The eclogite-facies Monviso meta-ophiolite Complex (MO) in the Western Alps represents a well preserved fragment of oceanic lithosphere and related Upper Jurassic–Lower Cretaceous sedimentary covers. This metaophiolite sequence records the evolution of an oceanic core complex formed by mantle exhumation along an intra-oceanic detachment fault (the Baracun Shear Zone), related to the opening of the Ligurian-Piedmont oceanic basin (Alpine Tethys). On the basis of a detailed geological mapping, and structural, stratigraphic and petrological observations, we propose a new interpretation for the tectono-stratigraphic architecture of the MO, and discuss the role played by structural inheritance in its formation. We document that subduction- and exhumation-related Alpine tectonics were strongly influenced by the inherited Jurassic intra-oceanic tectono-sedimentary physiography. The latter, although strongly deformed during a major Alpine stage of non-cylindrical W-verging folding and faulting along exhumation-related Alpine shear zones (i.e., the Granero-Casteldelfino and Villanova-Armoine shear zones), was not completely dismembered in different tectonic units or subduction-related mélanges as suggested in previous interpretations. The present-day architecture of the MO results from nappe-scale folding with a significant component of shearing, and strain partitioning of the Alpine deformation, which were controlled by the inherited occurrence of (i) lateral and vertical variations of facies and thickness of sediments, (ii) intra-oceanic fault-rock assemblage, which acted as weak horizons in concentrating deformation, and (iii) remnants of a volcanic ridge, which consists of massive metabasalt. Thus, the recognition of pre-collisional, intra-oceanic, tectono-stratigraphic inheritance represents an important step in reconstructing the tectonic evolution of meta-ophiolite units in orogenic belts.

Role of Late Jurassic intra-oceanic structural inheritance in the Alpine tectonic evolution of the Monviso meta-ophiolite Complex (Western Alps)

BALESTRO, GIANNI;FESTA, Andrea;BORGHI, Alessandro;CASTELLI, Daniele Carlo Cesare;GATTIGLIO, Marco;TARTAROTTI, Paola
2018-01-01

Abstract

The eclogite-facies Monviso meta-ophiolite Complex (MO) in the Western Alps represents a well preserved fragment of oceanic lithosphere and related Upper Jurassic–Lower Cretaceous sedimentary covers. This metaophiolite sequence records the evolution of an oceanic core complex formed by mantle exhumation along an intra-oceanic detachment fault (the Baracun Shear Zone), related to the opening of the Ligurian-Piedmont oceanic basin (Alpine Tethys). On the basis of a detailed geological mapping, and structural, stratigraphic and petrological observations, we propose a new interpretation for the tectono-stratigraphic architecture of the MO, and discuss the role played by structural inheritance in its formation. We document that subduction- and exhumation-related Alpine tectonics were strongly influenced by the inherited Jurassic intra-oceanic tectono-sedimentary physiography. The latter, although strongly deformed during a major Alpine stage of non-cylindrical W-verging folding and faulting along exhumation-related Alpine shear zones (i.e., the Granero-Casteldelfino and Villanova-Armoine shear zones), was not completely dismembered in different tectonic units or subduction-related mélanges as suggested in previous interpretations. The present-day architecture of the MO results from nappe-scale folding with a significant component of shearing, and strain partitioning of the Alpine deformation, which were controlled by the inherited occurrence of (i) lateral and vertical variations of facies and thickness of sediments, (ii) intra-oceanic fault-rock assemblage, which acted as weak horizons in concentrating deformation, and (iii) remnants of a volcanic ridge, which consists of massive metabasalt. Thus, the recognition of pre-collisional, intra-oceanic, tectono-stratigraphic inheritance represents an important step in reconstructing the tectonic evolution of meta-ophiolite units in orogenic belts.
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http://uk.cambridge.org/journals/geo
Alpine tectonics; Jurassic Monviso ophiolite; oceanic core complex; structural inheritance; Western Alps; Geology
Balestro, Gianni; Festa, Andrea; Borghi, Alessandro; Castelli, Daniele; Gattiglio, Marco; Tartarotti, Paola
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1645864
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