Structural evolution of the southernmost segment of the West European Variscides: the South Portuguese Zone (SW Iberia)

Onézime, Jérôme; Charvet, Jacques; Faure, Michel; Chauvet, Alain; Panis, Dominique

doi:10.1016/s0191-8141(01)00079-7

Cited by 32 publications

(23 citation statements)

References 19 publications

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“…The major structural feature of the IPB consists of a south-verging thrust-fold belt complex that caused significant crustal thickening and stacking. This structural configuration, compatible with a thin-skinned geometry, was developed in the course of two main deformation phases, presumably on top of a major cryptic décollement correlated with the lower-upper Devonian transition within the Phyllite-Quartzite Formation [29,31,[58][59][60][61][62]. Data gathered so far support the conclusion that the structural evolution experienced by the IPB is controlled by the OMZ-SPZ oblique collision.…”

Section: Geodynamic Framework Of the Sw Iberian Variscides: Setting Osupporting

confidence: 64%

“…In fact, the contact of the Pulo do Lobo Terrane with the SPZ northern border is characterized by dextral (to reverse-dextral) shearing structures (from Paymogo to Campofrio areas), which seem to be related to the late syntectonic emplacement of the Gil Márquez granodiorite dated 328±2 Ma [30, 32, 33 - Table 1]. According to Onézime et al [31], this dextral (to reverse-dextral) shearing typifies the last deformation episode recorded in both the Pulo do Lobo Terrane and the SPZ northern border, and may be related to dextral transtension associated with the emplacement of late-stage pulses of the (tonaliticgranitic) Sierra Norte Batholith.…”

Section: Geodynamic Framework Of the Sw Iberian Variscides: Setting Omentioning

confidence: 96%

“…Metamorphic conditions are typically of lower greenschist facies, although rocks belonging to the uppermost Formation reveal very low grade metamorphism [28]. The PLT displays strong multiphase deformation that can be ascribed to three main Variscan deformation phases with folding/axial plane cleavage development, plus important thrust systems with prevailing southwards shear sense [15,24,[29][30][31]. It should be noted, however, that structures formed in the northern sectors of the Terrane are consistent with a dominant sinistral strike-slip tectonic regime while those developed in the southern sectors reflect a chief dextral strike-slip tectonic regimes.…”

Section: Geodynamic Framework Of the Sw Iberian Variscides: Setting Omentioning

confidence: 99%

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The Beja Layered Gabbroic Sequence (Ossa-Morena Zone, Southern Portugal): geochronology and geodynamic implications

et al. 2007

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The Beja Igneous Complex (BIC) is a major geological feature in SW Iberian Variscides, consisting of three main units developed during different stages of the oblique collision between the Ossa Morena Zone (OMZ) upper plate and South Portuguese Zone (SPZ) lower plate, namely: (1) ca. 355 Ma to ca. 345 Ma Layered Gabbroic Sequence formed in early stages of collision magmatism; (2) the ca. 335-330 Ma to ca. 320 Ma Cuba-Alvito (gabbro-diorite) Complex formed throughout the late-collision magmatic event; and (3) the Baleizão Porphyry Complex corresponding to the period of post-collision magmatism, ca. 300 Ma. The new SHRIMP U-Pb age of 342±9 Ma reported here for amphibole-bearing pegmatite dykes cutting the layered gabbros is interpreted as dating the development of late fluid-rich melts in the Layered Gabbroic Sequence, synchronous with Fe-Cu-Co sulphide deposition. The close agreement between this data and available amphibole 40 Ar/ 39 Ar ages of BIC, Beja-Acebuches Ophiolite and other geological units of the OMZ southern border, may be taken as evidence for a moderate to rapid regional crustal uplift episode at ca. 340±5 Ma; this data, coupled with structural constraints, also allow to estimate the age for the transition between the D 2a -D 2b deformation phases of Variscan continental collision. A complex wedge system within the SW Iberian Variscides developed during this collision, involving the OMZ upper plate to the north and the SPZ passive margin in the lower plate. The Évora-Beja-Aracena Domain, located in the upper plate above the N-dipping subduction zone, is re-interpreted as a retro-wedge domain that was kinematically coupled to the SPZ pro-wedge and subduction system. Retro-wedge growth is linked to upper plate uplift (early collision) and a late-orogenic wedge thickening. The early stages of magmatism in the retro-wedge are related to asthenospheric mantle upwelling induced by the slab break-off. Regional LP-HT metamorphism and subsequent magmatic events in the retro-wedge domain were caused by long term high heat flow sustained by (1) mafic magma underplating, (2) stacking of high-heat producing upper-crustal lithologies, and reinforced (3) by (moderate to) rapid crustal uplifting. Mass advection and orogenic architecture were strongly affected by asymmetric removal towards the lower-part foreland basin and by transient mechanical properties of the wedge system associated with the anomalous thermal regime.

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Section: Geodynamic Framework Of the Sw Iberian Variscides: Setting Osupporting

confidence: 64%

Section: Geodynamic Framework Of the Sw Iberian Variscides: Setting Omentioning

confidence: 96%

Section: Geodynamic Framework Of the Sw Iberian Variscides: Setting Omentioning

confidence: 99%

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The Beja Layered Gabbroic Sequence (Ossa-Morena Zone, Southern Portugal): geochronology and geodynamic implications

et al. 2007

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“…The whole succession of the IPB suffered slight regional metamorphism during the Hercynian Orogeny (Munhá 1979(Munhá , 1990Abad et al 2001). Deformation in the IPB has been extensively discussed and a thin-skinned tectonic model is widely accepted that describes the IPB as a southward-verging thrust and fold belt (Schermerhorn and Stanton 1969;Schermerhorn 1971;Ribeiro and Silva 1983;Silva et al 1990;Soriano 1996;Quesada 1998;Onézime et al 2002).…”

Section: Geological Setting Of the Iberian Pyrite Beltmentioning

confidence: 99%

A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

et al. 2011

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International audienceIn the Rio Tinto district of the Iberian Pryrite Belt of South Spain, the weathering of massive sulfide bodies form iron caps, i.e., true gossans and their subsequent alteration and re-sedimentation has resulted in iron terraces, i.e., displaced gossans. To study the stucture and evolution of both types of gossans, magnetic investigations have been carried out with two foci: (1) the characterisation and spatial distribution of magnetic fabrics in different mineralised settings, including massive sulfides, gossans, and terraces, and (2) paleomagnetic dating. Hematite has been identified as the suceptibility carrier in all sites and magnetic fabric investigation of four gossans reveals a vertical variation from top to bottom, with: (1) a horizontal foliation refered to as "mature" fabric in the uppermost part of the primary gossans, (2) highly inclined or vertical foliation interpreted as "immature" fabric between the uppermost and lowermost parts, and (3) a vertical foliation interpreted to be inherited from Hercynian deformation in the lowermost part of the profiles. In terraces, a horizontal foliation dominates and is interpreted to be a "sedimentary" fabric. Rock magnetic studies of gossan samples have identified goethite as the magnetic remanence carrier for the low-temperature component, showing either a single direction close to the present Earth field (PEF) direction or random directions. Maghemite, hematite, and occasionally magnetite are the remanence carriers for the stable high-temperature component that is characterized by non PEF directions with both normal and reversed magnetic polarities. No reliable conclusion can be yet be drawn on the timing of terrace magnetization due to the small number of samples. In gossans, the polarity is reversed in the upper part and normal in the lower part. This vertical distribution with a negative reversal test suggests remanence formation during two distinct periods. Remanence in the upper parts of the gossans is older than in the lower parts, indicating that the alteration proceeded from top to bottom of the profiles. In the upper part, the older age and the horizontal "mature" fabric is interpreted to be a high maturation stage of massive sulfides' alteration. In the lower part, the age is younger and the inherited "imature" vertical Hercynian fabric indicates a weak maturation stage. These two distinct periods may reflect changes of paleoclimate, erosion, and/or tectonic motion

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“…The first strike‐slip stage affected the upper structural levels of the Pulo do Lobo terrane and gave place to a penetrative mylonitic foliation which is parallel to both OD‐S 2 and the axial planes of intrafolial folds defined by highly deformed quartz ribbons [ Díaz Azpiroz , 2001]. Fold axes orientation, fold asymmetries, S‐C' structures, mica‐fish structures, rotated σ‐type plagioclase porphyroclasts and helicoidal garnet porphyroblasts point to an apparent left‐lateral sense of movement [see also Onézime et al , 2002] and are, in consequence, compatible with the kinematics of the Southern Iberian shear zone. These observations suggest that the Southern Iberian shear zone (OD‐D 2 ) affected the upper structural levels of the Pulo do Lobo terrane [see also Crespo‐Blanc and Orozco , 1988; Crespo‐Blanc , 1992; Onézime et al , 2003].…”

Section: Oceanic Domainmentioning

confidence: 99%

Tectonometamorphic evolution of the Aracena metamorphic belt (SW Spain) resulting from ridge‐trench interaction during Variscan plate convergence

et al. 2006

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[1] The Aracena metamorphic belt is a hightemperature/low-pressure (HT/LP) band located at the southern end of the European Variscan chain. It marks a suture between Armorica and Avalonia. This belt is characterized by (1) the presence of mid-ocean ridge basalt-derived metabasites that were affected by an inverted HT/LP metamorphism related to SW verging thrusting, whose thermal peak diachronously migrated eastward; (2) the occurrence of a HT/LP metamorphism, related to an extensional event, affecting continental rocks belonging to the Ossa Morena zone with peak temperatures that are $150°C higher than that recorded in the oceanic metabasites; and (3) the presence of near-trench magmatism with high-Mg andesite composition. These and other characteristics can be interpreted in terms of a ridgetrench-trench triple junction that migrated along the Armorican margin during Variscan oblique convergence. Citation: Díaz Azpiroz, M., C. Fernández, A. Castro, and M. El-Biad (2006), Tectonometamorphic evolution of the Aracena metamorphic belt (SW Spain) resulting from ridgetrench interaction during Variscan plate convergence, Tectonics, 25, TC1001,

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Structural evolution of the southernmost segment of the West European Variscides: the South Portuguese Zone (SW Iberia)

Cited by 32 publications

References 19 publications

The Beja Layered Gabbroic Sequence (Ossa-Morena Zone, Southern Portugal): geochronology and geodynamic implications

The Beja Layered Gabbroic Sequence (Ossa-Morena Zone, Southern Portugal): geochronology and geodynamic implications

A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

Tectonometamorphic evolution of the Aracena metamorphic belt (SW Spain) resulting from ridge‐trench interaction during Variscan plate convergence

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