INGEIS   05370
INSTITUTO DE GEOCRONOLOGIA Y GEOLOGIA ISOTOPICA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Geochemical and Isotopic Composition of Deep Thermal Aquifers. Southern Córdoba province Argentina. Preliminary
Autor/es:
CABRERA, ADRIANA; DAPEÑA, CRISTINA; BLARASIN, MONICA; PANARELLO, HECTOR; MATTEODA, EDEL
Lugar:
Bariloche, Río Negro, Argentina
Reunión:
Simposio; VI South American Symposium on Isotope Geology; 2008
Institución organizadora:
INGEIS (CONICET-UBA)
Resumen:
The
studied zone is situated in the Pampean Plain (Córdoba, Argentina),
where the groundwater resources of major interest are confined-deep
aquifers, which are often used due to the bad quality of the unconfined
aquifer. The objective of this work is to present a preliminary
hydrogeochemical and isotopic model of deep aquifers in the studied
area. The hydrogeological and isotopica analyses were made according
to conventional methodologies. Hydrochemical maps, Schoeller diagrams,
box plots and dendrograms (Q mode) were obtained. The isotopic
analysis (18O and 2H) were very significant in
the assessment of these deep aquifers since the few sedimentological
and hydraulic data of the deepest layers made difficult a hydrogeologic
classification. The deepest sediments (120 m to 350 m), fluvial
materials with wide-ranging texture, were assigned to Upper Tertiary
units. Three deep multilayered aquifer systems were defined taking
into account depths and groundwater quality: a semiconfined lower deep
system, a confined system with low confinement grade and a confined
sytem with high confinement grade. Although all of them contain fresh
waters (l<
1800 µS/cm), hypothermal and mesothermal (29ºC - 36ºC) and sodium
sulphate type waters, the first (120 m - 200 m) and second (225 m - 290
m) levels displayed the most saline waters (l > 1800 µS/cm) and the greatest concentrations of As and F- and values of δ18O between -5,4 and -4,6 and of δ2H
between -32 y -25, which are similar to the phreatic system, being
able to suppose a feasible hydraulic connection between aquifers. The
isotopic composition of local and western allochthonous streams and the
characteristics of deepest confined levels (225 m -340 m), with always
artesian wells, better groundwater quality (l < 1800 µS/cm) and different isotopic composition (δ18O≈ -6.6; δ2H≈ -43) allow us to assume recharge sectors located outside the studied area, probably in the perimountain western region.