6 septembre 2021, 13h amphithéâtre du CRPG | Carolina Dantas Cardoso (CRPG)
Continuous isotopic tracing of crustal fluids transfer related to natural (seismic/volcanic) or anthropogenic hazards
Summary : Noble gases, unlike most stable isotopes or major elements used as geochemical tracers, are less susceptible to water/rock interactions and display widely variable ratios among the Earth reservoirs, making them good tracers of source and fluid interactions. 3He/4He ratios from groundwater in Italy are monitored by INGV through discrete sampling at seismically and volcanically active zones where they identified correlations between variations in 3He/4He ratios and earthquakes and eruptions. An uninterrupted sampling system has the potential to improve the monitoring at sites of interest, providing key information on processes of short timescales and their long-term geochemical backgrounds. Continuous sampling is possible using SPARTAH, an apparatus for automatic groundwater sampling. This project aims to comprehend the exchange and transfer of fluids to the surface in short timescales. With this knowledge, we hope to better constrain the sources and mechanisms involved in volcanic and seismogenic systems and potentially improve the forecasting of such hazards. Our current targeted areas are in northern (borehole HA-01) and southern (boreholes BA-01 and TH-13) Iceland. In the latter sites, monitoring is recent and we do not yet have any results. At HA-01, we started discrete weekly sampling in June 2020, shortly after an earthquake swarm, and continuous sampling with SPARTAH in September 2020. In addition to the monitoring, we surveyed the area around HA-01 for δ34S, δ18O, δ2H, δ13C, 3He/4He, 4He/20Ne, and major and trace elements to better characterize the region and interpret our monitoring data. In this presentation I’ll show you some of our preliminary results from Iceland, besides going briefly over some of our next projects.