Métodos geofísicos aplicados à prospecção de cobre na Serras de Carajás - Pará

Abstract

Through an agreement between the Federal University of Para and the Rio Doce Geologia e Mineração Company, a geophysical research was carried out in the area known as ALVO 1, MM1, Serra dos Carajás, south of Para, Brazil. The magnetic, electrical induced polarization and AFMAG methods were applied, to detect the distribution of copper in subsurface. This work was carried out both on a 9 km2 reconnaissance area (ALVO 1) and on a 0.63 km2 detail area (Corpo 2). The AFMAG method detected various conductors displaced from each other by possible faulting. The orientation of these conductors, coincides with the dominant strike of the body of schist which contains copper sulfide, associated with an iron formation. The close correlation they have with the magnetic anomaly, may imply that the AFMAG anomalies are caused, firstly by the iron formation and secondarily by the sulfide. The magnetic method detected strong anomaly over the iron formation. The displacement of the segment of the anomaly impleis faulting. This method is very important in the area due to the association of the sulfide zone with the iron formation. The electrical induced polarization/resistivity method detected anomalies with PFE, varying from 6 to 12% approximately. Several of these anomalies were confirmed by mechanical sounding and laboratory research (Rocha, 1979). It was verified that these anomalies were caused by a combined effect of the iron formation and the sulfide body. The geophysical research carried out at this pilot area turned out to be very important considering the fact that its results can be successfully extrapolated to a larger area with the same geological characteristics.