Irreversible water-rock mass transfer accompanying the generation of the neutral, Mg-HCO3 and high-pH, Ca-OH spring waters of the Genova province, Italy (Articolo in rivista)

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  • Irreversible water-rock mass transfer accompanying the generation of the neutral, Mg-HCO3 and high-pH, Ca-OH spring waters of the Genova province, Italy (Articolo in rivista) (literal)
Anno
  • 2001-01-01T00:00:00+01:00 (literal)
Alternative label
  • BRUNI J., CANEPA M., CHIODINI G., CIONI R., CIPOLLI F. LONGINELLI A.,MARINI L., OTTONELLO G., VETUSCHI ZUCCOLINI M. (2001)
    Irreversible water-rock mass transfer accompanying the generation of the neutral, Mg-HCO3 and high-pH, Ca-OH spring waters of the Genova province, Italy
    in Applied geochemistry
    (literal)
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  • BRUNI J., CANEPA M., CHIODINI G., CIONI R., CIPOLLI F. LONGINELLI A.,MARINI L., OTTONELLO G., VETUSCHI ZUCCOLINI M. (literal)
Pagina inizio
  • 455 (literal)
Pagina fine
  • 474 (literal)
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  • This work shows that the progressive evolution of the meteoric waters towards a Mg-rich component first and the C-OH facies afterwards can be attributed to low-temperature interaction of these meteoric waters with serpentinites and ultramafic rocks. These results are very important considering the role that these waters could have in the sequestration of anthropogenic carbon dioxide. (literal)
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  • 17 (literal)
Rivista
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  • Impact Factor 1,320 (literal)
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  • The interaction of meteoric waters with serpentinites and ultramafic rocks, determines a progressive evolution in the chemistry of the aqueous phase from immature Mg-rich, SO4_Cl facies of low salinity to: (1) an intermediate Mg_HCO3 facies and (2) to a mature Ca-OH type. The irreversible water-rock mass transfer leading to these chemical changes in the aqueous phase was simulated through reaction path modelling in reaction progress mode. The simulation was carried out in two steps. In the first step, the system was considered to be open with respect to CO2. In the second step the same rock was reacted with Mg-HCO3 water saturated with calcite, under closed-system conditions. The computed concentration of Ca, Mg, Ctot, and SiO2, pH values, and aMg2+/(aH+)2 and aCa2+/(aH+)2 ratios are fully comparable with analytical data, indicating that the computed irreversible water-rock mass transfer is a realistic simulation of that occurring in nature, at least as far as aqueous solution is concerned. These theoretical findings are in good agreement with field observations. Concerning the origin of CH4 in the high pH, Ca-OH waters, the occurrence of purely inorganic reduction of CO2 to CH4, can be ruled out since it would require a very long time. Bacterially mediated CO2-CH4 conversion is possible, but its occurrence and role cannot be evaluated on the base of available data. (literal)
Note
  • ISI Web of Science (WOS) (literal)
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  • J. BRUNI a), M. CANEPA a), G. CHIODINI b), R. CIONI c), F. CIPOLLI a), A. LONGINELLI d), L. MARINI a), G. OTTONELLO a), M. VETUSCHI ZUCCOLINI a) Dip. Per lo Studio del Territorio e delle sue Risorse, Università Genova, Corso Europa 26, Firenze, b) Osservatorio Vesuviano INGV, Via Diocleziano 328, Napoli, c) IGGI-CNR (ora IGG-CNR) Via Moruzzi 1, Pisa, d) Dip. Scienze della Terra, Università Parma, Parco Area delle Scienze 157 A, Parma. (literal)
Titolo
  • Irreversible water-rock mass transfer accompanying the generation of the neutral, Mg-HCO3 and high-pH, Ca-OH spring waters of the Genova province, Italy (literal)
Abstract
  • Abstract: In the recent survey of the spring waters of the Genova province, many neutral Mg-HCO3 waters and some high-pH, Ca-OH waters were found in association with serpentinites. All the springs are of meteoric origin as indicated by the stable isotopes of water and dissolved N2 and Ar. Interaction of these meteoric waters with serpentinites determines a progressive evolution in the chemistry of the acqueous phase from an immature Mg-rich, SO4-Cl facies of low salinity to an intermediate Mg-HCO3 facies (pH 7.0-8.5, PCO2 10-3.5_10-2.5 bar, Eh 150_250 mV), and to a mature Ca-OH facies (pH 10-12, PCO2 10-9.4_10-10.6 bar, Eh _ 390 to _ 516 mV). The irreversible water-rock mass transfer leading to these chemical changes in the aqueous phase was simulated through reaction path modelling, assuming bulk dissolution of a local serpentinite, and the precipitation of gibbsite, calcite, hydromagnesite, kaolinite, a montmorillonite solid mixture, a saponite solid mixture, sepiolite, and serpentinite. The simulation was carried out in two steps, under open-system and closed-system conditions with respect to CO2, respectively. The calculated concentrations agree with analytical data, indicating that the computed water-mass transfer is a realistic simulataion of the natural process. Moreover, the simulation elucidates the role of calcite precipitation during closed-system serpentinite dissolution in depleting the aqueous solution of C species, allowing the concurrent increment in Ca and the acquisition of a Ca-OH composition. Calcium-OH waters, due to their high pH, tend to absorb CO2, precipitating calcite. Therefore, these waters might be used to sequester anthropogenic CO2, locally preventing environmental impact to the atmosphere (literal)
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