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Thickening and exhumation of the Variscan roots in the Iberian Central System: Tectonothermal processes and 40Ar/39Ar ages

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Rubio Pascual, Francisco J. and Arenas Martín, Ricardo and Martínez Catalán, José Ramón and Rodríguez Fernández, Luis Roberto and Wijbrans, Jan R. (2013) Thickening and exhumation of the Variscan roots in the Iberian Central System: Tectonothermal processes and 40Ar/39Ar ages. Tectonophysics, 587 . pp. 207-221. ISSN 0040-1951

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Official URL: http://www.journals.elsevier.com/tectonophysics/



Abstract

40Ar/39Ar dating of white mica inmetapelites, thermobarometric calculations and new structural and geological
mapping have been carried out in the Somosierra region (Iberian Central System, ICS) to investigate the Variscan
thickening–exhumation processes and the evolution of the paleo-thermal structure in a key region of the Central
Iberian Zone. The rocks underwent an intermediate P/T event (M1) during a D1 stage of crustal thickening initiated
between 354 and 347 Ma. This eventwas probably related to a first S to SE-directed emplacement of theNW
Iberian allochthon, and during the initial development of amid-crustal subhorizontal shear zone accommodating
the ductile flow of thermally weakened crust parallel to the main orogenic trend. Syn-convergent extension of
the upper levels occurred by 335–327 Ma, when tectonic unroofing led to D2 domal uplift of the orogenic
roots and to recrystallization of rocks under intermediate to low P/T conditions (M2). Individualized gneiss
domes developed along the orogenic trend, whereas some post-M2 thrusts dated at c. 319 Ma reflect lateral
flow related to limited gravitational spreading of the domes. Younger upright to SW verging folding of the ICS
dome during D3 progressive renewal of contractive deformation took place after 316 Ma. Final D4 gravitational
collapse occurred under low P/T conditions (M3) at c. 300 Ma, accompanied by the intrusion of large volumes of
anatectic granitoids.


Item Type:Article
Uncontrolled Keywords:Variscan metamorphism, Barrovian to low-P evolution, 40Ar/39Ar geochronology, Iberian Massif
Subjects:Sciences > Geology > Petrology
ID Code:26601
Deposited On:03 Sep 2014 09:14
Last Modified:01 Jan 2015 00:01

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