Zircon Hf signatures from granitic orthogneisses of the Spanish Central System: Significance and sources of the Cambro-Ordovician magmatism in the Iberian Variscan Belt

Villaseca, Carlos; Martínez, Enrique Merino; García, David Orejana; Andersen, Tom; Белоусова, Е. А.

doi:10.1016/j.gr.2016.03.004

Cited by 51 publications

(39 citation statements)

References 114 publications

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“…These data sit along an average crustal evolution trend together with those from the 550 Ma-old zircons, corresponding to Hf model ages comprised between 1.0 and 1.5 Ga, in agreement with Hf and Nd isotope data from the FMC granitoids Pin and Duthou, 1990;Turpin et al, 1990). Such model ages clearly have no geological significance as zircon in all Gondwana derived sediments throughout Europe provide no evidence for magmatism during this period (Balintoni et al, 2014;Díez Fernández et al, 2012;Drost et al, 2011;Gebauer et al, 1989;Gerdes and Zeh, 2006;Linnemann et al, 2014;Morag et al, 2011a;Pastor-Galán et al, 2013;Pereira et al, 2012a;2012b;Shaw et al, 2014;Sirevaag et al, 2016;Villaseca et al, 2016;Williams et al, 2012;Zeh and Gerdes, 2010). Instead, this Hf isotope signature would correspond again to a mixed source consisting of Neoproterozoic (0.6-0.8 Ga), juvenile crust and Archean/Paleoproterozoic crust (2.0-3.3 Ga).…”

Section: Accepted Manuscriptsupporting

confidence: 76%

Pre-Cadomian to late-Variscan odyssey of the eastern Massif Central, France: Formation of the West European crust in a nutshell

Chelle-Michou¹

2017

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The East Massif Central (EMC), France, is part of the internal zone of the Variscan belt where late Carboniferous crustal melting and orogenic collapse have largely obliterated the pre-to early-Variscan geological record. Nevertheless, parts of this history can be reconstructed by using in-situ U-Th-Pb-Lu-Hf isotopic data of texturally well-defined zircon grains from different lithological units. All the main rock units commonly described in the EMC are present in the area of Tournon and include meta-sedimentary and meta-igneous rocks of the Upper Gneiss Unit (UGU) and of the Lower Gneiss Unit (LGU), as well as cross-cuttingVariscan granitoid dikes and a heterogeneous granite coring the major Velay dome. Herein we demonstrate that the UGU and the LGU have markedly distinct zircon records. The results of this study are consistent with deposition of the protoliths of the paragneisses within a backarc basin that was located adjacent to the Arabian-Nubian shield and/or the Saharan Metacraton during the late Ediacaran and collected detritus from the Gondwana continent. At ~545 Ma some of these sedimentary rocks were affected by a first melting event that formed the protoliths of the LGU orthogneisses, those of which subsequently remelted at ca. 308 Ma to form the Velay granite-migmatite dome. Protoliths of the UGU result mainly from a bimodal rift-related magmatism at ~480 Ma, corresponding to melting of the Ediacaran sediments and depleted mantle. Zircon rims from the UGU additionally provide evidence for a metamorphic/migmatitic overprint during the Lower Carboniferous (~350-340 Ma).Finally, several generations of granite dikes of which inherited zircons display characteristics of both the UGU and the LGU were protractedly emplaced from ~322 Ma to ~308 Ma, the youngest of which being coeval with the formation of the Velay dome. Our data further show that the vast majority of crustal material ultimately involved in the Variscan orogeny, which forms the present-day basement in the EMC, was derived from a sedimentary mixture of ACCEPTED MANUSCRIPTA C C E P T E D M A N U S C R I P T various components from the Gondwana continent deposited in Ediacaran times, with no evidence for the involvement of an older autochthonous crust.

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Section: Accepted Manuscriptsupporting

confidence: 76%

Pre-Cadomian to late-Variscan odyssey of the eastern Massif Central, France: Formation of the West European crust in a nutshell

Chelle-Michou¹

2017

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“…Neoproterozoic to Cambrian age modes are likely derived from various terranes in North Africa and Arabia related to the East African Orogeny (600–500 Ma; e.g., Kröner & Stern, ). Cambro‐Ordovician to Silurian DZ ages are likely related to Peri‐Gondwanan terranes that are characterized by ubiquitous Ordovician magmatism, including the pre‐Variscan European basement and the Peri‐Gondwanan belt of the Middle East, associated with early Paleozoic subduction along the northern margin of Gondwana as well as rifting of Avalonia (e.g., Hassanzadeh et al, ; Villaseca et al, ; von Raumer et al, ). In the Attic‐Cycladic complex, clastic sediments from Samos island are dominated by Cambrian to Neoproterozoic sources (Löwen et al, ).…”

Section: Discussionmentioning

confidence: 99%

Zircon U‐Pb Chronostratigraphy and Provenance of the Cycladic Blueschist Unit and the Nature of the Contact With the Cycladic Basement on Sikinos and Ios Islands, Greece

et al. 2019

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Sikinos and Ios Islands, located in the Southern Cyclades, represent part of a Cenozoic metamorphic core complex system that exposes subduction-related metamorphic rocks in the highly extended back-arc region of the Hellenic subduction zone. These exhumed HP-LT metamorphic units are composed of Mesozoic metasedimentary rocks of the Cycladic Blueschist Unit (CBU) and the Paleozoic Cycladic Basement (CB). The magmatic and stratigraphic evolution of these units, as well as the nature of the contact between the CBU and CB, have remained poorly understood. We used zircon U-Pb dating to determine crystallization ages of the CB on Sikinos and the maximum deposition ages and detrital provenance of the metasedimentary units to reconstruct the Mesozoic to early Cenozoic stratigraphic and tectonic evolution of the CBU on both islands. The results reveal that the CB in Sikinos is composed of Cambrian-Silurian metasedimentary rocks intruded by Carboniferous granites and is overlain by metasedimentary rocks of the CBU with depositional ages spanning from Permo-Triassic to Late Cretaceous. The provenance data from the CBU records a long-lived tectonic evolution from Paleo-Tethys subduction and rifting, to passive margin formation, and to subduction of the Neo-Tethyan Pindos basin. The continuous stratigraphic record and provenance evolution from the CB into the CBU imply a para-autochthonous relationship. On NE Sikinos and Ios, stratigraphic constraints suggest older-over-younger relationships along cryptic-thrusts, supporting premetamorphic or synmetamorphic structural repetition of the CBU by imbrication, likely during subduction underplating.

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“…CC BY 4.0 License. 2015;Díaz-Alvarado el al., 2016;Villaseca et al, 2016;García-Arias et al, 2018). The peak of magmatic activity was reached at ca.…”

Section: The Phase Of Uplift and Denudation Of An Inherited Palaeorelmentioning

confidence: 98%

“…Although a general consensus exists to associate this Furongian-Ordovician magmatism with the opening of the Rheic Ocean and the drift of Avalonia from northwestern Gondwana (Díez Montes et al, 2010;Nance et al, 2010;Thomson et al, 2010;Álvaro et al, 2014a), the origin of this magmatism has received different interpretations. In the Central Iberian Zone, for instance, proposals point to: (i) magmas formed in a subduction scenario reaching the crust in a magmatic arc to back-arc setting (Valverde-Vaquero and Dunning, 2000;Castro et al, 2009); (ii) magmas resulting from partial melting of sediments or granitoids in a continental lower crust affected by the underplating of hot mafic magmas during an extensional regime (Bea et al, 2007;Montero et al, 2009;Díez Montes et al, 2010); and (iii) magmas formed by post-collisional decompression melting of an earlier thickened continental crust, and without significant mantellic involvement (Villaseca et al, 2016). In the Occitan Domain (southern French Massif Central and Mouthoumet massifs) and the eastern Pyrenees, Marini (1988), Pouclet et al (2017) and Puddu et al (2019) have suggested a link to mantle thermal anomalies.…”

Section: Introductionmentioning

confidence: 99%

Comparative geochemical study on Furongian (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe

Álvaro¹,

Sánchez-García²,

Puddu³

et al. 2020

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Abstract. A geochemical comparison of Early Palaeozoic felsic magmatic episodes throughout the south-western European margin of Gondwana is analysed. The comparison is made between (i) Furongian–Early Ordovician (Toledanian) activies recorded in the Central Iberian and Galicia-Trás-os-Montes Zones of the Iberian Massif, and (ii) Early–Late Ordovician (Sardic) activities in the eastern Pyrenees, Occitan Domain (Albigeois, Montagne Noire and Mouthoumet massifs) and Sardinia. Both phases are related to uplift and denudation of an inherited palaeorelief, and stratigraphically preserved as distinct angular discordances and paraconformities involving gaps of up to 30 m.y. The geochemical features of the Toledanian and Sardic, felsic-dominant activies point to a predominance of byproducts derived from the melting of metasedimentary rocks, rich in SiO2 and K2O and with peraluminous character. Zr / TiO2, Zr / Nb, Nb / Y and Zr vs. Ga / Al ratios, and REE and ƐNd values suggest the contemporaneity, for both phases, of two geochemical scenarios characterized by arc and extensional features evolving to distinct extensional and rifting conditions associated with the final outpouring of mafic tholeiitic-dominant lava flows. The Toledanian and Sardic phases are linked to neither metamorphism nor penetrative deformation; on the contrary, their unconformities are associated with foliation-free open folds subsequently affected by the Variscan deformation. The geochemical and structural framework precludes a subduction scenario reaching the crust in a magmatic arc to back-arc setting, but favours partial melting of sediments and/or granitoids in a continental lower crust triggered by the underplating of hot mafic magmas during extensional events related to the opening of the Rheic Ocean.

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Zircon Hf signatures from granitic orthogneisses of the Spanish Central System: Significance and sources of the Cambro-Ordovician magmatism in the Iberian Variscan Belt

Cited by 51 publications

References 114 publications

Pre-Cadomian to late-Variscan odyssey of the eastern Massif Central, France: Formation of the West European crust in a nutshell

Pre-Cadomian to late-Variscan odyssey of the eastern Massif Central, France: Formation of the West European crust in a nutshell

Zircon U‐Pb Chronostratigraphy and Provenance of the Cycladic Blueschist Unit and the Nature of the Contact With the Cycladic Basement on Sikinos and Ios Islands, Greece

Comparative geochemical study on Furongian (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe

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