Alpine metamorphic and tectonic evolution of the Inzecca‐Ghisoni area (southern Alpine Corsica, France)

Garfagnoli, Francesca; Menna, F.; Pandeli, Enrico; Principi, Gianfranco

doi:10.1002/gj.1141

Cited by 18 publications

(23 citation statements)

References 41 publications

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“…Lithological assemblages present strong similarities with the lower continental crust exposed in the Ivrea zone of the Alps [ Libourel , ]. The complex is bordered to the north by the sedimentary Caporalino unit, to the south and east by the Schistes Lustrés and ophiolites of the Inzecca unit, and to the west by the Corte Slices and sinistral strike‐slip Central Corsica Fault Zone, a band of north‐south deformation separating Alpine and Variscan Corsica [ Maluski et al , ; Waters , ; Garfagnoli et al , ]. Several subunits bounded by low‐ T Alpine shear zones and faults have been differentiated within the Santa Lucia nappe complex, including the Granitic Complex, Belli Piani unit, Murato unit, and Tralonca unit [ Zibra , ; Beltrando et al , ].…”

Section: Geologic Settingmentioning

confidence: 99%

Tracing the thermal evolution of the Corsican lower crust during Tethyan rifting

et al. 2016

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Continental rifting requires thinning the continental lithosphere from ~120 km to <20 km by a series of processes which each impart a characteristic thermal signature to the extending lithosphere. Here high‐resolution thermochronology is used to trace the synrift thermal evolution within a lower crustal section of an upper plate hyperextended margin sampled in Corsica. Novel zircon, rutile, and apatite 206Pb/238U depth profiling coupled with garnet trace element diffusion modeling provide compelling evidence for rift‐related crustal reheating. A Jurassic thermal pulse is recorded in the footwall of the Belli Piani Shear Zone (BPSZ), where 200–180 Ma zircon 206Pb/238U overgrowth ages on Permian core populations and the preservation of stranded diffusion profiles in resorbed garnets implies the dominant footwall fabric formed as a result of high‐temperature (T ~ 800°C) ductile thinning of the lower crust. Conductive reheating of middle crustal rocks in the immediate BPSZ hanging wall, demonstrated by Jurassic apatite 206Pb/238U ages, was likely achieved by synkinematic juxtaposition against the hot footwall and wholesale conductive steepening of geothermal gradients. Subsequent rapid cooling from 180 to 160 Ma, coeval with extensional unroofing of the footwall, underscores the importance of extreme ductile thinning during crustal hyperextension. The results of this study suggest that early lithospheric‐scale depth‐dependent thinning follows an early phase of diffuse rifting and tectonic subsidence and triggers crustal reheating during early hyperextension. Continued extension results in rapid exhumation and cooling of the lower crust, extreme crustal attenuation, and mantle exhumation followed by relaxation to a steady state thermal field coeval with the start of seafloor spreading.

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Section: Geologic Settingmentioning

confidence: 99%

Tracing the thermal evolution of the Corsican lower crust during Tethyan rifting

et al. 2016

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“…1), each of them corresponding to different peak metamorphic con- These occurrences document the progressive underthrusting of these units down to different depths and their insequence contractional exhumation within an Alpine-age, east-dipping subduction system (Mattauer et al, 1981;Bezert and Caby, 1988;Jolivet et al, 1990;Garfagnoli et al, 2009;Molli and Malavieille, 2011;Maggi et al, 2012;Di Rosa et al, 2016;Guyedan et al, 2017;Beaudoin et al, 2017).…”

Section: Introductionmentioning

confidence: 95%

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Molli

Menegon

Malasoma³

2017

Solid Earth

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Abstract. The switching in deformation mode (from distributed to localized) and mechanisms (viscous versus frictional) represent a relevant issue in the frame of crustal deformation, being also connected with the concept of the brittle-"ductile" transition and seismogenesis. In a subduction environment, switching in deformation mode and mechanisms and scale of localization may be inferred along the subduction interface, in a transition zone between the highly coupled (seismogenic zone) and decoupled deeper aseismic domain (stable slip). However, the role of brittle precursors in nucleating crystal-plastic shear zones has received more and more consideration being now recognized as fundamental in some cases for the localization of deformation and shear zone development, thus representing a case in which switching deformation mechanisms and scale and style of localization (deformation mode) interact and relate to each other. This contribution analyses an example of a millimetrescale shear zone localized by brittle precursor formed within a host granitic protomylonite. The studied structures, developed in ambient pressure-temperature (P -T ) conditions of low-grade blueschist facies (temperature T of ca. 300 • C and pressure P ≥ 0.70 GPa) during involvement of Corsican continental crust in the Alpine subduction. We used a multidisciplinary approach by combining detailed microstructural and petrographic analyses, crystallographic preferred orientation by electron backscatter diffraction (EBSD), and palaeopiezometric studies on a selected sample to support an evolutionary model and deformation path for subducted continental crust. We infer that the studied structures, possibly formed by transient instability associated with fluctuations of pore fluid pressure and episodic strain rate variations, may be considered as a small-scale example of fault behaviour associated with a cycle of interseismic creep and coseismic rupture or a new analogue for episodic tremors and slow-slip structures. Our case study represents, therefore, a fossil example of association of fault structures related to stick-slip strain accommodation during subduction of continental crust.

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“…In this framework, a stack of continental units affected by high-pressure (HP) metamorphism during the Early Tertiary has been recognized in the last thirty years in the western areas of Alpine Corsica (e.g. Gibbons and Horak, 1984;Daniel et al, 1996;Tribuzio and Giacomini, 2002;Garfagnoli et al, 2009, Maggi et al, 2012Rossetti et al, 2015 and references therein). These continental units were deformed when the European continental margin, still attached to the downgoing oceanic slab, was subjected to underthrusting, accretion and subsequent exhumation.…”

Section: Introductionmentioning

confidence: 99%

Syn‐convergence exhumation of continental crust: evidence from structural and metamorphic analysis of the Monte Cecu area, Alpine Corsica (Northern Corsica, France)

et al. 2016

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In the Corsica Island, a stack of metamorphic continental units derived from the European continental margin is thrust over a pre‐Alpine basement during the convergence‐related processes in the Late Eocene–Early Miocene time span. The Piedigriggio‐Prato Unit is representative of these units. Its tectono‐metamorphic history has been reconstructed by an integrated approach, ranging from map‐ to meso‐ and microscopic scale analyses. This unit is characterized by a polyphase deformation history that consists of three deformation phases developed under retrograde metamorphism ranging from blueschist to sub‐greenschist facies metamorphic conditions. At the map‐scale, the Piedigriggio‐Prato Unit is characterized by km‐size isoclinal folds deformed by open to closed recumbent folds producing Type 3 fold interference pattern. The features of the deformations and the P–T conditions suggest that the first two phases were acquired during the ductile extrusion of the Piedigriggio‐Prato Unit. Before the Early Miocene, the gravitational collapse of over‐thickened continental crust produced vertical shortening and the consequently recumbent F3 folds. The exhumation history of the Piedigriggio‐Prato Unit can be viewed as representative for the exhumation of a continental crust fragment during the transition from the continental subduction to the continental collision. Copyright © 2016 John Wiley & Sons, Ltd.

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Alpine metamorphic and tectonic evolution of the Inzecca‐Ghisoni area (southern Alpine Corsica, France)

Cited by 18 publications

References 41 publications

Tracing the thermal evolution of the Corsican lower crust during Tethyan rifting

Tracing the thermal evolution of the Corsican lower crust during Tethyan rifting

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Syn‐convergence exhumation of continental crust: evidence from structural and metamorphic analysis of the Monte Cecu area, Alpine Corsica (Northern Corsica, France)

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