CHARACTERISTICS STUDY OF NICKEL LATERITES DEPOSITS, 3-D GEOLOGICAL MODELING, AND ESTIMATION OF NICKEL RESOURCES USING GEOSTATISTICAL METHOD ORDINARY KRIGING IN LAREONAI, MOROWALI REGENCY, CENTRAL SULAWESI PROVINCE

• Main Author: Agung Purnama, Rahmat
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/73143
• Institution: Institut Teknologi Bandung

<p align="justify"> Nickel (Ni) is currently a significant commodity in the mining industry. The electric car battery industry has grown exponentially, which has been affected by increasing nickel. Research is needed to know the quantity and quality of nickel and the model of deposits in the Laroenai area. The study aims to understand the characteristics of the deposits, conduct geological modelling, and estimate the nickel resource in the research area. The data used was 2241 samples from 147 exploration drill holes, observation results of laterite profiles, bedrock petrography, DEM, and other literary data. The profile of nickel laterite deposits in the study area is divided into limonite, saprolite and bedrock. The bedrock types found are lherzolite, harzburgite, serpentinized dunite and serpentinite. The residual enrichment process causes Fe and Al2O3 to be enriched in the limonite zone. Ni accumulation occurs in the saprolite zone due to supergene enrichment processes. The degree of lateritization in the limonite tends to be moderate to strong, while it is relatively weak to moderate in the saprolite. The lateritization pattern develops towards Fe due to residual enrichment. The ridge topography is proven to produce a relatively higher enrichment of nickel laterite compared to other areas in the study area. Based on geological interpretation, the 3-D block model is obtained through a correlation process between drill holes. This interpretation considers laterite characteristics and geological domains. Domain analysis got two geological domains, limonite and saprolite. Limonite is statistically characterized by high Fe, low SiO2 and low MgO populations, while saprolite is characterized by low Fe, high SiO2 and high MgO populations. The shape of the ore body tends to follow the topography of the northeast – southwest trending ridge. This is also evidenced by the continuity direction analysis of the Ni semivariogram, which shows an N 45 E direction, both in limonite and saprolite. The estimation of the block model uses the geostatistical ordinary kriging method. This method calculates unsampled points based on composite drill hole data concerning their spatial correlation. The estimation results are the nickel value and kriging efficiency in each block unit. The quality of nickel included in the resource is determined based on the cut-off grade (COG) value, with the limonite zone using a COG of 0.9% and the saprolite zone using a COG of 1.5%. Kriging efficiency is used to measure geological confidence in dividing the resource. Resource classification follows the Kode KCMI 2017, divided into measured, indicated and inferred resources. The limonite zone has nickel resources of 295.718 tons (measured), 198.812 tons (indicated) and 1.963.344 tons (inferred). The saprolite zone has nickel resources of 755.593 tons (measured), 279.031 tons (indicated) and 209.968 tons (inferred).