Tectono-metamorphic history of the ophiolitic Lento unit (northern Corsica): evidences for the complexity of accretion-exhumation processes in a fossil subduction system

The Alpine Corsica (Corsica Island, France) is characterized by a stack of continent- and ocean-derived tectonic units, known as Schistes Lustres complex. This complex is affected by deformation and metamorphic imprint achieved during Late Cretaceous – Early Tertiary subduction- related processes connected with the closure of the Ligure-Piemontese oceanic basin and subsequent continental collision. In the Schistes Lustres complex, the Lento oceanic unit is characterized by four deformation phases, from D1 to D4 phase. The D1 phase, characterized by blueschist metamorphism, is regarded as related to coherent underplating in a subduction zone at a depth of about 25-30 km. The subsequent deformation phases can be referred to exhumation history, as suggested by the continuous decrease of metamorphic conditions. The transition from accretion to exhumation is represented by the D2 phase, achieved during the development of a duplex structure of accreted units. The D3 phase is in turn achieved by a further horizo..

Robotic Rehabilitation and Multimodal Instrumented Assessment of Post-stroke Elbow Motor Functions—A Randomized Controlled Trial Protocol

Background: The reliable assessment, attribution, and alleviation of upper-limb joint stiffness are essential clinical objectives in the early rehabilitation from stroke and other neurological disorders, to prevent the progression of neuromuscular pathology and enable proactive physiotherapy toward functional recovery. However, the current clinical evaluation and treatment of this stiffness (and underlying muscle spasticity) are severely limited by their dependence on subjective evaluation and manual limb mobilization, thus rendering the evaluation imprecise and the treatment insufficiently tailored to the specific pathologies and residual capabilities of individual patients. Methods: To address these needs, the proposed clinical trial will employ the NEUROExos Elbow Module (NEEM), an active robotic exoskeleton, for the passive mobilization and active training of elbow flexion and extension in 60 sub-acute and chronic stroke patients with motor impairments (hemiparesis and/or spasticity) of the right arm. The study protocol is a randomized controlled trial consisting of a 4-week functional rehabilitation program, with both clinical and robotically instrumented assessments to be conducted at baseline and post-treatment. The primary outcome measures will be a set of standard clinical scales for upper limb spasticity and motor function assessment, including the Modified Ashworth Scale and Fugl-Meyer Index, to confirm the safety and evaluate the efficacy of robotic rehabilitation in reducing elbow stiffness and improving function. Secondary outcomes will include biomechanical, muscular activity, and motor performance parameters extracted from instrumented assessments using the NEEM along with synchronous EMG recordings. The study protocol has been registered on clinicaltrials.gov with registration trial number NCT04484571. Conclusions: This randomized controlled trial aims to validate an innovative instrumented methodology for clinical spasticity assessment and functional rehabilitation, relying on the precision and accuracy of an elbow exoskeleton combined with EMG recordings and the expertise of a physiotherapist, thus complementing and maximizing the benefits of both practices

Contrasting styles of (U)HP rock exhumation along the Cenozoic Adria-Europe plate boundary (Western Alps, Calabria, Corsica)

Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary

Tectono-metamorphic evolution of the external continental units of Alpine Corsica" (Northern Corsica, France)

The Alpine belt in Corsica is characterised by the occurrence of a continental units stack (External Continental Units), located along the boundary between two main geological domains, referred as Hercynian (to the west) and Alpine Corsica (to the east) respectively. This units stack represent a slice of the Corsican/European continental margin, involved in the Alpine orogeny. The investigated area is located in Northern Corsica, from Lozari and Ostriconi to Ponte Leccia, Francardo and Castiglione. The External Continental Units (ECU) consist of slices of a Palaeozoic continental crust mainly formed by Permo-Carboniferous granitoids, associated to a Late Carboniferous to middle Eocene meta-sedimentary cover. From the deformational point of view, these units record a polyphase deformation history of Alpine age, characterised by superimposed foliations and fold structures, well developed inside the meta-sedimentary cover. The basement rocks are characterized by a heterogeneous deformation with development of shear zones, where granites show a cataclastic-mylonitic deformation, wrapping around undeformed granitoids. In the ECU the three main deformation phases (D1, D2 & D3) can be regarded as ranging in age from Late Eocene (the age of the Bocca Capanna Flysch involved in the D1 deformation phase) to Early Miocene (the age of the oldest deposits found in the Francardo–Ponte Leccia Basin). The occurrence of Alpine polyphase deformation suggests that all the ECU extending between the Upper Units (Bas-Ostriconi Unit, Balagne Nappe and Pineto-Tribbio Unit), the Francardo–Ponte Leccia Basin and the “autochthonous” domain were involved in the Alpine Orogeny. Moreover, the occurrence of peak metamorphism characterised by epidote-blueschist mineral assemblages indicates that Alpine HP/LT metamorphism also affected these continental slices derived from the Corsica/Europe continental margin (previously regarded as weakly metamorphosed or non-metamorphosed, with the exception of Popolasca-Castiglione Unit), with estimated P–T conditions of T=280–380 °C and P=0.50–0.90 GPa for the granitoid rocks of the Popolasca-Castiglione (PCU) and Croce d’Arbitro (CAU) units, T=270-400 °C and P=0.70-1.25 GPa for the Fuata-Pedanu Unit (FPU) and P>0.40 GPa for the Palasca-Moltifao (PMU) and Piedigriggio-Prato (PPU) units. Therefore, this study provide new quantitative data about the peak metamorphism in the Corsican Alpine belt. Also the eastern margin of the “autochthonous” domain (referred to as Belgodere-Asco Unit) is affected by Alpine deformation and metamorphism, as testified by the development of localised cataclastic-mylonitic shear zones in the granitoids (observed in the area between the Asco and Golo valleys) and by the occurrence of peak metamorphism characterised by P-T conditions close to the greenschist / blueschist facies transition, with pressures between 0.55 and 0.70 GPa and temperatures lower than 450 °C. On the base of structural features and metamorphic conditions the D1 phase recognised in the ECU can be interpreted as related to the deformations achieved during their underplating at different depth into the accretionary wedge (as testified by development of HP/LT metamorphic mineral assemblages), while the D2 and D3 phases can be related to the exhumation history. Particularly the D2 phase was associated to the first stage of exhumation driven by a syn-contractional westward thrusting onto the eastern margin of the Hercynian basement and the D3 phase can be interpreted as related to the last stage of exhumation history during the Oligo-Miocene extensional tectonics. As a whole, a continuous belt of continental slices characterised by HP/LT metamorphism of Tertiary age can be identified from the Tenda Massif (NE of studied area) to the Corte area (S of studied area). This picture supports the hypothesis that large portions of the Corsican/European continental margin were deformed under HP/LT metamorphic conditions during their involvement in the tectonics connected with Alpine subduction and were subsequently juxtaposed against the metamorphic and non-metamorphic oceanic units during a complex exhumation history

Stratigraphic and structural features of the Bas-Ostriconi Unit (Corsica): paleogeographic implications

The palaeogeographic origin of the Bas Ostriconi Unit (Balagne area, Alpine Corsica) has long been a matter of debate. This unit is actually detached from its original basement. It is made of Late Cretaceous carbonatic turbidites with lenses of coarse-grained polymict conglomerates (Narbinco Flysch). The turbidites have a mixed siliciclastic-carbonatic composition and are affected by a polyphasic deformation. Here, based on field observations and sampling, we analyse the sedimentary, petrographic, and structural features of the Narbinco Flysch. From these analyses, we derive that the Narbinco Flysch belongs to the sedimentary cover of the Balagne ophiolite Nappe. We also show that the carbonatic turbidites are associated with mixed siliciclastic-carbonatic coarse-grained debris, which is typical of the turbidite sediments deposited during the Late Cretaceous in the Ligure-Piemontese oceanic basin close to the European Margin. Our results thus suggest that, the Bas Ostriconi Unit originally formed on the Ligure-Piemontese oceanic crust, then was integrated to the accretionary wedge that was thrusted on the European margin of Corsica during the Eocene collisional events

Pre-collisional architecture of the European distal margin: Inferences from the high-pressure continental units of central Corsica (France)

The Lower Units of Alpine Corsica, France, are fragments of continental crust strongly deformed and metamorphosed under high-pressure metamorphic conditions. Three slices of Lower Units are well exposed in the area between the Asco and Tavignano valleys, Central Corsica. Despite their complex structural setting, they provide the opportunity for a reconstruction of the pristine stratigraphic setting of the Lower Units. In our reconstruction, these units consist of a Paleozoic basement topped by Triassic to Early Jurassic sedimentary rocks unconformably covered by Middle to Late Eocene foredeep deposits. However, the three units exposed in the study area display strong differences mainly in the thickness of the Mesozoic sequence. These differences are here interpreted as acquired during the first stage of the rifting process in a setting controlled by normal faults. During the collision-related tectonics and the accretion of the Lower Units to the Alpine orogenic wedge, these normal faults were probably reactivated with a reverse kinematics. The stratigraphic logs of the Lower Units strictly resemble those of the Pre-Piedmont Units from Western Alps. This similarity indicates a common origin of the Lower Units and the Pre-Piedmont Units from the same domain (i.e., the European distal continental margin)

Alpine tectono-metamorphic history of the continental units from Vardar Zone: the Kopaonik Metamorphic Complex (Dinaric-Hellenic belt, Serbia)

The easternmost zone of the Dinaric-Hellenic belt is represented by the Vardar Zone, in which the Kopaonik Metamorphic Complex is regarded as the lowermost unit. This complex is topped by the unmetamorphosed Brzece unit and is intruded by the Oligocene Kopaonik Intrusive Complex. The Kopaonik Metamorphic Complex is characterized by a stratigraphy that includes metapelites and meta-carbonates of Late Triassic age, associated with metabasites. It is characterized by a complex deformation history that comprises four phases: D1 to D4. The D1 phase structures occur only as relict structures, whereas the D2 phase structures are represented by isoclinal F2 folds, associated with a well developed S2 foliation. The estimated P-T conditions for the D1 and D2 metamorphism are consistent with the upper greenschist facies. The D3 phase is characterized by west-verging thrusts associated with upright folds. In contrast, the D4 phase is characterized by open folds (F4) associated with low-angle normal faults. The D1 and D2 deformation phases developed during the shortening related to continental collision, whereas the subsequent D3 and D4 phases can be related to the progressive exhumation of the Kopaonik Metamorphic Complex. The D4 phase probably developed during extensional tectonics during and after emplacement of the Kopaonik Intrusive Complex. The data show that the continental units belonging to the Vardar Zone had a long-lived deformation history that was more complex that previously thought