Pseudotachylyte in the Monte Maggiore ophiolitic unit (Alpine Corsica): a possible lateral extension of the Cima di Gratera intermediate-depth Wadati-Benioff paleo-seismic zone
At the northern end of the Cap Corse peninsula, several klippes of ultramafic rocks (peridotite and serpentinite), among which the Monte Maggiore klippe is the least serpentinized one, rest upon continental-crust derived rocks (Centuri gneisses) and basic or metasedimentary schists (Schistes Lustrés...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
EDP Sciences
2018-01-01
|
| Series: | BSGF - Earth Sciences Bulletin |
| Subjects: | |
| Online Access: | https://www.bsgf.fr/articles/bsgf/full_html/2018/04/bsgf180017/bsgf180017.html |
| _version_ | 1818912853874180096 |
|---|---|
| author | Fabbri Olivier Magott Rémi Fournier Marc Etienne Lucas |
| author_facet | Fabbri Olivier Magott Rémi Fournier Marc Etienne Lucas |
| author_sort | Fabbri Olivier |
| collection | DOAJ |
| description | At the northern end of the Cap Corse peninsula, several klippes of ultramafic rocks (peridotite and serpentinite), among which the Monte Maggiore klippe is the least serpentinized one, rest upon continental-crust derived rocks (Centuri gneisses) and basic or metasedimentary schists (Schistes Lustrés). The Monte Maggiore ophiolitic klippe shares several characteristics with the Cima di Gratera klippe located 30 km further south. First, the two units are composed of a lherzolitic peridotite. Second, they record the same succession of metamorphic events. Third, in the Cap Corse tectonic pile, the two units occupy the highest structural position. Several differences are also observed. First, mafic rocks are significantly less abundant in the Monte Maggiore unit, where they are restricted to dykes cross-cutting the peridotite, than in the Cima di Gratera unit, where they constitute an entire sub-unit. Second, pyroxenite layers are more common at Monte Maggiore than at Cima di Gratera. Despite these differences, the Monte Maggiore and Cima di Gratera klippes can be considered as possible lateral equivalents of a single ophiolitic unit having covered the entire Cap Corse before subsequent erosion. Pseudotachylyte of seismic origin is newly discovered in the Monte Maggiore klippe. The host rock is a cataclastic serpentinized peridotite affected by a cataclastic foliation that is either flat-lying or steeply dipping. Pseudotachylyte fault veins are parallel to the host rock cataclastic foliation. The small lateral extension and the small thickness of fault veins along with frequent cross-cutting relationships suggest that the exposed pseudotachylyte most likely results from numerous small magnitude seismic events such as swarms or aftershocks rather than from large magnitude shocks. All these characteristics are also observed at the Cima di Gratera klippe where they are interpreted as the testimonies of a fossil intermediate-depth Wadati-Benioff zone at the time of subduction of the Ligurian Tethys oceanic lithosphere. Mineral assemblages that could constrain the depth of formation of the pseudotachylyte lack in the Monte Maggiore area. Despite this uncertainty, and given the similarities with the Cima di Gratera occurrences, the pseudotachylyte veins newly discovered at Monte Maggiore are tentatively related to the seismic activity linked with the subduction of the Piemonte-Ligurian oceanic lithosphere in Eocene times. This interpretation suggests that the fossil Wadati-Benioff zone could be traced further south in Alpine Corsica and further north in the Piemontese zone of the western Alps. |
| first_indexed | 2024-12-19T23:21:12Z |
| format | Article |
| id | doaj.art-7472af86732d4d96ab2ae9cd6df70046 |
| institution | Directory Open Access Journal |
| issn | 0037-9409 1777-5817 |
| language | English |
| last_indexed | 2024-12-19T23:21:12Z |
| publishDate | 2018-01-01 |
| publisher | EDP Sciences |
| record_format | Article |
| series | BSGF - Earth Sciences Bulletin |
| spelling | doaj.art-7472af86732d4d96ab2ae9cd6df700462022-12-21T20:01:58ZengEDP SciencesBSGF - Earth Sciences Bulletin0037-94091777-58172018-01-011894-61810.1051/bsgf/2018020bsgf180017Pseudotachylyte in the Monte Maggiore ophiolitic unit (Alpine Corsica): a possible lateral extension of the Cima di Gratera intermediate-depth Wadati-Benioff paleo-seismic zoneFabbri OlivierMagott RémiFournier MarcEtienne LucasAt the northern end of the Cap Corse peninsula, several klippes of ultramafic rocks (peridotite and serpentinite), among which the Monte Maggiore klippe is the least serpentinized one, rest upon continental-crust derived rocks (Centuri gneisses) and basic or metasedimentary schists (Schistes Lustrés). The Monte Maggiore ophiolitic klippe shares several characteristics with the Cima di Gratera klippe located 30 km further south. First, the two units are composed of a lherzolitic peridotite. Second, they record the same succession of metamorphic events. Third, in the Cap Corse tectonic pile, the two units occupy the highest structural position. Several differences are also observed. First, mafic rocks are significantly less abundant in the Monte Maggiore unit, where they are restricted to dykes cross-cutting the peridotite, than in the Cima di Gratera unit, where they constitute an entire sub-unit. Second, pyroxenite layers are more common at Monte Maggiore than at Cima di Gratera. Despite these differences, the Monte Maggiore and Cima di Gratera klippes can be considered as possible lateral equivalents of a single ophiolitic unit having covered the entire Cap Corse before subsequent erosion. Pseudotachylyte of seismic origin is newly discovered in the Monte Maggiore klippe. The host rock is a cataclastic serpentinized peridotite affected by a cataclastic foliation that is either flat-lying or steeply dipping. Pseudotachylyte fault veins are parallel to the host rock cataclastic foliation. The small lateral extension and the small thickness of fault veins along with frequent cross-cutting relationships suggest that the exposed pseudotachylyte most likely results from numerous small magnitude seismic events such as swarms or aftershocks rather than from large magnitude shocks. All these characteristics are also observed at the Cima di Gratera klippe where they are interpreted as the testimonies of a fossil intermediate-depth Wadati-Benioff zone at the time of subduction of the Ligurian Tethys oceanic lithosphere. Mineral assemblages that could constrain the depth of formation of the pseudotachylyte lack in the Monte Maggiore area. Despite this uncertainty, and given the similarities with the Cima di Gratera occurrences, the pseudotachylyte veins newly discovered at Monte Maggiore are tentatively related to the seismic activity linked with the subduction of the Piemonte-Ligurian oceanic lithosphere in Eocene times. This interpretation suggests that the fossil Wadati-Benioff zone could be traced further south in Alpine Corsica and further north in the Piemontese zone of the western Alps.https://www.bsgf.fr/articles/bsgf/full_html/2018/04/bsgf180017/bsgf180017.htmlpseudotachylytecataclasiteintermediate-depth seismicityperidotiteWadati-Benioff zoneAlpine Corsica |
| spellingShingle | Fabbri Olivier Magott Rémi Fournier Marc Etienne Lucas Pseudotachylyte in the Monte Maggiore ophiolitic unit (Alpine Corsica): a possible lateral extension of the Cima di Gratera intermediate-depth Wadati-Benioff paleo-seismic zone BSGF - Earth Sciences Bulletin pseudotachylyte cataclasite intermediate-depth seismicity peridotite Wadati-Benioff zone Alpine Corsica |
| title | Pseudotachylyte in the Monte Maggiore ophiolitic unit (Alpine Corsica): a possible lateral extension of the Cima di Gratera intermediate-depth Wadati-Benioff paleo-seismic zone |
| title_full | Pseudotachylyte in the Monte Maggiore ophiolitic unit (Alpine Corsica): a possible lateral extension of the Cima di Gratera intermediate-depth Wadati-Benioff paleo-seismic zone |
| title_fullStr | Pseudotachylyte in the Monte Maggiore ophiolitic unit (Alpine Corsica): a possible lateral extension of the Cima di Gratera intermediate-depth Wadati-Benioff paleo-seismic zone |
| title_full_unstemmed | Pseudotachylyte in the Monte Maggiore ophiolitic unit (Alpine Corsica): a possible lateral extension of the Cima di Gratera intermediate-depth Wadati-Benioff paleo-seismic zone |
| title_short | Pseudotachylyte in the Monte Maggiore ophiolitic unit (Alpine Corsica): a possible lateral extension of the Cima di Gratera intermediate-depth Wadati-Benioff paleo-seismic zone |
| title_sort | pseudotachylyte in the monte maggiore ophiolitic unit alpine corsica a possible lateral extension of the cima di gratera intermediate depth wadati benioff paleo seismic zone |
| topic | pseudotachylyte cataclasite intermediate-depth seismicity peridotite Wadati-Benioff zone Alpine Corsica |
| url | https://www.bsgf.fr/articles/bsgf/full_html/2018/04/bsgf180017/bsgf180017.html |
| work_keys_str_mv | AT fabbriolivier pseudotachylyteinthemontemaggioreophioliticunitalpinecorsicaapossiblelateralextensionofthecimadigrateraintermediatedepthwadatibenioffpaleoseismiczone AT magottremi pseudotachylyteinthemontemaggioreophioliticunitalpinecorsicaapossiblelateralextensionofthecimadigrateraintermediatedepthwadatibenioffpaleoseismiczone AT fourniermarc pseudotachylyteinthemontemaggioreophioliticunitalpinecorsicaapossiblelateralextensionofthecimadigrateraintermediatedepthwadatibenioffpaleoseismiczone AT etiennelucas pseudotachylyteinthemontemaggioreophioliticunitalpinecorsicaapossiblelateralextensionofthecimadigrateraintermediatedepthwadatibenioffpaleoseismiczone |