ESTIMATION AND SIMULATION THE TOP OF BEDROCK ZONE ELEVATION OF LATERITIC NICKEL DEPOSIT AT PAKAL ISLAND, NORTH MALUKU PROVINCE BY ORDINARY COKRIGING AND SEQUENTIAL GAUSSIAN SIMULATION METHOD

• Main Author: BUDIYONO (NIM : 22107007), ARIF
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/19913
• Institution: Institut Teknologi Bandung

The problem in exploration of lateritic nickel deposit arising when there are some unfinished drillholes which did not penetrate the bedrock zone yet. They will generate the not optimum resource model of lateritic nickel deposit. The bedrock zone in the location of unfinished drillholes was estimated by Ordinary Cokriging methods utilizing the top elevation of high saprolite ore zone as secondary data while the primary data is the top elevation of bedrock zone or bottom elevation of high saprolite ore zone derived from the finished drillholes. The high degree of linear coefficient correlation and data distribution similarity between the two variables yields spatial correlation and spatial structure coherence characteristics that satisfy multivarian spatial modelling condition by Linear Model of Coregionalization methods. <br /> <br /> Ordinary Cokriging approach statistically has improved the estimation results compared to the Ordinary Kriging due to the smaller estimation variance mainly in the Central Block of Pakal Island which the spatial structure is simpler and the spatial characteristics is drift-free relatively. Kriging with Trend method was also applied to compare the estimation result of top bedrock elevation. The sampling density pattern that incorporates the sampling position of secondary variable to primary variable also affecting the reduction of estimation variance by Ordinary Cokriging. For the more complex spatial structure and higher data variability such as in South and North Blocks of Pakal Island, Sequential Gaussian Simulation method which honored the histogram and cumulative distribution function of original data was applied to generate the local variability of top bedrock elevation. Conditional stochastic simulation methods has succeed in gaining comprehensive picture of bedrock topography since the profile of bedrock zone in Pakal Island is relatively complex.