Lithospheric upper mantle xenoliths hosted in Neogene alkaline basalts from the Bakony-Balaton Highland and Little Hungarian Plain Volcanic Fields of the Carpathian-Pannonian region have been studied extensively petrologically, geochemically and isotopically (e.g., Embey-Isztin et al., 1989; Downes et al., 1992; Szabo et al., 1995). Based on these studies, remarkable incompatible trace element enrichment and variable eNd and eSr values of the deformed Type I. xenoliths have been recognized and interpreted by Downes et al. (1992) as being due to the host alkaline magmas and subduction-related calc-alkaline magmas or fluids. However, apparent evidence for mantle metasomatism such as presence of amphiboles and phlogopites, melt pockets, veins and fluid and/or silicate melt inclusions occurring in these xenoliths have been reported very rarely (Embey- Isztin, 1976;. Embey-Isztin et al., 1989; Szabo et al., 1995).
Here we present the results of detailed petrographic and major element analyses of melt pockets and veins found in six selected upper mantle samples (four peridotites and two pyroxenites) collected at the best known xenolith locations (Szentbekkalla and Gerce) of the studied volcanic fields. The goal of this work is to characterize the mantle melts and/or fluids formed and migrated in the mantle.
According to the petrography, the melt pockets (up to 4.5 mm in diameter) occur as partially crystallized multicomponent aggregates replacing partially or totally melted Cr-diopsidic clinopyroxenes or rarely pargasitic amphiboles. The melt pockets are composed of silicate glass, newly formed clinopyroxene, olivine, spinel, carbonates, ± vesicles ± sulfide blebs. The melt veins (up to 1.5 mm in thickness) occur frequently as parallel cracks crosscutting the whole xenolith. They consist mostly of silicate glass and carbonates. Newly formed clinopyroxenes, olivines and spinels are very rare.
Based on electron microprobe analyses, the composition of carbonates is calcite and Mg-calcite with small amounts of FeO (up to 0.54 wt%) and MnO (up to 1.5 wt%). Compositions of silicate glasses show relatively wide silica range (50 to 59 wt%), high alumina (18 to 25 wt%) and high total alkalis (5.5 to 7.8 wt%), relatively low MgO (1.8 to 4.5 wt%) and FeO (2.4 to 6.8 wt%) content.
To estimate the bulk compositions of the melt pockets and veins, we have performed mass balance calculation, based on the modes and chemistry of the melt pockets and veins. The bulk compositions of the melt pockets are basaltic and trachybasaltic somehow resembling the composition of the host basalt reported by Embey-Isztin et al. (1993) and Harangi et al. (1995). The bulk compositions of the veins fall in fields of andesite and basaltic trachyandesite close to the large area of “andesitic” silicate melt inclusions occurring in Nograd-Gomor xenoliths studied by Szabo et al. (1996).
A severe boron pollution has been recognized in the shallow aquifer of Isola di Castelluccio (central-eastern Tuscany, Italy) since 2009. Previous investigations showed that the high boron concentrations (up to 57 mg L-1) were related to an anthropogenic source. It was likely due to current and/or past industrial and artisanal activities, which were using B-compounds during their productive cycles. However, a univocal source of boron has so far not been recognized. In this work, we present and discuss new geochemical and isotopic data related to an extensive campaign (June 2016) carried out in 33 domestic well and piezometer waters. In addition, the results from a three-weekly to monthly monitoring survey (from August 2014 to December 2019) on selected waters were used to recognize signals in response to dry and wet periods or related to the presence of the recently installed hydraulic barrier. To verify the efficiency of the hydraulic barrier a numerical model of the shallow aquifer was performed by using the MODFLOW computer program. This study has allowed to identify where the source of contamination is likely located. This implies that specific investigations can now be carried out to definitively remove the anthropogenic source of boron.
<p>The Adriatic region is highly vulnerable to the adverse impacts of climate change. Although attention has been paid to understand the climate change impact and risks over the last decades, the Adriatic community still faces a lack of a common risk assessment. For this reason, ASTERIS project has been financed at the Call for proposal 2017 Priority Axis Safety and resilience of Interregional V Italy-Croatia 2014-2020 Program. To this overall objective, the project will provide two main outputs: i) a map of vulnerability to coastal salinization at the macro-regional scale (Adriatic) based on future scenarios for sea-level rise and the hydrological cycle and ii) best practice and guidelines for the management of vulnerable sites defined though the analysis of representative case studies in Italy and Croatia. Within these general purposes, hydrogeological and geochemical surveys in two specific shallow aquifer systems that develop in the coastal areas of Fano and Ravenna (central-eastern Italy), were carried out. Several periodical campaigns, aimed at measuring water level and physical-chemical parameters by vertical logs in wells or piezometers, were also conducted. Additionally, ground and surface water samples were also collected for chemical and isotopic analyses to define the compositional features and the main geochemical processes affecting the two shallow aquifers. Preliminary investigations suggested that the Ravenna shallow aquifer is already strongly spoiled by a significant seawater intrusion (up to 80 %), whereas at Fano the presence of the saline wedge can be regarded as negligible. This indicates that the aquifer system of Fano can be considered as a good proxy for evaluating and simulating potential processes of saline-fresh water interactions by either the increasing demand of water exploitation and sea level rise due to anthropogenic pressure and climate change, respectively. In order to simulate possible future ingressions of seawater in the aquifer system of Fano, groundwater flow and transport models are currently in progress. These models will be implemented and calibrated according to the hydrogeological and geochemical data collected within the framework of the ASTERIS project. The expected modelled scenarios, obtained through predictive simulations, are of pivotal importance for assessing the possible groundwater response to climate change and for a correct management and protection of water resources, which can be exported to other aquifers system along the Adriatic Sea.</p>
