Juan de Fuca Ridge Flank

The hydrogeologic architecture of basaltic ocean crust: Compartmentalization, anisotropy, microbiology, and crustal-scale properties on the eastern flank of Juan de Fuca Ridge, eastern Pacific Ocean

IODP Expedition 327 co-chief scientists: Andrew Fisher (University of California, Santa Cruz) and Takeshi Tsuji (Kyoto University)

Integrated Ocean Drilling Program (IODP) Expedition 327 (July 5 - September 4, 2010) is part of a series of long-term multidisciplinary experiments that build from technical and scientific achievements and lessons learned during Ocean Drilling Program (ODP) Leg 168 and IODP Expedition 301, on the eastern flank of the Juan de Fuca Ridge.

Index map showing the location of Expedition 327 primary drill sites, in the Second Ridge (SR) area, about 100 km east of the Juan de Fuca Ridge. A secondary target for Expedition 327 operations is adjacent to Grizzly Bare (GRB) outcrop, where regional hydrothermal fluids are thought to recharge the oceanic crustal aquifer.

The main goals of these experiments are 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 ("CORKs") in two new holes in oceanic crust (at proposed Site SR-2);
• replace an observatory in an existing hole (ODP Hole 1027C) after deepening that hole, to facilitate long term monitoring;
• recover and replace an instrument string deployed in one of the Expedition 301 subseafloor borehole observatories; and
• complete remedial cementing of another Expedition 301 CORK that is not sealed at the seafloor.

Instruments to be deployed within new CORK systems will include temperature and pressure loggers to monitor multiple depths, long-term fluid samplers, and microbiological incubation substrate. Much of Expedition 327 will be dedicated to preparation and installation of subseafloor observatory installation operations, but science activities will also include ~200 m of basement coring at proposed Site SR-2 and ODP Site 1027, limited downhole logging, and single-hole hydrologic testing in the crust. Sediment coring may also occur around Grizzly Bare outcrop, 52 km to the SSW, where hydrothermal fluids recharge the crust.

Following Expedition 327, a series of non-drilling expeditions will conduct single- and crosshole hydrologic experiments using a submersible/remotely operated vehicle, with the complete network of six observatory systems functioning as perturbation and monitoring points (see figure below). Expedition 327 will include an international education and outreach program intended to develop tools and techniques that facilitate the communication of exciting scientific discoveries to a broad audience, build educational curricula, and create media products to achieve critical outreach goals for the complete experimental program.

Perspective diagram showing relative locations of drill holes, each of which will contain a long-term, subseafloor observatory (CORK), as used for cross-hole pressure testing and a tracer injection experiment. The color contours in this figure indicate depth to the top of basement, which contains the primary hydrothermal aquifer. Original image courtesy J. Cowen, University of Hawaii.

Learn more about the science and outreach associated with our North Pond expedtions from the links below.

NEXT FOLLOWUP EXPEDITION: UNOLS EXPEDITION, July 13-26, 2013
AT 25-04 RV Atlantis/ROV Jason II: Hydrogeologic, geochemical, and microbiological experiments in young ocean crust of the northeastern Pacific Ocean using subseafloor observatories
Chief scientist: Andy Fisher
[Scientific Prospectus, 10.1 MB] [UNOLS-JASON Expedition website]

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