SHRIMP U-PB DATA OF THE PALEOPROTEROZOIC, REGIÃO DOS LAGOS COMPLEX, RIO DE JANEIRO, BRAZIL: IMPLICATIONS TO RIBEIRA BELT EVOLUTION

Abstract

The studied region is located in the Rio de Janeiro State (SE, Brazil) and is part of the Ribeira Belt, in the central portion of the Mantiqueira Province. The rocks of this region were included in the Brasiliano/Pan-African orogeny, from Neoproterozoic to the early Paleozoic. The basement is comprised of Paleoproterozoic rocks, sedimentary and volcano-sedimentary rocks from Mesoproterozoic and Neoproterozoic and intrusive granitic rocks from the Neoproterozoic. These rocks are interpreted as associations of magmatic arcs, sedimentary sequences of passive margins and tardi-kinematic granites, respectively. The study area is located in Cabo Frio Terrane, where the basement is represented by the Região dos Lagos Complex.The Região dos Lagos Complex can be divided into: granitic rocks (biotite-orthoclase-plagioclase gneiss), tonalitic rocks (biotite-microcline-plagioclase gneiss). The main aims of the SHRIMP U-Pb zircon studies of the Região dos Lagos Complex is to identify the crystallization ages of this complex and to define the magmatic events in the Ribeira Belt. The obtained U-Pb ages are: sample CRL-04, 1960 ± 19 Ma; sample CRL-05, 1986 ± 24 Ma; sample CRL-06, 1985 ± 34 Ma; sample CRL-07, 1942 ± 16 Ma; sample CRL-08, 1970 ± 17 Ma and; sample CRL-09, 1989 ± 22 Ma.These results suggest that the Região dos Lagos complex has crystallization from 1989 Ma to 1942 Ma, and was formed during an important magmatic event related to the Ribeira Belt formed previously to the Gondwana amalgamation probably related to Congo craton basement.