Simulating the Geometry of a Granite-Hosted Uranium Orebody

Abstract

The aim of this study was to simulate the geometry of uranium mineralisation in the Rossing deposit. As plurigaussian simulations have been successful in modelling the lithotypes in oil reservoirs (that is, for sedimentary sequences) we wanted to test whether this approach could also simulate intrusive rocks hosted in metasediments. The work has been carried out in two stages. In the first part (Skvortsova et al, 2000) we successfully simulated the overall structure of the deposit. The lithotypes were reproduced in the correct stratigraphic order and in the right quantities, and mineralisation that is concordant with the bedding planes was reproduced correctly. However we were unable to generate mineralised stringers that cut across the bedding planes. This paper shows how this can be done.

After reviewing the geology, the mining method and the available data, we give an overview of the plurigaussian simulation method. When applying this methodology, the key steps are:

• - choosing the reference marker to flatten the deposit

• - grouping the lithologies into lithotypes

• - computing the vertical proportion curves

• - choosing the lithotype rule

• - calculating the experimental indicators variograms and fitting a model to the underlying gaussian random functions

• - carrying out the gaussian simulation and truncating to obtain the lithotypes - returning the deposit to its initial position

We describe how these steps were applied to the Rossing data, emphasising the geologist’s input into the decision-making process. Several simulations were generated.