In:
Earth and planetary science letters, Amsterdam [u.a.] : Elsevier, 1966, 275(2008), 1/2, Seite 61-69, 1385-013X
In:
volume:275
In:
year:2008
In:
number:1/2
In:
pages:61-69
Description / Table of Contents:
During segment-scale studies of the southern Mid-Atlantic Ridge (MAR), 712° S, we found evidence in the water column for high-temperature hydrothermal activity, off-axis, east of Ascension Island. Extensive water column and seafloor work using both standard CTD and deep submergence AUV and ROV deployments led to the discovery and sampling of the Drachenschlundʺ (Dragon Throatʺ) black smoker vent at 8ʿ17.87? S/13ʿ30.45? W in 2915 m water depth. The vent is flanked by several inactive chimney structures in a field we have named Nibelungenʺ. The site is located 6 km south of a non-transform offset between two adjacent 2nd-order ridge-segments and 9 km east of the presently-active, northward-propagating A2 ridge-segment, on a prominent outward-facing fault scarp. Both vent-fluid compositions and host-rock analyses show this site to be an ultramafic-hosted system, the first of its kind to be found on the southern MAR. The thermal output of this single vent, based on plume rise-height information, is estimated to be 60 ± 15 MW. This value is high for a single black smokerʺ vent but small for an entire field. The tectonic setting and low He content of the vent fluids imply that high-temperature off-axis venting at Drachenschlundʺ is driven not by magmatic processes, as at the majority of on-axis hydrothermal systems, but by residual heat minedʺ from the deeper lithosphere. Whether this heat is being extracted from high-temperature mantle peridotites or deep crustal cumulates formed at the duellingʺ non-transfrom offset is unclear, in either case the Drachenschlund vent provides the first direct observations of how cooling of deeper parts of the lithosphere, at least at slow-spreading ridges, may be occurring.
Type of Medium:
Online Resource
Pages:
Ill., grap. Darst
ISSN:
1385-013X
DOI:
10.1016/j.epsl.2008.08.010
Language:
English
Permalink
