CSA Global Principal-Nickel, Mick Elias recently presented on ‘Dealing with Nickel-Cobalt Laterite Deposit Complexity’ at The 11th MGEI (Indonesian Society of Economic Geologists) Annual Convention 2019 between 24-26 September, 2019 in Bogor, West Java in Indonesia.
Understanding the nature of nickel (Ni) deposits requires an understanding of the factors that control their formation. Ni laterite deposits are formed by the prolonged and pervasive weathering of Ni silicate-bearing ultramafic rocks, and it is mainly the variable nature of the weathering process and its effect on the ultramafic rock that results in their complexity.
The nature of a Ni laterite deposit is a function of many factors influencing the efficiency and extent of chemical weathering. The principal factors are parent rock type, climate, topography, drainage, tectonics and structure. Clearly many of these climatic and geological factors are closely interrelated, and the characteristics of a profile at any one place can best be described as due to the combined effect of all the individual factors acting over time, rather than being dominated by any single factor.
The practical difficulties imposed by the complexity of Ni laterites are mainly manifested in estimating mineral resources and ore reserves, and in their commercial exploitation from mining through processing. The boundaries between the horizons in Ni laterites are invariably highly irregular, particularly between the saprolite and the bedrock, on all scales and efforts to model deposits for resource estimation based on exploration and resource drilling come with an unavoidable degree of uncertainty.
Mining presents its own set of challenges, arising from the difficulty in recognising subtle changes in grade and mineralogy in the mining face which can result in ore loss or dilution. Because of the constraints imposed by different metallurgical processes on the physical and chemical composition of the feed ore, it is important to be able to work within those limits.
Mick is an expert in all aspects of nickel resource assessment and development in both laterites and sulphides. He has 35 years’ experience in the nickel industry conducting project generation and evaluation, exploration planning and management, development studies, open cut and underground mine geology, resource/reserve estimation, and resource economics. He has worked on the technical and financial evaluation of many nickel deposits throughout Australia. His international experience includes Cuba, Indonesia, Madagascar, Philippines, New Caledonia, Canada, Turkey and Brazil.