Reconstrução e comparação de trajetórias P-T no Sistema de Nappes Andrelândia, sul da Faixa Brasília, MG

The Andrelândia Nappe System consists of three main nappes, from bottom to top: the lower Andrelândia nappe, the middle Liberdade nappe and the upper Tres Pontas-Varginha nappe and associated klippen, Pouso Alto, Aiuruoca, Carvalhos and Serra da Natureza. In the Andrelândia Nappe System, metamorphism increases from north to south and east to west, with the highest temperatures and pressures recorded in rocks of the Tres Pontas-Varginha nappe and associated klippen. Samples of pelitic and mafic rocks were selected from the three nappes to determine the conditions of metamorphism using the program THERMOCALC. In this study, peak metamorphic conditions were calculated for the following samples: one sample of the Andrelândia Nappe (688 ± 35 °C and 5.63 ± 0.9 kbar), one sample of the Liberdade Nappe (648 ± 23°C and 7.41 ± 1 kbar), and three samples of the Carvalhos Klippe (845 ± 53oC and 15.7 ± 5.2 kbar, and 847 ± 45oC and 13.6 ± 5.8 kbar for two samples of pelitic granulites respectively, and 854 ± 71oC and 15 ± 1.4 kbar for one sample of mafic granulite). P-T paths inferred on the basis of the observed textures are clockwise and typical of collisional belts.