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Major, trace element, and Sr isotope geochemistry of surface and ground waters in the Chiavenna Valley (Sondrio, Northern Italy)
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The Chiavenna Valley (Sondrio, Northern Italy) is located in the Central Alps and is elongated along a NNW-SSE direction. Geologically, it consists of a poly-metamorphic sequence, which includes metasediments, metagranitoids, and ophiolites, intruded by Tertiary granitoid rocks. This work describes a geochemical investigation carried out in the Chiavenna Valley (Sondrio, Northern Italy) in 2000-2002, during which more than 200 running and ground waters were collected and analysed for major, trace elements, and Sr isotopes. The great majority of the analysed waters are of good quality and have low contents of those elements considered as contaminants or undesirable substances. Thus, the Chiavenna Valley can be regarded as a mostly low-pollution area. A few metals, i.e. As, Cd, Cr, and Pb, as well as the nitrogen species, are enriched close to urban centres or/and industrial areas, suggesting an anthropogenic source. Furthermore, Sr isotopes were used to evaluate the input due to the leaching of the country rocks.
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... Therefore, 87 Sr/ 86 Sr values are coherent with information provided by key elemental ratios useful to discriminate contributions by silicate rocks from the basement, that are prevalent in the upper Alpine part of the catchment (Piemonte), and carbonate rocks, that become widespread in the central part of the catchment where Po river receives contributions from the South-Alpine geological domain (Lombardia) and the Northern Apennines (Emilia-Romagna), where mafic ophiolite rocks are also present. Additional information can be retrieved by the 1/Sr (mg/L) vs 87 Sr/ 86 Sr diagram reported in Fig. 5, which highlights that the Po river water in UP has relatively low Sr elemental abundances coupled with highly radiogenic isotopic values, typical of weathering product of rocks included in the crystalline basement (Hosein et al., 2004;Pinarelli et al., 2014). Conversely, down flow in MP the Sr elemental concentration increases and the isotopic composition become less radiogenic, thus revealing more significant contributions from weathering of carbonate rocks. ...
... The choice of a water end-member draining silicate rocks is more challenging due to the high variability of lithotypes that include a wide spectrum of metamorphic and magmatic rocks. Within the Po river basin, reasonable candidates could be represented by the Pellice river and rivers from the Chiavenna valley (Pinarelli et al., 2014). The carbonate end-member is characterized by very high Sr concentration (1250 μg/l) coupled with low 87 Sr/ 86 Sr (down to 0.70773). ...
... Our results imply that the contribution of carbonate lithologies to the Sr budget seems to be subordinate, as also indicated by other authors that studied water geochemistry in Alpine catchments (Donnini et al., 2016). . Binary diagram reporting 1/Sr vs 87 Sr/ 86 Sr of the Po river waters: a) dashed lines represents the mixing between a carbonate water end member (C) and two distinct silicate water end members (S1 Pellice river; and S2 rivers from Chiavenna Valley, Pinarelli et al., 2014); percentages (%) represent the silicate contribution to the water chemistry. b) Inset showing mixing relation with seawater that occurs in the TP. ...
Strontium isotopic composition (⁸⁷Sr/⁸⁶Sr) of river water provides insight on the nature of rocks involved in the weathering processes and important constraints for reconstructing silicate versus carbonate weathering in large scale basins. New data, presented in the context of a geochemical map of the Po river basin, highlight that the Po river water evolves from the upper part of the catchment, where ⁸⁷Sr/⁸⁶Sr approaching 0.7097 relates to the weathering of igneous and metamorphic silicate rocks, to the middle part, where less radiogenic compositions (⁸⁷Sr/⁸⁶Sr ∼ 0.7089) are driven by the confluence of the tributaries draining Mesozoic carbonate rocks of the South Alpine domain and from inflow of Apennine streams characterized by less radiogenic Sr signatures due to weathering of marly sediments and mafic magmatic rocks. Down flow, the Sr isotopic compositions of Po river water rises at 0.7091 either by the confluence of the last Apennine tributary (Panaro, ⁸⁷Sr/⁸⁶Sr ∼ 0.7095) and/or by the possible contribution from hyporheic exchanges. Po river isotopic signatures reveal slightly more radiogenic ⁸⁷Sr/⁸⁶Sr in comparison to other important Alpine river systems (e.g. Danube, Rhine and Rhône), likely suggesting that silicate rocks are comparatively contributing more weathering byproducts in the Po basin.
La composizione chimica delle acque sotterranee costituisce uno dei fattori che, ove opportunamente interpretati, possono fornire indicazioni sulla storia e sulla evoluzione che queste hanno subito dal momento della infiltrazione nel terreno fino a quando raggiungono di nuovo la superficie. In particolare il ricorso alla sperimentazione di tecniche di analisi isotopica, nell’ambito dello studio dell’evoluzione chimica nel processo di interazione acqua-roccia costituisce da tempo un utile supporto alla caratterizzazione idrogeologica degli acquiferi. Nel presente lavoro, dopo avere brevemente riferito di alcuni fra i principali e più recenti studi che hanno sperimentato l’applicazione dello stronzio e del rapporto isotopico 87Sr/86Sr come traccianti di alcuni processi geologici ed idrogeologici, sono presentati i risultati ottenuti con l’impiego delle metodologie di analisi isotopica dello 87Sr/86Sr per distinguere l’origine ed il percorso delle acque sotterranee che circolano in due acquiferi geologicamente e litologicamente differenti. Nel primo caso le tecniche di analisi isotopica del rapporto 87Sr/86Sr sono state applicate al sistema idrogeologico relativo all’apparato vulcanico dei Colli Albani (Roma – Italia Centrale). In questo contesto geologico la distinzione dei percorsi seguiti dalle acque sotterranee risulta in molti casi di difficile interpretazione a causa della intensa variabilità litologica delle formazioni presenti, caratterizzate da differenti permeabilità. I risultati delle analisi dei rapporti isotopici dello 87Sr/86Sr eseguite su numerosi campioni prelevati in aree diverse del bacino investigato hanno consentito di riconoscere alcuni caratteri distintivi di queste acque. La tecnica utilizzata è stata quella di confrontare le indicazioni emerse dai valori del rapporto isotopico 87Sr/86Sr con i valori di altri costituenti chimici di queste acque che hanno funzionato da tracciante di riscontro per indirizzare e confermare le interpretazioni svolte. Nel secondo caso le analisi del rapporto isotopico 87Sr/86Sr è stata applicata allo studio delle acque che circolano all’interno di un bacino sedimentario quale è il bacino di Sangemini (Terni – Italia Centrale). La sperimentazione sviluppata in questo ambiente sembra consentire la distinzione delle litologie attraversate dalle acque lungo il proprio percorso sotterraneo. In particolare il rapporto isotopico 87Sr/86Sr misurato nei diversi campioni analizzati appare indirizzare verso una delle interpretazioni proposte in letteratura per la caratterizzazione della circolazione di queste acque sotterranee.
The Bergell pluton (Southern Switzerland, Northern Italy) : overview accompanying a geological-tectonic map of the intrusion and surrounding country rocks Schweizerische mineralogische und petrographische Mitteilungen, Vol.26 (1996) PDF erstellt am: 26.02.2010 Nutzungsbedingungen Mit dem Zugriff auf den vorliegenden Inhalt gelten die Nutzungsbedingungen als akzeptiert. Die angebotenen Dokumente stehen für nicht-kommerzielle Zwecke in Lehre, Forschung und für die private Nutzung frei zur Verfügung. Einzelne Dateien oder Ausdrucke aus diesem Angebot können zusammen mit diesen Nutzungsbedingungen und unter deren Einhaltung weitergegeben werden. Die Speicherung von Teilen des elektronischen Angebots auf anderen Servern ist nur mit vorheriger schriftlicher Genehmigung des Konsortiums der Schweizer Hochschulbibliotheken möglich. Die Rechte für diese und andere Nutzungsarten der Inhalte liegen beim Herausgeber bzw. beim Verlag. Abstract The major rock types and tectonic units compiled in the attached geological map (Berger, 1996) are briefly de¬ scribed. The tectonic units surrounding the Bergell pluton comprise the entire Stack of Alpine nappes from the Pen¬ ninic Adula-Gruf nappe to the Upper Austroalpine units and the Southern Alps. The text f acilitates access to the ex¬ isting literature, briefly summarizes the results of very recent work and serves as an introduction into the regional geology of the Bergell pluton and country rocks.
Building on the success of its 1993 predecessor, this second edition of Geochemistry, Groundwater and Pollution has been thoroughly re-written, updated and extended to provide a complete and authoritative account of modern hydrogeochemistry. Offering a quantitative approach to the study of groundwater quality and the interaction of water, minerals, gases, pollutants and microbes, this book shows how physical and chemical theory can be applied to explain observed water qualities and variations over space and time. Integral to the presentation, geochemical modelling using PHREEQC code is demonstrated, with step-by-step instructions for calculating and simulating field and laboratory data. Numerous figures and tables illustrate the theory, while worked examples including calculations and theoretical explanations assist the reader in gaining a deeper understanding of the concepts involved. A crucial read for students of hydrogeology, geochemistry and civil engineering, professionals in the water sciences will also find inspiration in the practical examples and modeling templates. © 2005 C.A.J. Appelo & D. Postma, Amsterdam, The Netherlands and Ben Akkerman collection Stedelijk Museum, Amsterdam. All rights reserved.
SmNd isotope data from garnets in ultrahigh-pressure (coesite-bearing) eclogite from the Western Alps were obtained to determine the age of peak metamorphism and exhumation rates of deeply buried oceanic crust in the Zermatt-Saas ophiolite complex. We report an exceptionally well-constrained SmNd isochron age of 40.6±2.6 Ma from the Lago di Cignana eclogite. Difficulties in dating Alpine eclogites using this method were overcome by using an HF acid-leaching procedure on garnet to remove mineral inclusions. The Zermatt-Saas rocks reached greenschist-facies conditions around 38 ± 2 Ma, on the basis of Rb-Sr whole rock-phengite isochrons. These data, combined with existing estimates of the pressure and temperature conditions of the eclogite, give an estimate for the initial exhumation rate of 10 to 26 km/m.y., depending on the inferred pressure for the recrystallization of phengite, followed by slow exhumation of 0.3 km/m.y. from 34 to 14 Ma. The initial exhumation rates at Lago di Cignana are among the highest yet determined for high-pressure terranes, and are well constrained because the age has been determined directly on the high-pressure assemblage. The rapid exhumation rates presented here place critical constraints on collisional tectonic models.
This paper presents a table of abundances of the elements in the various major units of the Earth's lithic crust with a documentation of the sources and a discussion of the choice of units and data.