Magma composition drives tremors during a volcanic eruption
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Escalation of caldera unrest indicated by increasing emission of isotopically light sulfur
Calderas are depressions formed by some of the largest volcanic eruptions. Their long-lived inter-eruptive periods are occasionally interrupted by phases of unrest, in which escalating seismicity, ground deformation and gas emissions raise concerns of potential volcano reawakening. However, interpretation of such physico-chemical signals is complicated by few examples of monitored unrest that culminated into eruption and by our fragmentary understanding of the drivers and timescales of caldera reactivation. Here we show that multi-decadal gas observations at the restless Campi Flegrei caldera in Italy record an unprecedented increase in isotopically light sulfur release from fumaroles since 2018. We then use hydrothermal gas equilibria and numerical simulations of magmatic degassing to propose that such a change in sulfur emissions results from decompression-driven degassing of mafic magma at ≥6 km depth, along with some extent of sulfur remobilization from hydrothermal minerals. Examination of a global dataset indicates that, despite the diversity in eruptive behaviour and tectonic setting, increasing sulfur output may be a common process during unrest escalation at calderas generally. Hence, our observations and models of sulfur behaviour may inform interpretations of unrest and hazard assessment at reawakening calderas and hydrothermal active volcanoes worldwide.
Perspective of soil carbon sequestration in Chilean volcanic soils
We analysed a large dataset consisting of 457 soil profiles of Andisols and Ultisols of volcanic origin compared to 60 non-volcanic soils. We hypothesised that soil pH has a greater impact on the development of Al-organomineral complexes in volcanic soils compared to non-volcanic soils, in the latter, the silt and clay fractions play a crucial role. Soil pH >4.5 strongly influenced the formation of Al-organomineral complexes in volcanic soils, while an increase in allophane content led to a decrease in SOC. Ultisols with more crystalline clays, such as halloysite and disordered kaolinite, the pH had a weaker impact and there was no effect on non-volcanic soils. Instead, a positive correlation (R2 = 0.63, p < 0.01) was found between silt and clay and SOC in non-volcanic soils, supporting our second hypothesis. Soil pH played a significant role in the interplay between Al-organomineral complexes and allophane formation, while crystalline mineralogy has a direct effect on SOC levels in non-volcanic soils.
Genesis and timing of KREEP-free lunar Mg-suite magmatism indicated by the first norite meteorite Arguin 002
There is ongoing debate about whether lunar magnesian suite (Mg-suite) magmatism was a global, nearly synchronous event with a genetic link to potassium, rare-earth element and phosphorus components (KREEP). Arguin 002, the first whole-rock meteorite classified as a lunar norite, offers a unique opportunity to explore the genesis and timing of Mg-suite rocks. Here we investigated the petrology, mineralogy, geochemistry, and chronology of Arguin 002, revealing it to be an evolved, KREEP-free Mg-suite rock with chemical similarities to atypical Apollo-15 Fe-norites. It likely formed through plutonic magmatism originating from low-degree partial melting of a deep, KREEP-free mantle source and has a 207Pb/206Pb age of 4341.5 ± 9.3 Ma. The potential source of Arguin 002 is within the South Pole-Aitken basin, near the Chang’e-6 landing site. These findings indicate that Mg-suite magmatism was a global and nearly synchronous event, potentially driven by rapid global mantle overturn.
Past hydroclimate extremes in Europe driven by Atlantic jet stream and recurrent weather patterns
The jet stream over the Atlantic–European sector is relevant for weather and climate in Europe. It generates temperature extremes and steers moisture and flood-propelling weather systems to Europe or facilitates the development of atmospheric blocks, which can lead to drought. Ongoing climate change may alter the jet characteristics, affecting weather extremes. However, little is known about the past interannual-to-decadal variability of the jet stream. Here we analyse the strength, tilt and latitude of the Atlantic–European jet from 1421 to 2023 in an ensemble of monthly and daily reconstructions of atmospheric fields. We compare the variability of these jet indices with blocking frequency and cyclonic activity data and with drought and flood reconstructions in Europe. Summer drought is enhanced in Central Europe in periods with a poleward-shifted jet. An equatorward-shifted jet associated with decreased blocking leads to frequent floods in Western Europe and the Alps, particularly in winter. Recurrent weather patterns causing floods often characterize an entire season, such that an association between peak discharge and jet indices is seen on seasonal or even annual scales. Jet strength and tilt are significantly influenced by volcanic eruptions. Our 600-year perspective shows that recent changes in the jet indices are within the past variability and cannot be drivers of increasing flood and drought frequency.
A review of micro-resolved crystochemical and mechanical probes for sustainable cement-based material studies
Exploring sustainable alternative constituents is a key pathway to carbon-neutralization of concrete, but often limited to insufficient understandings of how they interact with conventional concrete components at microscale. In this paper we reviewed the most cutting-edge microprobes used for such purposes, from both laboratory setup to synchrotron radiation-based techniques. We also provided practical guidelines on sample preparation and result analysis, which could benefit researchers who plan to adopt these methods
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