Seismic identification of along-axis hydrothermal flow on the East Pacific Rise

Tolstoy, M.; Waldhauser, F.; Bohnenstiehl, D. R.; Weekly, R. T.; Kim, W.-Y.

doi:10.1038/nature06424

Cited by 137 publications

(173 citation statements)

References 30 publications

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“…18). This result is very different from those of de Martin et al (2007) and Tolstoy et al (2008), who found many microearthquakes related to hydrothermal activity. The difference may be because their OBS network had a wider spacing (about 5 km) than the earlier networks (about 1-5 km), and they examined this possibility by checking the seismicity near an OBS, which was less than 1 km from the Pika site.…”

Section: Hydrothermal Vent Sitescontrasting

confidence: 56%

The Mantle Dynamics, the Crustal Formation, and the Hydrothermal Activity of the Southern Mariana Trough Back-Arc Basin

Seama

Sato

Nogi

et al. 2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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The Southern Mariana Trough back-arc basin is a currently active back arc basin, and it has fast spreading morphologic and geophysical characteristics, suggesting an additional magma supply, even though the full spreading rate is categorized as slow spreading. Five hydrothermal vent sites have been found within 5 km around the spreading axis at 13 N. The Japanese TAIGA Project selected this area as one of three integrated target sites, and TAIGA Project members conducted series of JAMSTEC research cruises for different types of geophysical surveys, together with dive observation and samplings by the submersible Shinkai 6500. We reviewed the results from these geophysical surveys and the volcanic rock samples to summarize the products from the TAIGA Project. The results provide strong constraints on the mantle dynamics and the crustal formation at the Southern Mariana Trough back-arc basin; all the results support that they are influenced by hydration derived from the subducting slab with accompanying the additional magma supply. Furthermore, the results from the geophysical and geological surveys for the five hydrothermal vent sites provide characteristic features on the hydrothermal activity and the features are different between on-axis and off-axis hydrothermal sites. The on-axis hydrothermal site is associated with an episodic diking event followed by fissures in a fourth order ridge segment, and its duration and size vary depending on the episodic diking event and on the fissures following. In contrast, the formation of the off-axis hydrothermal sites is closely related to the residual heat from the volcanism rather than tectonic stresses accompanied by faults, and the off-axis hydrothermal activity is for a long period and in a large scale. We summarized all the evidence to propose our scenario of the mantle dynamics, the crustal formation, and the hydrothermal activity of the Southern Mariana Trough back-arc basin.

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Section: Hydrothermal Vent Sitescontrasting

confidence: 56%

The Mantle Dynamics, the Crustal Formation, and the Hydrothermal Activity of the Southern Mariana Trough Back-Arc Basin

Seama

Sato

Nogi

et al. 2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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“…As oceanic plates spread apart, 3 upwelling mantle beneath the ridge undergoes decompressional melting and transport to a narrow zone of crustal formation. Seismic data shows that at fast spreading ridges a zone of partially molten crust underlies a thin, mostly liquid lens of magma 10 to 100 meters thick situated between approximately 1 and 3 kilometers beneath the seafloor [Detrick et al, 1987;Sinton and Detrick, 1992;Sohn et al, 1998;MacLeod and Yaouancq, 2000;Kelley et al, 2002;Tolstoy et al, 2008]. Replenishment of the magma lens, commonly called the AMC (axial magma chamber) may result in diking events and magmatic eruptions [Germanovich et al, 2011].…”

Section: General Background On Seafloor Hydrothermal Systemsmentioning

confidence: 99%

The response of two-phase hydrothermal systems to changing magmatic heat input at mid-ocean ridges

Choi

Lowell

2015

Deep Sea Research Part II: Topical Studies in Oceanography

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Hydrothermal processes at oceanic spreading centers are largely influenced by changing magmatic heat input. I use the NaCl-H 2 O FISHES code to investigate the evolution of surface temperature and salinity as a function of time-varying heat flux at the base of a two-phase, vaporbrine hydrothermal system. I consider a two-dimensional rectangular box that is 1.5 km deep and 4 km long with homogeneous permeability of 10 -13 m 2 . Temperature and pressure at top boundary correspond to seafloor conditions of 10C, 25MPa respectively. Impermeable,

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“…This low porosity suggests that these areas would not involve a lot of fluid, potentially because this area is massive and less fractured. The regions of high resistivity could act as barriers for across-axis hydrothermal circulation, leading to preferential along-axis circulation, similar to the observation at the East Pacific Rise (Tolstoy et al 2008).…”

Section: Discussionmentioning

confidence: 81%

“…This result suggests that fluid estimated at 44-200 C is not replaced by 2 C seawater. Fluid at 44-200 C and at depths of 800-1,500 m may represent a hydrothermal heating zone, one example of which was deduced at the East Pacific Rise (Tolstoy et al 2008).…”

Section: Discussionmentioning

confidence: 99%

“…The magnetic field anomaly is obtained by subtracting the magnetic field amplitude predicted from the optimal 1-D resistivity structure model B p from that observed B o in logarithmic scale (log |B o | À log |B p |). A program developed by Tada et al (2011) was used for the forward modeling. The size of the modeling area was 4,000 Â 4,600 Â 4,000 m in the x-, y-, and z-axes (the x-axis is parallel to the ridge axis) and was constructed using 80 Â 92 Â 80 cubes (the dimension of the cube is 50 m).…”

Section: Obtaining a Three-dimensional Electrical Resistivity Structurementioning

confidence: 99%

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Electrical Resistivity Structure of the Snail Site at the Southern Mariana Trough Spreading Center

Matsuno

Kimura

Seama

2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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The electrical resistivity of the oceanic crust is sensitive to the porosity of the crust and the fluid temperature within crustal fractures and pores. The spatial variation of the crustal porosity and the fluid temperature that is related to a hydrothermal circulation can be deduced by revealing an electrical resistivity structure of the oceanic crust involving a hydrothermal site. We carried out a magnetometric resistivity experiment using an active source to reveal an electrical resistivity structure of the oceanic crust at the Snail site on the ridge crest of the Southern Mariana Trough. Active source electric currents were transmitted along and across the ridge axis in a 4,000 m 2 area including the Snail site. Five ocean bottom magnetometers were deployed around the Snail site as receivers to measure the magnetic field induced by the transmission of the active source electric currents. The amplitude of the induced magnetic field was calculated by maximizing data density and the signal to error ratio in the data, and locations of the transmissions were determined using several types of calibration data. An optimal 1-D resistivity structure of the oceanic crust, averaged over the experimental area, was deduced by least squares from the data of the amplitude of the magnetic field and the location of the transmission. After calculating magnetic field anomalies, which are deviations of the observed amplitude from the prediction of the optimal 1-D resistivity model, an optimal 3-D resistivity structure was deduced from the magnetic field anomalies through trial and error 3-D forward modeling. The optimal 1-D resistivity structure is a two-layer model, which consists of a 5.6 Ω-m upper layer having a 1,500 m thickness and a 0.1 Ω-m underlying half-space. Using Archie's law and porosity profiles of the oceanic crust, the resistivity of 5.6 Ω-m at depths ranging from 800 to 1,500 m suggests the presence of hightemperature fluid related to the hydrothermal circulation. The resistivity of 0.1 Ω-m below 1,500 m depth may represent a magma mush that is a heat source for the hydrothermal circulation. The optimal 3-D resistivity structure includes a conductive anomaly (0.56 Ω-m in approximately 300 m 2 area down to 400 m depth) immediately below the Snail site, two resistive anomalies (56 Ω-m with slightly larger volumes than the conductive anomaly) adjacent to the conductive anomaly on the across-ridge side, and three conductive anomalies away from the Snail site. The conductive anomaly immediately below the Snail site suggests hydrothermal fluid, and the adjacent resistive anomalies suggest areas of low porosity. The size and distribution of the conductive and resistive anomalies near the Snail site constrains the size and style of the hydrothermal circulation.

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Seismic identification of along-axis hydrothermal flow on the East Pacific Rise

Cited by 137 publications

References 30 publications

The Mantle Dynamics, the Crustal Formation, and the Hydrothermal Activity of the Southern Mariana Trough Back-Arc Basin

The Mantle Dynamics, the Crustal Formation, and the Hydrothermal Activity of the Southern Mariana Trough Back-Arc Basin

The response of two-phase hydrothermal systems to changing magmatic heat input at mid-ocean ridges

Electrical Resistivity Structure of the Snail Site at the Southern Mariana Trough Spreading Center

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