Decoupling the effects of alteration on the mineralogy and flotation performance of Great Dyke PGE ores

T. Dzingai,M. Becker,B. McFadzean,M. Tadie

doi:10.17159/2411-9717/1487/2021

Abstract

Ores from a single deposit may exhibit extensive variability in their mineralogy and texture. The ability to quantify this variability and link it to mineral processing performance is one of the primary goals of process mineralogy. This study focuses on the effect of alteration in three platinum group element ore samples from the Great Dyke in Zimbabwe - two of which were more pristine compared to the third, which was locally classified as 'oxidized' ore. These ores are known to be characterized by varying degrees of alteration, resulting in numerous challenges in flotation and affecting both grade and recovery. Alteration, by near-surface oxidation, of the valuable base metal sulphides and platinum group minerals resulted in lower flotation recoveries of Cu, Ni, Pt, and Pd. Evidence of incipient oxidation was more readily observed in the base metal sulphide assemblage than the platinum group mineral assemblage, even though the loss in recovery (because of oxidation) was most significant for Pd. Alteration through hydration resulted in a significant increase in mass pull and dilution of concentrate grade through the inadvertent recovery of naturally floating gangue comprising composite orthopyroxene and talc particles. In this study, the amount of naturally floating gangue was more strongly correlated with the talc grain size distribution than the grade of talc in the flotation feed. The oxidation and hydration alteration reactions are not necessarily mutually exclusive, although one may be more dominant than the other, giving rise to ore variability.

Highlights

This study focuses on the effect of alteration in three platinum group element ore samples from the Great Dyke in Zimbabwe – two of which were more pristine compared to the third, which was locally classified as ‘oxidized’ ore
The ability to manage ore variability is a major challenge faced by the mining industry at present
Many existing plants cannot necessarily deal with ore variability since their design specifications have historically focused on averaged ore characteristics (e.g. Powell, 2013)

Summary

Introduction

The ability to manage ore variability is a major challenge faced by the mining industry at present. Many existing plants cannot necessarily deal with ore variability since their design specifications have historically focused on averaged ore characteristics (e.g. Powell, 2013). As design flexibility is not always an option for existing plants, the need for optimization of these operations based on process mineralogy is increasing (Lotter et al, 2011, 2018; Baum, 2014). The major contributors to ore variability include hydrothermal alteration, oxidation, and weathering of a pristine ore deposit. There is, a need for an understanding of the mineralogical aspects of ore variability, especially those arising from alteration, and the consequent assessment of how it can be managed. Some of the ways of managing ore variability include ore sorting, stockpiling and campaigning, blending, or the use of tailored reagent suites based on the mineralogy of the run-of-mine ore

Methods

Results

Conclusion