Geochemical study of Central-Eastern Lombard Prealps mineral and thermal springs

Abstract

Geochemical characteristics of mineralized waters of Central Eastern Lombard Prealps (Italy) have been studied with specific atten-tion to processes that originate waters with a complex composition. To achieve the objectives of this study, 34 samples of mineral waters were collected in the area of interest. These samples were analyzed for deter-mination of main cations, anions and some trace elements. Elaboration of analytical data allowed to classify the waters, to identify geochemical processes that originate them and to simulate reaction paths of the dif-ferent water groups. Reaction paths have been simulated with PhreeqcI geochemical software related to: (i) the evolutionary paths related to the dedolomitization process that starting from with bicarbonate-calcium waters originates sulphate-calcium waters with high magnesium con-tents (Boario, Angolo, Tartavalle and Salice di Prestine mineral wa-ters), (ii) the processes that generate sulphate-calcic waters that flow from the chalky outcrops of the Brembana and Camonica valleys and (iii) the processes that give rise to the basic sulphurous waters with bicarbonate-sodium composition of the Imagna, Brembilla and Cavallina valleys. Finally, by means of geothermometric techniques and mixing models, San Pellegrino and Bracca thermal waters have been studied: tempera-ture of the thermal reservoir that feeds them has been calculated and its depth has been estimated based on local geothermal gradient.