Off-axis hydrothermal circulation; parametric tests of a refined model of processes at Deep Sea Drilling Project/Ocean Drilling Program Site 504

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doi: 10.1029/93JB02741
Author(s): Fisher, A. T.; Becker, K.; Narasimhan, T. N.
Author Affiliation(s): Primary:
Indiana University, Department of Geological Sciences, Bloomington, IN, United States
Volume Title: Journal of Geophysical Research
Source: Journal of Geophysical Research, 99(B2), p.3097-3121. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227
Note: In English. 73 refs.; illus., incl. 4 tables, sects.
Summary: We have developed a refined model of coupled heat and fluid flow to numerically simulate off-axis hydrothermal circulation through the upper oceanic crust. The new representation includes mesh elements with curved sides and noncentered nodes. These curvilinear elements allow improved simulation of topography at the seafloor and within underlying sediment and basaltic layers. Curvilinear simulations of circulation at Deep Sea Drilling Project/Ocean Drilling Program site 504 confirm the broad conclusions derived from the rectilinear simulations of Fisher et al. (1990) but also suggest that permeability within the upper few hundred meters of crust around hole 504B must be concentrated within several narrow zones. This interpretation is consistent with core observations and wireline logs from hole 504B. Within these highly permeable zones, absolute permeability may be several orders of magnitude higher than the bulk permeability measured for the upper crust as a whole. A series of detailed parametric simulations was conducted to determine the quantitative importance of basal heat flow, seafloor bathymetry, basement relief, and differential sediment thickness in modifying the geometry and intensity of off-axis hydrothermal circulation. These studies reveal that basement relief and differential sediment thickness are more important than seafloor bathymetry in enhancing off-axis convection within the seafloor. Observed natural correlations between seafloor bathymetry and heat flow may exist because bathymetry is a proxy for the other two important parameters, basement relief and differential sediment thickness. Off-axis convection at geochemically significant velocities is possible even with heat input appropriate for some of the oldest oceanic crust. A thick sediment layer over older crust may cause enough conductive refraction at the seafloor to mask the variations in seafloor heat flow often associated with off-axis hydrothermal convection. Copyright 1994 by the American Geophysical Union.
Year of Publication: 1994
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; Equatorial Pacific; Heat flow; Hydrothermal conditions; IPOD; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Models; Movement; Numerical models; Ocean Drilling Program; Ocean floors; Oceanic crust; Pacific Ocean; Permeability; Thermal conductivity; Upper crust
Coordinates: N011335 N011338 W0834348 W0834357
Record ID: 1995037373
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.