The Carmópolis de Minas Layered Suite (CMLS) is a Neoarchean Unit metamorphosed at amphibolite- to granulite-facies conditions, comprised of metaultramafic rocks, amphibolites and metarhyolites. The CMLS is marked by two distinct phases of tholeiitic and calc-alkaline magmatism. Previous geochemical data and regional constraints suggest that the CMLS is possibly a metamorphosed arc-tholeiitic suite of the type boninite-basalt-andesite-rhyolite, interpreted in this study as a dismembered remnant of the juvenile oceanic arc. The rocks of tholeiitic affinity record a signature of depleted to enriched mantle with positive to weakly negative εNd(t) and predominantly positive εSr(t) values, indicating some degree of crustal assimilation. The rocks of calc-alkaline affinity present a signature of juvenile crust with εNd(t) close to the CHUR and weakly positive εSr(t) values. The Sm-Nd isochron age of 2736 ± 300 Ma obtained with εNd(i) = +0.4, suggests the edification of an intra-oceanic arc during the late phases of the Rio das Velhas Tectonothermal Event. The arc evolution involved tholeiitic magmatism in the early stages in association with calc-alkaline magmatism, of probably anatectic character, in the tardy-orogenic stages.
Nd and Sr isotopes; arc magmatism; Campo Belo Metamorphic Complex
