Scripps Institute of Oceanography, United States

Fluid sampling capabilities associated with borehole observatories (CORKs) are currently the best mechanism to collect fluids from subsurface hydrologic zones for evaluating the composition, evolution and consequence of fluid circulation in oceanic crust. These capabilities have evolved over the past two decades spanning the Ocean Drilling Program and the Integrated Ocean Drilling Program. Fluid sampling capabilities of the original CORK had a single Teflon tube that connected a valve at the seafloor and ended at depth in the formation. Through successes and disappointments coupled with community desires and efforts, significant iterations in CORK design and capabilities have led to a range of crustal fluid sampling systems. These iterations continue today with the development of new borehole capabilities, sensors and samplers. We present major iterations and transitions, highlighting the pros and cons of various designs, materials, and decisions. Although this evolution has taken years because of the infrequency of CORK deployments and sample recovery operations, we as a community are now in the position to provide groundbreaking results to enhance our understanding of subseafloor hydrogeology, crustal evolution, geochemical fluxes, microbial ecology and biogeochemical processes as indicated by the wealth of work to date and the complexity and flexibility of present and future designs.