John Aiken (University of Oslo): "Acoustic detection of degassing events associated with peridotite alteration"
A link between seismicity and peridotite alteration at mid-ocean ridges has been hypothesized (Grevemeyer et al., 2013; Horning et al., 2018), and there is ample evidence that earthquakes caused by tectonic stress or thermal contraction may allow fluid percolation into peridotite to trigger serpentinization (Roumejon and Cannat, 2014; Aupart et al., 2021). However, a definitive observation of reaction-driven seismicity associated with the volume changes involved in serpentinization has never been made. Furthermore, the in-situ rate of this cracking process is poorly constrained. Assuming the simplified reaction: 2Fe2+O + H2O = Fe3+2O3 + H2, H2 gas should present itself in cracks due to reaction driven seismicity due to peridotite alteration. This gas would then migrate towards the surface via "degassing events".
This talk will present evidence of these degassing events using data from a nine month hydrophone array deployment using the Oman Multi-Borehole Observatory.
Paiman Shafabakhsh (University of Oslo): "Neutron imaging of reactive-mixing in porous rocks"
Fluid mixing can trigger reactions that lead to the alteration of porous medium geochemistry through precipitation/dissolution reactions. The local fluid and solute transport can be explored through flow visualization in laboratory experiments. Neutron imaging has proven very useful for in-situ studies of fluid flow imaging in porous rocks. We have performed a series of experiments (PSI, Switzerland) using neutron imaging to quantify how the velocity field of fluid evolves during porosity clogging. In the experiments, we have injected miscible fluids into sandstone samples which induces a chemical reaction that leads to calcite precipitation. At this stage, we are investigating the impact of porosity changes on the mixing of fluids.
The talk will be an overview of the experiments that we have done and the feasibility of time-lapse neutron imaging to visualize fluid mixing in rocks.
You will find the complete schedule for Njord Seminar Series spring '22 here.
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