History and geochemistry of a metalliferous sediment core from the Mid-Atlantic Ridge at 26°N

Metz, Simone; Trefry, John H.; Nelsen, Terry A.

doi:10.1016/0016-7037(88)90294-3

Cited by 81 publications

(50 citation statements)

References 26 publications

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“…However, a dredged Mn oxide sample attests to an earlier low-temperature episode at ~75 ka (Lalou et al, 1995). A sediment core collected 0.5 km west of the Alvin Zone contains high concentrations of hydrothermally-derived material dating from 6 and 8.5 ka suggesting more recent activity (Metz et al, 1988).…”

Section: The Alvin Zonementioning

confidence: 95%

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: The Alvin Zonementioning

confidence: 95%

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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“…Radiometric dating suggests intermittent hydrothermal activity over at least 75,000 years (Lalou et al, 1995), and warm fluids (22.5°C) have been observed in the northern Alvin zone (Rona et al, 1998;White et al, 1998). Metalliferous sediments in this area represent different styles of venting (high temperature focused or low temperature diffuse) and modes of deposition (mass wasting or plume fall-out) (e.g., Thompson et al, 1985;Metz et al, 1988;German et al, 1993;Mills et al, 1993).…”

Section: Geological Setting: Metalliferous Sediments At Tagmentioning

confidence: 99%

“…Large transition metal enrichments occur in sediments surrounding submarine hydrothermal vent systems (Metz et al, 1988;German et al, 1993;Mills et al, 1993), with a significant proportion of the metals being derived from mass wasting and slumping of primary massive sulphides. Sediments close to the vents contain a high proportion of sulphides, and their juxtaposition with oxic seawater produces a substrate that contains sharp redox, pH and temperature gradients.…”

Section: Introductionmentioning

confidence: 99%

The role of prokaryotes in subsurface weathering of hydrothermal sediments: A combined geochemical and microbiological investigation

Severmann

Mills

Palmer

et al. 2006

Geochimica et Cosmochimica Acta

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“…Metz et al 1988). Enrichments of the same elements are encountered among the black schists associated with serpentinite-skarn-quartz rock assemblage in the Kainuu and Outokumpu areas.…”

Section: High Sulphur Isotope T~34s Values In Base-metal-richmentioning

confidence: 99%

Geochemical evidence for the hydrothermal origin of sulphur, base metals and gold in Proterozoic metamorphosed black shales, Kainuu and Outokumpu areas, Finland

Loukola-Ruskeeniemi

1991

Mineral. Deposita

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Metamorphosed black shale formations 120 150 m thick with median concentrations of 7% non-carbonate carbon and 6 8% sulphur are abundantly met in drill cores in the Kainuu and Outokumpu areas. Carbon isotope c~t3C values are comparable to the average isotopic composition of non-carbonate carbon in sedimentary rocks. The rare earth element patterns show cerium depletion, indicating a marine origin. Base metal concentrations in black shales are high in the Talvivaara mineralization (ore estimate: 300 Mt with 0.26% Ni, 0.14% Cu and 0.53% Zn) and in the vicinity of ophiolite complexes. In the Kainuu schist belt, the median value for gold is 35 ppb (max 170 ppb) in the western part and 16 ppb (max 180 ppb) in the east. Highest platinum and palladium concentrations encountered are 60-70 ppb. It is shown that in the Kainuu black shales, concentrations of sulphur, base metals and precious metals have been increased by hydrothermal processes, as indicated by positive europium anomalies, elevated mercury concentrations (max 7.5 ppm), high sulphur isotope 634S values and the enrichment of sulphur and base metals relative to carbon. The processes operative during the deposition of these shales find an analogy in recent processes in ocean ridge spreading axes.Black shales were originally argillaceous sediments containing organic matter. Their chemical composition has therefore been affected by numerous factors, including physicochemical conditions, prevailing organisms, the chemical composition of the water during deposition and the composition of detrital material. The hydrothermal activity leaves fingerprints in the mineralogy and geochemistry of sediments depositing near the vents (e.g. McMurray 1990). Hydrothermal fluids may also add metals to a black shale sediment later, during diagenesis, as indicated by studies on the Kupferschiefer (Jowett etal. 1987; Piittmann and Gobel 1990). In addition, metamorphic and tectonic remobilization may affect the chemical composition of shale.In a preliminary study (Ruskeeniemi etal. 1986;Ruskeeniemi 1988, the chemical characteristics of metamorphosed black shales were studied in 16 localities in the Proterozoic of Finland, to discover whether hydrothermal activity is reflected in their chemical composition, and, if so, whether the element ratios could be used in ore exploration. The promising nature of the results encouraged us to begin a detailed study in eastern Finland, where the Outokumpu Cu-Co-Zn-Au ore deposits and the Talvivaara Ni-Cu-Zn mineralization are located. The present publication reports on this work and represents a progress report on the total research, which will continue up until 1992.In the following, metamorphosed black shale is referred to as black schist.

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History and geochemistry of a metalliferous sediment core from the Mid-Atlantic Ridge at 26°N

Cited by 81 publications

References 26 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 role of prokaryotes in subsurface weathering of hydrothermal sediments: A combined geochemical and microbiological investigation

Geochemical evidence for the hydrothermal origin of sulphur, base metals and gold in Proterozoic metamorphosed black shales, Kainuu and Outokumpu areas, Finland

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