Multi-channel seismic imaging of a crustal magma chamber along the East Pacific Rise

Detrick, R. S.; Buhl, Peter; Vera, E.; Mutter, John C.; Orcutt, John A.; Madsen, John A.; Brocher, Thomas M.

doi:10.1038/326035a0

Cited by 718 publications

(440 citation statements)

References 30 publications

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“…Our model suggests velocities in the zone are probably higher than 6 km/s. This coupled with the lack of an axial magma chamber reflector [Detrick et al, 1987] indicates that the amount of magma is presently small compared to other ridge segments. The presence of volcanism on the RTI high also provides evidence that magma is at least episodically abundant beneath the northern ridge segment.…”

Section: Discussionmentioning

confidence: 99%

“…No evidence for a magma chamber reflector has been observed under the RTI Detrick et al, 1987]. However, the -0.7 km/s reduction in the middle to lower crustal velocities may indicate high temperatures associated with RTI volcanism.…”

mentioning

confidence: 87%

“…This distinctive morphology suggests that the southern segment is in a major phase of basaltic melt genesis [Gallo et al, 1986;Kastens et al, 1986]. An axial magma chamber reflector was detected beneath the southern segment by Detrick et al [1987] The seismic source was a tuned array of 10 air guns with a total gun volume of ~65.5 L (4000 cubic inches). The guns were towed behind the ship at ~ 10 m depth and fired at 100-s intervals during the second deployment giving a shot spacing of roughly 230-240 m. Shot intervals of less than 100 s were found to be too short; the resulting reverberation persisted within the water column, increasing significantly the noise levels at the seafloor instruments.…”

Section: Regional Geologymentioning

confidence: 99%

“…In addition, Detrick et al [1987], during a seismic reflection survey, did not detect an axial magma chamber reflector for 70 km under the EPR axis north of the RTI high.…”

Section: Regional Geologymentioning

confidence: 99%

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Velocity structure from forward modeling of the eastern ridge‐transform intersection area of the Clipperton Fracture Zone, East Pacific Rise

Begnaud¹,

McClain²,

Barth³

et al. 1997

J. Geophys. Res.

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Abstract. In the spring of 1994, we undertook an extensive geophysical study of the Clipperton Fracture Zone (FZ) on the fast spreading East Pacific Rise. The Clipperton Area Seismic Study to Investigate Compensation experiment (CLASSIC) included surveys to examine the deep structures associated with the fracture zone and adjacent northern ridge segment. In this paper, we report the results from five seismic profiles acquired over the eastern ridge-transform intersection (RTI), including profiles over the RTI high, the northern ridge segment, and the eastern transform region. The travel time data for crustal phases, Moho reflections, and mantle phases were modeled using two-dimensional ray tracing. Seismic profiles reveal that the crust is similar in thickness north and south of the Clipperton FZ, despite differences in axial topography that have previously been interpreted in terms of differences in magma supply. When compared to older crust, the northern ridge axis is characterized by lower seismic velocities and higher attenuation. In our model, a low-velocity zone exists beneath the ridge axis, probably associated with a zone of partial melt and/or very high temperatures. Within the transform zone, we find that the southeastern trough is underlain by nearly normal crustal structure. The crust is slightly thinner than the adjacent aseismic extension but not enough to compensate for the depths of the trough. Toward the RTI, the trough is replaced by an intersection high which appears underlain by a thickened crust, and a thicker upper crustal section. Both characteristics indicate that the intersection high is a volcanic feature produced by excess volcanism at the intersection. The volcanism acts to "fill in" the transform trough, creating the thicker crust that extends under the eastern aseismic extension of the transform. Our results show that the northern ridge segment, often identified as magma-starved, displays the crustal thickness and apparent signal attenuation characteristic of a plentiful, but perhaps episodic, magma supply.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 87%

Section: Regional Geologymentioning

confidence: 99%

“…In addition, Detrick et al [1987], during a seismic reflection survey, did not detect an axial magma chamber reflector for 70 km under the EPR axis north of the RTI high.…”

Section: Regional Geologymentioning

confidence: 99%

See 2 more Smart Citations

Velocity structure from forward modeling of the eastern ridge‐transform intersection area of the Clipperton Fracture Zone, East Pacific Rise

Begnaud¹,

McClain²,

Barth³

et al. 1997

J. Geophys. Res.

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“…We assume that magma at 1200øC is instantaneously emplaced at a depth of 2 km in the crust which is typical for ridge crest hydrothermal systems [Detrick et al, 1987]. This depth corresponds to a hydrostatic pressure of • 45 MPa.…”

Section: Conduction Modelmentioning

confidence: 99%

Evolution of a brine‐saturated layer at the base of a ridge‐crest hydrothermal system

Lowell¹,

Germanovich²

1997

J. Geophys. Res.

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Abstract. Vent fluids with chlorinities significantly greater than seawater are indicative of mixing between hydrothermal seawater and brines that have formed as a result of supercritical phase separation. We relate the evolution of a brine-saturated layer to magmatic and tectonic processes at the base of a ridge crest hydrothermal system. A conductive heat balance indicates that under steady state conditions such a brine-saturated layer is typically ~ 1-10 m thick and contains 10 7 to 10 8 kg of brine with 6 -10 times the chlorinity of seawater. Simple mixing and fractionation models indicate that the depletion and replenishment of brine-saturated layers may occur on a timescale of years to centuries. A timescale of years is consistent with temporal changes in chlorinity of fluids at vents in areas of recent, known dike injection. In these systems, brines may be undergoing depletion by mixing with liquid-phase seawater. Vents stably emitting high-chlorinity fluids on timescales of decades may represent older systems in which brines are being depleted by diffusion into an overlying liquid-phase hydrothermal system.

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Seafloor photo‐geology and sonar terrain modeling at the 9°N overlapping spreading center, East Pacific Rise

Klein

White

Nunnery

et al. 2013

Geochem Geophys Geosyst

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[1] A fundamental goal in the study of mid-ocean ridges is to understand the relationship between the distribution of melt at depth and seafloor features. Building on geophysical information on subsurface melt at the 9 N overlapping spreading center on the East Pacific Rise, we use terrain modeling (DSL-120A side scan and bathymetry), photo-geology (Jason II and WHOI TowCam), and geochemical data to explore this relationship. Terrain modeling identified four distinct geomorphic provinces with common seafloor characteristics that correspond well to changes in subsurface melt distribution. Visual observations were used to interpret terrain modeling results and to establish a relative seafloor age scale, calibrated with radiometric age dates, to identify areas of recent volcanism. On the east limb, recent eruptions in the north are localized over the margins of the 4 km wide asymmetric melt sill, forming a prominent off-axis pillow ridge. Along the southern east limb, recent eruptions occur along a neovolcanic ridge that hugs the overlap basin and lies several kilometers west of the plunging melt sill. Our results suggest that long-term southward migration of the east limb occurs through a series of diking events with a net southward propagation direction. Examining sites of recent eruptions in the context of geophysical data on melt distribution in the crust and upper mantle suggests melt may follow complex paths from depth to the surface. Overall, our findings emphasize the value of integrating information obtained from photo-geology, terrain modeling, lava geochemistry and petrography, and geophysics to constrain the nature of melt delivery at mid-ocean ridges.Components: 13,950 words, 12 figures.

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Multi-channel seismic imaging of a crustal magma chamber along the East Pacific Rise

Cited by 718 publications

References 30 publications

Velocity structure from forward modeling of the eastern ridge‐transform intersection area of the Clipperton Fracture Zone, East Pacific Rise

Velocity structure from forward modeling of the eastern ridge‐transform intersection area of the Clipperton Fracture Zone, East Pacific Rise

Evolution of a brine‐saturated layer at the base of a ridge‐crest hydrothermal system

Seafloor photo‐geology and sonar terrain modeling at the 9°N overlapping spreading center, East Pacific Rise

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