Lava Research Articles

Evaluating signal bleaching of Al and Ti–Li centers in fluvio-lacustrine sediments of Datong, North China, and its implications for the volcanic eruption chronology

Assessing the adequate bleaching of quartz Electron Spin Resonance (ESR) signals at the time of deposition is essential for sediment ESR dating. In this study, we focus on the Datong volcanic group is situated in Datong City, Shanxi Province, and is among the most renowned volcanic groups in China. The eruption within the Datong volcanoes during a geological period resulted in extensive high-temperature lava flow that directly overlaid Quaternary lacustrine deposits and subjected the underlying lacustrine layers to high-temperature heating. Thus, an investigation of the field profile in the Yujiazhai area, southeast of the Datong Volcanic Group, shows a novel approach for assessing the bleaching extent of ESR centers. This is accomplished by comparison of the DE values of the Al and the Ti–Li centers in partly-heated layer sample. The result reveals that quartz Al and Ti–Li centers in the lacustrine sediments appear to undergo sufficient bleached during transportation and natural bleaching processes in the study area. Furthermore, this study provides insight into the chronology of volcanic eruption in the Yujiazhai area, estimating an eruption age of approximately 300 ka. This volcanic activity most likely corresponds to the third volcanic activity period in the Datong region.

Transition of dome formation to sudden explosive eruptions at Popocatépetl, Mexico: magnetic indicators

Transitions from effusive to explosive activity can increase hazards making it crucial to define early indicators such as changes in the magnetic signals. After more than 80 cycles of crater-dome extrusion and destruction from 1996 on, Popocatépetl volcano (Mexico) experienced changes in its behavior from March 15 to 18 July 2019, when no lava domes were observed. Some of the domes behaved as contained lava flows within the crater floor (pancakes) while others were more irregular-shaped. Activity decreased considerably over this 2019 interval except for the unexpected explosions in March and June, that produced ash plumes reaching up to 14,000 m a.s.l. In order to investigate the causes of the transition from effusive to explosive behavior in March and June, we analyzed the time series from the magnetic monitoring network at Popocatépetl volcano between October 2018 and December 2019. The raw signals were analyzed by weighted differences (WD) based on the elimination of non-local changes from the total intensity values of the geomagnetic field and the discrete-time continuous wavelet transform was used to evaluate the local variations of energy within the time series. The high energy periods (linked to negative magnetic anomalies) are induced by magma ascent associated with movement within the conduit. They indicate that the sudden explosions were due to the ascent of several magma batches that were slowed during ascent and were not able to reach the surface. Changes in the rheology of the lava are linked to the influx of several batches of magma with different compositions as well as to compaction by gas loss when ascending andesitic magma pushed out overlying more viscous degassed magma clearing the conduit, which can explain why these sudden explosions were more energetic. Several geophysical data sets as well as tephra compositions were integrated to support this conclusion. The correlated multiparameters also confirm that geomagnetic volcano monitoring has been essential in understanding the processes that drive the observed changes in eruptive behavior. We present new evidence for the detection of transient events produced by magma ascent and changes in the feeding system of Popocatépetl volcano with wavelet analysis. Detailed vulcanomagnetic processing, especially when it is correlated with other monitoring parameters, provides information on ascending magma and several conduit processes that would otherwise be camouflaged. Ascending batches may precede an eruption but they can also ascend in several pulses indicating how dome growth occurs.

Hot rings on Io observed by Juno/JIRAM

It has been thought that Io’s many paterae may contain lava lakes, but observations by NASA’s Galileo spacecraft at sufficiently high resolution were limited to a few locations, such as Loki Patera. Data acquired by NASA’s Juno mission in May 2023 reveal a common set of thermal characteristics for at least ten paterae on Io, with bright (hot) “thermal rings” around the perimeter of their floors. Loki, Surt, Fuchi, Amaterasu, Mulungu, Chors, and Dazhbog Patera, and four unnamed paterae, all show the same pattern of surface temperature. This new Juno/JIRAM data suggests that hot rings around paterae are a common phenomenon, and that they are indicative of active lava lakes. All the investigated paterae lack recent lava flows on their flanks, suggesting that at the time of observations, the level of the lake was not high enough to overflow the rim. These observations provide insight about the characteristics of paterae’s activity, which may involve either central upwelling of magma, or up-and-down “piston-like” vertical motion of the lake surface. Tidal forces, which are extreme at Io, could play a role as well. Future observations from Juno, particularly during the closest flybys, may indicate which mechanism is more plausible.

Hydroacoustic Monitoring of Mayotte Submarine Volcano during Its Eruptive Phase

Submarine volcanoes are more challenging to monitor than subaerial volcanoes. Yet, the large eruption of the Hunga Tonga-Hunga Ha’apai volcano in the Tonga archipelago in 2022 was a reminder of their hazardous nature and hence demonstrated the need to study them. In October 2020, four autonomous hydrophones were moored in the sound fixing and ranging channel 50 km offshore Mayotte Island, in the North Mozambique Channel, to monitor the Fani Maoré 2018–2020 submarine eruption. Between their deployment and July 2022, this network of hydrophones, named MAHY, recorded sounds generated by the recent volcanic activity, along with earthquakes, submarine landslides, marine mammals calls, and marine traffic. Among the sounds generated by the volcanic activity, impulsive signals have been evidenced and interpreted as proxy for lava flow emplacements. The characteristics and the spatio-temporal evolution of these hydroacoustic signals allowed the estimation of effusion and flow rates, key parameters for volcano monitoring. These sounds are related to the non-explosive quenching of pillow lavas due to the rapid heat transfer between hot lava and cold seawater, with this process releasing an energy equivalent to an airgun source as used for active seismic exploration. Volcano observatories could hence use autonomous hydrophones in the water column to detect and monitor active submarine eruptions in the absence of regular on-site seafloor survey.

Geology, chronology, and temporal evolution of basaltic to dacitic magma system in Raung volcano, East Java, Indonesia

Raung volcano, located within the Ijen UNESCO Global Geopark in East Java, poses a significant risk of volcanic hazard for nearby residents and visitors. Our study provides a framework to understand Raung long-term behavior and potential hazards by examining its stratigraphy, petrology, and temporal magma evolution. The erupted products of Raung vary from lava flow, pyroclastic density current (ignimbrite and block and ash flow), scoria fall, and pumice fall. Radiocarbon dating of charcoal samples within pyroclastic deposits and weathered sediments beneath tephra fall layers yield the age of 840 ± 30 BP to 370 ± 30 BP. It provides an important chronological marker that confirms the past VEI-4 to VEI-5 eruption around 1200 to 1600 CE. Petrological and geochemical data reveal that Raung magma composition ranges from basalt to dacite (48–64 wt% SiO2) and can be classified into two distinct magma types. Type 1 magma has med-K series, low Rb/Nb, and no Eu anomaly. Type 2 magma has high-K series, high Rb/Nb, and negative Eu anomaly. Evidence of disequilibrium features (e.g., reverse zoning, sieve texture, resorption texture, orthopyroxene mantled by clinopyroxene) and mingling texture, along with geochemical features, indicate magma mixing and many episodes of mafic magma replenishment. While the current volcanic activity is dominated by andesitic Strombolian eruption, the characteristics of Raung eruptive products suggest that past major Plinian eruptions (VEI 4–5) had occurred in both andesitic and dacitic magmatic systems, with greater VEI associated with dacitic composition. The study of Raung temporal evolution documented various eruptive behaviors related to its wide range of magma composition, thus providing an essential database for hazard assessment and mitigation.

The SPICE Project: Calibrated production rates of cosmogenic 3He and 21Ne in olivine and pyroxene from the 72 ka SP basalt flow, Arizona, USA

The formally named SP lava flow is a quartz-, olivine- and pyroxene-bearing basalt flow that is preserved in the desert climate of northern Arizona, USA. The flow has an 40Ar/39Ar age of 72 ± 4 ka (2σ) and has undergone negligible erosion and/or burial, making its surface an ideal site for direct calibration of cosmogenic nuclide production rates. Production rates for cosmogenic 3He (3Hec) and 21Ne (21Nec) have been determined from SP flow olivine and pyroxene in this study. The error-weighted mean, sea-level, high latitude (SLHL) total reference production rates of 3He in olivine and pyroxene have identical values of 135 ± 8 at/g/yr (2σx‾; standard error) using time-independent Lal (1991)/Stone (2000) (St) scaling factors. These production rates decrease to identical values of 130 ± 8 at/g/yr (2σx‾; standard error) when 3He measurements are standardized to the CRONUS-P pyroxene standard. The St-scaled, error-weighted mean, total reference production rates of 21Ne in olivine and pyroxene are 48.4 ± 2.9 at/g/yr and 26.5 ± 1.7 at/g/yr (2σx‾; standard error), respectively, increasing to 49.3 ± 3.0 at/g/yr and 27.0 ± 1.7 at/g/yr (2σx‾; standard error), respectively, when standardized to the CREU-1 quartz standard. 3He and 21Ne production rates (St) overlap within 2σ uncertainty with other St-scaled production rates in the literature. SLHL 3He and 21Ne production rates in SP flow olivine and pyroxene are nominally lower if time-dependentLm and Sa scaling factors are used. Olivine and pyroxene both have identical, error-weighted mean SLHL production rates of 127 ± 8 at/g/yr (2σx‾; standard error) using Lm scaling factors and CRONUS-P standardized 3He measurements. These production rates decrease to identical values of 110 ± 7 at/g/yr (2σx‾; standard error) for olivine and pyroxene when using Sa scaling factors. The Lm-scaled, error-weighted mean, total reference production rates of 21Ne in olivine and pyroxene are 48.1 ± 2.8 at/g/yr and 26.4 ± 1.7 at/g/yr (2σx‾; standard error), respectively, when standardized to the CREU-1 quartz standard. The error weighted mean, local 21Ne/3He production rate ratio in olivine is 0.358 ± 0.009 (2σx‾; standard error), which increases to 0.378 ± 0.012 when using CREU-1 standardized 21Ne production rates and CRONUS-P standardized 3He production rates. The error weighted mean, local 21Ne/3He production rate ratio in pyroxene is 0.197 ± 0.006, or 0.208 ± 0.008 when 21Ne and 3He are standardized to CREU-1 and CRONUS-P, respectively. The updated, CREU-1 standardized 21Nec rate (St) in SPICE quartz is 16.5 ± 1.1 at/g/yr. Production of 21Ne in coexisting SPICE olivine (ol), pyroxene (px), and quartz (qz) (standardized to CREU-1; Fenton et al., 2019; this study) yields error-weighted mean, local production rate ratios of 3.00 ± 0.13 (2σx‾) and 1.64 ± 0.08 (2σx‾) for 21Neol/21Neqz and 21Nepx/21Neqz, respectively. This study suggests that production rates of 3He and 21Ne in SPICE olivine and pyroxene agree well with St- and Lm-scaled global mean production rates in the literature. It also indicates that CRONUS-P and CREU-1 standardizations yield production rates in even stronger agreement with these global mean rates.

Pleistocene to recent evolution of Mocho-Choshuenco volcano during growth and retreat of the Patagonian Ice Sheet

Mocho-Choshuenco volcano (39.9°S, 72.0°W) produced ∼75 explosive eruptions following retreat of the >1.5-km-thick Patagonian Ice Sheet associated with the local Last Glacial Maximum (LGM, from 35 to 18 ka). Here, we extend this record of volcanic evolution to include pre- and syn-LGM lavas that erupted during the Pleistocene. We establish a long-term chronology of magmatic and volcanic evolution and evaluate the relationship between volcanism and loading/unloading of the Patagonian Ice Sheet via twenty-four 40Ar/39Ar and two 3He age determinations integrated with stratigraphy and whole-rock compositions of lava flows and glass compositions of tephra. Our findings reveal that the edifice is much younger than previously thought and preserves 106 km3 of eruptive products, of which 50% were emplaced immediately following the end of the penultimate glaciation and 20% after the end of the LGM. A period of volcanic inactivity between 37 and 26 ka, when glaciers expanded, was followed by the eruption of incompatible element-rich basaltic andesites. Several of these syn-LGM lavas dated between 26 and 16 ka, which crop out at 1500−1700 m above sea level, show ice contact features that are consistent with emplacement against a 1400- to 1600-m-thick Patagonian Ice Sheet. Small volume dacitic eruptions and two explosive rhyolitic eruptions dominate the volcanic output from 18 to 8 ka, when the Patagonian Ice Sheet began to retreat rapidly. We hypothesize that increased lithostatic loading as the Patagonian Ice Sheet grew prohibited dike propagation, thus stalling the ascent of magma, promoting growth of at least three discrete magma reservoirs, and enhancing minor crustal assimilation to generate incompatible element-rich basaltic andesitic to dacitic magmas that erupted between 26 and 17 ka. From an adjacent reservoir, incompatible element-poor dacites erupted from 17 to 12 ka. These lava flows were followed by the caldera-forming eruption at 11.5 ka of 5.3 km3 of rhyolite from a deeper reservoir atop which a silicic melt lens had formed and expanded. Subsequent eruptions of oxidized dacitic magmas from the Choshuenco cone from 11.5 to 8 ka were followed by andesitic to dacitic eruptions at the more southerly Mocho cone, as well as small flank vent eruptions of basaltic andesite at 2.5 and 0.5 ka. This complex history reflects a multi-reservoir plumbing system beneath Mocho-Choshuenco, which is characterized by depths of magma storage, oxidation states, and trace element compositions that vary over short periods of time (<2 k.y.).

Disparate impacts of the Eldgjá and Laki flood-lava eruptions

The Eldgjá eruption of ~ 939 AD is recognised as the largest in Iceland since Settlement, and ranks among the largest late-Holocene volcanic episodes on Earth. It disgorged > 21.0 km3 (Dense Rock Equivalent) of magma as lava flows (~ 19.7 km3) and tephra deposits (> 1.3 km3 DRE), comprising alternating phreatomagmatic (wet) and magmatic (dry) explosive phases. Tephra deposits up to four metres thick buried proximal areas, and extreme quantities of sulphur and other volatiles were released into the atmosphere. Little is known about the environmental and societal impacts of the eruption within Iceland as it took place during the initial decades of human settlement, and before written record-keeping in Iceland became prevalent. In this work, we review what is known of the Eldgjá eruption, making comparisons with the better documented Laki eruption of 1783–1784 AD (~ 15.1 km3 DRE). While the Eldgjá eruption was volumetrically greater, probably longer-lasting, and involved phreatomagmatic explosive phases, we reason that societal resilience to volcanic hazards was likely stronger in the 10th century compared with the 18th, reflecting differences in social and natural capital in Iceland. Accordingly, the impacts of the Eldgjá eruption cannot be inferred reliably from knowledge of the Laki episode and its aftermath.

Reconstruction of Hualca Hualca volcano (southern Peru) based on geomorphological and geological evidence and 40Ar/39Ar dating

The volcanic history of many of the western Central Andes volcanoes, including Hualca Hualca in the northern Ampato Volcanic Complex, remains poorly constrained. Based on an updated 1:50,000-scale geological map, new cross-sections of the Ampato Complex, a compilation of published dates, new geochemical data and 40Ar/39Ar ages, we present new insights into its volcanic evolution. Our study identifies 7 principal geological units (4 were not reported on the previous geologic map) and 8, mostly constructive, volcanic phases. The 40Ar/39Ar dating supports that Hualca Hualca began its formation during the Early Pleistocene (>1.6 Ma) with the establishment of an ancient stratovolcano. This volcano underwent a massive sector collapse to the north that created a U-shaped large amphitheater. This collapse likely resulted in the temporary damming of the Colca River, though no dates or associated deposits have been identified. Subsequent eruptions led to the formation of a smaller volcano along the amphitheater's scar that emplaced andesitic and dacitic lavas. This volcano dubbed modern Hualca Hualca holds the main summit. One of the longest lavas of this edifice reach the Colca valley and was previously dated at 610 ka. Sometime around 550 ka, volcanic activity migrated to the interior of the amphitheater forming the Nevado de Puye, Cruz del Condor, and Ahuashune domes that produced lavas of andesitic and dacitic composition. Around 164 ka a dacitic lava flow was emitted between Nevado del Puye and the base of the modern Hualca Hualca inside the horseshoe crater. The youngest known collapse of the Hualca Hualca complex involved parts of Nevado de Puye dome and the modern Hualca Hualca volcano, emplacing a debris avalanche that again dammed the Colca River and formed an upstream temporary lake that emplaced lacustrine and volcaniclastic deposits. After this collapse, no other volcanic deposit of the Hualca Hualca complex has been identified. Subsequently, glacial erosion during the local Last Glacial Maximum (17–16 ka) modified the volcanic landscape. Geochemical characteristics of Hualca Hualca suggest that their magmas were produced in a metasomatized mantle wedge and likely underwent crustal contamination during their ascent through the thick continental crust.

Mapping Lava Flows on Venus Using SAR and InSAR: Hawaiʻi Case Study

AbstractWe explore the potential for repeat‐pass SAR Interferometry (InSAR) correlation to track volcanic activity on Venus' surface motivated by future SAR missions to Earth's sister planet. We use Hawai'i as a natural laboratory to test whether InSAR can detect lava flows assuming orbital and instrument parameters similar to that of a Venus mission. Hawai'i was chosen because lava flows are frequent, and well documented by the United States Geological Survey, and because Hawai'i is a SAR supersite, where space agencies have offered open radar data sets for analysis. These data sets have different wavelengths (L, C, and X bands), bandwidths, polarizations, look angles, and a variety of orbital baselines, giving opportunity to assess the suitability of parameters for detecting lava flows. We analyze data from ALOS‐2 (L‐band), Sentinel‐1 (C‐band), and COSMO‐SkyMed (X‐band) spanning 2018 and 2022. We perform SAR amplitude and InSAR correlation analysis over temporal baselines and perpendicular baselines similar to those of a Venus mission. Fresh lava flows create a sharp, noticeable decrease in InSAR correlation that persists indefinitely for images spanning the event. The same lava flows are not always visible in the corresponding amplitude images. Moreover, noticeable decorrelation persists in image pairs acquired months after the events due to post‐emplacement contraction of flows. Post‐emplacement effects are hypothesized to last longer on the Venusian surface, increasing the likelihood of detecting Venus lava flows using InSAR. We argue for further focus on repeat‐pass InSAR capabilities in upcoming Venus missions, to detect and quantify volcanic activity on Earth's hotter twin.

New details on the volcanic and tectonic evolution of the Mesoarchaean Dominion Group with special reference to the Syferfontein Formation in the Ottosdal area (South Africa)

Abstract The ca. 2.96 Ga Dominion Group (DG) preserves the first subaerial volcano-sedimentary succession on the Kaapvaal Craton. Based on field and core observations, this study provides revised stratigraphic logs and geological maps from the area around Ottosdal that refine the understanding of the stratigraphic and tectonic evolution of these ancient rocks. Fluvial sandstone and conglomerate of the Rhenosterspruit Formation (RsF) were deposited on granite basement, followed by andesitic to basaltic volcanic rocks of the Rhenosterhoek Formation (RhF). These amygdaloidal andesitic to basaltic lava units show fragmentation around lava flows that may represent an indication of prevalent subaerial environment. However, local hyaloclastite and pillow lava units indicate periodic aqueous conditions. The Syferfontein Formation (SF) has the most extensive exposures in the Ottosdal area and represents the youngest volcanic unit of the DG. The porphyritic and spherulitic volcanic rocks tell a story of subaerial volcanism interspersed with periods of lacustrine deposition of sandstone and shale. The Witwatersrand Supergroup (WSG) overlies the DG along an angular unconformity. Folding affected the succession of the DG, WSG and the Ventersdorp Supergroup (Rietgat Formation). This event is reflected in small-scale folds and mullion structures in the central part of the study area and by larger scale north-northwest–south-southeast-striking anticlines and synclines. Folding was accompanied by northwest-southeast-striking thrust faulting, either during or shortly after the formation of the Ventersdorp Supergroup. In the study area, post-Ventersdorp deformation is restricted to east-northeast–west-southwest-striking faults.

Sensorweb Systems for Global High-Resolution Monitoring of Environmental Phenomena

Many science phenomena are difficult to observe because they occur infrequently and without warning. Over the course of the last 20 years, the concept of a “sensorweb,” or a network of interdependent instruments that autonomously coordinate to observe phenomena of interest, has been developed and implemented. In one use case, sensorwebs use in situ and low- to moderate-resolution sensors for event detection and pointable sensors with high spatial resolution for subsequent observation of targets, thus accomplishing efficient high-resolution monitoring. These sensorwebs have previously been implemented to study flood extent and volcanic lava flow. In the flood monitoring case, mostly remote sensors have been used for low-resolution flood detection, while more in-situ sensors have been used for volcanic activity detection in the volcano monitoring application. To improve these sensorwebs, we integrate commercial satellite constellations for high-resolution observations, resulting in higher spatial and temporal resolutions than the individual assets used in previous work. We also spatially extend sensorwebs to the global scale, produce a high volume of alerts, and automatically generate useful high-resolution data products. These resulting data products include surface water extent products for our flood sensorweb and volcanic lava classifiers for our volcano sensorweb. Our sensorwebs represent the state of the art in automatic acquisition and processing of data for environmental phenomenon monitoring. We demonstrate the capabilities of these improved sensorwebs in our new flood sensorweb and volcano sensorweb systems and describe ongoing efforts to utilize additional in-situ and spaced-based sensors and generate additional data products.

Insights into the development of small-volume long lava flows: A case study of the Coalstoun Lakes Volcanic Field, southeast Queensland, Australia

Long lava flows exceeding 50 km in length are usually produced during large-volume flood basalt eruptions (>100 to 10,000 km3) but can also occur from small to moderate-volume (<30 km3) basaltic eruptions in continental intraplate monogenetic volcanic fields. Eruptive volume, therefore, is not an a priori barrier to producing long lava flows. Key factors that promote long lava flows include efficient lava transport systems that minimise heat loss, long-lived and sustained effusion rates to maintain flow advancement, and lava flow across low topographic gradients (<1°-10°) with minimal topographic barriers.Here, we focus on an anomalously young and poorly studied basaltic monogenetic volcanic field in southeast Queensland, Australia, that formed part of the broader intraplate volcanism in eastern Australia since the Late Cretaceous. The Coalstoun Lakes Volcanic Field (CLVF) comprises three lava fields: the Barambah Basalt Flow Field, the Deep Creek Flow Field and the Hunters Hill Flow Field. Basalt from the Barambah Basalt Flow Field has been redated here by Ar40/Ar39 analysis of groundmass material, yielding a weighted mean age of 0.520 ± 0.016 Ma. The Barambah Basalt Flow Field contains most of the eruptive volume and has advanced up to 165 km from the vent. The Hunters Hill and the Deep Creek flow fields are comparatively smaller in volume and have advanced ∼30 and ∼ 20 km from the vent, respectively. Lava tubes are only known from proximal regions and do not appear to be a significant factor in promoting long run-out in the CLVF. Flow confinement and utilisation of existing drainage networks are features of both lava flow fields, and advancement down the sand-based and ephemeral Burnett River significantly promoted long run-out despite low topographic gradients.New whole-rock geochemical data on our CLVF samples indicates that all lavas are hawaiites, a common feature of other Quaternary long lava flows globally. Overall, there is some compositional variation, but a cryptic zonation is readily apparent in trace element abundances, which helps to further distinguish the flow fields as the products of separate but closely spaced eruptions. The combination of field and geochemical data indicates that the long lava flow of the Barambah Basalt Flow Field resulted from a sustained and relatively low effusion eruption, creating a pāhoehoe flow field that continuously advanced across the landscape, utilising a drainage system that guided lava flow and helped to circumvent any topographic barriers.

Geochemical and geochronological evidence of a Neoproterozoic island-arc on the easternmost Sierras Pampeanas. New U-Pb LA-ICP-MS data from amphibolites and metacarbonate depositional sequences

The first basement outcrops west of the Río de La Plata craton are metabasaltic and metasedimentary units of the Sierra Chica belt, part of the Eastern Sierras Pampeanas. These are orthoamphibolites and subordinate garnet-biotite gneisses and metacarbonate sequences that are intruded by Cambrian calc-alkaline and peraluminous rocks of the Pampean Orogeny. In accordance with one of the leading tectonic models for the region, new provenance data from this research suggest that the metabasaltic-metasedimentary association represents the proximal deposits of a Late Neoproterozoic island-arc. This contribution brings new geochemical and geochronological evidence from orthoamphibolites located on different sites along the Sierra Chica belt, which are interbedded with metacarbonate and gneisses outcrops, showing tholeiitic compositions, island-arc related tectonic settings, and Cryogenian to Ediacaran crystallization ages. Moreover, silicate-rich metacarbonates interbedded within the same sequences yielded a maximum depositional age of 569 Ma, reinforcing the assumed age for the sequence. All things considered, these rocks are interpreted as old basic lava flows and gabbro dikes linked to an island-arc activity, interspersed within the carbonatic and siliciclastic shelf sediments, together constituting the Neoproterozoic Córdoba Arc from the Sierra Chica belt. A depositional analogy with the present-day Caribbean island-arcs deposits suggests that these sequences could have been part of Oceanic Arc Depositional Systems (OADS) during the diachronous closure of the Goiás ocean and the final assembly of West Gondwana. Overlapping thermo-tectonic processes associated with the Pampean Orogeny are ubiquitous throughout all the studied outcrops, as evidenced by the petrography, the zircon morphology, and the U-Pb results, indicating a complex scenario towards a Late Cambrian slab break-off event.

Radar signatures of active lava flows on Venus

Radar signatures of active lava flows on Venus

Origins and nature of large explosive eruptions in the lower East Rift Zone of Kīlauea volcano, Hawaii: Insights from ash characterization and geochemistry

Several powerful explosive eruptions have taken place in the populated lower East Rift Zone of Kīlauea within the past ∼750 years. These have created distinctive landforms, including a tephra rim enclosing Puʻulena Crater immediately south of the Puna Geothermal Venture power station, a tuff cone at Kapoho Crater near the eastern cape of the Island of Hawaiʻi, and a set of littoral cones, the Sand Hill in Nānāwale, where the 1840 lava flow poured into the ocean. Kapoho Crater tuff cone is the largest of these recent pyroclastic features. Mineral, glass, and melt inclusion analyses of tuff cone ash and later fissure-related scoriaceous materials also found within the crater indicate slightly evolved basaltic magmas (1120–1130 °C) that are compositionally similar to parts of the effusive lower East Rift Zone eruptions in 1955 and 2018. Tuff cone magmas were stored at depths of ∼2.5–3.5 km and had pre-eruptive volatile contents (0.5–0.8 wt% H2O, 280–340 ppm CO2, 1400–1800 ppm S) similar to other Kīlauea eruptions (e.g., 1959, 1960), suggesting that internal magma properties were unlikely to account for the unusual explosiveness of this eruption. Tephra componentry, grain-size analyses, and field observations confirm that the cone grew during a phreatomagmatic eruption mostly of vitric ash, probably where a fissure opened across the coastline or shallow ocean floor nearby. Supporting this hypothesis is the identification of at least two genera of marine diatoms within tuff cone strata. Sand Hill littoral cone ash is also vitric like that of Kapoho Crater, but distinctly coarser with abundant fluidal ejecta represented. In contrast, the Puʻulena Crater eruption deposited lithic ash and related blocks with minor juvenile magmatic contribution; a phreatomagmatic eruption that was dominantly phreatic. Differences in eruption styles are related to unique mechanics that tephra analyses help us interpret. While powerful explosive eruptions in the lower East Rift Zone are rare, they present a definite future hazard for inhabitants in this part of Hawaii.

Pāhoehoe lava emplacement in Lon Reudle, Mull

The base of the Mull Lava Sequence, part of the Paleogene British Igneous Province, contains a variety of volcanic features; for example, small-scale filled lava tubes and toes that can be interpreted as large-scale inflated sheets from pāhoehoe lava flows. Here, we re-examine a previously reported unique outcrop found along the coastline of Lon Reudle, Mull, which can be better understood under that conceptual model. The outcrop is composed by multiple layers, with repeating porphyritic, poorly columnar jointed and vesicle-free layers, alternating with vesicle-rich layers with individual vesicles measuring up to 1 m. We reinterpret the outcrop as an individual inflated pāhoehoe lobe with an aggregated total thickness of at least 25 m. The estimated thickness of the upper crust of this lobe is 15 m, as the upper crust would account for 40–60% of the total volume of the flow, and the time required for this upper crust to form is c . 4 years. The alternation between vesicle-rich and vesicle-free layers is likely to be caused by instabilities of the suspended bubbles in the basaltic melt, forming a diapir with abundant evidence of bubble coalescence. Typical Hawaiian pāhoehoe lava flows have thickness of 1–3 m, whereas in other flood basalt provinces thickness can reach 75–80 m, suggesting that pāhoehoe structures are scale-independent. This is a key factor to take into account when reinterpreting other lava structures that have been found in the Paleogene British Igneous Province.

The Trans-Crustal Evolution of Miocene Magmatism Parental to Epithermal Mineralization in the Sierra Madre del Sur, Southern Mexico

Abstract Arc-related volcanism results from the interplay of magmatic processes occurring in trans-crustal systems that consolidate over time in a given location. Trans-crustal systems comprise extensive networks of magma reservoirs and conduits at different depths, wherein melts cyclically differentiate and segregate before reaching the surface. The study of these systems provides valuable insights into crustal-scale phenomena, such as the evolution of the continental crust and the formation of metallogenic regions. In this study, we address the trans-crustal magmatic evolution of lower Miocene magmatism parental to several intermediate-sulfidation epithermal deposits in the eastern Sierra Madre del Sur igneous province, southern Mexico. Using a multi-methodological approach, we document changes over ca. 1.1 Myr in the magmatic system that fed andesitic-to-felsic volcanism in this region. We employ whole-rock REE ratios and λ parameters—which are used to quantify the shape of a REE pattern—to track the involvement of pressure-sensitive minerals in the deep-crustal magmatic evolution. The andesitic rocks consist of lava flows, porphyries, and dikes that collectively show REE patterns suggestive of control by fractionated or residual (i.e. in crustal melting) amphibole and/or clinopyroxene. In contrast, the felsic rocks consist of rhyolitic–dacitic ignimbrites, domes, and dikes that show contrasting REE patterns suggestive of control by plagioclase, clinopyroxene, amphibole, and/or garnet. The distinct pressure-sensitive mineral assemblages in the andesitic and felsic rocks indicate that the locus of deep-crustal magma evolution varied within the middle–lower crust. These magmas were episodically injected into ephemeral shallow crustal reservoirs (shortly?) before being erupted, inducing a progressive thermomechanical maturation of the middle–upper crust. Meanwhile, low degrees of crustal assimilation occurred as recorded by Mesozoic inherited zircon ages and Sr–Nd–Pb radiogenic isotopes. An extensive middle–lower crustal magma evolution has been linked to the formation of porphyry Cu deposits (i.e. ‘fertile’ magmatism). Given that intermediate-sulfidation epithermal deposits may be genetically linked with porphyry Cu deposits, the documented processes could have contributed to the formation of epithermal deposits in the region. However, magmatic fertility proxies resemble those from infertile magmas worldwide. Since these proxies have been exclusively applied to porphyry-type deposits, our results highlight the importance of developing new geochemical exploration tools applicable to a wider range of ore deposits.

Tracing the Origin and Magmatic Evolution of the Rejuvenated Volcanism in Santa Clara Island, Juan Fernández Ridge, SE Pacific

Oceanic intraplate volcanoes sometimes experience late-stage eruptive activity known as rejuvenated volcanism, and contrasting interpretations for its petrogenesis depend on the compositional characteristics. In the Juan Fernández Ridge (JFR), a volcanic chain approximately 800 km in length emplaced on the Nazca Plate, some subaerial occurrences of rejuvenated volcanism have been recognized on the Robinson Crusoe and Santa Clara Islands, both part of the same deeply eroded shield volcano complex. This study aims to understand the origin and magmatic evolution of rejuvenated volcanism on Santa Clara Island, emplaced after ~2.15 Ma of quiescence above the shield sequence, mainly via the analysis of unpublished geochemical and isotopic data. Field reconnaissance identified two nearly coeval rejuvenated sequences on Santa Clara Island: Bahía W (BW) and Morro Spartan (MS), both formed by basanitic and picro-basaltic lava flows with brecciated levels and local intercalations of sedimentary and pyroclastic deposits. In comparison to the chemical signature of the preceding shield-building stage (comprised mainly of basalts and picrites), the two rejuvenated sequences exhibit a notable enrichment in incompatible elements, but the Sr, Nd, and Pb isotopes are very similar to the FOZO mantle endmember, with an apparent additional contribution of HIMU and EM1 components. The geochemistry of lavas revealed the involvement of various processes, including contamination by ultramafic xenoliths, high-pressure fractional crystallization of olivine and clinopyroxene, and potential partial assimilation of oceanic lithospheric components. While the oceanic lithosphere has been considered as a potential source, the isotopic data from Santa Clara lies outside of the mixing curve between depleted mantle (DM, here represented by the North Chile Rise and the East Pacific Rise) and the previous shield stage, suggesting that a lithospheric mantle is not the primary source for the rejuvenated stage volcanism. Therefore, we favor an origin of the rejuvenated volcanism from the mantle plume forming the JFR, supported by similarities in isotopic signatures with the shield stage and high values of 208Pb/204Pb (only comparable to San Félix—San Ambrosio in the vicinity of JFR), implying the presence of a regional source with radiogenic 208Pb/204Pb isotope ratios. In addition, isotopic variations are subparallel to the mixing line between HIMU and EM1 components, whose participation in different proportions might explain the observed trends. In conclusion, we propose that the source of the rejuvenated volcanism on Santa Clara Island is a heterogeneous mantle plume, the same one that fed the shield stage. The rejuvenated volcanism is derived from a secondary melting zone away from the main axis of the plume.

Submarine morphology of Pantelleria volcano: The interplay between volcanic and erosive-depositional processes modulated by sea-level fluctuations.

High-resolution multibeam data integrated with seismic reflection profiles are used to identify and characterize the main primary volcanic and erosive-depositional features along the submarine part (about the 80%) of the active Pantelleria volcano located in the Sicily Channel. Volcanic features include lava flows, cones and elongated ridges. Lava flows are mainly recognized over the insular shelf, while volcanic cones and ridges are mostly concentrated along the steep submarine flanks, especially along the wider SE and NW ones. A strong volcano-tectonic interaction is envisaged for their formation, as indicated by their preferential elongation or alignment along the (main) SE-NW and (secondary) SW-NE directions that have controlled the evolution of the whole volcanic edifice. Erosive-depositional features mainly include small-scale landslide scars and narrow gullies affecting the edge of the insular shelf and overlying submarine depositional terraces. Gullies sometimes merge downslope in larger channels, whose formation is primarily controlled by the distribution of volcanic features and/or shelf sectors characterized by different age or lithologies. Based on the marked morphological differences between the different flanks of the Pantelleria volcano, we infer an overall migration of the volcanic activity from SE to NW over time. This migration is apparently in contrast with the presence of a much wider but shallower NW insular shelf with respect to the SE one. This anomaly can be explained through a two-stage model, with the formation, in the NW sector, of a polygenic shelf rejuvenated by volcanic progradation during the last eustatic hemicycle. The different depths of the insular shelf edge around the island also provide insights on vertical deformations that affected the Pantelleria volcano during the Late-Quaternary.