Preprints
https://doi.org/10.5194/egusphere-2023-126
https://doi.org/10.5194/egusphere-2023-126
06 Feb 2023
 | 06 Feb 2023

Kinematics and time-resolved evolution of the main thrust-sense shear zone in the Eo-alpine orogenic wedge (the Vinschgau Shear Zone, Eastern Alps)

Chiara Montemagni, Stefano Zanchetta, Martina Rocca, Igor Maria Villa, Corrado Morelli, Volkmar Mair, and Andrea Zanchi

Abstract. The Vinschgau Shear Zone (VSZ) is one of the largest and most significant shear zones developed in plastic conditions within the Austroalpine domain, juxtaposing the Ötztal and the Texel units to the Campo, Scharl and Sesvenna units during the building of the Eo-alpine Orogen. The VSZ dominates the structural setting of a large portion of the central Austroalpine Late Cretaceous thrust stack. In order to fully assess the evolution of the VSZ, a multi-faceted approach based on detailed multiscale structural and petrochronological analyses has been carried out across representative transects of the shear zone in the Vinschgau Valley. The research has been performed with a view to characterizing kinematics, PT conditions and age of motion of the VSZ.

Our fieldwork-based analyses suggest that the dip of mylonitic foliation increases from W to E with an E-W trending stretching lineation which dips alternatively to the W and to the E, due to later folding related to the Cenozoic crustal shortening. The dominant top to the W-directed shear sense of the mylonites recognized in the field and confirmed by microstructural analyses is in agreement with the exhumation of the upper Austroalpine nappes in the hanging wall of the shear zone: the Texel unit with Late Cretaceous eclogites, the Schneeberg and Ötztal units both affected by Eo-alpine amphibolite-facies metamorphism. Chemical and microstructural analyses suggest deformation temperatures of ca. 350–400 °C during shearing. Timing of deformation along the VSZ has been constrained for the first time through 40Ar/39Ar dating of syn-shearing micas, which reveal a Late Cretaceous age of the VSZ mylonites with ages ranging between 80 and 97 Ma. A systematic younging trend of deformation occurs towards the central part of the shear zone in the studied transects. Vorticity analysis shows a clear decrease in the simple shear component correlated to the younging direction of mica ages towards the core of the shear zone. This evolution is consistent with the growth of a shear zone where strain localizes into its central part during deformation. The defined evolution of the VSZ sheds new light on how large-scale thrust-sense shear zones act and how much exhumation they can accommodate in the frame of an evolving orogenic wedge.

Journal article(s) based on this preprint

24 May 2023
Kinematics and time-resolved evolution of the main thrust-sense shear zone in the Eo-Alpine orogenic wedge (the Vinschgau Shear Zone, eastern Alps)
Chiara Montemagni, Stefano Zanchetta, Martina Rocca, Igor M. Villa, Corrado Morelli, Volkmar Mair, and Andrea Zanchi
Solid Earth, 14, 551–570, https://doi.org/10.5194/se-14-551-2023,https://doi.org/10.5194/se-14-551-2023, 2023
Short summary

Chiara Montemagni et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • AC1: 'Comment on egusphere-2023-126', Chiara Montemagni, 17 Feb 2023
  • RC1: 'Comment on egusphere-2023-126', Paolo Conti, 06 Mar 2023
    • AC2: 'Reply on RC1', Chiara Montemagni, 13 Mar 2023
  • RC2: 'Comment on egusphere-2023-126', Franz Neubauer, 06 Mar 2023
    • AC3: 'Reply on RC2', Chiara Montemagni, 13 Mar 2023

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • AC1: 'Comment on egusphere-2023-126', Chiara Montemagni, 17 Feb 2023
  • RC1: 'Comment on egusphere-2023-126', Paolo Conti, 06 Mar 2023
    • AC2: 'Reply on RC1', Chiara Montemagni, 13 Mar 2023
  • RC2: 'Comment on egusphere-2023-126', Franz Neubauer, 06 Mar 2023
    • AC3: 'Reply on RC2', Chiara Montemagni, 13 Mar 2023

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Chiara Montemagni on behalf of the Authors (30 Mar 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (08 Apr 2023) by Yang Chu
RR by Franz Neubauer (15 Apr 2023)
ED: Publish subject to minor revisions (review by editor) (23 Apr 2023) by Yang Chu
AR by Chiara Montemagni on behalf of the Authors (26 Apr 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (26 Apr 2023) by Yang Chu
ED: Publish as is (26 Apr 2023) by Federico Rossetti (Executive editor)
AR by Chiara Montemagni on behalf of the Authors (27 Apr 2023)

Journal article(s) based on this preprint

24 May 2023
Kinematics and time-resolved evolution of the main thrust-sense shear zone in the Eo-Alpine orogenic wedge (the Vinschgau Shear Zone, eastern Alps)
Chiara Montemagni, Stefano Zanchetta, Martina Rocca, Igor M. Villa, Corrado Morelli, Volkmar Mair, and Andrea Zanchi
Solid Earth, 14, 551–570, https://doi.org/10.5194/se-14-551-2023,https://doi.org/10.5194/se-14-551-2023, 2023
Short summary

Chiara Montemagni et al.

Chiara Montemagni et al.

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Short summary
The Vinschgau Shear Zone is the most significant shear zones developed within the Austroalpine domain and dominated the structural setting of a large portion of central Austroalpine Late Cretaceous thrust stack. Here we explore the timing of deformation and kinematic of the flow along the Vinschgau Shear Zone and we propose that its evolution sheds new light on how large-scale thrust-sense shear zones act and how much exhumation they can accommodate in the frame of an evolving orogenic wedge.