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Large extensional structures developed during emplacement of a crystalline thrust sheet: the Mondoñedo nappe (NW Spain)

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Martínez Catalán, José Ramón and Arenas Martín, Ricardo and Díez Balda, M.A. (2003) Large extensional structures developed during emplacement of a crystalline thrust sheet: the Mondoñedo nappe (NW Spain). Journal of Structural Geology, 25 . pp. 1815-1839. ISSN 0191-8141

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Abstract

The Mondoñedo nappe is a crystalline thrust sheet characterized by large recumbent folds, regional intermediate-pressure metamorphism,
synkinematic intrusion of granitoids during nappe emplacement, and an extensional ductile shear zone developed within the nappe during
thrusting. A large tectonic window permits the study of the footwall unit, revealing another extensional shear zone contemporaneous with
thrusting and a low-pressure metamorphic evolution, in contrast to that of the hanging wall unit. The two main extensional shear zones
produced E–W extension parallel to the direction of orogenic shortening and normal to the orogenic structural trend. Furthermore,
subordinate N–S longitudinal extension was accommodated by normal faults in the footwall, and some of these faults were used as lateral
ramps in late stages of thrusting.
The role of the extensional shear zones and faults described is discussed in the context of an evolving orogenic wedge dominated by plate
convergence but characterized by large-scale rheological heterogeneities within it. Deep-seated viscous flow, triggered by heat accumulation,
seems to account for the horizontal stretching and probable tapering of the orogenic wedge, which was induced by gravitational instabilities
due to partial melting and underplating by buoyant continental crust.


Item Type:Article
Uncontrolled Keywords:Crystalline nappe; Syn-orogenic extension; Orogenic wedge; Iberian Massif
Subjects:Sciences > Geology > Geodynamics
ID Code:26605
Deposited On:03 Sep 2014 11:25
Last Modified:04 Sep 2014 08:20

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