The most recent geochronological studies carried out in the basement of the northern segment of the Araguaia Belt indicated the occurrence of rocks from both the Archean and the Lower Proterozoic. The oldest rocks, predominantly represented by trondhjemitic orthogneisses, with ages around 2.85 Ga, were grouped in the Colméia Complex. On the other hand, granitic orthogneisses, with a minimum age of 1.85 Ga, called Cantão Gneisse, constitute the youngest rocks, hitherto known, from the basement of the Araguaia Belt. In its southern segment, the basement of the Araguaia Belt is represented by tonalitic gneisses, associated with calciosilicate gneisses, which were correlated to the Colméia Complex, and which serve as host for the Serrote Granite, located south of the city of Paraíso do Tocantins. Calciosilicate gneisses, quartzites and tonalitic gneisses were also described, gathered in a distinct unit called Complexo Rio dos Mangues. Although the units mentioned above were considered Archean in age, there is practically no geochronological information about them. This work, therefore, aims to determine the ages of the basement rocks in the southern portion of the Araguaia Belt, and to investigate the correlation or not of these rocks with those outcroppings within the dome structures of the northern portion of this belt. This information is important for the organization of the lithostratigraphic framework of the basement of the southern portion of the Araguaia Belt, which in turn is fundamental for understanding the geological evolution of this belt. In the geochronological investigation, the method of evaporation of Pb in zircon single crystals (Pb-Pb in zircon) was used, which provides the crystallization age of zircon obtained from its gradual heating, in a thermal ionization mass spectrometer. A plateau age of the zircon grain is then calculated, on a 207Pb/206Pb versus temperature plot. Granodiorite gneisses with associated leucosomes and calciosilicate gneisses originally correlated to the Colméia Complex (samples SH12, SH15 and SH40), tonalytic gneisses and syenitic gneisses included in the Rio dos Mangues Complex (samples SH36 and SH33) and a sample of Serrote Granite. In the set of rocks that had been correlated to the Colméia Complex, the ages obtained were concentrated around 2.0 Ga, and the zircons of the leucosomes of the calcosilicate gneisses provided a relatively younger age of 1.8 Ga. In the group of rocks mapped as Complexo Rio dos Mangues, the age obtained for the zircons of the syenitic gneisses was relatively younger (1.0 Ga). These gneisses, due to their proximity to the alkaline gneisses of Serra da Estrela and because they are compositionally similar to them, should be part of the Monte Santo Suite. In the analysis of the zircons of the tonalytic gneisses, a plateau age was not defined and, on the contrary, it showed a pattern of continuous growth of the ratio , 207Pb/206Pb, and at higher temperatures, the ages systematically presented values slightly higher than 2.0 Ga . In this case, the oldest ages were assumed as minimum crystallization ages for these zircons. For the Serrote Granite, the age obtained through this method was 1851 ± 41 Ma (2σ). The ages of the gneissic rocks in the basement of the southern segment of the Araguaia Belt, located between 1.8 and 2.1 Ga, indicate the absence of gneisses of Archean ages in this portion of the belt. Consequently, it is advised against correlating them with those of the Colméia Complex. It is additionally suggested to abandon the aforementioned term and extend the name of Complexo Rio dos Mangues to the calciosilicate and orthogneisses that have expression in the vicinity of Paraíso de Tocantins. The crystallization ages of Serrote Granite (1851 ± 41 Ma, 2σ) and Cantão Gneiss (1846 ± 64 Ma) are very similar. Due to this similarity, an additional geochronological study was carried out using the Pb-Pb method in whole rock and feldspars, aiming to investigate the correlation between these granitic rocks. For the Serrote Granite, an age of 1872 ± 140 Ma (1σ) was obtained and for the Cantão Gneiss, an age of 1744 ± 27 Ma (1σ). These ages, when compared with those obtained by the Pb-Pb method in zircon, show that the Pb-Pb system in whole rock was partially opened, during a thermo-tectonic event subsequent to the crystallization of these rocks, rejuvenating their ages. A comparative study was also carried out between these units and some anorogenic granites of Proterozoic age from the Amazon region and the Median Massif of Goiás, where it was verified that the Serrote Granite is very similar to the same ones, also adjusting to the curves of evolution of Pb, proposed in the plumbotectonics model. The Cantão Gneiss does not fit the plumbotectonic model, due to the high 206Pb/204Pb ratios found in the feldspars of the samples from this unit. These high Pb ratios in these rocks reveal that they are enriched in U, and this enrichment may have come from the magma that generated them or have been acquired in a metamorphic event subsequent to its crystallization.
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