Edit Vein Model Samples

The following information relates to the vein-from-samples and surface-from-samples commands.

The Create Vein Surface task is a focussed tool for the calculation of hanging wall (HW) and/or footwall (FW) surfaces that represent vein or vein-like lodes. Similarly, the Create Contact Surface task is used to generate contact surfaces between groups of contiguous categorical values.

This topic explains how the vein-from-samples sample editing commands let you reverse samples, and ignore the sample start and/or end positions.

Note: A Datamine eLearning course is available that covers functions described in this topic. Contact your local Datamine office for more details.

The vein-from-samples command assesses the overall orientation of an implied structure and will assign HW and FW points accordingly. This assessment involves determining which side of the trend surface a point lies, with the assumption being that all hanging wall points will be on one side and all foot wall points on the other, or pinching out will occur. In cases where the general direction of drilling is similar, the default assignment is typically acceptable.

However, in other cases (such as deeply dipping or vertical lodes, or where a structure has multiple implied anisotropic trends), there is an increased tendency for drillholes to intercept the trend surface from opposite sides and directions, meaning there is no consistent assignment of hanging wall and foot wall points. This poses a challenge to implicit modelling routines (but not ours).

Consider the example below where the trend surface is formed by holes in different alignments. The implied surface is vertical and the dip of hole descent varies from 70 to 120 degrees. Constructing a surface with the default point assignment will result in excessive pinching out as the hanging wall and footwall surfaces will become inverted in several places:

Where the underlying structure (based on the presence of drillholes in the vicinity) strongly implies a steeply-dipping vein, it makes sense to reverse samples in this case and if the general trend is for holes to penetrate the structure from opposing sides, the Auto Reverse All option could be useful as it will determine the mean plane of the intervals (near to vertical) and apply hanging wall and foot wall assignments appropriately.

Reversing sample positions allows you to:

Swap the hanging wall and foot wall positions - this results in a full inversion of the interval.
Convert the drillhole into a double-hanging-wall or double-foot-wall interval. This would be useful where a hole is aligned so that it intercepts the lode hanging wall or foot wall in two places e.g.:

There are two options available to you to resolve this situation:

Auto Reverse All samples, which instructs Studio RM to create a trend plane through all sample intervals and determine how intervals align in relation to the normal of this plane, automatically reversing them if their direction is significantly different from that expected. For the majority of data, this step will force a distinct hanging wall and foot wall arrangement that closely follows the structure that is intuitively expected.
Manually reverse samples. This is useful where a relatively small number of samples show a severe direction change from the trend of the others. This could be a result of selective underdrilling, data error or a change in the anisotropy of the lode, for example. If you wish to create double-hanging-wall or double-foot-wall intervals, samples must be prepared manually.

Manually reversing samples is done using Pick Samples to select the positive drillhole interval you wish to manipulate. Once highlighted you can:

Enable or disable a hangingwall (From) or footwall (To) point by enabling or disabling Use. This will either display or hide the red/green point indicator on screen. Sample positions that are disabled are not used in hanging wall or foot wall generation. You need to Apply your changes.
Set the hanging wall or foot wall point to be reversed. Selecting either the hanging wall or the foot wall and enabling Reversed results in a double-hanging-wall or double-foot-wall interval. If you reverse both hanging wall and foot wall, the default interval orientations are fully reversed and you have swapped their positions.

You need to Apply your changes.

Both functions require at least one positive sample interval to be selected. If multiple intervals are selected, Use and Reversed settings are applied to all intervals.