Study of Radarfacies in Auriferous Placers at Baixada Cuiabana, Mato Grosso (Brazil)

The state of Mato Grosso (MT) is the fifth largest gold producer in Brazil, with much of it coming from the Baixada Cuiabana region. In this region, gold occurs in primary deposit associated with quartz veins and their host metasedimentary rocks of the Cuiabá Group and secondary sedimentary deposits (such as colluviums, alluviums and eluviums), the latter being quite profitable and easy to exploit. The gold exploitation in these areas often results in deforestation of the Pantanal biome, as mining uses random subsoil scarification to locate the deposits. In this study, the Ground Penetrating Radar (GPR) geophysical method was applied to differentiate and locate alluvial, colluvial and eluvial deposits. This may help to mitigate the local deforestation process. Thus, the acquisition of GPR data took place in a gold mine located in the municipality of Nossa Senhora do Livramento. The GPR recordings were done with a 200 MHz shielded antenna, along with ditches and gravel exposures. The results show variability of the electromagnetic wave velocity between 0.085 to 0.146 m/ns, with normalized amplitudes of -1 to 1 ranging between maximum values of -0.8 and 0.8. The lowest velocity values were found for gravels of alluvial origin. The intermediate velocity of 0.090 m/ns is associated with eluviums and the highest velocity (0.146 m/ns) is associated with gravel of colluvial origin. GPR was efficient to distinguish secondary sedimentary deposits in the Baixada Cuibana, becoming a prospective alternative for the region.