Investigação das mineralizações de cassiterita e minerais do subgrupo da columbita em Cristiano Otoni e Caranaíba – MG

Abstract

The municipalities of Caranaíba and Cristiano Otoni in the State of Minas Gerais are part of the tectonic subdivision called the Cinturão Mineiro. This region can also be considered as an eastern extension of the Pegmatitic Province of São João del Rei. This province is known worldwide for its mineralizations of Sn, Nb, Ta and Li. In this work, 26 points mineralized with cassiterite and minerals from the columbite subgroup were located in drainages, placers, pegmatite, abandoned mines and micro-basin with white clay. The spot analyzes in the SEM-EDS on 10 cassiterite grains indicated that they were pure cassiterite when analyzed inside the mineral. In four analyzes tantalum impurities were detected, its content being insignificant and it is in the chemical structure of the mineral. When analyzing the edges and fractures of the mineral, the Sn content reduces in atomic proportions. Two inclusions containing Nb, Ta and Sn were found, surrounded by low-grade cassiterite and with pure SnO2 inclusions. Lithogeochemical analyzes showed that the Termite granite is the result of intraplate magmatism. The other lithological units analyzed in geochemistry, Caatinga gneiss, Chuí tonalite, and Senhora dos Remédios granodiorite, showed a compatible result of accretionary magmatic arcs. The geophysical map of total magnetic field defined a signature for the metasedimentary rocks of the Carandaí Basin and for the lithological units studied in this research. The Analytical Signal Amplitude geophysics registered a different signature for the Cupim granite and for the Caatinga gneiss, suggesting an unmapped portion of the Cupim granite. The uranium element map shows values greater than 3 ppm in the Cupim granite, in the Chuí tonalite and in part of the Caatinga gneiss. The pegmatite was classified as NYF type according to Cerný & Ercit (2005), as it is associated with I-type termite granite and is close to metaultramafic rocks.