Now we have modeled an ore zone for you deposit. We wish carry out some statistical analysis on the data to determine sample populations and to then use the composited data to estimate the block model
1. Create a 3DM for each ore zone to be modelled.
This is usually a grade envelope. Use a different object number for each ore envelope.
2. Add a new interval table to your drillhole database.
I usually call the table 'intersect' and create a new character field called 'flag'. This table will be used to store drill hole intercepts that pass through the 3DM ore envelopes.
Go to Database, Administration, Create Table and fill out the forms as shown below.
3. Recall the 3DM into Graphics.
4. On the Database Menubar, Go to Analysis, DrillHole 3DM intersection
Apply through the query constraints
Fill out the form as shown below. At the very top of the form is an object pick list. Surpac will list all objects sitting in the active layer. You will have to do each object separately if there are more than one.
Any drill holes that pass through object three will be written to the 'intersect' table.
A new layer will also be created to visually show intercepts that pass through the 3DM. (shown below). It is not necessary to save this information. It can be used as a graphics check to ensure an intercept has been generated for all drillholes passing through the 3DM.
We now have flagged the grade intervals we wish to composite for statistical analysis, compositing and block model filling.
COMPOSITING
Several different ways to composite:
• Composite by grade
Produces bulked samples of different sample lengths based on width and grade constraints.
• Composite by geology
Produces composited samples of possibly different sample lengths based on geological constraints.
• Composite by elevation
Produces composited samples of equal length based on elevation restrictions.
• Composite downhole
Produces composited samples of equal length down a set of drill holes.
• Composite From End Of Hole
Create sample composites by searching up from the end of the hole and maximising one criteria while minimising a second criteria.
Of these compositing methods, only Composite by elevation and Composite downhole will produce composited samples of equal length suitable for use in statistical and geostatistical studies.
BENCH ELEVATIONS
This function creates one or more string files which contain elevation composites of sample data.
It can be weighted by length alone or by other fields in the table containing the sample data and can be used to weight by specific gravity or recovery.
Drill Holes are processed as described below:
All samples, or fractions of samples, of a drill hole which are within the nominated elevations for the composite, are reduced to a single point value. This value has the length weighted average of all samples which intersected the elevation range of interest. If the total vertical length of the samples as a percentage of the vertical height of the elevation bounds of the composite is less than a defined threshold percentage then the hole will be ignored. The reason for this is to give you some control over whether drill holes which only partially intersect the elevation composite are included or excluded from the final result.
a. Enter a file name
b. Enter the elevation range that you wish to composite
c. Define the elevation extent and type
The Type of extent can be either:
• -, to composite samples for the required extent below the nominal elevation
• +, to composite samples for the required extent above the nominal elevation
• +-, to composite samples for the required extent above and below the nominal elevation.
In this example an elevation range of 280, 300, 20 was specified with an extent of 10 and a type of `+-'.
Note: If you choose the +- method you should use an extent which is equal to half the spacing between the required composite elevations since the extent is applied both below and above the nominal elevation.
d. Define the output class range to determine to colour the string by grade range for greater impact
e. enter the minimum acceptable % of interval
If the total vertical length of the samples for a drill hole when expressed as a percentage of the vertical height of the elevation bounds of the composite, is equal to or greater than this threshold percentage then a composite value for the drill hole will be saved.
f. Threshold dip for channels
Holes which are within this angular tolerance of the horizontal are treated as channel samples, and one composite is extracted per discrete sample from the hole. Note: These composites may not be representative of the same length sample as composites from other, more vertical holes.
g. Dilute negative samples
In certain conditions, sample values for some elements may be missing. If this occurs special sentinel values are usually stored to indicate the absence of meaningful sample data. Generally negative values are stored to indicate the absence of data. There are two ways in which this absence of data may be treated:
Y= the sample will take on an assumed value of 0 (zero) this has the effect of reducing or diluting the final averages.
N= the sample will be ignored completely and it will have no effect on the final result.
Optional weighting fields - Field Name, Default
Typically, additional weighting fields used would be specific gravity and/or recovery. A maximum of 5 additional weighting fields may be used. Enter the field name/s which are to be used to provide the additional weighting criteria for the creation of the composite intervals.
Select the field that you wish to composite
DOWNHOLE COMPOSITING
a) Go to Composite, Downhole and fill out the form as shown.
Apply the form to continue.
Apply the form to continue
b. Recall the composite string file into graphics and view the results.
COMPOSITING DOWNHOLE CONSTRAINED BY INTERCEPT TABLE
a. Go to Composite, Downhole and fill out the form as shown. Make sure that 'Multiple Zones' has been selected on the form.
Apply the form to continue.
6. Because 'Multiple Zone's was chosen. Surpac will show the following form.
This is where we use the flagged intercepts created and stored in the 'Intersect' Table. Surpac will now composite samples that fall inside the intervals stored in this table.
b. Recall the composite string file into graphics and view the results.
To display the strings as markers, select from the display menu, strings and points
Display shows 1m composite string files inside the 3DM. Note the string 2 are the composites which did not meet the criteria.
c.. The Intersect table can be deleted from the drill hole database when finished as it is a sub-set of primary data.
Compositing Graphical
I. Create a Graphical Compositing II. Create a bench composite III. Create a downhole composite IV. Create a composite of interval data
I. Graphical Compositing 1. Composite >Setup options
The dilute option means that if the box is ticked any negative values or missing samples will be classed as zero and will therefore dilute any composite you create. If it is not ticked the negative value or missing sample will be ignored and not effect the composite.
This will display the averaged sample value 1 unit high, as a thick default trace terminated at each end by diamond shaped markers.
Composite code labels.
This will display the code labels on the left hand side of the drillhole trace, 1 unit high. The code is a character value suitable for storing in a database table representing an interval.
Composite > Create
Select the first composite point
Select the second composite point
Now shows the completed composite on the drillhole trace in blue – change the alignment and sizes if you wish
Change the size and alignment of the composite value so that it is visible.
Setup options .
Change the label position and alignment as shown below.
View the calculated grade and the exact depth to and depth.
Composite >Edit,
Select the composite
You can also edit the depths at this point should you wish. You can also edit the created composite in two other ways.
1. Composite | Adjust Length and ‘Select and drag an end point’ As you move this it also changes the calculated composite
2. Composite | Move and ‘Select and drag an end point’ the composite length does not change. The the calculated grade changes dynamically.
Exercise.
Create composites of high grade for the entire cross section.
To delete a composite left click on the Delete One composite icon , then left click on the composite that you wish to delete.
Creating a Composite Report
Using the previously created high grade areas we are going to generate a simple report for the cross section we have been working on.
or use the Report Composites Icon
The Group by Composite code will group all the HG_ORE code composites together, should you have also done some composites for low grade ore, previously in the exercise above these would also have been presented in the report
OPTIONAL EXERCISE
Grade Control Activity
Grade control drilling can also be interpreted in section, then the ore zones sliced in plan to produce flitch bars, these, together with a bench composite file can be re-interpreted in plan and then a grade assigned to the polygon to form a mining bench plan.
1. Display the drillholes and then section, interpreting each ore zone and saving to a separate file. A good naming convention is to ensure that the suffix of the file contains the section name, ie sec7200.str
2. Save all the section into one file. An easy way to do this is to select
FILE | OPEN and nominate the ore sections and the range, don’t forget to specify the
“append” which will place it all in one layer. Now that all the files are in the same layer, save the files, creating a new file name.
3. Ensure that all the ore polygons are clockwise and closed, with no duplicate points. Use the edit layer clean function to check for duplicate points and closure, the Identify Segment to check for string direction or the file tools | string summary to report the string directions within the file.
4. The ore zones where digitized in “real world co-ordinates”. To do any further calculations on this file, we need to flip it into sectional co-ordinates. This can be done easily using the edit | layer | maths function, to convert the Y field to the Z field, and the Z field to the Y field. The diagram below shows the sections as digitized in real world co-ordinates.
This is shown with a 3D grid over the file, below is the file in plan view
And section view
Using the layer maths function, complete the form as shown below:
Now the file in plan view is shown below. Compare this with the plan view screen capture taken above.
This is in section view.
The result of swapping the Y and Z fields is that the Y field (which was the northing) has now become the elevation, and the Z field (which was the rl) has now become the northing.
5. Create flitch bars
Once the ore section files have been converted to sectional co-ordinates and are cleaned, we can slice them in plan to obtain flitch bars to indicate where the ore lies in section. This can help us when we do our interpretation in plan, as it indicates where the ore zone lies.
To do this, select:
FILE TOOLS | SLICES THROUGH SECTIONS
6. Open the corresponding flitch bar file and bench composite file, we now have all the details on screen to begin to digitize in plan view.
7. Create ore blocks in plan view
a. Create a new layer and name it bench110
b. Set the digitizer properties to Z= 110 (or the rl required)
c. Digitise the oreblocks in plan view – saving the file as orebench110.str
8. To calculate the grade of the bench polygon, select FILE TOOLS | CALCULATE GRADE IN POLYGONS
This outputs the grade results to the message window and also creates a new file ore_blocks110.str. View this file in graphics to validate the ore grade.
VERTICAL SECTIONS FOR PLOTTING
The output from VERTICAL SECTIONS FOR PLOTTING is a series of string files containing the selected information for holes that match the hole selection criteria. There will be one string file for each section you have selected, with a location name that you have specified and an ID number equal to each section value. The structure of each string file is such that you can set up permanent map definitions in the PLOTTING menu which refer to the specific string numbers in which the selected information is stored. A summary of the string numbers output for each string file is given below:
String Description
1 Hole trace for holes entirely within extraction limits.
2 Hole trace for holes which start outside the extraction limits, but finish inside the extraction limits.
3 Hole trace for holes which start inside the extraction limits but finish outside the extraction limits.
4 Hole trace for holes that start and finish outside the extraction limits.
5 Top, bottom and down hole survey depths with survey data stored in the D fields.
6 The point at which the hole trace crosses the extraction plane.
11 The first interval sample grade range string, for the first sample table, with different elements stored in the D fields in the order in which they were selected (second table = 111, third = 211 etc).
12 The second and subsequent interval sample grade range strings, for the first sample table with different elements stored in the D fields in the order in which they were selected ( second table = 112, third = 212 etc).
21 The interval sample bar graph strings for the first selected element (or the first sample table), with the grade range in the D field (second table = 121, third = 221 etc).
22 The interval sample bar graph strings for the second and subsequent selected elements, for the first sample table with the grade range in the D field (second table = 122, third = 222 etc).
31 The interval bulked sample string for the first selected element, for the first sample table (second table = 131, third = 231 etc)
32 The interval bulked assay strings for the second and subsequent selected elements, for the first sample table (second table = 132, third = 232 etc).
41 The first point sample grade range string with different elements stored in the D fields for the first sample table, in the order in which they were selected (second table = 141, third
= 241 etc).
42 The second and subsequent interval sample grade range strings with different elements stored in the D fields for the first sample table in the order in which they were selected (second table = 142, third = 242 etc).
51 The line graph string for the first selected element, in the order in which they were selected (second table = 151, third = 251 etc).
52 The line graph string for the second and subsequent selected elements, in the order in which they were selected (second table = 152, third = 252 etc).
70 The literal geology string for the first sample table with the different geology fields stored in the D fields in the order in which they were selected (second table = 170, third = 270 etc).
71 The symbolic geology box strings for each geology field that has been selected with the literal geology codes in the D field, in the order in which they were selected (second table
= 171, third = 271 etc).
81 -
90 Geology trace for each geology field for the drill hole display module.
Strings 1 to 4 contain the drill hole trace strings for all of the holes extracted for plotting. Only the portion of the hole which lies within the extraction limits is extracted, so that special plot entities can be used to correctly display those holes which enter or leave the extraction limits.
The number of points defining the drill hole trace is determined by the answer to the question Downhole datapoint interval given in the EXTRACT SECTIONS FOR PLOTTING form. If you entered a value for Interval for plotting depths in the same form, the downhole depths will be stored in the D field of the drill hole trace string.
String 5 contains at least two points for each drill hole that has met the selection criteria. These points are for the top of the hole or the position where the hole enters the extraction limits, and the bottom of the hole or the position where the hole leaves the extraction limits. Each point in this string will have the following information stored in the D fields:
D1 hole_id D2 depth D3 dip D4 azimuth
String 6 will contain one point for each drill hole that intersects the section plane. If a drill hole does not intersect the section plane, such as a vertical drill hole, then no point will be stored for that hole.
Strings 11 to 20 will contain interval assay data for the selected elements, with each string representing a different grade range. If you answered `Y' to the prompt Process each element separately in the EXTRACT SECTIONS FOR PLOTTING form, then String 11 will contain all the values for each selected element in the first grade range for each individual element, String 12 will contain all the values for each selected element in the second grade range for each individual element, and so on. If you answered `N' to the prompt Process each element separately in the EXTRACT SECTIONS FOR PLOTTING form, then String 11 will contain the values for each selected element in the first grade range of the first selected element. The second and
subsequent selected elements for the samples in this string will be stored in this string regardless of their own value. String 12 will contain the values for each selected element in the second grade range of the first selected element, and so on. The actual data point stored for each of these strings represents the end point of the selected sample.
Strings 21 to 30 will contain bar graphs for selected elements, with one string number used for each selected element. These bar graph strings are closed segment boxes with the grade range number for each box stored in the D field so that fill entities can be applied when using the plotting module.
Strings 31 to 40 will contain the bulked sample data with one string number for each selected element. The bulked grades and lengths are stored in the D field at the point at the end of the bulked interval in the form `10m @ 25'.
Strings 41 to 50 will contain point sample data for the selected elements, with each string representing a different grade range. If you answered `Y' to the prompt Process each element separately in the EXTRACT SECTIONS FOR PLOTTING form, then String 41 will contain all the values for each selected element in the first grade range for each individual element, String 42 will contain all the values for each selected element in the second grade range for each individual element, and so on. If you answered `N' to the prompt Process each
element separately in the EXTRACT SECTIONS FOR PLOTTING form, then String 41 will
element separately in the EXTRACT SECTIONS FOR PLOTTING form, then String 41 will