Using GPR to Detect Bauxite Horizons in Laterite Deposits of Amazon Basin, Brazil

摘要

The GPR was applied on areas with laterite deposits and bauxite occurrences to see its capability of discriminate the different weathered horizons and detect the presence of bauxite horizon and also measure its width. The GPR was tested on two bauxite occurrences in Para State, Brazil: Paragominas Region and Trombetas River. The good quality of the radargrams was expected since the electric resistivity of the soil, evaluated by Vertical Electrical Sounding which reveals a resistivity varying from 450 to 3000 Ohm.m. The GPR data acquisition with constant-offset results in clear GPR sections where it was possible to separate four zones or horizons as well as its thicknesses. Each zone shows a different reflection pattern or radarfacies, which helps to differentiate them. The first horizon corresponds to the Belterra Clay, which is the most superficial layer, (AT); below, there is the laterite sequence composed by more three horizons, where the second one is a diffractions zone, which corresponds to a clay with concretionary laterites (ND); the third zone shows a homogeneous pattern and it corresponds to a massive ferruginous horizon (LT); an fourth zone shows discontinuous and small reflectors and/or chaotic pattern which corresponds to the main bauxite horizon (BX).