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The Choiyoi Group from the Permo-Triassic, is one of the most conspicuous volcano-sedimentary suites of southern South America, considered critical to understand the geological evolution of the western margins of Gondwana. In this regard, petrography, geochemistry, and structural data were examined to better elucidate the physical character and emplacement conditions of the unit in the Cordón del Plata range, within the Frontal Cordillera of Mendoza, Argentina. The site is representative of the magmatism and deformation through different Andean cycles. Results of the study indicate three facies of increasing felsic composition upwards. Mafic units consist of basalts, andesite and andesitic breccias at the base of the sequence. Felsic rocks such as rhyodacites, granites and welded tuffs are predominant above. The fault zone of La Polcura - La Manga is the most prominent structural feature in the region, which presumably controlled the emplacement of breccias and ignimbrites within the middle and upper members. These compositional variations suggest a magma evolution from subduction to a rifting environment after the San Rafael orogeny in the Late Palaeozoic. In this line, the Lower Choiyoi was observed to overlie the San Rafael structures indicating thus, that compression ceased before the volcanic extrusion. Geochemistry data indicate that mafic rocks are mostly high-potassium, calc-alkaline volcanics derived from the mantle wedge above the subduction zone. In contrast, the Upper Choiyoi corresponds to high-potassium rhyolites to shoshonites, typically depleted in Eu. This indicates partial melting of a lithospheric mantle in an average to thin crust. RESUMEN El Grupo Choiyoi del Permo-Triásico es una de las suites volcánicas y sedimentarias más conspicuas del sur de Sudamérica, considerada crítica para comprender la evolución geológica de los márgenes occidentales de Gondwana. En este sentido, se examinaron datos petrográficos, geoquímicos y estructurales para dilucidar mejor el carácter físico y las condiciones de emplazamiento de la unidad en el área del Cordón del Plata, dentro de la Cordillera Frontal de Mendoza, Argentina. El sitio es representativo del magmatismo y la deformación a través de diferentes ciclos andinos. Los resultados del estudio indican tres facies litológicas de aumento de la acidez hacia arriba. Las unidades máficas consisten en basaltos, brechas andesíticas y andesítas en la base de la secuencia. Predominan las rocas félsicas, como las riodacitas, los granitos y las tobas soldadas. La zona de falla de La Polcura - La Manga es la característica estructural más prominente de la región, que presumiblemente controla el emplazamiento de brechas e ignimbritas dentro de los miembros medios y superiores. Estas variaciones en la composición sugieren una evolución magmática de la subducción a un entorno de ruptura después de la orogenia de San Rafael en el Paleozoico tardío. En esta línea, se observó que el Choiyoi Inferior cubría las estructuras de San Rafael, lo que indica que la compresión cesó antes de la extrusión volcánica. Los datos de geoquímica indican que las rocas máficas son en su mayoría vulcanitas calcoalcalinos de alto potasio derivados de la cuña del manto por encima de la zona de subducción. En contraste, las rocas felsicas van desde las riolitas con alto contenido de potasio hasta las shoshonitas, típicamente pobres en Eu. Esto indica la fusión parcial de un manto litosférico en una corteza media a delgada.

A geochemical investigation was undertaken at Mt. Etna Volcano to better define groundwater characteristics of its aquifers. Results indicate that the Na?Mg ± Ca-HCO3− ± (SO42− or Cl−) type accounts for more than 80% of the groundwater composition in the volcano. The remaining 20% is characterized by elevated Ca2+. Waters along coastal areas are enriched in SO42− or Cl−, mainly due to mixing with seawater and anthropogenic effects. The majority of the samples showed values between −4% to −9% for δ18O and −19? to −53% for δ2H, suggesting that precipitation is the predominant source of recharge to the aquifers, especially in the west of the study area. The analysis of δ13C and pCO2 shows values 1 to 3 times higher than those expected for waters in equilibrium with the atmosphere, suggesting a partial gas contribution from deep sources. The diffusion of gasses is likely to be controlled by tectonic structures in the volcano. The ascent of deep brines is also reflected in the CO2 enrichment (up to 2.2 bars) and enriched δ2H/δ18O compositions observed in the salt mounts of Paternò. Fil: Bellia, Carmelo . National Institute of Advanced Industrial Science and Technology. Geological Survey of Japan; Japón Fil: Gallardo, Adrian Hugo. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Yasuhara, Masaya . National Institute of Advanced Industrial Science and Technology. Geological Survey of Japan; Japón Fil: Kazahaya, Kohei . National Institute of Advanced Industrial Science and Technology. Geological Survey of Japan; Japón

The Gnangara system is the main source of freshwater for Perth, Western Australia. However, aquifers in the region are under severe stress due to a drying climate, intensive pumping and changes in land use. The aim of this study is to apply the mean rainfall cumulative deviation and Mann-Kendall analyses at 77 monitoring bores to investigate the response of the water table to key recharge components. This information is critical for setting new allocation limits and reviewing current policies in the region. Results show that overall there is a good correspondence between water levels and rainfall fluctuations. Areas of groundwater recharge are highly sensitive to climate change and have been severely affected by reduction in rainfall rates in recent years. Further, removal of pine plantations correlated well with a rise in groundwater levels although the effect seems to be temporary. The impact of pumping is mainly observed in vicinities of public-supply borefields. Elsewhere, water table trends show a relative stabilisation indicating that storage still exceeds the influence of rainfall reduction in areas dominated by through flow or groundwater discharge. The study contributes to update the status of the Gnangara groundwater resource, and provides new insights for the sustainable management of one of the main aquifer systems in Australia.

Groundwater overdraft resulted in land subsidence throughout the Nobi Plain, central Japan. To cope with the growing water demand in the region, a numerical model was used to determine the maximum withdrawal capacity of two confined aquifers without causing undesirable consequences. Results were validated against field data and by analytical solutions. The analysis focused in Aburashima, a site expected to experience a rapid development in the forthcoming years. Calculations showed the water availability in the upper aquifer is limited. Moreover, seasonal fluctuations in heads reduce its extraction capacity up to 44%. In contrast, storage is substantially higher in the deep aquifer. Larger quantities and lower extraction costs make this layer a more reliable source for water supply. Findings from this study will be used by authorities to update the current legislation on groundwater abstraction. Nevertheless, it is argued that to achieve a long-term sustainability, policies should not limit solely to control regulations but also to economical strategies and the expansion of the infrastructure system.

Tsukuba city is located in the center of the Kanto Plain, the largest basin in Japan. Its dramatic increase in population and agricultural production make it imperative to quantify the groundwater system to ensure the long-term sustainability of the resource. In response to this need, the hydrogeology and chemistry of groundwater in a typical agricultural catchment of the region were characterized on a detailed scale in order to serve as a scientific tool for the local management authorities. The uplands include two aquifers separated by confining clays. In the lowlands, these aquifers behave as a single unit. Infiltration from precipitation recharges the groundwater, which moves laterally through the sands and discharges mainly into an artificial drainage. The age of groundwater increases with distance from the drain, with a maximum of 63 years for particles that originated at the catchment divide. The chemistry of shallow groundwater reflects a fertilizer's source, with approximately 75% of the samples collected within the croplands exceeding the Japan's drinking water standards for NO 3 − . Biochemical processes and the absence of agricultural practices reduce the salts concentrations throughout the rest of the area. Better water quality was found at depth, where groundwater of Ca–HCO 3 type prevails.

Driven by the hydraulic gradient, terrestrial groundwater can be discharged directly into the coastal ocean where heads are above sea level, a phenomenon known as submarine groundwater discharge (SGD). Although long overlooked, in recent years SGD has received increasing attention due largely to its potential importance in the transport of chemical constituents to the sea. Indeed, SGD occurrence and control mechanisms are still poorly understood. Submarine discharge often represents only a minor component of regional total water budgets, but because estimated fluxes are highly variable and quantification remains challenging, the process deserves to be carefully evaluated when investigating marine ecosystems and/or the safety of geological repositories in coastal areas, notably for the underground storage of CO2. In view of the focus the topic is gaining, reflected in the large amount of information continuously being published in this field, here we present a selected review of our current knowledge of key mechanisms determining submarine groundwater discharge, and an updated compilation of most recent advances in research both in Japan and other regions of the world. In addition, we identify some potential pitfalls that need to be borne in mind in future work on SGD. Particularly in view of globally increasing urbanization and climate change, this contribution should prove useful also to local governmental authorities and scientists involved in groundwater coastal ecosystem management.

Groundwater is one of the most valuable resources for drinking water and irrigation in the Maheshwaram Catchment, Central India, where most of the local population depends on it for agricultural activities. An increasing demand for irrigation and the growing concern about potential water contamination makes imperative the implementation of a systematic groundwater-quality monitoring program in the region. Nonetheless, limited funding and resources emphasize the need to achieve a representative but cost-effective sampling strategy. In this context, field observations were combined with a geostatistical analysis to define an optimized monitoring network able to provide sufficient and non-redundant information on key hydrochemical parameters. A factor analysis was used to evaluate the interrelationship among variables, and permitted to reduce the original dataset into a new configuration of monitoring points still able to capture the spatial variability in the groundwater quality of the basin. The approach is useful to maximize data collection and contributes to better manage the allocation of resources under budget constrains.