Ore-Thickness and Nickel Grade Resource Confidence at the Koniambo Nickel Laterite (A Conditional Simulation Voyage of Discovery)

Tropical weathering on the ridges of the Koniambo massif in New Caledonia has produced nickel mineralisation of variable thickness. Conditional simulation studies of nickel grade and ore-thickness (a proxy for ore tonnage) were used to quantify the resource risk and to generate constraining envelopes for resource classification.

Ore-thickness intercepts were created from vertical drilling and converted to 2D point data. Many drillholes that did not meet the selection criteria were included as barren, and these holes imposed a strong positive skewness on the data histograms. Indicator variography revealed that both grade and ore-thickness continuity is quasi-isotropic. One-hundred 2D sequential indicator conditional simulations were generated for each attribute on a 10 m by 10 m grid for the three deposit areas. This paper focuses on results from one area, the Centre sector.