Permeability versus depth in the upper oceanic crust; in situ measurements in DSDP Hole 504B, eastern Equatorial Pacific

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doi: 10.1029/JB090iB05p03659
Author(s): Anderson, Roger N.; Zoback, Mark D.; Hickman, Stephen H.; Newmark, Robin L.
Author Affiliation(s): Primary:
Lamont-Doherty Geol. Obs., Palisades, NY, United States
Other:
U. S. Geol. Surv., United States
Volume Title: Journal of Geophysical Research
Source: Journal of Geophysical Research, 90(B5), p.3659-3669. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227
Note: In English. Lamont-Doherty Geol. Obs.; Contrib. No. 3753. 25 refs.; illus. incl. 1 table, sketch maps
Summary: In situ permeabilities measured within the upper kilometer of oceanic crust in hole 504B on the south flank of the Costa Rica Rift decrease exponentially from 10-13 to 10-14 m2 in layer 2 A (the upper 150 m) to 10-15 to 10-17 m2 in layer 2B (150-550 m into basement), and to 10-17 m2 and lower in layer 2C(deeper than 550 m). We estimate the permeability (k) versus depth (z) to vary as k(z) = 0.11e(-z/50) × 10-12 m2. If this permeability versus depth function is representative of the oceanic crust in general, then hydrothermal convection would be vertically stratified, with the most vigorous circulation confined to the shallowest pillow basalt layers of the crust. The use of a full suite of geophysical logs (including borehole televiewer imagery; multichannel, full waveform sonic; nuclear; and variable spacing electrical resistivity logs) allows the characterization of the scale and interconnectedness of fractures, and the degree of infilling of these fractures by alteration minerals. At hole 504B, we observe a relationship between permeability and fracture porosity, determined from the geophysical logs. If fractures with similar aspect ratios are encountered at other oceanic sites, then prediction of the permeability of the oceanic crust to within an order of magnitude is possible from geophysical logs. At hole 395A in the Atlantic, for example, in situ permeability measurements yielded values similar to those predicted by the logging relationships established at hole 504B.
Year of Publication: 1985
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Crust; DSDP Site 504; Deep Sea Drilling Project; Depth; East Pacific; Equatorial Pacific; Fractures; IPOD; In situ; Interpretation; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Mechanical properties; Ocean Drilling Program; Oceanic crust; Pacific Ocean; Permeability; Physical properties; South American Pacific; South Pacific; Southeast Pacific; Tectonophysics; Upper crust; Well-logging
Coordinates: N010000 N013000 W0833000 W0840000
Record ID: 1985057412
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