Evolution of permeability and fluid pathways in the uppermost oceanic crust inferred from experimental measurements on basalt cores

Abstract

To examine the systematic decrease in permeability with crustal age in the uppermost layer of the oceanic crust, we investigated the effect of mechanical compaction on the permeability of basalt cores from Hole 765D and Hole 456 of the Ocean Drilling Program. The results indicate that permeability systematically decreases with increasing confining pressure. However, the pressure effects observed in the laboratory experiments are insufficient to fully explain the result of in–situ measurements of permeability through the oceanic crust. The permeability of core samples is closely related to porosity, both of which reduce with increasing crustal age. We infer that the evolution of permeability of the oceanic upper crust could be controlled by a reduction in porosity due to carbonate mineral precipitation.