Hinterland-foreland zonation of the Variscan orogen in the Central Pyrenees: comparison with the northern part of the Iberian Variscan Massif

Abstract

A new sequence of Variscan deformations is proposed for the Palaeozoic rocks of the Central Pyrenees. The non-metamorphic units include south-directed thrust systems and related folds with a poorly developed cleavage. In the metamorphic units north-verging, recumbent to inclined folds (D1), associated with a subhorizontal to south dipping cleavage, are refolded by south-verging, upright to inclined folds (D2), with a subvertical to north-dipping axial plane cleavage, and offset by south-directed thrusts approximately coeval with D2. The structural evolution of these units suggests a subdivision of the Variscan Central Pyrenees into two different regions consistent with the zones known for a long time in the core of the Ibero-Armorican or Asturian arc (northern part of the Iberian Variscan Massif). The structure of the Pyrenean non-metamorphic units has foreland affinities and is comparable to that of the Cantabrian Zone, whereas the deformation observed in the Pyrenean metamorphic units is characteristic of the hinterland and is consistent with the features of the West Asturian–Leonese Zone or Central–Iberian Zone. Since the Pyrenean non-metamorphic units are located southwards of the metamorphic ones and the Variscan thrusts are south-directed, we tentatively correlate the Variscan Pyrenees with the northern branch of the Ibero-Armorican or Asturian arc.

Mineralogical and geochemical constraints on the shallow origin, ancient veining, and multi-stage modification of the Lherz peridotite

“…The broad correlation between 187 Os/ 188 Os isotope compositions and bulk-rock Al 2 O 3 abundances that encompasses Lherz and many other Pyrenean ultramafic massifs (sampling an area >300 km in length) exhumed in a mountain belt with a significant collisional history (c.f. McCann, 2008a,b;Garcia-Sansegundo et al, 2011), lead us toward a preferred model in which the oldest portions of the Lherz massif were created during Meso-Proterozoic melting linked to the formation of overlying crust. New mineralogical and trace-element data for Lherz peridotites ± olivine-websterite indicate that the oldest portions of this massif represent materials from mantle-wedge environments, and fluid-present spinel-facies melting may have taken place in a back-arc basin setting.…”

The significance of early Permian and early Carboniferous U–Pb zircon ages in the Bossòst and Lys‐Caillaouas granitoids (Pyrenean Axial Zone)

“…Three main foliations characterize the Variscan deformation. The first two are related to folds and thrusts developed at low‐grade conditions, whereas the third is related to shear zones developed under LP‐HT conditions (García‐Sansegundo, Poblet, Alonso, & Clariana, ). The Alpine deformation has minor effects in the Variscan structure and includes thrusts with a general top‐to‐the‐south movement, producing a local change of attitude and tightening of Variscan folds (e.g., Gutiérrez‐Medina, Alonso, & García‐Sansegundo, ; Mey, ), and the local development of foliations in the absence of metamorphism and magmatism.…”

Lateral variation in structural style of mountain building: controls of rheological and rift inheritance

“…The Variscan hinterland domain, present in the central and eastern Pyrenees, is composed of folded metamorphic units showing pervasive cleavage and is affected by numerous granitic intrusions, rendering the overall composition of the crust more felsic. Conversely, the Variscan foreland domain, present in the western Pyrenees, is characterized by a thick succession of non‐metamorphic foreland basin sediments (Sanz‐López, ; García‐Sansegundo et al ., ) and is inferred to have an overall more mafic composition. This unit is, moreover, only deformed by thrusts and thrust‐related folds and presents poorly developed cleavage.…”