Tectonics of the Mid-Atlantic rift valley between the TAG and MARK areas (26–24°N): Evidence for vertical tectonism

Zonenshain, Lev P.; Kuzmin, M. I.; Lisitsin, A. P.; Bogdanov, Yu. A.; Baranov, Boris

doi:10.1016/0040-1951(89)90167-4

Cited by 96 publications

(109 citation statements)

References 28 publications

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“…An axis-parallel linear magnetization low was identified over the eastern rift valley wall, and was modeled as crustal thinning caused by 4 km of horizontal extension along a normal fault. This interpretation was supported by the observation of a gabbroic outcrop a few kilometers east of the TAG field at mid-depth (3000 m) on the eastern valley wall (Zonenshain et al, 1989). In their model, Tivey et al (2003) suggested that the hydrothermal field is located on the hanging wall of this active detachment fault within 3 km of its termination and, based on results from an early seismic experiment (Kong et al, 1992), that hydrothermal circulation is driven by heat from a mid-crustal magma reservoir.…”

Section: Geotectonic Setting Of the Tag Hydrothermal Systemmentioning

confidence: 70%

“…The only constraint on the location of the fault termination is that it must lie to the west of the dike and gabbro outcrops on the valley wall, which have been reported to occur at depths shallower than 3050 m (Zonenshain et al, 1989). While this coincides with the deeper areas of the Low Temperature Zone, it does not explain fluid flow at shallower depths on the eastern valley wall.…”

Section: The Role Of the Detachment Faultmentioning

confidence: 98%

“…The hydrothermal field lies 2.4 km east of the spreading axis adjacent to the eastern axial valley wall. The eastern axial valley wall is steeper than the western wall, and sheeted dikes and gabbro have been recovered from mid-depth (~3000 m) on the wall (Zonenshain et al, 1989;STAG Cruise Report, 2004). …”

Section: Geotectonic Setting Of the Tag Hydrothermal Systemmentioning

confidence: 99%

“…Nomenclature as summarized in Humphris and Tivey (2000). Gabbro/dike outcrops are also marked (Zonenshain et al, 1989;STAG Cruise Report, 2004) Figure 5…”

Section: Acknowledgementsmentioning

confidence: 99%

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The Trans-Atlantic Geotraverse hydrothermal field: A hydrothermal system on an active detachment fault

Humphris

Tivey

2015

Deep Sea Research Part II: Topical Studies in Oceanography

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Over the last ten years, geophysical studies have revealed that the Trans-Atlantic Geotraverse (TAG) hydrothermal field (26°08'N on the Mid-Atlantic Ridge) is located on the hanging wall of an active detachment fault. This is particularly important in light of the recognition that detachment faulting accounts for crustal accretion/extension along a significant portion of the Mid-Atlantic Ridge, and that the majority of confirmed vent sites on this slow-spreading ridge are hosted on detachment faults. The TAG hydrothermal field is one of the largest sites of high-temperature hydrothermal activity and mineralization found to date on the seafloor, and is comprised of active and relict deposits in different stages of evolution. The episodic nature of hydrothermal activity over the last 140 ka provides strong evidence that the complex shape and geological structure of the active detachment fault system exerts first order, but poorly understood, influences on the hydrothermal circulation patterns, fluid chemistry, and mineral deposition. While hydrothermal circulation extracts heat from a deep source region, the location of the source region at TAG is unknown. Hydrothermal upflow is likely focused along the relatively permeable detachment fault interface at depth, and then the high temperature fluids leave the low-angle portion of the detachment fault and rise vertically through the highly fissured hanging wall to the seafloor. The presence of abundant anhydrite in the cone on the summit of the TAG active mound and in veins in the crust beneath provides evidence for a fluid circulation system that entrains significant amounts of seawater into the shallow parts of the mound and stockwork. Given the importance of detachment faulting for crustal extension at slow spreading ridges, the fundamental question that still needs to be addressed is: How do detachment fault systems, and the structure at depth associated with these systems (e.g., presence of plutons and/or high permeability zones) influence the pattern of hydrothermal circulation, mineral deposition, and fluid chemistry, both in space and time, within slowly accreted ocean crust?

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Section: Geotectonic Setting Of the Tag Hydrothermal Systemmentioning

confidence: 70%

Section: The Role Of the Detachment Faultmentioning

confidence: 98%

Section: Geotectonic Setting Of the Tag Hydrothermal Systemmentioning

confidence: 99%

“…Nomenclature as summarized in Humphris and Tivey (2000). Gabbro/dike outcrops are also marked (Zonenshain et al, 1989;STAG Cruise Report, 2004) Figure 5…”

Section: Acknowledgementsmentioning

confidence: 99%

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The Trans-Atlantic Geotraverse hydrothermal field: A hydrothermal system on an active detachment fault

Humphris

Tivey

2015

Deep Sea Research Part II: Topical Studies in Oceanography

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“…This study focuses on three ridge segments which are separated by non-transform The rift morphology of these ridge segments has been described in detail by Sempere et al (1993) and Zonenshain et al (1989), and the axial and ridge-flank morphology is discussed by Tucholke et al (in press, a). Detailed morphology of the segments is shown in the contoured bathymetric map of Figure 2.…”

Section: Tectonic Settingmentioning

confidence: 99%

The geological record of oceanic crustal accretion and tectonism at slow-spreading ridges

Jaroslow¹

1996

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Microearthquake evidence for reaction-driven cracking within the Trans-Atlantic Geotraverse active hydrothermal deposit

Pontbriand¹,

Sohn

2014

J. Geophys. Res. Solid Earth

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We detected 32,078 very small, local microearthquakes (average M L = À1) during a 9 month deployment of five ocean bottom seismometers on the periphery of the Trans-Atlantic Geotraverse active mound. Seismicity rates were constant without any main shock-aftershock behavior at~243 events per day at the beginning of the experiment, 128 events per day after an instrument failed, and 97 events per day at the end of the experiment when whale calls increased background noise levels. The microearthquake seismograms are characterized by durations of <1 s and most have single-phase P wave arrivals (i.e., no S arrivals). We accurately located 6207 of the earthquakes, with hypocenters clustered within a narrow depth interval from~50 to 125 m below seafloor on the south and west flanks of the deposit. We model the microearthquakes as reaction-driven fracturing events caused by anhydrite deposition in the secondary circulation system of the hydrothermal mound and show that under reasonable modeling assumptions an average event represents a volume increase of 31-58 cm 3 , yielding an annual (seismogenic) anhydrite deposition rate of 27-51 m 3 .

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Tectonics of the Mid-Atlantic rift valley between the TAG and MARK areas (26–24°N): Evidence for vertical tectonism

Cited by 96 publications

References 28 publications

The Trans-Atlantic Geotraverse hydrothermal field: A hydrothermal system on an active detachment fault

The Trans-Atlantic Geotraverse hydrothermal field: A hydrothermal system on an active detachment fault

The geological record of oceanic crustal accretion and tectonism at slow-spreading ridges

Microearthquake evidence for reaction-driven cracking within the Trans-Atlantic Geotraverse active hydrothermal deposit

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