We present the results of a hydrogeochemical survey of the Bagni di Lucca area, a thermal district in the Serchio Valley, one of the areas of highest seismic risk in Tuscany, Italy. The aim of the survey was to identify a suitable site to be monitored for geochemical precursors of earthquakes. Based on hydrogeological and geochemical features, the Bernabò spring emerged as a proper candidate site for the installation and testing of an automatic monitoring station equipped with specific sensors for the continuous measurement of selected physical-chemical parameters (temperature, pH, electrical conductivity, redox potential).

Since late 2002, a continuous automatic monitoring network is operating in Tuscany, Central Italy, to investigate the geochemical response of selected aquifers to local seismic activity. The monitoring is aimed at identifying possible earthquake geochemical precursors. The network is currently constituted by six stations, all equipped with sensors for the measurement of temperature, pH, redox potential, electrical conductivity, CO2 and CH4 dissolved concentration, that have been installed in the areas of highest seismic risk of the region. By combining geochemical data gathered from the automatic station of Gallicano (Garfagnana, Northern Tuscany), and obtained via chemical analyses of spring water samples collected during periodic field surveys in the area surrounding this station, the most significant aspects of the deep fluid circulation paths feeding the Gallicano thermo-mineral system have been investigated, and the geochemical baseline of the Gallicano spring defined. The CO2 continuous signal recorded by the Gallicano automatic station has been then processed over the period 2003–2013 in the search for anomalies possibly related to local seismic activity. A substantial anomaly in CO2 content has been observed at Gallicano in conjunction with the Alpi Apuane earthquake (M=5.2) of 21 June 2013.

A multidisciplinary integrated approach was used to study the structural architecture influencing the circulation pattern of geothermal fluids in the Equi Terme area (NW Alpi Apuane, Tuscany). Geological-structural surveys were carried out to define the structural setting of the area and to characterize geometries and kinematics of fault systems. Chemical (major components) and isotopic analyses (delta O-18 parts per thousand, delta H-2 parts per thousand, H-3, delta C-13 parts per thousand([DIC]), delta S-34 parts per thousand([SO4]))) were performed on thermal water and cold springs. A geophysical survey was also conducted by means of both Magnetotelluric and Electrical Resistivity Tomography methodologies, in order to gain insight into the resistivity distribution at depth and to indirectly image the subsurface structure. This multidisciplinary approach proved to be a powerful tool, since it unravels the complexity of this natural geothermal system and provides useful suggestion for reconstructing the fluid circulation outflowing at the Equi Terme thermal spring. Results pointed out how the E-W oriented fault system (the Equi Terme Fault) play a key role in controlling the thermal groundwater outflow, and the chemical-physical features of this resource. This structural lineament separates high permeability carbonate complexes (footwall), in which both shallow and deep flow paths develop, from a medium-low permeability succession (hangingwall) that contains evaporitic formations from which thermal water acquires a high salinity and a composition of the Na-Cl (Ca-SO4) type. During the uprising along the fault system, the thermal water is also affected by a mixing with shallow fresh-cold waters that lead to a strong seasonal variation in the chemical-physical properties of the thermal springs.

We present the results of a hydrogeochemical survey of 111 springs and wells from Magra Valley, a seismic area located in northern Tuscany, Italy. This survey was aimed at defining the geochemical background and the underground fluid circulation scheme of an area currently investigated for earthquake precursory phenomena, with the final goal of identifying a suitable location for installation of a continuous automatic monitoring station for the remote control of hydrogeochemical parameters. Six springs of the project were identified suitable for the purpose, and the Equi Na-Cl-type spring emerged as the best candidate for the installation of a monitoring station.

Architettura tridimensionale e caratterizzazione strutturale del sistema di faglie a basso angolo della Val di Lima (Appennino Settentrionale, Italia).In Val di Lima e esposto un sistema di faglie a basso angolo che scompone la Falda Toscana, una unita tectonostratigrafica anchimetamorfica che affiora nella parte interna dell'Appennino Settentrionale. Il sistema di faglie e caratterizzato da due segmenti principali, entrambi con geometria ramp-and-flat e cinematica top-to-NE. La presenza sia di geometrie sottrattive che di ripetizioni tettoniche indica la presenza, nel sistema di faglie, di rampe che tagliano sia down-section che upsection nella direzione di trasporto tettonico. La restaurazione dei rigetti ha permesso di stimare un trasporto tettonico minimo di circa 5 km per i due segmenti principali del sistema di faglie.La zona di danneggiamento dei contatti tettonici principali e stata caratterizzata, prestando particolare attenzione al ruolo dei fluidi. In affioramenti selezionati e risultato evidente il ruolo di barriera rappresentato dalle faglie, con la risultante compartimentazione dei fluidi al footwall del contatto tettonico principale. La sovrappressione dei fluidi ha quindi influenzato i processi di deformazione attivi e la localizzazione del taglio.

An integrated approach to the study of the Central Apennines thrust system has been conducted, combining together new field, geophysical, organic matter maturity and mineralogical datasets. The area comprises one of the most studied basins of the Central Apennines: the Laga basin. It developed during the Messinian time and represents the link between the internal, uplifted, Lower Miocene fold-and-thrust belt to the west, and the external, more recent part of the chain, buried below a thick pile of synorogenic, Plio-Pleistocene clastic deposits of the Periadriatic basin to the east. The Laga basin is filled by several turbiditic sedimentary sequences, largely studied in the past and mostly included into the Laga Formation, classically considered the fill of a deep marine foredeep basin connected to the flexure of the subducted Adriatic lithosphere under the Apennines. Our results clearly suggest that during Messinian, the main factor controlling depositional system architectures was thrusts activity, which governed the localization of the main depocenter in the basin and its eastward space-time migration. The occurrence of thrust activity during deposition of most of the Laga basin sedimentary succession suggests that it can be described as an internally deformed but not migrating sedimentary wedge, having features recording the transition from foredeep to wedge top depozone.

We present a multidisciplinary integrated study performed to get insights into circulation pattern of geothermal fluids uprising in the Equi Terme area (Alpi Apuane, Tuscany). Geological-structural surveys were carried out to define the structural setting of the area and to characterize geometries and kinematics of fault-fracture systems. Chemical and isotopic analyses were carried out on thermal water and cold springs. Samples were repeatedly collected in the different seasons, measuring temperature, electrical conductivity, pH and total alkalinity. Furthermore, a geophysical survey has been carried out in order to get insights into the resistivity distribution at depth. The geophysical approach used MagnetoTelluric (MT) and Electrical Resistivity Tomography (ERT). This multidisciplinary approach proved to be a powerful tool, since it unravels the high complexity of this natural geothermal system and provides useful hints in order to reconstruct the complex fluid circulation pattern feeding the Equi Terme thermal spring.

The characteristics of a shallow-level shear zone that is representative of the deformation in the external sectors of the Northern Apennine fold-and-thrust belt are described. The characterization involved an integrated approach using microstructural analysis of deformation fabrics, vitrinite reflectance measurements, XRD analysis on clay minerals and carbon and oxygen stable isotopes analyses. This data set provides the evidence that the thrust was active at very shallow depths (ca. less than 3 km), with maximum paleotemperatures ranging from 60° to 100–110 °C. The regime during fault activity evolved through cycles of compaction and dilation linked to transient build up of fluid overpressure and injection. The alternating cycles of fluids supply generated a fault-fracture mesh with a complex network of blocky and striped veins that formed at temperatures ranging from 150° to 200 °C, not compatible with the conditions in the host rocks. This evidence implies that the shear zone was flooded by hot fluids coming upward from diagenetic and low-grade metamorphic dehydration of clay minerals active at deeper structural levels. The fluids were thus highly channelled and focused where deformation also focused, producing a local pronounced isotopic difference between fluids and host rock.

In the Trasimeno Lake area (Umbria Region), several thrust sheets belonging to the Sansepolcro-Monte Filoncio and Rentella Units, are interposed between the Tuscan Nappe (in the hanging-wall) and the Umbria-Romagna Unit (in the footwall). The thrust sheets succession of the Sansepolcro-Monte Filoncio Unit is made up of Rupelian-Chattian Scaglia toscana Fm. and Chattian-Aquitanian foredeep deposits of Macigno Fm.; the base of the siliciclastic succession becomes gradually younger eastward. The compositional mode of the fine-grained rock fragments in the arenaceous turbidites is comparable with that of the upper part of the Macigno Fm. in the Tuscan Nappe.The succession of the Rentella Unit includes Rupelian-Aquitanian Monte Rentella Fm. and Aquitanian-Burdigalian foredeep siliciclastic turbidites of the Montagnaccia Fm.. In the lower portion of the Montagnaccia Fm. a level of black cherty horizons is present, as detected in all Aquitanian-Burdigalian successions of the Northern Apennines. The compositional mode of the fine-grained rock fragments in the turbidites is comparable with that of Marnoso-Arenacea Fm..All these data allow an Oligocene-Miocene paleogeographic reconstruction of the Northern Apennines foredeep. Based on the age, the compositional mode and structural position, the Rentella and Sansepolcro-Monte Filoncio Units can be compared to the Carigiola and Acquerino Units cropping out in the Tuscan-Emilian Apennines.

A multi-method investigation (structural analysis, organic matter thermal maturity and clay mineralogy) was carried out on highly deformed foredeep successions in the Northern Apennine with special regard to shear zones in the Lago Trasimeno area (Rentella Unit) to unravel the main structural mechanisms and the thermal condition of the Miocene accretionary processes of the Northern Apennines belt. The Rentella Unit consists of a foredeep succession deposited in a paleogeographic domain between the Tuscan and the Umbria-Marche Domains. Meso- and microstructural data indicate shear planes compatible with C-planes (N160°, 45°SW). C-planes veins show dilational jogs and a staircase shape coherent to a top-to-the-NE sense of shear. Type II calcite twins in the shear zone associated veins suggest temperatures of 150-200°C. Temperature-dependent clay minerals and vitrinite reflectance indicate lower maximum paleo-temperatures (<100-110°C) in the early diagenesis and in the immature to early-mature stages of hydrocarbon generation. Thermal parameters suggest the development of the shear zone in the foredeep deposits at shallow depths (<3 km). Hot fluids coming from deeper structural levels within the collisional prism caused higher temperatures recorded in calcite twins of the shear zone veins.