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Noble gases in ocean sediments as proxies for fluid transport at subduction zones and past climate conditions (NoGOS)
Date du début: 1 janv. 2014, Date de fin: 30 juin 2016 PROJET  TERMINÉ 

In order to widen and further stimulate the use of noble-gas geochemistry in the sediment pore water the proposed research aims to systematically apply the analytical state-of-the-art to ocean sediments.On the one hand the researcher will study the fluid transport in forearc regions off shore Japan. A first sampling region is located close to the epicentre of the devastating Tohoku earthquake occurred in 2011 and the second sampling region close to the Nankai trough which is expected to hit by an earthquake in the future. The He isotopes should allow for the first time studying the release dynamics of deep fluids from solid earth close to these tectonically active regions and its relation to seismic activity. Moreover, the investigation of the noble-gas signature in the pore water will set a first data basis to interpret noble-gas anomalies in regions where major earthquakes occurred or are expected and will be a further step towards the use noble gases in terrestrial fluids as indicator of seismic activity.Further, although recently noble gases in pore water of lacustrine sediments allow the determination of lake level and salinity fluctuations, and the reconstruction of past environmental conditions and past eutrophic states in lakes, ocean sediments are still not fully assessable by present experimental techniques - in particular when considering the degassing affecting ICDP/IODP deep-drilling sediments. Based on the experience gained in the field of oceanography during this fellowship, the researcher's internationally acknowledged experimental skills will allow to overcome the restrictions that still limit the application of noble gases in deep sediments from the oceans (and from the continent) by developing a new in situ sampling technique. This technique, conceived, produced, and tested in collaboration with other international partners will allow climate reconstruction using noble gases dissolved in the pore water of deep-drilling ocean sediment cores.