Copper resource estimation in PT X Batu Hijau, Regency of West Sumbawa, West Nusa Tenggara Province using geostatistical method

Abstract

The presence of copper deposits below the earth surface is generally disordered and its spread is uncontinuous, has varying grades, so it has a high degree of uncertainty in the estimation. One method of estimation uses geostatistics (kriging) where this method is suitable for mineral deposits that are full of uncertainties. The method is strongly influenced by geological data, models and information points (drill hole data). Kriging will estimate the uninformed area by connecting the information points around it.The research was conducted at PT “X”, located in Batu Hijau, West Sumbawa regency, West Nusa Tenggara Province, with the lithology of the forming of tonalite intermediates. The data used is a composite data from a combined fifteen-meter hole assay with the number of 1123 sample points. Spatial variations of copper content are known from the results of data processing. Estimated results with the kriging method found that the level of each block varies from 0.2 percent to 1.5 percent with total copper amounts of 3.4 million tons and the value of kriging variance per block varies from 0.05 to 0.16. Relative kriging standard deviation (RKSD) is used for copper resources classification in measured, indicated and inferred categories. The result of RKSD is copper measured resources of ± 700 tons, copper indicated resources ± 400 thousand tons, and copper inferred resources ± 3 million tons.