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Consequently, the U-Pb dates obtained on apatite can be interpreted as the emplacement ages for these mafic intrusions.
Our results demonstrate that, in all cases, the apatite grains do carry enough radiogenic Pb to be dated by in situ U-Pb analyses and yield a Pb-corrected mean age of 363.4 ± 5.8 Ma.
Their emplacement ages were so far poorly constrained due to the difficulty to date these mafic rocks using either the Ar or the U-Pb methods on classical minerals like mica, plagioclase, or zircon.
These results reveal the existence of a major and short-lived magmatic event in the Variscan belt of Brittany during the Devonian-Carboniferous transition, a feature further highlighted by field evidence.
Beyond the geological implications of these results, U-Pb LA-ICP-MS dating of apatite appears to represent an ideal tool to date small size mafic intrusions.
Over the course of 14 machine runs and 160 spot analyses the 2 sigma concordia age uncertainty is 0.6% (Figure 2a).
The variable U concentrations and hence µ ( Figure 2: (a) Self-normalized MMap reference apatite data from 160 spots over 14 separate machine runs showing excellent concordia age precision of 1.2% (2 sigma).