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Barca, Donatella
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- PublicationRestrictedCrystal residence times from trace element zoning in plagioclase reveal changes in magma transfer dynamics at Mt. Etna during the last 400 yearsTrace element zoning in plagioclase of selected alkaline lavas from the historic (pre- 1971 AD) and recent (post-1971 AD) activity of Mt. Etna volcano has been used to highlight the possible role that volcano-tectonics exert on magma transfer dynamics. The observed textural characteristics of crystals include near-equilibrium textures (i.e.,oscillatory zoning) and textures with variable extent of disequilibrium (patchy zoning, coarse sieve textures and dissolved cores). One of the main differences between crystals of the historic and recent activity is the higher average 28 anorthite content for the post-1971 AD plagioclases, which agrees with the more basic character of the hosting lava. Among the most noticeable variations, recent plagioclases also exhibit higher K, Rb, LREEs and lower Ba abundances than the historic ones, with the largest differences more evident at high anorthite (An) contents. Variations in anorthite content along core-to-rim profiles obtained on crystals with different types of textures for both the historic and recent eruptive periods were evaluated particularly versus Sr/Ba. At comparable average An contents, crystals characterized by oscillatory zoning, which are representative of near-equilibrium crystallization from the magma, display distinct Sr/Ba ratios (~6 in historic and ~17 in recent lavas). We suggest these features are primarily related to recharge of a new, geochemically-distinct magma into the storage and transport system of the volcano since 1971 AD. In addition to distinct trace element and textural characteristics of plagioclase, Sr diffusion calculations for plagioclase suggest that magma residence times are generally shorter for magmas erupted in recent times (i.e., post-1971 AD) compared to those erupted during the historic period. These estimations match well with the enhanced extension rate within the upper 10 km of the crust observed during the last decades, and are also in accordance with the increased eruptive frequency after the 1971 AD eruption.
561 2 - PublicationRestrictedA multidisciplinary geochemical approach to geothermal resource exploration: The Spezzano Albanese thermal system, southern Italy(2023-07-07)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ; ; ; This work aims to define the geothermal conceptual model of the Spezzano Albanese thermal system located in the northern sector of the Calabria Region, along the western edge of the Sibari Plain. The study confirms that the deep thermal reservoir of Spezzano Albanese is mainly hosted within the permeable levels of the evaporite deposits of the Messinian succession including siltstones with manganese mineralisation, halite, and gypsumarenites. The thermal waters show discharging temperature between 20.2 and 26.6 ◦C and a high compositional variability, from Na–Cl to Na–Ca–HCO3. The compositional evolution (from Na–Cl to Na–HCO3) is accompanied by a decrease in both salinity and the concentrations of most dissolved constituents, including Cl, Br, B, Li, Na, K, Mg, Ca, and Ba. These variations are due to mixing between the thermal endmember, rich in Cl and related components, and low-salinity, cold shallow waters (temperature between 17.5 and 22.7 ◦C). The study points out that the thermal endmember derives by halite dissolution and more complex water-rock interaction processes involving (1) the dissolution of other solid phases of the Messinian deposits, as also confirmed by δ34S values of dissolved sulphate and sulphide, and (2) the precipitation of secondary solid phases (e.g., barite). The geothermometric modelling suggests that the thermal groundwaters in the deep reservoir are probably in equilibrium with either (i) quartz, calcite, disordered dolomite, low-albite, and K-feldspar, as well as with pyrophyllite and poorly crystalline kaolinite (as proxies of clay minerals) at temperatures of 65.5 ± 4.5 ◦C or (ii) quartz, calcite, disordered dolomite, low-albite, disordered adularia, laumontite and saponites at temperatures of 56.1 ± 4.3 ◦C, based on the first and second geothermometric model, respectively. The δ18O and δ2H values of water confirm a meteoric origin for the thermal waters with average recharge altitudes between 745 and 857 m a.s.l. These elevations are compatible with the recharge from the western side of the Esaro valley where evaporite successions are found close to the surface. The isotopic value of the dissolved CO2 associated to the Spezzano Terme water highlights its likely microbial origin, as recognised for other thermal circuits hosted in sedimentary rocks of the southern Apennines. Furthermore, the thermal endmember shows a noteworthy enrichment in CH4 with respect to air due to the interaction of groundwater with sediments rich in organic matter. Although methane could have a biogenic origin, the presence of a minor component of thermogenic methane in the gas phase dissolved in the Spezzano Terme waters cannot be completely excluded. The data obtained in this study allow to assume that the recharge meteoric waters descend to a maximum depth of about 1.1–1.4 km below the main emergence area and then the regional NE-SW fault systems probably act as a preferential pathway for the ascent of the thermal waters towards the surface. These waters discharge at Spezzano Albanese, where the crystalline-metamorphic units cropping out immediately upstream of the emergence area act as cap-rock favouring the final ascent towards the surface of the thermal waters.156 18 - PublicationOpen AccessEvidencing Human Occupation of a Small Island Through Ancient Glass: The Case of Ustica (Palermo, Italy)(2020)
; ; ; ; ; The subject of this study consists of 17 ancient glass fragments from the island of Ustica (Palermo, Italy) obtained from local museums. All the 17 glass fragments are stratigraphically decontextualized, as they were collected by archaeological surface surveys. Each fragment was analyzed by Electron Micro Probe Analyzer coupled with an Energy Dispersive X-Ray System (EMPA-EDS) and by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) to obtain the composition of major, minor and trace elements. Surface analyses revealed the presence of corrosion layers in most of the glass fragments which was evident also in the chemical data. Nevertheless, reconstruction of the glassmaking processes and the approximate period of production was possible for almost all the glass fragments. Less than half of the examined fragments are attributable to recognizable typologies as unguentaria, beakers, bottles, and vases; all the other small fragments are typologically undetermined. Out of 17 fragments only one fragment is of HLLA composition possibly being produced in 17th–18th century AD, while all the others can be attributed to soda glass with different periods of production: natron glass from Roman and Early Medieval period, plantash glass from High or Late Medieval period with the exception of possible Byzantine glass from 6th century AD, and synthetic soda glasses typical of modern era. These data confirm the discontinuous habitation of the island from the Roman period as well as the import of glass objects to the island.57 13 - PublicationEmbargoHydrogeochemical and isotopic characterization of the Gioia Tauro coastal Plain (Calabria - southern Italy): A multidisciplinary approach for a focused management of vulnerable strategic systems(2023)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ;This work pursues the hydro-geochemical and isotopic characterization of the complex groundwater system of the Gioia Tauro Plain, one of the most important industrialized and agricultural coastal areas of southern Italy. The anthropic pressure exposes the water resources at risk of depletion and quality degradation making the plain groundwater a system of high scientific and social interest. The plain is characterized by a shallow aquifer, mostly recharged by local rains and a deep aquifer apparently less influenced by local precipitation. Both aquifers are mainly Ca-HCO3 waters except for localized sectors where Na-HCO3, Na-Cl and Ca-SO4 waters are present. In deep aquifer, both prolonged interaction with sedimentary rocks, mainly deriving from the erosion of crystalline rocks, and direct cation exchange represent the primary factors controlling the formation of Na-HCO3 waters. Mixing processes between these waters and either connate brine and/or deep thermal waters contribute to the formation of isolated high salinity Na-Cl-rich waters. In shallow aquifer, inputs of N-rich sewage and agriculture-related contaminants, and SOx emissions in proximity of the harbor are responsible of the increasing nitrate and sulphate concentrations, respectively. The Cl/Br and NO3/Cl ratios highlight contamination mainly linked to agricultural activities and contribution of wastewater. Along the northern boundary, the warmest groundwater (Na-Cl[SO4]) were found close to a bend of the main strike-slip fault system, locally favouring the rising of B- and Li-rich deep waters, testifying the influence of geological-structural features on deep water circulation. Despite the high-water demand, a direct marine intrusion is localized in a very restricted area, where we observed an incipient groundwater-seawater mixing (seawater contribution ≤7 %). The qualitative and quantitative conditions of the shallow aquifer still have acceptable levels because of the relatively high recharge inflow. A reliable hydrogeochemical conceptual model, able to explain the compositional variability of the studied waters, is proposed.151 3