The hydrogeology of the oceanic crust influences numerous global processes and properties, including the thermal evolution of oceanic lithosphere, crustal alteration and the chemistry of crustal fluids, the nature and significance of subseafloor microbial ecosystems, tectonic and volcanic characteristics of active margins, and the creation of hydrate and ore deposits on and below the seafloor. Understanding these processes and properties has been a fundamental goal for scientific ocean drilling for over three decades, but progress has been limited in many cases by a vexing conundrum: drilling into the seafloor often causes open exchange of formation fluids and ocean bottom waters when coring penetrates through sediments and into permeable oceanic basement (e.g., Hyndman et al., 1976; Becker et al., 1983). Such open exchange strongly perturbs in situ conditions and limits validity of borehole measurements to resolve the natural state. These perturbations have greatly limited our ability to quantify fundamental physical, chemical, and microbiological parameters that control and are controlled by fluid flow within the oceanic crust.

Kastner, M., K. Becker, E.E. Davis, A.T. Fisher, H.W. Jannasch, E.A. Solomon, and G. Wheat. 2006. New insights into the hydrogeology of the oceanic crust through long-term monitoring. Oceanography 19(4):46–57, https://doi.org/10.5670/oceanog.2006.04.

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