Arranjo Gradiente Elétrico Modificado e Métodos Potenciais na Exploração de Sulfetos Disseminados em Suçuarana, Jaguarari-BA

Abstract

Suçuarana with an area of 1.30km2 and 15km south of Caraiba Mine contains a copper bearing mafic body hosted by gneissic rocks. A geophysical survey was conducted by using gravimetric, magnetic, induced electrical polarization and resistivity methods. The results of the gravimetric and magnetic methods characterized the geometry of the ore bearing mafic body and defined the local geological pattern. Both the induced electrical polarization and resistivity surveys used a variation of the gradient array aiming to investigate its applicability for the evaluation of disseminated metallic sulphide deposits in the Curaçá Valley. There were connected to the transmitter 10 current electrodes, 5 at each lateral extremity of the area with a separation equal to 1 km, and it was used about 0.5A. There were connected to the receiver 2 potential electrodes keeping one fixed to permit calculation of the values of the electric field in both the E-W and N-S directions. The E-W electric field data showed good horizontal resolution with respect to vertical and sub-vertical conducting bodies elongated in the N-S direction (transverse to the current lines). The NS electric field showed several short conductors, under the action of the E-W current flow. Ordinarily the electric field would vanish in the N-S direction. But, in this case, did not happen because the disturbance in the field lines, caused by these bodies, creates positive and negative peaks of the electric field close to their north and south boundaries. A theoretical solution was developed for the electric field applied to the case of a vertical dike of conductivity σ1 within an environment of conductivity or, by assuming an infinite number of current electrodes. The theoretical curves were then used to interpret the conductivity and the width of the mafic body. The PFE results indicated a maximum value of 3.5% for a background of 2%. These results suggest a uniformly disseminated mineralization, with some small local concentrations. The electromagnetic coupling interference limited the usefulness of the gradient array. However, the use of 10 current transmission electrodes permitted a homogeneous distribution and resulted in a uniform response of the various conducting bodies,