C. uerrot, J. J. Peucat, R. Capdevila, L. Dosso; Archean protoliths within Early Proterozoic granulitic crust of the west European Hercynian belt: Possible relics of the west African craton. Geology ; 17 (3): 241–244. doi: https://doi.org/10.1130/0091-7613(1989)017<0241:APWEPG>2.3.CO;2
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Granulites from the Bay of Biscay area have been studied by using U-Pb and Sm-Nd methods. Results on four granulites suggest two major events of crustal growth and high-grade metamorphism. The first is Archean (2.7 Ga), and the second is Early Proterozoic (1.9 Ga). In the Hercynian belt, the oldest basement remnants known so far are about 2.0 Ga and are located in the northern Armorican massif. The 2.7 Ga orthogneiss protolith age from the Bay of Biscay is the first direct evidence of Archean crust involved in the Hercynian belt. Major events at 2.7, 1.8, and 0.6 Ga in the Hercynian belt suggest that European Precambrian microplate(s) were part of the west African craton, where the same sequence of events is observed.