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Insights into the internal structure and formation of striated fault surfaces of oceanic detachments from in situ observations (13°20'N and 13°30'N, Mid-Atlantic Ridge)

Insights into the internal structure and formation of striated fault surfaces of oceanic detachments from in situ observations (13°20'N and 13°30'N, Mid-Atlantic Ridge)
Insights into the internal structure and formation of striated fault surfaces of oceanic detachments from in situ observations (13°20'N and 13°30'N, Mid-Atlantic Ridge)
Oceanic detachment faults (ODs) are known to play a significant role in oceanic crustal accretion along slow-spreading ridges, and many display a poorly understood corrugated fault surface. The ODEMAR cruise (Nov-Dec’14) studied the 13°20’N and 13°30’N ODs along the Mid-Atlantic Ridge via extensive microbathymetric surveys with AUV ABYSS (GEOMAR), combined with geological observations and sampling using ROV VICTOR (IFREMER).

The 13°20’N OD is largely intact, with an undisrupted corrugated surface. An abrupt, continuous moat where the OD emerges from the seafloor sloping at ~12-18° continuously sheds rubble onto the OD fault plane, blanketing it. An apron surrounds the detachment dipping ~10-14° towards volcanic rift valley floor thus forming a thin wedge above the active OD fault, which uplifts hangingwall material. In contrast, the 13°30’N OD is cut by recent high-angle faults, and is likely inactive. The OD fault is well exposed along these recent high angle fault scarps, and along mass wasting scarps.

The OD fault displays individual microbathymetric lineations throughout the >150 m of fault zone thickness, that are traced up to ~2 km in the spreading direction. Flanks of individual lineations display fault planes extending ~20-100 m laterally with well-developed, extension-parallel striae. At 13°20’N. These fault surfaces are primarily basalt fault breccias and minor serpentinite. At 13°30’N the scarps cutting the detachment system reveal highly heterogeneous deformation, with phacoidal blocks of undeformed peridotite, gabbro, and basalt enclosed in anastomosing shear zones. Basalt often shows greenschist grade alteration, and is only present in the upper 50 m of the OD fault zone.

In detail, OD faults are characterized by anastomosing zones of localized, strongly anisotropic deformation at different scales (m to km), bounding bodies of largely undeformed rock (basalt, gabbro, peridotite) elongated in the extension direction. Hangingwall material (basalt and dolerite) gets reworked into the fault zone in the green schist facies and effectively accreted to the footwall, both as fault breccia and as large blocks within the fault. Such fine-scale, in situ observations provide unprecedented insights into the three-dimensional and heterogeneous strain localization at OD fault zones.
Escartín, Javier
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Bonnemains, Diane
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Mével, Catherine
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Cannat, Mathilde
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Petersen, Sven
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Augustin, Nico
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Bezos, Antoine
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Chavagnac, Valerie MC
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Choi, Yujin
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Godard, Marguerite
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Haaga, Kristian A.
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Hamelin, Cédric
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Ildefonse, Benoit
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Jamieson, John
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John, Barbara
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Leleu, Thomas
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MacLeod, Christopher J.
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Massot Campos, Miguel
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Nomikou, Paraskevi
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Olive, Jean Arthur
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Paquet, Marine
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Rommevaux-Jestin, Céline
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Rothenbeck, Marcel
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Steinführer, Anja
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Tominaga, Masako
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Triebe, Lars
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Andreani, Muriel
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Garcia, Rafael
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Campos, Ricard
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Escartín, Javier
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Bonnemains, Diane
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Mével, Catherine
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Cannat, Mathilde
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Petersen, Sven
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Augustin, Nico
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Bezos, Antoine
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Chavagnac, Valerie MC
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Choi, Yujin
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Godard, Marguerite
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Haaga, Kristian A.
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Hamelin, Cédric
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Ildefonse, Benoit
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Jamieson, John
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John, Barbara
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Leleu, Thomas
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MacLeod, Christopher J.
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Massot Campos, Miguel
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Nomikou, Paraskevi
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Olive, Jean Arthur
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Paquet, Marine
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Rommevaux-Jestin, Céline
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Rothenbeck, Marcel
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Steinführer, Anja
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Tominaga, Masako
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Triebe, Lars
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Andreani, Muriel
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Garcia, Rafael
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Campos, Ricard
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Escartín, Javier, Bonnemains, Diane, Mével, Catherine, Cannat, Mathilde, Petersen, Sven, Augustin, Nico, Bezos, Antoine, Chavagnac, Valerie MC, Choi, Yujin, Godard, Marguerite, Haaga, Kristian A., Hamelin, Cédric, Ildefonse, Benoit, Jamieson, John, John, Barbara, Leleu, Thomas, MacLeod, Christopher J., Massot Campos, Miguel, Nomikou, Paraskevi, Olive, Jean Arthur, Paquet, Marine, Rommevaux-Jestin, Céline, Rothenbeck, Marcel, Steinführer, Anja, Tominaga, Masako, Triebe, Lars, Andreani, Muriel, Garcia, Rafael and Campos, Ricard (2014) Insights into the internal structure and formation of striated fault surfaces of oceanic detachments from in situ observations (13°20'N and 13°30'N, Mid-Atlantic Ridge). American Geophysical Union, Fall Meeting 2014, , San Francisco, United States. 15 - 19 Dec 2014.

Record type: Conference or Workshop Item (Paper)

Abstract

Oceanic detachment faults (ODs) are known to play a significant role in oceanic crustal accretion along slow-spreading ridges, and many display a poorly understood corrugated fault surface. The ODEMAR cruise (Nov-Dec’14) studied the 13°20’N and 13°30’N ODs along the Mid-Atlantic Ridge via extensive microbathymetric surveys with AUV ABYSS (GEOMAR), combined with geological observations and sampling using ROV VICTOR (IFREMER).

The 13°20’N OD is largely intact, with an undisrupted corrugated surface. An abrupt, continuous moat where the OD emerges from the seafloor sloping at ~12-18° continuously sheds rubble onto the OD fault plane, blanketing it. An apron surrounds the detachment dipping ~10-14° towards volcanic rift valley floor thus forming a thin wedge above the active OD fault, which uplifts hangingwall material. In contrast, the 13°30’N OD is cut by recent high-angle faults, and is likely inactive. The OD fault is well exposed along these recent high angle fault scarps, and along mass wasting scarps.

The OD fault displays individual microbathymetric lineations throughout the >150 m of fault zone thickness, that are traced up to ~2 km in the spreading direction. Flanks of individual lineations display fault planes extending ~20-100 m laterally with well-developed, extension-parallel striae. At 13°20’N. These fault surfaces are primarily basalt fault breccias and minor serpentinite. At 13°30’N the scarps cutting the detachment system reveal highly heterogeneous deformation, with phacoidal blocks of undeformed peridotite, gabbro, and basalt enclosed in anastomosing shear zones. Basalt often shows greenschist grade alteration, and is only present in the upper 50 m of the OD fault zone.

In detail, OD faults are characterized by anastomosing zones of localized, strongly anisotropic deformation at different scales (m to km), bounding bodies of largely undeformed rock (basalt, gabbro, peridotite) elongated in the extension direction. Hangingwall material (basalt and dolerite) gets reworked into the fault zone in the green schist facies and effectively accreted to the footwall, both as fault breccia and as large blocks within the fault. Such fine-scale, in situ observations provide unprecedented insights into the three-dimensional and heterogeneous strain localization at OD fault zones.

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More information

Published date: 2014
Venue - Dates: American Geophysical Union, Fall Meeting 2014, , San Francisco, United States, 2014-12-15 - 2014-12-19

Identifiers

Local EPrints ID: 480191
URI: http://eprints.soton.ac.uk/id/eprint/480191
PURE UUID: 40533c8a-9e14-4f2e-a74e-20a71a459b43
ORCID for Miguel Massot Campos: ORCID iD orcid.org/0000-0002-1202-0362

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Date deposited: 01 Aug 2023 17:01
Last modified: 17 Mar 2024 03:54

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Contributors

Author: Javier Escartín
Author: Diane Bonnemains
Author: Catherine Mével
Author: Mathilde Cannat
Author: Sven Petersen
Author: Nico Augustin
Author: Antoine Bezos
Author: Valerie MC Chavagnac
Author: Yujin Choi
Author: Marguerite Godard
Author: Kristian A. Haaga
Author: Cédric Hamelin
Author: Benoit Ildefonse
Author: John Jamieson
Author: Barbara John
Author: Thomas Leleu
Author: Christopher J. MacLeod
Author: Paraskevi Nomikou
Author: Jean Arthur Olive
Author: Marine Paquet
Author: Céline Rommevaux-Jestin
Author: Marcel Rothenbeck
Author: Anja Steinführer
Author: Masako Tominaga
Author: Lars Triebe
Author: Muriel Andreani
Author: Rafael Garcia
Author: Ricard Campos

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