To widen and further stimulate the use of noble-gas geochemistry in the sediment pore water the NoGOS (Noble Gases in Ocean Sediments as proxies for fluid transport at subduction zones and past climate conditions) project aims to systematically apply the analytical state-of-the-art to ocean sediments.
One target of the study is to quantify 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 likely to be hit by an earthquake in the future. The He isotopes should allow studying the release dynamics of deep fluids from solid earth close to these tectonically active regions and the relation of fluid emission 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 indicators of seismic activity.
Further, although recently noble gases in pore water of lacustrine sediments allow the determination of past 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. Hence, a second target of this project is to overcome the restrictions that still limit the application of noble gases in deep sediments from the oceans (and from the continents)
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 sediment cores.