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First measurements of the Fe oxidation state of spinel inclusions in olivine single crystals from Vulture (Italy) with the in situ synchrotron micro-Mössbauer technique
No full textThe redox state of the Earth’s upper mantle (i.e., oxygen fugacity, fO2 ) is a key variable that influences
numerous processes occurring at depth like the mobility of volatile species, partial melting, and metasomatism.
It is linked to the oxidation state of peridotite rocks, which is normally determined through the available oxythermobarometers
after measuring the chemical composition of equilibrated rock-forming minerals and the Fe3C in
redox-sensitive minerals like spinel or garnet. To date, accurate measurements of Fe3C =
P
Fe in peridotites have
been limited to those peridotites (e.g., harzburgites and lherzolites) for which an oxythermobarometer exists and
where spinel (or garnet) crystals can be easily separated and measured by conventional 57Fe Mössbauer spectroscopy.
Wehrlitic rocks have been generally formed by the interaction of a lherzolite with carbonatitic melts
and, therefore, have recorded the passage of (metasomatic) fluids at mantle conditions. However, no oxythermobarometer
exists to determine their equilibrium fO2 .
The aim of this study was to retrieve the fO2 of the mantle beneath Mt. Vulture volcano (Italy) through the
study of a wehrlitic lapillus emitted during the last eruption ( 140 kyr ago) that contain olivines with multiple
tiny spinel inclusions with sizes <40 μm. To our knowledge, the Fe oxidation state of these inclusions has been
never determined with the Mössbauer technique due to their small sizes.
Here, we present measurements of the Fe3C =
P
Fe using in situ synchrotron Mössbauer spectroscopy coupled
with chemical and spectroscopic analysis of both host olivine and spinel inclusions.
The results show Fe3C =
P
Fe ratios of 0.03–0.05 for olivine and 0.40–0.45 for the included spinels, the latter
of which appear higher than those reported in literature for mantle spinel harzburgites and lherzolites. Given the
evidence of the mantle origin of the trapped spinels, we propose that the high fO2 (between 0.81 and 1.00 log
above the fayalite–magnetite–quartz buffer; FMQ) likely results from the interaction between the pristine spinel
lherzolite and a CO2-rich metasomatic agent prior to the spinel entrapment in olivines at mantle depths.Published665–6783V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcaniciJCR Journa
Moho depths beneath the European Alps: a homogeneously processed map and receiver functions database
No full textWe use seismic waveform data from the AlpArray Seismic Network and three other temporary seismic networks, to perform receiver function (RF) calculations and time−to−depth migration to update the knowledge of the Moho discontinuity beneath the broader European Alps. In particular, we set up a homogeneous processing scheme to compute RFs using the time-domain iterative deconvolution method and apply consistent quality control to yield 112,205 high-quality RFs. We then perform time−to−depth migration in a newly implemented 3D spherical coordinate system using a European-scale reference P and S wave velocity model. This approach, together with the dense data coverage, provide us with a 3D migrated volume, from which we present migrated profiles that reflect the first-order crustal thickness structure. We create a detailed Moho map by manually picking the discontinuity in a set of orthogonal profiles covering the entire area. We make the RF dataset, the software for the entire processing workflow, as well as the Moho map, openly available; these open-access datasets and results will allow other researchers to build on the current study.Published2117–21381T. Struttura della TerraJCR Journa
Deep well new data in the area of the 2022 Mw 5.5 earthquake, Adriatic Sea, Italy: In situ stress state and P-velocities
No full textFollowing the Mw 5.5 earthquake of 9 November 2022 that occurred along the
Adriatic coast of Italy and the related seismic sequence, we analysed new data
from deep wells drilled in recent years by ENI S.p.A. Specifically, we calculated the
horizontal stress orientations from breakouts recognized in three wellbores,
determined the P-wave velocities for the first 5 km of crust from 12 well sonic
records, and then calculated the vertical stress values in the area. Our results,
indicating orientations of the present-day stress field of ~N130 and ~N040 for
minimum and maximum horizontal stress, respectively, are consistent with the
seismic sequence focal solutions. Thrust faulting focal solutions occurring at a
hypocentral depth between 5 and 10 km, show minimum horizontal stress
oriented at ~N140, which is also in agreement with the compressive tectonics
of the area and the known seismogenic sources. The crustal P-wave velocities vary
as a function of both the lithology crossed and the geological-structural location
of the wells, suggesting several velocity patterns in a confined area. The average
vertical stress for the investigated area, inferred from the velocity-derived density,
shows values of ~100 MPa at a depth of 4.5 km, with a gradient varying from 21 to
23 MPa/km. The obtained in situ stress measurements indicate that no stress
regime changes or temporal rotations have been observed in the past 50 years
throughout the entire area. The new stress indicators fill a geographical gap
between the northern and southernmost existing data coherently with a
compressive stress regime.Published11649292T. Deformazione crostale attiva4T. Sismicità dell'ItaliaJCR Journa
Application of the EEPAS earthquake forecasting model to Italy
No full textThis article has been accepted for publication in Geophysical Journal International ©:The Author(s) 2023. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Uploaded in accordance with the publisher's self-archiving policy.
All rights reserved.The Every Earthquake a Precursor According to Scale (EEPAS) forecasting model is a space– time point-process model based on the precursory scale increase (ψ ) phenomenon and associated predictive scaling relations. It has been previously applied to New Zealand, Cal- ifornia and Japan earthquakes with target magnitude thresholds varying from about 5–7. In all previous application, computations were done using the computer code implemented in Fortran language by the model authors. In this work, we applied it to Italy using a suite of computing codes completely rewritten in Matlab. We first compared the two software codes to ensure the convergence and adequate coincidence between the estimated model parameters for a simple region capable of being analysed by both software codes. Then, using the rewritten codes, we optimized the parameters for a different and more complex polygon of analysis using the Homogenized Instrumental Seismic Catalogue data from 1990 to 2011. We then perform a pseudo-prospective forecasting experiment of Italian earthquakes from 2012 to 2021 with Mw ≥ 5.0 and compare the forecasting skill of EEPAS with those obtained by other time in- dependent (Spatially Uniform Poisson, Spatially Variable Poisson and PPE: Proximity to Past Earthquakes) and time dependent [Epidemic Type Aftershock Sequence (ETAS)] forecasting models using the information gain per active cell. The preference goes to the ETAS model for short time intervals (3 months) and to the EEPAS model for longer time intervals (6 months to 10 yr).Published1681–1700OST4 Descrizione in tempo reale del terremoto, del maremoto, loro predicibilità e impattoJCR Journa
Obsidian Artifacts from Multiple Sources and Subsources at Valdesi in Western Sicily
No full textForty-two obsidian artifacts excavated at the site of Valdesi in western Sicily were analyzed
to determine their geological sources and to reconstruct trade patterns. Non-destructive analysis was
performed using a portable, non-destructive X-ray fluorescence spectrometer, with the calibrated
element’s composition values compared directly with a dataset of geological samples from the
Mediterranean and European sources that were analyzed with the same instrument. The results,
based on straightforward X-Y graphs using the trace elements Rb, Sr, Y, Zr, and Nb, showed the
presence of obsidian from two subsources on Lipari (Gabellotto Gorge, Canneto Dentro), two on
Pantelleria (Balata dei Turchi, Lago di Venere), and one on Sardinia. The majority coming from Lipari
coincided with the location of Valdesi, and nearly 20% came from Pantelleria, both consistent with
the overall distribution patterns for Sicily, while the one from Sardinia is a unique discovery. These
results are discussed in terms of the time period and context for Valdesi, as well as the open-water
and land-based routes that must have been taken.Published1093OSA4: Ambiente marino, fascia costiera ed Oceanografia operativaJCR Journa
Ultra-sensitive voltage-controlled skyrmion-based spintronic diode
No full textWe have designed a passive spintronic diode based on a single skyrmion stabilized in a magnetic tunnel junction and studied its dynamics induced by voltage-controlled magnetic anisotropy (VCMA) and Dzyaloshinskii-Moriya interaction (VDMI). We have demonstrated that the sensitivity (rectified output voltage over input microwave power) with realistic physical parameters and geometry can be larger than 10 kV W-1which is one order of magnitude larger than diodes employing a uniform ferromagnetic state. Our numerical and analytical results on the VCMA and VDMI-driven resonant excitation of skyrmions beyond the linear regime reveal a frequency dependence on the amplitude and no efficient parametric resonance. Skyrmions with a smaller radius produced higher sensitivities, demonstrating the efficient scalability of skyrmion-based spintronic diodes. These results pave the way for designing passive ultra-sensitive and energy efficient skyrmion-based microwave detectors.Published375202OSA5: Energia e georisorseJCR Journa
Clustering of eruptive events from high-precision strain signals recorded during the 2020–2022 lava fountains at the Etna volcano (Italy)
No full textLava fountains at the Etna volcano are spectacular eruptive events characterized by powerful jets that expel hot mixtures of solid particles and volcanic gases, easily reaching stratospheric heights. Ash dispersal and fallout of solid particles affect the inhabited areas, often causing hazards both to infrastructure and to air and vehicular traffic.
We focus on the extraordinary intense and frequent eruptive activity at Etna in the period of December 2020–February 2022, when more than 60 lava fountain events occurred with various ejected magma volume and lava fountain height and duration. Differences among the events are also imprinted in tiny ground deformations caught by strain signals recorded concurrently with the lava fountain events, reflecting a strict relationship with their evolution. To characterize this variability, which denotes changes in the eruption style, we clustered the lava fountain events using the k-means algorithm applied on the strain signal. A novel procedure was developed to ensure a high-quality clustering process and obtain robust results. The analysis identified four groups of strain variations which stand out for their amplitude, duration and time derivative of the signal. The temporal distribution of the clusters highlighted a transition in different types of eruptions, thus revealing the importance of clustering the strain variations for monitoring the volcano activity and evaluating the associated hazards.Published1743–17545V. Processi eruttivi e post-eruttiviJCR Journa
Hydrogeochemistry and Isotopic Composition of Waters in the Renella Cave (Central Italy): New Insights into Groundwater Dynamics
No full textThis article presents data from monthly monitoring carried out on cave and stream waters belonging to the Renella Cave karst system from September 2020 to April 2022. Additionally, old data pertaining to cave waters from previous published work are discussed. The aim is to develop a dataset for future climatic and hydrological studies on the Renella Cave and its surface recharges. Water samples were collected and analyzed for major ions, δ18O and δ2H, on water molecules. The cave sump water level, water temperature, and electrical conductivity were continuously measured and compared to the precipitation data. Additionally, air temperature and pressure inside and outside the cave were also monitored. The classification based on the Piper-Hill diagram indicated that both stream and cave waters belong to the bicarbonate-alkaline earth hydrochemical facies, indicating that their chemism is essentially determined by the dissolution of the Grezzoni Fm. Isotopic data suggest that both stream and cave waters have a meteoric origin, and their variability mainly depends on underground homogenization. Hydrogeochemistry, isotopic composition, and the monitoring data allowed a deeper understanding of the cave karst system, and identified an underground circulation network that is fragmented into independent parts.Published1764OSA2: Evoluzione climatica: effetti e loro mitigazioneJCR Journa
Progressive underplating of mafic material at mid-crustal depth beneath Ischia volcano, Italy
No full textThe destructive (Mw 3.9) earthquake of 21 August 2017 re-opened the question on where magma resides at the Ischia island volcano. The peculiar complexity of the seismic source initiated the debate on the involvement of fluid-related processes, but the magmatic origin of the event remains uncertain. Here we use ground displacement and broadband seismic data to investigate the magmatic system of Ischia volcano, where progressive underplating of mafic material at mid-crustal depth feeds the deep structures, which are characterized by exceptionally high seismic velocity and are connected with a shallow crystal mush. Although no direct evidence of large molten volumes was found, strong anisotropy suggests that the crystal mush is pervaded by magma-intruded dykes. We propose that the 2017 event was due to a negative tensile deformation caused by depressurization of supercritical fluids along a shallow southwest (SW-)-dipping fault defined by receiver functions (RFs) data, which acted as a valve regulating the overpressure of deep magmatic fluids.Published303JCR Journa
CO2 Reaction-Diffusion Experiments in Shales and Carbonates
No full textThe evaluation of caprock integrity and reservoir efficiency is critical for safe CO2 geological
storage management. It is therefore important to investigate geochemical reactions between CO2-
rich fluids and host rocks and their contribution in retaining CO2 at depth. This study deals with
diffusive reaction experiments on shales and carbonate samples cored from an offshore structure
in the Malaysian basin, a potential target for CO2-enhanced gas recovery. The aim is to evaluate
the CO2 reaction front velocity in a typical shaly caprock and the mineral response of the reservoir.
Rock samples were characterized in terms of texture, chemistry, and mineralogy by X-ray diffraction,
electron microscopy (SEM), microanalysis (EDS), infrared spectroscopy (FT-IR), rock geochemistry
(XRF), and mercury injection capillary permeability (MICP). Performed analyses show mineralogical
alteration induced by CO2 as it penetrated into the samples. Carbonate dissolution and weathering
of pyrite to form secondary carbonates belonging to siderite-ankerite series were observed along
two reaction fronts. Estimated diffusion coefficients of CO2 are two orders of magnitude lower
than CO2(aq) molecular diffusion in pure water and from half to an order of magnitude lower than
diffusivity computed on unaltered sample, highlighting the important effect of gas–water–rock
reactions on the CO2(aq) diffusivities in shales and carbonates. Results obtained in this study provide
an insight regarding the effect of geochemical reactions on CO2 transport and represent a further
discussion point on the diffusion coefficients.This research was funded by PETRONAS Research Sdn. Bhd for the Project “Methodology
of Mitigation CO2 Leakages (Overburden Study)”.Published561TR. GeorisorseJCR Journa