Calculation method used:
The calculation used is the longitudinal sectional polygonal method. The polygons are determined on sections generally on a scale of 1:200 and the grade associated with the polygon comes from the drilling or from the development sample grade within the polygon. The geology has been interpreted in section prior to calculation of the reserves to obtain detailed knowledge of the sections. When two grades are available for a single block, an average is generally made. The extension of the polygons is limited to the middle point between two drilling points or to a limit of 10 m (33 ft) of a drilling point as described in the reserve categories.
Each polygon is reproduced in longitudinal sections for better control. The area of the polygons is determined manually in cases of regular polygons or with the Autocad software for irregular polygons. In sections, polygons are identified by numbers (level, zone, section, number) with the tonnage and diluted grade. All the data are transferred onto worksheets in order to do a summation of the blocks. The reserves are separated by zone, level and class, and then grouped by stope.
The information collected when interpreting the drilling core is kept in the Prolog software. Treatment of the information is done using the Tralog software and finalized using Autocad.
Due to the very high but irregular grade of the economic intersections, it is difficult to make a good inventory evaluation of all the mineralized veins. For the same reasons, it is difficult to make the evaluation of the grade of tension veins (e.g., Zone BF). Often, the evaluation is lower than the actual grade. The interpretation of geological structures from drill holes is difficult. There is a lack of uniformity and quality control in the mapping of the core.
The drilling is carried out from the hanging wall and must be perpendicular to the vein to facilitate the interpretation. In order to make the interpretation of the geological structures more precise, the drifts are mapped. This information, along with that obtained from the diamond drilling, increases the degree of geological trust. To assure good quality control of the core mapping, a standard procedure will be elaborated on and written.
Datamine software is used to assess the reserves.
The calculation method used is reciprocal of the squared distance.
The geometry of lenses 07, 08, 40 and 50 enables reserve assessment using the conventional section method; this method used for narrow-vein interpretation is recognized by the industry.
In some areas, the vein interpretation is difficult. Sometimes the main vein pinches, a secondary vein widens and could become the main one.
The test holes are drilled inside the stope in order to identify secondary veins. A detailed interpretation is done from the geological sections prior to mining.
The drilling data is processed with Prolog and Fonpro softwares. Afterwards, Datamine software is used for 3D modelling of the mineralized blocks.
Refer to the attached document for the interpretation procedure.
The estimate and the interpretation are produced according to the polygonal method on transversal sections. A scale of 1:250 is used for the sections.
In some cases, longitudinal sections are used to define the influence of surveys near the borders of the lens.
The influence of surveys is fixed to 10 m to 40 m (33 ft to 131 ft), according to the spacing of the drilling grid and the category of the reserves.
The estimated grades in drifts and in stopes are used when they are available. However, their influences remain the same as in the surveys.
It is pointed out that at Sleeping Giant mine, only conventional methods are used to quantify the mineralized inventory. The accuracy of the estimates is evaluated on the basis of experience and the production history of the mine and not from geostatistical calculations.
The drilling results are reported manually on the drilling sections. The information is processed with the conventional section method. The practice of this method for the calculation of reserves in narrow-type deposits is recognized in the industry.
The interpretation of the reserves is presently in transition from the manual to a computerized system. The software are: Prolog, Tralog and Promine.
The evaluation is done by level plan sections, polygons and some cross sections.
In the proven reserve, only the grade obtained by sampling the ore drift is used for grade estimation.
The interpretation method differs according to the confidence level of the ore reserve. Basically, the proven reserve calculations from actual mapping analysis are projected 10 m (33 ft) above existing mined stope, while probable reserves are based on diamond drill intersections 20 m (66 ft) apart.
DEEP COPPER ZONE (37, 38 and 39)
For Proven Mineral Reserves, the tonnes per vertical metre were calculated using the last completely mapped horizon and face samples for the sulphides mined to date. Actual amounts of planned waste, overbreak and development mineral percentages were included in the calculation. For Proven Mineral Reserve, this calculation is projected 10 m (33 ft) except in 39-1620 stope where it is projected 5.5 m (18 ft) to connect with the sill above and in 42-1620 where it is projected 12.9 m (42 ft) to the 39 sill.
All remaining Probable Reserves were calculated as follows: An envelope was drawn on the diamond drill sections which contained stringers of sufficient true width and grade to meet cut-off grade over a minimum mining width. The cumulative true width at the weighted grade was used to construct a polygon from the mid-point of the envelope on each diamond drill hole. This polygon was then projected halfway up and down the envelope dip, halfway to the adjacent sections, and converted to tons. Planned waste, waste (overbreak) dilution and development mineral amounts were then added.
The reserve estimates are calculated using the polygonal method on longitudinal sections.
For flat veins, cross sections every 10 m (32.8 ft) are used.
A thickness of 5 m (16.4 ft) on each side of a development heading is proven reserve.
The reserve estimates are done in conjunction with the geology and engineering departments. Resources (all categories) are generated each year by the geology department through extensive surface and underground exploration efforts. The engineering department then redistributes the appropriate portions of the resource to the proven and probable reserve categories. In addition to the proven and probable categories, a category named incremental reserves is used. The reserve blocks that fit in this category are those for which the grade is lower than the cut-off grade and higher than the incremental cut-off grade which is based only on the direct operating costs. It is common practice at McWatters to process such reserve blocks on an incremental basis in order to optimize mill throughput.
The reserve estimates are calculated using the polygonal method with longitudinal sections with PROMINE, a software program designed to incorporate diamond drill hole information as well as chip samples from underground workings. The final product is then handed over to the engineering department, where a mining method is assigned along with the corresponding dilution factor. On the basis of an economical study, the geological blocks are classified.
CRITERIA (CROSS SECTIONAL METHOD - MEDS)
Ore reserves in MEDS (Mineral Evaluation Development System) are developed from detailed vertical cross sections plotted at 15-m (50-ft) intervals. The lenses are connected to form a 3D block model. The 3D block model is then sliced at 3-m (10-ft) intervals in East-West, North-South and horizontal orientations producing numerous 3 m x 3 m x 3 m (10 ft x 10 ft x 10 ft) cubes within the model. Based on inverse distance cubed calculations between drill holes, the ore grades from the drill hole composites are applied to the cubes and the ore reserve is calculated.
The evaluation is done by cross-sectional or longitudinal polygonal reserve depending on the zone.
The cross-sectional polygon evaluation method is historically the standard reserve evaluation method at Golden Giant. It is used for wider, consistent ore zones which are defined by drilling and detailed interpretation on regular N(D) cross sections. This classical projection method produces good results at Golden Giant, largely because a consistent and detailed interpretation is required to begin.
The longitudinal polygonal evaluation method is a classical method for narrow ore. It is interactive and fast. A detailed ore interpretation on cross section must be completed beforehand to ensure consistent interpretation. It is generally used for ore that will be sill-developed. It is flexible and allows quick recalculation to new stope boundaries.
After development, the ore reserves are finalized, that is, located accurately in space by actual development. The ore area, top and bottom, establishes the localization. The grades and specific gravity (SG) are transferred from the polygonal reserve and finally, dilution is applied.
The cross-sectional polygon method is not very interactive - the changes in interpretation or location of infrastructure cause a lot of work to be redone. The longitudinal polygonal method is suitable for the global estimate but caution must be used for selective mining. This classical projection method produces good tonnage/grade estimates for narrow zones at Golden Giant, but it does not locate the ore zone accurately in space.
All calculations were made on longitudinal sections, scale of 2.5 cm = 15 m (1 in = 50 ft). For some blocks or stopes in the South zone, the interpretations were calculated on longitudinal sections, scale of 2.5 cm = 6 m (1 in = 20 ft). All distances with respect to the criteria were measured in the direction of the dip.
The polygon calculation method was used. The surfaces connected with the ore intersections were measured with a PLACOM KP-90N type digital planimeter with a measuring accuracy of ± 0.2%. Each surface was measured twice to obtain an average area. The polygons were built on a longitudinal projection. For the West, East and # 7 zones, the calculation of the surface was made with the Autocad 13 software.
The influential zone of a polygon was limited to the middle distance between two intersections or at a maximum distance of 45 m (150 ft) for the peripheral holes. Where applicable, the limit of the polygon set on the border of the mineralized zone was located following the geological interpretation done on cross sections.
The software used to compile the data is Surpac. Longitudinal polygonal evaluation method is used for reserve estimation.
Reserves were calculated using the standard polygonal method based on diamond drilling. Chip sample data, when available, were also utilized to supplement the database. All complete chip sample strings were combined in 20 m to 30 m (66 to 98 ft) long stoping blocks and composited into point values. Grades greater than 0.080 oz/ton were considered to be ore. The update mining grid was then inserted onto the long section, and areas for the different mining blocks were generated and weighted to reflect the direction of the vein. Standard dilution factors based on stoping width were applied to the ore blocks to produce a diluted reserve. Finally, all stoping blocks interpreted to be inaccessible were eliminated in order to produce a mineable, diluted reserve. The software used to compile data is Gemcom.
The majority of the Mineral Inventory at New Britannia Mine was appraised using the sectional reserve estimation technique.
The calculations are based on the interpreted ore outlines derived from diamond drill core and underground development drift chip sampling. The data are plotted on 1:40 scale cross sections at 7.6-m (25-ft) intervals using the Gemcom software.
Reserve and Resource blocks are calculated using 15-m (50-ft) intervals between block centres. Geological factors, such as structural and mineralogical controls, are assessed during the construction of the ore blocks. Ore grade intersections in adjacent drill holes are not connected to outline an ore block unless geological factors supported the assumption of geological continuity.
In areas where diamond drill spacing is greater than 15 m (50 ft), but geological continuity is supported, a 30-m (100-ft) interval between block centres may be used to calculate the mineral inventory blocks. On each sections, the areas are calculated for each interpreted ore block. A tonnage is determined by projecting the ore block areas along strike one half the distance to the next section (25 feet). Geological factor or existing mine workings occasionally limited the projected distance.
The average grade for each interpreted ore block is the average of its drill hole intersections weighted by true width across its area of influence. Where sill drifting has occurred, the weighted average for the two or three drift faces closest to the individual section line is combined to produce a grade for the sill at this point. It is then treated as a drill intercept. Use of a weighted average for the sill drifting only occurs where this data has been compiled prior to the start of reserve calculations. The area of influence is interpreted up and down dip halfway to the next data point, or the limit of the particular reserve classification.
In the main mine, reserve and resource blocks are designed from sill level to sill level based on the present mining plan. For the 1997 Reserves, the spacing between the sills was changed to a distance of 15 m (50 ft) vertical to account for the periodic flattening of the ore zones. With the exception of the Ruttan Zone below the 2656 Level, this spacing has been continued for the 1999 Reserves.
The Ruttan Zone had been changed to 12 m (40 ft) vertical spacing between sills. The vertical spacing was changed because of the apparent flattening of the orebody along portions of its strike length. The flattening is due in part to the 30-degree strike change of the zone between the 2456 and 3000 levels. Later, this apparent flattening was proven to be more of a strike change rather than a flattening of the zone. Subsequently, the 15-m (50-ft) vertical spacing between sills was reinstated in the Ruttan Zone.
Three grid systems cover the various zones in the main mine to allow for the sections to be perpendicular to the ore. The three grids are the Toots, Ruttan and Dick.
- The Toots grid is used only in the upper portions of the mine above the 1530 Level. Below the 1530 Level, this grid is no longer used as the Toots Zone pinches out.
- The Dick grid is also called the Main Mine grid and is oriented North-South. As indicated by the grid, the Dick Zone is primarily an east-west trending zone.
- The Ruttan grid is a Northwest-Southeast trending grid oriented 40 degrees east to north. Due to the 30-degree change in strike direction of the Ruttan Zone, the Ruttan grid becomes obsolete below the 3000 Level. Future documents (2000) will interpret the mineral inventory in the Ruttan Zone using the Main Mine (Dick) grid. The Ruttan grid is also used for the Hogg Zone interpretation. Below the 2010 Level in the Hogg Zone, the Hogg and Ruttan Zones have no waste wedge between them and constitute one zone. Below the 2300 Level, the Hogg Zone, for the purposes of the Ore reserves, no longer exists as it is combined with the Ruttan Zone.
In cases where insufficient geological data was available to create sections, resources were estimated by the polygonal method, plotted on a longitudinal section. Resources at the Birch Zone, as well as those of the Lower 3 Zone (500L to 1100L) were estimated by this method.