Groundwater-driven temperature changes at thermal springs in response to recent glaciation: Bormio hydrothermal system,Central Italian Alps     

Giorgio Volpi  Fabien Magri  Paolo Frattini  Giovanni B. Crosta  Federico Riva 《Hydrogeology Journal》2017,25(7):1967-1984

Thermal springs are widespread in the European Alps, with hundreds of geothermal sites known and exploited. The thermal circulation and fluid outflows were examined in the area around Bormio (Central Italian Alps), where ten geothermal springs discharge from dolomite bodies located close to the regional Zebrù thrust. Water is heated in deep circulation systems and upwells vigorously at a temperature of about 40 °C. Heat and fluid transport is explored by steady and transient three-dimensional finite-element simulations taking into account the effect of the last glaciation, which in the study area was recognized to end around 11,000–12,000 years ago. The full regional model (ca. 700 km²) is discretized with a highly refined triangular finite-element planar grid. Numerical simulations suggest a reactivation of the system following the end of the Last Glacial Maximum. Results correctly simulate the observed discharge rate of ca. 2,400 L/min and the spring temperatures after ca. 13,000 years from deglaciation, and show a complete cooling of the aquifer within a period of approximately 50,000 years. Groundwater flow and temperature patterns suggest that thermal water flows through a deep system crossing both sedimentary and metamorphic lithotypes along a fracture network associated with the thrust system. This example gives insights into the influences of deep alpine structures and glaciations on groundwater circulation that control the development of many hydrothermal systems not necessarily associated with convective heat flow.  相似文献   

A quantitative approach to the influence of pyrite separation on Cu-processing tailings: a case study at Reps,Mirdita district,Albania     

Irene Fantone  Giovanni Grieco  Agim Sinojmeri  Alessandro Cavallo 《Environmental Earth Sciences》2017,76(22):774

Sulfide-rich tailings are a well-known environmental threat due to their production of acid drainage (AD) and release of potential toxic elements (PTE) to the local environment. The presence of heterogeneous materials produces complex environmental signatures and complicates the quantitative prediction of contamination. The present work provides a method of quantifying such heterogeneities, starting from mineral processing data of the Reps, Mirdita (Albania) site. A quantitative flow sheet (QF) method was applied to a selected dump site of the Mirdita copper mining district where secondary pyrite separation had been used in the past. The site is subject to long-lasting (10³ years) AD processes with significant release of PTE into the local environment. The tailings at the Reps site are divided into two classes based on the sulfide S content, respectively, represented by high-sulfide-content (S > 10 wt%) materials (hS) and low-sulfide-content (S < 3 wt%) material (lS). The reconstruction of the QF allowed us to identify the hS tailings as the discharge of single-flotation processing lines. This material accounts for about 82% of the total potential H₂SO₄ production, even though it represents < 20% of the entire tailing discard. The QF is a useful tool for the evaluation of heterogeneity and consequently for the modeling of waste management within abandoned sites and in working plants. Given a good quantification, heterogeneity can in fact support the setting of pyrite separation lines or the separate management of pyrite-rich tailing dumps.  相似文献   

Ensuring very shallow-water sediment properties: case study from Capo Granitola harbour,Sicily (Italy)     

Michele Punzo  Giuseppe Cavuoto  Daniela Tarallo  Vincenzo Di Fiore 《Marine Geophysical Researches》2017,38(3):313-323

We present high-resolution Vp models of the Capo Granitola harbor, Sicily (Italy) obtained by first arrival traveltime tomography. Seismic data were collected along four hydrophone arrays on the sea-bottom and via a Watergun as seismic source, in order to plan dredging operations in the harbor. Using a hydrophone spacing of 2.5 m and shot spacing of 5 m, very high resolution quality data were recorded. Seismic tomography expands existing knowledge of the harbour subsoil with a penetration of about 20 m, illuminating the Lower Pleistocene bedrock (Marsala calcarenites) that corresponds to high-Vp regions (Vp?>?4.5 km/s). Low Vp (1.8–4.5 km/s) deposits belonging to terraced calcarenites (Upper Pleistocene in age) are also well imaged; they are about 8 m thick and lie below loose sand deposits (Vp?=?1.5 km/s). The substratum has an articulated morphology; Vp images unravel small steps in the basement probably related to structural discontinuities (e.g., faults). Processing data with 3D techniques enables images of the structure and the thickness of the lithotypes to be reconstructed, thus leading to large-scale, realistic estimates of the total quantity of material to be excavated or dredged. Tomographic profiles permit clear discrimination of the soft sediment above the basement and thus allow the determination of the total volume of sediment above the seismic bedrock, estimated at about 265,000 m³.  相似文献   

An unexceptional scale     

Michele Ford 《Singapore journal of tropical geography》2008,29(2):130-132

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High‐pressure mineral assemblage in granitic rocks from continental units,Alpine Corsica,France     

Alessandro Malasoma  Michele Marroni  Giovanni Musumeci  Luca Pandolfi 《Geological Journal》2006,41(1):49-59

The Popolasca–Francardo area of northern Corsica contains an assemblage of continental tectonic units affected by an Alpine deformation. In one of these units, Unit II, previously regarded as weakly metamorphosed, a metamorphic mineral assemblage characterized by sodic amphibole, phengite, quartz, albite and epidote has been found in an aplite dyke that cuts the dominant granitoids. Peak‐metamorphic temperature and pressure conditions of 300–370°C and 0.50–0.80 GPa, respectively, have been determined. This finding indicates that a continuous belt of continental slices, characterized by high‐pressure, low‐temperature metamorphism of Tertiary age, extends from the Tenda Massif in the north to the Corte area in the south, thus placing additional constraints on the tectonic evolution of Alpine Corsica. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Persistent polybaric rests of calc-alkaline magmas at Stromboli volcano,Italy: pressure data from fluid inclusions in restitic quartzite nodules     

Gloria?Vaggelli  Lorella?FrancalanciEmail author  Giovanni?Ruggieri  Silvia?Testi 《Bulletin of Volcanology》2003,65(6):385-404

A fluid-inclusion study has been performed on quartzite nodules of stromboli volcano hosted by calc-alkaline lavas of both the Strombolicchio (200 ka) and Paleostromboli II (60 ka) periods. The nodules are mainly composed of quartz crystals with subordinate plagioclase and K-feldspar. Small interstitial minerals such as plagioclase, K-feldspar, clinopyroxene, biotite, and quartz are also found, together with glass. Muscovite, epidote and zircon occur as accessory minerals. Different quartzite nodules occur: (1) equigranular polygonal granoblastic quartzite nodules forming a polygonal texture with clear triple points; (2) inequigranular polygonal granoblastic quartzite nodules; and (3) break-up nodules with strongly resorbed quartz. These quartzites are restites from partial melting, involving felsic crustal rocks at the magma/wall rock contact. Restitic quartz re-crystallises at variable and generally high temperatures, leading to the formation of quartzites with different textures. Quartz grains contain five types of fluid inclusions distinguished on the basis of both fluid type and textural/phase relationships at room temperature. Type I are two-phase (liquid+vapour) CO ₂-rich fluid inclusions. They are primary and subordinately pseudosecondary in origin and have undergone re-equilibration processes. Type II mono-phase/two-phase (vapour/liquid+vapour) CO ₂-rich fluid inclusions are the most common and, based on their spatial distribution and shape, they can be divided into two subclasses: type IIa and type IIb. Type II inclusions are secondary or pseudosecondary and they are assumed to have formed after decrepitation of type I inclusions and cracking of the host quartz. Type III inclusions are mono-phase (vapour); they possibly contain CO ₂ at very low density and surround the inner rims of quartz grains. Type IV two-phase silicate-melt inclusions contain glass±CO ₂-rich fluid. Some of them are cogenetic with type II inclusions. Finally, type V two-phase (liquid+vapour) aqueous inclusions are both vapour-rich and liquid-rich aqueous inclusions. Microthermometric experiments were performed on both type I and II inclusions. Type I inclusions homogenise to liquid between 20 and 30.5 °C. Type IIa inclusions homogenise to vapour in the 24 to 30 °C range, with a maximum peak of frequency at 29 °C. Type IIb inclusions also homogenise to vapour between 14 and 25 °C. There appears to be no difference in homogenisation temperature distribution between the Strombolicchio and Paleostromboli II samples. The trapping pressures of the fluid inclusions have been obtained by combining the microthermometric data of the Strombolicchio and Paleostromboli II samples with the pressure–temperature–volume (i.e. density) characteristics for a pure CO ₂ system. The data on the early inclusions (type I) suggest an important magma rest at a pressure of about 290 MPa (i.e. about 11-km depth). Type IIa CO ₂ inclusions suggest that a second magma rest occurred at a pressure of about 100 MPa (i.e. about 3.5-km depth), whereas type IIb inclusions were trapped later at a shallower depth during the final magma upwelling. No pressure/depth differences seem to occur between the Strombolicchio and Paleostromboli II periods, indicating the same polybaric rests for the calc-alkaline magmas of Stromboli, despite their significantly different ages. This persistence in magma stagnation conditions from 200 to 60 ka suggests a similar plumbing system for the present-day Strombolian activity.  相似文献   

Comparative soil CO2 flux measurements and geostatistical estimation methods on Masaya volcano, Nicaragua     

Jennifer L. Lewicki  Deborah Bergfeld  Carlo Cardellini  Giovanni Chiodini  Domenico Granieri  Nick Varley  Cynthia Werner 《Bulletin of Volcanology》2005,68(1):76-90

We present a comparative study of soil CO₂ flux () measured by five groups (Groups 1–5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1–5 measured using the accumulation chamber method at 5-m spacing within a 900 m² grid during a morning (AM) period. These measurements were repeated by Groups 1–3 during an afternoon (PM) period. Measured ranged from 218 to 14,719 g m⁻² day⁻¹. The variability of the five measurements made at each grid point ranged from ±5 to 167%. However, the arithmetic means of fluxes measured over the entire grid and associated total CO₂ emission rate estimates varied between groups by only ±22%. All three groups that made PM measurements reported an 8–19% increase in total emissions over the AM results. Based on a comparison of measurements made during AM and PM times, we argue that this change is due in large part to natural temporal variability of gas flow, rather than to measurement error. In order to estimate the mean and associated CO₂ emission rate of one data set and to map the spatial distribution, we compared six geostatistical methods: arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods. While the total CO₂ emission rates estimated using the different techniques only varied by ±4.4%, the maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of , but a variety of geostatistical methods are appropriate to estimate the total CO₂ emission rate from a study area, which is a primary goal in volcano monitoring research.Editorial responsibility: H Shinohara  相似文献   

Environinformatics in ecological risk assessment of agroecosystems pollutant leaching     

Nazzareno Diodato  Michele Ceccarelli 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(4):292-300

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Experimental and Numerical Studies on the Seismic Response of R.C. Hollow Bridge Piers   总被引：3，自引：2，他引：1  

Gian?Michele?CalviEmail author  Alberto?Pavese  Alessandro?Rasulo  Davide?Bolognini 《Bulletin of Earthquake Engineering》2005,3(3):267-297

Appropriate seismic assessment of reinforced concrete bridges is an important challenge in structural engineering in consideration of the number and relevance of bridges built without applying advanced codes of practice and of the strategic role of transportation networks in modern economy. This paper focuses on some relevant aspects of the damage development and collapse modes of hollow piers, as commonly designed in the past. The following aspects have been considered: absence of confinement, inadequate shear strength, shifting of the critical section, insufficient length of lap splices. A series of experimental tests has been designed and performed; the capacity of predicting appropriate results of formulations recommended in codes of practice or proposed in recent research documents has been checked comparing experimental and analytical results.  相似文献   

An Algebraic Method to Compute the Critical Points of the Distance Function Between Two Keplerian Orbits     

Giovanni F. Gronchi 《Celestial Mechanics and Dynamical Astronomy》2005,93(1-4):295-329

We describe an efficient algorithm to compute all the critical points of the distance function between two Keplerian orbits (either bounded or unbounded) with a common focus. The critical values of this function are important for different purposes, for example to evaluate the risk of collisions of asteroids or comets with the Solar system planets. Our algorithm is based on the algebraic elimination theory: through the computation of the resultant of two bivariate polynomials, we find a 16th degree univariate polynomial whose real roots give us one component of the critical points. We discuss also some degenerate cases and show several examples, involving the orbits of the known asteroids and comets.   相似文献