basement-rocks, capped by Mesozoic sedimentary sequences related to an ancient passive continental margin. In thePeloritani Mountains, the basement nappes form an Africa-verging thrust belt, now located at the trailing edge of theLate Oligocene to Early Miocene Maghrebian accretionary wedge of Sicily. The innermost basement nappes of thePeloritani Mountains, including their Mesozoic sedimentary covers, show a locally preserved mylonitic overprint ofalpine age, suggesting their exhumation from deep-seated crustal levels, during the mountain building. Fieldinvestigations integrated by petrographic structural analyses, evidenced that the Paleogene edifice, overthrusting as awhole the Late Cretaceous-Eocene accretionary wedge terranes of the Mt. Soro Unit along the Taormina Line, actuallyconsists of three superimposed tectonic nappes. They are represented from the top, by the high grade Aspromonte Unit(AU), the low to medium grade Upper Metapelitic Unit (UMU) and the very low- to low grade Lower Metapelitic Unit(LMU). These three tectonic units are separated by two main shear zones, the Aspromonte Shear Zone (ASZ) and theUpper Metapelitic Shear Zone (UMSZ) respectively, involving highly sheared remnants of distinct Mesozoic toTertiary passive margin successions. Upper Eocene to Upper Oligocene clastic sequences, unconformably covering theMt. Soro Unit and the LMU, are involved in the footwall of the Taormina Line and of the UMSZ. Upper Chattian toLower Miocene deposits conceal the Taormina Line, the UMSZ and the ASZ.The structural and petrographic analyses evidenced that the two upper tectonic units are affected by an alpinemetamorphic overprint. It consists of an earlier sub-greenschist to greenschist mineral assemblages developed duringisoclinal folding, which also affected the Mesozoic sedimentary sequences along the AUSZ. This event was followedby ductile shearing that produced a mylonitic band along the AUSZ. Lithons of Mesozoic terranes deformed in ductilebrittleconditions are involved along the UMSZ which shows evidences of brittle shearing. The more external LMU andthe Mt. Soro Unit are unaffected by any alpine metamorphic overprint, as well as the intervening Taormina Line whichdeveloped in a brittle condition. The collected data well constrain a Paleogene alpine metamorphic event which wasassociated to the emplacement of the inner nappes of the Peloritani Mountain Belt (AU and UMU), which representedan alpine deep-crustal root that overthrust portions of the Variscan basement unaffected by the alpine metamorphism.The overall alpine evolution of the Peloritani Mountains implies a collision event that pre-dates the propagation of theSicilide accretionary wedge terrains and the Middle Miocene collision onto the African margin. This evidence suggestthe occurrence of a continental crustal domains, different from the african domains, now involved in the outer portion ofthe arc, at the footwall of the Paleogene collision zone.
|Titolo:||Paleogene collision tectonics in the Peloritani Mountains: geological and petrographical constraints|
|Data di pubblicazione:||2015|
|Appare nelle tipologie:||1.5 Abstract in rivista|