Surface Paste Disposal of High-Sulfide Tailings at the Neves Corvo Mine in Portugal.Part 1: Estimation of Tailings Desaturation and Implications on ARD Generation

摘要

Neves Corvo is a world-class underground copper-zinc mine located within a semi-aridclimate in Portugal, where the average annual evaporation rate is three times greater thanprecipitation. The mine has been operating since 1988 and generates pyritic tailings that havea very high acid generation potential. Tailings management will change from slurry tailingsto sub-aerial placement of paste onto the existing tailings. Upon closure of the mine, the Cerro do Lobo facility will be capped to prevent paste tailingsdesaturation and oxygen diffusion into the reactive tailings body, thereby preventing sulphideoxidation and the generation of acid rock drainage (ARD). Paste desaturation may occur withthe loss of water due to surface evaporation as well as due to seepage through the bottom ofthe tailings. The evolution of the desaturation process will be strongly affected by the typeand performance of the cover system installed on the paste. This paper presents the results of numerical models assessing the impact of different coversystem configurations and infiltration rates in the paste desaturation process over a period of100 years. The model results will be used to define the type of cover system that best suits thesite and guides the design criteria, such that tailings drainage be balanced with surface waterinfiltration to minimize paste tailings desaturation.