Geologic setting of the Snake Pit hydrothermal site: An active vent field on the Mid-Atlantic Ridge |
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| Authors: | Jeffrey A Karson Jennifer R Brown |
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| Institution: | (1) Department of Geology, Duke University, 27706 Durham, NC, USA |
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| Abstract: | TheSnake Pit Hydrothermal Site lies on the axis of the Mid-Atlantic Ridge at 23°22′ N latitude, about 30 km south of the Kane Transform
Intersection. Active ‘black smoker’ vents and a surrounding field of hydrothermal sediment occur at the crest of a laterally
extensive neovolcanic ridge. It is one of the first active hydrothermal vent fields to be found on a slow-spreading ridge
axis and despite significant differences in its geologic setting from those of the East Pacific Rise, has many similarities
to its fast-spreading counterparts. Although preliminary reports have documented many interesting aspects of these vents and
their surroundings, new data collected from the manned submersible ALVIN and the deep-towed ANGUS camera system define the
regional tectonic setting as well as the local geologic environment of this fascinating area.
The Snake Pit vents are located on a local peak of a volcanic constructional ridge at a depth of 3450 m, 700–800 m deeper
than vents known from the East Pacific Rise, Galapagos, or Juan de Fuca spreading centers. The vent field is at least 600
m long and up to 200 m wide and is covered by a thick blanket of greenish to yellow-orange hydrothermal sediment. Both active
and extinct vents are perched along the crests of steep-sided sulfide mounds that reach heights of over 40 m. High-temperature
(350° C) fluids are vented from black smoker chimneys and low-temperature (226° C) fluids seep from sulphide domes and subordinate
anhydrite constructions. Water temperatures, flow rates, fluid chemistries, and mineralization are strikingly similar to vents
of faster spreading ridge crests; however, a somewhat distinct fauna inhabit the area. |
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| Keywords: | Hydrothermal vents Snake Pit Mid-Atlantic Ridge seafloor spreading |
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