68. FLUID PERMEABILITY OF OCEANIC BASALTS

The liquid permeabilities have been determined for 10 basalt samples from DSDP Hole 418A. Fresh basalts have an average permeability of 5.2 × 10~cm, but the presence of secondary minerals has a substantial effect upon the permeabilities of altered basalts. Smectite clays infilling the pore spaces of the basalts decrease the specific permeability slightly, and samples with calcium carbonate veinlets had permeabilities that were 2 to 4 orders of magnitude greater than for fresh basalts. A positive correlation of decreasing permeability of fresh basalts with depth position in the drill hole corresponds closely with decreasing bulk porosity with depth.