Integrated Ocean Drilling Program, United States

Integrated Ocean Drilling Program (IODP) Expedition 327 is a critical part of a long-term multidisciplinary experiment that builds from technical and scientific achievements and lessons learned during Ocean Drilling Program (ODP) Leg 168 and IODP Expedition 301. The main goal of this experiment is to evaluate formation-scale hydrogeologic properties (transmission and storage) within oceanic crust; determine how fluid pathways are distributed within an active hydrothermal system; establish links between fluid circulation, alteration, and geomicrobial processes; and determine relations between seismic and hydrologic anisotropy. During Expedition 327 we will install subseafloor observatories in two new holes in oceanic crust (at proposed Site SR-2); replace an observatory in an existing hole (ODP Site 1027) to facilitate longterm monitoring; recover and replace an instrument string deployed in one of the Expedition 301 subseafloor borehole observatories (CORKs); and complete remedial cementing of another Expedition 301 CORK that is not sealed at the seafloor. Following Expedition 327, submersible expeditions will allow us to conduct single- and crosshole hydrologic experiments using a complete network of six observatory systems that use CORKs as perturbation and monitoring points. This expedition will be dominated by subseafloor observatory installation operations, and hence science activities will consist of approximately 200 m of basement coring at proposed Site SR-2 and ODP Site 1027, downhole logging, and drill string hydrologic testing. Expedition 327 will also include an international education and outreach program intended to develop tools and techniques that facilitate the communication of exciting scientific drilling results to a broad audience, build educational curricula, and create media products that will help achieve critical outreach goals.