlight the phreatomagmatic process as the primary control of their shape. In contrast, the irregular-fluidal shapes of juvenile B particles indicate magmatic fragmentation of basaltic andesite magma. This study reveals that variable magma properties yield diverse ash components, yet fragmentation dynamics govern pyroclast shapes in the LVF maar complex. Our integrated approach emphasizes the importance of considering multiple variables when interpreting heterogeneous volcanic ash deposits.

Lithostratigraphy of the ignimbrite-dominated Miocene Bükk Foreland Volcanic Area (Central Europe)

This study documents the volcanic evolution of the Miocene silicic Bükk Foreland Volcanic Area (BFVA), Northern Hungary (Central Europe) at an event-scale. The BFVA is a deeply eroded and dissected volcanic field dominated by multiple, several 10-m thick, valley-filling silicic ignimbrite units, which are chemically and texturally very similar to each other. Hence, establishing lateral correlation is a real challenge due to the sporadic and small-scale outcrops and lack of stratotypes. Detailed field observations allowed us to identify eleven lithological members including fourteen eruption events and establish a nearly complete lithostratigraphic correlation between fifteen outcrops across the BFVA. Primary pyroclastic material of each member was sampled, and volcanic glass was analyzed for major and trace element composition. The geochemical results confirm the field-based classification of the members and enable the correlation of distinct outcrops. The major and trace element composition of the glassy pyroclasts of each member of the BFVA served as basis to create a field-wide chemical reference database for regional correlational studies. Here, a new lithostratigraphic classification scheme consisting of one formation and eleven members is presented, which reflects the challenges unraveling the stratigraphy of ancient volcanic terrains. The field-based event-scale lithostratigraphy of the BFVA suggests a wet, partly sea-covered depositional environment in the close vicinity of the eruption centers providing favorable conditions to ‘fuel’ silicic explosive phreatomagmatism. On the contrary, paleosol horizons formed after almost each major eruption event or sequence suggests an overall near-coast terrestrial environment for the BFVA, where the emplacement of the pyroclastic material occurred.

Monogenetic volcanoes as windows into transcrustal mush: A case study of Slamet and Loyang volcanoes, Central Java

Monogenetic volcanic fields (MVFs) are commonly associated with long-lived polygenetic composite volcanoes in many tectonic settings. The association between polygenetic and monogenetic volcanoes has raised questions as to the source of melts feeding monogenetic volcanoes – specifically, whether they are derived from the transcrustal mush underlying a nearby polygenetic volcano, or from a batch of parental magma derived from a different mantle source. To address this question, we studied a well-constrained suite of scoria samples from Gunung Slamet in Central Java, Indonesia, and its most distal monogenetic scoria cone, Gunung Loyang. Slamet is composed of calc-alkaline basalts, and has an extensive MVF on its eastern flank, similar to other Indonesian volcanoes. We analyzed the textural and chemical features of the olivine cargo in both volcanoes, including olivine- and clinopyroxene-hosted melt inclusions. These melt inclusions are the first such analyzed for volatile element contents (H2O, CO2) in the Slamet-Loyang system. We applied hierarchical clustering and mass balance models to constrain the features of the olivine populations in both systems. The olivines in both volcanoes cluster in five distinct textural groups, defined by the presence or lack of zoning and resorption, and according to the type and degree of zoning they exhibit. Olivines show a range of moderate to evolved Fo%, and they also show significant variation in nickel contents (50–1600 ppm). By estimating saturation pressures of entrapped melt inclusions, we observe that Loyang olivines are drawn from a similar petrological system as Slamet, but from deeper mid-crustal levels (12 km), and more mafic source. Our work suggests that monogenetic volcanoes like Loyang can be used as “petrological windows” into the deeper crustal levels of mush reservoirs at composite stratovolcanoes and their associated MVFs.