Make Block Model

This is one of the initial commands to begin using the block modeling features of Carlson. It uses similar grid logic, for location and resolution in the X and Y. It will take bed and subdivide it into vertical divisions. This can be applied to stratafied deposits, or ore based geology, where it is not stratafied, such as limestone or copper, gold and silver. In these ore type cases, the strata or bed name could be just rock, or limestone all the way down the hole. It would then look at just the quality being modeled as the variable. The program takes this interval, makes a roof and a floor and divides it up equally into the number of vertical divisions specified, or at an elevation "lift", where the top and bottom elevations are specified, and the block height calculated based on the number of divisions.

The first dialog brings up the Select Bed and Attribute screen. One bed name must be selected, and one or more attributes selected. If there are no Bed names in the drillholes, then select the Model By Strata Names box to use just Strata names.

The next screen, Make Block Model, is for dimension and modeling settings. The number of cells in the X and Y direction are shown at the top. The total number of cells in plan view is shown next. The block height is determined by the Number of Vertical Divisions and Vertical Position settings. There are two options to determine the Vertical Position. The first one is by Fixed Elevations. This will activate the Bottom Z and Top Z windows where the roof and floor for the block model are entered. The Follow Ore Model makes the top and bottom of the block model follow the top and bottom elevations of the bed being processed. The Use Fixed Elevations for Ore Model controls how the attributes are interpolated for the Fixed Elevations mode. When this option is on, the attributes are calculated at the fixed elevations. When this option is off, the attributes are calculated within the elevation range of the bed and then interpolated to fit within the fixed elevations. The Number of Vertical Divisions controls the number of block model data points between the top and bottom of the block model.

Make Block Model uses 3D Inverse Distance, 3D Kriging or Discrete as the modeling method to produce the block model of the quality values. The Prompt Each Attribute will allow for different methods for different grades in the block modeling. For example, Calcium can be modeled with Inversed Distance and Magnesium modeled with Kriging. It will prompt for each before writing the BLK file. The distance weight for the 3D inverse distance is the combination of the X-Y distance and the Z distance. This vertical factor is multiplied by the Z distance. So if there is no special correlation in the deposit for vertical, then the vertical factor should be set to 1. If there is some strata-like correlation based on deposit level, then this vertical factor should be set greater than 1, such as 10. Inverse Distance horizontal weighting factor, and ellipsoid is prompted for at the command line with: "Use inverse distance to which power [First/<Second>/Third/Other]?" and "Use elliptical inverse distance [Yes/<No>]?"

Discrete is a method to model parameters such as color. It will carry one color 1/2 way over to the next drillhole, then switch to the other color. This way, there is now blending of colors, if color1 is a 2 in one drillhole and color2 is a 4 in the next drillhole, it will not blend them to a "3" in the middle. It models 2, and then switches to 4 at the halfway point.

After the routine is finished calculating, it creates a *.BLK file. This file can be viewed in a text editor to see what it contains, as shown here. Basically, it shows the roof and floor, the quality attribute name and the file paths of each level of the block qualities.

Keyboard Command: BLKMODEL
Pull-down Menu Location: Block Model
Prerequisite: Drillholes with a bed name, and variable quality values that can be vertically modeled.