3D Inversion of airborne gravity gradiomentry for iron ore exploration in Brazil

Cericia Martinez∗†,Yaoguo Li†, Richard Krahenbuhl†, Marco Braga‡
†Center for Gravity, Electrical, and Magnetic Studies, Department of Geophysics, Colorado School of Mines
‡Companhia Vale do Rio Doce, Brazil

SUMMARY

We present the 3D inversion results of gravity gradiometry data over iron ore deposits in Minas Gerais, Brazil. The host formation for the iron ore is largely the Cauˆe Itabirite, along with the overlying Gandalera Formation and, to a lesser degree, the underlying Batatal. Consequently, the iron ore bodies have a distinctly high density contrast and produce well defined anomalies in airborne gravity gradiometry data. We have carried out a preliminary study to apply a 3D inversion to a 20-km2 subarea of data from a larger survey to demonstrate the utility of such an algorithm both in delineatng the ore deposit and in estimating the reserves. We focus on three components of the data (Tzz, Txz, and Tyz). The commonly discussed Tzz componente is sufficient to produce geologically reasonable and interpretable results, while including the two horizontal componentes increases the resolution of the recovered density model and improves the ore delineation.