OCORRÊNCIAS DE CASSITERITA E DE MINERAIS DO SUBGRUPO DA COLUMBITA NOS MUNICÍPIOS DE CONSELHEIRO LAFAIETE, CARANAÍBA E CRISTIANO OTONI, SUL DO ESTADO DE MINAS GERAIS.

Occurrences of cassiterite and minerals of the columbite subgroup in the municipalities of Conselheiro Lafaiete, Caranaíba and Cristiano Otoni, South of the State of Minas Gerais

Abstract

The municipalities of Conselheiro Lafaiete, Caranaíba and Cristiano Otoni, in the state of Minas Gerais, are inserted in the tectonic compartmentation called Cinturão Mineiro. This region is considered as an extension of the São João del Rei Pegmatite Province, known for its Sn, Nb, Ta and Li mineralizations. The principal  units present are  Cupim Granite and  Caatinga Gneiss. Fifteen mineralized samples with cassiterite and minerals from the columbite subgroup were identified in creeks, placers, pegmatite and abandoned mines. SEM-EDS  analyses of cassiterite grains indicated the presence of tantalite and niobium inclusions, and a high tin content. Lithogeochemical analyses demonstrated that the Cupim Granite is the result of intraplate magmatism. The Caatinga Gneiss displays results compatible with an accretionary magmatic arc environment. The aerogeophysical map of the Analytical Signal Amplitude displays a different signature for the Cupim granite, and suggests an uncharted area associated with this unit. The Gammaspectrometric map of the element uranium shows values above 3 ppm for the Cupim Granite and part of the Caatinga Gneiss. The pegmatite was classified as being of the LCT type according to Cerný & Ercit (2005), and is associated with the Cupim Granite.