Multiple scales of hydrothermal circulation in Middle Valley, northern Juan de Fuca Ridge: Physical constraints and geologic models

Stein, Joshua S.; Fisher, A. T.

doi:10.1029/2000jb900395

Cited by 50 publications

(62 citation statements)

References 42 publications

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“…The layer is located at 30 meters below the seafloor (mbsf) at the Dead Dog field, and at approximately 150 mbsf at the ODP Mound field (SHIPBOARD SCIENTIFIC PARTY, 1992PARTY, , 1998aSTEIN and FISHER, 2001;STEIN et al, 1998). Recharge of vent fluids is thought to occur as flow along the normal faults and linear unsedimented basement ridges that border Middle Valley ( STEIN and FISHER, 2001), rather than as diffusive flow through the sediments (RABINOWICZ et al, 1998). The Dead Dog field is located over a buried basement edifice at 258 mbsf (SHIPBOARD SCIENTIFIC PARTY, 1992) that focuses fluid flow from the deep basement (DAVIS and FISHER, 1994;GOLDEN et al, 2003).…”

Section: Geologic Settingmentioning

confidence: 99%

Geochemistry of low-molecular weight hydrocarbons in hydrothermal fluids from Middle Valley, northern Juan de Fuca Ridge

Cruse

Seewald

2006

Geochimica et Cosmochimica Acta

108

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Hydrothermal vent fluids from Middle Valley, a sediment-covered mid-ocean ridge on the northern Juan de Fuca Ridge, were sampled in July, 2000. Eight different vents with exit temperatures of 186 to 281°C were sampled from two areas of venting: the Dead Dog and ODP Mound fields. Fluids from the Dead Dog field are characterized by higher concentrations of ΣNH 3 and organic compounds (C 1 -C 4 alkanes, ethene, propene, benzene and toluene) compared with fluids from the ODP Mound field. The ODP Mound fluids, however, are characterized by higher C 1 /(C 2 +C 3 ) and benzene:toluene ratios than those from the Dead Dog field. The aqueous organic compounds in these fluids have been derived from both bacterial processes (methanogenesis in low-temperature regions during recharge) as well as from thermogenic processes in higher-temperature portions of the subsurface reaction zone. As the sediments undergo hydrothermal alteration, carbon dioxide and hydrocarbons are released to solution as organic matter degrades via a stepwise oxidation process. Compositional and isotopic differences in the aqueous hydrocarbons indicate that maximum subsurface temperatures at the ODP Mound are greater than those at the Dead Dog field. Maximum subsurface temperatures were calculated assuming that thermodynamic equilibrium is attained between alkenes and alkanes, benzene and toluene, and carbon dioxide and methane. The calculated temperatures for alkene-alkane equilibrium are consistent with differences in the dissolved Cl concentrations in fluids from the two fields, and indicate that subsurface temperatures at the ODP Mound are hotter than those at the Dead Dog field. Temperatures calculated assuming benzene-toluene equilibrium and carbon dioxide-methane equilibrium are similar to observed exit temperatures, and do not record the hottest subsurface conditions. The difference in subsurface temperatures estimated using organic geochemical thermometers reflects subsurface cooling processes via mixing of a hot, low-salinity vapor with a cooler, seawater salinity fluid. Because of the disparate temperature dependence of alkene-alkane and benzene-toluene equilibria, the mixed fluid records both the high and low temperature equilibrium conditions. These calculations indicate that vapor-rich fluids are presently being formed in the crust beneath the ODP Mound, yet do not reach the surface due to mixing with the lower-temperature fluids.2

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Section: Geologic Settingmentioning

confidence: 99%

Geochemistry of low-molecular weight hydrocarbons in hydrothermal fluids from Middle Valley, northern Juan de Fuca Ridge

Cruse

Seewald

2006

Geochimica et Cosmochimica Acta

108

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“…Stein and Fisher (2001) describe the general processing scheme in detail, including estimation of uncertainties, which was implemented after the RetroFlux expedition using a graphically driven program that allowed viewing and editing of individual thermistor records. Interactive thermistor-by-thermistor processing was essential because many measurements included data that did not follow the standard pattern of heating and cooling after probe penetration.…”

Section: Processing and Uncertaintiesmentioning

confidence: 99%

Site surveys related to IODP Expedition 301: ImageFlux (SO149) and RetroFlux (TN116) expeditions and earlier studies

Zuehlsdorff¹,

Hutnak²,

Fisher³

et al. 2005

Proceedings of the IODP

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Integrated Ocean Drilling Program Expedition 301 was preceded during 2000 and 2002 by three surveys that helped to delineate seafloor and basement relief, sediment thickness, and the nature of ridge-flank hydrothermal conditions and processes on the eastern flank of the Juan de Fuca Ridge. These surveys generated swath map, seismic, and thermal data used to select locations for primary and secondary drilling targets, building from several decades of earlier work. We show compilations and examples of data from several characteristic settings in and around the Expedition 301 work area and use these observations to evaluate sedimentation patterns and thermal conditions in basement. There remain important unanswered questions in this area concerning fluid circulation within the upper oceanic crust, the magnitude of lithospheric heat input, the quantitative significance of advective heat loss from the crust, and relations between basement relief, sedimentation, and sediment alteration. These questions may be resolved through collection of a modest amount of additional data focusing on a few critical locations.

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“…Seawater level concentrations of sulfate, chlorite, and magnesium in the pore water in the deeper layer suggest the process of recharging of seawater into the subsurface sediments. Near active fluid venting site, such as TBS vent, pressure gradients associated with venting is known to induce the seawater recharge and to produce secondary fluid circulation cell below the seafloor (Stein and Fisher 2001). Incorporating oxic seawater into the subsurface sediments may retain a low concentration of NH 4 + , which is usually found under anoxic condition.…”

Section: Discussionmentioning

confidence: 99%

Sediment–Pore Water System Associated with Native Sulfur Formation at Jade Hydrothermal Field in Okinawa Trough

Yokoyama

Takahashi

Miyoshi

et al. 2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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The subsurface sediment-pore water system in the Jade hydrothermal field was investigated along with pore water chemistry and X-ray absorption fine structure analysis for sediment samples. Sediments were collected by coring near the TBS vent (Core 1186MBL) and from near the Biwako vent (Core 1188MB), which are active hydrothermal vents with high (320 C) and low (90 C) temperature fluids, respectively. Core 1186MBL is characterized by occurrences of chimney fragments in the shallow part (2-9 cmbsf) and native sulfur in the deep part (6-19 cmbsf). The results of chemical analyses of the pore water suggest a seawater recharge from the seafloor into Core 1186MBL. This hydraulic characteristic of the pore water, which is commonly observed near active submarine hydrothermal vents, leads to oxidation of sulfide minerals in chimney fragments in the shallow part by the oxic recharged seawater. The resulting acidic and suboxic pore water is transported downward, and can form native sulfur in the deeper part of Core 1186MBL. Core 1188MB shows a wide distribution of native sulfur, and its pore water chemistry indicates anaerobic oxidation of methane below 8 cmbsf and a mixing of seawater and hydrothermal fluid below 10 cmbsf. The mixing of acidic and anoxic hydrothermal fluid and seawater allows the precipitation of native sulfur in Core 1188MB, and the uniform circumneutral pH condition despite the input of acidic hydrothermal fluid. The native sulfur deposits in the arc-back-arc hydrothermal fields provide important geochemical information that is useful to understand the subsurface sediment-pore water system involving hydrothermal fluids Keywords

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Multiple scales of hydrothermal circulation in Middle Valley, northern Juan de Fuca Ridge: Physical constraints and geologic models

Cited by 50 publications

References 42 publications

Geochemistry of low-molecular weight hydrocarbons in hydrothermal fluids from Middle Valley, northern Juan de Fuca Ridge

Geochemistry of low-molecular weight hydrocarbons in hydrothermal fluids from Middle Valley, northern Juan de Fuca Ridge

Site surveys related to IODP Expedition 301: ImageFlux (SO149) and RetroFlux (TN116) expeditions and earlier studies

Sediment–Pore Water System Associated with Native Sulfur Formation at Jade Hydrothermal Field in Okinawa Trough

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