PETROLOGY AND GEOCHEMISTRY OF ULTRAMAFIC ROCK AND ITS IMPLICATION TO NICKEL-COBALT ENRICHMENT IN OVERLYING LATERITIC ZONES AT THE BLOCK X, SOUTH SULAWESI
DOI:
https://doi.org/10.51835/ijeg.2025.1.1.488Abstract
Targeting sectoral strategies toward low-carbon technologies is important as it encourages optimizing critical and alternative mineral resources. A detailed study is needed to maximize the utilization of mineral resources. Nickel and cobalt are critical elements that have a significant role in the industrial world, focused on the transition to environmentally sustainable energy. The research aims to identify the geochemical characteristics of rocks, visualize the distribution of nickel and cobalt enrichment zones, and the degree of lateritization by using data collection methods (geological mapping, core logging), laboratory analysis (petrography and XRF (X-ray fluorescence)) used to assay and collar data of 410 drill points. The study area is composed of ultramafic rock groups, dunite, harzburgite, lherzolite, wehrlite, and serpentinite alteration rocks. The Limonite zone shows Ni has a positive correlation with Co and Mn. Meanwhile, Fe shows a negative correlation with SiO2, with an average content of Ni 0.96%, Co 0.09%, Fe 46.6%, SiO2 7.16%, and MgO 2.01%. Saprolite zone, MgO, and SiO2 correlate negatively with Fe with average contents of Ni 2.08%, Co 0.05%, Fe 16.2%, SiO2 36.9%, MgO 22.1%. Based on the degree of lateritization, limonite shows S/SAF indices ranging from 0.019-0.044% (high lateritization) with residual products soils with high iron, saprolite 0.62-0.79% (weak lateritization-saprolitization) with residual products soils and rocks with more diverse chemical composition and bedrock between 0.80-0.82% (unlateritized). The saprolite zone shows the enrichment of nickel, while cobalt tends to enrich the lower zone of limonite towards transition, related to the process of oxidation and absorption of minerals. Dunite contains higher nickel content compared to other ultramafic rocks, with an average ore Ni value in the limonite zone of 1.07%, saprolite 2.24%, and bedrock 0.43%.
Keywords: nickel, cobalt, limonite, saprolite, lateritization
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