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less than 150 μm in size, with poorly marked oscillatory or sector zoning (soccer ball zoning) and showing no evi- dence of rim overgrowth or inherited xenocrystic cores; some show possible re-absorption (Figure 9a). Ten zircon crystals were analysed, of which eight crystals provided concordant U-Pb analyses (concordance values between 100% and 110%) and coherent isotopic ratios. These grains provided a Concordia age of 594 ± 2.9 Ma (Figure 10a) and a weighted average of 206 Pb/ 238 U ages for the same con- sistent group of 8 zircons of 596 ± 2.9 Ma (Figure 10b). This age is considered to be the most probable time of crystal- lization of the analysed metagabbro protolith. 5.2.2. Metatonalite OM-1. The metatonalite sample provided abundant zircon crys- tals of up to 200 μm in size. They are idiomorphic or subidiomorphic prismatic crystals, with well-developed concentric oscillatory zoning or soccer-ball zoning, black rims (in CL) and no evidence of inherited xenocrystic cores (Figure 9b). Other grains are too dark to reveal zoning, but in BSE images, some appear to be full of inclusions with random zoning. Forty-eight crystals were analysed, of which 39 provided concordant U-Pb ages (concordance values between 90% and 110%) and con- sistent isotopic ratios. Their projection on a conventional Figure 8. ɛ Nd vs. age diagrams showing TDM values for the mafic and felsic rocks (a and b, respectively) from the Mérida Ophiolite. The range of Nd model ages of the mafic and felsic rocks that occur in the Montemolín Formation of the Mérida Massif (Rojo-Pérez et al . 2022) is shown for comparison. INTERNATIONAL GEOLOGY REVIEW 15 Mérida Ophiolite (SW Iberia)