In the Serre massif (Calabria - Southern Italy) a circa 8 km thick portion of the varisic lower crust, constituted of migmatitic paragneisses and acid and basic granulites is exposed. The principal metamorphic overprint in the lower crust is due to the variscan orogeny and has been established to have been at granulitic facies p-T conditions . Zircon dating fixed the metamorphic peak at about 300 Ma (e.g. Schenk, 1984; Micheletti et al., 2008), when a huge amount of granitoids has been emplaced in the intermediate crust. Later, this deep crustal portion has locally been involved in the alpine/appenninc orogeny. During this orogeny, several tectonic nappes of different geologic provenience, have been imbricated during thrusts tectonics. The principal tectonic thrust is called the Curinga-Girifalco Line (CGL) and separates the hercynian crust section from other low-grade alpine nappes (Schenk, 1981). Close to this tectonic line, near the village of Amaroni (CZ), another shear zone, called the Amaroni Line, crops out. On the basis of quartz CPO analyses, it has been possible to determine that the Amaroni Line has worked in conditions of high temperature. Therefore, the Amaroni Line can be considered antecedent and not related to the Curinga-Girifalco one (bachelor thesis Carluccio (2013), Inama (2013)). The rock sample studied in this thesis comes from the lower crusalt migmatitic paragneisses and has been deformed in the Amaroni shear zone. The sample contains an equilibrium mineral assemblage of garnet, quartz, k-feldspar, sillimanite and biotite. Being known that the deformation has taken place at the conditions of the granulite facies, we proceeded with the analysis of the garnet microstructures in order to provide evidence for ductile garnet deformation. The analysis has been made via the Scanning Electron Microscope, using the EBSD and Orientation Contrast techniques. The result of the analysis point out that the garnet surely undergoes ductile deformation, but only marginally and limited to little portions. Therefore, we can establish that garnet deformation occurred in the brittle-ductile transition field for the garnet.

"Il comportamento del granato nel complesso granulitico delle Serre: Brittle-ductile transitions = The behaviour of garnet in the Serre granulitic complex: Brittle-ductile transitions."

Papa, Simone
2013/2014

Abstract

In the Serre massif (Calabria - Southern Italy) a circa 8 km thick portion of the varisic lower crust, constituted of migmatitic paragneisses and acid and basic granulites is exposed. The principal metamorphic overprint in the lower crust is due to the variscan orogeny and has been established to have been at granulitic facies p-T conditions . Zircon dating fixed the metamorphic peak at about 300 Ma (e.g. Schenk, 1984; Micheletti et al., 2008), when a huge amount of granitoids has been emplaced in the intermediate crust. Later, this deep crustal portion has locally been involved in the alpine/appenninc orogeny. During this orogeny, several tectonic nappes of different geologic provenience, have been imbricated during thrusts tectonics. The principal tectonic thrust is called the Curinga-Girifalco Line (CGL) and separates the hercynian crust section from other low-grade alpine nappes (Schenk, 1981). Close to this tectonic line, near the village of Amaroni (CZ), another shear zone, called the Amaroni Line, crops out. On the basis of quartz CPO analyses, it has been possible to determine that the Amaroni Line has worked in conditions of high temperature. Therefore, the Amaroni Line can be considered antecedent and not related to the Curinga-Girifalco one (bachelor thesis Carluccio (2013), Inama (2013)). The rock sample studied in this thesis comes from the lower crusalt migmatitic paragneisses and has been deformed in the Amaroni shear zone. The sample contains an equilibrium mineral assemblage of garnet, quartz, k-feldspar, sillimanite and biotite. Being known that the deformation has taken place at the conditions of the granulite facies, we proceeded with the analysis of the garnet microstructures in order to provide evidence for ductile garnet deformation. The analysis has been made via the Scanning Electron Microscope, using the EBSD and Orientation Contrast techniques. The result of the analysis point out that the garnet surely undergoes ductile deformation, but only marginally and limited to little portions. Therefore, we can establish that garnet deformation occurred in the brittle-ductile transition field for the garnet.
2013-12-13
Garnet, dislocation creep, EBSD, brittlr-ductile transitions
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12608/17787