Dom Feliciano Belt and Punta del Este terrane: geochronological features

Paleoproterozoic basement (2.3 to 2.0 Ga) affected by Neoproterozoic metamorphic processes and granitic intrusions in an interval from 0.8 to 0.6 Ga. Several Shrimp U/Pb data from southern Brazil (Porcher et al., 1999) indicate ages from 783 to 766 Ma for the acid volcanism related to the Porongos Complex. In Uruguay (Fig.1), the Lavalleja Group represents the southern portion of the Metamorphic Belt, which is characterized by a supracrustal sequence metamorphosed under low to medium grade conditions. Only few data are available for the metavolcanic rocks (around 680 to 690 Ma K/Ar (WR); Umpierre, 1974 in Sánchez, 1998). The southern basement of this volcano-sedimentary sequence is represented by the Punta Rasa basement with U/Pb ages on granitic-gneissic mylonites of 2.1 Ga and TDM of 2320 Ma. The presence of granitoids, directly related to the metamorphites of the Lavalleja Group, has been recognized