This proposal is to conduct hydrogeologic experiments in shallow ocean crust on the east flank of the Juan de Fuca Ridge using borehole instruments installed in IODP drill holes on Expedition 327, July-September, 2010. The proposed work will be the first to run a long-term cross-well hydrogeologic test in ocean crust. The data will be used to examine fluid and microbial characteristics within the shallow ocean crust and their relationships. Three-dimensional numerical modeling will evaluate coupled fluid-thermal-chemical flow within the crust.
Broader Impacts This project will train graduate and undergraduate students and also includes a major outreach effort that leverages off of an existing education and outreach program already in place for an IODP expedition in 2010.
This project supported acquisition of downhole pressure and temperature records from long-term hydrogeological "CORK" observatories installed into the seafloor in 2004 and 2010 during Expeditions 301 and 327 of the Integrated Ocean Drilling Program. The installation site is in young oceanic crust on the eastern flank of the Juan de Fuca Ridge in the northeast Pacific, within Canadian territorial waters. Here there is very active subseafloor fluid flow in the permeable oceanic basement beneath an unusually thick and impermeable layer of sediments. The CORK experiments seal several boreholes drilled into the oceanic basement, with downhole sensors for measuring temperature and pressure and sampling fluid chemistry and microbiological activity associated with the active fluid flow. The CORK experiments were installed by the scientific drillship JOIDES Resolution and then were revisited multiple times using manned and unmanned submersibles for downloading data and acquiring samples. This project specifically represented the University of Miami – Rosenstiel School of Marine and Atmospheric Science contribution to the multi-institution collaborative NSF-funded Juan de Fuca CORK project led overall by Dr. Andrew T. Fisher of the University of California, Santa Cruz. The specific objectives of this project included providing necessary equipment and overseeing retrieval of the CORK pressure and temperature data during two research cruises using the unmanned remotely-operated vehicle (ROV) Jason in summers of 2011 and 2013. The second cruise was originally scheduled for summer of 2012 but had to be postponed a year due to a major breakdown of the ship; as a result, this project was extended for one year at no additional cost. The pressure and temperature data were successfully recovered from all the Juan de Fuca Ridge CORKs as scheduled on both cruises. These data indicate that most of these CORKs have slightly overpressured and highly permeable basement, so they can produce copious amounts of formation fluids for geochemical and microbiological sampling by colleagues with related NSF support. The CORK pressure and temperature data also provide important constraints in quantifying the value of the basement permeability – a measure of the ability of the formation to allow through-flow of fluids and thus the most important formation parameter in understanding the fluid flow system. This aspect is explored in two 2013 research papers in the journal Geochemistry, Geophysics, Geosystems (citations below) that acknowledge support from this NSF grant. Another set of collaborative NSF grants to a subset of the same investigators has supported a final research cruise in summer of 2014 to the Juan de Fuca CORKs using the manned submersible Alvin. This cruise collected more formation pressure and temperature data, which will be made publicly available online within a year via the Oceans Network Canada/NEPTUNE Canada website. Publications acknowledging this NSF grant: Becker, K., Fisher, A.T., and Tsuji, T., 2013, New packer experiments and borehole logs in upper oceanic crust: evidence for ridge-parallel consistency in crustal hydrogeological properties, Geochemistry, Geophysics, Geosystems, 14, 2900-2915, doi: 10.1002/ggge.20201 Winslow, D.M., Fisher, A.T., and Becker, K., 2013, Characterizing borehole fluid flow and formation permeability in the ocean crust using linked analytic models and Markov chain Monte Carlo analysis, Geochemistry, Geophysics, Geosystems, 14, 3857-3874, doi: 10.1002/ggge.20241
