Geophysical modeling of two willemite deposits, Vazante (Brazil) and Beltana (Australia)

Abstract

Non‐sulfide zinc deposits (zinc “oxide” deposits) are becoming favored exploration targets due to new developments in metallurgy allowing for solvent‐extraction and electrowinning. While geologic understanding of the genesis of these types of deposits is improving, there has been little work aimed at documenting their geophysical responses. We therefore investigate the geophysical signature of two major hypogene non‐sulfide deposits, Vazante in Brazil and Beltana in Australia. Physical property values were measured for each deposit site and combined with geologic information to generate two‐ and three‐dimensional models for geophysical modeling. Results indicate that gravity method will be valuable at both deposit sites for direct detection of either ore and/or the alteration halo associated with mineralization. Simulated magnetic data indicate that the responses will not be large enough at either site to warrant magnetic method in exploration for willemite. Electrical method simulations vary for the two deposit sites. At Vazante, neither DC resistivity or induced polarization (IP) will generate a detectable response based on physical property values; while at Beltana, simulated data and inversion results indicate that both techniques will be valuable as an exploration tool. It is clear based on these simulations that geophysics can be effectively used to explore for nonsulfide zinc deposits either through direct detection of ore bodies or through imaging of associated hydrothermal alteration.