Volatiles and Fluids in Subduction Zones

Major research objectives

The major aims of the field-based part of subproject C1 are to determine the origin of subduction zone fluids and the scale of fluid flow, to provide quantitative constraints on element cycling in subduction zones at depths of metamorphic reactions, and to constrain the contribution of volatile and fluid-mobile elements from the subducted slab to the mantle wedge at sub-arc depths. By determining fluid-solid and fluid-melt-solid partition coefficients, the experimental part of C1 will specify the element contributions of the different components of the subducting slab (slab mantle, basaltic oceanic crust, sediments) to the element budget (LILE, REE, HFSE) released from the slab.

In short, the combined field-based and experimental approach of subproject C1 has the following objectives:

1. Determining fluid source(s) and evaluating the scale of fluid flow in subduction zones
2. Constraining the magnitude and mechanisms of element cycling within the slab
3. Using halogens as tracers of subduction zone processes
4. Studying UHP suites to trace element contributions from the subducted slab to the mantle wedge at sub-arc depths
5. Characterizing the interactions of fluids/melts with the different lithological components of the subduction slab and elucidating their role as sources and sinks of LILE, REE and HFSE at sub-arc conditions
6. Specifying the lithological components of the overlying mantle wedge as sources and sinks of LILE, REE and HFSE at sub-arc conditions

Figure 1: Illustration of the study areas of the field-based part placed on a sketch of a subduction zone

Figure 2: Illustration of the objectives of the experimental work. Subduction zone with key metamorphic transformations is modified after Schmidt and Poli (1998).