عنوان مقاله [English]
In present research geometric method using Surfer software and geostatistical estimation method have been used to evaluate sodium sulfate reserve in the central part of Mighan-Arak sedimentary basin. Using geometric method, average assay of the deposit and net ore reserve were calculated 25.1 percent and 3223581.7 tons respectively. In order to employ geostatistical method, first assay and thickness data of test pits, was statistically analyzed. The results of this stage showed a log-normal distribution for assay data and a normal distribution for thickness data. According to the results of variography and analysis of spatial structure, ordinary block log kriging was employed for assay data as well as inverse squared distance method for thickness data. By this method the size of estimated blocks was selected 60*58 m, average assay of sodium sulfate was obtained 24.98 percent with average standard deviation of 1.09 percent, average thickness of blocks was gained about 2.57m with average standard deviation of 0.23 m while the upper and lower limit of the mineral deposit are 5275221.4 and 6286683.8 tons respectively in the reliability surface of 95 percent. Based on the results of this research, the difference of calculated reserve by geometric method through Surfer software and kriging is 2557370.9 tons that means 44.2 percent. However the results of kriging estimation are highly accurate and more reliable due to be unbiased having minimum estimation error.