Origen de circones detríticos ricos en Hf de São João del Rei, Minas Gerais (Brasil)

Abstract

Heavy concentrates obtained by pane sampling on several creeks near São João del Rei, Minas Gerais (Brasil) provide unusual Hf-rich zircons. Image and chemical analyses performed on these zircons by SEM and LA-ICP-MS show uncommon textural and compositional features. The core of zircons exhibits a complex texture including evidences of hydrothermal recrystallization. Here it is also conspicuous the abundance of rare metal minerals as inclusions. The average content of HfO2 in the core is of about 12 weigh %. The rim of zircons shows different zoning features with HfO2 content up to 35 weigt %. An origin related with rare element pegmatites and further reworking by hydrothermal fluids is suggested as the more suitable scenario for these unusual zircons