A case study using indicator kriging - the Mount Morgan gold-copper deposit, Queensland / Тематическое исследование с использованием индикаторного кригинга - золото-медное месторождение Маунт Морган, Квинсленд

In August 1882, the Morgan brothers recognised a mineral deposit, now known as the Mount Morgan Gold-Copper Deposit. The final production figures for the mine were 250 tonnes of gold and 360,000 tonnes of copper from 50 million tonnes of ore, making the average grades 4.99g/t gold and 0.72% copper.
A three dimensional grade model was made of the pre-mined gold distribution within the Main Pipe mineralisation between the Slide Fault (to the west) and the Andesite Dyke (to the east), and bound to the south by the South Dyke.
Indicator kriging provided a method for estimating the grade in the strongly skewed gold distribution, without the problems of smearing of the high grades as seen in linear techniques. The application of indicator kriging using grade thresholds based on the declustered sample decile values was shown to be a poor application of indicator kriging, but was greatly improved by modifying grade thresholds above the median so that the amount of contained metal was evenly distributed between these classes.
The pre-mined resource estimate for this portion of the Main Pipe mineralisation using a 2g/t lower selection limit was 3,526,800 tonnes  with an average grade of 11.98g/t, equivalent to 42.25 tonnes gold.  <...>