Hydrothermal Circulation

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Robert A. Sohn - One of the best experts on this subject based on the ideXlab platform.

  • Crustal structure of the Trans-Atlantic Geotraverse (TAG) segment (Mid-Atlantic Ridge, 26°10'N): Implications for the nature of Hydrothermal Circulation and detachment faulting at slow spreading ridges
    Geochemistry Geophysics Geosystems, 2007
    Co-Authors: J. Pablo Canales, Robert A. Sohn, Brian J. Demartin
    Abstract:

    New seismic refraction data reveal that Hydrothermal Circulation at the Trans-Atlantic Geotraverse (TAG) Hydrothermal field on the Mid-Atlantic Ridge at 26°10′N is not driven by energy extracted from shallow or mid-crustal magmatic intrusions. Our results show that the TAG Hydrothermal field is underlain by rocks with high seismic velocities typical of lower crustal gabbros and partially serpentinized peridotites at depth as shallow as 1 km, and we find no evidence for low seismic velocities associated with mid-crustal magma chambers. Our tomographic images support the hypothesis of Tivey et al. (2003) that the TAG field is located on the hanging wall of a detachment fault, and constrain the complex, dome-shaped subsurface geometry of the fault system. Modeling of our seismic velocity profiles indicates that the porosity of the detachment footwall increases after rotation during exhumation, which may enhance footwall cooling. However, heat extracted from the footwall is insufficient for sustaining long-term, high-temperature, Hydrothermal Circulation at TAG. These constraints indicate that the primary heat source for the TAG Hydrothermal system must be a deep magma reservoir at or below the base of the crust.

  • crustal structure of the trans atlantic geotraverse tag segment mid atlantic ridge 26 10 n implications for the nature of Hydrothermal Circulation and detachment faulting at slow spreading ridges
    Geochemistry Geophysics Geosystems, 2007
    Co-Authors: Pablo J Canales, Robert A. Sohn, Brian J. Demartin
    Abstract:

    New seismic refraction data reveal that Hydrothermal Circulation at the Trans-Atlantic Geotraverse (TAG) Hydrothermal field on the Mid-Atlantic Ridge at 26°10′N is not driven by energy extracted from shallow or mid-crustal magmatic intrusions. Our results show that the TAG Hydrothermal field is underlain by rocks with high seismic velocities typical of lower crustal gabbros and partially serpentinized peridotites at depth as shallow as 1 km, and we find no evidence for low seismic velocities associated with mid-crustal magma chambers. Our tomographic images support the hypothesis of Tivey et al. (2003) that the TAG field is located on the hanging wall of a detachment fault, and constrain the complex, dome-shaped subsurface geometry of the fault system. Modeling of our seismic velocity profiles indicates that the porosity of the detachment footwall increases after rotation during exhumation, which may enhance footwall cooling. However, heat extracted from the footwall is insufficient for sustaining long-term, high-temperature, Hydrothermal Circulation at TAG. These constraints indicate that the primary heat source for the TAG Hydrothermal system must be a deep magma reservoir at or below the base of the crust.

  • Three‐dimensional tomographic velocity structure of upper crust, Coaxial segment, Juan de Fuca Ridge: Implications for on‐axis evolution and Hydrothermal Circulation
    Journal of Geophysical Research: Solid Earth, 1997
    Co-Authors: Robert A. Sohn, Spahr C. Webb, John A. Hildebrand, Bruce D. Cornuelle
    Abstract:

    Three-dimensional models of compressional velocity and azimuthal anisotropy from tomographic inversions using 23,564 ocean bottom seismometer P wave arrivals define systematic lateral variations in seismic structure of the CoAxial segment of the Juan de Fuca Ridge (JdFR). Over much of the segment the across-axis structure is roughly axisymmetric, characterized by a progressive increase in dike velocities moving away from the ridge axis. This trend is most apparent in the basal dikes, where on-axis velocities are about 800 m/s slower than those measured elsewhere within the rift valley. The on-axis sheeted dikes also exhibit ridge-oriented azimuthal anisotropy, with a peak-to-peak amplitude of about 600 m/s. Outboard of the rift valley, beneath ridge flanks with fault scarps, velocities in the upper 1500 m of crust are reduced. The maximum amplitude of this anomaly is about 700 m/s, located near the top of the sheeted dikes. Variations in the three-dimensional velocity model are believed to reflect changes in crustal porosity, from which we infer an axisymmetric porosity model for seismic layer 2 of the CoAxial segment. As the crust ages, the evolution of layer 2 porosity could occur in the following way: (1) the porosity of zero-age, on-axis dikes is set at formation by the contraction of molten material, (2) Hydrothermal alteration fills pore spaces as the dikes move away from the center of the axial valley, and (3) normal faulting on the ridge flank scarps opens fractures and increases porosity of the upper dikes as they move off-axis. At the north end of the segment, dike velocities are several hundred meters per second slower, on average, and the across-axis structure is lost. The transition from a coherent, aligned seismic structure to a less distinct pattern with reduced velocities may represent a shift from magmatic to amagmatic extension moving away from the Cobb hotspot on the ridge axis. The porosity structure we have derived for the CoAxial segment suggests an alternative to the usual Hydrothermal Circulation model of cross-axis convection cells. A Circulation model with along-axis convection cells located entirely within the axial valley appears to be more compatible with our data.

  • three dimensional tomographic velocity structure of upper crust coaxial segment juan de fuca ridge implications for on axis evolution and Hydrothermal Circulation
    Journal of Geophysical Research, 1997
    Co-Authors: Robert A. Sohn, Spahr C. Webb, John A. Hildebrand, Bruce D. Cornuelle
    Abstract:

    Three-dimensional models of compressional velocity and azimuthal anisotropy from tomographic inversions using 23,564 ocean bottom seismometer P wave arrivals define systematic lateral variations in seismic structure of the CoAxial segment of the Juan de Fuca Ridge (JdFR). Over much of the segment the across-axis structure is roughly axisymmetric, characterized by a progressive increase in dike velocities moving away from the ridge axis. This trend is most apparent in the basal dikes, where on-axis velocities are about 800 m/s slower than those measured elsewhere within the rift valley. The on-axis sheeted dikes also exhibit ridge-oriented azimuthal anisotropy, with a peak-to-peak amplitude of about 600 m/s. Outboard of the rift valley, beneath ridge flanks with fault scarps, velocities in the upper 1500 m of crust are reduced. The maximum amplitude of this anomaly is about 700 m/s, located near the top of the sheeted dikes. Variations in the three-dimensional velocity model are believed to reflect changes in crustal porosity, from which we infer an axisymmetric porosity model for seismic layer 2 of the CoAxial segment. As the crust ages, the evolution of layer 2 porosity could occur in the following way: (1) the porosity of zero-age, on-axis dikes is set at formation by the contraction of molten material, (2) Hydrothermal alteration fills pore spaces as the dikes move away from the center of the axial valley, and (3) normal faulting on the ridge flank scarps opens fractures and increases porosity of the upper dikes as they move off-axis. At the north end of the segment, dike velocities are several hundred meters per second slower, on average, and the across-axis structure is lost. The transition from a coherent, aligned seismic structure to a less distinct pattern with reduced velocities may represent a shift from magmatic to amagmatic extension moving away from the Cobb hotspot on the ridge axis. The porosity structure we have derived for the CoAxial segment suggests an alternative to the usual Hydrothermal Circulation model of cross-axis convection cells. A Circulation model with along-axis convection cells located entirely within the axial valley appears to be more compatible with our data.

Brian J. Demartin - One of the best experts on this subject based on the ideXlab platform.

Glenn A Spinelli - One of the best experts on this subject based on the ideXlab platform.

  • modeled temperatures and fluid source distributions for the mexican subduction zone effects of Hydrothermal Circulation and implications for plate boundary seismic processes
    Geochemistry Geophysics Geosystems, 2016
    Co-Authors: Matthew Perry, Glenn A Spinelli, Ikuko Wada
    Abstract:

    In subduction zones, spatial variations in pore fluid pressure are hypothesized to control the sliding behavior of the plate boundary fault. The pressure-temperature paths for subducting material control the distributions of dehydration reactions, a primary control on the pore fluid pressure distribution. Thus, constraining subduction zone temperatures are required to understand the seismic processes along the plate interface. We present thermal models for three margin-perpendicular transects in the Mexican subduction zone. We examine the potential thermal effects of vigorous fluid Circulation in a high-permeability aquifer within the basaltic basement of the oceanic crust and compare the results with models that invoke extremely high pore fluid pressures to reduce frictional heating along the megathrust. We combine thermal model results with petrological models to determine the spatial distribution of fluid release from the subducting slab and compare dewatering locations with the locations of seismicity, nonvolcanic tremor, slow-slip events, and low-frequency earthquakes. Simulations including Hydrothermal Circulation are most consistent with surface heat flux measurements. Hydrothermal Circulation has a maximum cooling effect of 180°C. Hydrothermally cooled crust carries water deeper into the subduction zone; fluid release distributions in these models are most consistent with existing geophysical data. Our models predict focused fluid release, which could generate overpressures, coincident with an observed ultraslow layer (USL) and a region of nonvolcanic tremor. Landward of USLs, a downdip decrease in fluid source magnitude could result in the dissipation in overpressure in the oceanic crust without requiring a downdip increase in fault zone permeability, as posited in previous studies.

  • Long-distance fluid and heat transport in the oceanic crust entering the Nankai subduction zone, NanTroSEIZE transect
    Earth and Planetary Science Letters, 2014
    Co-Authors: Glenn A Spinelli
    Abstract:

    Abstract I examine the potential causes of anomalous seafloor heat flux on the oceanic plate in the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) transect offshore southern Japan. The most prominent anomaly is a ∼ 50 mW m − 2 change in heat flux between Integrated Ocean Drilling Program Sites C0011 and C0012 over a distance of 30 km wide transition at the seafloor. The observed surface heat flux pattern is indicative of Hydrothermal Circulation in the basement aquifer and advection of heat from the subducted crust into the aquifer on the incoming plate. For a 600 m thick aquifer, the permeability is likely ⩾ 7 × 10 − 11 m 2 , and Hydrothermal Circulation transports at least 300 times more heat than conduction alone. The heat flux from the subduction zone seaward to the incoming plate is consistent with Hydrothermal Circulation in the subducting crust persisting to ∼100 km landward of the deformation front. Vigorous fluid Circulation in the basaltic basement is consistent with both the seafloor thermal anomalies and geochemical anomalies near the sediment–basement interface.

  • thermal effects of Hydrothermal Circulation and seamount subduction temperatures in the nankai trough seismogenic zone experiment transect japan
    Geochemistry Geophysics Geosystems, 2011
    Co-Authors: Glenn A Spinelli, Robert N Harris
    Abstract:

    [1] We examine the thermal effects of seamount subduction. Seamount subduction may cause transient changes in oceanic crust hydrogeology and plate boundary fault position. Prior to subduction, seamounts provide high-permeability pathways between the basaltic crustal aquifer and overlying ocean that can focus fluid flow and efficiently cool the oceanic crust. As the seamount is subducted, the high-permeability pathway is closed, shutting down the advective transfer of heat. If significant fluid flow occurs, it would be restricted after seamount subduction and would result in a redistribution of heat warming the trench and cooling landward parts of the system. Additionally, subducting seamounts can influence the position of the plate boundary fault that has thermal consequences by locally controlling the proportions of incoming sediment that subduct and accrete. Shifting the decollement to the seafloor at the trench in the wake of seamount subduction causes limited cooling focused at the toe of the margin wedge. We apply these features of seamount subduction to a thermal model for the Nankai Trough Seismogenic Zone Experiment transect on the margin of Japan. Models with Hydrothermal Circulation provide an explanation for anomalously high surface heat flux observations near the trench. They yield temperatures of ∼100°C−295°C for the rupture area of the 1944 Tonankai earthquake. Temperatures in the region of episodic tremor and slip are estimated at ∼290°C–325°C, ∼70°C cooler than a model with no fluid Circulation.

  • Effects of fluid Circulation in subducting crust on Nankai margin seismogenic zone temperatures
    Geology, 2008
    Co-Authors: Glenn A Spinelli, Kelin Wang
    Abstract:

    Vigorous fl uid Circulation maintained in newly subducted ocean crust signifi cantly affects subduction zone temperatures on the Nankai margin, Japan. The shallow part of the igneous ocean crust is pervasively fractured and thus highly permeable, allowing vigorous hydro thermal Circulation. This Circulation has been recognized as an important control on the thermal budget and evolution of ocean crust worldwide. However, existing subduction zone thermal models either do not include Hydrothermal Circulation in ocean crust or assume that it abruptly stops upon subduction. Here we use a conductive proxy to incorporate the thermal effects of high Nusselt number fl uid Circulation in subducting crust into a subduction zone thermal model. Hydrothermal Circulation reduces temperatures in the seismogenic zone of the Nankai margin plate boundary fault by ~20 °C at the updip limit of seismicity and ~100 °C at the downdip limit. With improved thermal models for subduction zones that include the effects of Hydrothermal Circulation in subducting crust, estimates of metamorphic reaction progress and interpretations of fault zone processes on various margins may need to be revisited.

  • Hydrothermal Circulation in subducting crust reduces subduction zone temperatures
    Geology, 2008
    Co-Authors: Troy Kummer, Glenn A Spinelli
    Abstract:

    Most thermal models of subduction zones assume no advection of heat by fluid flow because slow flow through underthrusting sediment, the decollement, and wedge likely transports only a minor amount of heat. We model coupled fluid and heat transport in a subduction zone and show that Hydrothermal Circulation in subducting basaltic basement rocks can have a great influence on subduction zone temperatures. Fractured basaltic basement has permeability several orders of magnitude higher than a typical decollement, allowing fluid Circulation to redistribute and extract heat from a subduction zone. We simulate systems with upper basaltic basement permeability ranging from 10−13 to 10−10 m2. In addition, we incorporate the effect of permeability reduction within the basaltic basement as it is subducted. The models with fluid transport show suppressed temperatures along the subducting slab relative to models with no fluid transport. With continuous sediment cover, heat is extracted from under the margin wedge to the trench. In models where faulted ocean crust exposes high-permeability basement to the ocean floor, cooling from ocean bottom water results in highly suppressed heat flow relative to conductive models. Hydrothermally cooled ocean crust also acts to slow thermally controlled diagenetic reaction progress within subducting sediment.

Fabrice J Fontaine - One of the best experts on this subject based on the ideXlab platform.

  • heat flow morphology pore fluids and Hydrothermal Circulation in a typical mid atlantic ridge flank near oceanographer fracture zone
    Earth and Planetary Science Letters, 2018
    Co-Authors: Le V Gal, Francis Lucazeau, Mathilde Cannat, Jeffrey Poort, C Monnin, Anne Battani, Fabrice J Fontaine, Bruno Goutorbe, Frederique Rolandone
    Abstract:

    Hydrothermal Circulation affects heat and mass transfers in the oceanic lithosphere, not only at the ridge axis but also on their flanks, where the magnitude of this process has been related to sediment blanket and seamounts density. This was documented in several areas of the Pacific Ocean by heat flow measurements and pore water analysis. However, as the morphology of Atlantic and Indian ridge flanks is generally rougher than in the Pacific, these regions of slow and ultra-slow accretion may be affected by Hydrothermal processes of different regimes. We carried out a survey of two regions on the eastern and western flanks of the Mid-Atlantic Ridge between Oceanographer and Hayes fracture zones. Two hundred and eight new heat flow measurements were obtained along six seismic profiles, on 5 to 14 Ma old seafloor. Thirty sediment cores (from which porewaters have been extracted) have been collected with a Kullenberg corer equipped with thermistors thus allowing simultaneous heat flow measurement. Most heat flow values are lower than those predicted by purely conductive cooling models, with some local variations and exceptions: heat flow values on the eastern flank of the study area are more variable than on the western flank, where they tend to increase westward as the sedimentary cover in the basins becomes thicker and more continuous. Heat flow is also higher, on average, on the northern sides of both the western and eastern field regions and includes values close to conductive predictions near the Oceanographer Fracture Zone. All the sediment porewaters have a chemical composition similar to that of bottom seawater (no anomaly linked to fluid Circulation has been detected). Heat flow values and pore fluid compositions are consistent with fluid Circulation in volcanic rocks below the sediment. The short distances between seamounts and short fluid pathways explain that fluids flowing in the basaltic aquifer below the sediment have remained cool and unaltered. Finally, relief at small-scale is calculated using variogram of bathymetry and compared for different regions affected by Hydrothermal Circulation.

  • Hydrothermal Circulation at slow-spreading mid-ocean ridges: The role of along-axis variations in axial lithospheric thickness
    Geology, 2008
    Co-Authors: Fabrice J Fontaine, Mathilde Cannat, Javier Escartín
    Abstract:

    At several ridge segments along the slow-spreading Mid-Atlantic Ridge, the lithosphere appears to be cooled by centrally located, isolated Hydrothermal fields, hundreds of meters wide, extracting as much as 1000 MW from the lithosphere and hosting very large (>106 m3) sulfide edifices. These fields are possibly fueled by subseafloor Hydrothermal cells cooling and leaching the lithosphere up to a few tens of kilometers along axis. However, the detailed mechanisms by which such Hydrothermal heat extraction takes place are not well constrained. It is postulated that melt focusing and preferred cooling near transforms result in a thinner lithosphere at the center of slow-spreading ridge segments. In this configuration, and with a depth of penetration controlled by brittle lithospheric thickness, the base of the Hydrothermal system is not at constant depth. Here we present models of along-axis Hydrothermal Circulation showing that pressure gradients generated along this basal slope influence flow dynamics. We show that the size of Hydrothermal cells increases with the basal slope α. For α 15°–20°, the Circulation reaches steady state and is composed of a single cell with a broad recharge and a focused discharge. Although our models make several simplifying assumptions, we propose that along-axis variations in lithosphere thickness associated with the magmatic and tectonic segmentation of slow-spreading ridges should favor the formation of large and centrally located vent fields, mining heat on several kilometers along axis. We also predict that more short-lived and weaker vent fields may develop away from the segment center.

  • Two‐dimensional numerical models of open‐top Hydrothermal convection at high Rayleigh and Nusselt numbers: Implications for mid‐ocean ridge Hydrothermal Circulation
    Geochemistry Geophysics Geosystems, 2007
    Co-Authors: Fabrice J Fontaine, William S. D. Wilcock
    Abstract:

    Mid-ocean ridges host vigorous Hydrothermal systems that remove large quantities of heat from the oceanic crust. Inferred Nusselt numbers (Nu), which are the ratios of the total heat flux to the heat flux that would be transported by conduction alone, range from 8 to several hundred. Such vigorous convection is not fully described by most numerical models of Hydrothermal Circulation. A major difficulty arises at high Nu from the numerical solution of the temperature equation. To avoid classical numerical artifacts such as nonphysical oscillatory behavior and artificial diffusion, we implement the Multidimensional Positive Definite Advection Transport Algorithm (MPDATA) technique, which solves the temperature equation using an iterated upwind corrected scheme. We first validate the method by comparing results for models with uniform fluid properties in closed- and open-top systems to existing solutions with Nu ≤ ∼20. We then incorporate realistic fluid properties and run models for Nu up to 50–60. Solutions are characterized by an unstable bottom thermal boundary layer where thermal instabilities arise locally. The pattern of heat extraction is periodic to chaotic. At any Nu > ∼13 the venting temperatures in a given plume are chaotic and oscillate from ∼350° to 450°C. Individual plumes can temporarily stop short of the surface for intervals ranging from tens to hundreds of years at times when other plumes vent with an increased flow rate. The solutions also display significant reCirculation, and as a result large areas of downflow are relatively warm with temperatures commonly exceeding 150°C at middepths. Our results have important implications for mid-ocean ridge Hydrothermal systems and suggest the following: (1) The reaction zones of mid-ocean ridge Hydrothermal systems are enlarged by thermal instabilities that migrate laterally toward upflow zones. This will substantially increase the volume of rock involved in chemical reactions compared to steady state configurations. (2) Hydrothermal discharge can stop temporarily as zones of venting are dynamically replaced by zones of seawater recharge. (3) Anhydrite precipitation occurring at temperatures exceeding ∼150°C will likely occur throughout a large portion of recharge zone and will not necessarily clog downflow pathways as efficiently as has been recently inferred.

  • two dimensional numerical models of open top Hydrothermal convection at high rayleigh and nusselt numbers implications for mid ocean ridge Hydrothermal Circulation
    Geochemistry Geophysics Geosystems, 2007
    Co-Authors: Fabrice J Fontaine, William S. D. Wilcock
    Abstract:

    Mid-ocean ridges host vigorous Hydrothermal systems that remove large quantities of heat from the oceanic crust. Inferred Nusselt numbers (Nu), which are the ratios of the total heat flux to the heat flux that would be transported by conduction alone, range from 8 to several hundred. Such vigorous convection is not fully described by most numerical models of Hydrothermal Circulation. A major difficulty arises at high Nu from the numerical solution of the temperature equation. To avoid classical numerical artifacts such as nonphysical oscillatory behavior and artificial diffusion, we implement the Multidimensional Positive Definite Advection Transport Algorithm (MPDATA) technique, which solves the temperature equation using an iterated upwind corrected scheme. We first validate the method by comparing results for models with uniform fluid properties in closed- and open-top systems to existing solutions with Nu ≤ ∼20. We then incorporate realistic fluid properties and run models for Nu up to 50–60. Solutions are characterized by an unstable bottom thermal boundary layer where thermal instabilities arise locally. The pattern of heat extraction is periodic to chaotic. At any Nu > ∼13 the venting temperatures in a given plume are chaotic and oscillate from ∼350° to 450°C. Individual plumes can temporarily stop short of the surface for intervals ranging from tens to hundreds of years at times when other plumes vent with an increased flow rate. The solutions also display significant reCirculation, and as a result large areas of downflow are relatively warm with temperatures commonly exceeding 150°C at middepths. Our results have important implications for mid-ocean ridge Hydrothermal systems and suggest the following: (1) The reaction zones of mid-ocean ridge Hydrothermal systems are enlarged by thermal instabilities that migrate laterally toward upflow zones. This will substantially increase the volume of rock involved in chemical reactions compared to steady state configurations. (2) Hydrothermal discharge can stop temporarily as zones of venting are dynamically replaced by zones of seawater recharge. (3) Anhydrite precipitation occurring at temperatures exceeding ∼150°C will likely occur throughout a large portion of recharge zone and will not necessarily clog downflow pathways as efficiently as has been recently inferred.

  • permeability changes due to mineral diagenesis in fractured crust implications for Hydrothermal Circulation at mid ocean ridges
    Earth and Planetary Science Letters, 2001
    Co-Authors: Fabrice J Fontaine, Michel Rabinowicz, Jacques Boulegue
    Abstract:

    Abstract The Hydrothermal processes at ridge crests have been extensively studied during the last two decades. Nevertheless, the reasons why Hydrothermal fields are only occasionally found along some ridge segments remain a matter of debate. In the present study we relate this observation to the mineral precipitation induced by Hydrothermal Circulation. Our study is based on numerical models of convection inside a porous slot 1.5 km high, 2.25 km long and 120 m wide, where seawater is free to enter and exit at its top while the bottom is held at a constant temperature of 420°C. Since the fluid Circulation is slow and the fissures in which seawater circulates are narrow, the reactions between seawater and the crust achieve local equilibrium. The rate of mineral precipitation or dissolution is proportional to the total derivative of the temperature with respect to time. Precipitation of minerals reduces the width of the fissures and thus percolation. Using conventional permeability versus porosity laws, we evaluate the evolution of the permeability field during the Hydrothermal Circulation. Our computations begin with a uniform permeability and a conductive thermal profile. After imposing a small random perturbation on the initial thermal field, the Circulation adopts a finger-like structure, typical of convection in vertical porous slots thermally influenced by surrounding walls. Due to the strong temperature dependence of the fluid viscosity and thermal expansion, the hot rising fingers are strongly buoyant and collide with the top cold stagnant water layer. At the interface of the cold and hot layers, a horizontal boundary layer develops causing massive precipitation. This precipitation front produces a barrier to the Hydrothermal flow. Consequently, the flow becomes layered on both sides of the front. The fluid temperature at the top of the layer remains quite low: it never exceeds a temperature of 80°C, well below the exit temperature of hot vent sites observed at black or white ‘smokers’. We show that the development of this front is independent of the Rayleigh number of the Hydrothermal flow, indicating that the mineral precipitation causes cold, diffusive vents. Finally, we present a model suggesting that the development of smokers is possible when successive tectonic/volcanic events produce a network of new permeable fissures that can overcome the permeability decrease caused by mineral precipitation. Such a model is consistent with recent seismic data showing Hydrothermal vents located at seismologically active ridge segments.

D. Hasterok - One of the best experts on this subject based on the ideXlab platform.

  • global patterns and vigor of ventilated Hydrothermal Circulation through young seafloor
    Earth and Planetary Science Letters, 2013
    Co-Authors: D. Hasterok
    Abstract:

    Article history: Using an updated global heat flow dataset with >14000 oceanic measurements, we revise the estimated global power deficit due to ventilated Hydrothermal Circulation. This study differs from previous estimates by taking into account (1) non-Gaussian statistics, (2) an improved seafloor age model, (3) a new plate cooling model calibrated directly to heat flow, and (4) the effect of sediment cover on the heat flow deficit and ventilated cutoff age. We obtain the maximum heat flow deficit (difference between predicted and observed) when the data are separated by seafloor areas with <400 m and ! 400 m of sediment cover. The estimated power deficit (integrated heat flow deficit with respect to area) for areas of thin (<400 m) sediment cover is 7.8 TW and for areas of thick (! 400 m) is 0.2 TW. The total power deficit, 8.0 TW with 50% of estimates falling between 5.0 and 10.0 TW, represents a ! 30% reduction in magnitude compared with previous heat flow and fluid flow based estimates. Regions with thick, ! 400 m, sediment cover experience half the heat flow deficit for one-third of the duration (25 Ma) of regions with thin sediment cover (75 Ma). Based on this study, vigorous fluid exchange between the oceans and seafloor redistributes ! 30% of heat lost through young oceanic crust.

  • Global patterns and vigor of ventilated Hydrothermal Circulation through young seafloor
    Earth and Planetary Science Letters, 2013
    Co-Authors: D. Hasterok
    Abstract:

    Article history: Using an updated global heat flow dataset with >14000 oceanic measurements, we revise the estimated global power deficit due to ventilated Hydrothermal Circulation. This study differs from previous estimates by taking into account (1) non-Gaussian statistics, (2) an improved seafloor age model, (3) a new plate cooling model calibrated directly to heat flow, and (4) the effect of sediment cover on the heat flow deficit and ventilated cutoff age. We obtain the maximum heat flow deficit (difference between predicted and observed) when the data are separated by seafloor areas with

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