The permeability of young oceanic crust east of Juan de Fuca Ridge determined using borehole thermal measurements
Geophysical Research Letters, 24 (11):
1311--1314 (1997)Abstract
Temperature measurements made in Ocean Drilling Program (ODP) Hole
1026B, drilled into a sediment-buried basement ridge in 3.5 m.y.
old crust on the eastern flank of Juan de Fuca Ridge, revealed fluid
flow from the formation and into the overlying ocean. This flow indicates
that the upper basaltic crust at this site is naturally overpressured
relative to hydrostatic. This finding is consistent with output from
previously published numerical models of hydrothermal circulation
in the upper crust that include appropriate crustal geometry, sediment
thickness,;and basal heat flow. The fluid flowing into Hole 1026B
enters the hole through the upper 10 m of basalt below the sediment-basement
contact. The flow rate estimated from the thermal data (80-120 m/hr),
in combination with the inferred basement overpressure relative to
hydrostatic (about 20-30 kPa), was used to estimate the bulk permeability
of the shallowest oceanic crust: 5 to 9 x 10(-12) m(2). Such high
bulk permeability would allow regionally significant hydrothermal
circulation, consistent with thermal homogenization of upper basement
in this area.