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Sample records for fuca ridge northeast

  1. Hydrothermal fluid effects on sediment column in Middle Valley, Juan de Fuca Ridge (northeast Pacific)

    SciTech Connect

    Al-Aasm, I.S.; Blaise, B.

    1987-05-01

    Core PAR 85-34, located near a high heat flow area in Middle Valley, northern Juan de Fuca Ridge, contains carbonate nodules of various sizes (less than or equal to 1-5 cm in length). Sedimentological, geochemical, and isotopic results allow us to understand the origin of these concretions and the effects of hydrothermal activity from nearby sulfide vents on the sediment column. The mineralogy of the olive-gray surface sediment (0-15 cm) is identical to unaffected hemipelagic sediments in the region except for a concentration of barite crystals (up to 1 cm) at the water-sediment interface. In the clay, mud fraction, and bulk sediment, the FeO, S, Ba, Cu, Ni, Pb, Zn and As are more enriched than in normal hemipelagic sediment in the area due to hydrothermal activity. Petrographic and SEM analysis of the nodules reveal iron calcite and barite minerals in cracks and on the outside part of the nodules with mineralogical and textural variations downcore. Stable isotope curves of these nodules appear to demonstrate the effects of both bacterial sulfate reduction and microbiological methane generation, with consequent extreme /sup 13/C-depletion in the precipitated carbonate. The curves also demonstrate that the hydrothermal fluid entering the system may have caused the negative shift in oxygen isotopes downcore, although this effect may have been of cyclic or episodic nature.

  2. Characteristics of hydrothermal plumes from two vent fields on the Juan de Fuca Ridge, northeast Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Baker, Edward T.; Massoth, Gary J.

    1987-09-01

    Deep CTD/transmissometer tows and water bottle sampling were used during 1985 to map the regional distribution of the neutrally-buoyant plumes emanating from each of two major vent fields on the Southern Symmetrical Segment (SSS) and Endeavour Segment (ES) of the Juan de Fuca Ridge. At both vent fields, emissions from point and diffuse hydrothermal sources coalesced into a single 200-m-thick plume elongated in the direction of current flow and with characteristic temperature anomalies of 0.02-0.05°C and light-attenuation anomalies of 0.01-0.08 m -1 (10-80 μg/l above background). Temperature anomalies in the core of each plume were uniform as far downcurrent as the plumes were mapped (10-15 km). Downcurrent light-attenuation trends were non-uniform and differed between plumes, apparently because different vent fluid chemistries at each field cause significant differences in the settling characteristics of the hydrothermal precipitates. Vent fluids from the SSS are metal-dominated and mostly precipitate very fine-grained hydrous Fe-oxides that remain suspended in the plume. Vent fluids from the ES are sulfur-dominated and precipitate a high proportion of coarser-grained Fe-sulfides that rapidly settle from the plume. The integrated flux of each vent field was estimated from measurements of the advective transport of each plume. Heat flux was 1700 ± 1100 MW from the ES and 580 ± 351 MW from the SSS. Particle flux varied from 546 ± 312 g/s to 204 ± 116 g/s at the ES depending on distance from the vent field, and was 92 ± 48 g/s from the SSS.

  3. Pb, Sr, and Nd isotopes in seamount basalts from the Juan de Fuca Ridge and Kodiak-Bowie seamount chain, northeast Pacific

    USGS Publications Warehouse

    Hegner, E.; Tatsumoto, M.

    1989-01-01

    Pb, Sr, and Nd isotopic ratios and their parent/daughter element concentrations for 28 basalts from 10 hotspot and nonhotspot seamounts are reported. Nd and Sr isotopic compositions (143Nd/144Nd = 0.51325-0.51304; 87Sr/86Sr = 0.70237-0.70275) plot in the envelope for Juan de Fuca-Gorda ridge basalts with tholeiitic basalts showing more depleted sources and a better negative correlation than transitional to alkalic basalts. Pb isotopic ratios in tholeiitic and alkalic basalts overlap (206Pb/204Pb = 18.29-19.44) and display a trend toward more radiogenic Pb in alkalic basalts. The isotopic data for hotspot and nonhotspot basalts are indistinguishable and correlate broadly with rock composition, implying that they are controlled by partial melting. The isotopic variation in the seamount basalts is about 60% (Nd-Sr) to 100% (Pb) of that in East Pacific Rise basalts and is interpreted as a lower limit for the magnitude of mantle heterogeneity in the northeast Pacific. The data indicate absence of a chemically distinct plume component in the linear seamount chains and strongly suggest an origin from mid-ocean ridge basalt-like east Pacific mantle. -Authors

  4. Post-eruption succession of macrofaunal communities at diffuse flow hydrothermal vents on Axial Volcano, Juan de Fuca Ridge, Northeast Pacific

    NASA Astrophysics Data System (ADS)

    Marcus, Jean; Tunnicliffe, Verena; Butterfield, David A.

    2009-09-01

    Hydrothermal vents harbor dense aggregations of invertebrate fauna supported by chemosynthesis. Severe tectonic events and volcanic eruptions frequently destroy vent communities and initiate primary succession at new vents on ridge-crest submarine lava flows. An eruption on Axial Volcano (˜1500 m depth), a seamount on the Juan de Fuca Ridge (JdFR) in the northeast Pacific Ocean, occurred in January 1998, which created new substratum and vents. This study examines the development of the macrofaunal vent assemblages associated with tubeworms ( Ridgeia piscesae) at eight diffuse flow vents over the following 3 years. Biological collections by suction of lava surfaces also characterized "pre-tubeworm assemblages". Coupled fluid sampling showed an overall decrease in temperature, sulphide, and sulphide-to-heat ratios over 3 years as well as large spatial variability across the new vents. We examined collections of pre-eruption diffuse flow vent assemblages at Axial Volcano to compare the stages of new community development to "mature" vents. Mature vent assemblages are characterized by two major community types dominated by limpets ( Lepetodrilus fucensis) and alvinellid polychaetes ( Paralvinella pandorae and/or P. palmiformis). The following post-eruption succession patterns emerged. First, R. piscesae tubeworms took up to 3 years to establish aggregations at the new vents, and the majority of pre-tubeworm assemblages were dominated by grazing polychaetes. Second, species colonized quickly and by 30 months after habitat creation >60% of Axial's species pool had arrived at the new vents; abundance at mature vents predicted colonization success with some notable exceptions. Third, shifts in species dominance occurred rapidly and by Year 3 new vent assemblages resembled mature, pre-eruption communities. In general, tubeworm assemblages were dominated by alvinellid polychaetes ( P. pandorae and P. palmiformis) in the first 2 years post-eruption, with limpets ( L

  5. Hydrothermal Vents of Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Stark, Joyce

    As a member of REVEL (Research and Education: Volcanoes, Exploration and Life), I had an opportunity to participant in a scientific research cruise focused on the active volcanoes along the Juan de Fuca Ridge, the submarine spreading center off the Washington- Oregon-Canada coast. REVEL was sponsored by the National Science Foundation, University of Washington, Pennsylvania State University and the American Museum of Natural History. We studied the geological, chemical and biological processes associated with active hydrothermal systems and my research focused on the biological communities of the sulfide structures. We worked on board the Woods Hole Oceanographic Institution Vessel, R/V Atlantis and the submersible ALVIN was used to sample the "Black Smokers". As a member of the scientific party, I participated in collection and sorting of biological specimens from the vent communities, attended lectures by scientists, contributed to the cruise log website, maintained a journal and developed my own research project. It was my responsibility to bring this cutting-edge research back to the classroom.

  6. Microbial Life in Ridge Flank Crustal Fluids at Baby Bare Seamount, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Huber, J. A.; Johnson, H. P.; Butterfield, D. A.; Baross, J. A.

    2005-12-01

    To determine the microbial community diversity within old oceanic crust, a novel sampling strategy was used to collect crustal fluids at Baby Bare Seamount, a 3.5 Ma old outcrop located in the northeast Pacific Ocean on the eastern flank of the Juan de Fuca Ridge. Stainless steel probes were driven directly into the igneous ocean crust to obtain samples of ridge flank crustal fluids. Genetic signatures and enrichment cultures of microorganisms demonstrate that these crustal fluids host a microbial community composed of species indigenous to the subseafloor, including anaerobic thermophiles, and species from other deep-sea habitats, such as seawater and sediments. Evidence using molecular techniques indicates the presence of a relatively small but active microbial population, dominated by bacteria. The microbial community diversity found in the crustal fluids may indicate habitat variability in old oceanic crust, with inputs of nutrients from seawater, sediment pore-water fluids and possibly hydrothermal sources. This report further supports the presence of an indigenous microbial community in ridge flank crustal fluids and advances our understanding of the potential physiological and phylogenetic diversity of this community.

  7. Water column hydrothermal plumes on the Juan de Fuca Ridge

    SciTech Connect

    Lupton, J.E. )

    1990-08-10

    Hydrographic surveys on the Juan de Fuca Ridge (JdFR) carried out from 1980 to 1987 show a complex pattern of {sup 3}He and Mn-rich water column plumes produced by venting from several submarine hot spring areas. In the vicinity of Axial Volcano at latitude 46{degree}N, distinct plumes were detected in 1980, 1982, and 1983 with {sup 3}He signatures up to {delta}({sup 3}He) = 64% at {approximately} 1,500 m depth at distances of {approximately} 10 km from the seamount summit. However, the same plumes had no detectable thermal signature, a paradox which is attributed to the high {sup 3}He/heat ratios and low salinities of the fluids venting within the caldera of Axial Volcano. Profiles directly over the seamount show hydrothermal {sup 3}He in the water column up to 300 m above the caldera floor, with the {sup 3}He signal increasing with depth to very high and uniform ratios of {delta}({sup 3}He) = 108-150% below the {approximately} 1,500-m caldera sill depth. Another apparent locus of hydrothermal input is Helium Basin, a depression on the northeast flank of Axial Volcano which had {delta}({sup 3}He) = 51% when first sampled in 1980. However, subsequent hydrocasts into Helium Basin in 1982 and 1983 yielded lower helium enrichments, suggesting either a decrease in hydrothermal input or flushing of the basin via a mixing event. To the south of Axial Volcano, high {delta}({sup 3}He) values of {approximately} 40% observed over the ridge axis at 45{degree}18{prime}N and 45{degree}39{prime}N indicate venting on this previously unexplored section of the ridge. The water column plumes over the US Geological Survey vent site at {approximately} 44{degree}40{prime}N on the southern JdFR have very high Mn/{sup 3}He ratios of 4,600 mol/cm{sup 3}, an apparently unique characteristic which can be used to distinguish these plumes from those originating at other JdFR vent fields.

  8. Sr isotopic variations along the Juan de Fuca Ridge.

    USGS Publications Warehouse

    Eaby, J.; Clague, D.A.; Delaney, J.R.

    1984-01-01

    The Sr isotopic ratios of 39 glass and microcrystalline basalt samples along the Juan de Fuca Ridge and one glass sample from Brown Bear Seamount are at the lower end of the range for normal MORB; the average 87Sr/86Sr ratio is 0.70249 + or - 0.00014 (2sigma ). Although subtle variations exist along the strike of the ridge, the Sr isotopic data do not show systematic variation relative to the proposed Cobb hotspot. The isotopic data are inconsistent with an enriched mantle-plume origin for the Cobb-Eikelberg Seamount chain.-W.H.B.

  9. Divergent Ridge Features on the Juan de Fuca and Gorda Ridges

    NASA Astrophysics Data System (ADS)

    Eaton, M. E.; Sautter, L.; Steele, M.

    2014-12-01

    Multibeam data collected using a Kongsberg EM122 sonar system on the NOAA ship R/V Marcus G. Langseth led by chief scientist Douglas Toomey (University of Oregon) in 2009 and with a Simrad EM302 sonar system on two NOAA ship Okeanos Explorer cruises led by chief scientists James Gardner (University of New Hampshire) and Catalina Martinez (University of Rhode Island) in 2009 show the morphology of the Juan de Fuca and Gorda Ridges, as well as the Blanco and Mendocino Fracture Zones. These ridges and fracture zones comprise the divergent plate boundary of the eastern edge of the Pacific Plate and the western edges of the Juan de Fuca and Gorda Plates. Both plates are being subducted beneath the western edge of the North American Plate. CARIS HIPS 8.1 software was used to process the multibeam data and create bathymetric images. The ridge axes, located off the coast of Washington and Oregon (USA) adjacent to the Cascadia Basin, indicate obvious signs of spreading, due to the series of faults and rocky ridges aligned parallel to the plate boundaries. Fault and ridge orientations are used to compare the direction of seafloor spreading, and indicate that both the Juan de Fuca Plate and Gorda Plate are spreading in a southeastern direction. Younger ridges from the Gorda Ridge system mapped in the study run parallel to the boundary, however older ridges do not show the same orientation, indicating a change in spreading direction. The presence of hydrothermal vents along the Juan de Fuca Ridge is also evidence of the active boundary, as the vent chimneys are composed of minerals and metals precipitated from the hot water heated by magma from beneath the spreading seafloor. In this study, the data are used to compare and contrast earthquake seismicity and ridge morphologies at a depth range of approximately 762 to 2134 meters. The diverging Pacific, Juan de Fuca, and Gorda Plates along with the San Andreas Fault have potential to increase seismic and volcanic activity around

  10. Acoustic detection of a seafloor spreading episode on the Juan de Fuca Ridge using military hydrophone arrays

    NASA Astrophysics Data System (ADS)

    Fox, Christopher G.; Radford, W. Eddie; Dziak, Robert P.; Lau, Tai-Kwan; Matsumoto, Haruyoshi; Schreiner, Anthony E.

    1995-01-01

    Until recently, no practical method has been available to continuously monitor seismicity of seafloor spreading centers. The availability of the U.S. Navy's SOund SUrveillance System (SOSUS) for environmental research has allowed the continuous monitoring of low-level seismicity of the Juan de Fuca Ridge in the northeast Pacific. On June 22, 1993, NOAA installed a prototype system at U.S Naval Facility Whidbey Island to allow real-time acoustic monitoring of the Juan de Fuca Ridge using SOSUS. On June 26, 2145 GMT, a burst of low-level seismic activity, with accompanying harmonic tremor, was observed and subsequently located near 46 deg 15 min N, 129 deg 53 min W, on the spreading axis of the Juan de Fuca Ridge. Over the following 2 days, the activity migrated to the NNE along the spreading axis with the final locus of activity near 46 deg 31.5 min N, 129 deg 35 min W. The nature of the seismicity was interpreted to represent a lateral dike injection with the possibility of eruption on the seafloor. Based on this interpretation, a response effort was initated by U.S. and Canadian research vessels, and both warm water plumes and fresh lavas were subsequently identified at the site.

  11. Microbial diversity in subseafloor fluids from Explorer Ridge, Northeast Pacific

    NASA Astrophysics Data System (ADS)

    Bolton, S.; Huber, J. A.; Embley, R.; Butterfield, D. A.; Baross, J. A.

    2003-12-01

    The Gorda, Juan de Fuca and Explorer Ridges are first order spreading centers located in the northeast Pacific. While the Gorda and Juan de Fuca Ridges have been extensively sampled for chemical and microbiological analyses, what little is known about the Explorer Ridge is from preliminary observations made in the mid-1980's. A cruise in 2002 revisited the area and discovered vigorous hydrothermal activity at Magic Mountain, a site located outside the primary rift valley. Explorer Ridge is an important site to compare with other well-described vent sites on the Juan de Fuca Ridge. Our research has focused on describing the phylogenetic and physiological diversity of bacteria and archaea in low temperature hydrothermal fluids in an effort to identify subseafloor indicator organisms and to use the physiological characteristics of these organisms to help constrain subseafloor habitat characteristics. We have previously established that there are microbial taxa that are unique to subseafloor habitats associated with diffuse flow fluids at Axial Seamount and at Endeavour both located on the Juan de Fuca Ridge. These included cultured anaerobic, thermophilic and hyperthermophilic heterotrophs, methanogens and sulfur metabolizers. Moreover, results from molecular phylogeny analyses using the 16S rRNA sequences identified a phylogenetically diverse group of bacteria belonging to the epsilon-proteobacteria. While anaerobic hyperthermophiles were cultured from some diffuse-flow vent sites at Explorer, they were less abundant than at Axial Volcano and Endeavour, and curiously, no methanogens were cultured or detected in 16S rRNA clonal libraries. Like Axial, a diverse group of epsilon-proteobacterial clones were found with many similar to those identified from Axial Seamount and other hydrothermal vent sites, although there appears to be some unique species. The overall bacterial diversity at Explorer appears different than at Axial, possibly linked to temperature or chemical

  12. Hydrothermal circulation within the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Johnson, H. Paul; Tivey, Maurice A.; Bjorklund, Tor A.; Salmi, Marie S.

    2010-05-01

    Areas of the seafloor at mid-ocean ridges where hydrothermal vents discharge are easily recognized by the dramatic biological, physical, and chemical processes that characterize such sites. Locations where seawater flows into the seafloor to recharge hydrothermal cells within the crustal reservoir are by contrast almost invisible but can be indirectly identified by a systematic grid of conductive heat flow measurements. An array of conductive heat flow stations in the Endeavour axial valley of the Juan de Fuca Ridge has identified recharge zones that appear to represent a nested system of fluid circulation paths. At the scale of an axial rift valley, conductive heat flow data indicate a general cross-valley fluid flow, where seawater enters the shallow subsurface crustal reservoir at the eastern wall of the Endeavour axial valley and undergoes a kilometer of horizontal transit beneath the valley floor, finally exiting as warm hydrothermal fluid discharge on the western valley bounding wall. Recharge zones also have been identified as located within an annular ring of very cold seafloor around the large Main Endeavour Hydrothermal Field, with seawater inflow occurring within faults that surround the fluid discharge sites. These conductive heat flow data are consistent with previous models where high-temperature fluid circulation cells beneath large hydrothermal vent fields may be composed of narrow vertical cylinders. Subsurface fluid circulation on the Endeavour Segment occurs at various crustal depths in three distinct modes: (1) general east to west flow across the entire valley floor, (2) in narrow cylinders that penetrate deeply to high-temperature heat sources, and (3) supplying low-temperature diffuse vents where seawater is entrained into the shallow uppermost crust by the adjacent high-temperature cylindrical systems. The systematic array of conductive heat flow measurements over the axial valley floor averaged ˜150 mW/m2, suggesting that only about 3% of

  13. Hydrothermal sulfide accumulation along the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Jamieson, J. W.; Clague, D. A.; Hannington, M. D.

    2014-06-01

    Hydrothermal sulfide deposits that form on the seafloor are often located by the detection of hydrothermal plumes in the water column, followed by exploration with deep-towed cameras, side-scan sonar imaging, and finally by visual surveys using remotely-operated vehicle or occupied submersible. Hydrothermal plume detection, however, is ineffective for finding hydrothermally-inactive sulfide deposits, which may represent a significant amount of the total sulfide accumulation on the seafloor, even in hydrothermally active settings. Here, we present results from recent high-resolution, autonomous underwater vehicle-based mapping of the hydrothermally-active Endeavour Segment of the Juan de Fuca Ridge, in the Northeast Pacific Ocean. Analysis of the ridge bathymetry resulted in the location of 581 individual sulfide deposits along 24 km of ridge length. Hydrothermal deposits were distinguished from volcanic and tectonic features based on the characteristics of their surface morphology, such as shape and slope angles. Volume calculations for each deposit results in a total volume of 372,500 m3 of hydrothermal sulfide-sulfate-silica material, for an equivalent mass of ∼1.2 Mt of hydrothermal material on the seafloor within the ridge's axial valley, assuming a density of 3.1 g/cm3. Much of this total volume is from previously undocumented inactive deposits outside the main active vent fields. Based on minimum ages of sulfide deposition, the deposits accumulated at a maximum rate of ∼400 t/yr, with a depositional efficiency (proportion of hydrothermal material that accumulates on the seafloor to the total amount hydrothermally mobilized and transported to the seafloor) of ∼5%. The calculated sulfide tonnage represents a four-fold increase over previous sulfide estimates for the Endeavour Segment that were based largely on accumulations from within the active fields. These results suggest that recent global seafloor sulfide resource estimates, which were based mostly

  14. Earthquake-induced changes in a hydrothermal system on the Juan de Fuca mid-ocean ridge

    PubMed

    Johnson; Hutnak; Dziak; Fox; Urcuyo; Cowen; Nabelek; Fisher

    2000-09-14

    Hydrothermal vents on mid-ocean ridges of the northeast Pacific Ocean are known to respond to seismic disturbances, with observed changes in vent temperature. But these disturbances resulted from submarine volcanic activity; until now, there have been no observations of the response of a vent system to non-magmatic, tectonic events. Here we report measurements of hydrothermal vent temperature from several vents on the Juan de Fuca ridge in June 1999, before, during and after an earthquake swarm of apparent tectonic origin. Vent fluid temperatures began to rise 4-11 days after the first earthquake. Following this initial increase, the vent temperatures oscillated for about a month before settling down to higher values. We also observed a tenfold increase in fluid output from the hydrothermal system over a period of at least 80 days, extending along the entire ridge segment. Such a large, segment-wide thermal response to relatively modest tectonic activity is surprising, and raises questions about the sources of excess heat and fluid, and the possible effect on vent biological communities. PMID:11001052

  15. Mantle flow geometry from ridge to trench beneath the Gorda-Juan de Fuca plate system

    NASA Astrophysics Data System (ADS)

    Martin-Short, Robert; Allen, Richard M.; Bastow, Ian D.; Totten, Eoghan; Richards, Mark A.

    2015-12-01

    Tectonic plates are underlain by a low-viscosity mantle layer, the asthenosphere. Asthenospheric flow may be induced by the overriding plate or by deeper mantle convection. Shear strain due to this flow can be inferred using the directional dependence of seismic wave speeds--seismic anisotropy. However, isolation of asthenospheric signals is challenging; most seismometers are located on continents, whose complex structure influences the seismic waves en route to the surface. The Cascadia Initiative, an offshore seismometer deployment in the US Pacific Northwest, offers the opportunity to analyse seismic data recorded on simpler oceanic lithosphere. Here we use measurements of seismic anisotropy across the Juan de Fuca and Gorda plates to reconstruct patterns of asthenospheric mantle shear flow from the Juan de Fuca mid-ocean ridge to the Cascadia subduction zone trench. We find that the direction of fastest seismic wave motion rotates with increasing distance from the mid-ocean ridge to become aligned with the direction of motion of the Juan de Fuca Plate, implying that this plate influences mantle flow. In contrast, asthenospheric mantle flow beneath the Gorda Plate does not align with Gorda Plate motion and instead aligns with the neighbouring Pacific Plate motion. These results show that asthenospheric flow beneath the small, slow-moving Gorda Plate is controlled largely by advection due to the much larger, faster-moving Pacific Plate.

  16. No spreading across the southern Juan de Fuca ridge axial cleft during 1994-1996

    USGS Publications Warehouse

    Chadwell, C.D.; Hildebrand, J.A.; Spiess, Fred N.; Morton, J.L.; Normark, W.R.; Reiss, C.A.

    1999-01-01

    Direct-path acoustic measurements between seafloor transponders observed no significant extension (-10 ?? 14 mm/yr) from August 1994 to September 1996 at the southern Juan de Fuca Ridge (44??40' N and 130??20' W). The acoustic path for the measurement is a 691-m baseline straddling the axial cleft, which bounds the Pacific and Juan de Fuca plates. Given an expected full-spreading rate of 56 mm/yr, these data suggest that extension across this plate boundary occurs episodically within the narrow (~1 km) region of the axial valley floor, and that active deformation is occurring between the axial cleft and the plate interior. A cleft-parallel 714-m baseline located 300 m to the west of the cleft on the Pacific plate monitored system performance and, as expected, observed no motion (+5??7 mm/yr) between the 1994 and 1996 surveys.Direct-path acoustic measurements between seafloor transponders observed no significant extension (-10 ?? 14 mm/yr) from August 1994 to September 1996 at the southern Juan de Fuca Ridge (44??40 minutes N and 130??20 minutes W). The acoustic path for the measurement is a 691-m baseline straddling the axial cleft, which bounds the Pacific and Juan de Fuca plates. Given an expected full-spreading rate of 56 mm/yr, these data suggest that extension across this plate boundary occurs episodically within the narrow (approx. 1 km) region of the axial valley floor, and that active deformation is occurring between the axial cleft and the plate interior. A cleft-parallel 714-m baseline located 300 m to the west of the cleft on the Pacific plate monitored system performance and, as expected, observed no motion (+5 ?? 7 mm/yr) between the 1994 and 1996 surveys.

  17. Pb, Sr, and Nd isotopes in basalts and sulfides from the Juan de Fuca Ridge

    SciTech Connect

    Hegner, E.; Tatsumoto, M.

    1987-10-10

    Pb, Sr, Nd isotopes of seven basalt glasses collected by the submersible Alvin from the southern Juan de Fuca Ridge (SJFR) are almost identical (/sup 206/Pb//sup 204/Pbapprox.18.45, /sup 207/Pb//sup 204/Pbapprox.15.47, /sup 208/Pb//sup 204/Pbapprox.37.81, /sup 87/Sr//sup 86/Srapprox.0.70249, /sup 143/Nd//sup 144/Ndapprox.0.51315). Whereas all basalts appear cogenetic, four of the samples have uniform abundances of U, Th, Rb, Nd, Sm, Pb, and Sr, indicating that they are also comagmatic. Two basalt glasses dredged previously at the SJFR have similar isotopic compositions but higher concentrations of U, Th, and Pb. The /sup 206/Pb//sup 204/Pb ratios are intermediate between generally less radiogenic ridge basalts from south of the Juan de Fuca Ridge (JFR) and often more radiogenic basalts from the northern JFR and NE Pacific seamounts. Sr and Nd isotopic compositions closely resemble data of other ridge basalts from the northernmost East Pacific Rise and are intermediate between isotopically more diverse seamount basalts produced nearby.

  18. Seismic anisotropy of the shallow crust at the Juan de Fuca Ridge

    USGS Publications Warehouse

    Almendros, J.; Barclay, A.H.; Wilcock, W.S.D.; Purdy, G.M.

    2000-01-01

    Microearthquake data recorded on four ocean bottom seismometers are used to study shear-wave splitting on the Endeavour Segment of the Juan de Fuca Ridge. The covariance matrix decomposition method is used to determine the sensor orientation from explosive shot data and to estimate the anisotropy parameters for 238 earthquake records. At three of the four sites, the results show a remarkably consistent fast direction parallel to the ridge axis. The time delays between the fast and the slow waves range from 40 to 200 ms, with an average of 90 ms. They are not clearly related to earthquake range, focal depth or source-receiver azimuth. The splitting of the shear waves is interpreted as an effect of structural anisotropy due to the presence of ridge-parallel cracks in the shallow crust. If we assume that anisotropy is concentrated in the upper 1-2 km, the splitting times require a high crack density of ~0.1.

  19. Propagation as a mechanism of reorientation of the Juan de Fuca ridge

    NASA Technical Reports Server (NTRS)

    Wilson, D. S.; Hey, R. N.; Nishimura, C.

    1984-01-01

    A revised model is presented of the tectonic evolution of the Juan de Fuca ridge by propagating rifting. The new model has three different relative rotation poles, covering the time intervals 17.0-8.5 Ma, 8.5-5.0 Ma, and 5.0 Ma to the present. The rotation pole shifts at 8.5 and 5.0 Ma imply clockwise shifts in the direction of relative motion of 10 deg to 15 deg. At each of these shifts, the pattern of propagation reorganizes, and the new ridges formed by propagation are at an orientation closer to orthogonal to the new direction of motion than the orientation of the preexisting ridges. The model, containing a total of seven propagation sequences, shows excellent agreement with the isochrons inferred from the magnetic anomaly data, except in areas complicated by the separate Explorer and Gorda plates. The agreement between model and data near the Explorer plate breaks down abruptly at an age of about 5 Ma, indicating that the probable cause of the rotation pole shift at that time was the separation of the Explorer plate from the Juan de Fuca plate.

  20. Biogenic iron oxyhydroxide formation at mid-ocean ridge hydrothermal vents: Juan de Fuca Ridge

    SciTech Connect

    Toner, Brandy M.; Santelli, Cara M.; Marcus, Matthew A.; Wirth, Richard; Chan, Clara S.; McCollom, Thomas; Bach, Wolfgang; Edwards, Katrina J.

    2008-05-22

    Here we examine Fe speciation within Fe-encrusted biofilms formed during 2-month seafloor incubations of sulfide mineral assemblages at the Main Endeavor Segment of the Juan de Fuca Ridge. The biofilms were distributed heterogeneously across the surface of the incubated sulfide and composed primarily of particles with a twisted stalk morphology resembling those produced by some aerobic Fe-oxidizing microorganisms. Our objectives were to determine the form of biofilm-associated Fe, and identify the sulfide minerals associated with microbial growth. We used micro-focused synchrotron-radiation X-ray fluorescence mapping (mu XRF), X-ray absorption spectroscopy (mu EXAFS), and X-ray diffraction (mu XRD) in conjunction with focused ion beam (FIB) sectioning, and highresolution transmission electron microscopy (HRTEM). The chemical and mineralogical composition of an Fe-encrusted biofilm was queried at different spatial scales, and the spatial relationship between primary sulfide and secondary oxyhydroxide minerals was resolved. The Fe-encrusted biofilms formed preferentially at pyrrhotite-rich (Fe1-xS, 0<_ x<_ 0.2) regions of the incubated chimney sulfide. At the nanometer spatial scale, particles within the biofilm exhibiting lattice fringing and diffraction patterns consistent with 2-line ferrihydrite were identified infrequently. At the micron spatial scale, Fe mu EXAFS spectroscopy and mu XRD measurements indicate that the dominant form of biofilm Fe is a short-range ordered Fe oxyhydroxide characterized by pervasive edge-sharing Fe-O6 octahedral linkages. Double corner-sharing Fe-O6 linkages, which are common to Fe oxyhydroxide mineral structures of 2-line ferrihydrite, 6-line ferrihydrite, and goethite, were not detected in the biogenic iron oxyhydroxide (BIO). The suspended development of the BIO mineral structure is consistent with Fe(III) hydrolysis and polymerization in the presence of high concentrations of Fe-complexing ligands. We hypothesize that

  1. U, Th, and Pb isotopes in hot springs on the Juan de Fuca Ridge

    NASA Technical Reports Server (NTRS)

    Chen, J. H.

    1987-01-01

    Concentrations and isotopic compositions of U, Th, and Pb in three hydrothermal fluids from the Juan de Fuca Ridge were determined from samples obtained by the Alvin submersible. The samples were enriched in Pb and Th relative to deep-sea water, and were deficient in U. No clear relationship with Mg was found, suggesting nonideal mixing between the hot hydrothermal fluids and the cold ambient seawater. Values for U-234/U-238 have a seawater signature, and show a U-234 enrichment relative to the equilibrium value. The Pb isotopic composition has a uniform midocean ridge basalt signature, and it is suggested that Pb in these fluids may represent the best average value of the local oceanic crust.

  2. Submersible observations along the southern Juan de Fuca Ridge: 1984 Alvin program.

    USGS Publications Warehouse

    Normark, W.R.; Morton, J.L.; Ross, S.L.

    1987-01-01

    In September 1984, the research submersible Alvin provided direct observations of three major hydrothermal vent areas along the southernmost segment of the Juan de Fuca Ridge (JFR). The submersible operations focuses on specific volcanologic, structural, and hydrothermal problems that had been identified during the preceding 4 years of photographic, dredging, acoustic imaging, and geophysical studies along a 12 km long section of the ridge. A continuously maintained (from 1981 to the present) net of seafloor-anchored acoustic transponders allowed the observations from Alvin to be directly tied to all previous USGS data sets and NOAA water column surveys from 1984 to the present. We review the dive program and present a brief synthesis of the geology of the vent sites together with sample and track line compilations.-from Authors

  3. Pb, Sr, and Nd isotopes in basalts and sulfides from the Juan de Fuca Ridge

    NASA Technical Reports Server (NTRS)

    Hegner, E.; Tatsumoto, M.

    1987-01-01

    Isotopic Pb, Sr, and Nd data were collected by the Alvin submersible from seven basalt glasses in the southern Juan de Fuca Ridge (JFR), giving similar ratios for Pb-206/Pb-204 of about 18.45, for Pb-207/Pb-204 of about 15.47, for Pb-208/Pb-204 of about 37.81, for Sr-87/Sr-86 of about 0.70249, and for Nd-143/Nd-144 of about 0.51315. Data suggest that the basalts are all cogenetic, and that four of the samples are also comagmatic. It is concluded that isotopic data for the JFR and seamount basalts provide additional support for the mantle blob cluster model (Allegre et al., 1984), suggesting the involvement of multiple components in the genesis of ridge basalts, and including an unusual end-member that has nonradiogenic Sr and variable Pb-206/Pb-204 isotopic compositions.

  4. Variability of low temperature hydrothermal alteration in upper ocean crust: Juan de Fuca Ridge and North Pond, Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Rutter, J.; Harris, M.; Coggon, R. M.; Alt, J.; Teagle, D. A. H.

    2014-12-01

    Over 2/3 of the global hydrothermal heat flux occurs at low temperatures (< 150°) on the ridge flanks carried by fluid volumes comparable to riverine discharge. Understanding ridge flank hydrothermal exchange is important to quantify global geochemical cycles. Hydrothermal chemical pathways are complex and the effects of water-rock reactions remain poorly constrained. Factors controlling fluid flow include volcanic structure, sediment thickness, and basement topography. This study compares the effects of low temperature alteration in two locations with contrasting hydrogeological regimes. The intermediate spreading Juan de Fuca ridge flank (JdF) in the northeast Pacific sports a thick sediment blanket. Rare basement outcrops are sites of fluid recharge and discharge. The average alteration extent (~10% secondary minerals), oxidation ratio (Fe3+/FeTOT=34%), and alteration character (orange, green, grey halos) of basement is constant with crustal age and depth along a 0.97-3.6 m.yr transect of ODP basement holes. However, vesicle fills record an increasingly complex history of successive alteration with age. In contrast, North Pond, a ~8 m.yr-old sediment-filled basin at 22N on the slow spreading Mid Atlantic Ridge, hosts rapid, relatively cool SE to NW basinal fluid flow. Average alteration extent (~10%) and oxidation ratio (33%) of Hole 395A basalts are similar to JdF. However, 395A cores are dominated by orange alteration halos, lack celadonite, but have abundant zeolite. Vesicle fill combinations are highly variable, but the most common fill progression is from oxidising to less oxidising secondary assemblages. The comparable extent of alteration between these two sites and the absence of an age relationship on the JdF suggests that the alteration extent of the upper crust is uniform and mostly established by 1 Myr. However, the variable alteration character reflects the influence of regional hydrology on hydrothermal alteration.

  5. Seismic and Acoustic Studies from a Seafloor Array on the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    McDonald, Mark Armstrong

    This dissertation consists of two related but separate studies, one a refraction seismic study of the oceanic crust and the other an acoustic study of whale behavior in the presence of noise, both using seafloor array data. The goal of the first study was to measure the lateral thickness variability in the extrusive volcanic layer on the Juan de Fuca Ridge. The Juan de Fuca Ridge is a medium rate (6 cm per year full rate), active spreading center, separating the Juan de Fuca and Pacific plates. It is a site of volcanic eruptions, associated with creation of new oceanic crust, and hydrothermal vents which are important in the chemical balance of the oceans. To better understand the mechanisms controlling hydrothermal venting and the creation of new crust, a seismic refraction survey was conducted over a 20 km by 30 km area of the ridge. This survey, conducted in August of 1990, used airguns as energy sources and ocean bottom seismometers as recorders. A 3-dimensional traveltime inversion was used to interpret extrusive volcanic layer thickness changes of 300 m, occurring over less than several kilometers laterally. These thickness changes are interpreted as lava accumulations on the low side of listric faults in an episodic spreading system. The traveltime inversion also reveals a large horizontal seismic velocity anisotropy which is confined to the upper 500 m of crust. Compressional velocities are 3.35 km/s in the ridge strike direction and 2.25 km/s across strike. This anisotropy is believed to be caused by oriented fractures within the extrusive layer. The second study involved the tracking and analysis of whale vocalizations which were recorded on the array 10 percent of the time. The goal was to determine if noises such as generated by the airguns, shipping or earthquakes affected the behavior of these fin and blue whales. The vocalization patterns allow analysis of swimming speed, direction, respiration cycle and call interaction. While no clear noise

  6. Preeruptive flow focussing in dikes feeding historical pillow ridges on the Juan de Fuca and Gorda Ridges

    NASA Astrophysics Data System (ADS)

    Yeo, I. A.; Clague, D. A.; Martin, J. F.; Paduan, J. B.; Caress, D. W.

    2013-09-01

    Linear, hummocky pillow mound volcanism dominates at slow and intermediate spreading rate mid-ocean ridges. Volcanic hummocks are thought to be formed by low effusion rates or as a result of flow focussing during effusive fissure style eruptions in which the initial dike intercepts the seafloor and erupts along its entire length. In this study, high-resolution autonomous underwater vehicle (AUV) bathymetry is used to accurately map the extents of four historical fissure eruptions of the Juan de Fuca and Gorda ridges: on the North Gorda, North Cleft, and CoAxial ridge segments. The four mapped eruptions take the form of pillow mounds, which are similar in both lithology and dimension to hummocks on the Mid-Atlantic Ridge. Pillow mounds may be isolated, or coalesce to form composite mounds, aligned as ridges or as clustered groups. In three of the four mapped sites, the eruptions were discontinuous along their lengths, with pillow mounds and composite mounds commonly separated by areas of older seafloor. This style of discontinuous eruption is inconsistent with typical en echelon fissure eruptions and is probably due to a mildly overpressured, fingering dike intersecting the seafloor along parts of its length.

  7. U, Th, and Pb isotopes in hot springs on the Juan de Fuca Ridge

    SciTech Connect

    Chen, J.H.

    1987-10-10

    The concentrations and isotopic compositions of U, Th, and Pb in three hydrothermal fluids from the Juan de Fuca Ridge were determined. The samples consisted of 10.2--57.6% of the pure hydrothermal end-members based on Mg contents. The Pb contents of the samples ranged from 34 to 87 ng/g, U from 1.3 to 3.0 ng/g, and Th from 0.2 to 7.7 pg/g. These samples showed large enrichments of Pb and Th relative to deep-sea water and some depletion of U. They did not show coherent relationships with Mg, however, indicating nonideal mixings between the hot hydrothermal fluids and cold ambient seawater. Particles filtered from these hydrothermal fluids contained significant amounts of Th and Pb which may effectively increase the concentration of these elements in the fluids when acidified. The /sup 234/U//sup 238/U values in all samples show a /sup 234/U enrichment relative to the equilibrium value and have a seawater signature. The Pb isotopic composition of the Juan de Fuca hydrothermal fluids resembles that of 21 /sup 0/N East Pacific Rise and has a uniform mid-ocean ridge basalt signature. The hydrothermal systems at oceanic spreading ridges have circulated through a large volume of basalts. Therefore Pb in these fluids may represent the best average value of the local oceanic crust. From the effects of U deposition from seawater to the crust and Pb extraction from rock to the ocean, the U/Pb ratio in the hydrothermally altered oceanic crust may be increased significantly. copyright American Geophysical Union 1987

  8. Geochemistry of Axial seamount lavas: Magmatic relationship between the Cobb hotspot and the Juan de Fuca Ridge

    SciTech Connect

    Rhodes, J.M.; Morgan, C.; Lilas, R.A. )

    1990-08-10

    Axial seamount, located along the central portion of the Juan de Fuca Ridge axis and at the eastern end of the Cobb-Eickelberg seamount chain, is the current center of the Cobb hotspot. Lava chemistry and bathymetry indicate that Axial seamount is a discrete volcanic unit, with a more productive shallow magmatic plumbing system separate from the adjacent ridge segments. Despite this classic association of spreading center and hotspot volcanic activity, there is no evidence in the lavas for geochemical or isotopic enrichment typical of hotspot or mantle plume activity. The differences in composition between the Axial seamount lavas and the Juan de Fuca Ridge lavas are attributed to melting processes rather than to any fundamental differences in their mantle source compositions. The higher magma production rates, higher Sr, and lower silica saturation in the seamount lavas relative to the ridge lavas are thought to be a consequence of melt initiation at greater depths. The melting column producing the seamount lavas is thought to be initiated in the stability field of spinel peridotite, whereas the ridge lavas are produced from a melting column initiated at shallower levels, possibly within or close to the stability field of plagioclase peridotite. Implicit in this interpretation is the conclusion that the Juan de Fuca Ridge lavas, and by analogy most MORB, are generated at shallow mantle levels, mostly within the stability field of plagioclase peridotite. This interpretation also requires that for the upwelling mantle to intersect the solidus at different depths, the mantle supplying Axial seamount must be hotter than the rest of the Juan de Fuca Ridge. Axial seamount, therefore, reflects a thermal anomaly in the mantle, rather than a geochemically enriched ocean island basalt type mantle plume.

  9. Noble gases in vent water from the Juan de Fuca Ridge

    SciTech Connect

    Kennedy, B.M. )

    1988-07-01

    Hydrothermal vent fluids collected with the DSRV Alvin from the southern limb of the Juan de Fuca Ridge are chemically unique, having chloride concentrations {approximately}2 times ambient seawater. The same fluids contain noble gases in relative abundances like 2{degree}C air-saturated seawater, the expected recharge composition. However, the absolute noble gas abundances are depleted by {approximately}30% relative to seawater. The combination of very high chloride and moderately depleted noble gases appears to require formation of a Cl-rich, gas-free brine by phase separation. This brine is mixed with recharge seawater at temperatures in excess of {approximately}340{degree}C and, therefore, deep in the hydrothermal system.

  10. Near-axis crustal structure and thickness of the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Soule, Dax; Wilcock, William S. D.; Toomey, Douglas R.; Hooft, Emilie E. E.; Weekly, Robert T.

    2016-06-01

    A model of crustal thickness and lower crustal velocities is obtained for crustal ages of 0.1-1.2 Ma on the Endeavour Segment of the Juan de Fuca Ridge by inverting travel times of crustal paths and non-ridge-crossing wide-angle Moho reflections obtained from a three-dimensional tomographic experiment. The crust is thicker by 0.5-1 km beneath a 200 m high plateau that extends across the segment center. This feature is consistent with the influence of the proposed Heckle melt anomaly on the spreading center. The history of ridge propagation on the Cobb overlapping spreading center may also have influenced the formation of the plateau. The sharp boundaries of the plateau and crustal thickness anomaly suggest that melt transport is predominantly upward in the crust. Lower crustal velocities are lower at the ends of the segment, likely due to increased hydrothermal alteration in regions influenced by overlapping spreading centers, and possibly increased magmatic differentiation.

  11. Juan de Fuca Plate Ridge-to-Trench Experiment: initial results from active source seismic imaging of the Juan de Fuca plate and Cascadia fore-arc (Invited)

    NASA Astrophysics Data System (ADS)

    Carbotte, S. M.; Canales, J.; Carton, H. D.; Han, S.; Gibson, J. C.; Janiszewski, H. A.; Horning, G.; Nedimovic, M. R.; Abers, G. A.; Trehu, A. M.

    2013-12-01

    Active source seismic data were acquired during the Juan de Fuca Ridge-to-Trench experiment (June-July 2012) to characterize the evolution and structure of the Juan de Fuca plate from formation at the ridge, through evolution in the plate interior, to subduction at the Cascadia trench. The survey provides plate-scale images of the sediments, crust, and shallowest mantle along two ridge-perpendicular transects, one extending from Axial seamount to the Oregon margin near Hydrate Ridge and the other from near Endeavour segment to Grays Harbor offshore Washington. In addition, a 450 km long trench-parallel line ~10 km seaward of the Cascadia deformation front was acquired to characterize variations in plate structure along the margin. Coincident long-streamer (8 km) multi-channel seismic (MCS) and wide-angle ocean bottom seismometer (OBS) data were collected along each transect. Using these data, our current investigations focus on the properties of the thick sediment blanket covering the Juan de Fuca plate and evidence for fluid flow at the deformation front, crustal structure within the plate interior and near the deformation front, and tracking the downgoing plate beneath the margin. Highlights include the discovery of numerous pockmarks on the seafloor providing evidence of active fluid flow up to 60 km west of the deformation front. Along the Oregon transect, a bright decollement horizon is imaged at ~1sec twtt above basement whereas at the Washington margin, protothrusts of the deformation front reach to the top of the oceanic crust. Variations in sediment properties are documented within the margin-parallel transect with changes in the stratigraphic level of decollement. While crustal thickness is quite uniform along the margin (~ 6 km), variations in crustal reflectivity and in shallowest mantle velocities are observed over ~30-50 km length scales that could be related to structural variations in the Cascadia subduction zone. Further landward, the top of the

  12. Sound field near hydrothermal vents on Axial Seamount, Juan de Fuca Ridge. Technical report

    SciTech Connect

    Little, S.A.; Stolzenbach, K.D.; Purdy, G.M.

    1990-08-10

    High-quality acoustic noise measurements were obtained by two hydrophones located 3 m and 40 m from an active hydrothermal vent on Axial Seamount, Juan de Fuca Ridge, in an effort to determine the feasibility of monitoring hydrothermal vent activity through flow noise generation. Most of the measured noise field could be attributed to ambient ocean noise sources of microseisms, distant shipping, and weather, punctuated by local ships and biological sources. Long-period, low-velocity, water/rock interface waves were detected with high amplitudes which rapidly decayed with distance from the seafloor. Detection of vent signals was hampered by unexpected spatial nonstationarity due to the shadowing effects of the calders wall. No continuous vent signals were deemed significant based on a criterion of 90% probability of detection and 5% probability of false alarm. However, a small signal near 40 Hz, with a power level of 0.0001 Pa sq/Hz was noticed on two records taken within 3 m of the Inferno black smoker. The frequency of this signal is consistent with predictions, and the power level suggests the occurrence of jet noise amplification due to convected density inhomogeneities. Keywords: Seamounts; Flow noise; Underwater acoustics; Acoustic measurement; Geothermy/noise; Ocean ridges; Underwater sound signals; Reprints; North Pacific Ocean. (EDC).

  13. Geochemistry of some gases in hydrothermal fluids from the southern Juan de Fuca Ridge

    USGS Publications Warehouse

    Evans, William C.; White, L.D.; Rapp, J.B.

    1988-01-01

    Five samples of hydrothermal fluids from two vent areas on the southern Juan de Fuca Ridge were analyzed for dissolved gases. Concentrations in the end-member hydrothermal fluid of H2 (270-527 ??mol/kg), CH4 (82-118 ??mol/kg), and CO2 (3920-4460 ??mol/kg) are well above values in ambient seawater and are similar to concentrations reported for other ridge crest hydrothermal systems. The carbon isotopic ratios of the CH4(??13C=-17.8 to -20.8) and CO2(??13C=-3.6 to -4.7) suggest that at least some of the CH4 and CO2 in the fluids is basalt-derived. The range of ??13C values for the basalt-derived CO2 is -6.8 to -9.7, calculated by assuming conservation of recharge ??CO2 during hydrothermal circulation. Apparent temperatures of equilibration between the CH4 and the basalt-derived CO2 range from 640??C to 750??C. Small amounts of ethane (C2H6/CH4??? 0.9 ?? 10-3-2.2 ?? 10-3), propane, and butane detected in the samples may also have formed in the basalt. One sample of almost pure (95.5%) hydrothermal fluid contained a significant fraction, up to 63% and 74%, respectively, of the recharge Ar and N2. This suggests that the fluid has not undergone extensive vapor-liquid phase separation. -Authors

  14. Hydrological response to a seafloor spreading episode on the Juan de Fuca ridge.

    PubMed

    Davis, Earl; Becker, Keir; Dziak, Robert; Cassidy, John; Wang, Kelin; Lilley, Marvin

    2004-07-15

    Seafloor hydrothermal systems are known to respond to seismic and magmatic activity along mid-ocean ridges, often resulting in locally positive changes in hydrothermal discharge rate, temperature and microbial activity, and shifts in composition occurring at the time of earthquake swarms and axial crustal dike injections. Corresponding regional effects have also been observed. Here we present observations of a hydrological response to seafloor spreading activity, which resulted in a negative formation-fluid pressure transient during and after an earthquake swarm in the sediment-sealed igneous crust of the Middle Valley rift of the northernmost Juan de Fuca ridge. The observations were made with a borehole seal and hydrologic observatory originally established in 1991 to study the steady-state pressure and temperature conditions in this hydrothermally active area. The magnitude of the co-seismic response is consistent with the elastic strain that would be expected from the associated earthquakes, but the prolonged negative pressure transient after the swarm is surprising and suggests net co-seismic dilatation of the upper, permeable igneous crust. The rift valley was visited four weeks after the onset of the seismic activity, but no signature of increased hydrothermal activity was detected in the water column. It appears that water, not magma, filled the void left by this spreading episode. PMID:15254534

  15. Submersible observations along the southern Juan de Fuca Ridge: 1984 Alvin Program

    NASA Astrophysics Data System (ADS)

    Normark, William R.; Morton, Janet L.; Ross, Stephanie L.

    1987-10-01

    In September 1984, the research submersible Alvin provided direct observations of three major hydrothermal vent areas along the southernmost segment of the Juan de Fuca Ridge (JFR). The submersible operations focused on specific volcanologie, structural, and hydrothermal problems that had been identified during the preceding 4 years of photographic, dredging, acoustic imaging, and geophysical studies along a 12-km-long section of the ridge. A continuously maintained (from 1981 to the present) net of seafloor-anchored acoustic transponders allowed the observations from Alvin to be directly tied to all previous U.S. Geological Survey data sets and National Oceanic and Atmospheric Administration water column surveys from 1984 to the present. The three vent areas studied are the largest of at least six areas identified by previous deep-towed camera surveys that lie within a deep cleft, which marks the axis of symmetry of the JFR in this region. The cleft appears to be the locus of eruption for this segment of the JFR. The vent areas, at least in part, are localized near what appear to be previous volcanic eruptive centers marked by extensive lava lake collapse features adjacent to the cleft at these sites. Each hydrothermal area has several active discharge sites, and sulfide deposits occur as clusters (15-100 m2) of small chimneys, individual large chimneys, or clusters of large branched chimneys. We review the dive program and present a brief synthesis of the geology of the vent sites together with sample and track line compilations.

  16. Heat Flux From the Endeavour Segment of the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Thompson, W. J.; McDuff, R. E.; Stahr, F. R.; Yoerger, D. R.; Jakuba, M.

    2005-12-01

    The very essence of a hydrothermal system is transfer of heat by a convecting fluid, yet the flux of heat remains a poorly known quantity. Past studies of heat flux consisted primarily of point measurements of temperature and fluid flow at individual vent sites and inventories of the neutrally buoyant plume above the field. In 2000 the Flow Mow project used the Autonomous Benthic Explorer (ABE) to determine heat flux from Main Endeavour Field (MEF) on the Juan de Fuca Ridge by intersecting the stems of rising buoyant plumes. ABE carries instruments to measure conductivity, temperature and depth, and a MAVS current meter to determine the vertical velocity of the fluid, after correcting for vehicle motion. Complementary work on horizontal fluxes suggests that the vertical flux measured by ABE includes both the primary high buoyancy focused "smoker" sources and also entrained diffuse flow. In 2004, ABE was again used to determine heat flux not only from MEF, but also from the other four fields in the Endeavour Segment RIDGE 2000 Integrated Study Site. In this four year interval the flux of heat from MEF has declined by approximately a factor of two. The High Rise vent field has the greatest heat flux, followed by MEF, then Mothra, Salty Dawg and Sasquatch (of order 500, 300, 100, 50 MW respectively; heat flux at Sasquatch was below detection).

  17. Lead Isotopic Compositions of the Endeavour Sulfides, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Labonte, F.; Hannington, M. D.; Cousens, B. L.; Blenkinsop, J.; Gill, J. B.; Kelley, D. S.; Lilley, M. D.; Delaney, J. R.

    2006-12-01

    32 sulfide samples from the main structures of the Endeavour vent field, Juan de Fuca Ridge, were analyzed for their Pb isotope composition. The samples were collected from 6 main vent fields between 1985 and 2005 and encompass a strike length of more than 15 km along the ridge crest. The sulfides are typical of black smoker deposits on sediment-starved mid-ocean ridges. Pb isotope compositions of the massive sulfides within the six hydrothermal fields vary within narrow ranges, with 206Pb/204Pb = 18.58 18.75, 207Pb/204Pb = 15.45 15.53 and 208Pb/204Pb = 37.84 38.10. A geographic trend is observed, with the lower Pb ratios restricted mostly to the northern part of the segment (Salty Dawg, Sasquatch and High Rise fields), and the higher Pb ratios restricted mostly to the southern part of the segment (Main Endeavour, Clam Bed and Mothra fields). Variations within individual fields are much smaller than those between fields, and variation within individual sulfide structures is within the uncertainty of the measurements. Therefore, it is unlikely that the ranges of Pb isotope compositions along the length of the segment reflect remobilization, replacement, and recrystallization of sulfides, as suggested for the observed Pb isotope variability in some large seafloor sulfide deposits. Instead, the differences in isotopic compositions from north to south are interpreted to reflect differences in the source rocks exposed to hydrothermal circulation of fluids below the seafloor. Possible sources of the somewhat more radiogenic Pb may be small amounts of buried sediment, either from turbidites or from hemipelagic sediment. This possibility is supported by high concentrations of CH4 and NHC4 found in the high-temperature vent fluids at the Main Endeavour Field, which are interpreted to reflect subseafloor interaction between hydrothermal fluids and organic material in buried sediments. However, the majority of the samples fall below and are approximately parallel to the

  18. Fluid and chemical fluxes along a buried-basement ridge in the eastern Juan de Fuca Ridge flank

    NASA Astrophysics Data System (ADS)

    Hulme, S.; Wheat, C. G.

    2010-12-01

    Hydrothermal fluid circulation within oceanic crust at low temperatures affects global biogeochemical cycles, with the volume of fluid circulation rivaling that of the world’s water flux to the oceans from rivers. Our work focuses on the best studied low temperature hydrothermal system on the eastern flank of the Juan de Fuca Ridge where a buried basement ridge 100 km from the active spreading axis has been sampled with a variety of mediums. We use data from deep sea drilling, gravity coring, and submersible operations from five sites along-strike of the buried ridge to better constrain the chemical and fluid fluxes along this transect. A transport (advection-diffusion) model is applied to the data, constraining the volumetric fluid flux per unit length within the oceanic crust from 0.05 and 0.2 m3 y-1 cm-1 and identifying conservative elements within this system. Using an average fluid flux, reactive fluxes are determined for non-conservative elements within basaltic crust for twenty-four chemical species. Conservative species include K, Cl, SO4, Ba, Sr, Cs, Mo, and Y. Only Ca and the rare earth elements Ce and Gd are produced by basaltic basement. The remaining chemical species Mg, Na, ammonium, Li, Rb, Mn, Fe, Co, Zn, Cd, U, La and Yb are all consumed within upper basaltic basement. Fluxes of potentially-bioavailable redox species ammonium, Fe, and Mn into the upper basaltic basement are 3 to 20 nmol y-1cm-2. Possible mechanisms of removal are suggested, placing constraints on microbial metabolic activity and biomineralization.

  19. Seismic Structure of the Shallow Mantle Beneath the Endeavor Segment of the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    VanderBeek, B. P.; Toomey, D. R.; Hooft, E. E.; Wilcock, W. S.; Weekly, R. T.; Soule, D. C.

    2013-12-01

    We present tomographic images of the seismic structure of the shallow mantle beneath the intermediate-spreading Endeavor segment of the Juan de Fuca ridge. Our results provide insight into the relationship between magma supply from the mantle and overlying ridge crest processes. We use seismic energy refracted below the Moho (Pn), as recorded by the Endeavor tomography (ETOMO) experiment, to image the anisotropic and isotropic P wave velocity structure. The ETOMO experiment was an active source seismic study conducted in August 2009 as part of the RIDGE2000 science program. The experimental area extends 100 km along- and 60 km across-axis and encompasses active hydrothermal vent fields near the segment center, the eastern end of the Heck seamount chain, and two overlapping spreading centers (OSCs) at either end of the segment. Previous tomographic analyses of seismic arrivals refracted through the crust (Pg), and reflected off the Moho (PmP), constrain a three-dimensional starting model of crustal velocity and thickness. These Pg and PmP arrivals are incorporated in our inversion of Pn travel-time data to further constrain the isotropic and anisotropic mantle velocity structure. Preliminary results reveal three distinct mantle low-velocity zones, inferred as regions of mantle melt delivery to the base of the crust, that are located: (i) off-axis near the segment center, (ii) beneath the Endeavor-West Valley OSC, and (iii) beneath the Cobb OSC near Split Seamount. The mantle anomalies are located at intervals of ~30 to 40 km along-axis and the low velocity anomalies beneath the OSCs are comparable in magnitude to the one located near the segment center. The direction of shallow mantle flow is inferred from azimuthal variations in Pn travel-time residuals relative to a homogeneous isotropic mantle. Continuing analysis will focus on constraining spatial variations in the orientation of azimuthal anisotropy. On the basis of our results, we will discuss the transport of

  20. Chemistry of hydrothermal solutions from the southern Juan de Fuca Ridge

    SciTech Connect

    Von Damm, K.L.; Bischoff, J.L.

    1987-10-10

    Fluids from three vent fields on the southern Juan de Fuca Ridge were sampled in September 1984 using the DSRV Alvin. The fluids are uniquely high in both chloride, which ranges up to twice the seawater value, and in metal content. Simple vapor-liquid phase separation could not have produced both the high chlorinity and gas concentrations observed in these fluids. The cause of the elevated chlorinity can not be uniquely identified but may be the result of either or a combination of two processes: (1) subsurface formation of a degassed brine and subsequent mixing of a small amount of this brine with a hydrothermal seawater which has not undergone a phase separation and (2) dissolution of a chloride-rich phase combined with a possible small loss of gas during sampling procedures. Although measured temperatures were all less than 300 /sup 0/C, quartz geothermometry suggests that the fluids have equilibrated at greater than 340 /sup 0/C. Quartz geobarometry is also in agreement with geophysical estimates of depth to the local magma chamber. copyright American Geophysical Union 1987

  1. Metals and isotopes in Juan de Fuca Ridge hydrothermal fluids and their associated solid materials

    SciTech Connect

    Hinkley, T.K.; Tatsumoto, M.

    1987-10-10

    The /sup 87/Sr//sup 86/Sr ratio of the hydrothermal solution (HTS) (0.7034) is larger than that of basalt (0.7025) at the southern vent field of the Juan de Fuca Ridge (SJFR). Both the Sr isotopic ratio for HTS and the water/rock interaction ratio lie between those at two sites farther south on the East Pacific Rise, 13 /sup 0/N and 21 /sup 0/N. These parameters may be closely related to subsurface temperatures and rates of magma ascent and to extent of faulting and surface areas of the frameworks of the hydrothermal systems. For these three Pacific Ocean sites there is no steady geographical progression of these measured parameters, nor of reported spreading rate, with increasing latitude northward. Pb and Nd isotopic measurements are uniform for all samples from the SJFR, ranging only from 18.43 to 18.58 for /sup 206/Pb//sup 204/Pb (fluids and associated solids) and centering near 0.5131 for /sup 143/Nd//sup 144/Nd (only fluids measured). Values for basalts and sulfides from the site have similar values. Relatively high /sup 206/Pb//sup 204/Pb values at the SJFR suggest the potential for the existence of an anomalous radiogenic heat source in the underlying mantle material.

  2. Numerical modeling of phase separation at Main Endeavour Field, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Singh, Shreya; Lowell, Robert P.; Lewis, Kayla C.

    2013-10-01

    Before being disrupted by a magmatic event in 1999, the vent temperatures and salinities along the axis of the Main Endeavour Field on the Juan de Fuca Ridge exhibited a quasi-steady spatial gradient in which the southern vent fluids were hotter and less saline than the northern vent fluids. We present 2-D numerical models of two phase flow in a NaCl-H2O system to understand these gradients. We consider homogenous permeability models with a range of bottom boundary temperature distributions and heterogeneous permeability models by imposing layer 2A extrusives with a constant bottom boundary temperature distribution. The aim is to understand the impact of both bottom boundary temperature and layer 2A permeability on hydrothermal fluids and to determine what combination of these controlling factors could cause the observed trend. We find that variations in bottom boundary temperature alone cannot explain the span of surface temperatures and salinities measured at the Main Endeavour Field. Heterogeneous permeability within layer 2A that has higher overall permeability in the northern part of the vent field than the southern part can reproduce the observed north to south temperature gradient, but such a permeability distribution cannot reproduce the observed salinity gradient. We conclude that both deep-seated heterogeneous permeability, perhaps localized by a fault zone, and a heterogeneous layer 2A are required to produce the trend of temperatures and salinities in vent fluids at the Main Endeavour Field prior to the 1999 event.

  3. A hydrographic transient above the Salty Dawg hydrothermal field, Endeavour segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Kellogg, J. P.; McDuff, R. E.

    2010-12-01

    During systematic repeat hydrography cruises to the Endeavour segment of the Juan de Fuca Ridge in the summers of 2004, 2005, and 2006, we encountered a transient increase in the water column heat content above the Salty Dawg hydrothermal field. First observed in July 2005 and mapped in greater detail in August 2005, this feature was not a typical event or megaplume since potential temperature anomalies were continuously elevated from the plume top to the seafloor. During the summer of 2005, the heat content in the waters above Salty Dawg was elevated ˜30 TJ, and the plume top was over 150 m higher in the water column than the other years measured. Based on scaling analyses, an order of magnitude increase in the volume flux from Salty Dawg would be required to generate a neutrally buoyant plume of this size. This observation was unexpected because no substantial earthquakes were detected in the time frame of this increased heat flux. The duration of the transient suggests possible forcing mechanisms: advancement of a cracking front, a small-scale dike intrusion, aseismic crustal movement, fracture of a flow constriction to a previously unaccessible reservoir, an increase of heat in an underlying magma chamber, or movement of melt within the axial magma chamber. The transient disappeared before returning in August 2006, likely due to thermal expansion of shallow host rock, decreasing the permeability. Should such increases in seafloor heat flux prove to be common, the rate of hydrothermal cooling could be faster than previously thought.

  4. Geology of a vigorous hydrothermal system on the Endeavour segment, Juan de Fuca Ridge

    SciTech Connect

    Delaney, J.R.; Robigou, V.; McDuff, R.E. ); Tivey, M.K. )

    1992-12-10

    A high-precision, high-resolution geologic map explicitly documents relationships between tectonic features and large steep-sided, sulfide-sulfate-silica deposits in the vigorously venting Endeavour hydrothermal field near the northern end of the Juan de Fuca Ridge. Location of the most massive sulfide structures appears to be controlled by intersections of ridge-parallel normal faults and other fracture-fissure sets that trend oblique to, and perpendicular to the overall structural fabric of the axial valley. As presently mapped, the field is about 200 by 400 m on a side and contains at least 15 large (> 1,000 m[sup 3]) sulfide edifices and many tens of smaller, commonly inactive, sulfide structures. The larger sulfide structures are also the most vigorously venting features in the field; they are commonly more than 30 m in diameter and up to 20 m in height. Maximum venting temperatures of 375[degrees]C are associated with the smaller structures in the northern portion of the field are consistently 20[degrees]-30[degrees]C lower. Hydrothermal output from individual active sulfide features varies from no flow in the lower third of the edifice to vigorous output from fracture-controlled black smoker activity near the top of the structures. Two types of diffuse venting in the Endeavour field include a lower temperature 8[degrees]-15[degrees]C output through colonies of large tubeworms and 25[degrees]-50[degrees]C vent fluid that seems to percolate through the tops of overhanging flanges. The large size and steep-walled nature of these structures evidently results from sustained venting in a mature hydrothermal system, coupled with dual mineral depositional mechanisms involving vertical growth by accumulation of chimney sulfide debris and lateral growth by means of flange development.

  5. Surficial permeability of the axial valley seafloor: Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Hearn, Casey K.; Homola, Kira L.; Johnson, H. Paul

    2013-09-01

    Hydrothermal systems at mid-ocean spreading centers play a fundamental role in Earth's geothermal budget. One underexamined facet of marine hydrothermal systems is the role that permeability of the uppermost seafloor veneer plays in the distribution of hydrothermal fluid. As both the initial and final vertical gateway for subsurface fluid circulation, uppermost seafloor permeability may influence the local spatial distribution of hydrothermal flow. A method of deriving a photomosaic from seafloor video was developed and utilized to estimate relative surface permeability in an active hydrothermal area on the Endeavour Segment of the Juan de Fuca Ridge. The mosaic resolves seafloor geology of the axial valley seafloor at submeter resolution over an area greater than 1 km2. Results indicate that the valley walls and basal talus slope are topographically rugged and unsedimented, providing minimal resistance to fluid transmission. Elsewhere, the axial valley floor is capped by an unbroken blanket of low-permeability sediment, resisting fluid exchange with the subsurface reservoir. Active fluid emission sites were restricted to the high-permeability zone at the base of the western wall. A series of inactive fossil hydrothermal structures form a linear trend along the western bounding wall, oriented orthogonal to the spreading axis. High-temperature vent locations appear to have migrated over 100 m along-ridge-strike over the decade between surveys. While initially an expression of subsurface faulting, this spatial pattern suggests that increases in seafloor permeability from sedimentation may be at least a secondary contributing factor in regulating fluid flow across the seafloor interface.

  6. Pressures of Partial Crystallization of Magmas from the Juan de Fuca Ridge: Implications for Crustal Accretion

    NASA Astrophysics Data System (ADS)

    Scott, J. L.; Barton, M.

    2010-12-01

    Plate spreading at the mid-ocean ridges is accompanied by intrusion of dikes and eruption of lava along the ridge axis. It has been suggested that the depth of magma chambers that feed the flows and dikes is related to the rate of spreading. As part of a larger effort to examine this hypothesis, we determined the depths of magma chambers beneath the intermediate spreading Juan de Fuca Ridge (JdF) which extends from the Blanco fracture zone at about 44.5 degrees North to the Triple junction of the JdF, Nootka Fault, and the Socanco fracture zone at 48.7 degrees North. Pressures of partial crystallization were determined by comparing the compositions of natural liquids (glasses) with those of experimental liquids in equilibrium with olivine, plagioclase, and clinopyroxene at different pressures and temperatures using the method described by Kelley and Barton (2008). Chemical analyses mid-ocean ridge basalts glasses sampled from along the JdF were used as liquid compositions. Samples with anomalous chemical compositions and samples that yielded pressures associated with unrealistically large uncertainties were filtered out of the database. The calculated pressures for the remaining 533 samples were used to calculate the depths of partial crystallization and to identify the likely location of magma chambers. Preliminary results indicate that the pressure of partial crystallization decreases from 2 to 1±0.5 kbars from the Blanco fracture zone to the north along the Cleft segment of the ridge. Calculated pressures remain approximately constant at 0.87±0.53 kbars along ridge segments to the north of the Cleft. These low pressures for the remaining segments of the ridge are interpreted to indicate magma chambers at depths of 1.3-4.9 km and agree reasonably well with the depths of seismically imaged tops of axial magma chambers (2-3 km) (Canales et al 2009). The higher pressures obtained for lavas erupted along the Cleft segment of the JdF agree very well with recent

  7. Microbial diversity within Juan de Fuca ridge basement fluids sampled from oceanic borehole observatories

    NASA Astrophysics Data System (ADS)

    Jungbluth, S.; Bowers, R.; Lin, H.; Hsieh, C.; Cowen, J. P.; Rappé, M.

    2012-12-01

    Three generations of sampling and instrumentation platforms known as Circulation Obviation Retrofit Kit (CORK) observatories affixed to Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) boreholes are providing unrivaled access to fluids originating from 1.2-3.5 million-years (Myr) old basaltic crust of the eastern flank of the Juan de Fuca ridge. Borehole fluid samples obtained via a custom seafloor fluid pumping and sampling system coupled to CORK continuous fluid delivery lines are yielding critical insights into the biogeochemistry and nature of microbial life inhabiting the sediment-covered basement environment. Direct microscopic enumeration revealed microbial cell abundances that are 2-41% of overlying bottom seawater. Snapshots of basement fluid microbial diversity and community structure have been obtained through small subunit ribosomal RNA (SSU rRNA) gene cloning and sequencing from five boreholes that access a range of basement ages and temperatures at the sediment-basement interface. SSU rRNA gene clones were derived from four different CORK installations (1026B, 1301A, 1362A, and 1362B) accessing relatively warmer (65°C) and older (3.5 Myr) ridge flank, and one location (1025C) accessing relatively cooler (39°C) and younger (1.2 Myr) ridge flank, revealing that warmer basement fluids had higher microbial diversity. A sampling time-series collected from borehole 1301A has revealed a microbial community that is temporally variable, with the dominant lineages changing between years. Each of the five boreholes sampled contained a unique microbial assemblage, however, common members are found from both cultivated and uncultivated lineages within the archaeal and bacterial domains, including meso- and thermophilic microbial lineages involved with sulfur cycling (e.g Thiomicrospira, Sulfurimonas, Desulfocapsa, Desulfobulbus). In addition, borehole fluid environmental gene clones were also closely related to uncultivated lineages

  8. Upper Crustal Seismic Velocity Structure of the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Weekly, R. T.; Wilcock, W. S.; Toomey, D. R.; Hooft, E. E.; Wells, A. E.

    2010-12-01

    We report preliminary results from an active-source seismic tomography experiment that was conducted along the intermediate-spreading Endeavour Segment of the Juan de Fuca Ridge in 2009. The overarching objective of the experiment is to test competing hypotheses for what governs the scale and intensity of magmatic and hydrothermal processes at mid-ocean ridges. Previous models of crustal accretion inferred that ridge-basin topography observed at the Endeavour results from alternating periods of enhanced or reduced magma supply from the mantle. Alternatively, a recent seismic reflection study has imaged a crustal magma chamber underlying the central portion of the Endeavour, which may indicate that variations in seafloor topography instead result from dike-induced faulting that occurs within the upper crust, adjacent to the axial magma chamber. The first model predicts a thicker high-porosity eruptive layer and lower velocities beneath topographic highs, while the second model is compatible with a uniform pattern of volcanic accretion. The experiment used 68 four-component ocean-bottom seismometers (OBSs) at 64 sites to record 5,567 airgun shots from the 6600 in3 airgun array of the R/V Marcus G. Langseth. Three nested shooting grids were collected to image the three-dimensional crustal and upper mantle velocity structure of the segment at multiple spatial scales. We use first-arriving crustal phases (Pg) recorded by the two grids with the densest shot-receiver spacing, the 24 x 8 km2 vent field grid and the 60 x 20 km2 crustal grid, to image the fine-scale (< 1 km) three-dimensional velocity structure of the upper few kilometers of crust at the segment scale. We employ a non-linear tomographic method that utilizes a shortest-path ray-tracing algorithm with columns of nodes sheared vertically to include effects of seafloor topography. To date, we have manually picked 13,000 Pg phases located within 10 km of 17 OBSs. The full analysis will include ~40,000 Pg travel

  9. Temperature and Redox Effect on Mineral Colonization in Juan de Fuca Ridge Flank Subsurface Crustal Fluids

    PubMed Central

    Baquiran, Jean-Paul M.; Ramírez, Gustavo A.; Haddad, Amanda G.; Toner, Brandy M.; Hulme, Samuel; Wheat, Charles G.; Edwards, Katrina J.; Orcutt, Beth N.

    2016-01-01

    To examine microbe-mineral interactions in subsurface oceanic crust, we evaluated microbial colonization on crustal minerals that were incubated in borehole fluids for 1 year at the seafloor wellhead of a crustal borehole observatory (IODP Hole U1301A, Juan de Fuca Ridge flank) as compared to an experiment that was not exposed to subsurface crustal fluids (at nearby IODP Hole U1301B). In comparison to previous studies at these same sites, this approach allowed assessment of the effects of temperature, fluid chemistry, and/or mineralogy on colonization patterns of different mineral substrates, and an opportunity to verify the approach of deploying colonization experiments at an observatory wellhead at the seafloor instead of within the borehole. The Hole U1301B deployment did not have biofilm growth, based on microscopy and DNA extraction, thereby confirming the integrity of the colonization design against bottom seawater intrusion. In contrast, the Hole U1301A deployment supported biofilms dominated by Epsilonproteobacteria (43.5% of 370 16S rRNA gene clone sequences) and Gammaproteobacteria (29.3%). Sequence analysis revealed overlap in microbial communities between different minerals incubated at the Hole U1301A wellhead, indicating that mineralogy did not separate biofilm structure within the 1-year colonization experiment. Differences in the Hole U1301A wellhead biofilm community composition relative to previous studies from within the borehole using similar mineral substrates suggest that temperature and the diffusion of dissolved oxygen through plastic components influenced the mineral colonization experiments positioned at the wellhead. This highlights the capacity of low abundance crustal fluid taxa to rapidly establish communities on diverse mineral substrates under changing environmental conditions such as from temperature and oxygen. PMID:27064928

  10. Sulfide geochronology along the Endeavour Segment of the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Jamieson, John W.; Hannington, Mark D.; Clague, David A.; Kelley, Deborah S.; Delaney, John R.; Holden, James F.; Tivey, Margaret K.; Kimpe, Linda E.

    2013-07-01

    Forty-nine hydrothermal sulfide-sulfate rock samples from the Endeavour Segment of the Juan de Fuca Ridge, northeastern Pacific Ocean, were dated by measuring the decay of 226Ra (half-life of 1600 years) in hydrothermal barite to provide a history of hydrothermal venting at the site over the past 6000 years. This dating method is effective for samples ranging in age from ˜200 to 20,000 years old and effectively bridges an age gap between shorter- and longer-lived U-series dating techniques for hydrothermal deposits. Results show that hydrothermal venting at the active High Rise, Sasquatch, and Main Endeavour fields began at least 850, 1450, and 2300 years ago, respectively. Barite ages of other inactive deposits on the axial valley floor are between ˜1200 and ˜2200 years old, indicating past widespread hydrothermal venting outside of the currently active vent fields. Samples from the half-graben on the eastern slope of the axial valley range in age from ˜1700 to ˜2925 years, and a single sample from outside the axial valley, near the westernmost valley fault scarp is ˜5850 ± 205 years old. The spatial relationship between hydrothermal venting and normal faulting suggests a temporal relationship, with progressive younging of sulfide deposits from the edges of the axial valley toward the center of the rift. These relationships are consistent with the inward migration of normal faulting toward the center of the valley over time and a minimum age of onset of hydrothermal activity in this region of 5850 years.

  11. Hydrothermal fluid composition at Middle Valley, Northern Juan de Fuca Ridge: Temporal and spatial variability

    NASA Astrophysics Data System (ADS)

    Cruse, Anna M.; Seewald, Jeffrey S.; Saccocia, Peter J.; Zierenberg, Robert

    Hydrothermal fluids were collected in July 2000 from the Dead Dog and Ore Drilling Program (ODP) Mound vent fields at Middle Valley, a sediment-covered spreading center on the northern Juan de Fuca Ridge. Measured fluid temperatures varied from 187° to 281°C in focused flow vents and 40°C in ODP Hole 1035F. Cl concentrations indicate that ODP Mound fluids undergo phase separation in the subsurface, whereas Dead Dog fluids do not. The lack of phase separation at Dead Dog is consistent with other geochemical indicators of lower subsurface temperatures. Cooling and equilibration with quartz after phase separation at the ODP Mound results in exit temperatures and silica concentrations that are indistinguishable from those at Dead Dog. The sulfur isotopic composition of aqueous ΣH2S indicates extensive reduction of seawater SO4 and leaching of basaltic sulfur at both areas. A new area of venting, which resulted from drilling operations during ODP Leg 169, was discovered on the eastern side of the ODP Mound. The fluids in the new area have compositions that are similar to those of Hole 1035H and Shiner Bock, except for lower H2 and higher H2S concentrations. These differences reflect the conversion of pyrite to pyrrhotite in the ODP Mound as fluids react with sulfide minerals during upflow. Fluid temperatures and compositions have remained constant between 1990 and 2000 indicating that subsurface reaction zone conditions did not change over this period. Near constant concentrations of sediment-derived mobile trace elements suggest that the residence time of fluids in a high-temperature reservoir exceeds 10 years.

  12. Microbial Primary Productivity in Hydrothermal Vent Chimneys at Middle Valley, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Olins, H. C.; Rogers, D.; Frank, K. L.; Girguis, P. R.; Vidoudez, C.

    2012-12-01

    Chemosynthetic primary productivity supports hydrothermal vent ecosystems, but the extent of that productivity has not been well measured. To examine the role that environmental temperature plays in controlling carbon fixation rates, and to assess the degree to which microbial community composition, in situ geochemistry, and mineralogy influence carbon fixation, we conducted a series of shipboard incubations across a range of temperatures (4, 25, 50 and 90°C) and at environmentally relevant geochemical conditions using material recovered from three hydrothermal vent chimneys in the Middle Valley hydrothermal vent field (Juan de Fuca Ridge). Net rates of carbon fixation (CFX) were greatest at lower temperatures, and were similar among structures. Rates did not correlate with the mineralogy or the geochemical composition of the high temperature fluids at each chimney. No obvious patterns of association were observed between carbon fixation rates and microbial community composition. Abundance of selected functional genes related to different carbon fixation pathway exhibited striking differences among the three study sites, but did not correlate with rates. Natural carbon isotope ratios implicate the Calvin Benson Bassham Cycle as the dominant mechanism of primary production in these systems, despite the abundance of genes related to other pathways (and presumably some degree of activity). Together these data reveal that primary productivity by endolithic communities does not exhibit much variation among these chimneys, and further reveal that microbial activity cannot easily be related to mineralogical and geochemical assessments that are made at a coarser scale. Indeed, the relationships between carbon fixation rates and community composition/functional gene abundance were also likely obfuscated by differences in scale at which these measurements were made. Regardless, these data reveal the degree to which endolithic, anaerobic carbon fixation contributes to

  13. Temperature and Redox Effect on Mineral Colonization in Juan de Fuca Ridge Flank Subsurface Crustal Fluids.

    PubMed

    Baquiran, Jean-Paul M; Ramírez, Gustavo A; Haddad, Amanda G; Toner, Brandy M; Hulme, Samuel; Wheat, Charles G; Edwards, Katrina J; Orcutt, Beth N

    2016-01-01

    To examine microbe-mineral interactions in subsurface oceanic crust, we evaluated microbial colonization on crustal minerals that were incubated in borehole fluids for 1 year at the seafloor wellhead of a crustal borehole observatory (IODP Hole U1301A, Juan de Fuca Ridge flank) as compared to an experiment that was not exposed to subsurface crustal fluids (at nearby IODP Hole U1301B). In comparison to previous studies at these same sites, this approach allowed assessment of the effects of temperature, fluid chemistry, and/or mineralogy on colonization patterns of different mineral substrates, and an opportunity to verify the approach of deploying colonization experiments at an observatory wellhead at the seafloor instead of within the borehole. The Hole U1301B deployment did not have biofilm growth, based on microscopy and DNA extraction, thereby confirming the integrity of the colonization design against bottom seawater intrusion. In contrast, the Hole U1301A deployment supported biofilms dominated by Epsilonproteobacteria (43.5% of 370 16S rRNA gene clone sequences) and Gammaproteobacteria (29.3%). Sequence analysis revealed overlap in microbial communities between different minerals incubated at the Hole U1301A wellhead, indicating that mineralogy did not separate biofilm structure within the 1-year colonization experiment. Differences in the Hole U1301A wellhead biofilm community composition relative to previous studies from within the borehole using similar mineral substrates suggest that temperature and the diffusion of dissolved oxygen through plastic components influenced the mineral colonization experiments positioned at the wellhead. This highlights the capacity of low abundance crustal fluid taxa to rapidly establish communities on diverse mineral substrates under changing environmental conditions such as from temperature and oxygen. PMID:27064928

  14. Precipitation and growth of barite within hydrothermal vent deposits from the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Jamieson, John William; Hannington, Mark D.; Tivey, Margaret K.; Hansteen, Thor; Williamson, Nicole M.-B.; Stewart, Margaret; Fietzke, Jan; Butterfield, David; Frische, Matthias; Allen, Leigh; Cousens, Brian; Langer, Julia

    2016-01-01

    Hydrothermal vent deposits form on the seafloor as a result of cooling and mixing of hot hydrothermal fluids with cold seawater. Amongst the major sulfide and sulfate minerals that are preserved at vent sites, barite (BaSO4) is unique because it requires the direct mixing of Ba-rich hydrothermal fluid with sulfate-rich seawater in order for precipitation to occur. Because of its extremely low solubility, barite crystals preserve geochemical fingerprints associated with conditions of formation. Here, we present data from petrographic and geochemical analyses of hydrothermal barite from the Endeavour Segment of the Juan de Fuca Ridge, northeast Pacific Ocean, in order to determine the physical and chemical conditions under which barite precipitates within seafloor hydrothermal vent systems. Petrographic analyses of 22 barite-rich samples show a range of barite crystal morphologies: dendritic and acicular barite forms near the exterior vent walls, whereas larger bladed and tabular crystals occur within the interior of chimneys. A two component mixing model based on Sr concentrations and 87Sr/86Sr of both seawater and hydrothermal fluid, combined with 87Sr/86Sr data from whole rock and laser-ablation ICP-MS analyses of barite crystals indicate that barite precipitates from mixtures containing as low as 17% and as high as 88% hydrothermal fluid component, relative to seawater. Geochemical modelling of the relationship between aqueous species concentrations and degree of fluid mixing indicates that Ba2+ availability is the dominant control on mineral saturation. Observations combined with model results support that dendritic barite forms from fluids of less than 40% hydrothermal component and with a saturation index greater than ∼0.6, whereas more euhedral crystals form at lower levels of supersaturation associated with greater contributions of hydrothermal fluid. Fluid inclusions within barite indicate formation temperatures of between ∼120 °C and 240 °C during

  15. Uniformity and diversity in the composition of mineralizing fluids from hydrothermal vents on the southern Juan de Fuca Ridge.

    USGS Publications Warehouse

    Philpotts, J.A.; Aruscavage, P. J.; Von Damm, K. L.

    1987-01-01

    Abundances of Li, Na, K, Rb, Ca, Sr, Ba, Mn, Fe, Zn, and Si have been determined in fluid samples from 7 vents located in three areas on the southern Juan de Fuca Ridge. The hydrothermal component estimated from the Mg contents of the samples ranges from 7% to 76%. Concentrations of Fe and Si, among other elements, in acid-stabilized solutions appear to be generally representative of the parental hydrothermal fluids, but some Zn determinations and most Ba values appear to be too low.-from Authors

  16. Monitoring Change on Hydrothermal Edifices by Photogrammetric Time Series: Case Studies from the Endeavour Segment (Juan de Fuca Ridge)

    NASA Astrophysics Data System (ADS)

    Heesemann, M.; Kwasnitschka, T.; Kelley, D. S.; Mihaly, S. F.

    2015-12-01

    High-resolution photogrammetric surveys derived from ROV or AUV imagery yield seafloor geometry at centimeter resolution with full color texture while modeling overhangs and crevasses, generating vastly more detailed terrain models compared to most acoustic methods. The models furthermore serve as geographic reference frames for localized studies. Repetitive surveys consequently facilitate the precise, quantitative study of edifice buildup and erosion as well as the development of the biological habitat. We compare data gathered by the Ocean Networks Canada maintenance cruises with earlier surveys at two sites (Mothra, Main Endeavour Field) along the Endeavour Segment of the Juan de Fuca Ridge.

  17. High-Resolution Imaging of Axial Volcano, Juan de Fuca ridge.

    NASA Astrophysics Data System (ADS)

    Arnulf, A. F.; Harding, A. J.; Kent, G. M.

    2014-12-01

    To date, seismic experiments have been key in our understanding of the internal structure of volcanic systems. However, most experiments, especially subaerial-based, are often restricted to refraction geometries with limited numbers of sources and receivers, and employ smoothing constraints required by tomographic inversions that produce smoothed and blurry images with spatial resolutions well below the length scale of important features that define these magmatic systems. Taking advantage of the high density of sources and receivers from multichannel seismic (MCS) data should, in principle, allow detailed images of velocity and reflectivity to be recovered. Unfortunately, the depth of mid-ocean ridges has the detrimental effect of concealing critical velocity information behind the seafloor reflection, preventing first arrival travel-time tomographic approaches from imaging the shallowest and most heterogeneous part of the crust. To overcome the limitations of the acquisition geometry, here we are using an innovative multistep approach. We combine a synthetic ocean bottom experiment (SOBE), 3-D traveltime tomography, 2D elastic full waveform and a reverse time migration (RTM) formalism, and present one of the most detailed imagery to date of a massive and complex magmatic system beneath Axial seamount, an active submarine volcano that lies at the intersection of the Juan de Fuca ridge and the Cobb-Eickelberg seamount chain. We present high-resolution images along 12 seismic lines that span the volcano. We refine the extent/volume of the main crustal magma reservoir that lies beneath the central caldera. We investigate the extent, volume and physical state of a secondary magma body present to the southwest and study its connections with the main magma reservoir. Additionally, we present a 3D tomographic model of the entire volcano that reveals a subsiding caldera floor that provides a near perfect trap for the ponding of lava flows, supporting a "trapdoor

  18. Massive sulfides in a sedimented rift valley, northern Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Davis, Earl E.; Goodfellow, Wayne D.; Bornhold, Brian D.; Adshead, John; Blaise, Bertrand; Villinger, Heiner; Le Cheminant, Gina M.

    1987-03-01

    A number of mounds each several hundred meters across and up to sixty meters high have been observed with SeaMARC II acoustic imagery and Seabeam bathymetry in the sediment-filled axial valley at the northern end of the Juan de Fuca Ridge. The mounds are located a few kilometers west of the eastern valley-bounding normal fault scarp where the local sediment fill is approximately 300 m thick. All of the mounds are believed to be of hydrothermal origin, and one is associated with anomalously high heat flow in excess of 1 W m -2. A piston core collected from that mound comprises coarse clastic sulfide units interbedded with sulfidic muds. Hydrothermal minerals present in the 2.3 m section include pyrrhotite, pyrite, marcasite, sphalerite, chalcopyrite, iss (intermediate solid solution in the Cu sbnd Fe sbnd Zn sbnd S system), chalcopyrrhotite, galena, talc, barite, and amorphous silica. Mineral fabrics of the clasts indicate that the material was precipitated at or near the sea floor by mixing of hot hydrothermal fluids with cold seawater. Low concentrations of Zn, Cu, Cd, and Ag relative to those found in unsedimented ridge hydrothermal deposits, and the presence of pyrrhotite as an early phase mineral indicates that the vent fluids have been modified by reaction with sediments beneath the mound. Rapid sedimentation in a rift valley is clearly conducive to the formation of large hydrothermal mineral deposits like those believed to be present within and beneath these mounds. The relatively impermeable sediment cover insulates the crust, inhibits groundwater recharge, promotes long-lived discharge at a restricted number of sites, provides a substrate for the efficient subsurface precipitation of minerals, and through continued sedimentation, protects surficial deposits from the corrosive effects of seawater. No reliable estimate of the bulk composition of the mounds can be made with existing data, but their size is comparable to major hydrothermal mineral deposits

  19. Endeavour Segment, Juan de Fuca Ridge, Integrated Studies Site (ISS) Update and Opportunities

    NASA Astrophysics Data System (ADS)

    Butterfield, D.; Ridge Community

    2003-12-01

    The Ridge 2000 (R2K) Integrated Studies bull's eye on the Juan de Fuca Ridge is focused on the Main Endeavour hydrothermal field, located on the central portion of the Endeavour Segment. This vent field is one of the most vigorously venting systems along the global mid-ocean ridge spreading network, hosting at least 18 large sulfide structures that contains more than100 smokers. Prior to a magmatic event in 2000 some of the edifices had been venting 380C, volatile-rich fluids with extremely low chlorinities for a decade. In addition to the Main Endeavour Field there are four other known high temperature vent fields spaced approximately 2 kilometers apart along the segment (with hints of more) and abundant areas of diffuse flow, both nearby and distal to the high temperature venting. Diffuse flow from the structures and from a variety of basaltic-hosted sites provides rich habitats abundant with microbial and macrofaunal communities. There are well-developed gradients in volatile concentrations along axis that may reflect influence from a sedimentary source to the north, and high chlorinity fluids vent from the most southern (Mothra) and northern fields (Sasquatch). Twenty years of research have laid a firm base for the 5-year plans of R2K at this site, which include examining the response of this segment to perturbations induced by tectonic and magmatic events, identification of the reservoirs, fluxes, and feedbacks of mass and energy at this site, and predictive modeling coupled with field observations. Since designation as an IS site, high-resolution bathymetric mapping (EM300) and an extensive multi-channel seismic survey have been conducted along the entire segment. Smaller focused areas have also been mapped at meter resolution by SM2000 sonar. Intense field programs in 2003 established the first in-situ seismic array along a mid-ocean ridge, which includes installation of a buried broadband seismometer and 7 short-period seismometers emplaced within basaltic

  20. Objective classification of oceanic ridge-crest terrains using two-dimensional spectral models of bathymetry: Application to the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Fox, Christopher G.

    1996-12-01

    An important application of detailed bathymetric mapping is the interpretation of geological processes based on the nature of the fine-scale morphology of the seafloor. This interpretation is usually accomplished through qualitative analysis of contour maps. In this paper, an objective classification technique, based on a two-dimensional spectral model of bathymetry developed by Fox and Hayes (1985) is applied to detailed Sea Beam data from the Juan de Fuca Ridge. Parameters of the model can be directly related to seafloor properties corresponding to 1) isotropic (non-directionally dependent) roughness; 2) anisotropic (directionally dependent) roughness; 3) orientation of the anisotropic component; and 4) spectral rool-off ( ˜ fractal dimension), by fitting the model surface to two-dimensional amplitude spectra of bathymetry determined on a regular grid over the study area. A test area was selected which encompasses the southern volcanic rift zone of Axial Volcano and the northern terminus of the Vance Segment. Parameters of the model clearly define the contrast between the constructional volcanic terrain (rough, isotropic, with high fractal dimension) and the tectonic extensional terrain (smoother, anisotropic, with low fractal dimension). An agglomerative, hierarchical cluster analysis is applied to the data, independent of spatial information, to delineate groups of spectra with similar characteristics. Distinct, mappable regions, corresponding to volcanic and tectonic provinces, are objectively determined. Also, coherent sub-regions of consistent spectral properties occur within the larger volcanic/tectonic divisions. The classification is extended to the Juan de Fuca Ridge system from 44°30' N to 47°20' N through combining these results with an a priori technique (K-means clustering). Broad-scale physiographic regions of the Juan de Fuca Ridge are delineated by the technique, which may aid geologists in the interpretation of crustal accretion processes at

  1. Vent Field Distribution and Evolution Along the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Kelley, D. S.; Delaney, J. R.; Lilley, M. D.; Butterfield, D. A.

    2001-12-01

    Five major vent fields have now been discovered along the Endeavour Segment of the Juan de Fuca Ridge. From the north to the south they include Sasquatch, Salty Dawg, High Rise, Main Endeavour, and Mothra. Spacing between the distinct, high-temperature fields increases from the north to the south. For example Sasquatch is located 1.6 km north of Salty Dawg and Mothra is 2.7 km south of the Main Endeavour Field. In addition to changes in spacing of the vent fields along axis there are also dramatic changes in the style, intensity, and thermal-chemical characteristics of venting. The newly discovered Sasquatch field extends for >200 m in length, and venting is limited to a few isolated, small structures that reach 284° C. Active venting is confined to the northern portion of the field. In contrast, extinct, massive sulfide edifices and oxidized sulfide talus can be followed continuously for over 200 m along a 25-30 m wide, 020 trending ridge indicating that this field was very active in the past. In contrast to the delicate active structures, older extinct structures reach at least 25 m in height and the aspect ratios are similar to active pillars in the Mothra Field 7.5 km, to the south. It is unclear if venting at this site represents rejuvenation of the field, or whether it is in a waning stage. Within Salty Dawg, vent fluid temperatures reach 296° C and vigorous venting is constrained to a few, multi-flanged edifices that reach 25 m in height and 25 m in length. The field hosts over 25 structures, oxidized sulfide is abundant, and diffuse flow is dominant. Fluid compositions and temperatures are consistent with Salty Dawg being in a waning stage of evolution. Venting intensity and incidence of venting increase dramatically at High Rise where numerous multi-flanged structures are active; temperatures reach 343° C. The most intense and active of the fields is the Main Endeavour, with at least 21 actively venting, multi-flanged edifices that contain at least 100

  2. Estimating Heat Transfer from Grotto Mound, NEPTUNE Canada Cabled Observatory, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Rona, P. A.; Bemis, K. G.; Xu, G.

    2012-12-01

    Heat flux is a fundamental property of a seafloor hydrothermal system that relates to magnitude of sub-seafloor heat source and biosphere conditions, to distribution and style of seafloor venting and benthic biota, to chemical flux, plume formation, and dispersal of biological matter in the water column. We are working to estimate heat flux from Grotto mound, the site of the NEPTUNE Canada Cabled Observatory in the Main Endeavour Field on the Juan de Fuca Ridge. The mound is formed of two sulfide edifices that lie between ~2190 and 2180 m isobaths: 1) an elliptical edifice with major NE-SW-trending axis ~30 m long and minor axis ~ 14 m wide (area ~ 330 m2); 2) a columnar edifice ~ 10 m in diameter and 10 m high (area ~80 m2) named the North Tower, situated across a narrow (~5 m wide) saddle (area ~40 m2) at the W end of the elliptical edifice. Several black smokers discharge relatively small plumes at the E end of the elliptical edifice. A cluster of vigorous black smokers discharge from the top of North Tower and merge to form a large plume. Patchy diffuse flow occurs in areas around all of the black smokers and in the saddle between the two edifices. We are in process of measuring heat flux from components of hydrothermal discharge on Grotto mound, as follows: 1) for smokers on the North Tower an integrated heat flux of 28-55 MW is calculated based on temperature measurements in the initial 20 m rise of the plume assuming that the highest temperatures measured are closest to those of the plume centerline ; 2) for smokers on the E end of the elliptical edifice based on measurements of flow rate from video and acoustic Doppler phase shift, video of vent diameters, and in situ temperature measurements; 3) for discharge from flanges on some chimneys based on video of flow and in situ temperature measurements; 4) for diffuse flow based on area measured by Acoustic Scintillation Thermography and direct measurements of temperature and flow rate. We are evaluating

  3. Direct Measurements of Hydrothermal Heat Output at Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Germanovich, L. N.; di Iorio, D.; Genc, G.; Hurt, R. S.; Lowell, R. P.; Holden, J. F.; Butterfield, D. A.; Olson, E. J.

    2009-12-01

    Heat output and fluid flow are key parameters for characterizing seafloor hydrothermal systems at oceanic spreading centers. In particular, they are essential for examining partition of heat and geochemical fluxes between discrete and diffuse flow components. Hydrothermal heat output also constrains permeability of young oceanic crust and thickness of the conductive boundary layer separating hydrothermal circulation from the underlying magmatic heat source. Over the past several years, we have deployed a number of relatively simple devices to make direct measurements of focused and diffuse flow. Most recently, we have used cup anemometer and turbine flow meters to measure fluid flow and heat flux at individual high-temperature vents and diffuse flow sites. The turbine flow meter (Figure 1) includes a titanium rotor assembly housed within a stainless steel tube and supported by sapphire bearings. The device can be used at different seafloor settings for measurements of both diffuse and focused flow. The spin of the rotor blades is videotaped to acquire the angular velocity, which is a function of the flow rate determined through calibration. We report data obtained during four cruises to the Main Endeavor and High Rise vent fields, Juan de Fuca Ridge (JdFR), between 2007 and 2009. Overall more than 50 successful measurements of heat flow have been made on a variety of high-, medium-, and low-temperature hydrothermal sites on the Endeavor, Mothra, and High Rise structures. For example, the velocity of diffuse flow at Endeavor ranged from ~1 to ~10 cm/sec. The flow velocity from black smokers varied from ~10 cm/sec to ~1 m/sec, which appears to be similar to EPR 9°N. Typical measurements of heat flux obtained at JdFR ranged from ~1 kW for diffuse flow to ~1 MW for black smokers. Although it is difficult to extrapolate the data and obtain the integrated heat output for a vent field on JdFR, the data are used to characterize the heat fluxes from individual vent

  4. Heat flux from black smokers on the Endeavour and Cleft segments, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Ginster, Ursula; Mottl, Michael J.; von Herzen, Richard P.

    1994-03-01

    We have estimated the heat flux from black smoker vents on the Juan de Fuca Ridge to evaluate their importance for heat transfer from young oceanic crust. The velocity and temperature of smoker effluent were measured from the manned submersible Alvin within a few centimeters of vent orifices, using a turbine flowmeter with an attached temperature probe. Exit velocity was calculated from a simple plume model, and vent orifices were measured in photographs and video records. The estimated power output from smokers alone is 49 plus or minus 13 MW for the Plume site, Vent 1 and Vent 3 on the southern Cleft segment near 45 deg N; 364 plus or minus 73 MW for the main vent field on the Endeavour Segment near 48 deg N; and 122 plus or minus 61 MW for the Tubeworm field 2 km north. The estimates for the Cleft and Tubeworm fields could be too low because of undiscovered vents. These values constitute only 4% to 14% of the total advective heat flux estimated for these vent fields from measurements in the nonbuoyant plume and of diffuse flow at the seafloor, indicating that most of the heat advected at these hydrothermal vent sites is carried by diffuse rather than focused flow. Values for individual smokers vary from 0.1 to 94 MW, with an average of 6.2 MW at the Endeavour field and 3.1 MW at the Cleft field. Our estimates agree well at all scales with those of Bemis et al. (1993) based on measurements made during the same dives, in some cases simultaneously, up to 50 m high in the buoyant plume. The good agreement between the two techniques implies that little diffuse flow at either high or low temperature is incorporated into the buoyant plumes generated by smokers at these sites. Velocity-temperature measurements at vents excavated by Alvin could not be modeled successfully, suggesting that vent structures may grow in equilibrium with the force of the exiting water such that orifice size is determined by volume flux. At the Endeavour field the heat flux is focused by

  5. Free-living bacterial communities associated with tubeworm (Ridgeia piscesae) aggregations in contrasting diffuse flow hydrothermal vent habitats at the Main Endeavour Field, Juan de Fuca Ridge

    PubMed Central

    Forget, Nathalie L; Kim Juniper, S

    2013-01-01

    We systematically studied free-living bacterial diversity within aggregations of the vestimentiferan tubeworm Ridgeia piscesae sampled from two contrasting flow regimes (High Flow and Low Flow) in the Endeavour Hydrothermal Vents Marine Protected Area (MPA) on the Juan de Fuca Ridge (Northeast Pacific). Eight samples of particulate detritus were recovered from paired tubeworm grabs from four vent sites. Most sequences (454 tag and Sanger methods) were affiliated to the Epsilonproteobacteria, and the sulfur-oxidizing genus Sulfurovum was dominant in all samples. Gammaproteobacteria were also detected, mainly in Low Flow sequence libraries, and were affiliated with known methanotrophs and decomposers. The cooccurrence of sulfur reducers from the Deltaproteobacteria and the Epsilonproteobacteria suggests internal sulfur cycling within these habitats. Other phyla detected included Bacteroidetes, Actinobacteria, Chloroflexi, Firmicutes, Planctomycetes, Verrucomicrobia, and Deinococcus–Thermus. Statistically significant relationships between sequence library composition and habitat type suggest a predictable pattern for High Flow and Low Flow environments. Most sequences significantly more represented in High Flow libraries were related to sulfur and hydrogen oxidizers, while mainly heterotrophic groups were more represented in Low Flow libraries. Differences in temperature, available energy for metabolism, and stability between High Flow and Low Flow habitats potentially explain their distinct bacterial communities. PMID:23401293

  6. Free-living bacterial communities associated with tubeworm (Ridgeia piscesae) aggregations in contrasting diffuse flow hydrothermal vent habitats at the Main Endeavour Field, Juan de Fuca Ridge.

    PubMed

    Forget, Nathalie L; Kim Juniper, S

    2013-04-01

    We systematically studied free-living bacterial diversity within aggregations of the vestimentiferan tubeworm Ridgeia piscesae sampled from two contrasting flow regimes (High Flow and Low Flow) in the Endeavour Hydrothermal Vents Marine Protected Area (MPA) on the Juan de Fuca Ridge (Northeast Pacific). Eight samples of particulate detritus were recovered from paired tubeworm grabs from four vent sites. Most sequences (454 tag and Sanger methods) were affiliated to the Epsilonproteobacteria, and the sulfur-oxidizing genus Sulfurovum was dominant in all samples. Gammaproteobacteria were also detected, mainly in Low Flow sequence libraries, and were affiliated with known methanotrophs and decomposers. The cooccurrence of sulfur reducers from the Deltaproteobacteria and the Epsilonproteobacteria suggests internal sulfur cycling within these habitats. Other phyla detected included Bacteroidetes, Actinobacteria, Chloroflexi, Firmicutes, Planctomycetes, Verrucomicrobia, and Deinococcus-Thermus. Statistically significant relationships between sequence library composition and habitat type suggest a predictable pattern for High Flow and Low Flow environments. Most sequences significantly more represented in High Flow libraries were related to sulfur and hydrogen oxidizers, while mainly heterotrophic groups were more represented in Low Flow libraries. Differences in temperature, available energy for metabolism, and stability between High Flow and Low Flow habitats potentially explain their distinct bacterial communities. PMID:23401293

  7. Stable isotope studies of vent fluids and chimney minerals, southern Juan de Fuca Ridge: Sodium metasomatism and seawater sulfate reduction

    SciTech Connect

    Shanks W.C. III; Seyfried W.E. Jr.

    1987-10-10

    Sulfur isotope values (delta/sup 34/S) or H/sub 2/S in vent fluids from the southern Juan de Fuca Ridge hydrothermal sites range from 4.0 to 7.4% and are variably /sup 34/S-enriched with respect to coexisting inner wall chimney sulfides. Chimney sulfides range from 1.6 to 5.7%. The chimneys consist of Fe-sphalerite zoned to inner zinc sulfide and chalcopyrite ( +- isocubanite)-pyrrhotite lining channels. Sulfide from inner walls of type A chimneys have the lightest delta/sup 34/S values. Type B chimneys (porous, unzoned, low-Fe-sphalerite) have the isotopically heaviest chimney sulfides and occur at vent sites distal to the along-axis shallow point of the ridge crest, hence distal to the magma chamber. These variations are largely ascribed to sulfate reduction by ferrous iron in the hydrothermal fluid in chimneys of substrate mounds, probably due to transitory entrainment of ambient sulfate-bearing seawater. The delta/sup 18/O values of end-member hydrothermal fluids range from 0.6 to 0.8%, significantly lower than the delta/sup 18/O values at 21 /sup 0/N vent fluids. The deltaD values of the fluid samples range from -2.5 to 0.5%. Isotopic differences from the 21 /sup 0/N fluids may be due to slightly higher water/rock ratios, approximately 1.0, in the southern Juan de Fuca Ridge hydrothermal system. Admixture of a small amount of residual brine from an earlier phase separation even may have contributed water with low deltaD values.

  8. Hot spot-ridge crest convergence in the northeast Pacific

    SciTech Connect

    Karsten, J.L.; Delaney, J.R. )

    1989-01-10

    Evolution of the Juan de Fuca Ridge during the past 7 m.y. has been reconstructed taking into account both the propagating rift history and migration of the spreading center in the 'absolute' (fixed hot spot) reference frame. Northwestward migration of the spreading center (at a rate of 30 km/m.y.) has resulted in progressive encroachment of the ridge axis on the Cobb Hot Spot and westward jumping of the central third of the ridge axis more recently than 0.5 Ma. Seamounts in the Cobb-Eickelberg chain are predicted to display systematic variations in morphology and petrology, and a reduction in the age contrast between the edifice and underlying crust, as a result of the ridge axis approach. Relative seamount volumes also indicate that magmatic output of the hot spot varied during this interval, with a reduction in activity between 2.5 and 4.5 Ma, compared with relatively more robust activity before and after this period. Spatial relationships determined in this reconstruction allow hypotheses relating hot spot activity and rift propagation to be evaluated. In most cases, rift propagation has been directed away from the hot spot during the time period considered. Individual propagators show some reduction in propagation rate as separation between the propagating rift tip and hot spot increases, but cross comparison of multiple propagators does not uniformly display the same relationship. No obvious correlation exists between propagation rate and increasing proximity of the hot spot to the ridge axis or increasing hot spot output. Taken together, these observations do not offer compelling support for the concept of hot spot driven rift propagation. However, short-term reversals in propagation direction at the Cobb Offset coincide with activity of the Heckle melting anomaly, suggesting that local propagation effects may be related to excess magma supply at the ridge axis.

  9. Uniformity and diversity in the composition of mineralizing fluids from hydrothermal vents on the southern Juan de Fuca Ridge

    SciTech Connect

    Philpotts, J.A.; Aruscavage, P.J.; Von Damm, K.L.

    1987-10-10

    Abundances of Li, Ni, K, Rb, Ca, Sr, Ba, Mn, Fe, Zn, and Si have been determined in fluid samples from seven vents located in three areas on the southern Juan de Fuca Ridge. The hydrothermal component estimated from the Mg contents of the samples ranges from 7% to 76%. Concentrations of Fe and Si, among the other elements, in acid-stabilized solutions appear to be generally representative of the parental hydrothermal fluids, but some Zn determinations and most Ba values appear to be too low. Thermodynamic calculations indicate that the acidified samples remain supersaturated with respect to silica, barite, and pyrite; unacidified samples are supersaturated, in addition with respect to ZnS, FeS, and many silicate phases. Within the constraints of limited sampling there appear to be differences in fluid compositions both within and between the three vent areas. Some uniform differences in the elemental abundances predicted for hydrothermal end-member fluids might be due to inmixing of fresh seawater at depth in the hydrothermal system. The Juan de Fuca hydrothermal fluids contain more Fe but otherwise have relative elemental abundances fairly similar to those in 13 /sup 0/N (East Pacific Rise) fluids, albeit at higher levels. In contrast, fluids from 21 /sup 0/N (East Pacific Rise) and Galapagos have lower K/Rb and much lower Sr and Na abundances; these compositional features probably result from interaction of these fluids with a different mineral assemblage, possibly more mature greenstone. copyright American Geophysical Union 1987

  10. Understanding Plume Bending at Grotto Vent on the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Xu, G.; Rabinowitz, J.; Rona, P. A.; Jackson, D. R.; Jones, C. D.

    2011-12-01

    Our improved understanding of black smoker plume bending derives from acoustic imaging of the plume at Grotto, a 30 m diameter vent cluster in the Main Endeavour Field, Juan de Fuca Ridge. In July 2000, the VIP2000 cruise collected 15 acoustic images over 24 hours. In September 2010, the Cabled Observatory Vent Imaging Sonar (COVIS) was connected to the NEPTUNE Canada Endeavour Observatory and acquired a 29 day time series capturing plume bending in 479 independent images. Inclination and declination are extracted for one or more plumes from the acoustic images using 2D Gaussian fitting. The bending of the large plume above the northwest end of Grotto is consistent with a dominant tidal sloshing and secondary rift valley inflow based a spectral analysis of the COVIS time series compared with a spectral analysis of current data from 2.9 km north of Grotto. The smaller plume above the eastern end of Grotto behaves in a more complicated fashion as it sometimes bends towards the larger plume. The overall shape of the larger plume is highly variable: sometimes the plume just leans in the direction of the presumed ambient current; other times, the plume bends-over and, in a few cases, the plume bends in two or more directions (forming a sinusoidal shape). Several factors influence bending direction, magnitude and shape. First, for a fluctuating plume, the instantaneous plume centerline wiggles around within the time-averaged plume boundaries; this will certainly produce a "sinusoidal" shape and may be the best explanation for the small scale multi-directional bending observed in individual acoustic images. Second, the transition from jet to plume could produce a change in bending magnitude (but not direction); however, this is unlikely to be visible on the acoustic images as the transition from jet to plume is anticipated to occur within the first 1 m of rise. Third, the ratio of rise velocity W to cross-flow velocity U controls the magnitude and direction of bending

  11. A detailed study of the Cobb Offset of the Juan de Fuca Ridge: Evolution of a propagating rift

    NASA Astrophysics Data System (ADS)

    Johnson, H. Paul; Karsten, Jill L.; Delaney, John R.; Davis, Earl E.; Currie, Ralph G.; Chase, Richard L.

    1983-03-01

    The Cobb Offset on the northern portion of the Juan de Fuca Ridge has been identified as the tip of a northward propagating rift [Hey and Wilson, 1982]. Map compilations of magnetic and seismic data from four new cruises define the present locus of spreading and volcanism on the two ridge segments abutting the Offset and permit detailed modeling of the recent evolution within this transform zone. The axis of recent spreading on the southern ridge segment bends from the normal ridge trend (N20°E) to a N-S trend, north of 47°15'N. The spreading axis on the northern ridge segment generally defines a N20°E trend, except at the southern terminus, where the spreading center is offset slightly to the east. The two spreading centers overlap by about 33 km in the Offset vicinity, and there is evidence of recent volcanism on both segments. Present ridge axis morphology exhibits a transitional sequence from a symmetrical, axial high along the more `normal' portions of each ridge segment to a grabenlike depression as the tip is approached. The magnetic anomaly patterns observed in the Cobb Offset vicinity are not consistent with the patterns predicted by models of continuous, northward propagation. The magnetic anomaly patterns of the Brunhes Epoch require an event of rapid northward propagation about 0.7 m.y. B.P., followed by a more gradual southward propagation in the middle Brunhes Epoch; most recently, the spreading center on the southern ridge has extended northward to its present configuration. Prior to the Brunhes Epoch, modeling of the magnetic anomaly patterns does not indicate a unique solution; however, net propagation has been northward. We present alternative models for the period beginning 1.7 m.y. B.P. In the first model, the Cobb Offset has evolved by a series of northward and southward events of propagation, with net advance to the north. In the second model, stable asymmetric spreading from overlapping ridge segments has evolved into a transform fault

  12. Mineralogical studies of sulfide samples and volatile concentrations of basalt glasses from the southern Juan de Fuca Ridge

    NASA Technical Reports Server (NTRS)

    Brett, Robin; Evans, Howard T., Jr.; Wandless, M. V.; Gibson, E. K., Jr.; Hedenquist, Jeffrey W.

    1987-01-01

    Sulfide samples obtained from Alvin dives on the southern Juan de Fuca Ridge were examined, showing the presence of two previously undiscovered minerals, both formed at low temperatures. The first detection of lizardite, starkeyite, and anatase in such an environment is also reported. Sulfide geothermometry involving the Cu-Fe-S system shows a vent temperature of less than 328 C for one sample. Ice-melting temperatures on inclusions from this sample are about -2.8 C, and fluid inclusion studies on crystals near this sample show pressure-corrected homogenization temperatures of 268 and 285 C. Volatile concentrations from vesicle-free basalt glass from the vent field are found to be about 0.0013 wt pct CO2 and 0.16 wt pct H2O.

  13. Spectra and magnitudes of T-waves from the 1993 earthquake swarm on the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Schreiner, Anthony E.; Fox, Christopher G.; Dziak, Robert P.

    1995-01-01

    A swarm of earthquakes on the crest of the Juan de Fuca Ridge was detected in June and July 1993 by a network of hydrophones. The activity migrated 60 km along the crest, suggesting a lateral dike injection and the possibility of a volcanic eruption. Subsequent geologic and oceanographic investigations confirmed that an eruption had taken place. Examination of the individual acoustic arrivals shows changes in the character of the signal that are consistent with an injection of magma. A reduction in the rise time of the wave packet and a proportional increase in high frequency energy was observed and is interpreted to result from a shoaling of the earthquake source region. Second, the source magnitudes were largest at the onset of the swarm and became smaller over time, also consistent with shoaling of the dike. The appearance of the T-wave arrivals changed significantly 5 days after the beginning of the swarm, potentially indicating the onset of a surface eruption.

  14. Regional patterns of hydrothermal alteration of sediments as interpreted from seafloor reflection coefficients, Middle Valley, Juan De Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Rohr, Kristin M. M.; Schmidt, Ulrike; Groschel-Becker, Henrike

    1993-09-01

    Reflection coefficients of the seafloor have been calculated from three multi-channel seismic reflection profiles across Middle Valley of the Juan de Fuca ridge. Seafloor reflection coefficients in this sedimented rift valley are high over an active hydrothermal vent and adjacent to major offset faults. Comparison of our measurements to drilling results from Leg 139 shows that high reflection coefficients over an active vent mound are produced by cemented sediments. Large reflection coefficients adjacent to major faults may have a similar origin and indicate that ongoing faulting creates pathways for hydrothermal fluids which alter the sediments and result in higher densities and velocities. Since 30 Hz seismic energy responds to the top 50 m of sediments, we are looking at the integrated response of hydrothermal alteration over tens of thousands of years. This is the first time seafloor reflection coefficients have been used to identify highly altered sediments in a region of deep-water hydrothermal activity.

  15. Estimates of crustal permeability on the Endeavour segment of the Juan de Fuca mid-ocean ridge

    NASA Astrophysics Data System (ADS)

    Wilcock, William S. D.; McNabb, Alex

    1996-02-01

    Observational studies of hydrothermal venting on the Endeavour segment of the Juan de Fuca Ridge place strong constraints on the spacing and area of vent fields, the depth of circulation, and the hydrothermal heat flux. A method is described to estimate a uniform crustal permeability from these parameters under the assumptions that upflow is confined to a narrow plume underlying each vent field and downflow can be described by potential flow into a point sink at the base of each plume. For a reasonable range of parameter values, the isotropic permeability of the Endeavour lies in the range 6 × 10 -13 to 6 × 10 -12 m 2. A significant elongation of vent fields along-axis suggests that the permeability structure is strongly anisotropic, with the across-axis permeability about an order of magnitude lower than the permeability in orthogonal directions.

  16. Geochemistry and petrology of andesites from the north rift zone of Axial Seamount, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Smithka, I. N.; Perfit, M. R.; Clague, D. A.; Wanless, V. D.

    2014-12-01

    In 2013, the ROV Doc Ricketts onboard R/V Western Flyer explored ~4 km of an elongate pillow ridge up to ~300 m high along the eastern edge of the north rift zone of Axial Seamount. The steep-sided volcanic ridge is constructed of large pillow lavas up to 2-3 m in diameter and smaller elongated pillow tubes. Of the 27 samples collected during dive D526, all but one are andesites making it one of the largest confirmed high-silica exposures along a mid-ocean ridge (MOR). Based on radiocarbon ages of sediment on top of flows, the mounds are at least ~1390 years old. This minimum age is much younger than the 56 Ka age calculated based on distance from the rift axis, indicating eruption off-axis through older, colder crust and supporting the hypothesis and model calculations that extensive fractional crystallization (>85%) caused the high silica content. The andesitic lavas are primarily glassy, highly vesicular, crusty, and sparsely phyric with small (~1 mm) plagioclase crystals and olivine, clinopyroxene, and Fe-Ti oxide microphenocrysts. Microprobe analyses of glasses are similar to wax-core samples previously collected from this area but are more compositionally variable. Excluding one basalt (7.7 wt% MgO) sampled between mounds, the lavas are basaltic andesites and andesites (53-59 wt% SiO2) with <3 wt% MgO and 12.8-15.7 wt% FeO concentrations. Incompatible trace element abundances are ~4-6 times more enriched than in Axial Seamount T-MORB. Primitive mantle-normalized patterns are similar to those of high-silica lavas from other MORs (southern Juan de Fuca Ridge, 9N East Pacific Rise) with significant positive U anomalies, large negative Sr anomalies, small negative Eu anomalies, and slight positive Zr-Hf anomalies. The andesites are more enriched in light rare earth elements than basalts from Axial Seamount ((La/Yb)N 1.35-1.4 vs. 0.7-1.27) and N-MORB from the southern Juan de Fuca Ridge. The andesites also have high Cl (~0.3-0.6 wt%) and H2O (~1.60-1.71 wt

  17. Stable isotope studies of vent fluids and chimney minerals, southern Juan de Fuca Ridge: Sodium metasomatism and seawater sulfate reduction

    NASA Astrophysics Data System (ADS)

    Shanks, Wayne C., III; Seyfried, William E., Jr.

    1987-10-01

    Sulfur isotope values (δ34S) of H2S in vent fluids from the southern Juan de Fuca Ridge hydrothermal sites range from 4.0 to 7.4‰ and are variably 34S-enriched with respect to coexisting inner wall chimney sulfides. Chimney sulfides range from 1.6 to 5.7‰. The chimneys consist of Fe-sphalerite zoned to inner zinc sulfide and chalcopyrite (± isocubanite)-pyrrhotite lining channels. Sulfide from inner walls of type A chimneys have the lightest δ34S values. Type B chimneys (porous, unzoned, low-Fe-sphalerite) have the isotopically heaviest chimney sulfides and occur at vent sites distal to the along-axis shallow point of the ridge crest, hence distal to the magma chamber. These variations are largely ascribed to sulfate reduction by ferrous iron in the hydrothermal fluid in chimneys or substrate mounds, probably due to transitory entrainment of ambient sulfate-bearing seawater. The δ18O values of end-member hydrothermal fluids range from 0.6 to 0.8‰, significantly lower than the δ18O values at 21°N vent fluids. The δD values of the fluid samples range from -2.5 to 0.5‰. Isotopic differences from the 21°N fluids may be due to slightly higher water/rock ratios, approximately 1.0, in the southern Juan de Fuca Ridge hydrothermal system. Admixture of a small amount of residual brine from an earlier phase separation event may have contributed water with low δD values. Sulfate reduction occurs in the deep (2.3 km) hydrothermal reaction zone; a small amount of seawater sulfate passes through the zone of anhydrite precipitation during recharge of the hydrothermal system and is reduced by reaction with pyrrhotite in basalt. Sulfide from pyrrhotite is mixed with 34S-enriched sulfate-derived sulfide to produce pyrite having δ34S values of about 3.0‰ and H2S having values of about 2.1‰ in the ascending fluid. Requisite acidity is provided by Na-metasomatism at about 370°C, yielding albite- and epidote-rich alteration phases.

  18. Upper crustal seismic structure of the Endeavour segment, Juan de Fuca Ridge from traveltime tomography: Implications for oceanic crustal accretion

    NASA Astrophysics Data System (ADS)

    Weekly, Robert T.; Wilcock, William S. D.; Toomey, Douglas R.; Hooft, Emilie E. E.; Kim, Eunyoung

    2014-04-01

    isotropic and anisotropic P wave velocity structure of the upper oceanic crust on the Endeavour segment of the Juan de Fuca Ridge is studied using refracted traveltime data collected by an active-source, three-dimensional tomography experiment. The isotropic velocity structure is characterized by low crustal velocities in the overlapping spreading centers (OSCs) at the segment ends. These low velocities are indicative of pervasive tectonic fracturing and persist off axis, recording the history of ridge propagation. Near the segment center, velocities within the upper 1 km show ridge-parallel bands with low velocities on the outer flanks of topographic highs. These features are consistent with localized thickening of the volcanic extrusive layer from eruptions extending outside of the axial valley that flow down the fault-tilted blocks that form the abyssal hill topography. On-axis velocities are generally relatively high beneath the hydrothermal vent fields likely due to the infilling of porosity by mineral precipitation. Lower velocities are observed beneath the most vigorous vent fields in a seismically active region above the axial magma chamber and may reflect increased fracturing and higher temperatures. Seismic anisotropy is high on-axis but decreases substantially off axis over 5-10 km (0.2-0.4 Ma). This decrease coincides with an increase in seismic velocities resolved at depths ≥1 km and is attributed to the infilling of cracks by mineral precipitation associated with near-axis hydrothermal circulation. The orientation of the fast-axis of anisotropy is ridge-parallel near the segment center but curves near the segment ends reflecting the tectonic fabric within the OSCs.

  19. Draft Genome Sequences of Pseudoalteromonas telluritireducens DSM 16098 and P. spiralis DSM 16099 Isolated from the Hydrothermal Vents of the Juan de Fuca Ridge.

    PubMed

    Zhang, Huan; Liu, Rui; Wang, Mengqiang; Wang, Hao; Gao, Qiang; Hou, Zhanhui; Zhou, Zhi; Gao, Dahai; Wang, Lingling

    2016-01-01

    This report describes the draft genome sequences of two strains, Pseudoalteromonas telluritireducens DSM 16098 and P. spiralis DSM 16099, which were isolated from hydrothermal vents of the Juan de Fuca Ridge. The reads generated by an Ion Torrent PGM were assembled into contigs with total sizes of 4.4 Mb and 4.1 Mb for DSM 16098 and DSM 16099, respectively. PMID:27563045

  20. Fluid rare earth element anlayses from geothermal wells located on the Reykjanes Peninsula, Iceland and Middle Valley seafloor hydrothermal system on the Juan de Fuca Ridge.

    DOE Data Explorer

    Andrew Fowler

    2015-05-01

    Results for fluid rare earth element analyses from four Reykjanes peninsula high-temperature geothermal fields. Data for fluids from hydrothermal vents located 2400 m below sea level from Middle Valley on the Juan de Fuca Ridge are also included. Data have been corrected for flashing. Samples preconcentrated using a chelating resin with IDA functional group (InertSep ME-1). Analyzed using an Element magnetic sector inductively coupled plasma mass spectrometry (ICP-MS).

  1. Draft Genome Sequences of Pseudoalteromonas telluritireducens DSM 16098 and P. spiralis DSM 16099 Isolated from the Hydrothermal Vents of the Juan de Fuca Ridge

    PubMed Central

    Liu, Rui; Wang, Mengqiang; Wang, Hao; Gao, Qiang; Hou, Zhanhui; Zhou, Zhi; Gao, Dahai

    2016-01-01

    This report describes the draft genome sequences of two strains, Pseudoalteromonas telluritireducens DSM 16098 and P. spiralis DSM 16099, which were isolated from hydrothermal vents of the Juan de Fuca Ridge. The reads generated by an Ion Torrent PGM were assembled into contigs with total sizes of 4.4 Mb and 4.1 Mb for DSM 16098 and DSM 16099, respectively. PMID:27563045

  2. Activity and abundance of denitrifying bacteria in the subsurface biosphere of diffuse hydrothermal vents of the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Bourbonnais, A.; Juniper, S. K.; Butterfield, D. A.; Devol, A. H.; Kuypers, M. M. M.; Lavik, G.; Hallam, S. J.; Wenk, C. B.; Chang, B. X.; Murdock, S. A.; Lehmann, M. F.

    2012-11-01

    Little is known about fixed nitrogen (N) transformation and elimination at diffuse hydrothermal vents where anoxic fluids are mixed with oxygenated crustal seawater prior to discharge. Oceanic N sinks that remove bio-available N ultimately affect chemosynthetic primary productivity in these ecosystems. Using 15N paired isotope techniques, we determined potential rates of fixed N loss pathways (denitrification, anammox) and dissimilatory nitrate reduction to ammonium (DNRA) in sulfidic hydrothermal vent fluids discharging from the subsurface at several sites at Axial Volcano and the Endeavour Segment on the Juan de Fuca Ridge. We also measured physico-chemical parameters (i.e., temperature, pH, nutrients, H2S and N2O concentrations) as well as the biodiversity and abundance of chemolithoautotrophic nitrate-reducing, sulfur-oxidizing γ-proteobacteria (SUP05 cluster) using sequence analysis of amplified small subunit ribosomal RNA (16S rRNA) genes in combination with taxon-specific quantitative polymerase chain reaction (qPCR) assays. Denitrification was the dominant N loss pathway in the subsurface biosphere of the Juan de Fuca Ridge, with rates of up to ~1000 nmol N l-1 day-1. In comparison, anammox rates were always < 5 nmol N l-1 day-1 and below the detection limit at most of the sites. DNRA rates were up to ~150 nmol N l-1 day-1. These results suggest that bacterial denitrification out-competes anammox in sulfidic hydrothermal vent waters. Taxon-specific qPCR revealed that γ-proteobacteria of the SUP05 cluster sometimes dominated the microbial community (SUP05/total bacteria up to 38%). Significant correlations were found between fixed N loss (i.e., denitrification, anammox) rates and in situ nitrate and dissolved inorganic nitrogen (DIN) deficits in the fluids, indicating that DIN availability may ultimately regulate N loss in the subsurface. Based on our rate measurements, and on published data on hydrothermal fluid fluxes and residence times, we estimated

  3. Activity and abundance of denitrifying bacteria in the subsurface biosphere of diffuse hydrothermal vents of the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Bourbonnais, A.; Juniper, S. K.; Butterfield, D. A.; Devol, A. H.; Kuypers, M. M. M.; Lavik, G.; Hallam, S. J.; Wenk, C. B.; Chang, B. X.; Murdock, S. A.; Lehmann, M. F.

    2012-04-01

    Little is known about nitrogen (N) transformations in general, and the elimination of N in particular, at diffuse vents where anoxic hydrothermal fluids have mixed with oxygenated crustal seawater prior to discharge. Oceanic N sinks that remove bio-available N ultimately affect chemosynthetic primary productivity in these ecosystems. Using 15N paired isotope techniques, we determined potential rates of fixed N-loss pathways (denitrification, anammox) and dissimilative nitrate reduction to ammonium (DNRA) in sulfidic hydrothermal vent fluids discharging from the subsurface at several sites at Axial Volcano and the Endeavour Segment on the Juan de Fuca Ridge. We also measured physico-chemical parameters (i.e. temperature, pH, nutrients, H2S and N2O concentrations) as well as the biodiversity and abundance of chemolithotrophic nitrate-reducing, sulfur-oxidizing γ-proteobacteria (SUP05 cluster) using sequence analysis of amplified small subunit ribosomal RNA (16S rRNA) genes in combination with taxon-specific quantitative polymerase chain reaction (qPCR) assays. Denitrification was the dominant N-loss pathway in the subsurface biosphere of the Juan de Fuca Ridge, with rates of up to ~1000 nmol N l-1 day-1. In comparison, anammox rates were always <5 nmol N l-1 day-1 and below the detection limit at most of the sites. DNRA rates were up to 152 nmol N l-1 day-1. These results suggest that bacterial denitrification out-competes anammox in sulfidic hydrothermal vent waters. Taxon-specific qPCR revealed that γ-proteobacteria of the SUP05 cluster sometimes dominated the microbial community (SUP05/total bacteria up to 38%). Significant correlation existed between fixed N-loss (i.e., denitrification, anammox) rates and in-situ nitrate and dissolved inorganic nitrogen (DIN) deficits in the fluids, indicating that DIN availability may ultimately regulate N-loss in the subsurface. Based on our rate measurements, and on published data on hydrothermal fluid fluxes and residence

  4. Compressional and Shear Wave Structure of the Upper Crust Beneath the Endeavour Segment, Juan De Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Kim, E.; Toomey, D. R.; Hooft, E. E. E.; Wilcock, W. S. D.; Weekly, R. T.; Lee, S. M.; Kim, Y.

    2014-12-01

    We present tomographic images of the compressional (Vp) and shear (Vs) wave velocity structure of the upper crust beneath the Endeavour segment of the Juan de Fuca Ridge. This ridge segment is bounded by the Endeavour and Cobb overlapping spreading centers (OSCs) to the north and south, respectively. Near the segment center an axial magma chamber (AMC) reflector underlies 5 hydrothermal vent fields. Our analysis uses data from the Endeavour tomography (ETOMO) experiment. A prior study of the Vp structure indicates that the shallow crust of the Endeavour segment is strongly heterogeneous [Weekly et al., 2014]. Beneath the OSCs Vp is anomalously low, indicating tectonic fracturing. Near the segment center, upper crustal Vp is relatively high beneath the hydrothermal vent fields, likely due to infilling of porosity by mineral precipitation. Lower velocities are observed immediately above the AMC, reflecting increased fracturing or higher temperatures. Anisotropic tomography reveals large amplitude ridge-parallel seismic anisotropy on-axis (>10%), but decreases in the off-axis direction over 5-10 km. Here we use crustal S-wave phases (Sg) — generated by P-to-S conversions near the seafloor — to better constrain crustal properties. Over half the OBSs in the ETOMO experiment recorded horizontal data on two channels that are of sufficiently high quality that we can orient the geophones using the polarizations of water waves from shots within 12 km. For these OBSs, crustal Sg phases are commonly visible out to ranges of ~20-25 km. We invert the Sg data separately for Vs structure, and also jointly invert Pg and Sg data to constrain the Vp/Vs ratio. Preliminary inversions indicate that Vs and Vp/Vs varies both laterally and vertically. These results imply strong lateral variations in both the physical (e.g., crack density and aspect ratio) and chemical (e.g., hydration) properties of oceanic crust.

  5. Fine-scale heat flow, shallow heat sources, and decoupled circulation systems at two sea-floor hydrothermal sites, Middle Valley, northern Juan de Fuca Ridge

    SciTech Connect

    Stein, J.S.; Fisher, A.T.; Langseth, M.; Jin, W.; Iturrino, G.; Davis, E.

    1998-12-01

    Fine-scale heat-flow patterns at two areas of active venting in Middle Valley, a sedimented rift on the northern Juan de Fuca Ridge, provide thermal evidence of shallow hydrothermal reservoirs beneath the vent fields. The extreme variability of heat flow is explained by conductive heating immediately adjacent to vents and shallow circulation within sediments above the reservoir. This secondary circulation is hydrologically separated from the deeper system feeding the vents by a shallow conductive lid within the sediments. A similar separation of shallow and deep circulation may also occur at sediment-free ridge-crest hydrothermal environments.

  6. Quantitative estimate of heat flow from a mid-ocean ridge axial valley, Raven field, Juan de Fuca Ridge: Observations and inferences

    NASA Astrophysics Data System (ADS)

    Salmi, Marie S.; Johnson, H. Paul; Tivey, Maurice A.; Hutnak, Michael

    2014-09-01

    A systematic heat flow survey using thermal blankets within the Endeavour segment of the Juan de Fuca Ridge axial valley provides quantitative estimates of the magnitude and distribution of conductive heat flow at a mid-ocean ridge, with the goal of testing current models of hydrothermal circulation present within newly formed oceanic crust. Thermal blankets were deployed covering an area of 700 by 450 m in the Raven Hydrothermal vent field area located 400 m north of the Main Endeavour hydrothermal field. A total of 176 successful blanket deployment sites measured heat flow values that ranged from 0 to 31 W m-2. Approximately 53% of the sites recorded values lower than 100 mW m-2, suggesting large areas of seawater recharge and advective extraction of lithospheric heat. High heat flow values were concentrated around relatively small "hot spots." Integration of heat flow values over the Raven survey area gives an estimate of conductive heat output of 0.3 MW, an average of 0.95 W m-2, over the survey area. Fluid circulation cell dimensions and scaling equations allow calculation of a Rayleigh number of approximately 700 in Layer 2A. The close proximity of high and low heat flow areas, coupled with previous estimates of surficial seafloor permeability, argues for the presence of small-scale hydrothermal fluid circulation cells within the high-porosity uppermost crustal layer of the axial seafloor.

  7. Submarine fissure eruptions and hydrothermal vents on the southern Juan de Fuca Ridge: preliminary observations from the submersible Alvin.

    USGS Publications Warehouse

    Normark, W.R.

    1986-01-01

    The submersible Alvin was used to investigate 3 active hydrothermal discharge sites along the S Juan de Fuca Ridge in September 1984. The hydrothermal zones occur within a 10-30m-deep, 30-50m-wide cleft marking the center of the axial valley. This cleft is the eruptive locus for the axial valley. The hydrothermal vents coincide with the main eruptive vents along the cleft. Each hydrothermal zone has multiple discharge sites extending as much as 500m along the cleft. Sulfide deposits occur as clusters (15-100m2 area) of small chimneys (= or <2m high) and as individual and clustered fields of large, branched chimneys (= or <10m high). Recovered sulfide samples are predominantly the tops of chimneys and spires and typically contain more than 80% sphalerite and wurtzite with minor pyrrhotite, pyrite, marcasite, isocubanite, chalcopyrite, anhydrite, anhydrite, and amorphous silica. The associated hydrothermal fluids have the highest chlorinity of any reported to date.-Authors

  8. Microbial diversity of a sulfide black smoker in main endeavour hydrothermal vent field, Juan de Fuca Ridge.

    PubMed

    Zhou, Huaiyang; Li, Jiangtao; Peng, Xiaotong; Meng, Jun; Wang, Fengping; Ai, Yuncan

    2009-06-01

    Submarine hydrothermal vents are among the least-understood habitats on Earth but have been the intense focus of research in the past 30 years. An active hydrothermal sulfide chimney collected from the Dudley site in the Main Endeavour vent Field (MEF) of Juan de Fuca Ridge was investigated using mineralogical and molecular approaches. Mineral analysis indicated that the chimney was composed mainly of Fe-, Zn-and Cu-rich sulfides. According to phylogenetic analysis, within the Crenarchaeota, clones of the order Desulfurococcales predominated, comprising nearly 50% of archaeal clones. Euryarchaeota were composed mainly of clones belonging to Thermococcales and deep-sea hydrothermal vent Euryarchaeota (DHVE), each of which accounted for about 20% of all clones. Thermophilic or hyperthermophilic physiologies were common to the predominant archaeal groups. More than half of bacterial clones belonged to epsilon-Proteobacteria, which confirmed their prevalence in hydrothermal vent environments. Clones of Proteobacteria (gamma-, delta-, beta-), Cytophaga-Flavobacterium-Bacteroides (CFB) and Deinococcus-Thermus occurred as well. It was remarkable that methanogens and methanotrophs were not detected in our 16S rRNA gene library. Our results indicated that sulfur-related metabolism, which included sulfur-reducing activity carried out by thermophilic archaea and sulfur-oxidizing by mesophilic bacteria, was common and crucial to the vent ecosystem in Dudley hydrothermal site. PMID:19557339

  9. Time-series measurement of hydrothermal heat flux at the Grotto mound, Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Xu, Guangyu; Jackson, Darrell R.; Bemis, Karen G.; Rona, Peter A.

    2014-10-01

    Continuous time-series observations are key to understanding the temporal evolution of a seafloor hydrothermal system and its interplay with thermal and chemical processes in the ocean and Earth interior. In this paper, we present a 26-month time series of the heat flux driving a hydrothermal plume on the Endeavour Segment of the Juan de Fuca Ridge obtained using the Cabled Observatory Vent Imaging Sonar (COVIS). Since 2010, COVIS has been connected to the North East Pacific Time-series Underwater Networked Experiment (NEPTUNE) observatory that provides power and real-time data transmission. The heat flux time series has a mean value of 18.10 MW and a standard deviation of 6.44 MW. The time series has no significant global trend, suggesting the hydrothermal heat source remained steady during the observation period. The steadiness of the hydrothermal heat source coincides with reduced seismic activity at Endeavour observed in the seismic data recorded by an ocean bottom seismometer from 2011 to 2013. Furthermore, first-order estimation of heat flux based on the temperature measurements made by the Benthic and Resistivity Sensors (BARS) at a neighboring vent also supports the steadiness of the hydrothermal heat source.

  10. Window into Sediment-Buried Basement Biosphere: Fluid Sampling from CORK Observatory Seafloor Platforms, Juan de Fuca Ridge Flanks

    NASA Astrophysics Data System (ADS)

    Cowen, J. P.; Lin, H.; Rappe, M.; Jungbluth, S.; Glazer, B. T.; Matzinger, M.; Amend, J. P.; Boettger, J.

    2010-12-01

    Studies of the deep basement biosphere are technologically challenging, requiring complementary approaches to provide sufficient access to allow precision analyses and experimentation. Our NSF-funded ‘Microbial Observatory’ has focused on IODP Circulation Obviating Retrofit Kit (CORK) observatories to obtain pristine samples of fluids from sediment-buried basement environments. We have developed instruments and samplers to interface with CORK fluid delivery lines, including a ROV/HOV-borne Mobile Pumping System and autonomous (e.g., GeoMICROBE) instrument sensor/sampler systems. These systems are providing high quality (e.g., depleted Mg++, <6 mM) samples of basement fluids from 3.5 mA old upper basement, on the flanks of the Juan de Fuca Ridge, for geochemical and microbial studies. Relative to bottom seawater, these fluids are also depleted in O2, SO42-, PO43-, NO3- and NO2-, while enriched in NH4+, H2S, Mn and Fe. In situ voltammetric analyses obtained during sample collection, revealed the presence of micromolar levels of sulfide (0.5 µm) in the fluids. Dissolved organic carbon in basement fluids is about half that of local bottom seawater, low molecular weight organic acids are below detection limits, while total amino acids are also low in concentration, but the relative abundance of specific amino acids varies from that of bottom seawater. Overall, the sediment-buried basement environments appears to be organic-carbon depleted and low energy, yet still dynamic. The microbial communities from CORK 1301A (47deg 45N, 127deg 45W) in consecutive years are heterogeneous, but share common groups. Different CORKs sampled a decade apart share major lineages, consistent with hydrogeologic connectivity. Samples collected from a new CORK installation at borehole 1026B contain a subset of members found a decade previously from an older style CORK at the same site. Communities retrieved from the CORK at 1025C (47deg 53N, 128deg 39W), in 1.4 My ridge flank basement

  11. Microbiological characterization of post-eruption “snowblower” vents at Axial Seamount, Juan de Fuca Ridge

    PubMed Central

    Meyer, Julie L.; Akerman, Nancy H.; Proskurowski, Giora; Huber, Julie A.

    2013-01-01

    Microbial processes within the subseafloor can be examined during the ephemeral and uncommonly observed phenomena known as snowblower venting. Snowblowers are characterized by the large quantity of white floc that is expelled from the seafloor following mid-ocean ridge eruptions. During these eruptions, rapidly cooling lava entrains seawater and hydrothermal fluids enriched in geochemical reactants, creating a natural bioreactor that supports a subseafloor microbial “bloom.” Previous studies hypothesized that the eruption-associated floc was made by sulfide-oxidizing bacteria; however, the microbes involved were never identified. Here we present the first molecular analysis combined with microscopy of microbial communities in snowblower vents from samples collected shortly after the 2011 eruption at Axial Seamount, an active volcano on the Juan de Fuca Ridge. We obtained fluid samples and white flocculent material from active snowblower vents as well as orange flocculent material found on top of newly formed lava flows. Both flocculent types revealed diverse cell types and particulates when examined by phase contrast and scanning electron microscopy (SEM). Distinct archaeal and bacterial communities were detected in each sample type through Illumina tag sequencing of 16S rRNA genes and through sequencing of the sulfide oxidation gene, soxB. In fluids and white floc, the dominant bacteria were sulfur-oxidizing Epsilonproteobacteria and the dominant archaea were thermophilic Methanococcales. In contrast, the dominant organisms in the orange floc were Gammaproteobacteria and Thaumarchaeota Marine Group I. In all samples, bacteria greatly outnumbered archaea. The presence of anaerobic methanogens and microaerobic Epsilonproteobacteria in snowblower communities provides evidence that these blooms are seeded by subseafloor microbes, rather than from microbes in bottom seawater. These eruptive events thus provide a unique opportunity to observe subseafloor microbial

  12. Seismic reflection images of a near-axis melt sill within the lower crust at the Juan de Fuca ridge.

    PubMed

    Canales, J Pablo; Nedimović, Mladen R; Kent, Graham M; Carbotte, Suzanne M; Detrick, Robert S

    2009-07-01

    The oceanic crust extends over two-thirds of the Earth's solid surface, and is generated along mid-ocean ridges from melts derived from the upwelling mantle. The upper and middle crust are constructed by dyking and sea-floor eruptions originating from magma accumulated in mid-crustal lenses at the spreading axis, but the style of accretion of the lower oceanic crust is actively debated. Models based on geological and petrological data from ophiolites propose that the lower oceanic crust is accreted from melt sills intruded at multiple levels between the Moho transition zone (MTZ) and the mid-crustal lens, consistent with geophysical studies that suggest the presence of melt within the lower crust. However, seismic images of molten sills within the lower crust have been elusive. Until now, only seismic reflections from mid-crustal melt lenses and sills within the MTZ have been described, suggesting that melt is efficiently transported through the lower crust. Here we report deep crustal seismic reflections off the southern Juan de Fuca ridge that we interpret as originating from a molten sill at present accreting the lower oceanic crust. The sill sits 5-6 km beneath the sea floor and 850-900 m above the MTZ, and is located 1.4-3.2 km off the spreading axis. Our results provide evidence for the existence of low-permeability barriers to melt migration within the lower section of modern oceanic crust forming at intermediate-to-fast spreading rates, as inferred from ophiolite studies. PMID:19571883

  13. Evolution of seismic layer 2B across the Juan de Fuca Ridge from hydrophone streamer 2-D traveltime tomography

    NASA Astrophysics Data System (ADS)

    Newman, Kori R.; Nedimović, Mladen R.; Canales, J. Pablo; Carbotte, Suzanne M.

    2011-05-01

    How oceanic crust evolves has important implications for understanding both subduction earthquake hazards and energy and mass exchange between the Earth's interior and the oceans. Although considerable work has been done characterizing the evolution of seismic layer 2A, there has been little analysis of the processes that affect layer 2B after formation. Here we present high-resolution 2-D tomographic models of seismic layer 2B along ˜300 km long multichannel seismic transects crossing the Endeavour, Northern Symmetric, and Cleft segments of the Juan de Fuca Ridge. These models show that seismic layer 2B evolves rapidly following a different course than layer 2A. The upper layer 2B velocities increase on average by 0.8 km/s and reach a generally constant velocity of 5.2 ± 0.3 km/s within the first 0.5 Myr after crustal formation. This suggests that the strongest impact on layer 2B evolution may be that of mineral precipitation due to "active" hydrothermal circulation centered about the ridge crest and driven by the heat from the axial magma chamber. Variations in upper layer 2B velocity with age at time scales ≥0.5 Ma show correlation about the ridge axis indicating that in the long term, crustal accretion processes affect both sides of the ridge axis in a similar way. Below the 0.5 Ma threshold, differences in 2B velocity are likely imprinted during crustal formation or early crustal evolution. Layer 2B velocities at propagator wakes (5.0 ± 0.2 km/s), where enhanced faulting and cracking are expected, and at areas that coincide with extensional or transtensional faulting are on average slightly slower than in normal mature upper layer 2B. Analysis of the layer 2B velocities from areas where the hydrothermal patterns are known shows that the locations of current and paleohydrothermal discharge and recharge zones are marked by reduced and increased upper layer 2B velocities, respectively. Additionally, the distance between present up-flow and down-flow zones is

  14. Shear wave splitting observations across the Juan de Fuca plate system: Ridge- to-trench constraints on mantle flow from 2 years of Cascadia Initiative OBS data

    NASA Astrophysics Data System (ADS)

    Bodmer, M.; Toomey, D. R.; Hooft, E. E. E.

    2014-12-01

    We present SKS splitting measurements for the first two years of data collected by the Cascadia Initiative (CI) amphibious array. Our analysis includes observations from over 100 ocean bottom seismometers (OBS), as well as 31 onshore stations, and spans both the Juan de Fuca and Gorda plates. The CI dataset is unique in that it includes several regions that can distinctly influence anisotropic fabric development such as: the upwelling mantle beneath the Juan de Fuca and Gorda ridges, the young evolving oceanic lithosphere of the plate interior, the Blanco transform fault, and the Cascadia subduction zone. For the first time, we are able to analyze these regions with a single dataset, and using a common methodology. Splitting measurements are routinely done on land sites, but have been completed on relatively few OBS stations. This is largely due to the low signal to noise present in OBS data, which can obscure the splitting results. To address that nearly all the OBS data exceeds the global high noise limit at the frequencies used for splitting, we implement a rigorous quality control scheme. Our method specifically takes into account the response of common splitting methods to high noise data and addresses known issues such as cycle skipping, false minima, low transverse energy, and near-null measurements. Individual measurements are filtered at 0.03-0.1 Hz, manually checked for quality, and stacked. Preliminary results show trench perpendicular onshore measurements consistent with previous studies. Oceanic measurements in the plate interior show a coherent fast axis roughly aligned with absolute plate motion. Several measurements near the ridge and trench appear to be rotated in the ridge and trench parallel directions. Continuing work will integrate splitting measurements from the final two years of the CI with these findings, which will be used to characterize the ridge-to-trench mantle flow across the Juan de Fuca plate system.

  15. Elastic Full Waveform Inversion reveals the fine-scale structure of Axial Volcano on the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Arnulf, A. F.; Harding, A. J.; Kent, G.

    2012-12-01

    Axial volcano (sometimes referred to as "Axial seamount" or "Axial") is located at 46N, 130W at the intersection of the Juan de Fuca Ridge and the Cobb-Eickelberg seamount chain. It is the most recent eruptive center of the Cobb hotspot, which last erupted in 2011. The volcano rises ~700 m above the adjacent ridge axis and its summit features a U-shaped caldera open to the southeast, which hosts an active hydrothermal field and very young lava flows. Located at the junction of a mid-ocean ridge and a volcanic hotspot, Axial volcano is atypical and its internal structure remains poorly understood. Here, we present results from an elastic full waveform inversion (FWI) along multiple seismic lines that span the whole volcano. We have used a multi-stage FWI, inverting successively wide-angle reflections and refractions arrivals from downward extrapolated streamer data, then windowed short offset reflections from the underlying magma chamber. Our final models show fine scale velocity structures with spatial resolutions of tens of meters. Our results indicate that Layer 2A thickness is extremely heterogeneous (350-900 m) within the volcano with abrupt vertical throws of >300 m beneath the caldera walls that suggests the tectonic thinning of a geologically defined Layer 2A. Interestingly, Layer 2A appears to be extremely thin beneath the active hydrothermal field and the most recent lava flows, on the southeast end of the caldera, where sheeted dikes might lay <100 m beneath the seafloor. On the other hand, the nearby caldera center is filled by successive lava sequences (~450 m thick) that further appear to be micro faulted, suggesting a constant interplay between magmatic and tectonic processes. Surface velocities show limited variation over the whole volcano and may suggest relative recent formation, considering the rapid increase in layer 2A velocity with age. Finally, our velocity structures image a wide and complex magma chamber system beneath the volcano at depth

  16. Evidence of active ground deformation on the mid-ocean ridge: Axial seamount, Juan de Fuca Ridge, April-June 1988

    SciTech Connect

    Fox, C.G. )

    1990-08-10

    Since September 1987 a precision bottom pressure recorder (BPR) has been deployed within the summit caldera of Axial seamount. The instrument is capable of measuring pressure of 1 mbar resolution and recording these measurements at 64 samples per hour for up to 15 months. Any significant change in the pressure record should indicate a change of depth associated with vertical ground movement, commonly indicative of active inflation or deflation of underlying magma bodies. Results from the first 9 months of the BPR deployment revealed a significant change in pressure, which is interpreted to represent a 15-cm subsidence of the caldera floor during two 2- to 3-week periods in April-June 1988. Also during these periods, an anomalous decline in temperature at the site was recorded that is correlated with an apparent increase in current velocity at the Axial Seamount Hydrothermal Emissions Study (ASHES) vent field, suggesting vigorous advection of cold water into the caldera. Concurrent oceanographic data from Geosat and from current meter arrays do not indicate any large-scale oceanographic phenomena capable of generating these simultaneous events. One mechanism to explain simultaneous ground subsidence and temperature decline at the caldera center and increased bottom current at the caldera margin is the generation of a buoyant parcel of heated water in response to the intrusion or the eruption of magma associated with volcanic deflation. Similar volcanic events also may have generated large midwater plumes that have been described previously along the southern Juan de Fuca Ridge.

  17. Space-time relations of hydrothermal sulfide-sulfate-silica deposits at the northern Cleft Segment, Juan de Fuca Ridge

    SciTech Connect

    Koski, R.A.; Smith, V.K. ); Embley, R.W. ); Jonasson, I.R. ); Kadko, D.C. . Rosenstiel School of Marine and Atmospheric Science)

    1993-04-01

    Submersible investigations along the northern Cleft Segment of the Juan de Fuca Ridge indicate that a newly erupted sheet flow and two recent megaplume events are spatially related to a NNE-trending fissure system that is now the locus for active hydrothermal venting and deposition of massive sulfide mounds and chimneys. Samples from active high-temperature vent sites located east and north of the sheet flow terrain include zoned Cu-sulfide-rich chimneys (Type 1), bulbous anhydrite-rich chimneys (Type 2), and columnar Zn-sulfide-rich chimneys (Type 3). Type 1 chimneys with large open channelways result from the focused discharge of fluid at temperatures between 310 and 328 C from the Monolith sulfide mound. Type 2 chimneys are constructed on the Monolith and Fountain mounds where discharge of fluid at temperatures between 293 and 315 C is diffuse and sluggish. Type 3 chimneys, characterized by twisting narrow channelways, are deposited from focused and relatively low-temperature fluid discharging directly from basalt substrate. Inactive sulfide chimneys (Type 4) located within 100 m of the fissure system have bulk compositions, mineral assemblages, colloform and bacteroidal textures, and oxygen isotope characteristics consistent with low-temperature (< 250 C ) deposition from less robust vents. Field relations and [sup 210]Pb ages (> 100 years) indicate that the Type 4 chimneys formed prior to the sheet flow eruption. The sulfide mounds and Type 1 and Type 2 chimneys at the Monolith and Fountain vents, however, are an expression of the same magmatic event that caused the sheet flow eruption and megaplume events.

  18. Mineralogical studies of sulfide samples and volatile concentrations of basalt glasses from the southern Juan de Fuca Ridge.

    PubMed

    Brett, R; Evans, H T; Gibson, E K; Hedenquist, J W; Wandless, M V; Sommer, M A

    1987-10-10

    Sulfide samples obtained from the U.S. Geological Survey's DSRV Alvin dives on the southern Juan de Fuca Ridge closely resemble those from the same area described by Koski et al. (1984). Major minerals include sphalerite, wurtzite, pyrite, marcasite, isocubanite, anhydrite, and chalcopyrite. Equilibrium, if attained at all, during deposition of most sulfides was a transient event over a few tens of micrometers at most and was perturbed by rapid temperature and compositional changes of the circulating fluid. Two new minerals were found: one, a hydrated Zn, Fe hydroxy-chlorosulfate, and the other, a (Mn, Mg, Fe) hydroxide or hydroxy-hydrate. Both were formed at relatively low temperatures. Lizardite, starkeyite, and anatase were found for the first time in such an environment. Sulfide geothermometry involving the system Cu-Fe-S indicates a vent temperature of <328 degrees C for one sample. Fluid inclusion studies on crystals from the same vicinity of the same sample give pressure-corrected homogenization temperatures of 268 degrees and 285 degrees C. Ice-melting temperatures on inclusions from the same sample are about -2.8 degrees C, indicating that the equivalent salinity of the trapped fluid is about 50% greater than that of seawater. Volatile concentrations from vesicle-free basalt glass from the vent field are about 0.013 wt% CO2 and 0.16 wt% H2O, CO2 contents in these samples yield an entrapment depth of 2200 m of seawater, which is the depth from which the samples were collected. PMID:11542121

  19. Linkages between mineralogy, fluid chemistry, and microbial communities within hydrothermal chimneys from the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Lin, T. J.; Ver Eecke, H. C.; Breves, E. A.; Dyar, M. D.; Jamieson, J. W.; Hannington, M. D.; Dahle, H.; Bishop, J. L.; Lane, M. D.; Butterfield, D. A.; Kelley, D. S.; Lilley, M. D.; Baross, J. A.; Holden, J. F.

    2016-02-01

    Rock and fluid samples were collected from three hydrothermal chimneys at the Endeavour Segment, Juan de Fuca Ridge to evaluate linkages among mineralogy, fluid chemistry, and microbial community composition within the chimneys. Mössbauer, midinfrared thermal emission, and visible-near infrared spectroscopies were utilized for the first time to characterize vent mineralogy, in addition to thin-section petrography, X-ray diffraction, and elemental analyses. A 282°C venting chimney from the Bastille edifice was composed primarily of sulfide minerals such as chalcopyrite, marcasite, and sphalerite. In contrast, samples from a 300°C venting chimney from the Dante edifice and a 321°C venting chimney from the Hot Harold edifice contained a high abundance of the sulfate mineral anhydrite. Geochemical modeling of mixed vent fluids suggested the oxic-anoxic transition zone was above 100°C at all three vents, and that the thermodynamic energy available for autotrophic microbial redox reactions favored aerobic sulfide and methane oxidation. As predicted, microbes within the Dante and Hot Harold chimneys were most closely related to mesophilic and thermophilic aerobes of the Betaproteobacteria and Gammaproteobacteria and sulfide-oxidizing autotrophic Epsilonproteobacteria. However, most of the microbes within the Bastille chimney were most closely related to mesophilic and thermophilic anaerobes of the Deltaproteobacteria, especially sulfate reducers, and anaerobic hyperthermophilic archaea. The predominance of anaerobes in the Bastille chimney indicated that other environmental factors promote anoxic conditions. Possibilities include the maturity or fluid flow characteristics of the chimney, abiotic Fe2+ and S2- oxidation in the vent fluids, or O2 depletion by aerobic respiration on the chimney outer wall.

  20. GeoChip-based analysis of metabolic diversity of microbial communities at the Juan de Fuca Ridge hydrothermal vent

    PubMed Central

    Wang, Fengping; Zhou, Huaiyang; Meng, Jun; Peng, Xiaotong; Jiang, Lijing; Sun, Ping; Zhang, Chuanlun; Van Nostrand, Joy D.; Deng, Ye; He, Zhili; Wu, Liyou; Zhou, Jizhong; Xiao, Xiang

    2009-01-01

    Deep-sea hydrothermal vents are one of the most unique and fascinating ecosystems on Earth. Although phylogenetic diversity of vent communities has been extensively examined, their physiological diversity is poorly understood. In this study, a GeoChip-based, high-throughput metagenomics technology revealed dramatic differences in microbial metabolic functions in a newly grown protochimney (inner section, Proto-I; outer section, Proto-O) and the outer section of a mature chimney (4143-1) at the Juan de Fuca Ridge. Very limited numbers of functional genes were detected in Proto-I (113 genes), whereas much higher numbers of genes were detected in Proto-O (504 genes) and 4143-1 (5,414 genes). Microbial functional genes/populations in Proto-O and Proto-I were substantially different (around 1% common genes), suggesting a rapid change in the microbial community composition during the growth of the chimney. Previously retrieved cbbL and cbbM genes involved in the Calvin Benson Bassham (CBB) cycle from deep-sea hydrothermal vents were predominant in Proto-O and 4143-1, whereas photosynthetic green-like cbbL genes were the major components in Proto-I. In addition, genes involved in methanogenesis, aerobic and anaerobic methane oxidation (e.g., ANME1 and ANME2), nitrification, denitrification, sulfate reduction, degradation of complex carbon substrates, and metal resistance were also detected. Clone libraries supported the GeoChip results but were less effective than the microarray in delineating microbial populations of low biomass. Overall, these results suggest that the hydrothermal microbial communities are metabolically and physiologically highly diverse, and the communities appear to be undergoing rapid dynamic succession and adaptation in response to the steep temperature and chemical gradients across the chimney. PMID:19273854

  1. Heat flux measured acoustically at Grotto Vent, a hydrothermal vent cluster on the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Xu, G.; Jackson, D. R.; Bemis, K. G.; Rona, P. A.

    2013-12-01

    Over the past several decades, quantifying the heat output has been a unanimous focus of studies at hydrothermal vent fields discovered around the global ocean. Despite their importance, direct measurements of hydrothermal heat flux are very limited due to the remoteness of most vent sites and the complexity of hydrothermal venting. Moreover, almost all the heat flux measurements made to date are snapshots and provide little information on the temporal variation that is expected from the dynamic nature of a hydrothermal system. The Cabled Observatory Vent Imaging Sonar (COVIS, https://sites.google.com/a/uw.edu/covis/) is currently connected to the Endeavour node of the NEPTUNE Canada observatory network (http://www.neptunecanada.ca) to monitor the hydrothermal plumes issuing from a vent cluster (Grotto) on the Endeavour Segment of the Juan de Fuca Ridge. COVIS is acquiring a long-term (20-months to date) time series of the vertical flow rate and volume flux of the hydrothermal plume above Grotto through the Doppler analysis of the acoustic backscatter data (Xu et al., 2013). We then estimate the plume heat flux from vertical flow rate and volume flux using our newly developed inverse method. In this presentation, we will briefly summarize the derivation of the inverse method and present the heat-flux time series obtained consequently with uncertainty quantification. In addition, we compare our heat-flux estimates with the one estimated from the plume in-situ temperatures measured using a Remotely Operative Vehicle (ROV) in 2012. Such comparison sheds light on the uncertainty of our heat flux estimation. Xu, G., Jackson, D., Bemis, K., and Rona, P., 2013, Observations of the volume flux of a seafloor hydrothermal plume using an acoustic imaging sonar, Geochemistry, Geophysics Geosystems, 2013 (in press).

  2. High-resolution near-bottom vector magnetic anomalies over Raven Hydrothermal Field, Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Tivey, Maurice A.; Johnson, H. Paul; Salmi, Marie S.; Hutnak, Michael

    2014-10-01

    High-resolution, near-bottom vector magnetic data were collected by remotely operated vehicle Jason over the Raven hydrothermal vent field (47°57.3'N 129°5.75'W) located north of Main Endeavour vent field on the Endeavour segment of the Juan de Fuca Ridge. The survey was part of a comprehensive heat flow study of the Raven site using innovative thermal blanket technology to map the heat flux and crustal fluid pathways around a solitary hydrothermal vent field. Raven hydrothermal activity is presently located along the western axial valley wall, while additional inactive hydrothermal deposits are found to the NW on the upper rift valley wall. Magnetic inversion results show discrete areas of reduced magnetization associated with both active and inactive hydrothermal vent deposits that also show high conductive heat flow. Higher spatial variability in the heat flow patterns compared to the magnetization is consistent with the heat flow reflecting the currently active but ephemeral thermal environment of fluid flow, while crustal magnetization is representative of the static time-averaged effect of hydrothermal alteration. A general NW to SE trend in reduced magnetization across the Raven area correlates closely with the distribution of hydrothermal deposits and heat flux patterns and suggests that the fluid circulation system at depth is likely controlled by local crustal structure and magma chamber geometry. Magnetic gradient tensor components computed from vector magnetic data improve the resolution of the magnetic anomaly source and indicate that the hydrothermally altered zone directly beneath the Raven site is approximately 15 × 106 m3 in volume.

  3. Chemical Speciation and Oxidation Kinetics of Iron and Sulfur in Subseafloor Basement Fluids on the Juan de Fuca Ridge Flanks

    NASA Astrophysics Data System (ADS)

    Glazer, B. T.; Matzinger, M.; Cowen, J. P.

    2011-12-01

    Redox reactive chemical species circulate throughout the upper oceanic crust, and are involved in a variety of abiotic and microbially-mediated reactions. Through exchange with bottom seawater, fluids circulating in the upper basement have the potential to influence scales ranging from global-scale biogeochemical cycling to micro-scale microbe-mineral interactions. Understanding fundamental chemical speciation, distribution, bioavailability, and rates of transformations for key chemical redox species is crucial to understanding processes in the subsurface. In-situ electrochemical analyses were conducted in real-time at CORK (Circulation Obviation Retrofit Kit) observatories affixed to Integrated Ocean Drilling Program (IODP) boreholes in Cascadia Basin on the Juan de Fuca Ridge Flanks. Voltammetric electrodes were mounted into a flow cell to allow for simultaneous detection of redox species (O2, H_{2}O2, HS^{-}, S(0), Sx^{2-}, S2O_{3}2-, S_{4}O6^{2-}, Fe(II), Fe(III), FeS$_{(aq)}) concurrent to sample filtering or fluid collection. During real-time voltammetric scanning, qualitative assessment of the integrity of fluids delivered through the Fluid Delivery Lines could be made, allowing for comparisons between CORK sites and various sampling strategies. Newly installed CORKs at IODP sites 1362A and 1362B are producing the highest-integrity basement fluids collected to date, deplete in oxygen (<3uM) and enriched in iron (>1uM). Here, we report results of in situ electrochemical measurements at multiple borehole observatories, including the newly installed 1362A & 1362B sites, and present results of speciation analyses and kinetics of oxidation for iron and sulfur in discrete samples.

  4. Complete genome sequence of the hyperthermophilic archaeon Pyrococcus sp. strain ST04, isolated from a deep-sea hydrothermal sulfide chimney on the Juan de Fuca Ridge.

    PubMed

    Jung, Jong-Hyun; Lee, Ju-Hoon; Holden, James F; Seo, Dong-Ho; Shin, Hakdong; Kim, Hae-Yeong; Kim, Wooki; Ryu, Sangryeol; Park, Cheon-Seok

    2012-08-01

    Pyrococcus sp. strain ST04 is a hyperthermophilic, anaerobic, and heterotrophic archaeon isolated from a deep-sea hydrothermal sulfide chimney on the Endeavour Segment of the Juan de Fuca Ridge in the northeastern Pacific Ocean. To further understand the distinct characteristics of this archaeon at the genome level (polysaccharide utilization at high temperature and ATP generation by a Na(+) gradient), the genome of strain ST04 was completely sequenced and analyzed. Here, we present the complete genome sequence analysis results of Pyrococcus sp. ST04 and report the major findings from the genome annotation, with a focus on its saccharolytic and metabolite production potential. PMID:22843576

  5. Complete Genome Sequence of the Hyperthermophilic Archaeon Pyrococcus sp. Strain ST04, Isolated from a Deep-Sea Hydrothermal Sulfide Chimney on the Juan de Fuca Ridge

    PubMed Central

    Jung, Jong-Hyun; Lee, Ju-Hoon; Holden, James F.; Seo, Dong-Ho; Shin, Hakdong; Kim, Hae-Yeong; Kim, Wooki; Ryu, Sangryeol

    2012-01-01

    Pyrococcus sp. strain ST04 is a hyperthermophilic, anaerobic, and heterotrophic archaeon isolated from a deep-sea hydrothermal sulfide chimney on the Endeavour Segment of the Juan de Fuca Ridge in the northeastern Pacific Ocean. To further understand the distinct characteristics of this archaeon at the genome level (polysaccharide utilization at high temperature and ATP generation by a Na+ gradient), the genome of strain ST04 was completely sequenced and analyzed. Here, we present the complete genome sequence analysis results of Pyrococcus sp. ST04 and report the major findings from the genome annotation, with a focus on its saccharolytic and metabolite production potential. PMID:22843576

  6. Linking Microearthquakes and Seismic Tomography on the Endeavour Segment of the Juan de Fuca Ridge: Implications for Hydrothermal Circulation

    NASA Astrophysics Data System (ADS)

    Wilcock, W. S.; Weekly, R. T.; Hooft, E. E.; Toomey, D. R.; Kim, E.

    2013-12-01

    We report on a remarkable correlation between the patterns of microearthquakes and three-dimensional upper crustal velocity anomalies on the Endeavour segment of the Juan de Fuca Ridge. Microearthquakes were monitored from 2003-2006 by a small seismic network deployed on the central part of the segment. The velocity model was obtained from a tomography experiment comprising over 5500 shots from a large airgun array that were recorded by ocean bottom seismometers deployed at 64 sites along the Endeavour segment and the adjacent overlapping spreading centers (OSCs). On the segment scale, upper crustal velocities are low in the OSCs indicating that the crust is highly fractured. These low velocities persist off-axis and record the history of ridge propagation. In 2005, two swarm sequences that were interpreted in terms of magmatic intrusions on the limbs of the Endeavour-West Valley OSC were accompanied by extensive seismicity within the overlap basin. Throughout the microearthquake experiment earthquakes were concentrated in a region surrounding the southern tip of the West Valley propagator that coincides closely with the southern limit of the low velocities imaged around the OSC. Beneath the hydrothermal vent fields in the center of the Endeavour segment, the earthquakes were mostly located in a 500-m-thick band immediately above the axial magma chamber. There was a close correlation between the rates of seismicity beneath each vent field and their thermal output. The highest rates of seismicity were observed beneath the High Rise and Main Endeavour fields that each have power outputs of several hundred megawatts. Seismic velocities are generally high beneath the vent fields relative to velocities along the ridge axis immediately to the north and south. However, the High Rise and Main Endeavour fields are underlain by a low velocity region at 2 km depth that coincides with the seismically active region. This is consistent with a region of increased fracturing and

  7. Geologic setting of massive sulfide deposits and hydrothermal vents along the southern Juan de Fuca Ridge

    SciTech Connect

    Normark, W.R.; Morton, J.L.; Delaney, J.R.

    1982-01-01

    This report incorporates data from two cruises of the USGS vessel SP LEE: (1) L12-80-WF from 29 October to 13 November 1980, and (2) L11-81-WF from 4 to 15 September 1981. The 1980 cruise occurred long after the optimum weather window for this region. The natural results was that no photographic or sample stations could be attempted during nearly continuous gale- and storm-force winds, which twice forced the vessel to depart the work area for safety. A detailed bathymetric survey of a 35-km segment of the ridge axial zone was completed nonetheless, and the bathymetric map compiled from this survey was used as the base for our second cruise in 1981. The second visit to the area was blessed with fair weather, and most of the cruise effort was devoted to photography and sampling, including dredging and hydrocasts in the axial valley segment, which is the central part of the area surveyed in 1980.

  8. Modeling mid-ocean ridge hydrothermal response to earthquakes, tides, and ocean currents: a case study at the Grotto mound, Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Xu, G.; Bemis, K. G.

    2014-12-01

    Seafloor hydrothermal systems feature intricate interconnections among oceanic, geological, hydrothermal, and biological processes. The advent of the NEPTUNE observatory operated by Ocean Networks Canada at the Endeavour Segment, Juan de Fuca Ridge enables scientists to study these interconnections through multidisciplinary, continuous, real-time observations. The multidisciplinary observatory instruments deployed at the Grotto Mound, a major study site of the NEPTUNE observatory, makes it a perfect place to study the response of a seafloor hydrothermal system to geological and oceanic processes. In this study, we use the multidisciplinary datasets recorded by the NEPTUNE Observatory instruments as observational tools to demonstrate two different aspects of the response of hydrothermal activity at the Grotto Mound to geological and oceanic processes. First, we investigate a recent increase in venting temperature and heat flux at Grotto observed by the Benthic and Resistivity Sensors (BARS) and the Cabled Observatory Vent Imaging Sonar (COVIS) respectively. This event started in Mar 2014 and is still evolving by the time of writing this abstract. An initial interpretation in light of the seismic data recorded by a neighboring ocean bottom seismometer on the NEPTUNE observatory suggests the temperature and heat flux increase is probably triggered by local seismic activities. Comparison of the observations with the results of a 1-D mathematical model simulation of hydrothermal sub-seafloor circulation elucidates the potential mechanisms underlying hydrothermal response to local earthquakes. Second, we observe significant tidal oscillations in the venting temperature time series recorded by BARS and the acoustic imaging of hydrothermal plumes by COVIS, which is evidence for hydrothermal response to ocean tides and currents. We interpret the tidal oscillations of venting temperature as a result of tidal loading on a poroelastic medium. We then invoke poroelastic

  9. Large Lava Pond Complex on the Juan de Fuca Ridge: an Effusive, Energetic Eruption that Drained Away

    NASA Astrophysics Data System (ADS)

    Paduan, J. B.; Clague, D. A.; Davis, A. S.; Chadwick, W.; Cousens, B. L.; Embley, R. W.

    2005-12-01

    We explored an unusually large, deep, drained lava lake complex on the south rift of Axial Seamount on the Juan de Fuca Ridge during three dives with the ROV Tiburon in August 2005. The complex of five large ponds, first identified from EM300 multibeam bathymetry, is 5 km long and more than 1 km wide. The ponds are separated from one another by narrow levees that rise about 90 meters above the pond floors. The levees are all about the same depth, which suggests that the ponds formed at the same time. The volume of the lake, prior to draining, was 0.2-0.4 km3, making it the largest lava lake known along the ridge system. The outer slopes of the pond levees are constructed of elongate pillows that flowed down the steep slopes. The rims are narrow, level plateaus of lobate flows with many collapses. The inner walls are vertical cliffs, overhanging in places, with horizontal shelves from the top of the levees down to the floors of the ponds. Left like bathtub rings, these shelves mark former surfaces of the lava pond as it drained away while the lava was still molten. In many places, this veneer has collapsed to reveal truncated lobate flows and pillows. The floor of one small pond was entirely talus blocks. However, the floors of the other, larger ponds had little talus and, instead, were vast expanses of thin broken crusts, lobate flows, and very fluid, chaotic, folded and jumbled sheet flows. The lavas from each pond have abundant large feldspar and rarer olivine crystals, suggesting that all were from the same eruption. This eruption apparently began with sheet flows whose advance was limited by topography. It then ponded and built up the levees that were left when the lava drained away. On the floor of one pond we found a deposit several meters tall that was delicate and difficult to sample, and turned out to be agglutinated spatter. Limu o Pele (lava bubble wall fragments) was abundant in all the sediment samples in and around the ponds. The spatter and limu

  10. Temporal Changes in the Strength of Tidal Triggering Linked to Volcanic Swarms on the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Wilcock, W. S.; Weekly, R. T.; Hooft, E. E.; Toomey, D. R.

    2010-12-01

    A number of studies on mid-ocean ridges have documented a clear tidal triggering signal for volcanic/hydrothermal microearthquakes with earthquake rates increasing during intervals when the volumetric tidal stresses are least compressive. Tidal triggering has been demonstrated for the Endeavour segment in 1995, Axial Volcano in 1994, and the East Pacific Rise near 9°50’N in 2003-4. The results from the East Pacific Rise show a particularly strong tidal triggering signal that was interpreted as indicating that the crust was critically stressed in the lead up to a volcanic eruption in 2005-6. Observations in several subduction zones also show an increasing tidal triggering signal prior to large earthquakes and no clear evidence for triggering immediately afterwards. We present results from a tidal triggering study on the Endeavour segment of the Juan de Fuca ridge using a three-year catalog of seismicity for a local network deployed around the vent fields from 2003-2006. The catalog spans two complex regional swarms in January and February 2005 that we interpret as non-eruptive volcanic events on the southern extension of the West Valley propagating ridge and the northern Endeavour segment, respectively. These swarms were followed by a substantial drop in seismicity rates along the entire Endeavour segment and by a drop in b-values in the areas of the swarms. The swarms appear to mark the end of a 6-year spreading event that began with a swarm in 1999 and cumulatively ruptured the whole Endeavour segment. We analyze both the tidal phase and height at the times of earthquakes for triggering. Preliminary results show that prior to the swarms there is a strong triggering signal. For example, for earthquakes near the vent fields the rates of seismicity during times when the tidal phase is closer to low tide than high tide is 50% higher than when the phase is closer to high tide. The rate of earthquakes is 130% higher when tide heights are in the lowest tenth

  11. Mechanisms of Mg-phyllosilicate formation in a hydrothermal system at a sedimented ridge (Middle Valley, Juan de Fuca)

    NASA Astrophysics Data System (ADS)

    Buatier, M. D.; Früh-Green, Gretchen L.; Karpoff, A. M.

    1995-11-01

    We present results of a detailed mineralogical and geochemical study of the progressive hydrothermal alteration of clastic sediments recovered at ODP Site 858 in an area of active hydrothermal venting at the sedimented, axial rift valley of Middle Valley (northern Juan de Fuca Ridge). These results allow a characterization of newly formed phyllosilicates and provide constraints on the mechanisms of clay formation and controls of mineral reactions on the chemical and isotopic composition of hydrothermal fluids. Hydrothermal alteration at Site 858 is characterized by a progressive change in phyllosilicate assemblages with depth. In the immediate vent area, at Hole 858B, detrital layers are intercalated with pure hydrothermal precipitates at the top of the section, with a predominance of hydrothermal phases at depth. Sequentially downhole in Hole 858B, the clay fraction of the pure hydrothermal layers changes from smectite to corrensite to swelling chlorite and finally to chlorite. In three pure hydrothermal layers in the deepest part of Hole 858B, the clay minerals coexist with neoformed quartz. Neoformed and detrital components are clearly distinguished on the basis of morphology, as seen by SEM and TEM, and by their chemical and stable isotope compositions. Corrensite is characterized by a 24 Å stacking sequence and high Si- and Mg-contents, with Fe/(Fe+Mg) ratio of ≈0.08. We propose that corrensite is a unique, possibly metastable, mineralogical phase and was precipitated directly from seawater-dominated hydrothermal fluids. Hydrothermal chlorite in Hole 858B has a stacking sequence of 14 Å with Fe/(Fe+Mg) ratios of ≈0.35. The chemistry and structure of swelling chlorite suggest that it is a corrensite/chlorite mixed-layer phase. The mineralogical zonation in Hole 858B is accompanied by a systematic decrease in δ18O, reflecting both the high thermal gradients that prevail at Site 858 and extensive sediment-fluid interaction. Precipitation of the Mg

  12. Microbially-Mediated Sulfur Oxidation in Diffuse Hydrothermal Vent Fluids at Axial Seamount, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Akerman, N. H.; Butterfield, D. A.; Huber, J. A.

    2011-12-01

    Diffusely venting hydrothermal fluids can act as a window to the subseafloor microbial environment, where chemically-reduced hydrothermal fluids mixing with oxygenated seawater in the shallow crust creates chemical disequilibria that chemotrophic microorganisms can exploit for energy gain. At Axial Seamount, an active deep-sea volcano located on the Juan de Fuca Ridge, sulfide concentrations have been measured as high as 5770 μM, and sulfide oxidation is quantitatively the most important chemical energy source for microbial metabolism. In addition, studies of microbial population structure indicate that diffuse fluids at Axial are dominated by putative sulfur- and sulfide-oxidizing bacteria belonging to the Epsilonproteobacteria. To further study this important microbial process, we surveyed diffuse vent samples from Axial over a range of temperature, pH, and sulfide concentrations for the presence and expression of sulfide-oxidizing bacteria using a functional gene approach. Dissolved oxygen concentrations decrease exponentially above 40°C and lower the potential for sulfide oxidation, so we identified six sites of different temperatures, two each in the low (< 30°C), medium (~30°C), and high temperature (30 - 50°C) range. The low temperature sites had sulfide-to-temperature ratios of 1 - 26, the medium from 15 - 29, and the high from 26 - 36. PCR primers were designed to target the sulfur oxidation gene soxB specifically from Epsilonproteobacteria and five of the six sites were positive for soxB in the DNA fraction. Bulk RNA was also extracted from the same sites to examine in situ expression of soxB. Data from these analyses, along with quantification of the soxB gene abundance and expression using quantitative PCR, are currently being carried out. Together, this data set of soxB gene diversity, expression, and abundance along with geochemical data will allow us to quantitatively determine the functional dynamics of sulfide oxidation in the subseafloor at

  13. Recent Results From Seafloor Instruments at the NeMO Observatory, Axial Volcano, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Chadwick, W. W.; Butterfield, D. A.; Embley, R. W.; Meinig, C.; Stalin, S. E.; Nooner, S. L.; Zumberge, M. A.; Fox, C. G.

    2002-12-01

    NeMO is a seafloor observatory at Axial Seamount, an active submarine volcano located on the Juan de Fuca Ridge (JdFR) in the NE Pacific. Axial Volcano was chosen for NeMO because it has the largest magma supply on the JdFR, and is therefore the best place to study volcanic events and the perturbations they cause to pre-existing hydrothermal systems. In fact, Axial volcano erupted in January 1998 and initially our field efforts were focused on mapping the new lava flows and documenting the impact of the eruption on the hydrothermal vents and biological communities. Since then, our emphasis has gradually shifted to long-term geophysical and geochemical monitoring of the volcano in anticipation of its next eruption. Recent results from seafloor monitoring instruments and recent geologic mapping will be presented, including the following: (1) NeMO Net, a state-of-the-art, two-way communication system currently deployed at Axial, which uses a moored surface buoy to link three instruments on the seafloor in near real-time to the internet. The buoy communicates with the seafloor instruments via acoustic modems and relays data to and from shore via the Orbcomm and Iridium satellite systems. The seafloor instruments include two Remote Access Samplers (RAS) located at two hydrothermal vents in the ASHES vent field, and a Bottom Pressure Recorder (BPR) located near the center of the caldera. The RAS samplers monitor temperature and chemistry at the vents and can take 48 fluid and particle samples over a year, but can also be commanded from shore to take a sample at any time in response to detected seismic or volcanic events. The BPR is monitoring vertical motion of the seafloor, looking for sudden inflation or deflation events that may signal the onset of an eruption or intrusion. Data from the three instruments is displayed on the web at http://www.pmel.noaa.gov/vents/nemo/realtime/. (2) Data from a RAS sampler that was deployed at Cloud vent in Axial caldera between 2001

  14. Crustal magnetization and the subseafloor structure of the ASHES vent field, Axial Seamount, Juan de Fuca Ridge: Implications for the investigation of hydrothermal sites

    NASA Astrophysics Data System (ADS)

    Caratori Tontini, Fabio; Crone, Timothy J.; Ronde, Cornel E. J.; Fornari, Daniel J.; Kinsey, James C.; Mittelstaedt, Eric; Tivey, Maurice

    2016-06-01

    High-resolution geophysical data have been collected using the Autonomous Underwater Vehicle (AUV) Sentry over the ASHES (Axial Seamount Hydrothermal Emission Study) high-temperature (~348°C) vent field at Axial Seamount, on the Juan de Fuca Ridge. Multiple surveys were performed on a 3-D grid at different altitudes above the seafloor, providing an unprecedented view of magnetic data resolution as a function of altitude above the seafloor. Magnetic data derived near the seafloor show that the ASHES field is characterized by a zone of low magnetization, which can be explained by hydrothermal alteration of the host volcanic rocks. Surface manifestations of hydrothermal activity at the ASHES vent field are likely controlled by a combination of local faults and fractures and different lava morphologies near the seafloor. Three-dimensional inversion of the magnetic data provides evidence of a vertical, pipe-like upflow zone of the hydrothermal fluids with a vertical extent of ~100 m.

  15. Preliminary Results from Downhole Osmotic Samplers in a Gas Tracer Injection Experiment in the Upper Oceanic Crust on the Eastern Flank of the Juan de Fuca Ridge.

    NASA Astrophysics Data System (ADS)

    de Jong, M. T.; Clark, J. F.; Neira, N. M.; Fisher, A. T.; Wheat, C. G.

    2015-12-01

    We present results from a gas tracer injection experiment in the ocean crust on the eastern flank of the Juan de Fuca Ridge, in an area of hydrothermal circulation. Sulfur hexafluoride (SF6) tracer was injected in Hole 1362B in 2010, during IODP Expedition 327. Fluid samples were subsequently collected from a borehole observatory (CORK) installed in this hole and similar CORKs in three additional holes (1026B, 1362A, and 1301A), located 300 to 500 m away. This array of holes is located on 3.5 My old seafloor, as an array oriented subparallel to the Endeavor Segment of Juan de Fuca Ridge. Borehole fluid samples were collected in copper coils using osmotic pumps. In addition to pumps at seafloor wellheads, downhole sampling pumps were installed in the perforated casing in the upper ocean crust. These downhole samplers were intended to produce a high-resolution continuous record of tracer concentrations, including records from the first year after tracer injection in Holes 1362A and 1362B. In contrast, wellhead samplers were not installed on these CORKs holes until 2011, and wellhead records from all CORKs have a record gap of up to one year, because of a delayed expedition in 2012. The downhole samples were recovered with the submersible Alvin in August 2014. SF6 concentrations in downhole samples recovered in 2014 are generally consistent with data obtained from wellhead samples. Of particular interest are the results from Hole 1362B, where a seafloor valve was opened and closed during various recovery expeditions. High resolution tracer curves produced from the 1362B downhole samples confirm that these operations produced an SF6 breakthrough curve corresponding to a classic push-pull test used to evaluate contaminant field locations in terrestrial setting. Complete analyses of downhole samples from these CORKs are expected to produce high-resolution breakthrough curves that will allow more precise analysis and modeling of hydrothermal flow in the study area.

  16. Geology, mineralogy, and chemistry of sediment-hosted clastic massive sulfides in shallow cores, Middle Valley, northern Juan de Fuca Ridge

    SciTech Connect

    Goodfellow, W.D.; Franklin, J.M. )

    1993-12-01

    Middle Valley is a sediment-covered rift near the northern end of Juan de Fuca Ridge. Hydrothermal fluids are presently being discharged at two vent fields about 3 km apart, Bent Hill and the area of active venting. The hydrothermally active chimneys at both Bent Hill and the area of active venting consist of anhydrite and Mg-rich silicates with minor pyrite, Cu-Fe sulfide, sphalerite, and galena. Hydrothermal discharge in these areas appears to be focused along extensional faults. At the Bent Hill massive sulfide deposit, clastic sulfide layers are interbedded with hydrothermally altered and unaltered hemipelagic and turbiditic sediment along the flanks of the sulfide mound. Sulfide textures and mineralogy suggest that the Bent Hill sulfide mound formed by the build-up and collapse of sulfide chimneys, the resedimentation of sulfide debris and the formation of clastic sulfide layers, and the infilling and replacement of clastic sulfides by hydrothermal fluids near vents. Sulfur isotope values that are consistently more positive than basaltic sulfur support the addition of seawater sulfur. Pb isotope values for the Bent Hill deposit that are transitional between midocean ridge basalt (MORB) and Middle Valley sediments indicate that the sulfides probably formed from fluids which originated in the oceanic crust but which have been modified by reaction with lower temperature (<274 C) fluids generated in the sedimentary pile, similar to those now venting in Middle Valley.

  17. Major- and minor-metal composition of three distinct solid material fractions associated with Juan de Fuca hydrothermal fluids (northeast Pacific), and calculation of dilution fluid samples

    USGS Publications Warehouse

    Hinkley, T.K.; Seeley, J.L.; Tatsumoto, M.

    1988-01-01

    Three distinct types of solid material are associated with each sample of the hydrothermal fluid that was collected from the vents of the Southern Juan de Fuca Ridge. The solid materials appear to be representative of deposits on ocean floors near mid-ocean ridges, and interpretation of the chemistry of the hydrothermal solutions requires understanding of them. Sr isotopic evidence indicates that at least two and probably all three of these solid materials were removed from the solution with which they are associated, by precipitation or adsorption. This occurred after the "pure" hydrothermal fluid was diluted and thoroughly mixed with ambient seawater. The three types of solid materials, are, respectively, a coarse Zn- and Fe-rich material with small amounts of Na and Ca; a finer material also rich in Zn and Fe, but with alkali and alkaline-earth metals; and a scum composed of Ba or Zn, with either considerable Fe or Si, and Sr. Mineral identification is uncertain because of uncertain anion composition. Only in the cases of Ba and Zn were metal masses greater in solid materials than in the associated fluids. For all other metals measured, masses in fluids dwarf those in solids. The fluids themselves contain greater concentrations of all metals measured, except Mg, than seawater. We discuss in detail the relative merits of two methods of determining the mixing proportions of "pure" hydrothermal solution and seawater in the fluids, one based on Sr isotopes, and another previously used method based on Mg concentrations. Comparison of solute concentrations in the several samples shows that degree of dilution of "pure" hydrothermal solutions by seawater, and amounts of original solutes that were removed from it as solid materials, are not related. There is no clear evidence that appreciable amounts of solid materials were not conserved (lost) either during or prior to sample collection. ?? 1988.

  18. Insights on the Biology of the Eastern Lau Spreading Center from Studies on the East Pacific Rise and Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Fisher, C. R.; Sen, A.; Becker, E.

    2011-12-01

    A primary goal of the Ridge 2000 program was to conduct comparable interdisciplinary studies at a few fundamentally different sites that would facilitate comparisons among sites and development of concepts with broad application across deep ocean ridge spreading centers. Although the Eastern Lau Spreading Center (ELSC) was the least known of the three Integrated Study Sites, we were able to make amazingly fast progress on understanding this system because we could draw on technology and experience developed during the RIDGE program to plan and conduct the work, and now interpret our findings in the context of the rich literature and Ridge 2000 studies on East Pacific Rise (EPR) , Juan de Fuca Ridge (JdFR), and Mid Atlantic Ridge communities. The ELSC communities not only house different species than those of the other regions, but unlike the often tubeworm dominated E. Pacific vents, they are structured by symbiont reliant species that are mobile; snails and mussels. Although there is some variation with lava type on the ELSC, the 4 species of large, symbiont-containing snails largely occupy the niches filled by tubeworms and mussels on the EPR, while the niche of the mussel in the W. Pacific vents is quite different from that of its EPR cousin. Although we have not observed any significant tectonic or magmatic events during our studies of the ELSC, 4 years of study considered in the context of what we have learned on the EPR and JdFR allow us to formulate and begin testing hypotheses about temporal change and succession in these very different and much less visited ecosystems. Furthermore, athough Paralvinella fijiensis are only found in limited areas on some chimneys and flanges, unlike the situation on the EPR and JdFR ,the ELSC chimney communities are largely composed of the same species as are found in diffuse flow on the lavas. The ELSC chimney communities are also remarkably stable, hosting some of the largest and apparently oldest individuals found on the

  19. Preliminary Results from a Gas Tracer Injection Experiment in the Upper Oceanic Crust on the Eastern Flank of the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Neira, N. M.; Clark, J. F.; Fisher, A. T.; Wheat, C. G.

    2013-12-01

    We present the first results from a gas tracer injection experiment in the ocean crust on the eastern flank of the Juan de Fuca Ridge, in an area of vigorous hydrothermal circulation. A mixture of tracers was injected in Hole 1362B in 2010, during IODP Expedition 327, as part of a 24-hour pumping experiment. Fluid samples were subsequently collected from this hole and three additional holes (1026B, 1362A, and 1301A), located 300 to 500 m away. The array of holes is located on 3.5 M.y. old seafloor, and oriented N20°E, subparallel to the Endeavor Segment of Juan de Fuca Ridge, 100 km to the west. Sulfur hexafluoride (SF6) was injected at a concentration of 0.0192 mol/min, with fluid pumping rate of 6.7 L/s for 20.2 h, resulting in a mean concentration of 47.6 μM and 23.3 mol of SF6 being added to crustal fluids. Borehole fluid samples were collected in copper coils using osmotic pumps attached to the wellheads of several long-term, subseafloor observatories (CORKs). These samples were recovered from the seafloor using a remotely-operated vehicle in 2011 and 2013. Analyses of SF6 concentrations in samples recovered in 2011 indicate the first arrival of SF6 in Hole 1301A, 550 m south of the injection Hole 1362B, ~265 days after injection. This suggests that the most rapid lateral transport of gas (at the leading edge of the plume) occurred at ~2 m/day. Samples recovered in 2013 should provide a more complete breakthrough curve, allowing assessment of the mean lateral transport rate. Additional insights will come from analysis of metal salts and particle tracers injected contemporaneously with the SF6, the cross-hole pressure response to injection and a two-year fluid discharge experiment. Additional wellhead samples will be collected in Summer 2014, as will downhole osmosamplers deployed in perforated casing within the upper ocean crust in Holes 1362A and 1362B.

  20. Seismic reflection imaging of the Juan de Fuca plate from ridge to trench: New constraints on the distribution of faulting and evolution of the crust prior to subduction

    NASA Astrophysics Data System (ADS)

    Han, Shuoshuo; Carbotte, Suzanne M.; Canales, Juan Pablo; Nedimović, Mladen R.; Carton, Hélène; Gibson, James C.; Horning, Greg W.

    2016-03-01

    We present prestack time-migrated multichannel seismic images along two cross-plate transects from the Juan de Fuca (JdF) Ridge to the Cascadia deformation front (DF) offshore Oregon and Washington from which we characterize crustal structure, distribution and extent of faults across the plate interior as the crust ages and near the DF in response to subduction bending. Within the plate interior, we observe numerous small offset faults in the sediment section beginning 50-70 km from the ridge axis with sparse fault plane reflections confined to the upper crust. Plate bending due to sediment loading and subduction initiates at ~120-150 km and ~65-80 km seaward of the DF, respectively, and is accompanied by increase in sediment fault offsets and enhancement of deeper fault plane reflectivity. Most bend faulting deformation occurs within 40 km from the DF; on the Oregon transect, bright fault plane reflections that extend through the crust and 6-7 km into the mantle are observed. If attributed to serpentinization, ~0.12-0.92 wt % water within the uppermost 6 km of the mantle is estimated. On the Washington transect, bending faults are confined to the sediment section and upper-middle crust. The regional difference in subduction bend-faulting and potential hydration of the JdF plate is inconsistent with the spatial distribution of intermediate-depth intraslab seismicity at Cascadia. A series of distinctive, ridgeward dipping (20°-40°) lower crustal reflections are imaged in ~6-8 Ma crust along both transects and are interpreted as ductile shear zones formed within the ridge's accretionary zone in response to temporal variations in mantle upwelling, possibly associated with previously recognized plate reorganizations at 8.5 Ma and 5.9 Ma.

  1. Contrasting two-dimensional and three-dimensional models of outcrop-to-outcrop hydrothermal circulation on the eastern flank of the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Fisher, A. T.; Winslow, D. M.; Stauffer, P. H.; Gable, C. W.; Zyvoloski, G.

    2015-12-01

    We present results from two-dimensional and three-dimensional coupled (fluid and heat flow) simulations of ridge-flank hydrothermal circulation on the eastern flank of the Juan de Fuca Ridge. Field studies in this region demonstrate the existence of an active hydrothermal siphon operating between two seamounts separated by ~50 km, and provide quantitative constraints that help to determine which simulations are successful in replicating known properties and processes. Constraints from field observations include (a) the flow rate between the outcrops, (b) the presence of secondary convection within the basement aquifer, leading to simultaneous recharge and discharge through a single outcrop (in additional to siphon flow between outcrops), (c) direct measurements of crustal permeability in basement boreholes, and (d) the lack of a regional seafloor heat flux anomaly as a consequence of outcrop-to-outcrop circulation. New simulations include an assessment of crustal permeability and thickness, outcrop permeability, and a comparison of simulation results using different geometries. Three-dimensional simulations are more consistent with field observations than their two-dimensional counterparts and indicate a crustal aquifer of ≤300 m thick having a bulk permeability between 3×10-13 and 2×10-12 m2, values consistent with borehole measurements. In addition, we find fluid flow rates and crustal cooling efficiencies that are an order of magnitude greater in three-dimensional simulations than inferred from two-dimensional simulations using equivalent properties. These results show that three-dimensional simulations of outcrop-to-outcrop hydrothermal circulation on a ridge flank improves the geological and geometric accuracy of results, in comparison to models run in two dimensions.

  2. Neogene magmatism northeast of the Aegir and Kolbeinsey ridges, NE Atlantic: Spreading ridge-mantle plume interaction?

    NASA Astrophysics Data System (ADS)

    Breivik, AsbjøRn Johan; Faleide, Jan Inge; Mjelde, Rolf

    2008-02-01

    According to mantle plume theory the Earth's interior cools partly by localized large vertical mass transport, causing extensive decompression melting. The Iceland melt anomaly is regarded as a typical example of a mantle plume. However, there are centers of Miocene to recent magmatism in the Norwegian-Greenland Sea not easily explained by the plume theory. Here we present new data to document diffuse late Miocene magmatic underplating of older oceanic crust located mostly north of the Aegir Ridge, an extinct seafloor spreading axis in the Norway Basin. There is also a region with similar magmatism northeast of the presently spreading Kolbeinsey Ridge north of Iceland. Intraplate magmatism in these locations is not easily explained by local plume models, edge-driven convection, or by asthenosphere flow-lithosphere thickness interaction. On the basis of correlation between the magmatism and the active or extinct spreading ridges, we propose the mid-ocean ridge basalt-capture model, in which this magmatism can be understood through plume-spreading ridge interaction: The asthenosphere flow out from Iceland captures deeper, low-degree partially molten asthenospheric regions from underneath the spreading ridges and carry these across the terminating fracture zones, to subsequently underplate oceanic crust or to intrude and build seamounts. This model is similar to lithospheric cracking models for intraplate magmatism in requiring that low-degree partial melt can be retained in the asthenosphere over time but differ in that the magma is extracted by internal magma movement processes and not by external tectonic forces.

  3. A Diverse Community of Metal(loid) Oxide Respiring Bacteria Is Associated with Tube Worms in the Vicinity of the Juan de Fuca Ridge Black Smoker Field.

    PubMed

    Maltman, Chris; Walter, Graham; Yurkov, Vladimir

    2016-01-01

    Epibiotic bacteria associated with tube worms living in the vicinity of deep sea hydrothermal vents of the Juan de Fuca Ridge in the Pacific Ocean were investigated for the ability to respire anaerobically on tellurite, tellurate, selenite, selenate, metavanadate and orthovanadate as terminal electron acceptors. Out of 107 isolates tested, 106 were capable of respiration on one or more of these oxides, indicating that metal(loid) oxide based respiration is not only much more prevalent in nature than is generally believed, but also is an important mode of energy generation in the habitat. Partial 16S rRNA gene sequencing revealed the bacterial community to be rich and highly diverse, containing many potentially new species. Furthermore, it appears that the worms not only possess a close symbiotic relationship with chemolithotrophic sulfide-oxidizing bacteria, but also with the metal(loid) oxide transformers. Possibly they protect the worms through reduction of the toxic compounds that would otherwise be harmful to the host. PMID:26914590

  4. Origin of minor and trace element compositional diversity in anorthitic feldspar phenocrysts and melt inclusions from the Juan de Fuca Ridge

    USGS Publications Warehouse

    Adams, David T.; Nielsen, Roger L.; Kent, Adam J.R.; Tepley, Frank J., III

    2011-01-01

    Melt inclusions trapped in phenocryst phases are important primarily due to their potential of preserving a significant proportion of the diversity of magma composition prior to modification of the parent magma array during transport through the crust. The goal of this investigation was to evaluate the impact of formational and post-entrapment processes on the composition of melt inclusions hosted in high anorthite plagioclase in MORB. Our observations from three plagioclase ultra-phyric lavas from the Endeavor Segment of the Juan de Fuca Ridge document a narrow range of major elements and a dramatically greater range of minor and trace elements within most host plagioclase crystals. Observed host/inclusion partition coefficients for Ti are consistent with experimental determinations. In addition, observed values of DTi are independent of inclusion size and inclusion TiO2 content of the melt inclusion. These observations preclude significant effects from the re-homogenization process, entrapment of incompatible element boundary layers or dissolution/precipitation. The observed wide range of TiO2 contents in the host feldspar, and between bands of melt inclusions within individual crystals rule out modification of TiO contents by diffusion, either pre-eruption or due to re-homogenization. However, we do observe comparatively small ranges for values of K2O and Sr compared to P2O5 and TiO2 in both inclusions and crystals that can be attributed to diffusive processes that occurred prior to eruption.

  5. A Diverse Community of Metal(loid) Oxide Respiring Bacteria Is Associated with Tube Worms in the Vicinity of the Juan de Fuca Ridge Black Smoker Field

    PubMed Central

    Maltman, Chris; Walter, Graham; Yurkov, Vladimir

    2016-01-01

    Epibiotic bacteria associated with tube worms living in the vicinity of deep sea hydrothermal vents of the Juan de Fuca Ridge in the Pacific Ocean were investigated for the ability to respire anaerobically on tellurite, tellurate, selenite, selenate, metavanadate and orthovanadate as terminal electron acceptors. Out of 107 isolates tested, 106 were capable of respiration on one or more of these oxides, indicating that metal(loid) oxide based respiration is not only much more prevalent in nature than is generally believed, but also is an important mode of energy generation in the habitat. Partial 16S rRNA gene sequencing revealed the bacterial community to be rich and highly diverse, containing many potentially new species. Furthermore, it appears that the worms not only possess a close symbiotic relationship with chemolithotrophic sulfide-oxidizing bacteria, but also with the metal(loid) oxide transformers. Possibly they protect the worms through reduction of the toxic compounds that would otherwise be harmful to the host. PMID:26914590

  6. Phylogenetic diversity of microorganisms in subseafloor crustal fluids from Holes 1025C and 1026B along the Juan de Fuca Ridge flank

    PubMed Central

    Jungbluth, Sean P.; Lin, Huei-Ting; Cowen, James P.; Glazer, Brian T.; Rappé, Michael S.

    2014-01-01

    To expand investigations into the phylogenetic diversity of microorganisms inhabiting the subseafloor biosphere, basalt-hosted crustal fluids were sampled from Circulation Obviation Retrofit Kits (CORKs) affixed to Holes 1025C and 1026B along the Juan de Fuca Ridge (JdFR) flank using a clean fluid pumping system. These boreholes penetrate the crustal aquifer of young ocean crust (1.24 and 3.51 million years old, respectively), but differ with respect to borehole depth and temperature at the sediment-basement interface (147 m and 39°C vs. 295 m and 64°C, respectively). Cloning and sequencing of PCR-amplified small subunit ribosomal RNA genes revealed that fluids retrieved from Hole 1025C were dominated by relatives of the genus Desulfobulbus of the Deltaproteobacteria (56% of clones) and Candidatus Desulforudis of the Firmicutes (17%). Fluids sampled from Hole 1026B also contained plausible deep subseafloor inhabitants amongst the most abundant clone lineages; however, both geochemical analysis and microbial community structure reveal the borehole to be compromised by bottom seawater intrusion. Regardless, this study provides independent support for previous observations seeking to identify phylogenetic groups of microorganisms common to the deep ocean crustal biosphere, and extends previous observations by identifying additional lineages that may be prevalent in this unique environment. PMID:24723917

  7. Distribution and composition of hydrothermal plume particles from the ASHES vent field at Axial Volcano, Juan de Fuca Ridge. [Axial Seamount Hydrothermal Emission Study

    SciTech Connect

    Feely, R.A.; Geiselman, T.L.; Baker, E.T.; Massoth, G.J. ); Hammond, S.R. )

    1990-08-10

    In 1986 and 1987, buoyant and neutrally buoyant hydrothermal plume particles from the ASHES vent field within Axial Volcano were sampled to study their variations in composition with height above the seafloor. Individual mineral phases were identified using standard X ray diffraction procedures. Elemental composition and particle morphologies were determined by X ray fluorescence spectrometry and scanning electron microscopy/X ray energy spectrometry techniques. The vent particles were primarily composed of sphalerite, anhydrite, pyrite, pyrrhotite, chalcopyrite, barite, hydrous iron oxides, and amorphous silica. Grain size analyses of buoyant plume particles showed rapid particle growth in the first few centimeters above the vent orifice, followed by differential sedimentation of the larger sulfide and sulfate minerals out of the buoyant plume. The neutrally buoyant plume consisted of a lower plume, which was highly enriched in Fe, S, Zn, and Cu, and an upper plume, which was highly enriched in Fe and Mn. The upper plume was enriched in Fe and Mn oxyhydroxide particles, and the lower plume was enriched in suspended sulfide particles in addition to the Fe and Mn oxyhydroxide particles. The chemical data for the water column particles indicate that chemical scavenging and differential sedimentation processes are major factors controlling the composition of the dispersing hydrothermal particles. Short-term sediment trap experiments indicate that the fallout from the ASHES vent field is not as large as some of the other vent fields on the Juan de Fuca Ridge.

  8. Three-dimensional modeling of outcrop-to-outcrop hydrothermal circulation on the eastern flank of the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Winslow, D. M.; Fisher, A. T.; Stauffer, P. H.; Gable, C. W.; Zyvoloski, G. A.

    2016-03-01

    We present three-dimensional simulations of coupled fluid and heat transport in the ocean crust, to explore patterns and controls on ridge-flank hydrothermal circulation on the eastern flank of the Juan de Fuca Ridge. Field studies have shown that there is large-scale fluid flow in the volcanic ocean crust in this region, including local convection and circulation between two basement outcrops separated by ~50 km. New simulations include an assessment of crustal permeability and aquifer thickness, outcrop permeability, the potential influence of multiple discharging outcrops, and a comparison between two-dimensional (profile) and three-dimensional representations of the natural system. Field observations that help to constrain new simulations include a modest range of flow rates between recharging and discharging outcrops, secondary convection adjacent to the recharging outcrop, crustal permeability determinations made in boreholes, and the lack of a regional seafloor heat flux anomaly as a consequence of advective heat loss from the crust. Three-dimensional simulations are most consistent with field observations when models use a crustal permeability of 3 × 10-13 to 2 × 10-12 m2, and the crustal aquifer is ≤300 m thick, values consistent with borehole observations. We find fluid flow rates and crustal cooling efficiencies that are an order of magnitude greater in three-dimensional simulations than in two-dimensional simulations using equivalent properties. Simulations including discharge from an additional outcrop can also replicate field observations but tend to increase the overall rate of recharge and reduce the flow rate at the primary discharge site.

  9. Eruptive and tectonic history of the Endeavour Segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages

    NASA Astrophysics Data System (ADS)

    Clague, David. A.; Dreyer, Brian M.; Paduan, Jennifer B.; Martin, Julie F.; Caress, David W.; Gill, James B.; Kelley, Deborah S.; Thomas, Hans; Portner, Ryan A.; Delaney, John R.; Guilderson, Thomas P.; McGann, Mary L.

    2014-08-01

    bathymetric surveys from autonomous underwater vehicles ABE and D. Allan B. were merged to create a coregistered map of 71.7 km2 of the Endeavour Segment of the Juan de Fuca Ridge. Radiocarbon dating of foraminifera in cores from three dives of remotely operated vehicle Doc Ricketts provide minimum eruption ages for 40 lava flows that are combined with the bathymetric data to outline the eruptive and tectonic history. The ages range from Modern to 10,700 marine-calibrated years before present (yr BP). During a robust magmatic phase from >10,700 yr BP to ˜4300 yr BP, flows erupted from an axial high and many flowed >5 km down the flanks; some partly buried adjacent valleys. Axial magma chambers (AMCs) may have been wider than today to supply dike intrusions over a 2 km wide axial zone. Summit Seamount formed by ˜4770 yr BP and was subsequently dismembered during a period of extension with little volcanism starting ˜4300 yr BP. This tectonic phase with only rare volcanic eruptions lasted until ˜2300 yr BP and may have resulted in near-solidification of the AMCs. The axial graben formed by crustal extension during this period of low magmatic activity. Infrequent eruptions occurred on the flanks between 2620-1760 yr BP and within the axial graben since ˜1750 yr BP. This most recent phase of limited volcanic and intense hydrothermal activity that began ˜2300 yr BP defines a hydrothermal phase of ridge development that coincides with the present-day 1 km wide AMCs and overlying hydrothermal vent fields.

  10. Eruptive and tectonic history of the Endeavour Segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages

    USGS Publications Warehouse

    Clague, David A.; Dreyer, Brian M; Paduan, Jennifer B; Martin, Julie F; Caress, David W; Gillespie, James B.; Kelley, Deborah S; Thomas, Hans; Portner, Ryan A; Delaney, John R; Guilderson, Thomas P.; McGann, Mary L.

    2016-01-01

    High-resolution bathymetric surveys from autonomous underwater vehicles ABE and D. Allan B. were merged to create a coregistered map of 71.7 km2 of the Endeavour Segment of the Juan de Fuca Ridge. Radiocarbon dating of foraminifera in cores from three dives of remotely operated vehicle Doc Ricketts provide minimum eruption ages for 40 lava flows that are combined with the bathymetric data to outline the eruptive and tectonic history. The ages range from Modern to 10,700 marine-calibrated years before present (yr BP). During a robust magmatic phase from >10,700 yr BP to ~4300 yr BP, flows erupted from an axial high and many flowed >5 km down the flanks; some partly buried adjacent valleys. Axial magma chambers (AMCs) may have been wider than today to supply dike intrusions over a 2 km wide axial zone. Summit Seamount formed by ~4770 yr BP and was subsequently dismembered during a period of extension with little volcanism starting ~4300 yr BP. This tectonic phase with only rare volcanic eruptions lasted until ~2300 yr BP and may have resulted in near-solidification of the AMCs. The axial graben formed by crustal extension during this period of low magmatic activity. Infrequent eruptions occurred on the flanks between 2620–1760 yr BP and within the axial graben since ~1750 yr BP. This most recent phase of limited volcanic and intense hydrothermal activity that began ~2300 yr BP defines a hydrothermal phase of ridge development that coincides with the present-day 1 km wide AMCs and overlying hydrothermal vent fields.

  11. Seismic Structure of the Endeavour Segment, Juan de Fuca Ridge: Correlations of Crustal Magma Chamber Properties With Seismicity, Faulting, and Hydrothermal Activity

    NASA Astrophysics Data System (ADS)

    van Ark, E. M.; Detrick, R. S.; Canales, J. P.; Carbotte, S. M.; Diebold, J. B.; Harding, A.; Kent, G.; Nedimovic, M. R.; Wilcock, W. S.

    2003-12-01

    Multichannel seismic reflection data collected in July 2002 at the RIDGE2000 Integrated Studies Site at the Endeavour segment, Juan de Fuca Ridge show a high-amplitude, mid-crustal reflector underlying all of the known hydrothermal vent fields at this segment. This reflector, which has been identified with a crustal magma body [Detrick et al., 2002], is found at a two-way travel time of 0.85-1.5 s (1.9-4.0 km) below the seafloor and extends approximately 25 km along axis although it is only 1-2 km wide on the cross-axis lines. The reflector is shallowest (2.5 km depth on the along-axis line) beneath the central, elevated part of the Endeavour segment and deepens toward the segment ends, with a maximum depth of 4 km. The cross axis lines show the mid-crustal reflector dipping from 9 to 50? to the east with the shallowest depths under the ridge axis and greater depths under the eastern flank of the ridge. The amplitude-offset behavior of this mid-crustal axial reflector is consistent with a negative impedance contrast, indicating the presence of melt or a crystallizing mush. We have constructed partial offset stacks at 2-3 km offset to examine the variation of melt-mush content of the axial magma chamber along axis. We see a decrease in P-wave amplitudes with increasing offset for the mid-crustal reflector beneath the Mothra and Main Endeavour vent fields and between the Salty Dawg and Sasquatch vent fields, indicating the presence of a melt-rich body. Beneath the High Rise, Salty Dawg, and Sasquatch vent fields P-wave amplitudes vary little with offset suggesting the presence of a more mush-rich magma chamber. Hypocenters of well-located microseismicity in this region [Wilcock et al., 2002] have been projected onto the along-axis and cross-axis seismic lines, revealing that most axial earthquakes are concentrated in a depth range of 1.5 - 2.7 km, just above the axial magma chamber. In general, seismicity is distributed diffusely within this zone indicating thermal

  12. Local Earthquakes on the Endeavour Segment of the Juan de Fuca Ridge: First Seismic Results from the Keck Seismic/Hydrothermal Observatory

    NASA Astrophysics Data System (ADS)

    Wilcock, W. S.; Barclay, A. H.; McGill, P. R.; Stakes, D. S.; Ramirez, T. M.; Toomey, D. R.; Durant, D. T.; Hooft, E. E.; Mulder, T. L.; Ristau, J. P.

    2004-12-01

    The W.M. Keck Foundation is supporting a five-year program to conduct prototype seafloor observatory experiments to monitor the relationships between episodic deformation, fluid venting and microbial productivity on the Endeavour segment of the Juan de Fuca Ridge and at the intersection of the Nootka fault and the Cascadia subduction zone. At the Endeavour, the experiment is sited near the central portion of the segment in a region where the spreading axis is characterized by a 100-m-deep, 500-m-wide axial valley that hosts five high-temperature hydrothermal vent fields spaced 2-3 km apart. The objectives of the experiment are to monitor local and regional seismicity around the vent fields in conjunction with the deployment of sensors and samplers to monitor temporal variations in the physical, chemical and ultimately microbial characteristics of the hydrothermal fluids. The Endeavour seismic network was installed in the summer of 2003 with the ROV ROPOS and comprises seven GEOSense three-component short-period corehole seismometers and one buried Guralp CMG-1T broadband seismometer. Five of the seven short-period seismometers were inserted in horizontal coreholes drilled into seafloor basalts; two were deployed in concrete monuments on the ridge flanks. It is the first seismic network on a mid-ocean ridge in which the sensors are deployed with an ROV beneath the seafloor in order to ensure good coupling and minimize the effects of current-generated noise. In August 2004, we used the ROV Tiburon to service the Endeavour seismic network and recover the first year of data. In addition, we installed a second broadband and three short period seismometers on the Nootka fault and a third broadband seismometer on the Explorer plate. The Endeavour seismic network performed well with all eight instruments recording high-quality data. A preliminary inspection of the data reveals many examples of local, regional and teleseismic earthquakes. One striking characteristic of the

  13. Crustal structure of Axial Volcano on the Juan de Fuca Ridge, from seafloor depths to the bottom of the magma chamber, using Elastic Full Waveform Inversion.

    NASA Astrophysics Data System (ADS)

    Arnulf, Adrien; Harding, Alistair; Kent, Graham

    2013-04-01

    Axial volcano is located at 46˚N, 130˚W at the intersection of the Juan de Fuca Ridge and the Cobb-Eickelberg seamount chain. It is the most recent eruptive center of the Cobb hotspot, which last erupted in 2011. The volcano rises ~700 m above the adjacent ridge axis and its summit features a 8-km-long, U-shaped caldera with an opening to the southeast where there is an active hydrothermal field and very young lava flows. Located at the junction of a mid-ocean ridge and a volcanic hotspot, Axial volcano is atypical and its internal structure remains poorly understood. Here, we present results from an elastic full waveform inversion (FWI) along multiple seismic lines that span the whole volcano. We have used a multi-stage FWI, inverting successively wide-angle reflections and refractions arrivals from downward extrapolated streamer data, then windowed short offset reflections from the underlying magma chamber. Our final models show fine scale velocity structures with spatial resolutions of tens of meters. Our results indicate that Layer 2A thickness is extremely heterogeneous (350-900 m) within the volcano with abrupt vertical offsets of >300 m at the caldera walls, consistent with faulting of a geologically defined Layer 2A. Interestingly, Layer 2A appears to be extremely thin beneath the active hydrothermal field, where sheeted dikes might lay <100 m beneath the seafloor. On the other hand, the ever-dropping floor of the caldera appears to be a perfect trap for the ponding of lava flows: the thickness of the lava flows increase gradually to the northwest reaching ~450 m at end of the caldera. Surface velocities are low and exhibit limited variation over the whole volcano suggesting relative recent formation, as layer 2A velocity increases rapidly with age at slightly greater depths. Crustal aging (increase in layer 2A velocity with age) appears to be controlled by pipe-like pattern of focused hydrothermal mineralization. Finally, RTM images reveal a large melt

  14. Constraining Seasonal and Vertical Distributions of Planktonic Foraminifera for Paleoclimate Reconstruction Since MIS3 at the Axial Seamount, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Chen, S. L.; Ravelo, A. C.; Clague, D. A.

    2015-12-01

    The California Current is an upwelling region with dynamic interactions between circulation, biological productivity and ecology. A 77 cm piston push core was taken from the Juan de Fuca Ridge Axial Seamount using a Remotely Operated Vehicle (ROV) (2213m, 45.55º N, 130.08º W), an active submarine volcano ~480 km off Oregon's coast. Five radiocarbon dates indicate that the sediment ranges from 42.6 ka at 77 cm to 17.6 ka at 15 cm, with an average sediment accumulation rate of 2.47 cm/ka from 77-15 cm, and an average rate of 0.85 cm/ka during the postglacial period (<17.6 ka). Multiple species of planktic foraminifera from the core representing subtropical, subartic, and arctic fauna have been used to constrain changes in vertical and seasonal temperature since Marine Isotope Stage 3 (MIS3). Measurements of δ18O of the upwelling species Globigerina bulloides, the thermocline dwelling species Neogloboquadrina dutertrei, and the warm mixed-layer species Orbulina universa are offset from each other, reflecting vertical and seasonal variation among the planktonic foraminifera. Of the three species, G. bulloides shows the least variation in δ18O, possibly indicating that marked changes in temperature are masking changes in the δ18O of seawater due to global ice volume changes. G. bulloides and O. universa δ18O values are similar in MIS 3 and diverge with time, indicating the development of strong seasonal succession of species, since the last glacial maximum. Bulk nitrogen isotopes and nitrogen flux provide additional constraints on upwelling strength and insight into local biological productivity and nutrient dynamics. Obtaining Mg/Ca data will clarify the δ 18O interpretation except deep in the core where metal-bearing authigenic precipitates affect Mg concentrations. These climatic proxies together provide insight into how global climate change and local seamount volcanism impacts regional productivity in the California Current.

  15. Metalloid reducing bacteria isolated from deep ocean hydrothermal vents of the Juan de Fuca Ridge, Pseudoalteromonas telluritireducens sp. nov. and Pseudoalteromonas spiralis sp. nov.

    PubMed

    Rathgeber, Christopher; Yurkova, Natalia; Stackebrandt, Erko; Schumann, Peter; Humphrey, Elaine; Beatty, J Thomas; Yurkov, Vladimir

    2006-11-01

    Five strains of Gram-negative, rod, curved rod and spiral-shaped bacteria were isolated from the vicinity of deep ocean hydrothermal vents along the Main Endeavour Segment of the Juan de Fuca Ridge in the Pacific Ocean. All strains showed remarkable resistance to high levels of toxic metalloid oxyanions, and were capable of reducing the oxyanions tellurite and selenite to their less toxic elemental forms. Phylogenetic analysis of four strains identified these isolates as close relatives of the genus Pseudoalteromonas within the class Gammaproteobacteria. Pseudoalteromonas agarivorans was the closest relative of strains Te-1-1 and Se-1-2-redT, with, respectively, 99.5 and 99.8% 16S rDNA sequence similarity. Strain Te-2-2T was most closely related to Pseudoalteromonas paragorgicola, with 99.8% 16S rDNA sequence similarity. The DNA G+C base composition was 39.6 to 41.8 mol%, in agreement with other members of the genus Pseudoalteromonas. However, the isolates showed important morphological and physiological differences from previously described species of this genus, with one group forming rod-shaped bacteria typical of Pseudoalteromonas and the other forming vibrioid- to spiral-shaped cells. Based on these differences, and on phylogenetic data, we propose the creation of the new species Pseudoalteromonas telluritireducens sp. nov., with strain Se-1-2-redT (DSMZ = 16098T = VKM B-2382T) as the type strain, and Pseudoalteromonas spiralis sp. nov., with strain Te-2-2T (DSMZ = 16099T = VKM B-2383T) as the type strain. PMID:17066332

  16. Numerical Modeling of Two-Phase Flow at the Main Endeavour Field, Juan de Fuca Ridge: Quasi-Steady State and Thermal Decline of the Vent Field

    NASA Astrophysics Data System (ADS)

    Singh, S.; Lowell, R. P.; Lewis, K. C.

    2012-12-01

    The Main Endeavour Field (MEF) on the Juan de Fuca Ridge consists of a large number of chimney structures occupying an area approximately 400 m x 150 m along the ridge axis. For nearly a decade, the MEF exhibited quasi-steady north-south trending spatial gradients of both temperature and salinity. We have constructed 2-D across-axis numerical models of two-phase flow using the code FISHES to investigate possible causes for this variation. We considered the effect of bottom boundary temperature and both a homogeneous permeability structure and a geometry incorporating a more-permeable layer 2A. From these model results we argue that such a trend is more likely to be the result of heterogeneous permeability structure of the shallow oceanic crust than a result of bottom boundary temperature variations. After a magmatic event in 1999, this trend was disrupted; and thermal data using the Autonomous Benthic Explorer (ABE) indicates that there has been a significant decline in the heat output from a value of approximately 450 MW in 2000 to approximately 300 MW in 2004. In the southern part of the vent field, vent salinities have also increased from values well below those of seawater to values close to seawater. We therefore extend our investigation to include the effect of a temporally-decaying basal heat flow, which may result from cooling, crystallizing magma chamber, on the system. Our aim is to determine whether such a phenomenon could cause the observed rapid decline of heat flow and changes in vent salinity at the MEF. We find that the thermal inertia in the system is such that changes in basal heat flow would be difficult to detect in the given time frame, if magma replenishment ceased following the 1999 magmatic event. The time delay between changes in bottom conditions and the observed decay in observed heat output suggests that the 1999 event represented a small replenishment event and that the AMC may have begun cooling some time before that. Moreover, because

  17. Microearthquakes beneath the Hydrothermal Vent Fields on the Endeavour Segment of the Juan de Fuca Ridge: Results from the Keck Seismic/Hydrothermal Observatory

    NASA Astrophysics Data System (ADS)

    Bowman, D.; Parker, J.; Wilcock, W.; Hooft, E.; Barclay, A.; Toomey, D.; McGill, P.; Stakes, D.; Schmidt, C.; Patel, H.

    2005-12-01

    The W.M. Keck Foundation is supporting the operation of a small seismic network in the vicinity of the hydrothermal vent fields on the central portion of the Endeavour Segment of the Juan de Fuca Ridge. This is part of a program to conduct prototype seafloor observatory experiments to monitor the relationships between episodic deformation, fluid venting and microbial productivity at oceanic plate boundaries. The Endeavour seismic network was installed in the summer of 2003 and comprises seven GEOSense three-component short-period corehole seismometers and one buried Guralp CMG-1T broadband seismometer. A preliminary analysis of the first year of data was undertaken as part of an undergraduate research apprenticeship class taught at the University of Washington's Friday Harbor Laboratories and additional analysis has since been completed by two of the apprentices and by two IRIS undergraduate interns. Over 12,000 earthquakes were located along the ridge-axis of the Endeavour, of which ~3,000 occur within or near the network and appear to be associated with the hydrothermal systems. The levels of seismicity are strongly correlated with the intensity of venting with particularly high rates of seismicity beneath the Main and High Rise Fields and substantially lower rates to the north beneath the relatively inactive Salty Dawg and Sasquatch fields. We have used both HYPOINVERSE and a grid search algorithm to investigate the distribution of focal depths assuming a variety of one-dimensional velocity models. The preliminary results show that the majority of earthquakes occur within a narrow depth range and may represent an intense zone of seismicity within a reaction overlying the axial magma chamber at ~2.5 km depth. However, the mean focal depth is strongly dependent on the relative weights assigned to the S arrivals. We infer from the inspection of residuals that no combination of the P- and S-wave velocity models we have so far investigated are fully consistent with

  18. Age, Episodicity and Migration of Hydrothermal Activity within the Axial Valley, Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Jamieson, J. W.; Hannington, M. D.; Kelley, D. S.; Clague, D. A.; Holden, J. F.; Tivey, M. K.; Delaney, J. R.

    2011-12-01

    Hydrothermal sulfide deposits record the history of high-temperature venting along the Endeavour Segment. Active venting is currently located within five discreet vent fields, with minor diffuse venting occurring between the fields. However, inactive and/or extinct sulfide structures are found throughout the entire axial valley of the ridge segment, suggesting that hydrothermal activity has been more vigorous in the past or focused venting has migrated with time. Here, we present age constraints from U-series dating of 44 sulfide samples collected by manned submersible from between the Mothra Field in the south to Sasquatch in the north. Samples are dated using 226Ra/Ba ratios from hydrothermal barite that precipitates along with the sulfide minerals. Most samples have been collected from within or near the active vent fields. Fifteen samples from the Main Endeavour Field (MEF) show a spectrum of ages from present to 2,430 years old, indicating that this field has been continuously active for at least ~2,400 years. MEF appears to be oldest currently active field. This minimum value for the age of hydrothermal activity also provides a minimum age of the axial valley itself. Ages from thirteen samples from the High-Rise Field indicate continuous venting for at least the past ~1,250 years. These age data are used in conjunction with age constraints of the volcanic flows to develop an integrated volcanic, hydrothermal and tectonic history of the Endeavour Segment. The total volume of hydrothermal sulfide within the axial valley, determined from high-resolution bathymetry, is used in conjunction with the age constraints of the sulfide material to determine the mass accumulation rates of sulfide along the Endeavour Segment. These data can be used to calibrate the efficiency of sulfide deposition from the hydrothermal vents, and provide a time-integrated history of heat, fluid and chemical fluxes at the ridge-segment scale. The comparison of time-integrated rates with

  19. Characterization of Active Hydrothermal Fluid Discharge and Recharge Zones in the Endeavour Axial Valley, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Salmi, M.; Hutnak, M.; Hearn, C.; Tivey, M.; Bjorklund, T.; Johnson, H. P.

    2012-12-01

    Sites where warm hydrothermal fluid vents at mid-ocean spreading centers are important for understanding a wide range of critical oceanic processes, but discharge zones represent a very limited portion of crustal fluid circulation pathways. Mapping the distribution of both fluid recharge and discharge sites within the axial valley provides wider insight into the larger scale features of hydrothermal circulation. Our 2011 survey consisted of 180 conductive heat flow stations within the Endeavour axial valley in roughly a 400 m by 1000 m grid, extending across the entire axial valley from the outer flank of the western boundary ridge to the eastern wall. Data acquisition used thermal blankets which measured conductive heat flow without requiring substantial sediment cover. A surprising result from this survey was zones of high heat flow extending across-strike, from the summit of the west valley wall across the entire axial valley floor. This trend was correlated with anomalously low seafloor magnetization from a near-bottom survey with the ROV JASON. Unexpectedly, over half of the axial valley floor was anomalously low at <50 mW m-2, while a small portion of the sites within the 'warm zone' had heat flow values >1 W m-2. The areas of extremely low heat flow values are interpreted as being directly influenced by recharge zones. Based on MCS estimates of partial melt depth below the axial valley and the assumption of no fluid advection, the purely conductive heat flow for this region should be on the order of 1 W m-2.The observation that conductive heat flux is suppressed over large portions of the axial valley floor suggests that heat transfer within the crustal sub-surface fluid reservoir is widespread, and impacts a large portion of our survey area. The largely bi-modal distribution of high and low conductive heat flow, coupled with geophysical and video observations, suggest current Endeavour axial valley crustal fluid circulation models need to be re-evaluated.

  20. Seismicity Along the Endeavour Segment of the Juan de Fuca Ridge: Automated Event Locations for an Ocean-Bottom Seismometer Network

    NASA Astrophysics Data System (ADS)

    Weekly, R. T.; Wilcock, W. S.; Hooft, E. E.; Toomey, D. R.; McGill, P. R.

    2004-12-01

    From 2003-2006, the W.M. Keck Foundation supported the operation of a network of eight ocean-bottom seismometers (OBSs) that were deployed with a remotely operated vehicle along the central portion of the Endeavour Segment of the Juan de Fuca mid-ocean ridge as part of a multidisciplinary prototype NEPTUNE experiment. Data from 2003-2004 were initially analyzed during a research apprenticeship class at the University of Washington's Friday Harbor Laboratories. Eight student analysts located ~13,000 earthquakes along the Endeavour Segment. Analysis of data from 2004-2005 has to date been limited to locating ~6,000 earthquakes associated with a swarm in February-March 2005 near the northern end of the Endeavour Segment. The remaining data includes several significant swarms and it is anticipated that tens of thousands of earthquakes still need to be located. In order to efficiently obtain a complete catalog of high-quality locations for the 3-year experiment, we are developing an automatic method for earthquake location. We first apply a 5-Hz high-pass filter and identify triggers when the ratio of the root-mean square (RMS) amplitudes in short- and long- term windows exceeds a specified threshold. We search for events that are characterized by triggers within a short time interval on the majority of stations and use the signal spectra to eliminate events that are the result of 20-Hz Fin and Blue whale vocalizations. An autoregressive technique is applied to a short time window centered on the trigger time to pick P-wave times on each station's vertical channel. We locate the earthquake with these picks and either attempt to repick or eliminate arrivals with unacceptable residuals. Preliminary S-wave picks are then made on the horizontal channels by applying a 5-12 Hz bandpass filter, identifying the peak RMS amplitude for a short running window, and making a pick at the time the RMS amplitude rises above 50% of this value. The picks are refined using the

  1. Seismicity Along the Endeavour Segment of the Juan de Fuca Ridge: Automated Event Locations for an Ocean-Bottom Seismometer Network

    NASA Astrophysics Data System (ADS)

    Weekly, R. T.; Wilcock, W. S.; Hooft, E. E.; Toomey, D. R.; McGill, P. R.

    2007-12-01

    From 2003-2006, the W.M. Keck Foundation supported the operation of a network of eight ocean-bottom seismometers (OBSs) that were deployed with a remotely operated vehicle along the central portion of the Endeavour Segment of the Juan de Fuca mid-ocean ridge as part of a multidisciplinary prototype NEPTUNE experiment. Data from 2003-2004 were initially analyzed during a research apprenticeship class at the University of Washington's Friday Harbor Laboratories. Eight student analysts located ~13,000 earthquakes along the Endeavour Segment. Analysis of data from 2004-2005 has to date been limited to locating ~6,000 earthquakes associated with a swarm in February-March 2005 near the northern end of the Endeavour Segment. The remaining data includes several significant swarms and it is anticipated that tens of thousands of earthquakes still need to be located. In order to efficiently obtain a complete catalog of high-quality locations for the 3-year experiment, we are developing an automatic method for earthquake location. We first apply a 5-Hz high-pass filter and identify triggers when the ratio of the root-mean square (RMS) amplitudes in short- and long- term windows exceeds a specified threshold. We search for events that are characterized by triggers within a short time interval on the majority of stations and use the signal spectra to eliminate events that are the result of 20-Hz Fin and Blue whale vocalizations. An autoregressive technique is applied to a short time window centered on the trigger time to pick P-wave times on each station's vertical channel. We locate the earthquake with these picks and either attempt to repick or eliminate arrivals with unacceptable residuals. Preliminary S-wave picks are then made on the horizontal channels by applying a 5-12 Hz bandpass filter, identifying the peak RMS amplitude for a short running window, and making a pick at the time the RMS amplitude rises above 50% of this value. The picks are refined using the

  2. Competing styles of deep-marine explosive eruptions revealed from Axial seamount and Juan De Fuca ridge push core records

    NASA Astrophysics Data System (ADS)

    Portner, R. A.; Clague, D. A.; Paduan, J. B.; Martin, J. F.

    2012-12-01

    extremely fine-grained, angular-sliver shaped and locally concentrated into reverse graded laminae. Fluidal shards are rare. Plagioclase fragments are locally abundant up to 15%. A significant component of hydrothermal grains also occurs and consists of pale greenish-blue clay aggregates, reddish-orange botryoidal grains, anyhydrite, barite or zeolite, and pyrite. X-ray diffraction analysis indicates that the muddy host contains minor nontronite or saponite, and chlorite. This mineral association is in stark contrast to quartz-illite bearing sediment samples from adjacent ridge segments, and supports the interpretation that the ashy mud deposits on Axial seamount preserve hydrothermal activity. Analogous to a phreatomagmatic eruption on land, we envisage shallow circulation of hydrothermal fluids below the vent and hydrovolcanic fragmentation during ascent through the conduit. Lamination and grading criteria suggest that beds were deposited via dilute turbidity flows and reworked by ocean bottom currents. Associations of the two pyroclastic lithofacies with interbedded fossiliferous-bioturbated mud, indicates relatively quiescent periods between separate magmatic or phreatomagmatic eruptions. These eruptive modes extend our knowledge about the range in deep-marine explosive activity.

  3. Very High Resolution Bathymetric Mapping at the Ridge 2000 Integrated Study Sites: Acquisition and Processing Protocols Developed During Recent Alvin Field Programs to the East Pacific Rise and Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Ferrini, V.; Fornari, D. J.; Shank, T.; Tivey, M.; Kelley, D. S.; Glickson, D.; Carbotte, S. M.; Howland, J.; Whitcomb, L. L.; Yoerger, D.

    2004-12-01

    Recent field programs at the East Pacific Rise and Juan de Fuca Ridge have resulted in the refinement of data processing protocols that enable the rapid creation of high-resolution (meter-scale) bathymetric maps from pencil-beam altimetric sonar data that are routinely collected during DSV Alvin dives. With the development of the appropriate processing tools, the Imagenex sonar, a permanent sensor on Alvin, can be used by a broad range of scientists permitting the analysis of various data sets within the context of high-quality bathymetric maps. The data processing protocol integrates depth data recorded with Alvin's Paroscientific pressure sensor with bathymetric soundings collected with an Imagenex 675 kHz articulating (scanning) sonar system, and high-resolution navigational data acquired with DVLNAV, which includes bottom lock Doppler sonar and long baseline (LBL) navigation. Together these data allow us, for the first time, to visualize portions of Ridge 2000 Integrated Study Sites (ISS) at 1-m vertical and horizontal resolution. These maps resolve morphological details of structures within the summit trough at scales that are relevant to biological communities (e.g. hydrothermal vents, lava pillars, trough walls), thus providing the important geologic context necessary to better understand spatial patterns associated with integrated biological-hydrothermal-geological processes. The Imagenex sonar is also a permanent sensor on the Jason2 ROV, which is also equipped with an SM2000 (200 kHz) near-bottom multibeam sonar. In the future, it is envisioned that near-bottom multibeam sonars will be standard sensors on all National Deep Submergence Facility (NDSF) vehicles. Streamlining data processing protocols makes these datasets more accessible to NDSF users and ensures broad compatibility between data formats among NDSF vehicle systems and allied vehicles (e.g. ABE). Establishing data processing protocols and software suites, routinely calibrating sensors (e

  4. Microbial and Mineral Descriptions of the Interior Habitable Zones of Active Hydrothermal Chimneys from the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Holden, J. F.; Lin, T.; Ver Eecke, H. C.; Breves, E.; Dyar, M. D.; Jamieson, J. W.; Hannington, M. D.; Butterfield, D. A.; Bishop, J. L.; Lane, M. D.

    2013-12-01

    Actively venting hydrothermal chimneys and their associated hydrothermal fluids were collected from the Endeavour Segment, Juan de Fuca Ridge to determine the mineralogy, chemistry and microbial community composition of their interiors. To characterize the mineralogy, Mössbauer, FTIR, VNIR and thermal emission spectroscopies were used for the first time on this type of sample in addition to thin-section petrography, x-ray diffraction and elemental analyses. A chimney from the Bastille edifice was Fe-sulfide rich and composed primarily of chalcopyrite, marcasite-sphalerite, and pyrrhotite while chimneys from the Dante and Hot Harold edifices were Fe-sulfide poor and composed primarily of anhydrite. The bulk emissivity and reflectance spectroscopies corroborated well with the petrography and XRD analyses. The microbial community in the interior of Bastille was most closely related to mesophilic-to-thermophilic anaerobes of the deltaproteobacteria and hyperthermophilic archaea while those in the interiors of Dante and Hot Harold were most closely related to mesophilic-to-thermophilic aerobes of the beta-, gamma- and epsilonproteobacteria. The fluid temperatures (282-321°C) and chemistries of the three chimneys were very similar suggesting that differences in mineralogy and microbial community compositions were more dependent on fluid flow characteristics and paragenesis within the chimney. Thin-section petrography of the interior of another hydrothermal chimney collected from the Dante edifice (emitting 336°C fluid) shows a thin coat of Fe3+ oxide associated with amorphous silica on the exposed outer surfaces of pyrrhotite, sphalerite and chalcopyrite in pore spaces, along with anhydrite precipitation in the pores that is indicative of seawater ingress. The Fe-sulfide minerals were likely oxidized to ferrihydrite with increasing pH and Eh due to cooling and seawater exposure, providing reactants for bioreduction. Culture-based most-probable-number estimates of

  5. The Cobb-Eickelberg seamount chain: Hotspot volcanism with mid-ocean ridge basalt affinity

    SciTech Connect

    Desonie, D.L.; Duncan, R.A. )

    1990-08-10

    Cobb hotspot, currently located beneath Axial seamount on the Juan de Fuca ridge, has the temporal but not the isotopic characteristics usually attributed to a mantle plume. The earlier volcanic products of the hotspot, form eight volcanoes in the Cobb-Eickelberg seamount (CES) chain, show a westward age progression away from the hotspot and a westward increase in the age difference between the seamounts and the crust on which they formed. These results are consistent with movement of the Pacific plate over a fixed Cobb hotspot and eventual encroachment by the westwardly migrating Juan de Fuca ridge. CES lavas are slightly enriched in alkalies and incompatible elements relative to those of the Juan de Fuca ridge but they have Sr, Nd, and Pb isotopic compositions virtually identical to those found along the ridge. Therefore, Cobb hotspot is a stationary, upper mantle melting anomaly whose volcanic products show strong mid-ocean ridge basalt (MORB) affinity. These observations can be explained by low degrees of partial melting of entrained heterogeneous upper mantle MORB source material within a thermally driven lower mantle diapir or by an intrinsic MORB-like composition of the deeper mantle source region from which northeast Pacific plumes rise.

  6. An estimate of hydrothermal fluid residence times and vent chimney growth rates based on 210Pb Pb ratios and mineralogic studies of sulfides dredged from the Juan de Fuca Ridge

    USGS Publications Warehouse

    Kadko, D.; Koski, R.; Tatsumoto, M.; Bouse, R.

    1985-01-01

    The 210Pb Pb ratios across two sulfide samples dredged from the Juan de Fuca Ridge are used to estimate the growth rate of the sulfide material and the residence time of the hydrothermal fluid within the oceanic crust from the onset of basalt alteration. 210Pb is added to the hydrothermal fluid by two processes: (1) high-temperature alteration of basalt and (2) if the residence time of the fluid is on the order of the 22.3-year half-life of 210Pb, by in-situ growth from 222Rn (Krishnaswami and Turekian, 1982). Stable lead is derived only from the alteration of basalt. The 210Pb Pb ratio across one sample was ??? 0.5 dpm/10-6 g Pb, and across the other it was ??? 0.4 dpm/10-6 g Pb. These values are quite close to the 238U Pb ratios of basalts from the area, suggesting that the residence time of the hydrothermal fluid from the onset of basalt alteration is appreciably less than the mean life of 210Pb, i.e., the time required for ingrowth from the radon. An apparent growth rate of 1.2 cm/yr is derived from the slope of the 210Pb Pb curve for one of the samples. This is consistent with its mineralogy and texture which suggest an accretionary pattern of development. There is no obvious sequential growth pattern, and virtually no gradient in 210Pb Pb across the second sample. This is consistent with alteration of the original 210Pb Pb distribution by extensive remobilization reactions which are inferred from the mineralogic and textural relationships of the sample. ?? 1985.

  7. Re-evaluating across-axis geochemical variations at the East Pacific Rise and Juan de Fuca Ridge: on- and off-axis melt delivery

    NASA Astrophysics Data System (ADS)

    Perfit, M. R.; Walters, R. L.

    2014-12-01

    High spatial density geochemical data sets from the N-EPR and S-JdFR are used to re-evaluate the across-axis geochemical variations in major and trace elements at mid-ocean ridges (MORs). At two axial melt lens (AML) segments, north and south, at the 9-10°N EPR, N-MORB MgO varies across-axis from the most primitive above the AML to more evolved away from the axis. This trend is distinct at the northern (magmatically more robust) segment with an axial MgO range of 8-9 wt% and off-axis (>2km) range of 6.5-8 wt%. This decrease is also reflected in E-MORB MgO variation. There is more variability at the southern segment but, off-axis progression to more evolved MgO is still evident. Interestingly, the Cleft segment, JdFR, displays similar geochemical behavior to the EPR with an axial MgO range of 7-8.5 wt% and off-axis (>2km) range of 6-7.5 wt%. EPR geochemical studies over the past 30 years have described models of upper crustal accumulation ranging from eruptions limited to the axis, to temporal variation in the composition of magma in the AML, to multiple eruption sites across the ridge crest and flanks (<5km). Eruptions limited to the axis, with topographically controlled flow off-axis, cannot reproduce the observed off-axis change to more evolved N-MORB. Time-dependence could explain one instance of evolved lavas off-axis but, similar geochemical behavior is observed at two separate AML segments. Multiple instances of consistent compositional variability at multiple AML segments, and at different ridges, point to a common process of crustal accretion at MORs. In light of recent geophysical discoveries of Off-axis AMLs (OAMLs) at the EPR and JdFR, we propose that the trend of more evolved lavas for the majority of N-MORB lavas with distance from the axis is controlled by thermal distribution in the underlying crystal mush zone (CMZ). Higher magma flux beneath the axis facilitates higher temperatures and high porosity melt pathways, reducing crustal residence times

  8. Phylogenetic and Physiological Diversity of Subseafloor Microbial Communities at Axial Seamount, Juan de Fuca Ridge: Summary of Results From the New Millenium Observatory (NeMO), 1998-2004

    NASA Astrophysics Data System (ADS)

    Baross, J. A.; Huber, J. A.; Mehta, M. P.; Opatkiewicz, A.; Bolton, S. A.; Butterfield, D. A.; Sogin, M. L.; Embley, R. W.

    2005-12-01

    Axial Seamount (45 ° 58' N; 130 ° 00' W) is an active submarine volcano located on the Juan de Fuca Ridge, approximately 300 miles off the coast of Oregon. Lying at the intersection of a seamount chain and a spreading axis, Axial is a unique study site from both the geological and biological perspective. In January of 1998, Axial experienced a week-long series of earthquakes, and subsequent water column and seafloor observations on the southeast portion of the caldera found temperature and chemical anomalies, extensive new seafloor lava flows, large "snow blower" type vents, and other characteristics commonly associated with diking-eruptive events. Due to its high activity and close proximity to shore, Axial was chosen as a site for a multi-year observatory (New Millenium Observatory, NeMO) to document changes and interactions between geology, chemistry, and biology on the mid-ocean ridge system. From 1998 through 2004, we extensively sampled diffuse vents at Axial Seamount to determine the physiological and phylogenetic diversity of subseafloor microbial communities and their relationship to the geochemical environment. Here we present a summary of those studies, including molecular-based phylogenetic surveys of bacteria, archaea, and potential nitrogen-fixing organisms, culturing results of thermophiles and hyperthermophiles from over 20 sites, and the distribution of one particular group of hyperthermophiles at diffuse vents throughout the caldera and how that distribution may be linked to the geochemical habitat. Results indicate that Axial supports a diverse subseafloor microbial community, including hydrogen and sulfur oxidizers, hyperthermophilic methane producers and heterotrophs, and many organisms with the potential to fix nitrogen. In addition, we find that the species composition of the microbial community changes in response to changes in the physical and chemical conditions at each vent site. The extent of seawater mixing with hydrothermal fluids

  9. Phylogenetic Diversity of Nitrogenase (nifH) Genes in Deep-Sea and Hydrothermal Vent Environments of the Juan de Fuca Ridge

    PubMed Central

    Mehta, Mausmi P.; Butterfield, David A.; Baross, John A.

    2003-01-01

    The subseafloor microbial habitat associated with typical unsedimented mid-ocean-ridge hydrothermal vent ecosystems may be limited by the availability of fixed nitrogen, inferred by the low ammonium and nitrate concentrations measured in diffuse hydrothermal fluid. Dissolved N2 gas, the largest reservoir of nitrogen in the ocean, is abundant in deep-sea and hydrothermal vent fluid. In order to test the hypothesis that biological nitrogen fixation plays an important role in nitrogen cycling in the subseafloor associated with unsedimented hydrothermal vents, degenerate PCR primers were designed to amplify the nitrogenase iron protein gene nifH from hydrothermal vent fluid. A total of 120 nifH sequences were obtained from four samples: a nitrogen-poor diffuse vent named marker 33 on Axial Volcano, sampled twice over a period of 1 year as its temperature decreased; a nitrogen-rich diffuse vent near Puffer on Endeavour Segment; and deep seawater with no detectable hydrothermal plume signal. Subseafloor nifH genes from marker 33 and Puffer are related to anaerobic clostridia and sulfate reducers. Other nifH genes unique to the vent samples include proteobacteria and divergent Archaea. All of the nifH genes from the deep-seawater sample are most closely related to the thermophilic, anaerobic archaeon Methanococcus thermolithotrophicus (77 to 83% amino acid similarity). These results provide the first genetic evidence of potential nitrogen fixers in hydrothermal vent environments and indicate that at least two sources contribute to the diverse assemblage of nifH genes detected in hydrothermal vent fluid: nifH genes from an anaerobic, hot subseafloor and nifH genes from cold, oxygenated deep seawater. PMID:12571018

  10. Phylogenetic diversity of nitrogenase (nifH) genes in deep-sea and hydrothermal vent environments of the Juan de Fuca Ridge.

    PubMed

    Mehta, Mausmi P; Butterfield, David A; Baross, John A

    2003-02-01

    The subseafloor microbial habitat associated with typical unsedimented mid-ocean-ridge hydrothermal vent ecosystems may be limited by the availability of fixed nitrogen, inferred by the low ammonium and nitrate concentrations measured in diffuse hydrothermal fluid. Dissolved N2 gas, the largest reservoir of nitrogen in the ocean, is abundant in deep-sea and hydrothermal vent fluid. In order to test the hypothesis that biological nitrogen fixation plays an important role in nitrogen cycling in the subseafloor associated with unsedimented hydrothermal vents, degenerate PCR primers were designed to amplify the nitrogenase iron protein gene nifH from hydrothermal vent fluid. A total of 120 nifH sequences were obtained from four samples: a nitrogen-poor diffuse vent named marker 33 on Axial Volcano, sampled twice over a period of 1 year as its temperature decreased; a nitrogen-rich diffuse vent near Puffer on Endeavour Segment; and deep seawater with no detectable hydrothermal plume signal. Subseafloor nifH genes from marker 33 and Puffer are related to anaerobic clostridia and sulfate reducers. Other nifH genes unique to the vent samples include proteobacteria and divergent Archaea. All of the nifH genes from the deep-seawater sample are most closely related to the thermophilic, anaerobic archaeon Methanococcus thermolithotrophicus (77 to 83% amino acid similarity). These results provide the first genetic evidence of potential nitrogen fixers in hydrothermal vent environments and indicate that at least two sources contribute to the diverse assemblage of nifH genes detected in hydrothermal vent fluid: nifH genes from an anaerobic, hot subseafloor and nifH genes from cold, oxygenated deep seawater. PMID:12571018

  11. The NeMO Explorer Web Site: Interactive Exploration of a Recent Submarine Eruption and Hydrothermal Vents, Axial Volcano, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Weiland, C.; Chadwick, W. W.; Embley, R. W.

    2001-12-01

    To help visualize the submarine volcanic landscape at NOAA's New Millennium Observatory (NeMO), we have created the NeMO Explorer web site: http://www.pmel.noaa.gov/vents/nemo/explorer.html. This web site takes visitors a mile down beneath the ocean surface to explore Axial Seamount, an active submarine volcano 300 miles off the Oregon coast. We use virtual reality to put visitors in a photorealistic 3-D model of the seafloor that lets them view hydrothermal vents and fresh lava flows as if they were really on the seafloor. At each of six virtual sites there is an animated tour and a 360o panorama in which users can view the volcanic landscape and see biological communities within a spatially accurate context. From the six sites there are hyperlinks to 50 video clips taken by a remotely operated vehicle. Each virtual site concentrates on a different topic, including the dynamics of the 1998 eruption at Axial volcano (Rumbleometer), high-temperature hydrothermal vents (CASM and ASHES), diffuse hydrothermal venting (Marker33), subsurface microbial blooms (The Pit), and the boundary between old and new lavas (Castle vent). In addition to exploring the region geographically, visitors can also explore the web site via geological concepts. The concepts gallery lets you quickly find information about mid-ocean ridges, hydrothermal vents, vent fauna, lava morphology, and more. Of particular interest is an animation of the January 1998 eruption, which shows the rapid inflation (by over 3 m) and draining of the sheet flow. For more info see Fox et al., Nature, v.412, p.727, 2001. This project was funded by NOAA's High Performance Computing and Communication (HPCC) and Vents Programs. Our goal is to present a representative portion of the vast collection of NOAA's multimedia imagery to the public in a way that is easy to use and understand. These data are particularly challenging to present because of their high data rates and low contextual information. The 3-D models create

  12. Continuing evolution of the Pacific-Juan de Fuca-North America slab window system-A trench-ridge-transform example from the Pacific Rim

    USGS Publications Warehouse

    McCrory, P.A.; Wilson, D.S.; Stanley, R.G.

    2009-01-01

    Many subduction margins that rim the Pacific Ocean contain complex records of Cenozoic slab-window volcanism combined with tectonic disruption of the continental margin. The series of slab windows that opened beneath California and Mexico starting about 28.5 Ma resulted from the death of a series of spreading ridge segments and led to piecewise destruction of a subduction regime. The timing and areal extent of the resultant slab-window volcanism provide constraints on models that depict the subsequent fragmentation and dispersal of the overlying continental margin. The initial Pioneer slab window thermally weakened the overlying western Transverse Ranges and California Borderlands region starting about 28.5 Ma. A second thermal pulse occurred in the same region starting about 19 Ma during growth of the Monterey slab window. This additional heating, combined with the capture of a partially subducted Monterey plate fragment by the Cocos plate, initiated the pulling apart and rotation of the adjacent continental margin. Similarly, the capture of Guadalupe and Magdalena plate fragments by the Pacific plate and initiation of the Guadalupe-Magdalena slab window about 12.5 Ma are coeval with Baja California pulling away from the Mexico continental margin, with the break along the Comondú arc, in crust already thermally weakened by about 10 My of volcanism. In coastal California, distributed crustal extension and subsidence accompanied the new transform plate boundary, and continued until the slab windows cooled and plate motion coalesced along a through-going system of strike-slip faults. The transform boundary continues to evolve, and forward modeling predicts an instability with the current configuration as a result of convergence between the Sierra Nevada and Peninsular Ranges batholiths, starting about 2 My in the future. The instability may be resolved by a shift in the locus of transform motion from the San Andreas fault to the eastern California shear zone, or by

  13. Volcanism and massive sulfide formation at a sedimented spreading center, Escanaba Trough, Gorda Ridge, northeast Pacific.

    USGS Publications Warehouse

    Morton, J.L.; Holmes, M.L.; Koski, R.A.

    1987-01-01

    Seismic-reflection profiles over the sediment-filled Escanaba Trough at the southern Gorda Ridge reveal a series of volcanic centers that pierce the sediment. The volcanic edifices are 3 to 6 km in diameter and are spaced at 15 to 20 km intervals along the axis of the trough. Composition and form of sulfide samples obtained from the bank suggest significant interaction between hydrothermal fluids and sediment at depth, and deposition of sulfide within the sediment pile.-from Authors

  14. Rare earth element geochemistry in cold-seep pore waters of Hydrate Ridge, northeast Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Himmler, Tobias; Haley, Brian A.; Torres, Marta E.; Klinkhammer, Gary P.; Bohrmann, Gerhard; Peckmann, Jörn

    2013-07-01

    The concentrations of rare earth elements (REEs), sulphate, hydrogen sulphide, total alkalinity, calcium, magnesium and phosphate were measured in shallow (<12 cm below seafloor) pore waters from cold-seep sediments on the northern and southern summits of Hydrate Ridge, offshore Oregon. Downward-decreasing sulphate and coevally increasing sulphide concentrations reveal sulphate reduction as dominant early diagenetic process from ~2 cm depth downwards. A strong increase of total dissolved REE (∑REE) concentrations is evident immediately below the sediment-water interface, which can be related to early diagenetic release of REEs into pore water resulting from the re-mineralization of particulate organic matter. The highest pore water ∑REE concentrations were measured close to the sediment-water interface at ~2 cm depth. Distinct shale-normalized REE patterns point to particulate organic matter and iron oxides as main REE sources in the upper ~2-cm depth interval. In general, the pore waters have shale-normalized patterns reflecting heavy REE (HREE) enrichment, which suggests preferential complexation of HREEs with carbonate ions. Below ~2 cm depth, a downward decrease in ∑REE correlates with a decrease in pore water calcium concentrations. At this depth, the anaerobic oxidation of methane (AOM) coupled to sulphate reduction increases carbonate alkalinity through the production of bicarbonate, which results in the precipitation of carbonate minerals. It seems therefore likely that the REEs and calcium are consumed during vast AOM-induced precipitation of carbonate in shallow Hydrate Ridge sediments. The analysis of pore waters from Hydrate Ridge shed new light on early diagenetic processes at cold seeps, corroborating the great potential of REEs to identify geochemical processes and to constrain environmental conditions.

  15. Biogeochemistry of dissolved methane and hydrogen within basement fluids of the sediment-buried Juan de Fuca Ridge flank at Borehole (CORKs) 1301A, 1362A and 1362B

    NASA Astrophysics Data System (ADS)

    Lin, H.; Cowen, J. P.; Olson, E. J.; Lilley, M. D.; Jungbluth, S.; Rappé, M.; Bowers, R.

    2012-12-01

    Hydrogen and methane are important electron donors in chemosynthesis-based ecosystmes. Within the deeply buried Juan de Fuca Ridge flank crustal biosphere, while oxygen and nitrate are exhausted, sulfate is still abundant. Coupled with sulfate, hydrogen and methane can yield energy to support life. In this work, we will present and discuss the hydrogen and methane concentrations of fluids collected via fluid delivery line that run exterior to the Integrated Ocean Drilling Project (IODP) Circulation Observatory Retrofit Kit (CORK) casing from basement depths to the seafloor outlet ports at sites 1301A, 1362A and 1362B. Carbon isotope values of methane will also be presented and discussed for 1301A samples. The three CORKs were installed to study horizontal and vertical circulation/mixing patterns. CORK 1362 is ~800 m north-northwest of CORK 1301B. CORK 1362 A and 1362B are ~200m apart. The fluid intake is ~50 m below sediment-basement interface (mbs) at CORK 1301A, 200 mbs at CORK 1362A and ~40 mbs at CORK 1362B. Despite their close proximities, the basement fluids from the three CORKs show some differences in their biogeochemical compositions, including their hydrogen and methane concentrations. Higher hydrogen (0.3-2 μM) and lower methane (1.5±0.2μM) concentrations are observed at CORK 1301A than at the other two sites. CORKs 1362A and 1362B have similar hydrogen concentrations (0.05±0.02 μM and 0.08±0.03 μM, respectively) but their methane concentrations differ significantly (6±0.4 μM and 13±1 μM, respectively) and are much higher than the methane concentrations (2-3 μM) in the sediment porewater collected near the sediment-basement interface, suggesting methane sources in situ within the basement environment. Abiotic production of hydrogen from basalt-seawater interaction has been observed in both field and lab studies (Stevens and McKinley, 2000). Thermodynamic calculations also show that the reaction of methane production from hydrogen is favorable

  16. Biogeochemistry of dissolved methane and hydrogen in basement fluids of the sediment-buried Juan de Fuca Ridge flank at Boreholes (CORKs) 1301A, 1362A and 1362B: methane isotopic compositions

    NASA Astrophysics Data System (ADS)

    Lin, H.; Cowen, J. P.; Olson, E. J.; Lilley, M. D.; Jungbluth, S.; Rappe, M. S.

    2013-12-01

    The ocean crust is the largest aquifer system on Earth. Within the sediment-buried 3.5 Myr basaltic crust of the eastern Juan de Fuca Ridge (JFR) flank, the circulating basement fluids have moderate temperature (~65°C) and potentially harbor a substantial subseafloor biosphere. With dissolved oxygen and nitrate exhausted, sulfate may serve as the major electron acceptor in this environment. This study aims to evaluate the availability and the biogeochemistry of two important electron donors, methane and hydrogen, for the subseafloor biosphere. Basement fluids were collected via stainless steel and ethylene-tetrafluoroethylene fluoropolymer (ETFE) fluid delivery lines associated with Integrated Ocean Drilling Program (IODP) Circulation Obviation Retrofit Kits (CORKs) that extend from basement depths to outlet ports at the seafloor. Three CORKs were visited; 1301A, 1362A and 1362B lie within 200 to 500 m of each other, and their fluid intakes lie at ~30, ~60, and ~50 m below the sediment-basement interface (mbs), respectively. In addition, CORK 1362A contains a second intake at a deep (~200 mbs) horizon. The basement fluids from the three CORKs contained significantly higher concentrations of methane (1.5-13μM) and hydrogen (0.05-1.1 μM) than in bottom seawater (0.002 and 0.0004, respectively), indicating that prevalence and availability of both methane and hydrogen as electron donors for the subseafloor biosphere. Thermodynamic calculations show that sulfate reduction coupled with either methane or hydrogen oxidation is energy yielding in the oceanic basement. The δ13C values of methane ranged from -43×1‰ to -58×0.3‰; the δ2H values of methane in CORKs 1301A, 1362A and 1362B fluids were 57×5‰, -262×2‰, -209×2‰, respectively. The isotopic compositions suggest that methane in the basement fluid is of biogenic origin. Interestingly, the δ2H value of methane in the CORK 1301A fluids is far more positive than that in other marine environments

  17. Regional characteristics of land use in Northeast and Southern Blue Ridge Province: Associations with acid rain effects on surface-water chemistry

    NASA Astrophysics Data System (ADS)

    Liegel, Leon; Cassell, David; Stevens, Donald; Shaffer, Paul; Church, Robbins

    1991-03-01

    The Direct/Delayed Response Project (DDRP) is one of several studies being conducted by the United States Environmental Protection Agency to assess risk to surface waters from acidic deposition in the eastern United States. In one phase of DDRP, land use, wetland, and forest cover data were collected for statistical samples of 145 Northeast lake and 35 Southern Blue Ridge Province stream watersheds in the United States. Land-use and other data then were extrapolated from individual to target watershed populations. Project statistical design allows summarization of results for various subsets of the target population. This article discusses results and implications of the land-use and land-cover characterization for both regions. Forest cover was the primary land use in both regions. In the Northeast, developed (agriculture and urban) land was positively associated with surface-water chemistry values for acid neutralizing capacity, Ca plus Mg, pH, and sulfate in the Pocono/Catskill subregion. Extensive wetlands and beaver activity occur in parts of the Northeast region, whereas topography limits wetland and riparian development in the Southern Blue Ridge Province. Northeast soils have low sulfate adsorption capacity, most watersheds are near sulfur steady state, and lake sulfate concentrations are controlled principally by levels of sulfur deposition. Net annual sulfur retention in Northeast watersheds is positively correlated with occurrence of wetlands and beaver impoundments. In contrast, most Southern Blue Ridge Province soils have high sulfate adsorption capacities, resulting in high net watershed sulfur retention. At the present time, stream sulfate concentrations and percent sulfur retention are controlled principally by soil chemical properties related to adsorption rather than atmospheric deposition and land use.

  18. Sea level Variability and Juan de Fuca Bathymetry

    NASA Astrophysics Data System (ADS)

    Huybers, P. J.; Boulahanis, B.; Proistosescu, C.; Langmuir, C. H.; Carbotte, S. M.; Katz, R. F.

    2015-12-01

    That deglaciation influences mid-ocean ridge volcanism is well established for Iceland, where depressurization associated with melting a ~2 km ice cap led to order of magnitude increases in volcanism during the last deglaciation. The case was also made that the more subtle ~100 m changes in sea level that accompany glacial cycles have identifiable implications for undersea mid-ocean ridge systems using both models and data from the Australian-Antarctic Ridge (Crowley et al., 2015). Sea level rising at ~1 cm/year during deglaciation leads to an expectation of ~10% decreases in melt production at ridges, given mantle upwelling rates of ˜3 cm/yr at intermediate spreading ridges and mantle density being ~3 times that of seawater. The implications of variations in melt production for bathymetry, however, involve numerous considerations, including whether melt signals are cancelled within the melt column, appreciably alter accretionary or fault processes, and have identifiable surface expressions. Further empirical assessment of bathymetry is thus useful for purposes of confirming patterns and constraining processes. Here we report on spectral analyses of bathymetry recently acquired from the Juan de Fuca ridge between 44°30'N and 45°15'N during the SeaVOICE expedition. Multibeam swath sonar data were acquired with an EM122 sonar insonfiying seafloor to crustal ages of ˜2 ma with 35 m spatial resolution. We examine (1.) the statistical significance of concentrations of bathymetric variability at the 100 ky, 41 ky, and 23 ky periods characteristic of late-Pleistocene sea level variability; (2.) whether sea level responses are primarily at 41 ky periods in crust accreted during the early Pleistocene, when global sea level variations were primarily at this period; and (3.) if sea level responses are superimposed on bathymetry variations or, instead, align with fault features. We also note that Juan de Fuca's proximity to the Cordilleran Ice Sheet implies that regional

  19. Magnetic Anomalies over the Mid-Atlantic Ridge near 27{degrees}N.

    PubMed

    Phillips, J D

    1967-08-25

    Ten magnetic profiles across the mid-Atlantic ridge near 27 degrees N show trends that are parallel to the ridge axis and symmetrical about the ridge axis. The configuration of magnetic bodies that could account for the pattern supports the Vine and Matthews hypothesis for the origin of magnetic anomalies over oceanic ridges. A polarity-reversal time scale inferred from models for sea-floor spreading in the Pacific-Antarctic ridge and radiometrically dated reversals of the geomagnetic field indicates a spreading rate of 1.25 centimeters per year during the last 6 million years and a rate of 1.65 centimeters per year between 6 and 10 million years ago. A similar analysis of more limited data over the mid-Atlantic ridge near 22 degrees N also indicates a change in the spreading rate. Here a rate of 1.4 centimeters per year appears to have been in effect during the last 5 million years; between 5 and 9 million years ago, an increased rate of 1.7 centimeters per year is indicated. The time of occurrence and relative magnitude of these changes in the spreading rate, about 5 to 6 million years ago and 18 to 27 percent, respectively, accords with the spreading rate change implied for the Juan de Fuca ridge in the northeast Pacific. PMID:17792827

  20. SEISMICITY AND VOLCANISM IN THE PACIFIC NORTHWEST: EVIDENCE FOR THE SEGMENTATION OF THE JUAN DE FUCA PLATE.

    USGS Publications Warehouse

    Weaver, Craig S.; Michaelson, Caryl A.

    1985-01-01

    The distributions of earthquakes and late Cenozoic and Quaternary volcanism in Washington and northern Oregon change markedly across two northeast-striking lines, one near Mount Rainier and one near Mount Hood. On the basis of these observations and a comparison with the Nazoa subduction zone, we propose that the Juan de Fuca subduction zone is divided into two segments. Landward of the coastal thrust zone, we suggest the Juan de Fuca plate dips more steeply beneath the southern segment than beneath the northern segment. Refs.

  1. Isotopic evidence for the incorporation of methane-derived carbon into foraminifera from modern methane seeps, Hydrate Ridge, Northeast Pacific

    NASA Astrophysics Data System (ADS)

    Hill, T. M.; Kennett, J. P.; Valentine, D. L.

    2004-11-01

    The presence of modern methane seeps at Hydrate Ridge, offshore Oregon, provide an opportunity to study the influence of methane seeps on the ecology and geochemistry of living foraminifera. A series of cores were collected from the southern summit of Hydrate Ridge in 2002. Samples were preserved and stained to determine the δ 13C composition of three species of live (stained) and dead benthic foraminifera: Uvigerina peregrina, Cibicidoides mckannai, and Globobulimina auriculata. Specimens were examined under light and Scanning Electron Microscopy (SEM) and exhibit no evidence of diagenesis or authigenic carbonate precipitation. Individual living foraminifera from seep sites recorded δ 13C values from -0.4‰ to -21.2‰, indicating the isotopic influence of high methane concentrations. Average δ 13C values (calculated from single specimens) range from -1.28 to -5.64‰ at seep sites, and -0.81 to -0.85‰ at a control (off seep) site. Two distinct seep environments, distinguished by the presence of microbial mats or clam fields, were studied to determine environmental influences on δ 13C values. Individual foraminifera from microbial mat sites exhibited more depleted δ 13C values than those from clam field sites. We interpret these differences as an effect of food source and/or symbiotic microbes on foraminiferal carbon isotopic values, acting to magnify the negative δ 13C values recorded via the DIC pool. No statistical difference was found between δ 13C values of live vs. dead specimens. This suggests that authigenic carbonate precipitation did not play a dominant role in the observed isotopic compositions. However, a few dead specimens with extremely negative δ 13C composition (<-12‰) do indicate potential evidence for an authigenic influence on the recorded δ 13C composition.

  2. Bimodal volcanism in northeast Puerto Rico and the Virgin Islands (Greater Antilles Island Arc): Genetic links with Cretaceous subduction of the mid-Atlantic ridge Caribbean spur

    NASA Astrophysics Data System (ADS)

    Jolly, Wayne T.; Lidiak, Edward G.; Dickin, Alan P.

    2008-07-01

    Bimodal extrusive volcanic rocks in the northeast Greater Antilles Arc consist of two interlayered suites, including (1) a predominantly basaltic suite, dominated by island arc basalts with small proportions of andesite, and (2) a silicic suite, similar in composition to small volume intrusive veins of oceanic plagiogranite commonly recognized in oceanic crustal sequences. The basaltic suite is geochemically characterized by variable enrichment in the more incompatible elements and negative chondrite-normalized HFSE anomalies. Trace element melting and mixing models indicate the magnitude of the subducted sediment component in Antilles arc basalts is highly variable and decreases dramatically from east to west along the arc. In the Virgin Islands, the sediment component ranges between< 0.5 to ˜ 1% in Albian rocks, and between ˜ 1 and 2% in succeeding Cenomanian to Campanian strata. In comparison, sediment proportions in central Puerto Rico range between 0.5 to 1.5% in the Albian to 2 to > 4% during the Cenomanian-Campanian interval. The silicic suite, consisting predominantly of rhyolites, is characterized by depleted Al 2O 3 (average < 16%), low Mg-number (molar Mg/Mg + Fe < 0.5), TiO 2 (< 1.0%), and Sr/Y (< 10), oceanic or arc-like Sr, Nd, and Pb isotope signatures, and by the presence of plagioclase. All of these features are consistent with an anatexic origin in gabbroic sources, of both oceanic and arc-related origin, within the sub-arc basement. The abundance of silicic lavas varies widely along the length of the arc platform. In the Virgin Islands on the east, rhyolites comprise up to 80% of Lower Albian strata (112 to 105 Ma), and about 20% in post-Albian strata (105 to 100 Ma). Farther west, in Puerto Rico, more limited proportions (< 20%) of silicic lavas were erupted. The systematic variation of both sediment flux and abundance of crustally derived silicic lavas are consistent with current tectonic models of Caribbean evolution involving approximately

  3. 33 CFR 80.1385 - Strait of Juan de Fuca.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Strait of Juan de Fuca. 80.1385... NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1385 Strait of Juan de Fuca. The 72 COLREGS shall apply on all waters of the Strait of Juan de Fuca....

  4. Vacuolate-attached filaments: highly productive Ridgeia piscesae epibionts at the Juan de Fuca hydrothermal vents.

    PubMed

    Kalanetra, Karen M; Nelson, Douglas C

    2010-01-01

    Vacuolate sulfur bacteria with high morphological similarity to vacuolate-attached filaments previously described from shallow hydrothermal vents (White Point, CA) were found at deep-sea hydrothermal vents. These filamentous bacteria grow in dense mats that cover surfaces and potentially provide a significant source of organic carbon where they occur. Vacuolate-attached filaments were collected near vents at the Clam Bed site of the Endeavour Segment of the Juan de Fuca Ridge and from the sediment surface at Escanaba Trough on the Gorda Ridge. A phylogenetic analysis comparing their 16S rRNA gene sequences to those collected from the shallow White Point site showed that all vacuolate-attached filament sequences form a monophyletic group within the vacuolate sulfur-oxidizing bacteria clade in the gamma proteobacteria. Abundance of the attached filaments was quantified over the length of the exterior surface of the tubes of Ridgeia piscesae worms collected from the Clam Bed site at Juan de Fuca yielding a per worm average of 0.070 ± 0.018 cm(3) (n = 4). In agreement with previous results for White Point filaments, anion measurements by ion chromatography showed no detectable internal nitrate concentrations above ambient seawater (n = 9). For one R. piscesae tube worm "bush" at the Easter Island vent site, potential gross epibiont productivity is estimated to be 15 to 45× the net productivity of the worms. PMID:24391244

  5. Shallow structure and surface wave propagation characteristics of the Juan de Fuca plate from seismic ambient noise

    NASA Astrophysics Data System (ADS)

    Tian, Y.; Shen, W.; Ritzwoller, M. H.

    2013-12-01

    Ambient noise cross-correlation analysis has been widely used to investigate the continental lithosphere, but the method has been applied much less to study the oceanic lithosphere due to the relative shortage of continuous ocean bottom seismic measurements. The Cascadia Initiative experiment possesses a total of 62 ocean bottom seismometers that spans much of the Juan de Fuca plate and provides data to investigate both the structure and evolution of the oceanic lithosphere near the Juan De Fuca ridge and the characteristics of surface waves and overtones propagating within the oceanic lithosphere. We produce ambient noise cross correlations for the first year of Cascadia OBS data for both the vertical and the horizontal components. The observed empirical Green's functions are first used to test the hypothesis that the near-ridge phase speeds can be described by a simple age-dependent formula, which we invert for an age-dependent shear wave speed model (Figure 1a). A shallow low shear velocity zone with a velocity minimum at about 20km depth is observed in Vsv and the lithosphere thickens with age faster than predicted by a half-space conductive cooling model (Figure 1b). To further understand the oceanic surface waves, we analyze the first higher mode Rayleigh waves that propagate within the Juan De Fuca plate and emerge on the North American continent and investigate the existence of radial anisotropy beneath the ridge by exploring the Rayleigh and Love wave Green's functions. The results of the study are summarized with the age-dependent shear velocity model along with some preliminary observations of both Love wave and higher mode Rayleigh waves.

  6. Juan de Fuca subducting plate geometry and intraslab seismicity

    NASA Astrophysics Data System (ADS)

    Medema, Guy Frederick

    The geometry of the subducting Juan de Fuca plate beneath the Olympic Peninsula of Western Washington is modeled using wide-angle P mP reflections off the slab Moho. Active-source reflection data collected from the 1998 WET SHIPS project were augmented with earthquake-source reflections to increase the spatial distribution of reflection points over the Juan de Fuca arch structure. Approximately 1100 WET SHIPS and 500 earthquake-source reflections were used in our inversion. PmP travel-times from active sources and PmP--P differential times from earthquakes sources were simultaneously inverted for slab-Moho depth, using a combination of finite-difference and 3-D ray-tracing methods. Results show a tighter arch structure than in previous models with the shallowest dipping portion (˜ 10° dip) concentrated directly beneath the Olympic Mountains. Comparison of our slab model to intraslab earthquake hypocenters reveals a southwest-northeast trending lineament of seismicity situated just beneath the subducted Moho in the slab mantle. We interpret this seismicity as the manifestation of a subducting pseudofault along which high levels of upper mantle hydration occurred prior to subduction. Most of the remaining intraslab seismicity is concentrated on the northern and southern flanks of the arch and is likely due to increased strain rates in these regions from the combined effect of slab arch and subsequent steepening of slab dip. Earthquakes in the northern region appear to occur above the slab Moho in the crust of the oceanic plate, while uncertainties in earthquake locations and 3-D velocities in the southern region prevent an unambiguous interpretation at this time. The southern patch is especially important as it contains 3 large (magnitude 6.5 to 7.1) earthquakes during that past 60 years, including the 2001, Mw 6.8, Nisqually earthquake. Earthquakes occurring between 45 and 65 km depth in these two regions also systematically produce an anomalous low

  7. Tracking fin whales in the northeast Pacific Ocean with a seafloor seismic network.

    PubMed

    Wilcock, William S D

    2012-10-01

    Ocean bottom seismometer (OBS) networks represent a tool of opportunity to study fin and blue whales. A small OBS network on the Juan de Fuca Ridge in the northeast Pacific Ocean in ~2.3 km of water recorded an extensive data set of 20-Hz fin whale calls. An automated method has been developed to identify arrival times based on instantaneous frequency and amplitude and to locate calls using a grid search even in the presence of a few bad arrival times. When only one whale is calling near the network, tracks can generally be obtained up to distances of ~15 km from the network. When the calls from multiple whales overlap, user supervision is required to identify tracks. The absolute and relative amplitudes of arrivals and their three-component particle motions provide additional constraints on call location but are not useful for extending the distance to which calls can be located. The double-difference method inverts for changes in relative call locations using differences in residuals for pairs of nearby calls recorded on a common station. The method significantly reduces the unsystematic component of the location error, especially when inconsistencies in arrival time observations are minimized by cross-correlation. PMID:23039436

  8. Hydrothermal plumes over spreading ridges and related deposits in the northeast Pacific Ocean: The East Pacific Rise near 11 degrees north and 21 degrees north, Explorer Ridge and J. Tuzo Wilson Seamounts

    SciTech Connect

    McConachy, T.F.

    1988-01-01

    Hydrothermal plumes emanating from hot springs over spreading ridges in the north east Pacific Ocean have been mapped and sampled using the submersible ALVIN and equipment deployed from surface ships. The geologic setting and polymetallic sulfides of the vent field producing the hydrothermal plume at 11{degree}N have also been examined. At 11{degree}N, two distinct metalliferous components are delivered to the intermediate to far-field from high temperature black smoker discharge as a result of the physical and chemical processes that occur in the lower 32 m of the plume. About 60 volume % of this material is estimated to settle within a 6-km-radius of the vent field, based on the results of SEM-IPS grain-size analyses and their application to a published particle settling model. The second component delivered to the far-field consists of the remaining 40 volume % of fine-grained sulfides and non-sulfides, 10% of dissolved Fe which will eventually precipitate as oxyhydroxides, and {>=} 80% of the hydrothermally injected Mn, Si, and probably Ba. At 21{degree} N by contrast, only 20 volume % of the smoke particles is conservatively estimated to settle within a 8-km-radius of the NGS vent due to their finer grain size and a higher terminal height of the buoyant hydrothermal plume.

  9. Seismic velocity structure of the Juan de Fuca and Gorda plates revealed by a joint inversion of ambient noise and regional earthquakes

    NASA Astrophysics Data System (ADS)

    Gao, Haiying

    2016-05-01

    The crust and upper mantle seismic structure, spanning from the Juan de Fuca and Gorda spreading centers to the Cascade back arc, is imaged with full-wave propagation simulation and a joint inversion of ambient noise and regional earthquake recordings. The spreading centers have anomalously low shear wave velocity beneath the oceanic lithosphere. Around the Cobb axial seamount, we observe a low-velocity anomaly underlying a relatively thin oceanic lithosphere, indicating its influence on the Juan de Fuca ridge. The oceanic Moho is clearly defined by a P velocity increase from 6.3 km/s to 7.5 km/s at about 6 km depth beneath the seafloor. The thickness of the oceanic plates is less than 40 km prior to subduction, and the structure of the oceanic lithosphere varies both along strike and along dip. Farther landward, very low velocity anomalies are observed above the plate interface along the Cascade fore arc, indicative of subducted sediments.

  10. THE STRAIT OF JUAN DE FUCA INTERTIDAL AND SUBTIDAL BENTHOS

    EPA Science Inventory

    This report presents the second year results of an intertidal and shallow subtidal benthic sampling program at ten sites along the Washington State coast of the Strait of Juan de Fuca. The purpose of this program was to provide a quantitative characterization of the marine, shall...

  11. Offshore finfish mariculture in the Strait of Juan de Fuca

    SciTech Connect

    Rensel, Jack; Kiefer, Dale; Forster, John R.; Woodruff, Dana L.; Evans, Nathan R.

    2007-10-07

    Finfish mariculture has existed in the U.S. Pacific Northwest for over thirty years, but for the past 15 years most effort has focused on culture of Atlantic salmon in protected, inshore cage sites. The Strait of Juan de Fuca (the "Strait") is a large area with relatively sparce shoreline development and several apparent advantages for mariculture using offshore technology.

  12. Recent movements of the Juan de Fuca Plate System

    NASA Astrophysics Data System (ADS)

    1984-08-01

    Analysis of the magnetic anomalies of the Juan de Fuca plate system allows instantaneous poles of rotation relative to the Pacific plate to be calculated from 7 Ma to the present. By combining these with global solutions for Pacific America and ``absolute'' (relative to hot spot) motions, a plate motion sequence can be constructed. This sequence shows that both absolute motions and motions relative to America are characterized by slower velocities where younger and more buoyant material enters the convergence zone: ``pivoting subduction.'' The resistance provided by the youngest portion of the Juan de Fuca plate apparently resulted in its detachment at 4 Ma as the independent Explorer plate. In relation to the hot spot framework, this plate almost immediately began to rotate clockwise around a pole close to itself such that its translational movement into the mantle virtually ceased. After 4 Ma the remainder of the Juan de Fuca plate adjusted its motion in response to the fact that the youngest material entering the subduction zone was not to the south. Differences in seismicity and recent uplift between northern and southern Vancourver Island may reflect a distinction in tectonic style between the ``normal'' subduction of the Juan de Fuca plate to the south and a complex ``underplating occurring as the Explorer plate is overridden by the continent. The history of the Explorer plate may exemplify the conditins under which the self-driving forces of small subducting plates are overcome by the influence of larger, adjacent plates. The recent rapid migration of the absolute pole of rotation of the Juan de Fuca plate toward the plate suggests that it, too, may be nearing this condition.

  13. Recent movements of the Juan de Fuca Plate System

    NASA Astrophysics Data System (ADS)

    Riddihough, Robin

    1984-08-01

    Analysis of the magnetic anomalies of the Juan de Fuca plate system allows instantaneous poles of rotation relative to the Pacific plate to be calculated from 7 Ma to the present. By combining these with global solutions for Pacific/America and "absolute" (relative to hot spot) motions, a plate motion sequence can be constructed. This sequence shows that both absolute motions and motions relative to America are characterized by slower velocities where younger and more buoyant material enters the convergence zone: "pivoting subduction." The resistance provided by the youngest portion of the Juan de Fuca plate apparently resulted in its detachment at 4 Ma as the independent Explorer plate. In relation to the hot spot framework, this plate almost immediately began to rotate clockwise around a pole close to itself such that its translational movement into the mantle virtually ceased. After 4 Ma the remainder of the Juan de Fuca plate adjusted its motion in response to the fact that the youngest material entering the subduction zone was now to the south. Differences in seismicity and recent uplift between northern and southern Vancouver Island may reflect a distinction in tectonic style between the "normal" subduction of the Juan de Fuca plate to the south and a complex "underplating" occurring as the Explorer plate is overridden by the continent. The history of the Explorer plate may exemplify the conditions under which the self-driving forces of small subducting plates are overcome by the influence of larger, adjacent plates. The recent rapid migration of the absolute pole of rotation of the Juan de Fuca plate toward the plate suggests that it, too, may be nearing this condition.

  14. The importance of hydrothermal venting to water-column secondary production in the northeast Pacific

    NASA Astrophysics Data System (ADS)

    Burd, Brenda J.; Thomson, Richard E.

    2015-11-01

    The purpose of this study is to show that seafloor hydrothermal venting in the open northeast Pacific Ocean has a marked impact on secondary biomass and production within the overlying water column. Specifically, we use net tows and concurrently measured acoustic backscatter data collected over six summers to examine the effects of hydrothermal venting from the Endeavour Segment of Juan de Fuca Ridge on macro-zooplankton biomass and production throughout the entire 2000 m depth range. Previous research shows that ontogenetic diapausing migrators and their predators from the upper ocean aggregate above the neutrally buoyant plumes in summer and resume feeding on plume and bottom upwelled particles, resulting in increased zooplankton reproductive output to the upper ocean. Within the limitations of our sampling methodology, net tows reveal a statistically significant exponential decline in total water-column biomass with increasing lateral distance from the vent fields. The acoustic backscatter data show a similar decline, but only below 800 m depth. Near-surface biomass was highly variable throughout the region, but values near vents consistently ranged higher than summer values found elsewhere in the offshore northeast Pacific. Water-column biomass was similar in magnitude above and below 800 m depth throughout the region. Because epiplume biomass can be advected a considerable distance from vent fields, biomass enhancement of the water column from hydrothermal venting may extend considerable distances to the west and northwest of the vent sites, in the prevailing directions of the subsurface flow. Based on the extensive acoustic Doppler current profiler (ADCP) data collected, and the strong correlation between zooplankton production derived from net sample biomass and acoustic backscatter intensity, we estimate that daily macro-zooplankton production in the upper 400 m of the water column within 10 km of the vent fields averages approximately 16% of photosynthetic

  15. 33 CFR 110.229 - Straits of Juan de Fuca, Wash.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Straits of Juan de Fuca, Wash. 110.229 Section 110.229 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY ANCHORAGES ANCHORAGE REGULATIONS Anchorage Grounds § 110.229 Straits of Juan de Fuca, Wash. (a)...

  16. 33 CFR 167.1312 - In the Strait of Juan de Fuca: Southern lanes.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...: Southern lanes. 167.1312 Section 167.1312 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Southern lanes. In the southern lanes of the Strait of Juan de Fuca, the following are...′ W 48°10.99′ N 123°24.84′ W (b) A traffic lane for northbound traffic between the separation zone...

  17. 33 CFR 167.1311 - In the Strait of Juan de Fuca: Western lanes.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...: Western lanes. 167.1311 Section 167.1311 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Western lanes. In the western lanes of the Strait of Juan de Fuca, the following are established...′ W (b) A traffic lane for north-westbound traffic. (1) The traffic lane is established between...

  18. 33 CFR 167.1313 - In the Strait of Juan de Fuca: Northern lanes.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...: Northern lanes. 167.1313 Section 167.1313 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Northern lanes. In the northern lanes of the Strait of Juan de Fuca, the following are...′ W (b) A traffic lane for southbound traffic between the separation zone and a line connecting...

  19. 33 CFR 167.1312 - In the Strait of Juan de Fuca: Southern lanes.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...: Southern lanes. 167.1312 Section 167.1312 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Southern lanes. In the southern lanes of the Strait of Juan de Fuca, the following are...′ W 48°10.99′ N 123°24.84′ W (b) A traffic lane for northbound traffic between the separation zone...

  20. 33 CFR 167.1314 - In the Strait of Juan de Fuca: Eastern lanes.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...: Eastern lanes. 167.1314 Section 167.1314 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Eastern lanes. In the eastern lanes of the Strait of Juan de Fuca, the following are established...′ W (b) A traffic lane for westbound traffic between the separation zone and a line connecting...

  1. 33 CFR 167.1311 - In the Strait of Juan de Fuca: Western lanes.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...: Western lanes. 167.1311 Section 167.1311 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Western lanes. In the western lanes of the Strait of Juan de Fuca, the following are established...′ W (b) A traffic lane for north-westbound traffic. (1) The traffic lane is established between...

  2. 33 CFR 167.1313 - In the Strait of Juan de Fuca: Northern lanes.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...: Northern lanes. 167.1313 Section 167.1313 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Northern lanes. In the northern lanes of the Strait of Juan de Fuca, the following are...′ W (b) A traffic lane for southbound traffic between the separation zone and a line connecting...

  3. 33 CFR 167.1313 - In the Strait of Juan de Fuca: Northern lanes.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...: Northern lanes. 167.1313 Section 167.1313 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Northern lanes. In the northern lanes of the Strait of Juan de Fuca, the following are...′ W (b) A traffic lane for southbound traffic between the separation zone and a line connecting...

  4. 33 CFR 167.1311 - In the Strait of Juan de Fuca: Western lanes.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...: Western lanes. 167.1311 Section 167.1311 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Western lanes. In the western lanes of the Strait of Juan de Fuca, the following are established...′ W (b) A traffic lane for north-westbound traffic. (1) The traffic lane is established between...

  5. 33 CFR 167.1314 - In the Strait of Juan de Fuca: Eastern lanes.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...: Eastern lanes. 167.1314 Section 167.1314 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Eastern lanes. In the eastern lanes of the Strait of Juan de Fuca, the following are established...′ W (b) A traffic lane for westbound traffic between the separation zone and a line connecting...

  6. 33 CFR 167.1314 - In the Strait of Juan de Fuca: Eastern lanes.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...: Eastern lanes. 167.1314 Section 167.1314 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Eastern lanes. In the eastern lanes of the Strait of Juan de Fuca, the following are established...′ W (b) A traffic lane for westbound traffic between the separation zone and a line connecting...

  7. 33 CFR 167.1311 - In the Strait of Juan de Fuca: Western lanes.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...: Western lanes. 167.1311 Section 167.1311 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Western lanes. In the western lanes of the Strait of Juan de Fuca, the following are established...′ W (b) A traffic lane for north-westbound traffic. (1) The traffic lane is established between...

  8. 33 CFR 167.1314 - In the Strait of Juan de Fuca: Eastern lanes.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...: Eastern lanes. 167.1314 Section 167.1314 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Eastern lanes. In the eastern lanes of the Strait of Juan de Fuca, the following are established...′ W (b) A traffic lane for westbound traffic between the separation zone and a line connecting...

  9. 33 CFR 167.1312 - In the Strait of Juan de Fuca: Southern lanes.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...: Southern lanes. 167.1312 Section 167.1312 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Southern lanes. In the southern lanes of the Strait of Juan de Fuca, the following are...′ W 48°10.99′ N 123°24.84′ W (b) A traffic lane for northbound traffic between the separation zone...

  10. 33 CFR 167.1313 - In the Strait of Juan de Fuca: Northern lanes.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...: Northern lanes. 167.1313 Section 167.1313 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Northern lanes. In the northern lanes of the Strait of Juan de Fuca, the following are...′ W (b) A traffic lane for southbound traffic between the separation zone and a line connecting...

  11. 33 CFR 167.1312 - In the Strait of Juan de Fuca: Southern lanes.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...: Southern lanes. 167.1312 Section 167.1312 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Fuca: Southern lanes. In the southern lanes of the Strait of Juan de Fuca, the following are...′ W 48°10.99′ N 123°24.84′ W (b) A traffic lane for northbound traffic between the separation zone...

  12. Physical characteristics of the Endeavour Ridge hydrothermal plume during July 1988

    NASA Astrophysics Data System (ADS)

    Thomson, Richard E.; Delaney, John R.; McDuff, Russell E.; Janecky, David R.; McClain, James S.

    1992-06-01

    We conducted CTD-transmissometer tows from 8 to 26 July, 1988 within 15 km of the central hydrothermal vent site ( ≈ 47°57'N, 129°06'W) on the Endeavour segment of Juan de Fuca Ridge. Anomalies of temperature, salinity and light attenuation reveal possible new vent sites 4 and 8 km northeast and 6 km south of the central vent site. As a result of widespread plume dispersion, background values of potential temperature, salinity and light attenuation below the 1900 m depth exceeded those for "pristine" ambient waters by 0.05°C, 0.05 psu and 0.03 m -1, respectively. Maximum plume anomalies relative to the background waters were of the order of 0.10°C, 0.010 psu and 0.10 m -1 at core depths of 2000-2050 m. Heat and salt anomalies were detectable more than 5 km from the central vent site whereas light attenuation (particle) anomalies were confined to within 2.5 km of the vent site. Based on the background water property anomalies and moored current meter records, the mean (time-averaged) heat fluxes for the survey region were+2.3(±1.5) × 10 8 W in the along-ridge direction (20°T) and-7.7(±4.7) × 10 8 W in the cross-ridge direction (110°T). Mean along- and cross-ridge salt fluxes were+7(±5)and-25(±15)kg s -1; mean particle fluxes were+0.09(±0.06)and-0.29(±0.18)kg s -1. Estimates of the instantaneous fluxes derived from coincident current and plume measurements indicate that heat fluxes from the central vent field may have been as high as1.2(±0.6)×10 10 W and corresponding particulate fluxes as high as6(±3)kg s -1.

  13. Cabled-observatory Regional Circulation Moorings on the Endeavour segment of the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Mihaly, S. F.

    2011-12-01

    In September of 2010, one of four moorings was deployed on the Endeavour node of the NEPTUNE Canada cabled-observatory network. The installation included the laying of a 7km cable from the node to the mooring site in the axial valley about 3km north of the Main Endeavour Vent Field over extraordinary bathymetry. This September, three more cables and secondary junction boxes will be deployed to support the three additional moorings that complete the regional circulation array. The cable-laying is facilitated by the Canadian Scientific Submersible Facility's ROV ROPOS and a remotely operated cable-laying system, whereas the actual deployment of the moorings is a two ship operation. The CCGS John P. Tully lowers the mooring anchor first, while the RV Thomas G. Thompson supports the ROV operations which navigate the mooring to underwater mateable cable end. Precise navigation is needed because there are few areas suitable for placement of the junction boxes. Scientifically, the moorings are designed and located to best constrain the hydrothermally driven circulation within the rift valley, the regional circulation can then be used as a proxy measurement for hydrothermal fluxes. Each mooring carries a current meter/ ctd pair at 4, 50, 125, and 200m, with an upward looking ADCP at 250m. The northern moorings are located between the Hi-Rise and Salty Dawg fields about 700m apart in the ~1km wide rift valley and the southern moorings are located south of the Mothra vent field. Here we present initial results from the four mooring array.

  14. Geologic history of the summit of Axial Seamount, Juan de Fuca Ridge

    USGS Publications Warehouse

    Clague, David A.; Dreyer, Brian M; Paduan, Jennifer B; Martin, Julie F; Chadwick, William W Jr; Caress, David W; Portner, Ryan A; Guilderson, Thomas P.; McGann, Mary; Thomas, Hans; Butterfield, David A; Embley, Robert W

    2013-01-01

    Multibeam (1 m resolution) and side scan data collected from an autonomous underwater vehicle, and lava samples, radiocarbon-dated sediment cores, and observations of flow contacts collected by remotely operated vehicle were combined to reconstruct the geologic history and flow emplacement processes on Axial Seamount's summit and upper rift zones. The maps show 52 post-410 CE lava flows and 20 precaldera lava flows as old as 31.2 kyr, the inferred age of the caldera. Clastic deposits 1–2 m thick accumulated on the rims postcaldera. Between 31 ka and 410 CE, there are no known lava flows near the summit. The oldest postcaldera lava (410 CE) is a pillow cone SE of the caldera. Two flows erupted on the W rim between ∼800 and 1000 CE. From 1220 to 1300 CE, generally small eruptions of plagioclase phyric, depleted, mafic lava occurred in the central caldera and on the east rim. Larger post-1400 CE eruptions produced inflated lobate flows of aphyric, less-depleted, and less mafic lava on the upper rift zones and in the N and S caldera. All caldera floor lava flows, and most uppermost rift zone flows, postdate 1220 CE. Activity shifted from the central caldera to the upper S rift outside the caldera, to the N rift and caldera floor, and then to the S caldera and uppermost S rift, where two historical eruptions occurred in 1998 and 2011. The average recurrence interval deduced from the flows erupted over the last 800 years is statistically identical to the 13 year interval between historical eruptions.

  15. Geologic history of the summit of Axial Seamount, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Clague, David A.; Dreyer, Brian M.; Paduan, Jennifer B.; Martin, Julie F.; Chadwick, William W.; Caress, David W.; Portner, Ryan A.; Guilderson, Thomas P.; McGann, Mary L.; Thomas, Hans; Butterfield, David A.; Embley, Robert W.

    2013-10-01

    Multibeam (1 m resolution) and side scan data collected from an autonomous underwater vehicle, and lava samples, radiocarbon-dated sediment cores, and observations of flow contacts collected by remotely operated vehicle were combined to reconstruct the geologic history and flow emplacement processes on Axial Seamount's summit and upper rift zones. The maps show 52 post-410 CE lava flows and 20 precaldera lava flows as old as 31.2 kyr, the inferred age of the caldera. Clastic deposits 1-2 m thick accumulated on the rims postcaldera. Between 31 ka and 410 CE, there are no known lava flows near the summit. The oldest postcaldera lava (410 CE) is a pillow cone SE of the caldera. Two flows erupted on the W rim between ˜800 and 1000 CE. From 1220 to 1300 CE, generally small eruptions of plagioclase phyric, depleted, mafic lava occurred in the central caldera and on the east rim. Larger post-1400 CE eruptions produced inflated lobate flows of aphyric, less-depleted, and less mafic lava on the upper rift zones and in the N and S caldera. All caldera floor lava flows, and most uppermost rift zone flows, postdate 1220 CE. Activity shifted from the central caldera to the upper S rift outside the caldera, to the N rift and caldera floor, and then to the S caldera and uppermost S rift, where two historical eruptions occurred in 1998 and 2011. The average recurrence interval deduced from the flows erupted over the last 800 years is statistically identical to the 13 year interval between historical eruptions.

  16. Juan de Fuca plate: Aseismic subduction at 1. 8 cm/yr

    SciTech Connect

    Acharya, H.

    1981-11-01

    Volcanic activity in the Cascades in historic times suggests that the Juan de Fuca plate is underthrusting aseismically at about 1.8 cm/yr. This rate of underthrusting is identical to the rate computed from sediment studies.

  17. Pole of rotating analysis of present-day Juan de Fuca plate motion

    NASA Technical Reports Server (NTRS)

    Nishimura, C.; Wilson, D. S.; Hey, R. N.

    1984-01-01

    Convergence rates between the Juan de Fuca and North American plates are calculated by means of their relative, present-day pole of rotation. A method of calculating the propagation of errors in addition to the instantaneous poles of rotation is also formulated and applied to determine the Euler pole for Pacific-Juan de Fuca. This pole is vectorially added to previously published poles for North America-Pacific and 'hot spot'-Pacific to obtain North America-Juan de Fuca and 'hot spot'-Juan de Fuca, respectively. The errors associated with these resultant poles are determined by propagating the errors of the two summed angular velocity vectors. Under the assumption that hot spots are fixed with respect to a mantle reference frame, the average absolute velocity of the Juan de Puca plate is computed at approximately 15 mm/yr, thereby making it the slowest-moving of the oceanic plates.

  18. 247. Axial Parkway alignment along ridge top. Note the open ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    247. Axial Parkway alignment along ridge top. Note the open vistas to either side of the roadway. These are maintained through vegetation management. The wood guide rail is a primary safety feature. View is to the northeast. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  19. Nature and extent of electrogenic microbial communities recovered from Juan de Fuca hydrothermal sulfides

    NASA Astrophysics Data System (ADS)

    Girguis, P. R.; Nielsen, M. E.

    2011-12-01

    Microbes have evolved a variety of metabolic strategies to survive in anaerobic environments, including extracellular electron transfer (EET). Here we present laboratory and in situ experiments revealing that hydrothermal vent microbes employ and depend upon EET to access spatially remote oxidants via semi-conductive pyrite. To simulate the physical and electrochemical conditions in vent sulfides, we constructed a two-chamber flow-through bioelectrochemical reactor in which a pyrite electrode was enclosed in one chamber and subject to simulated hydrothermal conditions. Electroactive biofilms formed solely on pyrite in electrical continuity with oxygenated water. Phylogenetic and metagenomic analyses revealed a diversity of autotrophic and heterotrophic archaea and bacteria, markedly different in composition from the control (pyrite without electrical continuity). To further characterize this phenomenon, we deployed a bioelectrochemical experiment in situ at the hydrothermal vent sulfide "Roane" (2200 m water depth, at the Mothra hydrothermal field, Juan de Fuca ridge). A graphite anode was inserted into a borehole drilled into the base of a hydrothermal sulfide, and connected through a potentiostat to a carbon-fiber cathode on the outside of the vent structure. The in situ experiment produced sustained current and enriched for a distinct microbial community likely associated with EET. The data presented herein reveal the nature and extent of microbial communities that use conductive minerals such as pyrite, though fully reduced, to facilitate the reduction of spatially remote oxidants while maintaining chemical discontinuity. Thus EET, by enabling sustained access to terminal electron acceptors while maintaining the functioning of strictly anaerobic metabolisms, may alleviate the limitations commonly associated with anaerobic environs, namely the depletion of oxidants.

  20. p53 directly regulates the glycosidase FUCA1 to promote chemotherapy-induced cell death.

    PubMed

    Baudot, Alice D; Crighton, Diane; O'Prey, Jim; Somers, Joanna; Sierra Gonzalez, Pablo; Ryan, Kevin M

    2016-09-01

    p53 is a central factor in tumor suppression as exemplified by its frequent loss in human cancer. p53 exerts its tumor suppressive effects in multiple ways, but the ability to invoke the eradication of damaged cells by programmed cell death is considered a key factor. The ways in which p53 promotes cell death can involve direct activation or engagement of the cell death machinery, or can be via indirect mechanisms, for example though regulation of ER stress and autophagy. We present here another level of control in p53-mediated tumor suppression by showing that p53 activates the glycosidase, FUCA1, a modulator of N-linked glycosylation. We show that p53 transcriptionally activates FUCA1 and that p53 modulates fucosidase activity via FUCA1 up-regulation. Importantly, we also report that chemotherapeutic drugs induce FUCA1 and fucosidase activity in a p53-dependent manner. In this context, while we found that over-expression of FUCA1 does not induce cell death, RNAi-mediated knockdown of endogenous FUCA1 significantly attenuates p53-dependent, chemotherapy-induced apoptotic death. In summary, these findings add an additional component to p53s tumor suppressive response and highlight another mechanism by which the tumor suppressor controls programmed cell death that could potentially be exploited for cancer therapy. PMID:27315169

  1. p53 directly regulates the glycosidase FUCA1 to promote chemotherapy-induced cell death

    PubMed Central

    Baudot, Alice D.; Crighton, Diane; O'Prey, Jim; Somers, Joanna; Sierra Gonzalez, Pablo; Ryan, Kevin M.

    2016-01-01

    ABSTRACT p53 is a central factor in tumor suppression as exemplified by its frequent loss in human cancer. p53 exerts its tumor suppressive effects in multiple ways, but the ability to invoke the eradication of damaged cells by programmed cell death is considered a key factor. The ways in which p53 promotes cell death can involve direct activation or engagement of the cell death machinery, or can be via indirect mechanisms, for example though regulation of ER stress and autophagy. We present here another level of control in p53-mediated tumor suppression by showing that p53 activates the glycosidase, FUCA1, a modulator of N-linked glycosylation. We show that p53 transcriptionally activates FUCA1 and that p53 modulates fucosidase activity via FUCA1 up-regulation. Importantly, we also report that chemotherapeutic drugs induce FUCA1 and fucosidase activity in a p53-dependent manner. In this context, while we found that over-expression of FUCA1 does not induce cell death, RNAi-mediated knockdown of endogenous FUCA1 significantly attenuates p53-dependent, chemotherapy-induced apoptotic death. In summary, these findings add an additional component to p53s tumor suppressive response and highlight another mechanism by which the tumor suppressor controls programmed cell death that could potentially be exploited for cancer therapy. PMID:27315169

  2. Metopic ridge

    MedlinePlus

    ... infant is made up of bony plates. The gaps between the plates allow for growth of the skull. The places where these plates connect are called sutures or suture lines. They do not fully close until the 2nd or 3rd year of life. A metopic ridge occurs when the ...

  3. 33 CFR 334.1180 - Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area. 334.1180 Section 334.1180 Navigation and Navigable... REGULATIONS § 334.1180 Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area. (a)...

  4. 33 CFR 334.1180 - Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area. 334.1180 Section 334.1180 Navigation and Navigable... REGULATIONS § 334.1180 Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area. (a)...

  5. 33 CFR 334.1180 - Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area. 334.1180 Section 334.1180 Navigation and Navigable... REGULATIONS § 334.1180 Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area. (a)...

  6. 33 CFR 334.1180 - Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area. 334.1180 Section 334.1180 Navigation and Navigable... REGULATIONS § 334.1180 Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area. (a)...

  7. 33 CFR 334.1180 - Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area. 334.1180 Section 334.1180 Navigation and Navigable... REGULATIONS § 334.1180 Strait of Juan de Fuca, Wash.; air-to-surface weapon range, restricted area. (a)...

  8. Novel p53 target gene FUCA1 encodes a fucosidase and regulates growth and survival of cancer cells.

    PubMed

    Ezawa, Issei; Sawai, Yuichiro; Kawase, Tatsuya; Okabe, Atsushi; Tsutsumi, Shuichi; Ichikawa, Hitoshi; Kobayashi, Yuka; Tashiro, Fumio; Namiki, Hideo; Kondo, Tadashi; Semba, Kentaro; Aburatani, Hiroyuki; Taya, Yoichi; Nakagama, Hitoshi; Ohki, Rieko

    2016-06-01

    The tumor suppressor p53 functions by inducing the transcription of a collection of target genes. We previously attempted to identify p53 target genes by microarray expression and ChIP-sequencing analyses. In this study, we describe a novel p53 target gene, FUCA1, which encodes a fucosidase. Although fucosidase, α-l-1 (FUCA1) has been reported to be a lysosomal protein, we detected it outside of lysosomes and observed that its activity is highest at physiological pH. As there is a reported association between fucosylation and tumorigenesis, we investigated the potential role of FUCA1 in cancer. We found that overexpression of FUCA1, but not a mutant defective in enzyme activity, suppressed the growth of cancer cells and induced cell death. Furthermore, we showed that FUCA1 reduced fucosylation and activation of epidermal growth factor receptor, and concomitantly suppressed epidermal growth factor signaling pathways. FUCA1 loss-of-function mutations are found in several cancers, its expression is reduced in cancers of the large intestine, and low FUCA1 expression is associated with poorer prognosis in several cancers. These results show that protein defucosylation mediated by FUCA1 is involved in tumor suppression. PMID:26998741

  9. 46 CFR 7.145 - Strait of Juan de Fuca, Haro Strait and Strait of Georgia WA.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Strait of Juan de Fuca, Haro Strait and Strait of Georgia WA. 7.145 Section 7.145 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES APPLICABLE TO THE PUBLIC BOUNDARY LINES Pacific Coast § 7.145 Strait of Juan de Fuca, Haro Strait and...

  10. Multi-mode conversion imaging of the subducted Gorda and Juan de Fuca plates below the North American continent

    NASA Astrophysics Data System (ADS)

    Tauzin, Benoit; Bodin, Thomas; Debayle, Eric; Perrillat, Jean-Philippe; Reynard, Bruno

    2016-04-01

    Receiver function analysis and seismic tomography show tectonic structures dipping eastward in the mantle below the Cascadia volcanic arc (western US) that have been related to the subduction of the Gorda and Juan de Fuca oceanic micro-plates. Inconsistencies in the dip angle and depth extent of the slab between the two methods undermine the interpretation of the structure and processes at work. Receiver function imaging is biased by multiple reflection phases that interfere with converted phases, and produce spurious discontinuities in images. Here, we correct the interference using a multiple mode conversion imaging technique that efficiently removes artifacts under dipping structures. The method has the advantage of being applicable to large aperture arrays, and can image large-scale structures down to the transition zone. With this approach, the interfaces between the subducting and overriding plates and the oceanic Moho are imaged at shallow depths (<120 km) with a dip angle of ∼20°, consistently with former studies. In addition, several important features are imaged with the present method. Faint converters located between 100 and 400 km depth in the mantle wedge, and strong sub-horizontal seismic scatterers near 160 km depth, may highlight dehydration and metasomatism processes in the Cascadia subduction zone. A discontinuity located at ∼15 km depth in the lithospheric mantle of the subducted plates and associated with a negative impedance contrast is interpreted as the fossil fabric of the plates acquired at the spreading ridges.

  11. Estuarine versus transient flow regimes in Juan de Fuca Strait

    NASA Astrophysics Data System (ADS)

    Thomson, Richard E.; MiháLy, Steven F.; Kulikov, Evgueni A.

    2007-09-01

    Residual currents in Juan de Fuca Strait are observed to switch between two fundamental states: estuarine and transient. The estuarine regime, which prevails roughly 90% of the time in summer and 55% of the time in winter, has a fortnightly modulated, three-layer structure characterized by strong (˜50 cm s-1) outflow above 60 ± 15 m depth, moderate (˜25 cm s-1) inflow between 60 and 125 m depth, and weak (˜10 cm s-1) inflow below 125 ± 10 m depth. Rotation increases the upper layer depth by 40 m on the northern side of the channel and upwelling-favorable coastal winds augment inflow in the bottom layer by as much as 5 cm s-1. Rotation, combined with modulation of the estuarine currents by tidal mixing in the eastern strait, leads to fortnightly variability in the along-channel velocity and cross-channel positioning of the core flow regions. Transient flows, which occur roughly 10% of the time in summer and 45% of the time in winter, are rapidly evolving, horizontally and vertically sheared "reversals" in the estuarine circulation generated during poleward wind events along the outer coast. Major events can persist for several weeks, force a net inward transport, and give rise to an O(10) km wide, surface-intensified, O(100) cm s-1 inflow along the southern (Olympic Peninsula) boundary of the strait. This "Olympic Peninsula Countercurrent" is typically accompanied by an abrupt decrease in salinity, indicating that it is a buoyancy flow originating with low-density water on the northern Washington shelf.

  12. EFFECTS OF EXPERIMENTAL OILING ON RECOVERY OF STRAIT OF JUAN DE FUCA INTERTIDAL HABITATS

    EPA Science Inventory

    Experimental studies of the effects of Prudhoe Bay crude oil on the recovery of inter-tidal infauna and epifauna were conducted in the Strait of Juan de Fuca region of Washington State. The studies experimentally evaluated the effect of oil treatment, site, substrate type, season...

  13. SYNTHESIS OF BIOLOGICAL DATA FROM THE STRAIT OF JUAN DE FUCA AND NORTHERN PUGET SOUND

    EPA Science Inventory

    This report summarizes the biological data collected during a 5-year research project, titled 'An Environmental Assessment of Northern Puget Sound and the Strait of Juan de Fuca.' This report also incorporates biological data collected during a similar program conducted by the Wa...

  14. RECOVERY OF STRAIT OF JUAN DE FUCA INTERTIDAL HABITAT FOLLOWING EXPERIMENTAL CONTAMINATION WITH OIL

    EPA Science Inventory

    This is a second year interim report on the effects of experimental oiling with Prudhoe Bay crude oil on recovery of intertidal infauna and epifauna of the Strait of Juan de Fuca, Washington State. It describes completed studies of the recovery of infauna as recovery rate relates...

  15. Polar Ridges

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03662 Polar Ridges

    This ridge system is located in the south polar region.

    Image information: VIS instrument. Latitude -81.7N, Longitude 296.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  16. Topographically Enhanced Subinertial Currents at Endeavour Ridge

    NASA Astrophysics Data System (ADS)

    Thomson, R. E.; Rabinovich, A. B.; Mihaly, S. F.; Veirs, S.; Stahr, F. R.; McDuff, R. E.; Subbotina, M. M.

    2001-12-01

    We use velocity records collected from moored current meters to examine the effects of seafloor topography and hydrothermal venting on near-bottom (\\~ 2000 m depth) currents flowing over the Endeavour Segment of Juan de Fuca Ridge. Focus is on the 50-m vertical resolution records collected from July-October 2000 near the main Endeavour vent field and on the 2-km lateral resolution records collected from July-October 2001 at three sites within the 100 m deep axial valley. Semidiurnal currents are found to be marginally more energetic than diurnal currents, and flow above the ridge crest is often dominated by wind-generated inertial events (periods \\~ 16 hrs at 48N) and low-frequency (O(10 day) period) clockwise rotary motions. Observations, supported by numerical modeling, reveal marked topographic amplification of subinertial motions within 100 m of the ridge crest. Motions within the diurnal, inertial, and wind-forced frequency bands undergo especially pronounced above-ridge amplification but attenuate equally rapidly within the confines of the narrow (\\~ 1 km) axial valley. Semidiurnal currents are much less affected by the ridge topography and have approximately uniform amplitudes with depth within the first 250 m of the bottom. Within a few tens of meters of the valley floor, the flow is dominated by \\~ 5 cm/s along-axis semidiurnal oscillations and a surprisingly strong (2 to 4 cm/s), persistently northward up-valley flow. The up-valley flow appears to be independent of, and generally counter to, the prevailing flow in the overlying water column. Initial findings suggest that the enhanced near-bottom flow is maintained by an along-valley pressure gradient created by turbulent entrainment of cold (\\~ 2 C) ambient water by the superheated (\\~ 350 C) hydrothermal plumes and low-temperature diffuse flow. If so, the mean-flow dynamics may be analogous to the summer sea-breeze in coastal fjords, with hydrothermal convection playing the role of summertime

  17. Detail of the ridge framing of the clerestory roof, note ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of the ridge framing of the clerestory roof, note the alternating wood and steel beams, view facing northeast - U.S. Marine Corps Base Hawaii, Kaneohe Bay, Warehouse 250, Aviation Storehouse, C Street between Fifth & Sixth Streets, Kaneohe, Honolulu County, HI

  18. Structure of the Lithosphere-Asthenosphere System Beneath the Juan de Fuca Plate: Results of Body Wave Imaging Using Cascadia Initiative Data

    NASA Astrophysics Data System (ADS)

    Byrnes, J. S.; Toomey, D. R.; Hooft, E. E. E.

    2014-12-01

    The plate-scale deployment of ocean bottom seismometers (OBS) as part of the Cascadia Initiative (CI) of NSF provides a unique opportunity to study the structure and dynamics of the lithosphere-asthenosphere system beneath an entire oceanic plate, from its birth at a spreading center to its subduction beneath a continent. Here we present tomographic images of the seismic structure of oceanic upper mantle beneath the Juan de Fuca (JdF) and Gorda plates derived from body wave delay times. The results constrain structural anomalies beneath the JdF and Gorda spreading centers, the Blanco and Mendocino transform faults, near ridge hotspots such as Axial Seamount, and the upper mantle structure beneath the subducting oceanic lithosphere. We measured delay times of teleseismic P and S wave phases for the first two years of the CI. Our tomographic analysis assumes both isotropic and anisotropic starting models and accounts for finite-frequency effects and three-dimensional ray bending. Preliminary results indicate that the upper mantle structure beneath the JdF spreading center is asymmetric, with lower shear wave velocities beneath the Pacific plate (also the direction of ridge migration). On a regional scale, regions of lower seismic velocities beneath the JdF and Gorda spreading centers correlate with shallower ridge depths. Beneath the southern Gorda plate a low velocity anomaly is detected, which is absent to the north; this anomaly is bounded to the south by the Mendocino transform. Ongoing work includes analysis of the third year of CI data, which will improve resolution of structure and allow better definition of anomalies in the vicinity of the Blanco transform. In addition, we will combine ocean and continental data to obtain images of the Cascadia subduction zone.

  19. NORTHEAST CLIMATE DATA

    EPA Science Inventory

    The Northeast Regional Climate Center (NRCC) database includes a complete collection of historical climate data for the northeastern United States as well as continually updated National Weather Service observations and forecasts. In addition, daily temperature and precipitation ...

  20. Transform push, oblique subduction resistance, and intraplate stress of the Juan de Fuca Plate

    NASA Astrophysics Data System (ADS)

    Wang, Kelin; He, Jiangheng; Davis, Earl E.

    1997-01-01

    The Juan de Fuca plate is a small oceanic plate between the Pacific and North America plates. In the southernmost region, referred to as the Gorda deformation zone, the maximum compressive stress σ1 constrained by earthquake focal mechanisms is N-S. Off Oregon, and possibly off Washington, NW trending left-lateral faults cutting the Juan de Fuca plate indicate a σ1 in a NE-SW to E-W direction. The magnitude of differential stress increases from north to south; this is inferred from the plastic yielding and distribution of earthquakes throughout the Gorda deformation zone. To understand how tectonic forces determine the stress field of the Juan de Fuca plate, we have modeled the intraplate stress using both elastic and elastic-perfectly plastic plane-stress finite element models. We conclude that the right-lateral shear motion of the Pacific and North America plates is primarily responsible for the stress pattern of the Juan de Fuca plate. The most important roles are played by a compressional force normal to the Mendocino transform fault, a result of the northward push by the Pacific plate and a horizontal resistance operating against the northward, or margin-parallel, component of oblique subduction. Margin-parallel subduction resistance results in large N-S compression in the Gorda deformation zone because the force is integrated over the full length of the Cascadia subduction zone. The Mendocino transform fault serves as a strong buttress that is very weak in shear but capable of transmitting large strike-normal compressive stresses. Internal failure of the Gorda deformation zone potentially places limits on the magnitude of the fault-normal stresses being transmitted and correspondingly on the magnitude of strike-parallel subduction resistance. Transform faults and oblique subduction zones in other parts of the world can be expected to transmit and create stresses in the same manner.

  1. Transform push, oblique subduction resistance, and intraplate stress of the Juan de Fuca plate

    USGS Publications Warehouse

    Wang, K.; He, J.; Davis, E.E.

    1997-01-01

    The Juan de Fuca plate is a small oceanic plate between the Pacific and North America plates. In the southernmost region, referred to as the Gorda deformation zone, the maximum compressive stress a, constrained by earthquake focal mechanisms is N-S. Off Oregon, and possibly off Washington, NW trending left-lateral faults cutting the Juan de Fuca plate indicate a a, in a NE-SW to E-W direction. The magnitude of differential stress increases from north to south; this is inferred from the plastic yielding and distribution of earthquakes throughout the Gorda deformation zone. To understand how tectonic forces determine the stress field of the Juan de Fuca plate, we have modeled the intraplate stress using both elastic and elastic-perfectly plastic plane-stress finite element models. We conclude that the right-lateral shear motion of the Pacific and North America plates is primarily responsible for the stress pattern of the Juan de Fuca plate. The most important roles are played by a compressional force normal to the Mendocino transform fault, a result of the northward push by the Pacific plate and a horizontal resistance operating against the northward, or margin-parallel, component of oblique subduction. Margin-parallel subduction resistance results in large N-S compression in the Gorda deformation zone because the force is integrated over the full length of the Cascadia subduction zone. The Mendocino transform fault serves as a strong buttress that is very weak in shear but capable of transmitting large strike-normal compressive stresses. Internal failure of the Gorda deformation zone potentially places limits on the magnitude of the fault-normal stresses being transmitted and correspondingly on the magnitude of strike-parallel subduction resistance. Transform faults and oblique subduction zones in other parts of the world can be expected to transmit and create stresses in the same manner. Copyright 1997 by the American Geophysical Union.

  2. Juan de Fuca slab geometry and its relation to Wadati-Benioff zone seismicity

    USGS Publications Warehouse

    McCrory, Patricia A.; Blair, J. Luke; Waldhause, Felix; Oppenheimer, David H.

    2012-01-01

    A new model of the subducted Juan de Fuca plate beneath western North America allows first-order correlations between the occurrence of Wadati-Benioff zone earthquakes and slab geometry, temperature, and hydration state. The geo-referenced 3D model, constructed from weighted control points, integrates depth information from earthquake locations and regional seismic velocity studies. We use the model to separate earthquakes that occur in the Cascadia forearc from those that occur within the underlying Juan de Fuca plate and thereby reveal previously obscured details regarding the spatial distribution of earthquakes. Seismicity within the slab is most prevalent where the slab is warped beneath northwestern California and western Washington suggesting that slab flexure, in addition to expected metamorphic dehydration processes, promotes earthquake occurrence within the subducted oceanic plate. Earthquake patterns beneath western Vancouver Island are consistent with slab dehydration processes. Conversely, the lack of slab earthquakes beneath western Oregon is consistent with an anhydrous slab. Double-differenced relocated seismicity resolves a double seismic zone within the slab beneath northwestern California that strongly constrains the location of the plate interface and delineates a cluster of seismicity 10 km above the surface that includes the 1992 M7.1 Mendocino earthquake. We infer that this earthquake ruptured a surface within the Cascadia accretionary margin above the Juan de Fuca plate. We further speculate that this earthquake is associated with a detached fragment of former Farallon plate. Other subsurface tectonic elements within the forearc may have the potential to generate similar damaging earthquakes.

  3. Juan de Fuca slab geometry and its relation to Wadati-Benioff zone seismicity

    NASA Astrophysics Data System (ADS)

    McCrory, Patricia A.; Blair, J. Luke; Waldhauser, Felix; Oppenheimer, David H.

    2012-09-01

    A new model of the subducted Juan de Fuca plate beneath western North America allows first-order correlations between the occurrence of Wadati-Benioff zone earthquakes and slab geometry, temperature, and hydration state. The geo-referenced 3D model, constructed from weighted control points, integrates depth information from earthquake locations and regional seismic velocity studies. We use the model to separate earthquakes that occur in the Cascadia forearc from those that occur within the underlying Juan de Fuca plate and thereby reveal previously obscured details regarding the spatial distribution of earthquakes. Seismicity within the slab is most prevalent where the slab is warped beneath northwestern California and western Washington suggesting that slab flexure, in addition to expected metamorphic dehydration processes, promotes earthquake occurrence within the subducted oceanic plate. Earthquake patterns beneath western Vancouver Island are consistent with slab dehydration processes. Conversely, the lack of slab earthquakes beneath western Oregon is consistent with an anhydrous slab. Double-differenced relocated seismicity resolves a double seismic zone within the slab beneath northwestern California that strongly constrains the location of the plate interface and delineates a cluster of seismicity 10 km above the surface that includes the 1992 M7.1 Mendocino earthquake. We infer that this earthquake ruptured a surface within the Cascadia accretionary margin above the Juan de Fuca plate. We further speculate that this earthquake is associated with a detached fragment of former Farallon plate. Other subsurface tectonic elements within the forearc may have the potential to generate similar damaging earthquakes.

  4. Precise relative locations for earthquakes in the northeast Pacific region

    SciTech Connect

    Cleveland, K. Michael; VanDeMark, Thomas F.; Ammon, Charles J.

    2015-10-09

    We report that double-difference methods applied to cross-correlation measured Rayleigh wave time shifts are an effective tool to improve epicentroid locations and relative origin time shifts in remote regions. We apply these methods to seismicity offshore of southwestern Canada and the U.S. Pacific Northwest, occurring along the boundaries of the Pacific and Juan de Fuca (including the Explorer Plate and Gorda Block) Plates. The Blanco, Mendocino, Revere-Dellwood, Nootka, and Sovanco fracture zones host the majority of this seismicity, largely consisting of strike-slip earthquakes. The Explorer, Juan de Fuca, and Gorda spreading ridges join these fracture zones and host normal faulting earthquakes. Our results show that at least the moderate-magnitude activity clusters along fault strike, supporting suggestions of large variations in seismic coupling along oceanic transform faults. Our improved relative locations corroborate earlier interpretations of the internal deformation in the Explorer and Gorda Plates. North of the Explorer Plate, improved locations support models that propose northern extension of the Revere-Dellwood fault. Relocations also support interpretations that favor multiple parallel active faults along the Blanco Transform Fault Zone. Seismicity of the western half of the Blanco appears more scattered and less collinear than the eastern half, possibly related to fault maturity. We use azimuthal variations in the Rayleigh wave cross-correlation amplitude to detect and model rupture directivity for a moderate size earthquake along the eastern Blanco Fault. Lastly, the observations constrain the seismogenic zone geometry and suggest a relatively narrow seismogenic zone width of 2 to 4 km.

  5. Precise relative locations for earthquakes in the northeast Pacific region

    DOE PAGESBeta

    Cleveland, K. Michael; VanDeMark, Thomas F.; Ammon, Charles J.

    2015-10-09

    We report that double-difference methods applied to cross-correlation measured Rayleigh wave time shifts are an effective tool to improve epicentroid locations and relative origin time shifts in remote regions. We apply these methods to seismicity offshore of southwestern Canada and the U.S. Pacific Northwest, occurring along the boundaries of the Pacific and Juan de Fuca (including the Explorer Plate and Gorda Block) Plates. The Blanco, Mendocino, Revere-Dellwood, Nootka, and Sovanco fracture zones host the majority of this seismicity, largely consisting of strike-slip earthquakes. The Explorer, Juan de Fuca, and Gorda spreading ridges join these fracture zones and host normal faultingmore » earthquakes. Our results show that at least the moderate-magnitude activity clusters along fault strike, supporting suggestions of large variations in seismic coupling along oceanic transform faults. Our improved relative locations corroborate earlier interpretations of the internal deformation in the Explorer and Gorda Plates. North of the Explorer Plate, improved locations support models that propose northern extension of the Revere-Dellwood fault. Relocations also support interpretations that favor multiple parallel active faults along the Blanco Transform Fault Zone. Seismicity of the western half of the Blanco appears more scattered and less collinear than the eastern half, possibly related to fault maturity. We use azimuthal variations in the Rayleigh wave cross-correlation amplitude to detect and model rupture directivity for a moderate size earthquake along the eastern Blanco Fault. Lastly, the observations constrain the seismogenic zone geometry and suggest a relatively narrow seismogenic zone width of 2 to 4 km.« less

  6. Geophysical Investigation of Australian-Antarctic Ridge Using High-Resolution Gravity and Bathymetry

    NASA Astrophysics Data System (ADS)

    Kim, S. S.; Lin, J.; Park, S. H.; Choi, H.

    2015-12-01

    Much of the Australian-Antarctic Ridge (AAR) has been remained uncharted until 2011 because of its remoteness and harsh weather conditions. From 2011, the multidisciplinary ridge program initiated by the Korea Polar Research Institute (KOPRI) surveyed the little-explored eastern ends of the AAR to characterize the tectonics, geochemistry, and hydrothermal activity of this intermediate spreading system. In this study, we present a detailed analysis of a 300-km-long supersegment of the AAR to quantify the spatial variations in ridge morphology and axial and off-axis volcanisms as constrained by high-resolution shipboard bathymetry and gravity. The ridge axis morphology alternates between rift valleys and axial highs within relatively short ridge segments. To obtain a geological proxy for regional variations in magma supply, we calculated residual mantle Bouguer gravity anomalies (RMBA), gravity-derived crustal thickness, and residual topography for neighboring seven sub-segments. The results of the analyses revealed that the southern flank of the AAR is associated with shallower seafloor, more negative RMBA, thicker crust, and/or less dense mantle in comparison to the conjugate northern flank. Furthermore, this north-south asymmetry becomes more prominent toward the KR1 supersegment of the AAR. The axial topography of the KR1 supersegment exhibits a sharp transition from axial highs at the western end to rift valleys at the eastern end, with regions of axial highs being associated with more robust magma supply as indicated by more negative RMBA. We also compare and contrast the characteristics of the AAR supersegment with that of other ridges of intermediate spreading rates, including the Juan de Fuca Ridge, Galápagos Spreading Center, and Southeast Indian Ridge west of the Australian-Antarctic Discordance, to investigate the influence of ridge-hotspot interaction on ridge magma supply and tectonics.

  7. 33 CFR 334.1200 - Strait of Juan de Fuca, eastern end; off the westerly shore of Whidbey Island; naval restricted...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Register citations affecting § 334.1200, see the List of CFR Sections Affected, which appears in the... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Strait of Juan de Fuca, eastern... AND RESTRICTED AREA REGULATIONS § 334.1200 Strait of Juan de Fuca, eastern end; off the westerly...

  8. VIEW OF NORTHEAST TOWARD MAINTENANCE SHED AT NORTHEAST CORNER OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF NORTHEAST TOWARD MAINTENANCE SHED AT NORTHEAST CORNER OF PARK - Candler Park Historic District, Roughly bounded by Moreland, Dekalb, McLendon & Harold Avenues, Matthews Street & Clifton Terrace, Atlanta, Fulton County, GA

  9. 52. Ground floor, northeast corner, looking northeast at former delivery ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    52. Ground floor, northeast corner, looking northeast at former delivery entries (archways have since been filled in) - Sheffield Farms Milk Plant, 1075 Webster Avenue (southwest corner of 166th Street), Bronx, Bronx County, NY

  10. 5. INTERIOR OF NORTHEAST ROOM AND MEZZANINE, NORTHEAST VIEW OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. INTERIOR OF NORTHEAST ROOM AND MEZZANINE, NORTHEAST VIEW OF (HOISTS IN CENTER). - Vanadium Corporation of America (VCA) Naturita Mill, Sampling Building & Ore Receiving Platform, 3 miles Northwest of Naturita, between Highway 141 & San Miguel River, Naturita, Montrose County, CO

  11. Grafts for Ridge Preservation

    PubMed Central

    Jamjoom, Amal; Cohen, Robert E.

    2015-01-01

    Alveolar ridge bone resorption is a biologic phenomenon that occurs following tooth extraction and cannot be prevented. This paper reviews the vertical and horizontal ridge dimensional changes that are associated with tooth extraction. It also provides an overview of the advantages of ridge preservation as well as grafting materials. A Medline search among English language papers was performed in March 2015 using alveolar ridge preservation, ridge augmentation, and various graft types as search terms. Additional papers were considered following the preliminary review of the initial search that were relevant to alveolar ridge preservation. The literature suggests that ridge preservation methods and augmentation techniques are available to minimize and restore available bone. Numerous grafting materials, such as autografts, allografts, xenografts, and alloplasts, currently are used for ridge preservation. Other materials, such as growth factors, also can be used to enhance biologic outcome. PMID:26262646

  12. Project NEPTUNE: an innovative, powered, fibre-optic cabled deep ocean observatory spanning the Juan de Fuca plate, NE Pacific

    NASA Astrophysics Data System (ADS)

    Barnes, C.; Delaney, J.

    2003-04-01

    NEPTUNE is an innovative facility, a deep-water cabled observatory, that will transform marine science. MARS and VENUS are deep and shallow-water test bed facilities for NEPTUNE located in Monterey Canyon, California and in southern British Columbia, respectively; both were funded in 2002. NEPTUNE will be a network of over 30 subsea observatories covering the 200,000 sq. km Juan de Fuca tectonic plate, Northeast Pacific. It will draw power via two shore stations and receive and exchange data with scientists through 3000 km of submarine fiber-optic cables. Each observatory, and cabled extensions, will host and power many scientific instruments on the surrounding seafloor, in seafloor boreholes and buoyed through the water column. Remotely operated and autonomous vehicles will reside at depth, recharge at observatories, and respond to distant labs. Continuous near-real-time multidisciplinary measurement series will extend over 30 years. Free from the limitations of battery life, ship schedules/ accommodations, bad weather and delayed access to data, scientists will monitor remotely their deep-sea experiments in real time on the Internet, and routinely command instruments to respond to storms, plankton blooms, earthquakes, eruptions, slope slides and other events. Scientists will be able to pose entirely new sets of questions and experiments to understand complex, interacting Earth System processes such as the structure and seismic behavior of the ocean crust; dynamics of hot and cold fluids and gas hydrates in the upper ocean crust and overlying sediments; ocean climate change and its effect on the ocean biota at all depths; and the barely known deep-sea ecosystem dynamics and biodiversity. NEPTUNE is a US/Canada (70/30) partnership to design, test, build and operate the network on behalf of a wide scientific community. The total cost of the project is estimated at about U.S. 250 million from concept to operation. Over U.S. 50 million has already been funded for

  13. Ambient light emission from hydrothermal vents on the Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    White, Sheri N.; Chave, Alan D.; Reynolds, George T.; Van Dover, Cindy L.

    2002-08-01

    A spectral imaging camera was used to observe light emission from high-temperature, deep-sea vents at three hydrothermal sites on the Mid-Atlantic Ridge (MAR): Logatchev, Snake Pit, and Lucky Strike. Ambient light measured at these sites is similar to that observed at sites along the East Pacific Rise and the Juan de Fuca Ridge, with components from both thermal and non-thermal sources. The shrimp species Rimicaris exoculata, which is found on the MAR but not in the Eastern Pacific, possesses a unique photoreceptor capable of detecting low light levels. It is not yet known if R. exoculata ``sees'' vent light. However, since the characteristics of vent light appear to be unrelated to geographical location, the exclusion of R. exoculata from the Eastern Pacific is probably unrelated to differences in ambient light conditions.

  14. Magnetite formation from ferrihydrite by hyperthermophilic archaea from Endeavour Segment, Juan de Fuca Ridge hydrothermal vent chimneys.

    PubMed

    Lin, T Jennifer; Breves, E A; Dyar, M D; Ver Eecke, H C; Jamieson, J W; Holden, J F

    2014-05-01

    Hyperthermophilic iron reducers are common in hydrothermal chimneys found along the Endeavour Segment in the northeastern Pacific Ocean based on culture-dependent estimates. However, information on the availability of Fe(III) (oxyhydr) oxides within these chimneys, the types of Fe(III) (oxyhydr) oxides utilized by the organisms, rates and environmental constraints of hyperthermophilic iron reduction, and mineral end products is needed to determine their biogeochemical significance and are addressed in this study. Thin-section petrography on the interior of a hydrothermal chimney from the Dante edifice at Endeavour showed a thin coat of Fe(III) (oxyhydr) oxide associated with amorphous silica on the exposed outer surfaces of pyrrhotite, sphalerite, and chalcopyrite in pore spaces, along with anhydrite precipitation in the pores that is indicative of seawater ingress. The iron sulfide minerals were likely oxidized to Fe(III) (oxyhydr) oxide with increasing pH and Eh due to cooling and seawater exposure, providing reactants for bioreduction. Culture-dependent estimates of hyperthermophilic iron reducer abundances in this sample were 1740 and 10 cells per gram (dry weight) of material from the outer surface and the marcasite-sphalerite-rich interior, respectively. Two hyperthermophilic iron reducers, Hyperthermus sp. Ro04 and Pyrodictium sp. Su06, were isolated from other active hydrothermal chimneys on the Endeavour Segment. Strain Ro04 is a neutrophilic (pH opt 7-8) heterotroph, while strain Su06 is a mildly acidophilic (pH opt 5), hydrogenotrophic autotroph, both with optimal growth temperatures of 90-92 °C. Mössbauer spectroscopy of the iron oxides before and after growth demonstrated that both organisms form nanophase (<12 nm) magnetite [Fe3 O4 ] from laboratory-synthesized ferrihydrite [Fe10 O14 (OH)2 ] with no detectable mineral intermediates. They produced up to 40 mm Fe(2+) in a growth-dependent manner, while all abiotic and biotic controls produced <3 mm Fe(2+) . Hyperthermophilic iron reducers may have a growth advantage over other hyperthermophiles in hydrothermal systems that are mildly acidic where mineral weathering at increased temperatures occurs. PMID:24612368

  15. Viral Genomics and Evolution in Subseafloor Diffuse Flow Viral Communities in the Main Endeavour Hydrothermal Field, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Anderson, R. E.; Baross, J. A.

    2010-04-01

    In the dynamic environment of hydrothermal vents, transduction may play a crucial role in microbial evolution. Metagenomic analysis of diffuse flow viral communities may elucidate the nature and extent of transduction in these ancient ecosystems.

  16. Heat and chemical flux variability within the Main Endeavour Field, Juan de Fuca Ridge, from 2000, 2004

    NASA Astrophysics Data System (ADS)

    Kellogg, J. P.; McDuff, R. E.; Hautala, S. L.; Stahr, F.

    2010-12-01

    The Main Endeavour Field (MEF) has had a split personality since it was discovered. The southern half of the field is regularly observed to be hotter and fresher than the northern half. Differences lessened after the 1999 earthquake event, but the thermal and chemical gradient remains. We examine CTD and MAVS current meter data collected during surveys, designed to intersect the rising hydrothermal plume, conducted with the Autonomous Benthic Explorer (ABE) in 2000 and 2004. By taking subsets of the data over known clusters of structures within the field, we attribute fractional contributions to the whole field heat and salt fluxes. Preliminary findings indicate that North MEF contributes ~90% and ~100% of the heat from MEF in 2000 and 2004 respectively. It is clear from this that the majority of the MEF buoyancy flux is from North MEF even though the source fluids from South MEF are estimated to be initially more buoyant than those from North MEF. Within North MEF, ~2/3 of the heat comes from the Grotto, Dante, Lobo sulfide cluster and ~1/4 from the Hulk and Crypto cluster. These data, for the intra-field spatial scales of heat and salt flux, may allow us to infer mechanisms capable of altering the porous network of the hydrothermal system.

  17. Beryllium 10 in hydrothermal vent deposits from the East Pacific Ridges: Role of sediments in the hydrothermal processes

    SciTech Connect

    Valette-Silver, J.N.; Tera, F.; Klein, J.; Middleton, R.

    1987-10-10

    Beryllium 10 concentrations were determined for 31 handpicked hydrothermal sulfides, six oxyhydroxides, seven basalts, and five sediments collected from the hydrothermally active areas of the East Pacific ridges. The samples includes specimens from the East Pacific Rise (EPR) at 21 /sup 0/N and 13 /sup 0/N, the Galapagos Rift, the Guaymas Basin, and the Gorda and the Juan de Fuca ridges. Additional samples from massive sulfides associated with the Oman ophiolites were studied. In all samples, we obtained values ranging from 0.04 x 10/sup 6/ atoms/g to 125 x 10/sup 6/ atoms/g, with the lowest values being very close to our blank (0.015 x 10/sup 6/ atoms/g). The data show systematic variations with sample location and type. The /sup 10/Be concentrations measured for the mid-ocean basalts are of the order of 0.3 x 10/sup 6/ atoms/g and reach 3800 x 10/sup 6/ atoms/g for the pelagic deep-sea sediments collected near the EPR 21 /sup 0/N. Based on their /sup 10/Be concentrations, we can clearly distinguish two categories of sulfides: sulfides containing low /sup 10/Be concentration (<10 /sup 6/ atoms/g) sitting directly on the mid-ocean basalt (EPR of Juan de Fuca), and sulfides with high /sup 10/Be concentration (>10/sup 6/ atoms/g) located atop of a thick pile of young sediments (Guaymas Basin or Gorda Ridge).

  18. Northeast Hellas Landscape

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-446, 8 August 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image of pitted terrain northeast of Hellas Basin shows light-toned outcrops of layered, sedimentary rock, and a valley floor covered by large, dark ripples or small dunes. Similar light-toned sedimentary materials are found throughout the region immediately northeast of Hellas, and in the crater, Terby. The area shown is 3 km (1.9 mi) wide and located near 27.5oS, 281.7oW. Sunlight illuminates the scene from the upper left.

  19. Segmentation of mid-ocean ridges attributed to oblique mantle divergence

    NASA Astrophysics Data System (ADS)

    Vanderbeek, Brandon P.; Toomey, Douglas R.; Hooft, Emilie E. E.; Wilcock, William S. D.

    2016-08-01

    The origin of mid-ocean ridge segmentation--the systematic along-axis variation in tectonic and magmatic processes--remains controversial. It is commonly assumed that mantle flow is a passive response to plate divergence and that between transform faults magma supply controls segmentation. Using seismic tomography, we constrain the geometry of mantle flow and the distribution of mantle melt beneath the intermediate-spreading Endeavour segment of the Juan de Fuca Ridge. Our results, in combination with prior studies, establish a systematic skew between the mantle-divergence and plate-spreading directions. In all three cases studied, mantle divergence is advanced with respect to recent changes in the plate-spreading direction and the extent to which the flow field is advanced increases with decreasing spreading rate. Furthermore, seismic images show that large-offset, non-transform discontinuities are regions of enhanced mantle melt retention. We propose that oblique mantle flow beneath mid-ocean ridges is a driving force for the reorientation of spreading segments and the formation of ridge-axis discontinuities. The resulting tectonic discontinuities decrease the efficiency of upward melt transport, thus defining segment-scale variations in magmatic processes. We predict that across spreading rates mid-ocean ridge segmentation is controlled by evolving patterns in asthenospheric flow and the dynamics of lithospheric rifting.

  20. Crustal Assimilation and the Petrogenesis of Mid-Ocean Ridge Dacites

    NASA Astrophysics Data System (ADS)

    Wanless, V.; Perfit, M. R.; Ridley, W. I.; Klein, E. M.; Grimes, C. B.; Valley, J. W.

    2010-12-01

    The majority of eruptions at spreading centers produce lavas with relatively homogeneous mid-ocean ridge basalt (MORB) compositions, but andesitic and dacitic lavas have been sampled at several different mid-ocean ridges (MOR). Eruption of high-silica lavas are commonly associated with ridge discontinuities, examples being propagating ridge tips at ridge-transform intersections on the Juan de Fuca Ridge and eastern Galápagos spreading center, and at the 9°N overlapping spreading center on the East Pacific Rise. Although these lavas are found at different ridges, the dacites show remarkably similar major element trends and incompatible trace element enrichments, suggesting that similar processes control their formation. Although most geochemical variability in the MOR series basalts -ferrobasalts - FeTi basalts is consistent with low-pressure fractional crystallization, modeling suggests that extreme fractional crystallization accompanied by partial melting and assimilation of amphibole-bearing altered oceanic crust is important in the petrogenesis of high-silica differentiates. Such a complex process is consistent with dacites showing: 1) elevated U, Th, Zr, and Hf; 2) relatively low Nb and Ta; 3) Al2O3, K2O, Cl, H2O concentrations that are higher than expected from fractional crystallization; 4) relatively low δ18O glass values of ~5.6 compared to values ~6.9 ‰ expected from fractional crystallization. This suggests that crustal assimilation is an important process in the formation of highly evolved MOR lavas (i.e., andesites and dacites) and may be significant in formation of MORB in general. Although basaltic material at MOR is much more voluminous than high-silica lavas, the eruption of dacites at numerous ridges, and the seemingly ubiquitous presence of plagiogranite veins in exposed and drilled sections of gabbroic Layer 3 indicate that high-silica lavas are an intrinsic component of the ocean crust, though their petrogenesis may involve various

  1. Sub-Seafloor Carbon Dioxide Storage Potential on the Juan de Fuca Plate, Western North America

    SciTech Connect

    Jerry Fairley; Robert Podgorney

    2012-11-01

    The Juan de Fuca plate, off the western coast of North America, has been suggested as a site for geological sequestration of waste carbon dioxide because of its many attractive characteristics (high permeability, large storage capacity, reactive rock types). Here we model CO2 injection into fractured basalts comprising the upper several hundred meters of the sub-seafloor basalt reservoir, overlain with low-permeability sediments and a large saline water column, to examine the feasibility of this reservoir for CO2 storage. Our simulations indicate that the sub-seafloor basalts of the Juan de Fuca plate may be an excellent CO2 storage candidate, as multiple trapping mechanisms (hydrodynamic, density inversions, and mineralization) act to keep the CO2 isolated from terrestrial environments. Questions remain about the lateral extent and connectivity of the high permeability basalts; however, the lack of wells or boreholes and thick sediment cover maximize storage potential while minimizing potential leakage pathways. Although promising, more study is needed to determine the economic viability of this option.

  2. A Geo-referenced 3D model of the Juan de Fuca Slab and associated seismicity

    USGS Publications Warehouse

    Blair, J.L.; McCrory, P.A.; Oppenheimer, D.H.; Waldhauser, F.

    2011-01-01

    We present a Geographic Information System (GIS) of a new 3-dimensional (3D) model of the subducted Juan de Fuca Plate beneath western North America and associated seismicity of the Cascadia subduction system. The geo-referenced 3D model was constructed from weighted control points that integrate depth information from hypocenter locations and regional seismic velocity studies. We used the 3D model to differentiate earthquakes that occur above the Juan de Fuca Plate surface from earthquakes that occur below the plate surface. This GIS project of the Cascadia subduction system supersedes the one previously published by McCrory and others (2006). Our new slab model updates the model with new constraints. The most significant updates to the model include: (1) weighted control points to incorporate spatial uncertainty, (2) an additional gridded slab surface based on the Generic Mapping Tools (GMT) Surface program which constructs surfaces based on splines in tension (see expanded description below), (3) double-differenced hypocenter locations in northern California to better constrain slab location there, and (4) revised slab shape based on new hypocenter profiles that incorporate routine depth uncertainties as well as data from new seismic-reflection and seismic-refraction studies. We also provide a 3D fly-through animation of the model for use as a visualization tool.

  3. Tomographic imaging of the Cascadia subduction zone: Constraints on the Juan de Fuca slab

    NASA Astrophysics Data System (ADS)

    Chen, Chuanxu; Zhao, Dapeng; Wu, Shiguo

    2015-04-01

    We used 40,343 P-wave arrival times from 1883 local earthquakes and 105,455 P-wave arrivals from 6361 teleseismic events to study the detailed structure of the Cascadia subduction zone. We conducted tomographic inversions using a starting velocity model which includes the high-velocity subducting Juan de Fuca slab as a priori information. A number of such slab-constrained inversions are conducted by changing the slab thickness and the velocity contrast between the slab and the surrounding mantle. Our optimal 3-D velocity model fits the data much better than that determined by an inversion with a 1-D homogeneous starting model. Our results show that the subducting Juan de Fuca slab has a thickness of 30-50 km and a P-wave velocity of 1-3% higher than that of the surrounding mantle. Beneath the northern and southern parts of the Cascadia, P-wave velocity is lower in the slab and along the slab interface, which may reflect a more hydrated slab and more active slab dehydration there. The lateral velocity variations may indicate different degrees of slab dehydration and forearc mantle serpentinization. The segmentation in episodic tremor and slip (ETS) is also spatially coincident with the velocity heterogeneities, indicating that the ETS occurrence and recurrence interval are controlled by fluid activity in and around the mantle wedge corner.

  4. 46 CFR 7.145 - Strait of Juan de Fuca, Haro Strait and Strait of Georgia WA.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 1 2013-10-01 2013-10-01 false Strait of Juan de Fuca, Haro Strait and Strait of Georgia WA. 7.145 Section 7.145 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES... of Georgia WA. (a) A line drawn from the northernmost point of Angeles Point to latitude 48°21.1′...

  5. 46 CFR 7.145 - Strait of Juan de Fuca, Haro Strait and Strait of Georgia WA.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 1 2012-10-01 2012-10-01 false Strait of Juan de Fuca, Haro Strait and Strait of Georgia WA. 7.145 Section 7.145 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES... of Georgia WA. (a) A line drawn from the northernmost point of Angeles Point to latitude 48°21.1′...

  6. 46 CFR 7.145 - Strait of Juan de Fuca, Haro Strait and Strait of Georgia WA.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 1 2011-10-01 2011-10-01 false Strait of Juan de Fuca, Haro Strait and Strait of Georgia WA. 7.145 Section 7.145 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES... of Georgia WA. (a) A line drawn from the northernmost point of Angeles Point to latitude 48°21.1′...

  7. 46 CFR 7.145 - Strait of Juan de Fuca, Haro Strait and Strait of Georgia WA.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 1 2014-10-01 2014-10-01 false Strait of Juan de Fuca, Haro Strait and Strait of Georgia WA. 7.145 Section 7.145 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES... of Georgia WA. (a) A line drawn from the northernmost point of Angeles Point to latitude 48°21.1′...

  8. HF (HIGH FREQUENCY) RADAR MEASUREMENTS OF CIRCULATION IN THE EASTERN STRAIT OF JUAN DE FUCA (AUGUST, 1978)

    EPA Science Inventory

    During August, 1978, the surface currents in the Eastern Strait of Juan de Fuca were mapped with a High Frequency (HF) radar system (CODAR). The surface currents were measured simultaneously over several hundred square kilometers at one hour intervals continuously for five days. ...

  9. HF (HIGH FREQUENCY) RADAR MEASUREMENTS OF CIRCULATION IN THE EASTERN STRAIT OF JUAN DE FUCA NEAR PROTECTION ISLAND (JULY, 1979)

    EPA Science Inventory

    During July 1979 the surface currents in the Eastern Strait of Juan de Fuca were mapped with a High Frequency (HF) radar system (CODAR). These currents were measured simultaneously over several hundred square kilometers continuously for five days. The strong tidal currents and es...

  10. 33 CFR 165.1310 - Strait of Juan de Fuca and adjacent coastal waters of Northwest Washington; Makah Whale Hunting...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Strait of Juan de Fuca and adjacent coastal waters of Northwest Washington; Makah Whale Hunting-Regulated Navigation Area. 165.1310 Section 165.1310 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PORTS AND WATERWAYS SAFETY...