Correlation between seafloor heat flow and basement relief; observational and numerical examples and implications for upper crustal permeability

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doi: 10.1029/95JB00315
Author(s): Fisher, Andrew T.; Becker, Keir
Author Affiliation(s): Primary:
Indiana University, Department of Geological Sciences, Bloomington, IN, United States
Other:
University of Miami, United States
Volume Title: Journal of Geophysical Research
Source: Journal of Geophysical Research, 100(B7), p.12,641-12,657. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227
Note: In English. 72 refs.; illus., incl. sects., 1 table, sketch maps
Summary: There is a strong positive correlation between bathymetric and well-navigated heat flow data from the Galapagos Mounds hydrothermal area and the east flank of the Juan de Fuca Ridge. A similar correlation is apparent at Deep Sea Drilling Project/Ocean Drilling Program (DSDP/ODP) site 504, where it provides a constraint on the intensity and geometry of ridge flank hydrothermal circulation. We test the implications of this correlation with a hydrogeological model of the shallow crust that contains significant permeability mainly within a few thin layers (tens of meters thick) in the upper few hundred meters of basement, consistent with observations in DSDP/ODP holes into upper oceanic crust. These simulations are compared directly to others in which the same bulk permeability is represented more homogeneously within the upper crust. A model with thin permeable zones and subtle relief beneath a flat seafloor can explain the variations in seafloor heat flow observed on one part of the Juan de Fuca Ridge east flank, as can a model with a flat seafloor and basement top but relief within the most permeable zone. We explore the importance of layered heterogeneities versus explicit permeability anisotropy in these simulations through a series of parametric tests. Some form of permeability anisotropy appears to be required in order to achieve efficient lateral heat transport within the upper volcanic crust so as to produce the common seafloor heat flow-basement relief correlation. This permeability anisotropy may result directly from the primary architecture of the volcanic crust. Numerical results suggest that within an anisotropic system such as the upper oceanic crust, the length scale of heat flow variations (and therefore the length scale of underlying hydrothermal convection cells) is not an indication of the depth extent of fluid flow. Rather, the length scale of heat flow anomalies may reflect the length scale of relief along aquifer boundaries, while the depth of vigorous flow is constrained by the depth extent of significant permeability, and may be unresolvable with surface heat flow measurements.
Year of Publication: 1995
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Bathymetry; Circulation; Crust; DSDP Site 504; Deep Sea Drilling Project; East Pacific; Galapagos Rift; Heat flow; Hydrothermal vents; IPOD; Juan de Fuca Ridge; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Mounds; North Pacific; Northeast Pacific; Ocean Drilling Program; Ocean floors; Oceanic crust; Pacific Ocean; Permeability; Plate tectonics; Solutions; Spatial variations
Coordinates: N010900 N011600 W0834100 W0834800
Record ID: 1995053154
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