Zircon U-€“Pb geochronology of lower crust and quartzo-feldspathic clastic sediments from the Balagne ophiolite (Corsica)

The Balagne ophiolite from central-northern Corsica represents a continent-near paleogeographic domain of the Jurassic Liguria-Piedmont ophiolitic basin. Pillow and massive basalt lavas are primarily associated with Middle\u2013Upper Jurassic pelagic sediments (mostly radiolarites at their base), continental-derived quartzo-feldspathic clastic sediments and ophiolitic breccias containing clasts of gabbros and basalts. The basalt-sedimentary succession is tectonically associated with a slice composed of an intrusive sequence overlain by basalt lavas. A \u201cplagiogranite\u201d from the intrusive sequence was dated by U\u2013Pb zircon geochronology. Although affected by some uncertainty, mainly reflecting common Pb contamination, the U\u2013Pb zircon data suggest a crystallization age of 159 \ub1 3 Ma (MSWD = 6.3), which is coeval with the formation of oceanic lower crust in the Schistes Lustr\ue9s units from Alpine Corsica. The predominance of quartz grains preserving typical volcanic shape, the prevalence of prismatic zircons and the arkose whole-rock composition indicate that the continental-derived quartzo-feldspathic clastic sediments have a low degree of textural maturity. U\u2013Pb zircon geochronology carried out on two distinct levels of quartzo-feldspathic clastic sediments identified the predominance of zircons with within error U\u2013Pb dates at ~280 Ma; minor components at ~457, ~309 and ~262 Ma were also obtained. The U\u2013Pb date distribution is consistent with a source magmatic material mostly developed during the Variscan orogenic collapse