Quantifying the Role of Chemical Weathering in Nickel and Cobalt Mobilization and Redistribution in Lateritic Profiles, Sulawesi, Indonesia

Abstract

This paper explores the influence of chemical weathering on the mobilization and redistribution of nickel and cobalt within lateritic soil layers in Koninis, Banggai Regency, Central Sulawesi. The formation of laterite here results from prolonged chemical alteration of harzburgite bedrock that has undergone serpentinization. Based on geochemical analysis, nickel generally accumulates in the saprolite zone, where Ni is released from primary minerals and then bound in secondary minerals, especially nickel-rich lizardite. Conversely, the highest cobalt accumulation is found in the limonite zone and is usually associated with goethite. The mobilization and distribution of these two elements are controlled by ongoing chemical weathering, as reflected in the ternary diagrams Mg-SiO₂-(Al₂O₃ + Fe₂O₃) and SAF (SiO₂ - Al₂O₃ - Fe₂O₃). The diagram shows a consistent pattern: soluble elements Mg and Si decrease, while immobile elements such as Fe, Al, and Cr become richer from the bedrock to the surface. The results of this study also confirm that lateritization not only increases the ore element content but also determines the spatial distribution of Ni and Co in the laterite profile, with bedrock mineralogy and secondary minerals as the hosts.