Abstract

Integrated Ocean Drilling Program (IODP) Expedition 327 (summer 2010) was designed to resolve the nature of fluid-rock interactions in young, upper volcanic crust on the eastern flank of the Juan de Fuca Ridge. Expedition 327 drilled, cased and cored two new basement holes, conducted hydrogeologic experiments, and installed subseafloor borehole observatories (Circulation Obviation Retrofit Kits, CORKs). These CORKs were intended to allow borehole conditions to recover to a more natural state after the dissipation of disturbances caused by drilling, casing, and other operations; provide a long-term monitoring and sampling presence for determining fluid pressure, temperature, composition, and microbiology; and facilitate the completion of active experiments to resolve crustal hydrogeologic conditions and processes. Expedition 327 was followed (summer 2011) by R/V Atlantis Expedition AT18-07, with the remotely-operated vehicle (ROV) Jason, to service these CORKs, collect subseafloor pressure data, recover and deploy autonomous fluid and microbial samplers, collect large volumes of borehole fluids, and initiate a cross-hole hydrogeologic experiment using an electromagnetic flow meter. In addition, Atlantis Expedition AT18-07 refurbished an old CORK that could not be replaced during IODP Expedition 327, completing a critical part of the three-dimensional observation network that is currently being used to monitor a large-scale, directional formation response to long-term fluid flow from the crust.