Large quantities of ocean-floor terrigenous and biogenic sediment, together with associated fluid, and hydration and alteration products, are annually added to the upper layer of igneous ocean crust and carried into subduction zones around the world. Although some of these materials are derived from atmospheric and hydrospheric sources, the great bulk are contributed to the ocean basin from continental or terrestrial areas. When drawn within the embrace of a subduction zone, the host igneous crust and its freight of additives begin a process of recycling or the transfer of material to the fluid reservoir of the ocean basin, the crustal mass of continents and island arcs, and to the underlying mantle from which the Earth’s terrestrial and fluid realms were derived. Recycling at ocean margins also includes large volumes of mostly sialic material tectonically eroded from the upper plate by the underthrusting action of the downgoing ocean plate.
Challenging scientific questions, including many that are relevant to societally important concerns, arise regarding the processes, solid-volume and geochemical mass fluxes, pathways, and fates of recycling materials. These wonderments in particular focus on the effects, consequences, and destinies of subducted continental components. To explore these issues and practical strategies to address them through ocean-floor drilling a JOI/USSAC-sponsored Recycling Workshop was convened. Driving this event was the notion that scientific ocean drilling can uniquely provide quantitative information on the composition and quantities of recycling components entering the subduction zone, refluxed to the ocean basin, accreted in the forearc, returned to the upper plate via magmatic or diapiric processes, or restored to the mantle with the subducting slab.
Workshop Report (pdf)
David W. Scholl, U.S. Geological Survey
Terry Plank, University of Kansas
Julie Morris, Washington University in St. Louis
Roland von Huene, GEOMAR
Michael Mottl, University of Hawaii