The Ardea Basin fluid geochemistry, hydrogeology and structural patterns: new insights about the geothermal unrest activity of the Alban Hills quiescent volcano (Rome, Italy) and its geochemical hazard surveillance

摘要

A multidisciplinary task study was undertaken within the Ardea Basin, located at the South-Eastern boundary of the Alban Hills quiescent volcano (central Italy), encompassing fluid geochemistry, hydrogeology, structural geology and seismotectonics. The work is aimed at evaluating: i) the active geodynamics and geothermal unrest activity of the volcano; ii) the Natural Gases Hazard (CO_2, H_2S, CH_4 and other dangerous peri-volcanic gases); iii) the Rn-indoor hazard prone sectors; iv) the effects of anthropogenic depletion of shallow aquifers on the Natural Gases Hazard. The Ardea Basin, bordered by a complex fault system, and interpreted as a transfer related basin, is marked by a high CO_2 flux and by hydrothermal and gas-emitting sites, which were revisited during this work allowing new geothermometric and chemical equilibria evaluations and giving renewed insights into the geothermal reservoir. The pCO_2 and ~(222)Rn in groundwater were mapped to finally assess a moderate to low NGH, excluding the Fossignano and Zolforata pools. The main positive anomalies are located along the border of the basin, corresponding to NE transfer fault systems.