Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS)
The strong morphological similitude of the block-in-matrix fabric of chaotic rock units (mélanges and broken formations) makes problematic the recognition of their primary forming-processes. We present results of the comparison between magnetic fabric and mesoscale structural investigations...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2019-08-01
|
| Series: | Geosciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-3263/9/9/381 |
| _version_ | 1818035907171713024 |
|---|---|
| author | Claudio Robustelli Test Andrea Festa Elena Zanella Giulia Codegone Emanuele Scaramuzzo |
| author_facet | Claudio Robustelli Test Andrea Festa Elena Zanella Giulia Codegone Emanuele Scaramuzzo |
| author_sort | Claudio Robustelli Test |
| collection | DOAJ |
| description | The strong morphological similitude of the block-in-matrix fabric of chaotic rock units (mélanges and broken formations) makes problematic the recognition of their primary forming-processes. We present results of the comparison between magnetic fabric and mesoscale structural investigations of non-metamorphic tectonic, sedimentary, and polygenetic mélanges in the exhumed Late Cretaceous to early Eocene Ligurian accretionary complex and overlying wedge-top basin succession in the Northern Apennines (northwest Italy). Our findings show that the magnetic fabric reveals diagnostic configurations of principal anisotropy of magnetic susceptibility (AMS) axes orientation that are well comparable with the mesoscale block-in-matrix fabric of mélanges formed by different processes. Broken formations and tectonic mélanges show prolate and neutral-to-oblate ellipsoids, respectively, with magnetic fabric elements being consistent with those of the mesoscale anisotropic “structurally ordered” block-in-matrix fabric. Sedimentary mélanges show an oblate ellipsoid with a clear sedimentary magnetic fabric related to downslope gravitational emplacement. Polygenetic mélanges show the occurrence of a cumulative depositional and tectonic magnetic fabric. The comparison of field and laboratory investigations validate the analysis of magnetic features as a diagnostic tool suitable to analytically distinguish the contribution of different mélange forming-processes and their mutual superposition, and to better understand the geodynamic evolution of subduction-accretion complexes. |
| first_indexed | 2024-12-10T07:02:30Z |
| format | Article |
| id | doaj.art-77e242417a4846348549592f5bd94294 |
| institution | Directory Open Access Journal |
| issn | 2076-3263 |
| language | English |
| last_indexed | 2024-12-10T07:02:30Z |
| publishDate | 2019-08-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Geosciences |
| spelling | doaj.art-77e242417a4846348549592f5bd942942022-12-22T01:58:17ZengMDPI AGGeosciences2076-32632019-08-019938110.3390/geosciences9090381geosciences9090381Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS)Claudio Robustelli Test0Andrea Festa1Elena Zanella2Giulia Codegone3Emanuele Scaramuzzo4Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, 10125 Torino, ItalyDipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, 10125 Torino, ItalyDipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, 10125 Torino, ItalyStogit Division, Snam S.p.A., Piazza Santa Barbara 7, 20097 San Donato Milanese, ItalyDipartimento di Scienza ed Alta Tecnologia, Università degli Studi dell’Insubria, Via Valleggio 11, 22100 Como, ItalyThe strong morphological similitude of the block-in-matrix fabric of chaotic rock units (mélanges and broken formations) makes problematic the recognition of their primary forming-processes. We present results of the comparison between magnetic fabric and mesoscale structural investigations of non-metamorphic tectonic, sedimentary, and polygenetic mélanges in the exhumed Late Cretaceous to early Eocene Ligurian accretionary complex and overlying wedge-top basin succession in the Northern Apennines (northwest Italy). Our findings show that the magnetic fabric reveals diagnostic configurations of principal anisotropy of magnetic susceptibility (AMS) axes orientation that are well comparable with the mesoscale block-in-matrix fabric of mélanges formed by different processes. Broken formations and tectonic mélanges show prolate and neutral-to-oblate ellipsoids, respectively, with magnetic fabric elements being consistent with those of the mesoscale anisotropic “structurally ordered” block-in-matrix fabric. Sedimentary mélanges show an oblate ellipsoid with a clear sedimentary magnetic fabric related to downslope gravitational emplacement. Polygenetic mélanges show the occurrence of a cumulative depositional and tectonic magnetic fabric. The comparison of field and laboratory investigations validate the analysis of magnetic features as a diagnostic tool suitable to analytically distinguish the contribution of different mélange forming-processes and their mutual superposition, and to better understand the geodynamic evolution of subduction-accretion complexes.https://www.mdpi.com/2076-3263/9/9/381mélangesAMSmagnetic fabricdiagnostic criteriaLigurian accretionary complexNorthern Apennines |
| spellingShingle | Claudio Robustelli Test Andrea Festa Elena Zanella Giulia Codegone Emanuele Scaramuzzo Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS) Geosciences mélanges AMS magnetic fabric diagnostic criteria Ligurian accretionary complex Northern Apennines |
| title | Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS) |
| title_full | Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS) |
| title_fullStr | Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS) |
| title_full_unstemmed | Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS) |
| title_short | Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS) |
| title_sort | distinguishing the melange forming processes in subduction accretion complexes constraints from the anisotropy of magnetic susceptibility ams |
| topic | mélanges AMS magnetic fabric diagnostic criteria Ligurian accretionary complex Northern Apennines |
| url | https://www.mdpi.com/2076-3263/9/9/381 |
| work_keys_str_mv | AT claudiorobustellitest distinguishingthemelangeformingprocessesinsubductionaccretioncomplexesconstraintsfromtheanisotropyofmagneticsusceptibilityams AT andreafesta distinguishingthemelangeformingprocessesinsubductionaccretioncomplexesconstraintsfromtheanisotropyofmagneticsusceptibilityams AT elenazanella distinguishingthemelangeformingprocessesinsubductionaccretioncomplexesconstraintsfromtheanisotropyofmagneticsusceptibilityams AT giuliacodegone distinguishingthemelangeformingprocessesinsubductionaccretioncomplexesconstraintsfromtheanisotropyofmagneticsusceptibilityams AT emanuelescaramuzzo distinguishingthemelangeformingprocessesinsubductionaccretioncomplexesconstraintsfromtheanisotropyofmagneticsusceptibilityams |