CO2 degassing linked to late Quaternary seismicity
|Speaker:||Dr. Tonguc Uysal
Queensland Geothermal Energy Centre of Excellence, The University of Queensland,
Australia School of Earth Sciences, The University of Queensland, Australia.
|Time:||11 September 2013, 15:00–16:00|
|Venue:||Room U26, Geoscience Building, Stockholm University|
Fluid overpressures in excess of the hydrostatic are known to reduce shear stress causing fault failure. In regions of continental extension, deeply derived CO2 and meteoric water circulating to depths of 10–15 km below the earth surface are the major fluid sources; however, the cause and timing of CO2 and meteoric water accumulations has remained unexplored.
We obtained high-precision U-series ages of carbonate veins that filled spaces created by overpressurised CO2 –rich meteoric fluids during active normal faulting in southwest Turkey (Aegean region). Trace element, Sr, and O-C isotope data in combination of U-series dating reflect cyclic changes in fluid chemistry in relation to CO2 accumulation and CO2 exsolution following seismically triggered depressurisation. Timing of carbonate veining corresponds well to periods of low to transitional insolation in the Northern Hemisphere but is notably absent during periods of high insolation.
Although glacial episodes are generally associated with dry climatic conditions, there is substantial evidence suggesting that the eastern Mediterranean climate was wetter during the Last Glacial Maximum, which may also be the case for earlier periods of lower insolation. Whereas “background” tectonics is the ultimate driver of faulting, we argue climate-driven hydrological changes may have played an important role in modulating CO2-rich fluid circulation and reducing fault strength, triggering earthquakes.
|Host:||Professor Uwe Ring, Department of Geological Sciences, Stockholm University|