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Isotope geochemistry and revised geochronology of the Purrido Ophiolite (Cabo Ortegal Complex, NW Iberian Massif): Devonian magmatism with mixed sources and involved Mesoproterozoic basement

Sánchez Martínez, Sonia and Arenas Martín, Ricardo and Gerdex, Axel and Castiñeiras García, Pedro and Potrel, Alain and Fernández Suárez, Javier (2011) Isotope geochemistry and revised geochronology of the Purrido Ophiolite (Cabo Ortegal Complex, NW Iberian Massif): Devonian magmatism with mixed sources and involved Mesoproterozoic basement. Journal of the Geological Society, 168 . pp. 733-750. ISSN 0016-7649

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Abstract

In the Purrido Ophiolite (Cabo Ortegal Complex), new U–Pb zircon dating of the amphibolite
G03-8 (by laser ablation inductively coupled plasma mass spectrometry) confirms the existence of a dominant
Mesoproterozoic zircon population with a refined age of 1155 14 Ma. However, the U–Pb zircon dating of
two more amphibolite samples (by sensitive high-resolution ion microprobe) has provided new ages of
395 3 Ma and 395 2 Ma, respectively, interpreted as the crystallization age. Hf isotope data for zircon
show that most of the Devonian zircons crystallized from a juvenile depleted mantle source. The
Mesoproterozoic zircons have relatively juvenile Hf isotopic composition reflecting some influence of an older
component. A few Devonian zircon crystals show evidence of mixing with an older component represented by
the Mesoproterozoic zircons. The whole-rock Sm–Nd isotope data indicate an important heterogeneity in the
composition of the Purrido amphibolites, only compatible with the generation of their protoliths from two
sources. We interpret these puzzling data as resulting from the mixing of a Devonian mantle-derived magma
with a Mesoproterozoic basement. These new data provide new perspectives in the interpretation of the most
common ophiolites across the Variscan suture in Europe.


Item Type:Article
Uncontrolled Keywords:Devonian magmatism; Isotope geochemistry; NW Iberian massif
Subjects:Sciences > Geology > Petrology
ID Code:14034
Deposited On:07 Dec 2011 12:49
Last Modified:07 Dec 2011 12:49

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