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  • 1
    Publication Date: 2019-01-27
    Type: Dataset
    Format: text/tab-separated-values, 109 data points
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  • 2
    Publication Date: 2019-01-28
    Type: Dataset
    Format: text/tab-separated-values, 38 data points
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  • 3
    Publication Date: 2015-10-06
    Description: Fifty-four new heat flow measurements in the central troughs of the Guaymas basin support the hypothesis that they are sites of active intrusion. In the northern trough a distinct pattern of hydrothermal cooling is revealed, with venting along the western boundary fault of the trough. In the southern trough an analogous pattern is apparently superimposed upon a conductive cooling anomaly associated with a recent central intrusion. The discharge of thermal waters occurs along the boundary faults and through other faults associated with a possible horst block located in the north central floor of the southern trough. The heat flow patterns suggest that the intrusions are episodic and do not occur simultaneously along the length (15–40 km) of a spreading segment. A review of all available heat flow measurements for the Guaymas basin suggests that most of the recharge for a pervasive regional hydrothermal system is limited to the central depressions, with perhaps some contribution from pore water. The discharge of thermal waters occurs predominantly in the central depressions and possibly along the boundary transform faults and fracture zones. The regions of the basin more than a few kilometers in distance from the spreading axis, although presumably underlain by a hydrothermal system, are probably not the location of numerous vents or recharge zones.
    Type: Article , PeerReviewed
    Format: text
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  • 4
    Publication Date: 2017-01-04
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 7 (2006): Q07011, doi:10.1029/2005GC001178.
    Description: We report 157 closely spaced heat flow measurements along the Lucky Strike segment in the Mid-Atlantic Ridge (MAR) for ages of the ocean floor between 0 and 11 Ma. On the eastern flank of a volcanic plateau delimiting off-axis and axial domains, the magnitude of heat flow either conforms to the predictions of conductive lithospheric cooling models or is affected by localized anomalies. On the western flank it is uniformly lower than conductive model predictions. We interpret the observed patterns of heat flow by lateral fluid circulation in a highly permeable oceanic basement. The circulation geometries are probably 3-D rather than 2-D and are determined by the configuration of the basement/sediment interface and the distribution of effectively unsedimented seamounts where water recharge can occur. Two major hydrothermal circulation systems can possibly explain the observations off-axis: the first would involve lateral pore water flow from west to east, and the second would have a reverse flow direction. The wavelengths and magnitudes of heat flow anomalies require Darcy velocities of the order of 1–4 m/year, which are similar to those proposed for fast-accreted crust elsewhere. However, a large proportion of this MAR domain remains unaffected by hydrothermal cooling, which is a relatively unusual observation but confirms the validity of conductive thermal models for seafloor ages between 5 and 10 Ma. Closer to the ridge axis (<5 Myr old crust), water circulation affects the overall axial domain, as larger proportions of basement are exposed. As much as 80–90% of the heat flux from the axial domain may be transferred to the Lucky Strike vent field, in agreement with the estimated discharge.
    Keywords: Heat flow ; Mid-Atlantic Ridge
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: 9995846 bytes
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  • 5
    Publication Date: 2017-01-04
    Description: Author Posting. © American Geophysical Union, 2003. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 108, B9 (2003): 2434, doi:10.1029/2001JB000703.
    Description: From August 1994 to March 1995, three 50-m-high vertical thermistor arrays designated “Giant Kelps” (GKs) were deployed around the central black smoker complex (CBC) at the TAG hydrothermal mound, Mid-Atlantic Ridge (26°08primeN, 44°49primeW). These were designed to monitor the temporal variability of the vertical temperature distribution in the hydrothermal plume. One small high-temperature probe “Hobo” was also deployed in one of the black smoker vents of CBC. Over the observation period, two typical characteristics are recognized in plume temperatures measured with GKs: (1) the amplitudes of temperature anomalies decrease with increasing height above the top of CBC; (2) maximum temperature anomalies on the upper thermistors occurred periodically and nearly simultaneously across the array about every 6 hours. Conversely, maximum temperature anomalies on the lower thermistors occurred periodically every 12 hours, indicating that the location of the plume discharged from CBC was forcibly moved by the change in direction of tidally modulated current flow. The heat flux from CBC was estimated from temperatures measured by GKs based on a model of buoyant hydrothermal fluid rising in a stable, stratified density environment. The estimated heat flux from CBC gradually decreases from about 86 to 55 MW over the ~7 months of measurement, with a mean rate of decrease of 0.17 MW d-1. Since the black smoker effluent temperature measured with Hobo was almost stable over the measurement period, a plausible cause of the decrease is a reduction in the volume of hydrothermal fluid provided to the CBC (in which case the estimated mean rate of decrease in volume flux of CBC is 8.9 m3 d-1). Estimated heat flux, temperature anomalies observed by Hobo, and diffuse flow and subbottom temperature anomalies recorded by other long-term monitoring instruments before, during, and after ODP Leg 158 indicate that the drilling probably affected the fluid flow pattern within the mound but had little effect on the total heat flux from CBC.
    Description: This study was supported by the Ridge Flux project of the Science and Technology Agency, Japan, the US NSF, and the UK NERC BRIDGE program. GK instrumentation development and deployments were supported in large part by NSF grant OCE-9324542.
    Keywords: Heat flux ; Hydrothermal plume ; TAG hydrothermal mound
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
    Publication Date: 2017-06-06
    Description: The outrigged thermal probes of a "pogo" marine geothermal probe have been adapted to measure thermal conductivity in-situ by the continuous-heating line source technique. The instrumental uncertainty in applying the analytical theory to a single-probe and double-probe configuration is found to be 3 and 6 percent, respectively. The in-situ outrigged single probe <.32 cm dia.) is essentially a scaled-up version of the needle probe (.08 cm dia.). The main advantage of the outrigged probe over a larger radius probe <e.g., violin-bow probe) is that for short-time temperatures (<2 min.), simple approximations to the exact solution for a perfectly conducting cylindrical probe are achieved. The continuous-heating compares favorably with the pulse-heating technique, the latter being more energy efficient. The continuous-heating method applied to the thin outrigged probe allows for accurate equilibrium in-situ temperature and thermal conductivity estimates in less than 15 minutes of recording time. The technique has been applied to several hundred marine heat flow stations. Comparison of in-situ measurements to needle probe measurements made on nearby piston cores indicate agreement to within 5%. The conductivity profiles of the in-situ data and core data show that the piston coring process frequently does not retrieve the upper meter of surficial sediment.
    Description: Support was provided by the U. S. National Science Foundation under grant Nos. OCE-8025181, OCE-8117886, and OCE-8409170.
    Keywords: Ocean temperature ; Terrestrial heat flow
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 7
    Publication Date: 2017-01-05
    Description: Heat flow estimates at two sites on the U.S. Atlantic continental margin are presented. An estimate of the heat flowing from the basement also has been obtained. About 4.8 km of sediments penetrated at the COST B-2 and 4.0 km at the COST B-3 were deposited since the Upper Jurassic. Well logs were used to evaluate thermal gradients and sedimentation rates, whereas thermal conductivities and radiogenic heat productions were measured on drill cuttings samples. A procedure to estimate in-situ thermal conductivity from drill cuttings and well logs is described. A substantial set of samples, in the form of drill cuttings, were sorted in four major lithologies: sandstones, siltstones, shales and limestones. Laboratory measurements of density, porosity, thermal conductivity, quartz (%), potassium (%), uranium (ppm) and thorium (ppm) were performed on 128 reorganized and pulverized samples. A significant correlation of the matrix thermal conductivity to quartz and potassium content was found. In situ porosity and volume fraction of each lithology, determined mainly from well logs, were used to calculate in situ mean thermal conductivity. Finally the mean in situ vertical component of the thermal conductivity, as required for heat flow values, has been estimated from a correction factor for the anisotropy of each lithology. The in-situ temperature and anisotropy effects substantially decrease estimates of thermal conductivity at depth. Below the uppermost 1 km in both wells the best estimate of the thermal gradient is 26.3°C km- 1 at COST B-2 and 26.1°C km- 1 at COST B-3, whereas in situ mean thermal conductivities range between about 1.8 and 1.9 W m- 1 K- 1 (4.3-4.5 T.C.U.). The average heat flow is estimated as about 45 mwm- 2 (1.07 H.F.U.) at COST B-2 and 44 mWm- 2 (1.06 H.F.U.) at COST B-3, with an uncertainty of about 20-25%. The mean radiogenic production in sediments at the two sites has been estimated as 1.83 (COST B-2) and 1.44 (COST B-3) 10- 6Wm- 3 • With a 12-14 km thick sedimentary sequence a radioactive contribution of 20-25 mWm- 2 can be expected. The effects of sediment deposition, compaction, pore water advection and radiogenic heat production have been combined in a numerical model (Hutchison, 1985) to estimate the undisturbed basement heat flux. Although the sedimentation depresses the basement heat flux by 15-20%, this effect is more than compensated by radioactive heat production in the sediments, so that the surface flux is estimated to be higher than that from the basement. The latter is calculated at about 33-39 mwm- 2 (0.8-0.9 H.F.U.), a relatively low value. The overall uncertainity is about ± 20-25%, and other estimates on continental margins with thick sediments (e.g. Reiter and Jessop, 1985) probably have at least a similar uncertainty.
    Keywords: Earth temperature ; Sedimentation and deposition
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 8
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    Woods Hole Oceanographic Institution
    Publication Date: 2017-01-04
    Description: A miniature temperature recorder has been developed to be used with the hydraulic piston sediment corer <HPC) on the Deep Sea Drilling Project <DSDP). The instrumentation fits into pressure-sealed slots in the wall of the HPC, allowing temperature measurements to be made simultaneously with coring operations. Temperatures from -2 to 70°C are measured to a resolution of about 0.01°C. Up to 1300 13-bit measurements are recorded in random access memory (RAM), at a sampling rate ranging between 0.1 s to over 100 min., as specified by the operator in a program loaded into a microprocessor of the instrument. During recording the instrumentation uses about 3.5 mamp at 7.5 volts, which can be supplied for about 20 hours of operation by a custom-made pack of silver-oxide batteries. The corer is normally left motionless in the sediment for about 10 min. to allow extrapolation of the measured temperatures to equilibrium in-situ temperature. Examples of data from DSDP Leg 86 are given.
    Description: Funding was provided by the National Science Foundation under grant Nos. OCE 82-14658 and OCE 83-00073. Additional support was provided by U.S. Geological Survey of Woods Hole to begin development of instrumentation; and to the Ocean Industry Program of the Woods Hole Oceanographic Institution to complete the development.
    Keywords: Ocean temperature ; Oceanographic instruments ; Temperature measurements
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 9
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    Woods Hole Oceanographic Institution
    Publication Date: 2018-02-16
    Description: The reproducibility of thermal conductivity measurements on fused silica glass by various investigators using different techniques suggests its suitability as a standard for such measurements. Our laboratory measurements with the needle probe technique on chip samples of silica glass saturated with water gave a value of 3.287 ± 0.154 (S.D.) mcal/cm s °C (n = 21) at 25 °C, which is within about 1% of the previously determined values and the value given by the manufacturer for this material. The good agreement indicates that the flat-plate steady-state and needle probe transient methods give the same value for this material, and that the water-saturated chip technique is an accurate method to measure thermal conductivity of isotropic samples.
    Description: Supported by the National Science Foundation under Grant OCE 79-0944 8.
    Keywords: Thermal analysis ; Silica
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 10
    Publication Date: 2017-01-05
    Description: Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 6 (2005): Q11001, doi:10.1029/2005GC001013.
    Description: Heat flow measurements colocated with seismic data across 106 Ma seafloor of the Madeira Abyssal Plain (MAP) reveal variations in seafloor heat flow of ±10–20% that are positively correlated with basement relief buried below thick sediments. Conductive finite element models of sediments and upper basement using reasonable thermal properties are capable of generating the observed positive correlation between basement relief and seafloor heat flow, but with variability of just ±4–8%. Conductive simulations using a high Nusselt number (Nu) proxy for vigorous local convection suggest that Nu = 2–10 within the upper 600–100 m of basement, respectively, is sufficient to achieve a reasonable match to observations. These Nu values are much lower than those inferred on younger ridge flanks where greater thermal homogeneity is achieved in upper basement. Fully coupled simulations suggest that permeability below the MAP is on the order of 10−12–10−10 m2 within the upper 300–600 m of basement. This permeability range is broadly consistent with values determined by single-hole experiments and from modeling studies at other (mostly younger) sites. We infer that the reduction in basement permeability with age that is thought to occur within younger seafloor may slow considerably within older seafloor, helping hydrothermal convection to continue as plates age.
    Description: Funding in support of this work was provided by the U.S. National Science Foundation (OCE-0001892), the U.S. Science Support Program for IODP (T301A7), and the Institute for Geophysics and Planetary Physics/Los Alamos National Laboratory (1317).
    Keywords: Crustal evolution ; Hydrothermal processes ; Numerical modeling
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: 1294823 bytes
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