Geostatistical Modelling
Geological Modelling Considerations
- Definition of Geological/Grade Populations
- 3D Modelling Concepts
- Block Modelling Concepts
Definition of Geological/Grade Populations
The creation of three dimensional models of an orebody is essential for visualisation and presentation. Sectional and plan methods do not take into account whether or not the interpretation is geologically 'attainable', that is, can the outlines be joined together?
It is presumed that interpretation of geological and or grade boundaries is feasible, possible and attainable in that geological comprehension of the mineralisation is adequate to allow sensible interpretation. The style of the mineralisation will dictate the type of interpretation which is appropriate, that is, geological or grade boundaries or a combination of both. If it is not possible to define sensible geological and or grade constraints on the available data then grade interpolation methods may be used with caution for interpretation.
Constraining grade interpolation methods will set limits on ore volumes (tonnages). It is important to realise that unconstrained grade interpolation will create mineralisation to the limit of the interpolation parameters.
The basic requirements for modelling are to create a 3D solid shape of geology and or grade which will be used to:
- accurately and sensibly represent the accepted current geological interpretation of the mineralisation.
- flag the samples to be utilized for grade interpolation process.
- constrain the interpolation methodology to the volume and 3D shape of the geological interpretation.
3D Modelling Concepts
The purpose for which the model is to be used will impact on the concepts used for interpretation. In particular:
- open pit or underground mining methods
- the detail required for mine planning
- will the 3D model be used for block modelling or will it be used for presentation.
Either sectional, plan or a combination of these approaches can be used as the basis for creating 3D solid models. It is important to ensure that all sectional views through the solid model represent the geological interpretation accurately.
Block Modelling Concepts
When block modelling is being carried out the following points should be taken into consideration:
- What is the purpose of the model?
- What level of detail is required?
- How many variables are required in the block model to allow for evaluation?
- How will the model of the mineralisation be categorized in the block model?
- What priorities are to be assigned to individual solid shapes in the model?
- Do all the variables and triangulations in the model cover the model extent?
- Do the solid models properly identify and flags the samples to be used in the grade interpolation.
