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Soligo, M.
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- PublicationOpen AccessReal-time setup to measure radon emission during rock deformation: implications for geochemical surveillanceLaboratory experiments can represent a valid approach to unravel the complex interplay between the geochemical behaviour of radon and rock deformation mechanisms. In light of this, we present a new real-time experimental setup for analysing in continuum the alpha-emitting Rn-222 and Rn-220 daughters over variable stress-strain regimes. The most innovative segment of this setup consists of the radon accumulation chamber obtained from a tough and durable material that can host large cylindrical rock samples. The accumulation chamber is connected, in a closed-loop configuration, to a gas-drying unit and to a RAD7 radon monitor. A recirculating pump moves the gas from the rock sample to a solid-state detector for alpha counting of radon and thoron progeny. The measured radon signal is enhanced by surrounding the accumulation chamber with a digitally controlled heating belt. As the temperature is increased, the number of effective collisions of radon atoms increases favouring the diffusion of radon through the material and reducing the analytical uncertainty. The accumulation chamber containing the sample is then placed into a uniaxial testing apparatus where the axial deformation is measured throughout a linear variable displacement transducer. A dedicated software allows obtaining a variety of stress-strain regimes from fast deformation rates to long-term creep tests. Experiments conducted with this new real-time setup have important ramifications for the interpretation of geochemical anomalies recorded prior to volcanic eruptions or earthquakes.
49 23 - PublicationOpen AccessDeliverable # 3.01.1 Technical report illustrating the results obtained in the Crotone Peninsula based on geological and InSAR data(2010-05-31)
; ; ; ; ; ; ; ; ; ; ; ;Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Barba, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Fracassi, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Kastelic, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Tiberti, M. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Vannoli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Stramondo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Tolomei, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Soligo, M.; Università di Roma Tre ;Tuccimei, P.; Università di Roma Tre; ; ; ; ; ; ; ; ; ; This work was aimed at collecting data to estimating the rate of uplift over several temporal scales. The analysis includes a very short-term analysis (tens of years) of InSAR data, a middle-term analysis of Holocene geological data, and a long-term analysis of Middle-Late Pleistocene geological data. After a preliminary reconnaissance in a large area, all final datasets focus strictly on the area of the Crotone Peninsula. The techniques applied span from Small Baseline Subset Interferometric SAR, to classic geomorphic and stratigraphic analysis aided by radiocarbon and U/Th dating.366 758 - PublicationRestrictedGeographically weighted regression and geostatistical techniques to construct the geogenic radon potential map of the Lazio region: A methodological proposal for the European Atlas of Natural Radiation(2017-01)
; ; ; ; ; ; ; ; ; ; ; ; ;In many countries, assessment programmes are carried out to identify areas where people may be exposed to high radon levels. These programmes often involve detailed mapping, followed by spatial interpolation and extrapolation of the results based on the correlation of indoor radon values with other parameters (e.g., lithology, permeability and airborne total gamma radiation) to optimise the radon hazard maps at the municipal and/or regional scale. In the present work, Geographical Weighted Regression and geostatistics are used to estimate the Geogenic Radon Potential (GRP) of the Lazio Region, assuming that the radon risk only depends on the geological and environmental characteristics of the study area. A wide geodatabase has been organised including about 8000 samples of soil-gas radon, as well as other proxy variables, such as radium and uranium content of homogeneous geological units, rock permeability, and faults and topography often associated with radon production/migration in the shallow environment. All these data have been processed in a Geographic Information System (GIS) using geospatial analysis and geostatistics to produce base thematic maps in a 1000 m × 1000 m grid format. Global Ordinary Least Squared (OLS) regression and local Geographical Weighted Regression (GWR) have been applied and compared assuming that the relationships between radon activities and the environmental variables are not spatially stationary, but vary locally according to the GRP. The spatial regression model has been elaborated considering soil-gas radon concentrations as the response variable and developing proxy variables as predictors through the use of a training dataset. Then a validation procedure was used to predict soil-gas radon values using a test dataset. Finally, the predicted values were interpolated using the kriging algorithm to obtain the GRP map of the Lazio region. The map shows some high GRP areas corresponding to the volcanic terrains (central-northern sector of Lazio region) and to faulted and fractured carbonate rocks (central-southern and eastern sectors of the Lazio region). This typical local variability of autocorrelated phenomena can only be taken into account by using local methods for spatial data analysis. The constructed GRP map can be a useful tool to implement radon policies at both the national and local levels, providing critical data for land use and planning purposes.111 3 - PublicationRestrictedContrasting radon background levels in volcanic settings: Clues from 220Rn activity concentrations measured during long-term deformation experiments(2013)
; ; ; ; ; ;Scarlato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Tuccimei, P.; Università Roma Tre ;Mollo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Soligo, M.; Università Roma Tre ;Castelluccio, M.; Università Roma Tre; ; ; ; To better understand the mechanisms leading to different radon background levels in volcanic settings, we have performed two long-term deformation experiments of 16 days using a real-time setup that enables us to monitor any variation of radon activity concentration during rock compression. Our measurements demonstrate that, in the case of highly porous volcanic rocks, the emanating power of the substrate changes as a function of the volcanic stress conditions. Constant magmatic pressures, such as those observed during dike intrusions and hydrothermal fluid injections, can result in pervasive pore collapse that is mirrored by a significant radon decrease until a constant emanation is achieved. Conversely, repeated cycles of stress due to, for example, volcano inflation/deflation cycles, cause a progressive radon increase a few days (but even weeks and months) before rupture. After rock failure, however, the formation of new emanation surfaces leads to a substantial increase of the radon signal. Our results suggest that surface deformation in tectonic and volcanic settings, such as inflation/ deflation or constant magmatic pressures, have important repercussions on the emanating power of volcanic substrates.206 26 - PublicationRestrictedIncrease in radon emission due to rock failure: An experimental study(2011-07-22)
; ; ; ; ; ; ; ; ;Mollo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Tuccimei, P.; Università “Roma Tre" ;Heap, M.; CNRS, EOST ;Vinciguerra, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Soligo, M.; Università “Roma Tre" ;Castelluccio, M.; Università “Roma Tre" ;Scarlato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Dingwell, D.; ; ; ; ; ; ; Radon anomalies are commonly observed prior to dynamic failure in the crust and are interpreted as cracking of the medium, thus attracting considerable attention in understanding the precursory phenomena of earthquakes and volcanic activity. In this study we have compared the starting radon emissions from low porosity crystalline lava (phonolite) samples with those from damaged and failed samples. The damaged sample was loaded up to just beyond the end of the linear elastic phase, as evidenced by the output of AE energy, the increase in total porosity and a decrease in P‐wave and S‐wave velocity relative to the intact sample. Whereas, the failed sample showed deformation behaviour characteristically brittle with increasing values of AE output and porosity as the sample approached macroscopic failure. Radon measurements have evidenced that dilatational microcracking of deformed sample produced no significant variation in radon emanation with respect to the intact sample. In contrast, after macroscopic failure, radon emanation drastically increased. Therefore, major finding from this study is that, in the case of low porosity and relatively high strength crystalline lavas, the development of a macroscopic fracture provides new large exhaling surface resulting in a substantial increase in radon emission rate.199 32 - PublicationOpen AccessA new test for equilibrium based on clinopyroxene-melt pairs: Clues on the solidification temperatures of Etnean alkaline melts at post-eruptive conditions(2013)
; ; ; ; ; ;Mollo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Putirka, K.; California State University, Fresno, Department of Earth and Environmental Sciences, 2576 E. San Ramon Avenue, MS/ST25, Fresno, California 93740-8039, U.S.A. ;Misiti, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Soligo, M.; Dipartimento di Scienze Geologiche, Università “Roma Tre”, Largo San Leonardo Murialdo 1, 00146 Roma, Italy ;Scarlato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; We have performed new global regression analyses to calibrate a model of equilibrium between clinopyroxene and co-existing melt. Then we have applied this model to a restricted but important range of clinopyroxene and melt compositions from Mt. Etna volcano. The degree of disequilibrium is determined through the comparison between components “predicted” for clinopyroxene via regression analyses of clinopyroxene-liquid pairs in equilibrium conditions, with those “measured” in the analyzed crystals. The model is tested using compositions not included into the calibration dataset, i.e., clinopyroxene-melt pairs obtained from equilibrium and cooling rate experiments conducted at ambient pressure on an Etnean trachybasalt. The experiments were duplicated at the NNO+1.5 and QFM oxygen buffering conditions estimated for magmas at Mt. Etna. Both equilibrium and disequilibrium clinopyroxene-melt pairs from the experiments were also used as input data for one of the most recent thermometers based on the Jd-DiHd exchange reaction. Results from calculations indicate that, under rapid cooling rate conditions, clinopyroxenes do not equilibrate with the melt. Consequently, the thermometers predict higher crystallization temperatures compared to the final experimental temperature, prior to rapid quenching of the experiment. The systematic difference between expected and measured compositions and temperatures allows us to calibrate a model that describes undercooling based on disequilibrium exchange reactions. We use this new tool to estimate the thermal history of naturally cooled lava flows and dikes at Mt. Etna volcano.257 1305 - PublicationRestrictedInteraction between regional and local tectonic forcing along a complex Quaternary extensional basin: Upper Tiber Valley, Northern Apennines, Italy(2014-09)
; ; ; ; ; ; ; ; ;Pucci, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Mirabella, F.; Dipartimento di Fisica e Geologia, Universit a di Perugia, Piazza dell'Universit a, 00123 Perugia, Italy ;Pazzaglia, F.; Dipartimento di Fisica e Geologia, Universit a di Perugia, Piazza dell'Universit a, 00123 Perugia, Italy ;Barchi, M. R.; Dipartimento di Fisica e Geologia, Universit a di Perugia, Piazza dell'Universit a, 00123 Perugia, Italy ;Melelli, L.; Dipartimento di Fisica e Geologia, Universit a di Perugia, Piazza dell'Universit a, 00123 Perugia, Italy ;Tuccimei, P.; Science Department, Section of Earth Science, University Roma 3, Largo San L. Murialdo, 00146 Rome, Italy ;Soligo, M.; Science Department, Section of Earth Science, University Roma 3, Largo San L. Murialdo, 00146 Rome, Italy ;Saccucci, L.; Dipartimento di Fisica e Geologia, Universit a di Perugia, Piazza dell'Universit a, 00123 Perugia, Italy; ; ; ; ; ; ; In extending areas undergoing regional tectonic uplift, the persistence of subsidence at a normal-fault hanging-wall depends on the competition between regional and local tectonic effects. When regional uplift exceeds the subsidence of the hanging-wall block, denudation prevails at both the hanging-wall and the foot-wall. When local tectonic subsidence exceeds regional uplift, sedimentation occurs over the hanging-wall block, supplied by foot-wall erosion. We analyzed a PlioceneeQuaternary continental basin, currently crossed by the Tiber River in Italy. The tectono-sedimentary evolution of the basin developed at the hanging-wall of a regional low-angle extensional detachment, the Alto Tiberina Fault, in the axial region of the Northern Apennines of Italy. This area is affected by regional uplift on the order of 0.5e1.0 mm/yr. The present-day activity of the fault is revealed by both microseismicity and geodetic (GPS) data. We investigated the mid- (10e100 ka) and long-term (0.5e3.0 Ma) evolution of the three depocenters by studying the continental Pleistocene succession infilling the basin as well as fluvial terraces and higher paleosurfaces carved into the Pleistocene deposits. By using surficial geologic data and an interpretation of a set of seismic reflection profiles, we show that the three depocenters experienced a fairly similar evolution during the PlioceneeEarly Pleistocene, when a 1000-m-thick continental succession was deposited. On the contrary, geomorphological observations indicate that, at the beginning of the Middle Pleistocene, a switch occurred in the evolution of the three depocenters. In the northernmost Sansepolcro sub-basin, bounding normal faults are active and hanging-wall subsidence outpaces regional uplift. Concurrently, in the Umbertide and Ponte Pattoli subbasins uplift dominates over the hanging-wall subsidence, promoting river incision and exhumation of the Pleistocene deposits. For these two depocenters, by means of terrace-river correlations, we estimate that the incision rate is ~0.3e0.35 mm/yr, suggesting a maximum tectonic subsidence of 0.2 mm/yr. The identification of a heterogeneous uplift pattern along the hanging-wall of the Alto Tiberina Fault, driven by different displacement rates of its fault splays, allowed us to characterize fault segments with different activities and, possibly, different seismic behaviors.332 19 - PublicationRestrictedRadon and thoron emission from lithophysae-rich tuff under increasing deformation: An experimental study(2010-03-12)
; ; ; ; ; ;Tuccimei, P.; Università Roma Tre ;Mollo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Vinciguerra, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Castelluccio, M.; Università Roma Tre ;Soligo, M.; Università Roma Tre; ; ; ; Radon and thoron emissions from lithophysae‐rich tuff under increasing deformation are measured to determine how mechanical damage affects gas emission levels in tuffs. Mechanical properties of rocks under stresses should be carefully considered to properly interpret data from geochemical field monitoring. Two samples are uniaxially loaded up to failure, while two others are unloaded at the end of the elastic phase, in order to achieve the highest compaction of existing pores. Changes in the porosity of deformed samples are evidenced by helium pycnometer and microscopy analyses. Radon and thoron exhalation rates are measured on groups of two samples by alpha spectrometer technique. Results show that tuff samples are characterised by a dual porosity consisting of a macroporosity, given by isolated large pores with sizes from mm‐ up to cm‐scale and a microporosity ranging between microns to hundreds of microns. At the end of the elastic phase pervasive pore collapse is observed, due to the closure of the cm‐scale macropores. This is mirrored by a significant decrease of radon and thoron release. After failure, a further reduction of porosity in the rock adjacent to the fault planes is observed due to extensive closure of both macropores and micropores. At this stage radon and thoron emissions increase. The formation of new exhaling surfaces is the main carrier of the bulk increase of radon and thoron exhalations, strongly prevailing over the densification carried out from the compaction mechanisms. In terms of volcanic hazard, negative anomalies in radon emissions should be considered as indicators of forthcoming ruptures. Key words: radon and thoron exhalation, tuff deformation, seismic precursor.180 23 - PublicationRestrictedThe role of cooling rate in the origin of high temperature phases at the chilled margin of magmatic intrusions(2012)
; ; ; ; ;Mollo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Misiti, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Scarlato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Soligo, M.; Università Roma Tre; ; ; Both large (i.e. from hundreds to thousands of metres thick) and small (i.e. from centimetres to a few metres thick) magmatic intrusions are characterized by mineral compositional variations proceeding from the outermost to the innermost part of the intrusive body. However, in the case of large intrusions, mineral compositions become progressively more primitive (e.g. An-rich plagioclases and En-rich pyroxenes) from the chilled margin towards the interior; whereas, the opposite occurs for small intrusive bodies. Since it is unclear to what extent variable cooling rate conditions may alter the phase compositions, we have performed isothermal and dynamic experiments within a temperature interval of 1250–1100 °C using four different cooling rates of 150, 50, 10 and 2.5 °C/h. Numerical simulations of thermal regimes in and around small and large magmatic intrusions have also been performed and compared with phase compositional variations observed in our laboratory experiments. Results indicate that, over rapid cooling rate conditions, the crystal compositions faithfully reproduce those of high-temperature formations, i.e. An-rich plagioclases, En-rich pyroxenes and Usp-poor spinels. However, such a process is limited to a maximum distance of 2–3 m from the margin of the intrusion. Moreover, in active volcanic systems, heat fluxes are released from the main regions of magma storage into host rocks; therefore, only magmas solidifying at the contact of cold wall rocks may develop chilled margins with features related to rapid cooling rate conditions. In the presence of hot host rocks, thermal gradients are significantly reduced and the role played by cooling dynamics on textural and compositional variations of minerals is practically negligible.217 23