Geostatistics in the presence of geological boundaries: Exploratory tools for contact analysis

Identification and categorization of geological, geotechnical, or geometallurgical domains is a common practice in the modeling of mineral deposits, in order to account for the controls exerted by categorical variables (ore type, rock type or facies) on the quantitative variables of interest. The definition of a suitable geostatistical model for spatial prediction or simulation is commonly based on a contact analysis, aimed at determining whether or not these quantitative variables are spatially continuous across the domain boundaries. In this paper, we present several tools such as cross-to-direct variogram ratios, cross-correlograms, pseudo cross-variograms and lagged scatter plots that are useful for such an analysis and discuss their strengths and weaknesses. The tools are illustrated with applications to synthetic case studies.