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Constraining the timescales of pre-eruptive magmatic processes in active volcanic systems is paramount to understand magma chamber dynamics and the triggers for volcanic eruptions. Temporal information of magmatic processes is locked within the chemical zoning profiles of crystals but can be accessed by means of elemental diffusion chronometry. Mineral compositional zoning testifies to the occurrence of substantial temperature differences within magma chambers, which often bias the estimated timescales in the case of multi-stage zoned minerals. Here we propose a new Non-Isothermal Diffusion Incremental Step model to take into account the non-isothermal nature of pre-eruptive processes, deconstructing the main core-rim diffusion profiles of multi-zoned crystals into different isothermal steps. The Non-Isothermal Diffusion Incremental Step model represents a significant improvement in the reconstruction of crystal lifetime histories. Unravelling stepwise timescales at contrasting temperatures provides a novel approach to constraining pre-eruptive magmatic processes and greatly increases our understanding of magma chamber dynamics. Zoned crystals may reflect magma chamber dynamics, where changes in temperature, pressure and timescale before volcanic eruption may be measured. Petrone et al . develop a new Non-Isothermal Diffusion Incremental Step model to reconstruct crystal lifetime histories to constrain pre-eruptive magmatic processes.

Extreme meteorological events and anthropogenic influences determine important variations in microbial community composition. To know the extent of these variations, it is necessary to delve deeper into the geogenic factors to be considered as a baseline. The purpose of this study was to assess the effect of topographic characteristics and soil geochemistry on the spatial distribution of three Actinobacteria genera considered as molecular biomarkers of landforms belonging to Mediterranean environments. Given the important role that Actinobacteria play in the ecosystem, we performed a spatial distribution model of the genera Rubrobacter, Gaiella, and Microlunatus and investigated the fungi/bacteria ratio in a machine learning (ML)-based framework. Variable importance provided insight into the controlling factor of geomicrobial spatial distribution. The spatial distribution of the predicted Actinobacteria genera generally follows topographic constraints, mostly altitude. Rubrobacter was related to the slope aspect and lithium; Microlunatus was related to the topographic wetness index (TWI) and normalized difference water index (NDWI), as well as the fungi/bacteria ratio; and Gaiella was related to flow path and metals. Our results provide new information on the adaptation of Actinobacteria in Mediterranean areas and show the potential of using ML frameworks for the spatial prediction of OTUs distribution.

The active volcano of Ischia, an island off-shore the city of Naples, Southern Italy, has a discontinuous volcanic activity characterized by caldera-forming paroxysmal eruptions, lava flows, and lava domes, and thus offers the opportunity to study the complexity of magma storage, differentiation, and extraction mechanisms in a long-lived magma reservoir. The overall geochemical composition of erupted magmas varies from shoshonite to latite and trachyte/trachyphonolite. Their Sr and Nd, isotope composition variation is typical of subduction-related magmas, akin to other potassic magmas of the Neapolitan District, and there is a complete overlap of radiogenic isotope composition among shoshonite, latite, and trachyte/trachyphonolite. The lack of systematic radiogenic isotope covariation during differentiation suggests that the radiogenic isotope variability could be a signature of each magma pulse that subsequently evolved in a closed-system environment. Erupted magmas record a recurrent evolutionary process consisting of two-step fractional crystallization along similar liquid lines of descent for each magma pulse, suggesting near steady-state magma chamber conditions with balanced alternating periods of replenishment, differentiation, and eruption. The dominant role of fractionating feldspars determines a significant depletion of Sr (<10 ppm) coupled with high Rb/Sr (>200) in the residual trachyte magma. Several more-evolved trachytes have anomalous radiogenic 87Sr/86Sri (>0.707) coupled with high 87Rb/86Sr (>50), all other geochemical and isotopic characteristics being similar to normal 87Sr/86Sri trachytes at the same degree of evolution. This radiogenic Sr isotope signature is not consistent with assimilation of crustal material and demands for a time-related in-growth of 87Sr during storage within the magma chamber. Rb-Sr isochrons on separated mineral-groundmass pairs provide robust constraints on a prolonged pre-eruptive history ranging from a few tens to hundreds of thousands of years at relatively low temperature (∼750 °C). Remarkably, also normal trachytes with high 87Rb/86Sr (>200) yield a magma residence time from some 4 to 27 kyr, implying that the long-lived history of Ischia magmas is not limited to the anomalous 87Sr/86Sri trachytes. This long-lived history could be a characteristic feature of the magma chamber reservoir of this active volcano, which other volcanic products (i.e., shoshonite and latite) cannot disclose due to their lower Rb/Sr (i.e., low 87Sr in-growth rate) and higher magma storage temperature (>900 °C) (i.e., rapid Sr isotope homogenization via diffusion). The magma chamber dynamics of the active volcano of Ischia, probed on the basis of geochemical and radiogenic isotope tools, is consistent with recent models of complex magma chamber reservoirs made up of multiple discrete melt pockets, isolated by largely crystalline mush portions, maintained in a steady-state thermal flux regime with no mass exchange, and with reactivation shortly before eruption.

The presence of the olive tree in Tuscany, Italy, in its forms that have survived to the present day as an essential component of the landscape dates back many centuries. Global change is now threatening it. Therefore, it is important to find markers to enhance the olive tree environment in terms of its resilience. The aim of the research was to investigate the composition of soil bacteriomes in contrasting geochemical environments using a geochemistry approach based on the behavior of the REEs, inherited from parent rock material. Bacteriome assemblages and REE content were analyzed in 48 topsoils developed in six geochemical Tuscan environments. Combined geochemical, geoinformatic, and bioinformatic techniques highlighted the existence of four bacteriome assemblages depending on Light-REEs. Further results showed that the soil bioavailable fraction of REEs was related to parent rock materials, pH, and bacteriome composition. The most abundant bacteria were Microlunatus in graded fluvio-lacustrine soils, Gaiella in graded arenaceous soils, Bradyrizhobium in pyroclastic soils, and Rubrobacter in soils on gentle slopes of calcareous and carbonatic lithologies. This research represents a starting point to define new indicators able to assess the resilience of the olive trees in the Mediterranean landscape and characterize the territory of extra virgin olive oils.

An analytical protocol for high-precision, in situ microscale isotopic investigations is presented here, which combines the use of a high-performing mechanical microsampling device and high-precision TIMS measurements on micro-Sr samples, allowing for excellent results both in accuracy and precision. The present paper is a detailed methodological description of the whole analytical procedure from sampling to elemental purification and Sr-isotope measurements. The method offers the potential to attain isotope data at the microscale on a wide range of solid materials with the use of minimally invasive sampling. In addition, we present three significant case studies for geological and life sciences, as examples of the various applications of microscale 87Sr/86Sr isotope ratios, concerning (i) the pre-eruptive mechanisms triggering recent eruptions at Nisyros volcano (Greece), (ii) the dynamics involved with the initial magma ascent during Eyjafjallajökull volcano’s (Iceland) 2010 eruption, which are usually related to the precursory signals of the eruption, and (iii) the environmental context of a MIS 3 cave bear, Ursus spelaeus. The studied cases show the robustness of the methods, which can be also be applied in other areas, such as cultural heritage, archaeology, petrology, and forensic sciences.

This study investigates the magma plumbing system of the Miocene volcano shield stage of Tenerife (Canary Islands) through a geothermobarometric analysis of clinopyroxenes in ankaramite dykes and lavas from the Teno and Roque del Conde massifs. Ankaramites, characterized by a high phenocryst content of olivine and clinopyroxene, provide valuable insights into magma storage and transport processes. Two different methods have been applied to estimate the pressure and temperature of crystallization of clinopyroxenes: (i) a novel machine learning geothermobarometer and (ii) a geobarometer that uses their structural parameters (Vcell and VM1 polyhedron). The results yielded a pressure distribution between 0 and 8 kbar with a difference between clinopyroxene cores and rims, reflecting a multi-level plumbing system with evidence for the progressive ascent and crystallization of magmas. Further considerations of aluminium incorporation into the tetrahedral site and zonation patterns of clinopyroxene cores revealed three groups with distinct P–T paths, which are Low-T, High-T, and Low-P clinopyroxenes. Low-T clinopyroxenes are the largest ones (up to few centimetres in size) and exhibit resorbed and patchy zonation. This group represents a relatively cold crystal mush formed from a more hydrated magma, accumulated during a long residence time in disequilibrium conditions, as testified by crystal habits. High-T clinopyroxenes show normal zonation pattern and consist of small crystals (1–2 mm in size) directly crystallized from a less hydrated carrier magma during its ascent from depth (> 20 km b.s.l.). This magma, which tore away part of the crystal mush bodies, acted as the transport agent of these two suites of crystals up to the shallower crustal reservoirs (0–7 km). At these depths, clinopyroxene cores of the Low-P group crystallized in the same P–T conditions as those of the rim domain, in a chemical disequilibrium regime, proved by resorbed and patchy textures. In this scenario, ankaramites witness the occurrence of a heterogeneous cargo of clinopyroxenes that formed at different depths in the plumbing system of the Teno and Roque del Conde massifs during the volcano shield stage. The results of our research extend previous geothermobarometric studies and refine the understanding of the ankaramite plumbing system of Tenerife. Our data are consistent with the plumbing systems of other shield volcanoes of the Canary Islands and Hawaii and boost the application of machine learning approaches in revealing the anatomy of volcano plumbing systems.

Mantle xenoliths (lherzolites and a wehrlite) found in Cenozoic alkaline lavas from Azrou–Timahdite (Middle Atlas, Morocco) were petrographically studied with a particular emphasis on mineral chemistry. The most striking feature of these rocks is that plagioclase formed as a result of Al-rich spinel destabilization. This reaction is recorded in different steps and determined a variety of microstructures that allowed to identify four groups of xenoliths. Spinel chemistry generally becomes more refractory approaching the magma-xenolith interface. Geothermobarometry of both xenoliths and host lavas based on pyroxene equilibria and Forsterite—Anorthite—Ca Tschermak—Enstatite (FACE) geobarometer is consistent with a scenario in which spinel to plagioclase reaction was triggered at 0.7–1 GPa by hot (> 1100 °C) upraising magma in a mantle already characterized by a high heat flow (> 80 mW/m 2 ). The entrapment of the xenoliths by the host magma en route to the surface caused a chemical interaction resulting in orthopyroxene destabilization with the formation of anorthoclase. The high geothermal gradient outlined by the mineral chemistry of the xenoliths is consistent with the geodynamic setting of the area, where the lithosphere has been thinned due to the upraising of a mantle plume active since Mesozoic and producing the Mesozoic Central High Atlas basalts. Graphical abstract

Multiple magma storage levels are commonly recognized beneath magmatic systems and may play an important role in the processes leading to the build-up of large silicic magma chambers in the crust, with possible critical implications for the occurrence of explosive eruptions. Within such reservoirs, interactions between different magmas due to new recharge events are common processes, as demonstrated by the presence of mafic enclaves, which also reveal the occurrence of magma immiscibility conditions. In Nisyros (Greece), the two most recent eruptive events are the caldera-forming explosive eruption of the Upper Pumice (UP) and the following effusive activity of the Post Caldera Domes (PCD), which emplaced a thick pyroclastic deposit and six main lava domes, both hosting mafic components as crystal-rich clasts (CRCs) and enclaves, respectively. These two eruptions show differences in the abundance, petrographic characteristics, mineral chemistry, and geochemical and isotopic signatures of their mafic components, as well as in the extent of their mingling processes, indicating that the magma interaction conditions were different, possibly related to a change in the magma chamber dynamics and/or in the deeper feeding system structure. In this work, we investigated the textural characteristics and mineral chemistry of the products erupted by these two eruptive episodes, exploring their crystallization histories and the possible variations in physical conditions to reconstruct the structure of the plumbing system throughout the two phases of activities. Our results revealed the occurrence of evident mineral disequilibria within CRCs and enclaves related to their rapid crystallization due to the undercooling within the host. In the PCD systems, mineral disequilibria are also related to the extensive crystal transfer from the host to the enclaves and vice versa, generating mingling at the microscale, which increases with time. The application of geothermobarometers records progressively higher pressure from the UP to the PCD under similar temperature conditions. This indicates a deepening of the main eruptible reservoir, sampled by the PCD activity, after the UP–caldera collapse. Between the two periods, an interconnected evolved magma-rich system developed through new inputs of mafic melts that refilled and reheated the system, progressively mingling with the host and generating new conditions for the eruption.

The manufacturing of Italian maiolica (tin-glazed pottery) was extremely appreciated during the Middle Ages and Renaissance, leading to the production and collection of a rich cultural heritage. This pilot study aims to characterize the production technique and the origin of the lead used as a flux in a set of samples of maiolica glazes made in the area of Florence over a wide time span, ranging from the fifteenth to the nineteenth century. In particular, this is the first study that applies provenance analysis, using lead isotopes, to tin-glazed artefacts made in the site of Montelupo Fiorentino and by the Ginori manufactory in Doccia (Florence, Italy), both important production centres of ceramics in Italy. The samples were first analysed by scanning electron microscopy to characterize their layer structure and chemical composition. Lead isotope analysis was then performed by thermal ionization mass spectrometry and showed that the samples tend to be distributed into distinct groups according to their period of production. Moreover, the comparison with the lead isotope composition of the deposits of the European and circum-Mediterranean area from which lead was historically extracted showed that the isotopic composition of the samples differs from that of the Italian deposits, suggesting that lead was imported from abroad. The isotopic composition of all the investigated maiolica glazes is compatible with German ore deposits, in agreement with what is reported by the historical sources relating to the lead supply areas.

The Radicofani Volcano is characterised by few lava flows, a cinder cone and a denudated neck, and is part of the Tuscan Magmatic Province, the northernmost volcanic region of the Italian peninsula. In spite of the short time span of activity, a large time-dependant chemical and isotopic variability is observed. Most of the rocks of the Radicofani volcano are ultrapotassic shoshonites associated to younger basaltic andesites, found at the bottom of the neck. K 2 O contents are positively correlated with trace element and isotopic variations. Shoshonitic and high-K calc-alkaline rocks of the Radicofani volcano are significantly different from shoshonites occurring in association with leucite-bearing ultrapotassic rocks in the southernmost portion of the Roman Magmatic Province. The studied rocks are characterised by high, but variable, levels of incompatible trace elements with a subduction-related signature, with troughs at Ba, Ta, Nb, and Ti, and peaks at Cs, K, Th, U, and Pb. Initial values of 87 Sr/ 86 Sr range from 0.71333 to 0.71588, 143 Nd/ 144 Nd ranges from 0.512050 to 0.512183, while the lead isotope ratios vary between 18.672 and 18.716 for 206 Pb/ 204 Pb, 15.665 to 15.696 for 207 Pb/ 204 Pb, and 39.981 to 39.081 for 208 Pb/ 204 Pb. Ultrapotassic shoshonites show the highest incompatible trace element contents coupled with the highest 87 Sr/ 86 Sr and the lowest 143 Nd/ 144 Nd. On the basis of geochemical and isotopic signatures it is argued that magmas were generated in a modified lithospheric peridotitic source containing metasomatic veins generated by K-rich melts from recycled sediments within the mantle via subduction. A further metasomatic event generated by slab-derived fluids pervasively enriched the peridotitic source. Partial melting of the veins produced leucite-free ultrapotassic magmas (i.e. lamproite), and was triggered by rising of the isotherms after the orogenic front migrated eastward in the Italian Peninsula. Further rise of the isotherms induced larger degrees of partial melting inducing melting of the surrounding wall peridotite. The variation of the degree of partial melting of such a heterogeneous peridotitic source produced a wide spectrum of magma compositions, which mimic a mixing line between two components: ultrapotassic magma from partial melting of the metasomatic vein and a basaltic andesitic magma from partial melting of the surrounding peridotite.