In the portion east of the Cinturão Araguaia in the State of the Tocantins some graníticos bodies of small dimensions are identified, deserving have detached granites Santa Luzia, Ramal do Lontra and Presidente Kennedy, which are the register of an important event of granitogênese related to the evolution of the Cinturão Araguaia in the end of the Neoproterozóic. The Granite Ramal do Lontra, located in the northwest of the State of the Tocantins, approximately the 30 km the Southeast of the city of Xambioá, constitutes a stock of lightly oval form with longer axe of approximately 5 km and smaller axe of 4 km, hosted by quartzitos and micaxistos of the Estrondo Group . The Granite Ramal do Lontra, accord petrographics studies are represented by metagranites with small mineralogical variations, poor in mafics minerals (< 6%), hololeucocratic, equigranular middle, presenting granoblastic texture, predominantly, with texture to reliquiar granular hipidiomorphic. In diagram QAP of Strackeisen, its classification is placed dominant in the field of the monzogranite, or in the limit of the fields monzogranite the granodiorite. The classification most specific detaches muscovite-biotite meta-monzogranites and muscovite-biotite meta-monzogranites the granodiorites. Its mineralogic content is formed essentially by peristeritic plagioclase (An11-16), quartz and microcline, beyond biotite and muscovite. The accessory minerals congregate apatite, zircon, titanite, alanite, monazite, oxide of rare earth element and minerals opacs. The geochemicals data show great composicional homogeneity presenting high values of SiO2, Al2O3, K2O and Na2O, and low values of MgO, Fe2O3Total and TiO2. The diagrams of the geochemistry classification and normative data with the presence of normative coríndon, indicate leucogranitic nature and peraluminous character for the Granite Ramal do Lontra. The study of element-trace showed that it has compositions variations in the rocks of the Granite Ramal do Lontra, what was not evidenced in the elements biggest, where observed a homogeneity in content of such elements. Such study it disclosed to a group of rocks with signature geochemistry distinct of the majority of the rocks of the Granite Ramal do Lontra, possessing high contents of REE, beyond element-trace Nb, Ta and Y, that is reflected petrographicly by the biggest amount of monazite and a rare earth oxide in these rocks. The high content of these elements is possibly related to the contamination of the magma for its hosted rocks during its ascension. The geocronologic study carried through by the method of evaporation of Pb in zircon supplied average age of 549±5 Ma, which is interpreted as the minimum age of crystallization of the zircon and, consequently, of the Granite Ramal do Lontra. This age is similar to gotten in the Granite Santa Luzia enter 550-560 Ma the one that is correlated the same the magmatic event of the Cinturão Araguaia. Combining geologic, petrographics, geochemicals and geocronologics the data of the Granite Ramal do Lontra it is concluded to deal with one granitogênese peraluminous of lodging sin-tectonic to the evolution of the Cinturão Araguaia. This granitogenese also cronologicaly is related to granites of the Suíte Lageado of age 546±6 Ma, situated the Southeast of the Cinturão Araguaia whose bodies are incased in granulítics and gnaissics lands of the paleoproterozoic of the Massif of Goiás, but with geologic, petrographics and geochemicals characteristics different. These varied granitics bodies can be related to a thermal event of great amplitude related to the regional metamorphism in the neoproterozoic of the Cinturão Araguaia, that also affected its basement. Two hypotheses are adopted as possible sources for the Granite Ramal do Lontra. One of them would be for fusing of ortognaisses of the Complex Colméia, and to another one it would involve fusing of the metassediments of the Cinturão Araguaia (Estrondo Group), however not them of pelitic composition, but of composition the quartz-feldspatic.
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