Avaliação do impacto da utilização de diferentes bases de dados de densidade na estimativa da massa em inventários de recursos minerais

Abstract

When evaluating a mineral resource and building a mineral inventory, density is a key factor, because it is used to calculate the deposit tonnage. However, in the estimation process, density itself is not being used properly, because the companies are commonly using an average density value for each lithology of such deposit, instead of considering its regional variability. To diminish such mistakes, this study focuses on a comparison between different ways to obtain density value, so that more accurate estimations can be produced. To support such comparison, three estimations will be produced using ordinary kriging for each lithology, each for a different density acquisition method, one using the direct laboratory methods, one using the gamma-gamma logging geophysical method and the other using the calculated density obtained from the normative mineralogy. To compare those values, it was necessary a selection of blocks which had density estimated simultaneously for the three methods, and the tonnage was calculated for each of the density methods, so that density and mass could be compared, considering the gamma-gamma geophysical logging method as reference. The estimations were produced for three different lithotypes, the compact itabirite, the friable itabirite and the rich friable itabirite. The database is from an iron deposit from the Minas Gerais state, at the region known as Quadrilátero Ferrífero.