ANALYSIS OF NICKEL LATERITE DEPOSIT CHARACTERISTICS AND THE DISTRIBUTION OF COBALT (CO) IN THE NICKEL LATERITE DEPOSIT IN MABA AREA, EAST HALMAHERA, NORTH MALUKU

• Main Author: Aulia Rachman, Safrie
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/77884
• Institution: Institut Teknologi Bandung

Nickel is one of a metal that has been widely exploited and used in a broad sector of indutries. Indonesia is well known as one of the largest nickel producing country with one of its reserves is located in East Halmaera Regency. In the nickel laterite deposits, cobalt exists as an accompanying mineral which mostly being a byproduct of the metallurgical processes from the deposit. East Halmahera Regency is one of a place that has a Ni-Co laterite deposit in Indonesia. Cobalt’s large potential to become a critical raw material in the future will be a challenge for us to meet the demand of this element in the future. This study aims to determine the characteristics of nickel laterite deposit in the study area, to determine the enrichment zone and the distribution of this element in the lateritic nickel deposit in the study area, also to determine the elements or compunds which have association with cobalt in the cobalt enriched zone. XRF geochemical data from 121 drill holes, geological map of Ternate, and Digital Elevation Model (DEM) data were used as secondary data in conducting the analysis in this study. In addition, primary data such as core description, core box photos, and rock samples (18 handspeciments, 1 bedrock sample from the drill hole, and 9 rock thin sections) were also used in this study. The laterite profile in the study area consists of the layer of top soil, limonite, saprolite, and bedrock which at some points there are boulders between the layers. The limonite zone in the study is thicker in an area with a small slope and low elevation. In the laterite profile of the study area, the highest average value of Fe is in the limonite zone (35,37 wt%), the highest average value of MgO compounds are in the bedrock (35,33 wt%), while SiO2 in the saprolite zone (43,74 wt%). The highest average value of Co and MnO is in the limonite zone (0,13 wt% and 0,68 wt%). Nickel has a high average grade in the saprolite zone (1,14 wt%) in the laterite profile of the study area. Nickel laterite deposits in the study area are the result of weathering with a strong lateritization level with Fe elements as a result of the residual enrichment. Based on the value of the laterization index (IOL), the limonite layers in the study area have experienced weak – strong laterization. The value of the laterization index will be higher when it is in an area with a small slope. The movement of elements and compounds within each laterite zone depends on their solubility. This solubility makes MgO and SiO2 as well as Co and MnO have a similar geochemical patterns in the profile. Cobalt tends to be enriched in the limonite zone in the laterite profile of the study area. This element has a very strong correlation with MnO in the limonite layer based on the Spearman corellation results. In addition, MnO also has a fair positive correlation with Fe and Ni in the limonite. The abundance of MnO and Co is affected by the value of IOL. The higher of the IOL, the higher the MnO and Co grades in the study area. High value of the IOL will make the degree of crystallinity of the manganese oxide minerals in the limonite to be poor so that the cobalt contained in the minerals will be in higher grade. Based on the estimation result of the cobalt’s grade distribution using the inverse distnace weighting (IDW) method, the cobalt’s grade with relatively high values (%Co > 0,1%) is mostly in the areas that have high value of MnO, Fe, Ni, and IOL. On the other hand, areas with low MnO, Fe, and Ni grades tend to have lower grade of Co (%Co < 0,1).