14:30 〜 14:45
[SGC32-04] Fluid migration and geochemical processes in seismically active regions: a case study in Southern Italy
★Invited Papers
キーワード：CO2 output, Gas-Water-Rock Interaction, Low & High Frequency Monitoring, Geochemical Modeling, Near Fault Observatories
Nowadays, the availability of a new generation of field deployable geochemical instrumentations allows novel approaches in the monitoring of seismically active regions. These instruments are providing novel long-time series that can be interpreted in a multidisciplinary context.
This development follows the vision of the Near Fault Observatories (NFO) community, according to which a better understanding of the earthquake nucleation and more in general deformation processes deserves the contribution of diverse disciplines (e.g. seismology, geodesy, geophysics and geochemistry).
However, it is worth noting that only a limited number of geochemical parameters can be acquired and transmitted in real time to open access gateways (e.g., FRIDGE-http://fridge.ingv.it). Moreover, the variety of parameters that can be monitored on the field is limited if compared to the ones that can be derived in the laboratory by analysing the sampled fluids. Hence, a combination of these two approaches (long vs short time series) is necessary for a more efficient monitoring of ongoing crustal processes.
We focused on the degassing process of deep and shallow volatiles, particularly Helium (He) and Carbon Dioxide (CO2), in active areas to investigate the gas-water-rock interaction at depth and create a geochemical model of fluids circulation as basic information for the interpretation of the long data series.
Southern Italy, known for its seismic activity with catastrophic events in the recent past (e.g., Irpinia 1981), provides a remarkable case study, because here it exists the Irpinia NFO and a network for high frequency geochemical monitoring is growing up.
Regional-scale outgassing of deep-sourced CO2, with a mantle-derived component (indicated by He isotopes), is facilitated by fault systems despite the absence of active volcanic centres within a considerable distance (>10 km). In addition to the study of dissolved and free gases, the analysis of calcite veins within fault zones, provides valuable insights into the history of paleo-fluid flow and mineral deposition. These veins serve as records of past fluid migration pathways and aid in understanding the temporal evolution of fault systems and their role in facilitating fluid transport through the crust over time.
Our investigation confirms the conclusions in Caracausi et al. (2022), according to which seismic events cause rock deformation and fracturing along fault zones, regulating the episodic release of He. Furthermore, the use of regional geophysical models that encompass the entire crust allows us to clearly delineate the processes involving fluid-rock interactions that govern the chemical and isotopic composition of degassing CO2 (Buttitta et al., 2023).
In conclusion, the study presents evidence that active tectonic domains can release CO2 and He at rates comparable to volcanic regions. This highlights their crucial role in the global geochemical cycle and emphasises the potential impact of fluid migration through fault systems to the assessment of the CO2 emission in atmosphere. The novelty and originality of this study stem from solving secondary processes within the crust that modify the chemical and isotopic composition of fluids, accounting for specific local conditions at depth such as temperature, pressure, salinity, and lithology. These processes have a significant impact on the calculation of CO2 emitted to the surface.
Furthermore, it represents a base-study to organise the activities of high frequency geochemical monitoring in the seismic regions of Italy. In fact, this study allows to create a 3D model about the sources of fluids and their transfer to surface, where they can be collected and monitored by the NFO offering to the world-wide scientific community, long data series for better understanding the processes related to the generation of damaging earthquakes (Chiaraluce et al., 2022)
Caracausi, et al., (2022) C E & E
Buttitta, et al., (2022) STOTEN
Chiaraluce, et al., (2022) AdG
This development follows the vision of the Near Fault Observatories (NFO) community, according to which a better understanding of the earthquake nucleation and more in general deformation processes deserves the contribution of diverse disciplines (e.g. seismology, geodesy, geophysics and geochemistry).
However, it is worth noting that only a limited number of geochemical parameters can be acquired and transmitted in real time to open access gateways (e.g., FRIDGE-http://fridge.ingv.it). Moreover, the variety of parameters that can be monitored on the field is limited if compared to the ones that can be derived in the laboratory by analysing the sampled fluids. Hence, a combination of these two approaches (long vs short time series) is necessary for a more efficient monitoring of ongoing crustal processes.
We focused on the degassing process of deep and shallow volatiles, particularly Helium (He) and Carbon Dioxide (CO2), in active areas to investigate the gas-water-rock interaction at depth and create a geochemical model of fluids circulation as basic information for the interpretation of the long data series.
Southern Italy, known for its seismic activity with catastrophic events in the recent past (e.g., Irpinia 1981), provides a remarkable case study, because here it exists the Irpinia NFO and a network for high frequency geochemical monitoring is growing up.
Regional-scale outgassing of deep-sourced CO2, with a mantle-derived component (indicated by He isotopes), is facilitated by fault systems despite the absence of active volcanic centres within a considerable distance (>10 km). In addition to the study of dissolved and free gases, the analysis of calcite veins within fault zones, provides valuable insights into the history of paleo-fluid flow and mineral deposition. These veins serve as records of past fluid migration pathways and aid in understanding the temporal evolution of fault systems and their role in facilitating fluid transport through the crust over time.
Our investigation confirms the conclusions in Caracausi et al. (2022), according to which seismic events cause rock deformation and fracturing along fault zones, regulating the episodic release of He. Furthermore, the use of regional geophysical models that encompass the entire crust allows us to clearly delineate the processes involving fluid-rock interactions that govern the chemical and isotopic composition of degassing CO2 (Buttitta et al., 2023).
In conclusion, the study presents evidence that active tectonic domains can release CO2 and He at rates comparable to volcanic regions. This highlights their crucial role in the global geochemical cycle and emphasises the potential impact of fluid migration through fault systems to the assessment of the CO2 emission in atmosphere. The novelty and originality of this study stem from solving secondary processes within the crust that modify the chemical and isotopic composition of fluids, accounting for specific local conditions at depth such as temperature, pressure, salinity, and lithology. These processes have a significant impact on the calculation of CO2 emitted to the surface.
Furthermore, it represents a base-study to organise the activities of high frequency geochemical monitoring in the seismic regions of Italy. In fact, this study allows to create a 3D model about the sources of fluids and their transfer to surface, where they can be collected and monitored by the NFO offering to the world-wide scientific community, long data series for better understanding the processes related to the generation of damaging earthquakes (Chiaraluce et al., 2022)
Caracausi, et al., (2022) C E & E
Buttitta, et al., (2022) STOTEN
Chiaraluce, et al., (2022) AdG