Soft and Hard Boundaries
Depending on the style of mineralisation at your project you may need to incorporate soft boundaries. A soft boundary occurs where there is a gradational geological contact between mineralised and un-mineralised zones, or between two mineralised zones, often found in porphyry or stockwork deposits.
A typical hard boundary occurs where there is a sharp geological contact between two zones, usually through some form of lithological or structural control. Hard boundaries are common in lode-style deposits.
Modelling soft boundaries
Armed with information about the contact you can choose to:
- Ignore the boundary altogether and incorporate all grades.
- Incorporate grades just outside the boundary by creating a diluted wireframe (Wireframe | Utilities | Resize) or by using carefully chosen data search parameters.
- Use filters to control which grades contribute to the domains either side of the boundary.
This approach is best for a highly gradational contact with a smooth grade transition that influences grades on both sides of the boundary.
Use this approach for somewhat sharper contacts with a more distinct grade transition that influences grades on both sides of the boundary.
This approach suits gradational contacts where adjoining domains may influence each other, or where the influence of an adjacent domain is one-directional.
Modelling hard boundaries
Modelling hard boundaries is straightforward. The strong control caused by a sharp geological contact usually means the grade values on either side of the boundary are independent of each other.
Not only does this make interpretation easier but it often makes the identification of statistical differences between the domains more robust. As a result, each domain can be modelled using only the grades within that domain’s boundary.