Republic of Turkey Figure 11-1
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DIAMOND DRILL SAMPLES
Almost all delineation drill holes are NQ size and the intersections have been sawed in half, with one half sent for analysis and the other retained for future uses. Sample intervals are variable, based on the geology and range from 0.1 m to a maximum of four metres (35% of samples are less than one metre in length and 61% are one metre to two metres in length).
The stope definition holes are BQ size and, following geological logging, the complete core is sent to the lab for analysis. The standard sample interval is two metres but can locally vary based on the geology of the hole. Geology staff carried out grade comparison between NQ and BQ core sizes and found that there are no indications of grade bias related to sample size.
UNMINERALIZED ZONES
Intervals which intersect unmineralized zones (such as dykes) are generally not sent for analysis. These are identified by the rock type codes in the database and are assigned default grades of zero.
MISSING SAMPLES
Intervals for which no core was recovered and no drill cuttings were collected are marked as “missing” in the database and have no effect on block grade estimates during interpolation.
UNDERGROUND CHANNEL SAMPLES
Underground channel samples were taken extensively in the mine up until 2001. They were then replaced with the stope definition drill hole since the latter improved the timing of the results for mining purposes and reduced sampling costs. The channel samples are retained in the database as they still contribute valuable information on active areas in the upper portions of the deposit.
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Underground channel samples are obtained following the completion of primary sill drifts. A channel is cut using a diamond saw on both the north and south walls of the drift, and the material is removed with a chisel and placed in sample bags. The wall is logged and the sample intervals (from and to a known point) are recorded in a similar fashion to diamond drill core processing. In the database, each wall which is channel sampled is treated like an individual drill hole.
Geology staff carried out a statistical comparison in 1999 between diamond drilling and channel sample data for a given volume of data including a relatively equal amount of sampling of each type. There were no indications of significant bias between the two data sets.
DEVELOPMENT SLUDGE SAMPLES
Development sludge samples are obtained using a small shovel and scooping a total of five to seven kilograms of drill cuttings that accumulate along the base of a face during the jumbo drilling of each round in the ore zone. Each sample represents approximately four metres of advance in the drift. In the database, each individual drift is presented as a drill hole located about the centerline of the drift. A statistical analysis carried out by geology staff indicates that the sludge sample data produce slightly lower grades than channel or drill hole samples over a given area. It has been concluded that this trend is due to the difference in selectivity in the sample sizes and the related dilution effects at a cut-off limit.
Sludge samples have been collected since the beginning of production, but, historically, this information has only been utilized for visually aiding the daily grade control activities. In 2001, this data was converted to digital format and testing began for ways to better utilize this information. It was found that it could improve the short-term forecasting of stope production. During interpolation, the effect of the sludge data is limited to primarily higher-level (measured) resources within a distance of 15 m from the sample location. The sludge sample has no effect on the longer-term resources/reserves in the model.
SAMPLE DISTRIBUTION
The distribution of samples by type, as of the end of 2004, is listed in Table 11-1. Core samples account for 57% of total samples in the database.
TABLE 11-1 SAMPLE DATABASE STATISTICS Inmet Mining Corporation – Çayeli Mine
Type Number of
Holes Metres Number of
Samples % Samples Delineation Drill Holes 660 83,283 28,174 51.4 Stope Definition Drill Holes 247 7,130 3,256 5.9
Channel Samples 644 14,527 15,582 28.4 Sludge Samples 846 28,975 7,834 14.3
Total 2,397 133,915 54,846 100
RPA considers the quantity of samples in the database that are used for grade estimation appropriate and sufficient.
BROKEN ORE SAMPLES
Broken ore from stopes and from stockpiles in surface ore bins are sampled on a continuous basis, one 10 kg sample for every 250 tonnes of ore. Stope samples are taken from every tenth 25-tonne truck. Stope samples are used for grade reconciliation.
Stockpile samples are used to report daily production of mill feed. Stockpile grades are not used for grade reconciliation.
Broken ore samples are taken by geology technicians or geologists. They are all collected by hand shovel.
There are no broken ore samples taken in development headings.
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RPA recommends conducting a more detailed study on broken ore sampling in order to see if sampling quantity is appropriate for grade reconciliation, or whether additional sampling is necessary. Maybe one sample per 250 tonnes is not enough.
DEVELOPMENT GRADE CONTROL
Grade control in development headings is based on:
x Visual estimates. Development faces are split in quadrants and the proportion of ore type (clastic, spec, stockwork) is estimated in each quadrant. Surface ore bin stockpiles become necessary when a bigger proportion of ore type is identified in the face.
x Sludge sample grades. Sludge samples are analyzed by X-ray Fluorescence (XRF) to provide rapid discrimination between ore and waste. Visually estimated grades and sludge sample grades are entered into the database to be compared by each of the geology technicians. Technicians are instructed about significant discrepancies between the visual estimates and sludge grades.