An off-axis hydrothermal vent field near the Mid-Atlantic Ridge at 30 degrees N.
Evidence is growing that hydrothermal venting occurs not only along mid-ocean ridges but also on old regions of the oceanic crust away from spreading centres. Here we report the discovery of an extensive hydrothermal field at 30 degrees N near the eastern intersection of the Mid-Atlantic Ridge and the Atlantis fracture zone. The vent field--named 'Lost City'--is distinctly different from all other known sea-floor hydrothermal fields in that it is located on 1.5-Myr-old crust, nearly 15 km from the spreading axis, and may be driven by the heat of exothermic serpentinization reactions between sea water and mantle rocks. It is located on a dome-like massif and is dominated by steep-sided carbonate chimneys, rather than the sulphide structures typical of 'black smoker' hydrothermal fields. We found that vent fluids are relatively cool (40-75 degrees C) and alkaline (pH 9.0-9.8), supporting dense microbial communities that include anaerobic thermophiles. Because the geological characteristics of the Atlantis massif are similar to numerous areas of old crust along the Mid-Atlantic, Indian and Arctic ridges, these results indicate that a much larger portion of the oceanic crust may support hydrothermal activity and microbial life than previously thought.
Kelley
D S
DS
University of Washington, School of Oceanography, Seattle, Washington 98195, USA. kelley@ocean.washington.edu
Karson
J A
JA
Blackman
D K
DK
Früh-Green
G L
GL
Butterfield
D A
DA
Lilley
M D
MD
Olson
E J
EJ
Schrenk
M O
MO
Roe
K K
KK
Lebon
G T
GT
Rivizzigno
P
P
D001267:Atlantic Ocean; D019418:Evolution, Chemical; D019015:Geologic Sediments; D008386:Marine Biology; D008903:Minerals; D000069497:Origin of Life; D012623:Seawater; D013696:Temperature; D014871:Water Microbiology; D014961:X-Ray Diffraction
D008903:Minerals