Comparative use of TIMS and SHRIMP for U–Pb zircon dating of A-type granites and mafic tholeiitic layered complexes and dykes from the Corsican Batholith (France)

The Corsica-Sardinia batholith in the southern realm of the Hercynian belt of Europe shows evidence for gravitational collapse of this part of the mountain belt, causing major felsic and mafic magmatism. The latest intrusions are composed of leucomonzogranite and late metaluminous and alkaline granite, associated with tholeiitic layered complexes and dykes. Three dating methods on zircon (Pb-evaporation, ID-TIMS and SHRIMP) were used to unravel the chronology of these felsic and mafic rocks. Dating of zircons by the conventional U–Pb method, using TIMS after zircon dissolution, achieved an analytical uncertainty of 1 Ma for favourable cases. The TIMS Pb-evaporation technique resulted in ages with an uncertainty range of 4 to 8 Ma. After 15 to 20 analyses with the SHRIMP method, a precision ranging from 2 to 5 Ma was obtained (all at 2σ). The three methods applied to the same zircon population extracted from four A-type granites, show that the uncertainty ranges within 2–5 Ma according to the sample. This error seems to correspond to the real geochronological uncertainty that can be achieved.