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The study of magmatic/volcanic volatiles is based on the determination of H2O and CO2 in glasses, assuming they represent the main volatiles reservoirs of volcanic rocks . However, recent works show that some volcanic nominally anhydrous minerals (NAMs) do contain water ( CO2). Leucite (KAlSi2O6) is an anhydrous mineral typical of potassium-rich basic lavas [1]. Recently [2] and [3] studied, using FTIR spectroscopy, a large number of leucites from all volcanic areas of the Roman Comagmatic Region and showed that they typically contain significant amounts, up to several thousand ppm, of structurally bound water. We report here preliminary results of an experimental study aimed at defining pressure and temperature conditions controlling the solubility of H2O into the leucite framework. Experiments were performed in a non end-loaded piston cylinder apparatus, with T in the range 400-800°C and P in the range 200-500 MPa. Leucite fragments were used as starting materials. The fragments were pre-heated at 600 °C and atmospheric pressure in order to abtain completely dehydrated starting material [4]. The anhydrous grains were then introduced in platinum tubes with excess distilled water and run. Single-crystal micro FTIR was used as a technique to analyse the experimental products. Preliminary data show that significant water amounts (650-950 ppm) diffuse into leucite at these conditions. FTIR images show that the crystals run under these conditions for 4 hours are homogeneously hydrated, suggesting a fast H2O diffusion through the feldspathoid matrix, as also suggested by the dehydration experiments done by [4] at 1 atm. References [1] Deer, Howie and Zussman (2004) Rock-forming minerals, 4B. The Geological Society, London. [2] Balassone, Beran, Fameli, Amalfitano, and Petti (2006) Neues Jahrbuch für Mineralogie Abhandlungen, 182, 149-156. [3] Della Ventura, Bellatreccia and Piccinini (2008) Am. Mineral., 93, 1538-1544. [4] Della Ventura, Bellatreccia, and Piccinini (2007) Frontiers in Mineral Sciences, 27-28 June, Cambridge (GB).

Radon gas is the subject of a great deal of research because its concentration builds up into indoor air and the long-term radon exposure is considered the second cause of lung cancer, after smoking. In addition to that, the release of radon from soil is under investigation in active volcanic and seismic areas because radon anomalies are believed to occur before earthquakes and volcanic eruptions. Several papers report results of laboratory experiments on the effects of activity concentration of 222Rn and 220Rn precursors, humidity content and grain size of geological materials over the radon emission. However no correspondent studies have targeted the effect of the temperature on radon release. The present contribution focuses on the influence of temperature, varying from 20° to 60° C, on 222Rn and 220Rn emission from two volcanic rocks, a tuff and a lava flow. The experimental apparatus consists of a small accumulation chamber coupled to solid-state alpha spectroscopy; it also allows to select and keep constant the experimental temperatures applied to the rock sample. The effect of ambient temperature on detection efficiency is also investigated. Results show a significant enhancement of radon emissions from rocks with increasing temperature. The results of these experiments suggest that thermal enhancement of radon emission can be used to investigate more precisely the correlation between physical mechanisms determining damage in stressed rocks and radon release, taking advantage of the improved radon emission. Experimental test with a better resolution are the key to interpret radon anomalies preceding earthquakes or volcanic eruption.

""Positive radon anomalies are commonly used as a tool to predict dynamic failure in the crust, as stated by the widely-used dilatancy model for earthquake prediction. The model foresees that the formation and propagation of cracks prior to rupture will serve to create new surface area and hence increase radon emanation. However, this simplified picture is not only occasionally contradicted by negative radon anomalies, but sometimes negative anomalies are measured at the seismic source, whilst contemporaneous positive anomalies are recorded at monitoring stations located hundreds of kilometres away. Mysteriously, alternating increases and decreases or no significant variations have also been recorded. Hence, despite early promise, radon emanation does not appear to be a very compelling warning signal and many questions remain unresolved. Although numerous studies have investigated field radon emanation from rocks under natural stress conditions, only few have attempted to experimentally relate rock deformation with radon change. . Here we present, for the first time to our knowledge, an original experimental set-up consisting of a new accumulation chamber made of a drypack material, a polyester-aluminum-polyethylene bag, containing the rock specimen and connected in a closed-loop configuration to the RAD 7. The drypack-chamber is loaded under a uniaxial press, without being damaged during rock deformation. Radon gas concentration emitted from the samples is simultaneously and continuously monitored by the system; therefore, the originality of the experiments consists in a real time monitoring of radon emission changes during the whole process of rock deformation. Additionally, the drypack-chamber is surrounded by a heating belt that allows us to investigate the effect of high temperature conditions (up to 90 °C) on radon emission. It needs to be stressed that the radonometer is alpha-spectrometry based and is able to measure simultaneously 222Rn (radon) and 220Rn (thoron) activity concentrations. The great advantage of determining thoron is the possibility of recording any activity change in the closed system within the length of a single run cycle (30 minutes), due to the short half-life of 220Rn (55.6 seconds) that reaches any new equilibrium conditions in about 5 minutes.. Results demonstrate that radon exhalation from the rock specimen drastically increases with increasing the experimental temperature. This finding allows us to discriminate low variations in radon emissions when rock samples are uniaxially loaded under the press. Uniaxial compressive tests performed on highly porous (47 %) volcanic tuff from Vico Volcanic District (central Italy) shows that the radon emission decreases with increasing load. Such a variation is proportional to a reduction of porosity associated with the compaction of the tuff sample. When the specimen fails, a drastic increase of emission is verified.. Moreover, long-term experiments (in the order of weeks) performed by maintaining a constant load on the tuff specimen show that the deformation increases with time. The radon signal coherently continues to decrease up to the complete closure of pores. At that point, a further increase of load does not induce any additional compaction and any radon emission change, with a constant exhalation up to the failure. This has strong implications in the field of radon anomalies prior to earthquakes, showing that the seismic event can be preceded by no significant radon anomalies, as already documented in literature. . Our experimental investigation sheds light on several apparently contradictory signals recorded by radon monitoring stations near active faults and volcanoes. Results demonstrate that emanation rate is governed by the prevalent deformation mechanism. In terms of seismic and volcanic hazard, the deformation mechanism of rocks under stresses should be carefully considered to properly interpret data from geochemical field monitoring. . . ""

""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""

""Anomalous radon and thoron emissions are regarded as valuable precursors of earthquakes and volcanic eruptions and are related to increasing damage of the medium. However both positive and negative anomalies are observed in the field prior ruptures, thus indicating competing deformation mechanisms. Initial porosity (P) plays a key role for natural lithologies in controlling damage accumulation and strain localisation processes. Thus investigating how elastic properties of low to high porosity rocks are affected from increasing loading is required to quantitatively interpret the positive and negative anomalies observed. . Here we present an experimental dataset where measurements of radon (222Rn) and thoron (220Rn) emissions are carried out on low to high porosity lithologies incrementally loaded up to failure. The following samples are investigated: a high porosity lithophysae-rich tuff (P = 47.0 %) and a low porosity phonolitic lava flow (P = 3.6%). Cylindrical samples of 120 (length) x 60 (diameter) mm, have been uniaxially loaded at constant strain rate in servo-controlled uniaxial machines. Samples have been either 1) mechanically damaged to the end of the elastic phase, before the onset of dilatancy or 2) loaded up to the failure. Radon and thoron exhalation rates are carried out by using a solid-state alpha detector, connected to a small accumulation chamber kept at the constant temperature of 60°C. Measurements are performed on two samples at once to achieve stronger signals and repeated several times in order to verify their reproducibility.. Results show that a decrease of radon and thoron emissions are evidenced at the end of the ‘damage phase’ for the high porosity tuff, while a slight increase is observed for the low porosity lava flow. At the end of the elastic phase the tuff reduces its radon and thoron exhalation rates, because of pervasive pore collapse of the macropores, with a P reduction up to 40.1 %. In contrast, for the lava flows the loading slightly increases the crack damage and, consequently, P increases up to 5.1 %. This change does not significantly affect the radon exhalation. At the failure, new rupture surfaces are generated. The total exhaling surface of the samples increases and an increase of radon emission is observed for both lithologies. ""

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.