J. J. Peucat, Y. Hirbec, B. Auvray, J. Cogné, J. Cornichet; Late Proterozoic zircon ages from a basic-ultrabasic complex: A possible Cadomian orogenic complex in the Hercynian belt of western Europe. Geology ; 9 (4): 169–173. doi: https://doi.org/10.1130/0091-7613(1981)9<169:LPZAFA>2.0.CO;2
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The basic-ultrabasic complex of Belle-IsIe-en-Terre (northwestern part of the Armorican Massif, France) has been dated at 602+4−1 m.y. by the U-Pb zircon method. The calc-alkaline trend of the metabasic rocks and the geologic context suggest that this ophiolite-like complex is related to a back-arc orogenic setting similar to the geodynamic environment that has been proposed for Pan-African calc-alkaline ophiolite-like complexes of late Proterozoic age around the West African craton. Our results are compatible with the closing, in late Proterozoic time, of a “Channel ocean” north of the basement and formed during the Cadomian orogeny, rather than with possible Caledonian or Hercynian subduction.