[en] Rb-Sr systematics have been applied on rocks from the Sao Felix do Xingu region, in the southeastern part of the State of Para. An age of 2716 ± 34 Ma with IR of 0.70292 ± 0.00030 (MSWD = 1.54) and an age of 2677 ± 50 Ma with IR of 0.70161 ± 0.00022 (MSWD = 5.21) had been obtained for a granitic body and a tonalitic body respectively, both of them associated to the green stones belts that occur in this area. Gneisses from the Xingu complex gave an age of 2574 ± 57 Ma with an IR of 0.70416 ± 0.00054 (MSWD = 5.06). An age of 1653 ± 14 Ma with IR of 0.70823 ± 0.02361 (MSWD = 1.71) had been obtained for the Velho Guilherme granite that crosscut the granite-green stones terrains. Such geochronological data show the existence of a magmatic event between 2.72 Ga and 2.68 Ga and permit us to conclude on the archaean age of the green stones terrains. (author)