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Open AccessArticle

Superposed Sedimentary and Tectonic Block-In-Matrix Fabrics in a Subducted Serpentinite Mélange (High-Pressure Zermatt Saas Ophiolite, Western Alps)

1
Dipartimento di Scienze della Terra, Università degli Studi di Milano, via Mangiagalli 34, 20133 Milano, Italy
2
Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, 10125 Torino, Italy
3
Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, PA 18015, USA
4
Istituto di Geoscienze e Georisorse, CNR, Via Moruzzi 1, 56124 Pisa, Italy
5
Dipartimento di Scienze della Terra Ambiente e Vita, Università di Genova, Corso Europa, 26, 16132 Genova, Italy
*
Author to whom correspondence should be addressed.
Geosciences 2019, 9(8), 358; https://doi.org/10.3390/geosciences9080358
Received: 6 July 2019 / Revised: 9 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
(This article belongs to the Special Issue Geology of Mélanges)
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. View Full-Text
Keywords: sedimentary mélange; broken formation; ophiolite; Zermatt Saas; turbidite sedimentary mélange; broken formation; ophiolite; Zermatt Saas; turbidite
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MDPI and ACS Style

Tartarotti, P.; Guerini, S.; Rotondo, F.; Festa, A.; Balestro, G.; Bebout, G.E.; Cannaò, E.; Epstein, G.S.; Scambelluri, M. Superposed Sedimentary and Tectonic Block-In-Matrix Fabrics in a Subducted Serpentinite Mélange (High-Pressure Zermatt Saas Ophiolite, Western Alps). Geosciences 2019, 9, 358. https://doi.org/10.3390/geosciences9080358

AMA Style

Tartarotti P, Guerini S, Rotondo F, Festa A, Balestro G, Bebout GE, Cannaò E, Epstein GS, Scambelluri M. Superposed Sedimentary and Tectonic Block-In-Matrix Fabrics in a Subducted Serpentinite Mélange (High-Pressure Zermatt Saas Ophiolite, Western Alps). Geosciences. 2019; 9(8):358. https://doi.org/10.3390/geosciences9080358

Chicago/Turabian Style

Tartarotti, Paola; Guerini, Sara; Rotondo, Francesca; Festa, Andrea; Balestro, Gianni; Bebout, Gray E.; Cannaò, Enrico; Epstein, Gabe S.; Scambelluri, Marco. 2019. "Superposed Sedimentary and Tectonic Block-In-Matrix Fabrics in a Subducted Serpentinite Mélange (High-Pressure Zermatt Saas Ophiolite, Western Alps)" Geosciences 9, no. 8: 358. https://doi.org/10.3390/geosciences9080358

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