Simple alternative to disjunctive kriging

• Main Authors: I Clark, Ph.D M Sc, D.I C C Eng, F S S, F I M A, M I M M
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Cornish; Fuller; Greenland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1054.7135; http://www.kriging.com/publications/IMM1981.pdf

Synopsis The regression effect in ore-reserve estimation has been identified, described and quantified in vein and reef deposits for more than twenty years. Its importance in 'three-dimensional' deposits -whether underground or open-pit --has been recognized under the alternate guise of the geostatistical volume-variance relationship. The Fontainebleau school has developed the technique of disjunctive kriging to combat the regression-volume-variance effect, but this is not yet widely available (or understood) in a form in which the ordinary user could apply it. A new and simpler approach to this problem is proposed, its development on a Cornish tin vein is briefly described and a fuller case study of its application to part of a three-dimensional uranium deposit in South Greenland is given. There are many possible sources for the difference between an ore-reserve estimate and the actual amount of ore in a stope or mining block, some of which present insurmountable problems in that they reflect the limited amount of sampling available compared with the large volume of ground to be estimated. They also, often, reflect the peripheral nature of the sampling and/or the erratic nature of the mineral that is sampled. Many attempts have been made to minimize the errors incurred in estimation, and the current consensus of opinion seems to have focused on the weighted-average type of estimator. Each sample is given a weight in accordance with its geometrical position in relation to the volume that is to be estimated. The weights may be decided by one of several methods: simple averaging, inverse distance and related operators or kriging. A weighted average or linear type of estimator has many advantages in practice: it is easy to compute and intuitively pleasing, and, if the user can derive a semivariogram for the deposit, the standard error of such an estimate may be evaluated without difficulty. Unfortunately, there is one major drawback in the use of a linear combination of sample values to estimate the average value ...