Application of Covariance Clouds for Estimating the Anisotropy Ellipsoid Eigenvectors, with Case Study in Uranium Deposit

Various methods of Kriging and nonlinear geostatistical methods considered as acceptable methods for resource and reserve estimations have characters such as the least estimation variance in their nature, and accurate results in the acceptable confidence levels range could be achieved if the required parameters for the estimation are determined accurately. If the determined parameters don’t have the sufficient accuracy, 3-D geostatistical estimations will not be reliable any more, and by this, all the quantitative parameters of the mineral deposit (e.g. grade-tonnage variations) will be misinterpreted. One of the most significant parameters for 3-D geostatistical estimation is the anisotropy ellipsoid. The anisotropy ellipsoid is important for geostatistical estimations because it determines the samples in different directions required for accomplishing the estimation. The aim of this paper is to illustrate a more simple and time preserving analytical method that can apply geophysical or geochemical analysis data from the core-length of boreholes for modeling the anisotropy ellipsoid. By this method which is based on the distribution of covariance clouds in a 3-D sampling space of a deposit, quantities, ratios, azimuth and plunge of the major-axis, semi-major axis and the minor-axis determine the ore-grade continuity within the deposit and finally the anisotropy ellipsoid of the deposit will be constructed. A case study of an uranium deposit is also analytically discussed for illustrating the application of this method.