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-Upper 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 "plagiogranite'' from the intrusive sequence was dated by U-Pb zircon geochronology. Although affected by some uncertainty, mainly reflecting common Pb contamination, the U-Pb zircon data suggest a crystallization age of 159 +/- 3 Ma (MSWD = 6.3), which is coeval with the formation of oceanic lower crust in the Schistes Lustre ' s 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-Pb zircon geochronology carried out on two distinct levels of quartzo-feldspathic clastic sediments identified the predominance of zircons with within error U-Pb dates at similar to 280 Ma; minor components at similar to 457, similar to 309 and similar to 262 Ma were also obtained. The U-Pb date distribution is consistent with a source magmatic material mostly developed during the Variscan orogenic collapse.