ORE BODY MODELING AND RESOURCE ESTIMATION ON URANIUM MINERALIZATION OF REMAJA SECTOR, KALAN REGION, WEST KALIMANTAN USING GEOSTATISTICAL METHOD

• Main Author: Cahya Ciputra, Roni
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/66284
• Institution: Institut Teknologi Bandung

Manual orebody modeling (explicit modeling) of uranium mineralization in the Remaja Sector, Kalan, West Kalimantan generally takes a long time and is subjective. On the other hand, automatic modeling (implicit modeling) is faster, objective, and equipped with uncertainty factors. This study aims to analyze the geological structure concerning the variogram parameter analysis, the comparison between the ore body model using the geostatistical Sequential Indicator Simulation (SIS) method to the manual ore body model to obtain a domain for resource estimation and to estimate uranium resources. The lithology database that has been validated, composited, and transformed into binary format is used as input for variogram analysis and SIS simulation. Meanwhile, the Ordinary Kriging (OK) method was used to estimate the levels of eU3O8 from the results of the analysis of gamma-ray logs that had been made composites with 1 m intervals. The orientation of the lithology position corresponds to the anisotropy of the variogram map binary data of siltstone lithology, schistositic metapelite, and metaampelite, while the orientation of the uranium veins corresponds to the anisotropy of the binary data map variogram mineralized zone and the eU3O8 grade data of Block A. Therefore, a directional variogram in this direction was used to construct an experimental variogram of the corresponding data. The Sequential Indicator Simulations were carried out in Blocks A and B with block sizes of 6×6×6 m3 and 5×5×5 m3 respectively, taking into account the distance between the lithological binary data and grade data. The simulation results were processed to produce a probability model or lithology proportion. By using maximum probability as block lithology, simulation results were well validated by the composite database histogram, the lithologies along the tunnel on the geological map of level 450 m.a.s.l. of the Eko Remaja Tunnel, and the lithologies along boreholes. The weakness of the geostatistical orebody model was that the results depend on the input parameters. Meanwhile, several advantages of the geostatistical ore body model were including a faster processing process, equipped with an uncertainty factor, and the block size of the model has taken into account the distance between grade data so that it can be used directly for grade estimation. Quantitatively, the geostatistical orebody model had a higher average percentage of conformity to the lithology of the mineralized zone along the borehole than the manual orebody model. Therefore, the geostatistical ore body model was used as the limit in grade estimation in the Remaja Sector. The resource model that has been developed in this study has two types of uncertainty factors, namely the lithological probability of the realization of the SIS simulation process results and the kriging variance of OK. In the Remaja Sector Block A resource model with an ore body probability of 0.5, in total there are 570 tons of uranium equivalent with a proportion of measured resource categories of 449 tons of uranium equivalent, an indicated resource of 95 tons of uranium equivalent, and an inferred resource of 26 tons of uranium equivalent. In Block B, there are total resources of 106 tons of uranium equivalent with the proportion of measured resource categories being 62 tons of uranium equivalent, an indicated resource of 40 tons of uranium equivalent, and an inferred resource of 4 tons of uranium equivalent.