Indicator Variograms as an Aid for Geological Interpretation and Modeling of Ore Deposits

Mohammad Maleki,Nadia Mery,Xavier Emery

doi:10.3390/min7120241

Abstract

Geostatistics offers a set of methods for modeling, predicting, or simulating geological domains in space. In addition of being an input of some of these methods, indicator direct and cross-variograms convey valuable information on the geometry of the domain layouts and on their contact relationships, in particular, on the surface area of a domain boundary, on the surface area of the contact between two domains, on the propensity for a domain to be in contact with, or separated from, another domain, and on the minimum and maximum distances between points from two domains. Accordingly, the indicator variograms inferred from sparse sampling data can be used to determine whether or not an interpreted model of the subsurface is consistent with the sampling information. The previous concepts are illustrated through a case study corresponding to a porphyry copper deposit.

Highlights

Identifying and modeling rock type, mineralization and alteration domains in ore deposits has become a crucial step in the assessment of geological and geometallurgical regionalized variables, such as metal grades or metal recoveries, due to the controls that these domains often exert on the distribution of these variables [1,2,3,4,5].One issue for mining geologists and geometallurgists is to define the layout of each domain with the greatest possible accuracy, in order to minimize misclassifications
Another issue relates to the consistency between the interpreted domain layouts and the information obtained from sampling data, so as to determine whether or not the geological interpretation is a faithful representation of reality
Of particular interest are the spatial regularity of the domain layouts and the contact relationships between domains, as some domains may have a propensity to be or not to be in contact depending on the geological setting

Summary

Introduction

One issue for mining geologists and geometallurgists is to define the layout of each domain with the greatest possible accuracy, in order to minimize misclassifications (material predicted as belonging to a domain, but belonging to another one). Another issue relates to the consistency between the interpreted domain layouts and the information obtained from sampling data, so as to determine whether or not the geological interpretation is a faithful representation of reality. Of particular interest are the spatial regularity of the domain layouts and the contact relationships between domains, as some domains may have a propensity to be or not to be in contact depending on the geological setting. This paper focuses on alternative tools (namely, the indicator direct and cross-variograms) that are often disregarded in the geological modeling stage, they can be inferred from a set of sampling data

Methods

Results

Discussion

Conclusion