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doi:10.2204/iodp.proc.327.101.2011

Expedition 327 summary¹

Expedition 327 Scientists²

Abstract

Integrated Ocean Drilling Program (IODP) Expedition 327 and related experiments focus on understanding fluid-rock interactions in young upper ocean crust on the eastern flank of the Juan de Fuca Ridge, delineating the magnitude and distribution of hydrologic properties; the extent to which crustal compartments are connected or isolated (laterally and with depth); the rates and spatial extent of ridge-flank fluid circulation; and links between ridge-flank circulation, crustal alteration, and geomicrobial processes. Expedition 327 built on the achievements of Ocean Drilling Program (ODP) Leg 168, IODP Expedition 301, and subsequent submersible and remotely operated vehicle (ROV) expeditions. During earlier drilling expeditions, subseafloor borehole observatories (“CORKs”) were installed in basement holes to allow borehole conditions to recover to a more natural state after the dissipation of disturbances caused by drilling, casing, and other operations; to provide a long-term monitoring and sampling presence for determining fluid pressure, temperature, composition, and microbiology; and to facilitate the completion of active experiments to resolve crustal hydrogeologic conditions and processes.

During Expedition 327, two basement holes were cored and drilled at Site U1362. Hole U1362A was cored and drilled to 528 meters below seafloor (mbsf) (292 meters subbasement [msb]), geophysically logged and hydrologically tested, and instrumented with a multilevel CORK observatory. Hole U1362B was drilled to 359 mbsf (117 msb), tested with a 24 h pumping and tracer injection experiment, and instrumented with a single-level CORK observatory. Both CORK observatories include pressure and temperature monitoring and downhole fluid and microbiology sampling and experiments. Wellhead samplers will be added and a long-term cross-hole test will be initiated during a postdrilling ROV expedition scheduled for summer 2011. In addition, part of an instrument string deployed in Hole U1301B during Expedition 301 was recovered during Expedition 327, and a replacement string of thermal sensors was installed. Finally, a program of shallow sediment coring was completed adjacent to Grizzly Bare outcrop, a location where regional hydrothermal recharge occurs. Thermal measurements and analyses of pore fluid and microbiological samples from a series of holes aligned radially from the outcrop edge will elucidate rates of fluid transport and evolution during the initial stages of ridge-flank hydrothermal circulation.

¹Expedition 327 Scientists, 2011. Expedition 327 summary. In Fisher, A.T., Tsuji, T., Petronotis, K., and the Expedition 327 Scientists, Proc. IODP, 327: Tokyo (Integrated Ocean Drilling Program Management International, Inc.).
doi:10.2204/iodp.proc.327.101.2011

²Expedition 327 Scientists’ addresses.

Publication: 5 September 2011
MS 327-101

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