CHARACTERISTICS OF LATERITE NICKEL DEPOSITS AND ANALYSIS OF COBALT (CO) ABUNDANCE AND THEIR DISTRIBUTION IN POMALAA REGION, KOLAKA, SOUTHEAST SULAWESI

• Main Author: Nayottama Gaffar, Bima
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/79637
• Institution: Institut Teknologi Bandung

Sulawesi Island is one of the locations in Indonesia that has abundant reserve of laterite nickel reserves due to the weathering process of ultramafic rocks. Nickel is an important metal that is used in various industrial sectors and the demand for it will continue to increase within years. Apart from nickel, laterite nickel deposits also contain another important metal, namely cobalt (Co). Administratively, the research area is in Pomalaa District, Kolaka Regency, Southeast Sulawesi Province with an area of 2.78 km 2 which is included in the IUP of PT Vale Indonesia Tbk. This study aims to determine the characteristics of laterite nickel deposits, to determine the cobalt element enrichment zone, the relationship of cobalt element with other elements or compounds in laterite nickel deposits, and estimate the distribution of cobalt element in laterite nickel deposits in the study area. The data used for this study consists of XRF geochemical data, core data, Kolaka sheet geological map, and Digital Elevation Model (DEM) data. Based on core and geochemical XRF analysis, the laterite nickel deposits in the research area is divided into three zones, namely limonite, saprolite, and bedrock. The basic rocks found in the research area are harzburgite and lerzolite. Laterite nickel deposits in the research area have hydrous Mg silicate and oxide type nickel deposits. The research area has experienced strong laterization which is characterized by the enrichment of Fe2O3 in the limonite zone as a final product in the laterite. Based on other XRF geochemical analysis, cobalt element is enriched in the limonite zone. Spearman Correlation Analysis (rs) indicates that cobalt element has a very strong positive correlation with MnO (rs=0.9), a moderate positive correlation with Ni (rs=0.42), and a weak correlation with SiO2 and MgO. The abundance of the cobalt element is influenced by the presence of MnO which has a tendency to be controlled by the index of laterization (IOL). The estimation of cobalt element distribution was conducted using the Inverse Distance Weighting (IDW) method in the limonite zone. The estimation results indicate that the high concentrations of cobalt element (Co > 0.2 wt%) is located in the southwest and the south of the study area which have a relatively thin limonite layer but is thought to be controlled by the geological structure. The low concentrations of cobalt element (Co < 0.1 wt%) is located in the west and the east of the study area with a relatively thicker limonite layer.