Passive, off-axis convection through the southern flank of the Costa Rica rift

Journal Article · Sun Jun 10 00:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB06p09343· OSTI ID:5009423

Fisher, A T; Becker, K ^[1]; Narasimhan, T N ^[2]; Langseth, M G ^[3]; Mottl, M J ^[4]

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1. Univ. of Miami, FL (United States)
2. Lawrence Berkeley Laboratory, Berkeley, CA (United States)
3. Lamont-Doherty Geological Observatory, Palisades, NY (United States)
4. Univ. of Hawaii, Honolulu (United States)

Pore fluids are passively convecting through young oceanic sediments and crust around Deep Sea Drilling Project (DSDP) site 504 on the southern flank of the Costa Rica Rift, as inferred from a variety of geological, geochemical, and geothermal observations. The presence of a fluid circulation system is supported by new data collected on Ocean Drilling Program (ODP) leg 111 and a predrilling survey cruise over the heavily sedimented, 5.9 Ma site; during the latter, elongated heat flow anomalies were mapped subparallel to structural strike, with individual measurements of twice the regional mean value, and strong lateral and vertical geochemical gradients were detected in pore waters squeezed from sediment cores. Also, there is a strong correlation between heat flow, bathymetry, sediment thickness, and inferred fluid velocities up through the sediments. Although the forces which drive passive circulation are not well understood, it has generally been thought that the length scale of heat flow variations provides a good indication of the depth of hydrothermal circulation within the oceanic crust. The widely varied geothermal and hydrogeological observations near site 504 are readily explained by a model which combines (1) basement relief, (2) irregular sediment drape, (3) largely conductive heat transfer through the sediments overlying the crust, and (4) thermal and geochemical homogenization of pore fluids at the sediment/basement interface, which results from (5) topographically induced, passive hydrothermal circulation with large aspect ratio, convection cells. This convection involves mainly the permeable, upper 200-300 m of crust; the deeper crust is not involved.

• OSTI ID: 5009423
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:B6; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
COSTA RICA
RIFT ZONES
HEAT FLOW
HYDROLOGY
BOREHOLES
CONVECTION
CORRELATIONS
FLOW RATE
FLUID FLOW
GEOCHEMISTRY
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
HEAT TRANSFER
HYDROTHERMAL SYSTEMS
OCEANIC CRUST
PERMEABILITY
RESERVOIR FLUIDS
SEDIMENTS
THICKNESS
WELL DRILLING
CAVITIES
CENTRAL AMERICA
CHEMISTRY
DEVELOPING COUNTRIES
DIMENSIONS
DRILLING
EARTH CRUST
ENERGY SYSTEMS
ENERGY TRANSFER
FLUIDS
GEOTHERMAL SYSTEMS
LATIN AMERICA
MASS TRANSFER
580000* - Geosciences