Young volcanism and related hydrothermal activity at 5°S on the slow-spreading southern Mid-Atlantic Ridge.

Haase, K. M., Petersen, Sven , Koschinsky, A., Seifert, R., Devey, Colin W. , Keir, Robin, Lackschewitz, Klas, Melchert, Bernd, Perner, Mirjam , Schmale, Oliver, Süling, Jörg, Dubilier, N., Zielinski, F. and Fretzdorff, Susanne (2007) Young volcanism and related hydrothermal activity at 5°S on the slow-spreading southern Mid-Atlantic Ridge. Open Access Geochemistry, Geophysics, Geosystems, 8 (Q11002). DOI 10.1029/2006GC001509.

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Abstract

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.

Document Type: Article
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-MI Marine Microbiology
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2006GC001509
ISSN: 1525-2027
Projects: Future Ocean, SPP 1144 "From Mantle to Ocean"
Expeditions/Models/Experiments:
Date Deposited: 03 Dec 2008 16:51
Last Modified: 18 Jul 2018 08:26
URI: http://oceanrep.geomar.de/id/eprint/7730

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