HP-LT metamorphism in Elba Island: Implications for the geodynamic evolution of the inner Northern Apennines (Italy)

Bianco, Caterina; Brogi, Andrea; Caggianelli, Alfredo; Giorgetti, Giovanna; Liotta, Domenico; Meccheri, Marco

doi:10.1016/j.jog.2015.08.001

Cited by 48 publications

(65 citation statements)

References 43 publications

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“…The hanging wall is composed of lithologically heterogeneous and variably deformed Cretaceous and Paleogene Flysch and the oceanic‐derived Ligurian Unit tectonically juxtaposed against the Triassic‐Oligocene Tuscan Nappe and the Carboniferous‐Triassic Rio Marina Formation of continental affinity. Imbrication during the Early Miocene is considered responsible for nappe stack formation by thrusting and folding (e.g., Massa et al, , and references therein) and juxtaposition of greenschist‐ to blueschist‐facies tectonic units within the exposed tectonostratigraphy (Bianco et al, ).…”

Section: Geological Setting and Sample Materialssupporting

confidence: 59%

New Constraints on the Evolution of the Inner Northern Apennines by K‐Ar Dating of Late Miocene‐Early Pliocene Compression on the Island of Elba, Italy

et al. 2018

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The Northern Apennines (NA) orogenic wedge formed during Oligocene‐Miocene convergence and westward subduction of Adria beneath the European Plate. Extension ensued in the Mid‐Late Miocene in response to Adria roll‐back, causing opening of the back‐arc Northern Tyrrhenian Sea. Whether extension continues uninterrupted since the Mid‐Late Miocene or it was punctuated by short‐lived compressional events, remains, however, uncertain. We used the K‐Ar method to date a set of brittle‐ductile and brittle deformation zones from the Island of Elba to contribute to this debate. We dated the low‐angle Zuccale Fault (ZF), the Capo Norsi‐Monte Arco Thrust (CN‐MAT), and the Calanchiole Shear Zone (CSZ). The CN‐MAT and CSZ are moderately west dipping, top‐to‐the‐east thrusts in the immediate footwall of the ZF. The CSZ slipped 6.14 ± 0.64 Ma (<0.1 μm fraction) and the CN‐MAT 4.90 ± 0.27 Ma ago (<0.4 μm fraction). The ZF, although cutting the two other faults, yielded an older age of 7.58 ± 0.11 Ma (<0.1 μm fraction). The ZF gouge, however, contains an illitic detrital contaminant from the Paleozoic age flysch deformed in its hanging wall and the age thus is a maximum faulting age. Removal of ~1% of a 300‐Ma‐old contaminant brings the ZF faulting age to <4.90 Ma. Our results provide the first direct dating of brittle deformation in the Apennines, constraining Late Miocene‐Early Pliocene regional compression. They call for a refinement of current NA geodynamic models in the framework of the Northern Tyrrhenian Sea extension.

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Section: Geological Setting and Sample Materialssupporting

confidence: 59%

New Constraints on the Evolution of the Inner Northern Apennines by K‐Ar Dating of Late Miocene‐Early Pliocene Compression on the Island of Elba, Italy

et al. 2018

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“…More recently, on the basis of the geochemical signature of metabasite lenses, Bianco et al . () suggest a correlation with the sedimentary sequence of Tuscan domain. However, the lithological association of this unit (marble, cherty marble and grey pelites) differs from that documented in the Palombini Shales Fm.…”

Section: Lithostratigraphy Of the Eastern Elba Nappe Stackmentioning

confidence: 60%

“…Recently, Bianco et al . () reported the occurrence of metabasite lenses hosted within marbles and pelites affected by HP/LT low‐grade metamorphism. The Ortano Porphyroid and the Ortano Marble are attributed to the Tuscan domain (Pertusati et al ., ) with the former deriving from the Palaeozoic basement (Middle Ordovician volcanic arc; Musumeci et al ., ) and the latter representing a Lower Mesozoic carbonatic platform sequence (Barberi et al ., ).…”

Section: Lithostratigraphy Of the Eastern Elba Nappe Stackmentioning

confidence: 99%

“…epizone) in the Lower Complex (as testified by relics of albite + muscovite + chloorite mineral assemblages in the Calamita Unit; Garfagnoli et al, 2005). Recent finding of glaucophane-bearing metabasite lenses in the Ortano Unit not overprinted by contact metamorphism indicates that some portions of metamorphic units experienced early Miocene highpressure metamorphism (Bianco et al, 2015). E-verging thrusts separating the Lower Complex and Upper Complex as well as thrust sheets documented within the Upper Complex trend N-S/NNE-SSW.…”

Section: Geological Outline Of the Elba Island Nappe Stackmentioning

confidence: 99%

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Coexistence of contractional and extensional tectonics during the northern Apennines orogeny: the late Miocene out‐of‐sequence thrust in the Elba Island nappe stack

et al. 2016

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In the northern Tyrrhenian Sea, the Elba Island is one of the westernmost portions of the northern Apennine inner belt. One of its noteworthy features is the anomalous tectonic repetition of continental‐derived (Tuscan Unit) and oceanic‐derived (Ligurian units) thrust sheets, lately intruded by late Miocene granitoids. Moreover, in detail, a slice of strongly deformed Ligurian peridotites results tectonically sandwiched between two thrust sheets of Tuscan units. This tectonic setting results from a middle Miocene folding and thrusting of the Apenninic nappe stack with development of large‐scale antiform and out‐of‐sequence thrust. In central‐eastern Elba Island, the folding of an imbricate stack is bracketed between Langhian (middle Miocene) and Messinian (late Miocene). Consequently, the anomalous repetition of Tuscan and Ligurian units thrust sheets gives evidence of middle‐late Miocene shortening deformation post‐dating nappe stack and pre‐dating late Miocene–Pliocene granite emplacement. We suggest that the architecture of the Elba Island nappe stack documents the coexistence of early‐middle Miocene contractional and extensional tectonics in an overall convergent tectonic setting in the westernmost zone of northern Apennines. Extensional tectonics in the upper portion of the wedge, balancing transient gravitational instabilities due to over‐thickened conditions, were followed by a renewal of contractional deformation leading to development of large‐scale out‐of‐sequence thrust responsible for inversion of the stack order. Copyright © 2016 John Wiley & Sons, Ltd.

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“…The nappe pile is characterized by east verging structures stacked over west dipping top-to-the-E thrust sheets during the early Miocene (Keller & Coward, 1996;Massa et al, 2017). Blueschist facies metamorphism related to early Miocene underthrusting and nappe stacking is locally preserved in the Ortano Unit (Bianco et al, 2015). Blueschist facies metamorphism related to early Miocene underthrusting and nappe stacking is locally preserved in the Ortano Unit (Bianco et al, 2015).…”

Section: Geological Outlinementioning

confidence: 99%

Fluid‐Assisted Strain Localization in Quartz at the Brittle/Ductile Transition

Papeschi

Musumeci

2019

Geochem Geophys Geosyst

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A mylonitic quartzite with conjugate and synthetic shear bands was investigated by Electron Backscatter Diffraction and optical microscopy to obtain insights on recrystallization mechanisms and strain localization in quartz at plastic to semibrittle conditions close to the brittle‐ductile transition. The mylonitic quartzite deformed during late Miocene thrusting coeval with contact metamorphism in the high‐strain domains of the Calamita Schists (Elba Island, Italy). Mylonitic deformation occurred from amphibolite to lower greenschist facies conditions during cooling of the aureole. Dynamic recrystallization, dominated by the activity of dislocation creep by prism slip, produced recrystallized quartz layers mantling relic large quartz porphyroclasts. Under decreasing temperature and fluid‐rich conditions, quartz porphyroclasts acted as relatively rigid bodies and fractured along synthetic and conjugate C′ shear bands. Shear bands developed along kinematically favored orientations, just locally assisted by weak crystallographic planes in quartz. Fracturing along shear bands was assisted by cataclasis and fluid infiltration enhancing fracture propagation and healing by recrystallization and authigenesis of new quartz and phyllosilicate grains. The process enhanced the propagation of and strain localization in shear bands, with the development of bands of weak phyllosilicates. Furthermore, we observed the development of a c axis preferred orientation (CPO) related to dissolution and precipitation of new grains with their c axis oriented parallel to shear bands. This study highlights the importance of the interplay between brittle and crystal‐plastic processes and fluid ingress in the semibrittle regime to understand deformation partitioning and strain localization.

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HP-LT metamorphism in Elba Island: Implications for the geodynamic evolution of the inner Northern Apennines (Italy)

Cited by 48 publications

References 43 publications

New Constraints on the Evolution of the Inner Northern Apennines by K‐Ar Dating of Late Miocene‐Early Pliocene Compression on the Island of Elba, Italy

New Constraints on the Evolution of the Inner Northern Apennines by K‐Ar Dating of Late Miocene‐Early Pliocene Compression on the Island of Elba, Italy

Coexistence of contractional and extensional tectonics during the northern Apennines orogeny: the late Miocene out‐of‐sequence thrust in the Elba Island nappe stack

Fluid‐Assisted Strain Localization in Quartz at the Brittle/Ductile Transition

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