2D-3D liberation comparisons in HCTtestwork for the Hannukainen IOCG Deposit, Finland.

摘要

The Hannukainen Iron-Oxide-Copper-Gold (IOCG) deposit is located in northern Finland approximately 25 km northeast of Kolari. The deposit consists of the Hannukainen deposit and its northern extension, the Kuervitikko deposit. Geochemical assessment of high sulfur potentially acid-forming waste rock has included kinetic humidity cell tests (HCTs) lasting >200 weeks. The onset of acid generation exhibits a considerable lag time which is hypothesized to be caused by the coarse crystallinity of sulfide minerals and a subsequent low oxidation rate. Sulfide grain size, crystallinity and liberation are fundamental parameters controlling the quality of HCT leachate and the balance between them can be complex. In order to understand the relative importance of these textural controls on acid generation, pre-leach HCT material was split into several size fractions and analysed by 2D (Zeiss Mineralogic) and 3D (High-resolution X-Ray computed tomography) methods.Results from the 2D Mineralogic show significant differences in sulfide modal mineralogy and liberation by size fraction. Sulfide deportment is dominant by pyrrhotite, pyrite and chalcopyrite with increasing majorities in the fine size fractions, which also show greater degrees of liberation. The long lag time in acid generation is primarily attributed to sulfide crystallinity leading to a slow reaction time. At this stage in the analysis HRXCT has shown similar liberation values across the size fractions but crucially currently without the capability to distinguish between the different sulfide phases, particularly pyrite and pyrrhotite. This mineralogical separation, which is straightforward in SEM-based applications is a crucial ongoing research question for the application of HRXCT in HCT programs.