Nova Terra 52

cons and the results are shown in Supplementary Table S3.4. 95 analyses with more than 5% discordance have been discarded. A Concordia plot of the remaining concordant analyses shows a string of overlapping ellipses with corresponding ages ranging from 613 ± 19 Ma (Ediacaran) to 535 ± 18 Ma (Lower Cambrian) (Fig. 11a). Conducting a more detailed statistical study (see above), several clusters are observed at 597 ± 4 Ma (n = 22; MSWD = 0.51), 574 ± 2 Ma (n = 61; MSDW = 1.02), and a younger population at 551 ± 4 Ma (n = 14; MSWD = 4.3). The Concordia age (Fig. 11b) cor- responding to the youngest cluster is considered to represent the best estimate for the crystallization for the igneous protolith. The oldest concordant age (630 ± 27 Ma) was obtained from a single analysis. 5.2.5. Deformed metagranite of the Valverde metaigneous complex (VALMIC1 metagranite) This rock was collected near the boundary of the Valverde Metaigneous Complex and was affected by intense deformation). CL-images (Fig. 9) show a predominance of short and small prims and abundant broken zircon fragments. Zircons with a homoge- neous domain are poorly luminescent. Zircons display oscillatory or sector zoning with no evidence of metamorphic overgrowth or inherited xenocrystic cores. U-content ranges from 105 to 851 ppm and Th/U ratios range from 0.26 to 0.53. A total of 120 analyses were performed on 119 zircon grains and the results are shown in Supplementary Table S3.5. 48 of these analyses are con- cordant and 72 have a discordance > 5% or anomalous common 0.075 0.085 0.095 0.105 0.115 0.6 0.7 0.8 0.9 207 Pb/ 235 U 206 Pb/ 238 U 500 540 580 620 660 0 2 4 6 8 10 12 14 16 18 20 500 550 600 650 700 Relative probability 0.080 0.084 0.088 0.092 0.096 0.65 0.67 0.69 0.71 0.73 0.75 0.77 0.79 207 Pb/ 235 U 206 Pb/ 238 U 520 ConcordiaAge = 550.8± 4.3 Ma (2 ,decay- const. erros included) MSWD (of concordance) = 4.0, Probability(of concordance) = 0.047 560 0.084 0.086 0.088 0.090 0.092 0.094 0.67 0.69 0.71 0.73 0.75 0.77 207 Pb/ 235 U 206 Pb/ 238 U 530 570 550 (a) (b) (c) (d) VALVMIC metagranite VALVMIC metagranite 0.07 0.08 0.09 0.10 0.11 0.55 0.65 0.75 0.85 0.95 207 Pb/ 235 U 206 Pb/ 238 U 680 480 520 560 600 640 0 2 4 6 8 10 12 14 16 480 530 580 630 680 VALVMIC1 metagranite VALVMIC1 metagranite Relative probability ConcordiaAge = 553.6± 2.6 Ma (2 ,decay- const. erros included) MSWD (of concordance) = 1.07, Probability(of concordance) = 0.30 Fig. 11. Conventional Concordia diagrams showing U-Pb (LA-ICP-MS) ages of magmatic zircon from Mérida Massif metagranites: (a) granite from Valverde Metaigneous Complex (internal facies VALMIC), combined with the frequency and probability density distribution plot. (b) Concordia age obtained from the youngest zircon population in the granite from Valverde Metaigneous Complex (internal facies VALMIC), interpreted as the protolith age. (c) granite from Valverde Metaigneous Complex (external deformed facies VALMIC1), combined with the frequency and probability density distribution plot. (d) Concordia age obtained from the youngest zircon population in the granite from Valverde Metaigneous Complex (external deformed facies VALMIC1), interpreted as the protolith age. E. Rojo-Pérez, U. Linnemann, M. Hofmann et al. Gondwana Research 109 (2022) 89–112 The Ediacaran arc section