10 - High Permeability of Young Oceanic Crust Constrained by Thermal and Pressure Observations

Abstract

This chapter discusses the high permeability of young oceanic crust constrained by thermal and pressure observation. Young oceanic crest is particularly heterogeneous, and it is reasonable to expect the scale dependence to be extreme. Permeabilities determined by pumping tests in deep-ocean boreholes are sensitive to a scale of tens to hundreds of meters and are found to be several orders of magnitude greater than those measured in core samples. The chapter reviews three novel strategies that provide permeability determinations that are sensitive to an even greater scale, and they indeed yield values that are much higher than the borehole determinations. The three strategies include: determining the degree to which the thermal regime of sediment-buried oceanic crest is nonconductive; determining the frequency dependence and scale of the diffusion of seafloor pressure variations; determining the dissipation rate following instantaneous changes in pressure generated internally by tectonic strain.