Concepts of Regionalised Variables and Variogram Modelling

Abstract

Usually, information about a geological phenomenon under study is sketchy or very limited. Therefore, we need a model to be able to draw valid inferences about mineralised zones that have not been sampled. In Chapter 4, we discussed models based on time series analysis (stochastic modelling) and applied the same to realistic situations. There are also methods based on trend surface analysis which is a regression method. Here a dependent variable, Z, is predicted, given the locational co-ordinates (x, y). The implicit assumption underlying these types of regression methods is that the surface under study can be represented, locally, by a fairly simple deterministic function such as a polynomial, plus a random error component. However, most geological variables display a considerable amount of short scale variation in addition to the large scale trends that can reasonably be described by deterministic functions. Therefore, a dichotomy into deterministic and random may not always be correct.