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Elastic and electrical properties and permeability of serpentinites from Atlantis Massif, Mid-Atlantic Ridge

Elastic and electrical properties and permeability of serpentinites from Atlantis Massif, Mid-Atlantic Ridge
Elastic and electrical properties and permeability of serpentinites from Atlantis Massif, Mid-Atlantic Ridge
Serpentinized peridotites co-exist with mafic rocks in a variety of marine environments including subduction zones, continental rifts and mid-ocean ridges. Remote geophysical methods are crucial to distinguish between them and improve the understanding of the tectonic, magmatic and metamorphic history of the oceanic crust. But, serpentinite peridotites exhibit a wide range of physical properties that complicate such a distinction. We analysed the ultrasonic P- and S-wave velocities (Vp, Vs) and their respective attenuation (Qp−1, Qs−1), electrical resistivity and permeability of four serpentinized peridotite samples from the southern wall of the Atlantis Massif, Mid-Atlantic Ridge, collected during International Ocean Discovery Program Expedition 357. The measurements were taken over a range of loading-unloading stress paths (5–45 MPa), using ∼1.7 cm length, 5 cm diameter samples horizontally extracted from the original cores drilled on the seafloor. The measured parameters showed variable degrees of stress dependence, but followed similar trends. Vp, Vs, resistivity and permeability show good inter-correlations, while relationships that included Qp−1 and Qs−1 are less clear. Resistivity showed high contrast between highly serpentinized ultramafic matrix (>50 Ω m) and mechanically/geochemically altered (magmatic/hydrothermal-driven alteration) domains (<20 Ω m). This information together with the elastic constants (Vp/Vs ratio and bulk moduli) of the samples allowed us to infer useful information about the degree of serpentinization and the alteration state of the rock, contrasted by petrographic analysis. This study shows the potential of combining seismic techniques and controlled source electromagnetic surveys for understanding tectonomagmatic processes and fluid pathways in hydrothermal systems.
0956-540X
686–699
Falcon-Suarez, Ismael
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Bayrakci, Gaye
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Minshull, Tim A.
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North, Laurence J.
65837b6b-40f1-4a1c-ba66-ec6ff2d7f84b
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Rouméjon, Stéphane
bb64129e-5f21-4e4d-92a6-2881baa15234
IODP Expedition 357 Science Party,
0fe8e786-3c07-4f5d-ab9f-8b9cc38025ca
Falcon-Suarez, Ismael
9e8022b5-8799-4326-8d5b-0ed46de3b25a
Bayrakci, Gaye
e0b89aa5-d514-4ecb-91b1-8ed8bd472eda
Minshull, Tim A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
North, Laurence J.
65837b6b-40f1-4a1c-ba66-ec6ff2d7f84b
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Rouméjon, Stéphane
bb64129e-5f21-4e4d-92a6-2881baa15234
IODP Expedition 357 Science Party,
0fe8e786-3c07-4f5d-ab9f-8b9cc38025ca

Falcon-Suarez, Ismael, Bayrakci, Gaye, Minshull, Tim A., North, Laurence J., Best, Angus I., Rouméjon, Stéphane and IODP Expedition 357 Science Party, (2017) Elastic and electrical properties and permeability of serpentinites from Atlantis Massif, Mid-Atlantic Ridge. Geophysical Journal International, 211 (2), 686–699. (doi:10.1093/gji/ggx341).

Record type: Article

Abstract

Serpentinized peridotites co-exist with mafic rocks in a variety of marine environments including subduction zones, continental rifts and mid-ocean ridges. Remote geophysical methods are crucial to distinguish between them and improve the understanding of the tectonic, magmatic and metamorphic history of the oceanic crust. But, serpentinite peridotites exhibit a wide range of physical properties that complicate such a distinction. We analysed the ultrasonic P- and S-wave velocities (Vp, Vs) and their respective attenuation (Qp−1, Qs−1), electrical resistivity and permeability of four serpentinized peridotite samples from the southern wall of the Atlantis Massif, Mid-Atlantic Ridge, collected during International Ocean Discovery Program Expedition 357. The measurements were taken over a range of loading-unloading stress paths (5–45 MPa), using ∼1.7 cm length, 5 cm diameter samples horizontally extracted from the original cores drilled on the seafloor. The measured parameters showed variable degrees of stress dependence, but followed similar trends. Vp, Vs, resistivity and permeability show good inter-correlations, while relationships that included Qp−1 and Qs−1 are less clear. Resistivity showed high contrast between highly serpentinized ultramafic matrix (>50 Ω m) and mechanically/geochemically altered (magmatic/hydrothermal-driven alteration) domains (<20 Ω m). This information together with the elastic constants (Vp/Vs ratio and bulk moduli) of the samples allowed us to infer useful information about the degree of serpentinization and the alteration state of the rock, contrasted by petrographic analysis. This study shows the potential of combining seismic techniques and controlled source electromagnetic surveys for understanding tectonomagmatic processes and fluid pathways in hydrothermal systems.

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Falcon_Suarez_etal_2017_GJI_R2_02_08_2017_accepted - Accepted Manuscript
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Accepted/In Press date: 2 August 2017
e-pub ahead of print date: 14 August 2017
Published date: 1 November 2017

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Local EPrints ID: 412803
URI: http://eprints.soton.ac.uk/id/eprint/412803
ISSN: 0956-540X
PURE UUID: 6aae9a2e-41d8-4069-a14c-0cfe102512e4
ORCID for Tim A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379

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Date deposited: 02 Aug 2017 16:30
Last modified: 07 Oct 2020 01:44

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Contributors

Author: Ismael Falcon-Suarez
Author: Gaye Bayrakci
Author: Tim A. Minshull ORCID iD
Author: Laurence J. North
Author: Angus I. Best
Author: Stéphane Rouméjon
Author: IODP Expedition 357 Science Party

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