We report the results of a systematic study carried out on the fracture systems exposed in the Sierra de La Candelaria anticline, in the central Andean retrowedge of northwestern Argentina. The aim was to elaborate a kinematic model of the anticline and to assess the dimensional and spatial properties of the fracture network characterizing the Cretaceous sandstone reservoir of the geothermal system of Rosario de La Frontera. Special regard was devoted to explore how tectonics may affect fluid circulation at depth and control fluids' natural upwelling at surface. With this aim we performed a Discrete Fracture Network model in order to evaluate the potential of the reservoir of the studied geothermal system. The results show that the Sierra de La Candelaria regional anticline developed according to a kinematic model of transpressional inversion compatible with the latest Andean regional WNW–ESE shortening, acting on a pre-orogenic N–S normal fault. A push-up geometry developed during positive inversion controlling the development of two minor anticlines: Termas and Balboa, separated by further NNW–SSE oblique-slip fault in the northern sector of the regional anticline. Brittle deformation recorded at the outcrop scale is robustly consistent with the extensional and transpressional events recognized at regional scale. In terms of fluid circulation, the NNW–SSE and NE–SW fault planes, associated to the late stage of the positive inversion, are considered the main structures controlling the migration paths of hot fluids from the reservoir to the surface. The results of the fracture modeling performed show that fractures related to the same deformation stage, are characterized by the highest values of secondary permeability. Moreover, the DFN models performed in the reservoir volume indicates that fracture network enhances its permeability: its secondary permeability is of about 49 mD and its fractured portion represents the 0.03% of the total volume

The Adria microplate is the foreland of the oppositely verging Apennines and Alps or Dinarides fold-thrust belts associated to the related subduction zones. Along its western margin, the Adria plate hosts the active Northern Apennines accretionary prism, which is buried under the Adriatic Sea and the Po Plain. The interpretation of seismic reflection profiles and borehole data allowed us to define the geometry of the transition from the Apennines fold-thrust belt to its undeformed foreland. Moreover, continuous GPS (CGPS) data from offshore hydrocarbon platforms anchored to the seabed of the northern Adriatic plate allow to measure present-day kinematics. Although the CGPS signals are affected by non-tectonic components associated with hydrocarbon extraction, the integration of geodetic analysis, subsurface geological reconstructions, and analytical modeling allowed us to constrain the ongoing tectonic activity. Shortening is currently accommodated by aseismic slip along the basal detachment, likely accumulating elastic energy along the frontal ramp that may eventually seismically slip. Our multidisciplinary study suggests that the study area may not be sheltered from relevant seismic sequences similar to the Mw 6 Emilia 2012 events and that the occurrence of potential seismogenic sources in the area should be carefully evaluated. Similar studies may be useful to constrain the present-day activity in other marine areas and to identify potential and hitherto unrecognized seismogenic sources along the entire Apennines belt and other accretionary prisms worldwide.

This study presents new stratigraphic, structural and hydrogeological data on the Tocomar geothermal volcanic area (Puna plateau, Central Andes, NW Argentina), together with preliminary geochemical and magnetotelluric data. The main geothermal reservoir is located within the fractured Pre-Palaeozoic-Ordovician units. The reservoir is recharged by meteoric waters. Geothermal fluids upwell where main regional structures intersect secondary structures associated with the development of the Tocomar basin. Preliminary data indicate a reservoir temperature of ∼ 200°C and a local geothermal gradient of ∼ 130°C/km associated with the Quaternary volcanic activity in the Tocomar area

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Cap rock characterization of geothermal systems is often neglected despite fracturing\ud may reduce its efficiency and favours fluid migration. We investigated the siliciclastic cap\ud rock of Rosario de La Frontera geothermal system (NW Argentina) in order to assess its\ud quality as a function of fracture patterns and related thermal alteration.\ud Paleothermal investigations (XRD on fine-grained fraction of sediments, organic matter\ud optical analysis and fluid inclusions on veins) and 1D thermal modelling allowed us to\ud distinguish the thermal fingerprint associated to sedimentary burial from that related to fluid\ud migration.\ud The geothermal system is hosted in a Neogene N-S anticline dissected by high angle\ud NNW- and ENE-striking faults. Its cap rock can be grouped into two quality categories:\ud ● rocks acting as good insulators, deformed by NNW–SSE and E–W shear\ud fractures, NNE-SSW gypsum- and N-S-striking calcite-filled veins that\ud developed during the initial stage of anticline growth. Maximum paleotemperatures\ud (<60 °C) were experienced during deposition to folding phases.\ud ● rocks acting as bad insulators, deformed by NNW-SSE fault planes and NNWand\ud WNW-striking sets of fractures associated to late transpressive\ud kinematics. Maximum paleo-temperatures higher than about 115 °C are linked to\ud fluid migration from the reservoir to surface (with a reservoir top at maximum depths\ud of 2.5 km) along fault damage zones. This multi-method approach turned out to be particularly useful to trace the main\ud pathways of hot fluids and can be applied in blind geothermal systems where either\ud subsurface data are scarce or surface thermal anomalies are lacking

Deep fluid circulation likely triggered the large extensional events of the 2016–2017 Central Italy seismic sequence. Nevertheless, the connection between fault mechanisms, main crustal‐scale thrusts, and the circulation and interaction of fluids with tectonic structures controlling the sequence is still debated. Here, we show that the 3D temporal and spatial mapping of peak delays, proxy of scattering attenuation, detects thrusts and sedimentary structures and their control on fluid overpressure and release. After the mainshocks, scattering attenuation drastically increases across the hanging wall of the Monti Sibillini and Acquasanta thrusts, revealing fracturing and fluid migration. Before the sequence, low‐scattering volumes within Triassic formations highlight regions of fluid overpressure, which enhances rock compaction. Our results highlight the control of thrusts and paleogeography on the sequence and hint at the monitoring potential of the technique for the seismic hazard assessment of the Central Apennines and other tectonic regions.

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