Supplementary Material

Fig. S1. Summary of U-Pb ages (2σ) obtained on zircon control materials during the different LA-ICP-MS analytical sessions using the Agilent 8900 (green) and Nu Instruments AttoM ES (red) systems at GeoRessources. The zircon primary reference material was changed from 91500 (Wiedenbeck et al., 1995) in 2023 (a–b) to RAK-17 (Webb et al., 2020) in 2024 (c–d). The recommended age of Temora-2 (Black et al., 2004), RAK-17, Peng-16 (G-Chron3) and 91500 are shown in blue, while calculated mean U-Pb ages are shown in grey. The excess variance in U-Pb ages determined across all analytical sessions ranges from 0.6% for 91500 (d) to 1.5% for Temora-2 (a).

Fig. S2. Interpretative cross section of the Beauvoir rare-metal granite of the Echassières complex (Cuney et al., 1992; Rocher et al., 2024) showing location of analyzed samples.

Fig. S3. Supplementary photographs of samples from the Sioule region investigated during this study. (a-b) Metasedimentary rock samples collected for detrital zircon U-Pb geochronology within the paragneiss unit: (a) Quartzite interlayered with migmatitic paragneiss; (b) biotite-sillimanite paragneiss. (c-d) Cambrian metatexitic monzogranitic gneiss and diatexitic leucogranitic gneiss. (e) Fine-grained leucogranite from the Saint-Gervais Massif deformed along the Sainte-Christine shear zone. (f) Trachy-dacitic tuff from the Manzat Formation. (g) Trachy-dacitic tuff from the Châteauneuf Formation. (h) Microphotograph of a cordierite crystal almost entirely replaced by white and black micas in the devitrified matrix of a rhyolitic dyke from the Echassières Complex.

Fig. S4. Total alkaki versus silica diagram for (a) (meta-) plutonic rocks (Wilson, 1989) and (b) volcanic rocks (Le Bas et al., 1986) from the Sioule region. Abbreviations: Fm. - Formation.

Fig. S5. Representative cathodoluminescence images of zircon grains from Sioule (meta)igneous rocks. Locations of LA–ICP–MS analytical spots are shown, along with their corresponding analysis numbers and associated 206Pb/238U dates (or 207Pb/206Pb dates for purple analyses). Date uncertainties are reported at the 2σ level.

Fig. S6. Representative cathodoluminescence images of apatite grains from the Colettes granites and Beauvoir microgranite enclave that were analyzed for their U-Pb isotopic compositions.

Fig. S7. U–Pb compositions of detrital zircon grains from metasedimentary rocks of the mica schist (a) and paragneiss (b–c) units of the Sioule Series. Inset diagrams show either 206Pb/238U date distributions (a–b) or a zoomed-in Tera-Wasserburg plot (c) highlighting the youngest detrital zircon dates and corresponding maximum depositional ages. Diagram (1) in panel (c) displays a close-up of the main Paleoproterozoic zircon population identified in sample ECH23-101, along with calculated intercept dates in a Wetherill concordia plot. Ellipses, error bars, and dates are reported at 2σ. Empty ellipses correspond to analyses with a degree of concordance < 90% and were excluded from the histogram and KDE diagrams in Fig. 8.

Fig. S8. Topographic profiles across the transition between the volcanic-sedimentary rocks of the Châteauneuf and Manzat Formations, constructed using Google Earth and 1:50,000 BRGM geological maps (Hottin et al., 1989). The profiles consistently show the Châteauneuf Formation overlying the Manzat Formation, supporting the interpretation of an older age for the latter.

Supplementary Table 1. Metadata for LA-ICP-MS U–Pb isotopic (and trace element) analyses..

Supplementary Table 2. U–Pb LA-ICP-MS data for apatite, cassiterite, and wolframite control reference materials. Analyses shown in grey were not taken into account in age calculations.

Supplementary Table 3. U–Pb LA-ICP-MS data for apatite, cassiterite, and wolframite samples. Analyses shown in grey were not taken into account in age calculations.

Supplementary Table 4. U–Pb (and trace elements) LA-ICP-MS data for zircon (and glass) control reference materials. Analyses shown in grey were not taken into account in age calculations. LOD = limit of detection.

Supplementary Table 5. Synthesis of U–Pb ages calculated from zircon control reference materials (uncertainties quoted without long-term uncertainty propagation). The data point in grey was rejected from the excess variance calculation.

Supplementary Table 6. U–Pb (and trace elements) LA-ICP-MS data for zircon (and glass) samples. Analyses shown in grey were not taken into account in age calculations.

Supplementary Table 7. Summary of U–Pb geochronological data obtained in this study.

Supplementary Table 8. Whole-rock geochemical data and GPS coordinates of samples from this study. bdl = below detection limit.

Supplementary Table 9. Whole-rock geochemical data compiled from the literature.

Supplementary Table 10. Compilation of ages for Sn and W magmatic-hydrothermal mineralizing events, as well as peraluminous RMG and RMP emplacement, across the west-European Variscan belt including the French Massif central, and the Armorican and Iberian massifs.

© C. Ballouard et al., Published by EDP Sciences 2026