Volatiles and Fluids in Subduction Zones

This proposal aims at collecting data offshore Guatemala and Costa Rica that will allow to understand the recent and long-term evolution of the Middle America Landbridge and in particular the mass flux into the subduction system. Offshore Costa Rica and Nicaragua numerous seismic profiles and a full multibeam bathymetric and magnetic coverage of the margin and adjacent ocean plate have yielded a rapid change in the concepts of the margin formation and evolution. That area of Middle America is currently considered an erosional type of margin whereas it was previously considered an accretionary margin. In contrast Guatemala has no high resolution bathymetric or magnetic coverage, although there exist numerous seismic profiles and perhaps the best set of drilling information across the entire continental slope for the whole Middle America. On the other hand, Costa Rica and Nicaragua lack of drilling information across much of the slope that can be used to decipher the long term evolution. The data to be gathered in Guatemala will permit to reinterpret the existing seismic and drill core data and to better understand the evolution of Middle America. A particularly unconstrained parameter is the amount of eroded material from the upper plate and the data to be collected in Costa Rica will be of great importance for a Complex Drilling Proposal that aims at collecting drill holes across the slope to study the subsidence history, and ultimately to drill a deep hole with a riser drill ship into the plate boundary at depths where eroded material is contributed to the subduction channel and where seismogenic slip occurs.

Working Area SO 173-2 + Trackplot