Design, deployment, and status of borehole observatory systems used for single-hole and cross-hole experiments, IODP Expedition 327, eastern flank of Juan de Fuca Ridge

Abstract

Integrated Ocean Drilling Program (IODP) Expedition 327 installed two new subseafloor borehole observatory systems ("CORKs") in 3.5 m.y. old upper ocean crust on the eastern flank of Juan de Fuca Ridge in Holes U1362A and U1362B. Expedition 327 participants also recovered part of an instrument string previously deployed in a CORK in Hole U1301B and deployed a short replacement string. These observatories are part of a network of six CORKs that was designed to monitor, sample, and complete multidisciplinary cross-hole experiments. We present an overview of project goals and describe the design, construction, and deployment of new CORK systems. We also provide an update on the status of preexisting CORK systems as of the start of Expedition 327. Additional CORK servicing and sampling are scheduled for summer 2011 and 2012, including a long-term free-flow perturbation experiment that will test the large-scale directional properties of the upper ocean crust around the observatories. Motivation, background, and overview of experimental design Long-term borehole observatory systemsSubseafloor borehole observatory systems ("CORKs") are designed to (1) seal one or more depth intervals of a borehole so that thermal, pressure, chemical, and microbiological conditions can equilibrate following the dissipation of drilling and other operational disturbances; (2) facilitate collection of fluid and microbiological samples and temperature and pressure data using autonomous samplers and data logging systems; and (3) serve as longterm monitoring points for large-scale crustal testing, including formation response to perturbation experiments Davis et al., 1992a;. The development of CORK systems was motivated by the desire to address a broad range of scientific objectives that have been the focus of scientific ocean drilling for decades, particularly those associated with submarine hydrogeology, lithospheric and hydrothermal fluid evolu-

Time-lapse characterization of hydrothermal seawater and microbial interactions with basaltic tephra at Surtsey Volcano

“…Assessments of the geochemical composition of hydrothermal seawater, reaction progress associated with water-rock-microbiological interaction and inorganic chemical energy available in the hydrothermal system, will be combined with equilibrium reaction models to describe affinities for chemosynthesis and tephra alteration and provide constraints on the potential energy available for microbial metabolism. The design of the Surtsey subsurface observatory is similar to that of observatories installed during recent IODP expeditions (Fisher et al, 2011;Edwards et al, 2012). After drilling, incubation chambers (e.g., Toner et al, 2013) will be deployed inside slotted sections of the aluminum casing to facilitate further microbial, geochemical and hydrological studies in isolated sections of the drill hole above sea level (< 60-70 m below the surface (mbs) at the drill site), in the highest temperature regime (70-140 mbs), and below the high temperature regime (> 140 mbs) (Fig.…”

Scientific Drilling

“…336 and previously on Exp. 327 and 328 (see technical descriptions in Davis et al, 2010;Fisher et al, 2011;Edwards et al, 2012b). The instrument includes batteries, electronics, two absolute pressure gauges (Paroscientific Model 8B-7000; one to monitor the formation and the other to monitor the seafloor), a data logger (set to sample pressure and temperature every two minutes like the Exp.…”

Summary of carbon, nitrogen, and iron leaching characteristics and fluorescence properties of materials considered for subseafloor observatory assembly

“…Subseafloor borehole observatories (CORKs) have been used successfully for several decades to study hydrological and geochemical dynamics in deep oceanic crust Fisher et al, 2011). Essentially, CORKs are instrumented experimental wells deployed in boreholes created through ocean drilling that consist of a series of pipes extending below the seafloor that house the instruments and sensors, seals at the seafloor and various depths to isolate intervals, and a wellhead protruding above the seafloor.…”

“…These experiments include the use of nonreactive coated tubes for pumping fluids from basement formations as well as the deployment of colonization experiments within the boreholes (Cowen et al, 2012;Fisher et al, 2011Fisher et al, , 2005Orcutt et al, 2011;Smith et al, 2011). During Integrated Ocean Drilling Program (IODP) Expedition 327 to the Juan de Fuca Ridge flank, several new CORKs that were installed featured steel pipe that had been coated with epoxy resins to limit corrosion .…”