Open AccessYoung volcanism and related hydrothermal activity at 5°S on the slow‐spreading southern Mid‐Atlantic Ridge
Author(s) -
Haase K. M.,
Petersen S.,
Koschinsky A.,
Seifert R.,
Devey C. W.,
Keir R.,
Lackschewitz K. S.,
Melchert B.,
Perner M.,
Schmale O.,
Süling J.,
Dubilier N.,
Zielinski F.,
Fretzdorff S.,
GarbeSchönberg D.,
Westernströer U.,
German C. R.,
Shank T. M.,
Yoerger D.,
Giere O.,
Kuever J.,
Marbler H.,
Mawick J.,
Mertens C.,
Stöber U.,
Walter M.,
OstertagHenning C.,
Paulick H.,
Peters M.,
Strauss H.,
Sander S.,
Stecher J.,
Warmuth M.,
Weber S.
Publication year - 2007
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2006gc001509
Subject(s) - geology , seafloor spreading , hydrothermal circulation , volcano , lava , ridge , basalt , mid ocean ridge , volcanism , submarine volcano , mid atlantic ridge , hydrothermal vent , geochemistry , magma , petrology , earth science , oceanography , seismology , paleontology , tectonics
The effect of volcanic activity on submarine hydrothermal systems has been well documented along fast‐ and intermediate‐spreading centers but not from slow‐spreading ridges. Indeed, volcanic eruptions are expected to be rare on slow‐spreading axes. Here we report the presence of hydrothermal venting associated with extremely fresh lava flows at an elevated, apparently magmatically robust segment center on the slow‐spreading southern Mid‐Atlantic Ridge near 5°S. Three high‐temperature vent fields have been recognized so far over a strike length of less than 2 km with two fields venting phase‐separated, vapor‐type fluids. Exit temperatures at one of the fields reach up to 407°C, at conditions of the critical point of seawater, the highest temperatures ever recorded from the seafloor. Fluid and vent field characteristics show a large variability between the vent fields, a variation that is not expected within such a limited area. We conclude from mineralogical investigations of hydrothermal precipitates that vent‐fluid compositions have evolved recently from relatively oxidizing to more reducing conditions, a shift that could also be related to renewed magmatic activity in the area. Current high exit temperatures, reducing conditions, low silica contents, and high hydrogen contents in the fluids of two vent sites are consistent with a shallow magmatic source, probably related to a young volcanic eruption event nearby, in which basaltic magma is actively crystallizing. This is the first reported evidence for direct magmatic‐hydrothermal interaction on a slow‐spreading mid‐ocean ridge.