Determinação da densidade in situ do minério da mina de bauxita de Juruti-PA através de método prático e krigagem ordinária

Abstract

The estimation of resources and reserves of solid minerals deposits depends on a correct geological model, result of a good estimate of grade and bulk density. Although the last factor possess an extreme relevance to calculate ore tonnage, it is common to overlook this parameter basing its value on little determinations or even, assuming it by comparisons with similar deposits. The correct value of the bulk density determination minimizes the uncertainty on deposits tonnage estimation and brings numerous benefits such as improvement of predictability, more accuracy on the geometry of the deposit models, more adherence and long and short-term reconciliation planning. On the present study were made tests to determinate the bauxite in situ bulk density located on the mine in Juruti in each of four working faces, and were elaborated a spatial distribution map of this parameter by kriging interpolation method. The weighted average in situ bulk density obtained by the tests were 1,67 t/m³, whereas the short-term planning uses the value of 1,71 t/m³. The dry bulk density was 1,53 t/m³ which represents a difference of 3,8% related to density methods average of drill core (1,59 t/m³) and 10% in relation to the density used to evaluate the bauxite resource deposit in Juruti-PA. The density estimate value by the kriging interpolation was consistent according to the working face tests results. The elaboreted map indicates a increase of in situ bulk density towards mine advance and a overestimation of Juruti’s resources deposits due to the use of a dry in situ density of 1,70 t/m³.