A rifted inside corner massif on the Mid-Atlantic Ridge at 5°S.

Reston, Timothy J., Weinrebe, Reimer Wilhelm, Grevemeyer, Ingo , Flueh, Ernst R., Mitchell, N.C., Kirstein, L., Kopp, C. and Kopp, Heidrun and Participants of Meteor 47/2 (2002) A rifted inside corner massif on the Mid-Atlantic Ridge at 5°S. Earth and Planetary Science Letters, 200 (3-4). pp. 255-269. DOI 10.1016/S0012-821X(02)00636-2.

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Abstract

The structure of the Mid-Atlantic Ridge at 5°S was investigated during a recent cruise with the FS Meteor. A major dextral transform fault (hereafter the 5°S FZ) offsets the ridge left-laterally by 80 km. Just south of the transform and to the west of the median valley, the inside corner (IC – the region bounded by the ridge and the active transform) is marked by a major massif, characterized by a corrugated upper surface. Fossil IC massifs can also be identified further to the west. Unusually, a massif almost as high as the IC massif also characterizes the outside corner (OC) south of the inactive fracture zone and to the east of the median valley. This OC massif has axis-parallel dimensions identical to the IC massif and both are bounded on their sides closest to the spreading axis by abrupt, steep slopes. An axial volcanic ridge is well developed in the median valley both south of the IC/OC massifs and in an abandoned rift valley to the east of the OC massif, but is absent along the new ridge-axis segment between the IC and OC massifs. Wide-angle seismic data show that between the massifs, the crust of the median valley thins markedly towards the FZ. These observations are consistent with the formation of the OC massif by the rifting of an IC core complex and the development of a new spreading centre between the IC and OC massifs. The split IC massif presents an opportunity to study the internal structure of the footwall of a detachment fault, from the corrugated fault surface to deeper beneath the fault, without recourse to drilling. Preliminary dredging recovered gabbros from the scarp slope of the rifted IC massif, and serpentinites and gabbros from the intersection of this scarp with the corrugated surface. This is compatible with a concentration of serpentinites along the detachment surface, even where the massif internally is largely plutonic in nature.

Document Type: Article
Keywords: spreading centers; fracture zones; transform faults; bathymetry; segmentation; detachment faults
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/S0012-821X(02)00636-2
ISSN: 0012-821X
Expeditions/Models/Experiments:
Date Deposited: 18 Feb 2008 17:25
Last Modified: 15 Nov 2016 10:38
URI: http://oceanrep.geomar.de/id/eprint/3186

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