Isotopic dating of older elements (including the Cabo Ortegal mafic-ultramafic complex) in the Hercynian orogen of NW Spain: Manifestations of a presumed Early Paleozoic mantle-plume

Calsteren, P. W. C. van; Boelrijk, N.A.I.M.; Hebeda, E. H.; Priem, H.N.A.; Tex, E. den; Verdurmen, E.A.Th.; Verschure, R. H.

doi:10.1016/0009-2541(79)90011-1

Cited by 96 publications

(36 citation statements)

References 7 publications

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“…Upper intercept ages of 1.95-2.5 Ga have been found in orthogneisses of the Ordenes and Morais Complexes (Kuijper 1979;, whereas granulite-and amphibolite-facies rocks sampled in units derived from mafic protoliths have yielded upper intercept ages of 2.6-2.8 Ga (peucat et al 1990;Santos Zalduegui et al 1996). Widespread Cambro-Ordovician magmatism at 520-500 Ma has been documented in the upper units of the allochthonous complexes (Kuijper 1979;Van Calsteren et al 1979;Peucat et al 1990;Schafer et al 1993;Abati et al 1999;Ord6fiez Casado et al 2001;Femindez-Suarez et al 2002, 2004Santos et al 2002). In the Ordenes Complex, both arc-type magmatism and a related the=al event have been recognized and dated at c. 500-495 Ma (Abati et al 1999(Abati et al , 2003.…”

Section: Pre-520mamentioning

confidence: 99%

⁴⁰ Ar/ ³⁹ Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia

Barreiro

Wijbrans

Castiñeiras

et al. 2006

JGS

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The tectonothennal evolution of a polyorogenic terrane in the Variscan belt of NW Spain has been constrained by 40 Ar/ 3 9 Ar laserprobe incremental heating experiments on mylonitic f � brics developed in major structures. Transitional levels between HP-HT and IP upper lUlits in the Ordenes Complex where metamorphic and structural records demonstrate two cycles of burial and exhlUllation were selected for dating. Two groups of ages have been defined: (1) Silurian-Early Devonian, obtained from mylonites of the Fomas extensional detachment, here considered as the minimlUll age for the start of tectonic exhlUllation of the HP HT lUlits and an upper age-limit for the HP-HT event itself; (2) Early to Mid-Devonian, from structures related to the Variscan convergence in the area, which include top-to-the-east thrusts and extensional detachments. A single, YOlUlger Carboniferous age obtained from the uppennost allochthonous sequences possibly reflects the final stages of emplacement of the allochthonous complexes. Our data indicate a polyorogenic character for a part of the Iberian allochthonous complexes, including Variscan (sensu stricto)and Early Variscan convergence, as well as an older, Early Palaeozoic cycle.

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Section: Pre-520mamentioning

confidence: 99%

⁴⁰ Ar/ ³⁹ Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia

Barreiro

Wijbrans

Castiñeiras

et al. 2006

JGS

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“…10B), represented by the basal units, where the end of the HP metamorphic event has been dated at 374 Ma (average Rb-Sr ages obtained in posteclogitic phengites by Van Calsteren et al 1979). The available isotopic data point to synchronism between the unroofing of the HP basal units and the development of extensional detachments in the upper part of the nappe pile.…”

Section: Tectonic Evolution Of the Careó N Unitmentioning

confidence: 99%

“…Classically, and in contrast to Alpine-type orogens, the Variscan belt was considered to be almost devoid of remnants of oceanic crust. This has led some authors to put forward strike-slip or "ensialic" models involving mantle plume processes (Van Calsteren et al 1979). More recently, oceanic relicts have been identified (Arenas et al 1986;Arenas 1988), and paleomagnetic data now support the geological evidence of wide Paleozoic oceans (Bon- Manuscript received September 29, 1998;accepted June 1, 1999. 1 Departamento de Petrología y Geoquímica, Universidad Complutense, 28040 Madrid, Spain.…”

Section: Introductionmentioning

confidence: 99%

Tectonic Evolution of the Careón Ophiolite (Northwest Spain): A Remnant of Oceanic Lithosphere in the Variscan Belt

García¹,

Arenas²,

Catalán³

et al. 1999

The Journal of Geology

102

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A B S T R A C TAnalysis of the Careó n Unit in the Ordenes Complex (northwest Iberian Massif) has supplied relevant data concerning the existence of a Paleozoic oceanic lithosphere, probably related to the Rheic realm, and the early subduction-related events that were obscured along much of the Variscan belt by subsequent collision tectonics. The ophiolite consists of serpentinized harzburgite and dunite in the lower section and a crustal section made up of coarse-grained and pegmatitic gabbros. An Early Devonian zircon age ( Ma, U-Pb) was obtained in a leucocratic gabbro. The 395 ‫ע‬ 2 whole section was intruded by numerous diabasic gabbro dikes. Convergence processes took place shortly afterward, giving rise to a mantle-rooted synthetic thrust system, with some coeval igneous activity. Garnet amphibolite, developed in metamorphic soles, was found discontinuously attached to the thrust fault. The soles graded downward to epidote-amphibolite facies metabasite and were partially retrogressed to greenschist facies conditions. Thermobarometric estimations carried out at a metamorphic sole ( ЊC; kbar) suggested that imbrications T ≈ 650 P ≈ 11.5 developed in a subduction setting, and regional geology places this subduction in the context of an early Variscan accretionary wedge. Subduction and imbrication of oceanic lithosphere was followed by underthrusting of the Gondwana continental margin.

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“…They also suggest contemporaneity with the ongoing convergence. The end of the HP metamorphic event of the basal units has been dated at 374 Ma (average Rb-Sr ages obtained in post-eclogitic phengites by Van Calsteren et al 1979). This and other Rb-Sr ages ranging from 365 to 352B3 Ma (Santos Zalduegui et al 1995) reflect the progressive exhumation of the subducted outer margin of Gondwana (Fig.…”

Section: Discussionmentioning

confidence: 99%

Structural and kinematic analysis of the Corredoiras detachment: evidence for early Variscan synconvergent extension in the Ordenes Complex, NW Spain

García¹,

Catalán

Arenas

et al. 1999

International Journal of Earth Sciences

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An important detachment is described in the allochthonous Ordenes Complex, in the NW Iberian Massif, and its meaning is related to the kinematics of contemporaneous convergent structures. The Corredoiras Detachment (CD) separates a hangingwall unit, characterised by a medium-pressure metamorphic gradient, from a footwall high-pressure and hightemperature unit and an underlying ophiolitic unit. An associated ductile shear zone, nearly 2000 m thick, developed in the lower part of the hangingwall unit, where the Corredoiras Orthogneiss, a Lower Ordovician metagranite, was progressively transformed into augengneisses, mylonitic and ultramylonitic gneisses. The attitude of the stretching and mineral lineation in the mylonites varies due to late refolding at map scale, but the sense of movement can be estimated, being roughly top to the SE. According to crosscutting relationships, the CD developed subsequent to the thrusting of the high-pressure/high-temperature unit onto the ophiolitic unit, and prior to younger extensional detachments, upright folding and strike-slip tectonics. The geometric relationships of the CD with the previous structures in the footwall unit, the subtractive character of the metamorphic gap between its hangingwall and footwall, and the available isotopic data suggest that the CD is an early Variscan, ductile extensional detachment, the movement of which was roughly simultaneous with the onset of thrusting of the allochthonous complexes over their relative autochthon.

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Isotopic dating of older elements (including the Cabo Ortegal mafic-ultramafic complex) in the Hercynian orogen of NW Spain: Manifestations of a presumed Early Paleozoic mantle-plume

Cited by 96 publications

References 7 publications

⁴⁰ Ar/ ³⁹ Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia

⁴⁰ Ar/ ³⁹ Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia

Tectonic Evolution of the Careón Ophiolite (Northwest Spain): A Remnant of Oceanic Lithosphere in the Variscan Belt

Structural and kinematic analysis of the Corredoiras detachment: evidence for early Variscan synconvergent extension in the Ordenes Complex, NW Spain

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Isotopic dating of older elements (including the Cabo Ortegal mafic-ultramafic complex) in the Hercynian orogen of NW Spain: Manifestations of a presumed Early Paleozoic mantle-plume

Cited by 96 publications

References 7 publications

40 Ar/ 39 Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia

40 Ar/ 39 Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia

Tectonic Evolution of the Careón Ophiolite (Northwest Spain): A Remnant of Oceanic Lithosphere in the Variscan Belt

Structural and kinematic analysis of the Corredoiras detachment: evidence for early Variscan synconvergent extension in the Ordenes Complex, NW Spain

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⁴⁰ Ar/ ³⁹ Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia

⁴⁰ Ar/ ³⁹ Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia