Timing of Cadomian deformation and magmatism within La Hague, NW France
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The La Hague peninsula, Normandy, NW France, contains the most northerly components of the Late Neoproterozoic Cadomian orogeny. U-Pb dates for single-grain and small multiple-grain zircon separates from carefully selected plutons provide geochronological constraints on the timing of deformation and magmatism within the region. The syntectonic Jardeheu quartz diorite and Omonville granodiorite were emplaced and contemporaneously deformed during the development of a greenschist-facies fabric, pervasive across the peninsula. U-Pb zircon dates of 610 1 Ma for the Jardeheu quartz diorite and 608 2 Ma for the Omonville granodiorite are similar to a previously reported sensitive high-resolution ion microprobe U-Pb date for metamorphism of the basement, and indicate that a regionally significant period of metamorphism and magmatism occurred between 620 and 608 Ma. An emplacement age of 573.9 +1.3/-0.9 Ma for the syntectonic Thibot granodiorite places limits on the timing of deformation along the Thibot Shear Zone. Zircons from the undeformed St Martin monzonite give a precise U-Pb age of 581.3 1.1 Ma. The new dates point to reactivation of magmatism and localized greenschist-facies deformation between 582 and 573 Ma.
