U-Pb SHRIMP monazite ages of the giant Morro Velho and Cuiaba gold deposits, Rio das Velhas greenstone belt, Quadrilatero Ferrifero, Minas Gerais, Brazil

摘要

U-Pb SHRIMP results of 2672 + - 14 Ma obtained on hydrothermal monazite crystals, from ore samples of the giant Morro Velho and Cuiaba Archean orogenic deposits, represent the first reliable and precise age of gold mineralization associated with the Rio das Velhas greenstone belt evolution, in the Quadrilatero Ferrifero, Brazil. In the basal Nova Lima Group, of the Rio das Velhas greenstone belt, felsic volcanic and volcaniclastic rocks have been dated between 2792 + - 11 and 2751 + - 9 Ma, coeval with the intrusion of syn-tectonic tonalite and granodiorite plutons, and also with the metamorphic overprint of older tonalite-trondhjemite-granodiorite crust. Since cratonization and stable-shelf sedimentation followed intrusion of Neoarchean granites at 2612+3/-2 Ma, it is clear that like other granite-greenstone terranes in the world, gold mineralization is constrained to the latest stages of greenstone evolution.