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The last stages of the Avalonian–Cadomian arc in NW Iberian Massif: isotopic and igneous record for a long-lived peri-Gondwanan magmatic arc

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Andonaegui Moreno, Pilar and Arenas Martín, Ricardo and Albert Roper, Richard and Sánchez Martínez, Sonia and Díez Fernández, Rubén and Gerdes, Axel (2016) The last stages of the Avalonian–Cadomian arc in NW Iberian Massif: isotopic and igneous record for a long-lived peri-Gondwanan magmatic arc. Tectonophysics, 681 . pp. 6-14. ISSN Issn: 0040-1951 ; Essn: 1879-3266

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Official URL: https://www.sciencedirect.com/journal/tectonophysics/vol/681/suppl/C




Abstract

The upper allochthonous units of NW Iberian Massif contain an extensive Cambrian magmatism (c. 500 Ma), covering felsic to mafic compositions. The magmatic activity generated large massifs of granitoids and gabbros, with calc-alkaline and tholeiitic compositions respectively. Petrological and geochemical features of these massifs are characteristic of volcanic arc. The plutons intruded siliciclastic sedimentary series deposited in the periphery of the West Africa Craton. U–Pb/Hf isotopic compositions of detrital zircon in the siliciclastic host series, indicate continental arc activity between c. 750 Ma and c. 500 Ma. It was characterized by a large variety of isotopic sources, including from very old continental input, even Archean, to the addition of a significant amount of juvenile mafic material. These isotopic sources experienced an extensive mixing that explains the composition and isotopic features (εHft from −50 until +15) of the represented Cambrian plutons. The Cambrian igneous rocks of the upper units of NW Iberia are related to the latest activity of the Avalonian–Cadomian arc. From the Middle Cambrian arc activity in the periphery of Gondwana was replaced by pronounced extension associated with the development of continental rifting, which finally led to separation of the microcontinent Avalonia. Subsequent drifting of Avalonia to the North caused progressive opening one of the main Paleozoic ocean, the Rheic Ocean.


Item Type:Article
Uncontrolled Keywords:Cambrian magmatism, Avalonian-Cadomian arc, Whole rock geochemistry, U-Pb/Hf zircon signatures, NW Iberian Massif, Variscan orogen
Subjects:Sciences > Geology > Petrology
ID Code:55474
Deposited On:29 May 2019 06:48
Last Modified:29 May 2019 06:48

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