Geostatistical evaluation of the Abu Tartur phosphate deposit, Western Desert, Egypt

CIM Bulletin, Vol. 83, No. 934, 1990

A. Sahin and A.A. Abdul-Latif,Department of Earth Sciences, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia

The phosphate deposit, located in the Abu Tartur plateau between the Kharga and the Dakhla Oases in the southern part of the Western Desert of Egypt, is the largest of its kind in the country. The phosphates are found in two horizons referred to as the Lower and Upper Phosphate Horizons within the Late Campanian Sibaiya Formation which belongs to the Nubia Group. This paper presents the results of a geostatistical study on the main phosphorite bed at the base of the Lower Phosphate Horizon which contains almost all the commercial reserves in the area. After semivariogram modelling for the phosphate thickness and accumulation, ordinary block kriging was employed to estimate the values of these variables in blocks of 400 m by 400 m dimensions. The kriging results, which are presented in the form of contour maps, can be of considerable use in both future exploration and exploitation of the deposit. The grade-tonnage relationship based on the grade estimates derived from the corresponding thickness and accumulation estimates indicates the existence of 453.9 x 106 tonnes of phosphate above a cut-off grade of 18% P2O5. The mean grade of this tonnage has been estimated to be 25.77% P205.

Keywords: Exploration, Geostatistics, Phosphate deposits, Abu Tartur, Kriging, Grade estimation