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Superposed sedimentary and tectonic block-in-matrix fabrics in a subducted serpentinite mélange (high-pressure Zermatt Saas ophiolite, Western Alps)

Superposed sedimentary and tectonic block-in-matrix fabrics in a subducted serpentinite mélange (high-pressure Zermatt Saas ophiolite, Western Alps)
Superposed sedimentary and tectonic block-in-matrix fabrics in a subducted serpentinite mélange (high-pressure Zermatt Saas ophiolite, Western Alps)

The primary stratigraphic fabric of a chaotic rock unit in the Zermatt Saas ophiolite of the Western Alps was reworked by a polyphase Alpine tectonic deformation. Multiscalar structural criteria demonstrate that this unit was deformed by two ductile subduction-related phases followed by brittle-ductile then brittle deformation. Deformation partitioning operated at various scales, leaving relatively unstrained rock domains preserving internal texture, organization, and composition. During subduction, ductile deformation involved stretching, boudinage, and simultaneous folding of the primary stratigraphic succession. This deformation is particularly well-documented in alternating layers showing contrasting deformation style, such as carbonate-rich rocks and turbiditic serpentinite metasandstones. During collision and exhumation, deformation enhanced the boudinaged horizons and blocks, giving rise to spherical to lozenge-shaped blocks embedded in a carbonate-rich matrix. Structural criteria allow the recognition of two main domains within the chaotic rock unit, one attributable to original broken formations reflecting turbiditic sedimentation, the other ascribable to an original sedimentary mélange. The envisaged geodynamic setting for the formation of the protoliths is the Jurassic Ligurian-Piedmont ocean basin floored by mostly serpentinized peridotites, intensely tectonized by extensional faults that triggered mass transport processes and turbiditic sedimentation.

Broken formation, Ophiolite, Sedimentary mélange, Turbidite, Zermatt Saas
2076-3263
Tartarotti, Paola
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Guerini, Sara
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Rotondo, Francesca
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Festa, Andrea
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Balestro, Gianni
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Bebout, Gray E.
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Cannaò, Enrico
b916f234-dd3e-4355-ba0e-bac4bf85c1fe
Epstein, Gabe S.
b8e7fc5e-77e1-4d6f-923e-0179cd2d3a62
Scambelluri, Marco
4a92c8c1-4f77-4ffa-996f-10a510b5ddf6
Tartarotti, Paola
7b14ab6a-465b-4572-9990-23edacb4e308
Guerini, Sara
f2b10b34-a201-4392-9e8a-9619aa10b818
Rotondo, Francesca
7e05d184-fd35-44db-9b29-b093aeabe708
Festa, Andrea
a976e6a7-68f3-488e-af27-237c737d5d78
Balestro, Gianni
8a3799c1-f5c7-4c40-89fb-b72d1e32ea5d
Bebout, Gray E.
1778415f-5b37-4dd1-a46b-d300c5f813d8
Cannaò, Enrico
b916f234-dd3e-4355-ba0e-bac4bf85c1fe
Epstein, Gabe S.
b8e7fc5e-77e1-4d6f-923e-0179cd2d3a62
Scambelluri, Marco
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Tartarotti, Paola, Guerini, Sara, Rotondo, Francesca, Festa, Andrea, Balestro, Gianni, Bebout, Gray E., Cannaò, Enrico, Epstein, Gabe S. and Scambelluri, Marco (2019) Superposed sedimentary and tectonic block-in-matrix fabrics in a subducted serpentinite mélange (high-pressure Zermatt Saas ophiolite, Western Alps). Geosciences (Switzerland), 9 (8), [358]. (doi:10.3390/geosciences9080358).

Record type: Article

Abstract

The primary stratigraphic fabric of a chaotic rock unit in the Zermatt Saas ophiolite of the Western Alps was reworked by a polyphase Alpine tectonic deformation. Multiscalar structural criteria demonstrate that this unit was deformed by two ductile subduction-related phases followed by brittle-ductile then brittle deformation. Deformation partitioning operated at various scales, leaving relatively unstrained rock domains preserving internal texture, organization, and composition. During subduction, ductile deformation involved stretching, boudinage, and simultaneous folding of the primary stratigraphic succession. This deformation is particularly well-documented in alternating layers showing contrasting deformation style, such as carbonate-rich rocks and turbiditic serpentinite metasandstones. During collision and exhumation, deformation enhanced the boudinaged horizons and blocks, giving rise to spherical to lozenge-shaped blocks embedded in a carbonate-rich matrix. Structural criteria allow the recognition of two main domains within the chaotic rock unit, one attributable to original broken formations reflecting turbiditic sedimentation, the other ascribable to an original sedimentary mélange. The envisaged geodynamic setting for the formation of the protoliths is the Jurassic Ligurian-Piedmont ocean basin floored by mostly serpentinized peridotites, intensely tectonized by extensional faults that triggered mass transport processes and turbiditic sedimentation.

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geosciences-09-00358-v2 - Version of Record
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More information

Accepted/In Press date: 13 August 2019
e-pub ahead of print date: 16 August 2019
Published date: August 2019
Additional Information: This article belongs to the Special Issue Geology of Mélanges
Keywords: Broken formation, Ophiolite, Sedimentary mélange, Turbidite, Zermatt Saas

Identifiers

Local EPrints ID: 444375
URI: http://eprints.soton.ac.uk/id/eprint/444375
ISSN: 2076-3263
PURE UUID: 38324c8e-2bee-4149-8412-2c5e87429c50
ORCID for Francesca Rotondo: ORCID iD orcid.org/0000-0002-3922-9254

Catalogue record

Date deposited: 14 Oct 2020 16:33
Last modified: 26 Nov 2021 03:21

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Contributors

Author: Paola Tartarotti
Author: Sara Guerini
Author: Andrea Festa
Author: Gianni Balestro
Author: Gray E. Bebout
Author: Enrico Cannaò
Author: Gabe S. Epstein
Author: Marco Scambelluri

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