Tectonic structure, evolution, and the nature of oceanic core complexes and their detachment fault zones (13°20′N and 13°30′N, Mid Atlantic Ridge)

Escartín, J., Mével, C., Petersen, Sven, Bonnemains, D., Cannat, M., Andreani, M., Augustin, Nico, Bezos, A., Chavagnac, V., Choi, Y., Godard, M., Haaga, K., Hamelin, C., Ildefonse, B., Jamieson, John, John, B., Leleu, T., MacLeod, C. J., Massot-Campos, M., Nomikou, P., Olive, J. A., Paquet, M., Rommevaux, C., Rothenbeck, Marcel, Steinfuhrer, A., Tominaga, M., Triebe, Lars, Campos, R., Gracias, N. and Garcia, R. (2017) Tectonic structure, evolution, and the nature of oceanic core complexes and their detachment fault zones (13°20′N and 13°30′N, Mid Atlantic Ridge) Geochemistry, Geophysics, Geosystems, 18 (4). pp. 1451-1482. DOI 10.1002/2016GC006775.

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Abstract

Microbathymetry data, in situ observations, and sampling along the 138200N and 138200N oceanic
core complexes (OCCs) reveal mechanisms of detachment fault denudation at the seafloor, links between tectonic
extension and mass wasting, and expose the nature of corrugations, ubiquitous at OCCs. In the initial
stages of detachment faulting and high-angle fault, scarps show extensive mass wasting that reduces their
slope. Flexural rotation further lowers scarp slope, hinders mass wasting, resulting in morphologically complex
chaotic terrain between the breakaway and the denuded corrugated surface. Extension and drag along the fault
plane uplifts a wedge of hangingwall material (apron). The detachment surface emerges along a continuous
moat that sheds rocks and covers it with unconsolidated rubble, while local slumping emplaces rubble ridges
overlying corrugations. The detachment fault zone is a set of anostomosed slip planes, elongated in the alongextension
direction. Slip planes bind fault rock bodies defining the corrugations observed in microbathymetry
and sonar. Fault planes with extension-parallel stria are exposed along corrugation flanks, where the rubble cover
is shed. Detachment fault rocks are primarily basalt fault breccia at 138200N OCC, and gabbro and peridotite
at 138300N, demonstrating that brittle strain localization in shallow lithosphere form corrugations, regardless of
lithologies in the detachment zone. Finally, faulting and volcanism dismember the 138300N OCC, with widespread
present and past hydrothermal activity (Semenov fields), while the Irinovskoe hydrothermal field at the
138200N core complex suggests a magmatic source within the footwall. These results confirm the ubiquitous
relationship between hydrothermal activity and oceanic detachment formation and evolution.

Document Type: Article
Keywords: oceanic detachment fault; hydrothermal field; mid-ocean ridge; faulting; mass wasting; oceanic core complex; ODEMAR cruise, AUV Abyss, ROV Victor6000
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems > Marine Mineralische Rohstoffe
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
Refereed: Yes
DOI etc.: 10.1002/2016GC006775
ISSN: 1525-2027
Expeditions/Models:
Date Deposited: 23 May 2017 11:40
Last Modified: 23 May 2017 11:45
URI: http://eprints.uni-kiel.de/id/eprint/38096

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