GeoActa Special Publication 1
2008
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GeoActa
an international Journal of Earth Sciences
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Rocco Giammetta, Antonio Telesca, Giovanni Mongelli
Dipartimento di Scienze Geologiche, Università degli Studi della Basilicata, Campus di Macchia Romana, 85100 Potenza, Italy. E-mail: mongelli@unibas.it
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Serpentinites-water interaction in the S. Severino area, Lucanian Apennines, southern Italy
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Abstract
Cataclastic serpentinites with Cr and Ni concentrations about 100 orders of magnitude higher than that of the Upper Continental Crust (UCC) crop out in the S. Severino area, southern Apennines. In this area several springs of both Mg-HCO3 and Ca-HCO3 type are present. The higher concentration of dissolved Ba and Sr and the lower value of aH4SiO4 in the Ca-rich waters are consistent with a model of circulation involving thickening of serpentinites in the southernmost part of the study area. Hydrochemical characteristics of the Ca-rich type are likely to derive from the interaction with calc-schists and not as a consequence of a prolonged interaction between meteoric waters and serpentinites.
The morphology of the area does not favour the formation of secondary minerals, including those that may adsorb mobile ions like Ni2+. This fact, coupled to the high concentration of Ni in the serpentinites, is the cause of 30 ppb concentration of Ni in a spring used for drinking supply, above the Italian maximum permissible level for drinking waters (20 ppb). Total Cr is below the Italian maximum permissible level for drinking waters.
Although further investigations are necessary about chromium speciation, in waters interacting with serpentinites in northern Apennines dissolved Cr occurs mostly in the highly toxic hexavalent form. This implies that waters from the S. Severino area may be affected by natural Cr (VI) pollution. A more detailed survey of natural pollution in the study area is claime.
Keywords: Serpentinites, Geochemical survey, Ni and Cr, Natural pollution
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