Caratterizzazione idrogeochimica e rapporti isotopici 87Sr/86Sr nelle acque del distretto vulcanico del Monte Vulture (Basilicata): implicazioni idrogeologiche.

The paper describes the results of a study that was conducted to determine the relationship between hydrogeochemical composition and hydrogeological knowledge of the Mt. Vulture spring waters. Mount Vulture is a Pleistocene stratovolcano, located in the northeastern sector of the Basilicata region, along the external edge of the Apennine Chain, close to the Bradano river Miocene foredeep. Mount Vulture’s volcanic structure developed during the period 730 and 130 kyr BP, with a maximum activity period in the period of 800 kyr and 580 kys BP. Two hydrogeologically independent groundwater basins have been found: Monticchio-Atella and Melfi-Barile. In the Monticchio-Atella groundwater basin the representative hydrogeochemical type is sodium-bicarbonate, associated with high grade mineralization of groundwater. The latter is characterised by CO2 relative abundance (with values up to about 4000 mg/l), by electrical conductivity ranging between 200 and 19.000 μS/cm and by a temperature ranging between 10°C and about 20°C. The highest CO2 values have been detected in the Monticchio area, where the last eruption of Monte Vulture occurred. In the Melfi-Barile basin a different hydrogeochemical feature has been found. Calcium-bicarbonate and sodiumbicarbonate are the most represented hydrogeochemical types. The first, characterises a great part of Melfi-Barile groundwater basin, while the second can be detected only close to the aforesaid Toppo San Paolo structure (between Melfi and Rapolla towns) and in the area westward from Melfi. The strontium isotope ratios for four more anomalous samples in comparison with those representative of the volcanic rocks, showed a model with four sources with different strontium isotope ratios.