1,720,986 research outputs found
The Bobbio Tectonic Window: insights in the geological structure at the northwestern edge of the Northern Apennine collisional belt.
No full textTectono-metamorphic evolution of the External Continental Units of Alpine Corsica (France): evidence for involvement of the Europe/Corsica continental margin in the Alpine subduction zone
No full textHigh-pressure external continental units (HECU) belt at the boundary between Alpine and Hercynian Corsica: a key for the understanding the Tertiary subduction and exhumation processes along the European plate margin
No full textHP/LT metamorphism in the Volparone Breccia (Northern Corsica, France): evidence for involvement of the Europe/Corsica continental margin in the Alpine subdution zone
No full textThe Alpine belt in Corsica (France) is characterized by the occurrence of stacked tectonic slices derived from the Corsica/Europe continental margin, which outcrop between two weakly or non-metamorphic tectonic domains: the “autochthonous” domain of the Hercynian basement to the west and the Balagne Nappe (ophiolitic unit belonging to the “Nappes supérieures”) to the east. These slices, including basement rocks (Permian granitoids and their Palaeozoic host rocks), Late Carboniferous–Permian volcano-sedimentary deposits, coarse-grained polymict breccias (Volparone Breccia) and Middle Eocene siliciclastic turbidite deposits, were affected by a polyphase deformation history of Alpine age, associated with a well-developed metamorphic recrystallization. This study provides new quantitative data about the peak of metamorphism and the retrograde P–T path in the Alpine Corsica: the tectonic slices of Volparone Breccia from the Balagne region (previously regarded as unmetamorphosed) were affected by peak metamorphism characterized by the phengite + chlorite + quartz ± albite assemblage. Using the chlorite-phengite local equilibria method, peak metamorphic P–T conditions coherent with the low-grade blueschist facies are estimated as 0.60 ± 0.15 GPa and 325 ± 20 C. Moreover, the retrograde P–T path, characterized by a decrease of pressure and temperature, is evidence of the first stage of the exhumation path from the peak metamorphic conditions to greenschist facies conditions (0.35 ± 0.06 GPa and 315 ± 20 °C). The occurrence of metamorphic peak at high-pressure/lowtemperature (HP/LT) conditions is evidence of the fact that these tectonic slices, derived from the Corsica/Europe continental margin, were deformed and metamorphosed in the Alpine subduction zone during their underplating at about 20 km of depth into the accretionary wedge and were subsequently juxtaposed against the metamorphic and non-metamorphic oceanic units during a complex exhumation history
The metabasites from The Kopaonik Metamorphic Complex, Vardar Zone, Southern Serbia: remnants of the rifting-related magmatism of the Mesothetyan domain or evidence for Paleotethys closure in the Dinaric-Hellenic belt?
No full textTectono-metamorphic history of the Tacagua ophiolitic unit (Cordillera de la Costa, Northern Venezuela): insights in the evolution of the southern margin of the Caribbean plate
Full text linkThe southern margin of the Caribbean Plate is well exposed in the Cordillera de la Costa of northern Venezuela, where amalgamated terranes consisting of continental and oceanic units occur. In the Cordillera de la Costa, metamorphosed oceanic units crop out along the coast near Caracas. Among them, the Tacagua unit is characterized by metaserpentinites and metabasites showing mid-oceanic ridge basalt geochemical affinity.
These lithologies, representative of a disrupted ophiolite sequence, are associated with metasediments consisting of calcschists alternating with pelitic and psammitic schists, whose protoliths were probably represented by deep-sea hemipelagic and turbiditic deposits. In the Tacagua unit, a polyphase deformation history has been reconstructed, consisting of four folding phases from D1 to D4. Geological setting suggests an involvement of the Tacagua unit in the processes connected with a subduction zone. The following deformations (from D2 to D4) observed in the field might be related to the exhumation history of the Tacagua unit. The late deformation history consists of an alternation of deformation phases characterized by displacement parallel (D2 and D4 phases) and normal (D3 phase) to plate boundary between the Caribbean and South America Plates. All lines of geological evidence suggest that the whole evolution of the Tacagua unit was acquired in a setting dominated by oblique convergence, in which alternation of strike-slip and pure compressional or pure extensional tectonics occurred through time
Tectono metamorphic history of the Golo Valley Schistes Lustres (Alpine Corsica, France): key for understanding the processes of accretion and exhumation in a fossil subduction system.
No full textTectono-metamorphic history of the ophiolitic Lento unit (northern Corsica): evidences for the complexity of accretion-exhumation processes in a fossil subduction system
No full textThe Alpine Corsica (Corsica island, France) is characterized by a stack of continent- and ocean-derived tectonic units, known as Schistes Lustrés 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 Lustrés 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 horizontal shortening, whereas the D4 phase is developed during an extensional event representing the final exhumation of the Lento unit.
On the whole, the data collected for the Lento unit suggest an history that include an accretion by coherent underplating followed by exhumation, more complex than previous described
Tectono-metamorphic history of the Duarte Terrane (Jarabacoa area, Hispaniola Isl.): Insights on the tectonic evolution of the northern rim of the Caribbean Oceanic Plateau.
No full textThe complexity of exhumation processes in a fossil subduction system provided by the tectono-metamorphic history of the oceanic Lento unit (Northern Corsica)
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