ANALYTICAL ROUTE FOR HYDROGEOLOGICAL ANOMALIES: THE CASE OF A “WHITE” SPRING IN MINE VALLEY (LIVIGNO – ITALY)

The Livigno area represents a good test for the groundwater system reconstruction in the mountain environment because it has a complex geological and tectonical setting. In order to characterize this aquifer, a multidisciplinary approach, based on lithological, geochemical, hydrogeological and geo-structural methods, has been adopted. The Livigno area is located at 1800 m s.l.m. in the central Alps (northern Lombardy – Italy). For the tectonic setting this area is comprise between the Err Bernina system (Lower Australpine) and the Ortles-Quatervals system (Upper Austroalpine). The most important regional fault is represented by Zebrù fault. This fault divides the sedimentary rocks constituted by Fraele and Monte Motto limestone (Lias) to crystalline basement, which is constituted by “Bormio phyllades” and “Punta Rossa Formation”. To the north of Zebru fault system the Alpisella fault system outcrops and divides the Monte Motto limestone by Triassic dolomites and limestones. In the Livigno area 32 springs were sampled and analyzed. In particular, in the Mine Valley (in the south part of the Livigno area) there is a peculiar spring, named “White”, which shows a peculiar unknown whitish deposition. The first step was to characterize that compound through the integration of several analytical techniques: XRD, SEM-EDX, FTIR, ICP-MS. Using this approach we tried to have a complete picture of the problem, also matching results with hydro-geochemical information. Via the elemental analysis with EDX was identified the presence of aluminum, sulfur, oxygen and silicon. Subsequent analysis and bibliographic documentations [1] allowed us to identify the following structure tridecameric of Na[Al13O4(OH)24(H2O)12] (SO4)4 x 13H2O, and detect an anomaly in the presence of rare earth elements (REE) in the whitish compound. The second step was to analyze closely at Livigno water, which confirmed this peculiarity in REE in the “White” spring. [1] I.N. Bhattacharya, P.K. Gochhayat, P.S. Mukherjee, S. Paul, P.K. Mitra, Materials Chemistry and Physics 88 (2004) 32–40.