Geostatistical ore reserve estimation at the Lac Knife graphite deposit, Esmanville Township, Quebec

CIM Bulletin, Vol. 84, No. 951, 1991

Marc Lavigne, Roche Ltd., Consulting Group, Sainte-Foy, Quebec

The Lac Knife graphite deposit was estimated, as part of a feasibility study, using a geostatistical ore reserve estimation method: ordinary kriging. Based on the geology and its interpretation, the results of a variogram study, and the statistical parameters of the grade distribution of the core samples and the composites through the mineralization, the deposit was divided into three separate zones (west, centre and east), and each of these zones was then analyzed and kriged independently. The geological ore reserve estimation results of ordinary kriging are compared to the results of a conventional method (sections) used previously. The two methods gave almost similar reserve figures. The conventional method provided a + 2% estimation for tonnage and +10% for grade because it ignored the spatial relation between sections and samples, and ordinary kriging gave a more accurate longitudinal definition of the deposit. Finally, the paper concludes with the advantages of proceeding with ordinary kriging, namely: higher flexibility (change of cut-off grade), better deposit resolution and enhanced selectivity for the design of the open pit.

Mots Clés: Geostatistics, Ore reserve estimation, Lac Knife deposit, Graphite deposits.