Anomalous water temperatures over Mid-Atlantic Ridge crest at 26° North latitude

Rona, Peter A.; McGregor, Bonnie A.; Betzer, Peter R.; Bolger, G.W.; Krause, Dale C.

doi:10.1016/0011-7471(75)90048-0

Cited by 40 publications

(23 citation statements)

References 10 publications

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“…Zones of low-and high-temperature activity, as well as two major areas of inactive sulfide deposits, have been mapped in a small, 5 × 5 km area on the hanging wall of the detachment fault (Figure 1) (e.g., Rona et al, 1975Rona et al, , 1986Rona et al, , 1993aThompson et al, 1985;White et al, 1998). The geological and geochemical characteristics of the active and inactive zones have been synthesized in detail by Rona et al (1993a, b;, Tivey et al (1995), and Humphris and Tivey (2000); here we provide only a brief overview.…”

Section: Geological and Geochemical Characteristics Of The Tag Hydrotmentioning

confidence: 99%

“…The TAG hydrothermal field on the Mid-Atlantic Ridge (26°08'N) was first located through detection of low temperature hydrothermal activity and mineralization during the NOAA Trans-Atlantic Geotraverse (TAG) project led by Peter Rona in 1972-1973(Scott et al, 1974aRona et al, 1975). Since the discovery in 1985 of the first high temperature vents, massive sulfide deposits, and new vent ecosystems in the Atlantic Ocean again by Peter Rona (Rona at el., 1986), the TAG hydrothermal field has served as a major 'type' example of a massive sulfide deposit on a slow-spreading ridge, particularly with its similarities to sulfide deposits in Cyprus (e.g., Herzig et al, 1991;Hannington et al, 1998;Humphris and Cann, 2000).…”

Section: Introductionmentioning

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: Geological and Geochemical Characteristics Of The Tag Hydrotmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…The valley and flank axis of the ridge in the TAG area are deeply incised by normal faults resulting in a relief of about 2000 m from the floor of the broad axial valley to the top of the rift. The hydrothermal deposits and their settings were intensively studied as early as 1972, as a part of the TAG project (Rona et al, 1975). But the active high-temperature mound was discovered in 1985 Thompson et al, 1988).…”

Section: Geologic Backgroundmentioning

confidence: 99%

“…This site is well known, as it has been the subject of ongoing interdisciplinary studies since the discovery of low-temperature hydrothermal activity and mineralization in 1972−1973 during the Trans-Atlantic Geotraverse project of the National Oceanic and Atmospheric Administration (Rona et al, 1975). 2.…”

Section: Introductionmentioning

confidence: 99%

Lead isotopic compositions of the TAG mineralization, Mid-Atlantic Ridge, 26°08'N

Andrieux¹,

Honnorez²,

Lancelot³

1998

Proceedings of the Ocean Drilling Program

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Lead isotope analyses were performed on sulfides from the Trans-Atlantic Geotraverse (TAG) hydrothermal site, located at 26°08′N, on the unsedimented, slow-spreading Mid-Atlantic Ridge, which is characterized by a high Pb isotopic heterogeneity of the basalts erupting along its axis. Pb isotope ratios of TAG massive sulfides are very uniform. Reported in Pb-Pb diagrams, TAG sulfide data plot on the Northern Hemisphere Reference Line and define a small domain compared with the larger field of the Mid-Atlantic Ridge basalts, which suggests that the main lead sources for the TAG mineralization are the components of the upper oceanic crust. The means of the Pb isotopic compositions of TAG sulfides and neighboring basalts are similar, and identical to the lead composition of present TAG hydrothermal vent fluid. These data suggest that the Pb isotopic ratios of TAG sulfides reflect the average isotope composition of the upper part of the oceanic crust affected by the large-scale hydrothermal fluid circulation, and that the Pb isotopic compositions of the hydrothermal vent fluids recorded in recent and ancient sulfides remain constant during the active interval of a main hydrothermal vent field such as TAG.

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“…Previous investigations have described various aspects of the TAG hydrothermal field: discovery (Rona et al, 1975(Rona et al, , 1984Thompson et al, 1985), geology (Rona et al, 1993), hydrothermal precipitates and fluid chemistry Mills, 1995), and mineralogy of the primary and secondary (Hannington et al, 1988;Hannington, 1993) mineral phases of hydrothermal precipitates. The only previous sulfide δ 34 S values reported from TAG were included in a paper by Lein et al (1993).…”

Section: Introductionmentioning

confidence: 99%

Detailed sulfurisotope investigation of the TAG hydrothermal mound and stockwork zone, 26°N, Mid-Atlantic Ridge

Gemmell¹,

Sharpe²

1998

Proceedings of the Ocean Drilling Program

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Drilling of the Trans-Atlantic Geotraverse (TAG) hydrothermal mound and underlying stockwork zone has revealed a complex internal stratigraphy consisting of, with increasing depth, massive pyrite and pyrite breccias, with significant chalcopyrite and sphalerite in places, pyrite-anhydrite breccias, pyrite-silica breccias, silicified wallrock breccias, and chloritized basalt breccias. Several stages of quartz pyrite ± chalcopyrite veins occur in the stockwork zone and lower portions of the mound whereas anhydrite ± pyrite ± chalcopyrite veins are common within the central and upper parts of the mound.A detailed sulfur-isotope investigation of sulfides and sulfates within mound and the underlying stockwork zone has revealed that the overall range of sulfide δ 34 S analyses is from 0.35‰ to 10.27‰, with a mean of 7.20‰. Anhydrite has a mean δ 34 S value of 21.10‰ within a tight range of 20.55‰-21.56‰.There are distinct differences in δ 34 S values between the different textural types of pyrite (massive sulfide, breccia clasts, disseminations associated with alteration, and veins) within the hydrothermal mound and stockwork zone. The massive sulfide and breccia clasts have a similar distribution of isotope values (δ 34 S = 6‰-8‰), however the δ 34 S values of the disseminated pyrite associated with the alteration are distinctly heavier (δ 34 S = 8‰-10‰). Vein sulfides have the lightest δ 34 S values (δ 34 S = 5‰-7‰) at TAG. The sulfur-isotope values measured at TAG are, in general, the heaviest reported for unsedimented mid-ocean ridge deposits.A sulfur-isotope model is proposed to account for the heavy δ 34 S signature (compared to other sediment-free hydrothermal systems), the distribution of δ 34 S values from the various textural styles and the spatial distribution of the δ 34 S values both laterally and vertically throughout the hydrothermal mound and underlying stockwork zone. The two initial sources of sulfur during the life of the TAG hydrothermal system are seawater sulfate (δ 34 S = 21‰) and mid-ocean ridge basalt (MORB) derived sulfur (δ 34 S = 0‰-1‰). Variations in δ 34 S values at TAG can be explained in a model where totally to partially reduced seawater sulfate of shallow origin mixes with a deep hydrothermal fluid dominated by MORB sulfur and interacts with previously formed sulfide and sulfate minerals in the upper parts of the stockwork zone and within the mound. Deep subseafloor processes cause the initial hydrothermal fluids entering the TAG system at depth to have a δ 34 S value of approximately 0‰-1‰. This fluid mixes with locally entrained partially reduced seawater in the upper parts of the subseafloor stockwork system (created by local hydrothermal convection though the porous and permeable mound and stockwork zone) and creates a modified hydrothermal fluid with a δ 34 S value of approximately 6‰−7‰. The fluid rises to the seafloor, precipitating pyrite in the quartz-pyrite veins (δ 34 S = 6‰−7‰) in the upper parts of the stockwork, and mixes with cold seawater, which causes rapid pr...

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Anomalous water temperatures over Mid-Atlantic Ridge crest at 26° North latitude

Cited by 40 publications

References 10 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

Lead isotopic compositions of the TAG mineralization, Mid-Atlantic Ridge, 26°08'N

Detailed sulfurisotope investigation of the TAG hydrothermal mound and stockwork zone, 26°N, Mid-Atlantic Ridge

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Anomalous water temperatures over Mid-Atlantic Ridge crest at 26° North latitude

Cited by 40 publications

References 10 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

Lead isotopic compositions of the TAG mineralization, Mid-Atlantic Ridge, 26°08'N

Detailed sulfurisotope investigation of the TAG hydrothermal mound and stockwork zone, 26°N, Mid-Atlantic Ridge

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Detailed sulfurisotope investigation of the TAG hydrothermal mound and stockwork zone, 26°N, Mid-Atlantic Ridge