Volatiles and Fluids in Subduction Zones

Core Objectives

For the proposed funding period 2008-2012, new and continued objectives are defined in adjustment to the scientific progress made by the SFB 574 in phases I and II and to the new target area at central Chile. As the initially formulated scientific concept has proved successful, the general structure and aims will remain, but will be refocused to expand the scope of investigations to subduction processes occurring at a broader range of tectonic settings. The Central American subduction zone is transitional between an oceanic and a continental setting; the oceanic end member of subduction is the focus of the US Margins program. The SFB has therefore chosen Central Chile to investigate a continental end member. Comprehensive geophysical data from previous projects will provide a basis for our future work. In this way, the scientific resources will be effectively used towards the aim of understanding global subduction zone processes.

Our research will address the following goals:

• Structure of the entire subduction system, including the oceanic slab and overriding plate, and the locations of seismogenesis, of fluid release and of magma production and storage
• Characterization of seismic activity, tectonic structure, fluid flow pathways and thermal structure
• Links between seismic activity and volcanism and related hazards
• Mass transfer between the down-going and overriding plate
• Hydrogeological properties of the ocean crust, its hydrothermal circulation and heat flow, and serpentinization of the subducting plate and overlying mantle
• Fluid formation processes, fluid vent sites and pathways
• The role of microbiological and geochemical parameters on benthic filtering mechanisms on the volatile exchange at the forearc sediment - deep ocean water interface
• Storage and release of fluids in sediments during diagenesis
• Reactions and depth intervals involved in the devolatilization of the slab, and the subsequent chemical and isotopic fractionation of fluids along different ascent pathways
• Evolution of the magmatic systems over a time scale of major changes in subduction regime
• Element fractionation during arc magma evolution and storage in crust of variable thickness, composition and structure; relationships between volatile fluxes and compositions in explosive volcanic eruptions and magma chamber conditions
• Short- and long-term effects of volatile emission from the forearc and the arc volcanoes on the marine and atmospheric/climatic environments
• The major final goal is a global budget of volatile cycling through the subduction system.