Akoko North - Resource Statement and Parameters
A Mineral Resource estimate for the Akoko North Gold Deposit was completed during March 2009 by Runge Limited for Castle Minerals Limited.The deposit is located 25km south of the town of Tarkwa in Ghana, West Africa.
The deposit is hosted within metasediments and metavolcanics. The mineralised zones are flat lying with a slight plunge to the north. The zones vary in thickness from 3m to 20m with an average of approximately 10m. Two main zones have been delineated with individual strike lengths of up to 600m. The mineralised zones have an east west extent of 20m to 50m. Mineralisation occurs in both the weathered and primary zones, with no clear change in tonnes or grade distribution. Elevated Au is often associated with quartz veining but shows no obvious lithological constraint.
The resource estimate complies with recommendations in the Australasian Code for Reporting of Mineral Resources and Ore Reserves prepared in 2004 by the Joint Ore Reserves Committee (JORC), therefore it is suitable for public reporting. The Runge Mineral Resource is summarised in the Table below.
| Material Type | Indicated | Inferred | Total | ||||
|---|---|---|---|---|---|---|---|
| Tonnes (t) | Au (g/t) | Tonnes (t) | Au (g/t) | Tonnes (t) | Au (g/t) | Au (ounces) | |
| Laterite | 300 | 2.1 | 300 | 2.1 | 20 | ||
| Oxide | 332,900 | 1.8 | 545,700 | 1.6 | 878,600 | 1.7 | 47,400 |
| Transitional | 24,000 | 1.5 | 121,000 | 1.7 | 145,000 | 1.7 | 7,900 |
| Fresh | 700 | 1.7 | 409,000 | 1.6 | 410,000 | 1.6 | 20,800 |
| Total | 358,000 | 1.8 | 1,076,000 | 1.6 | 1,434,000 | 1.7 | 76,100 |
The resource estimate was completed using the following parameters:
- The resource has a 1,000m lateral extent from 559,500mN to 560,500mN. The vertical extent of the resource is 80m from surface at 115mRL to 35mRL.
- 22 surface RC holes were used in the resource estimate for a total of 1,695m of drilling. Drilling density varies from 40m to 200m section spacings with 20m to 40m hole spacings over the deposit. The majority of holes are orientated at 50° to the east.
- A site visit was undertaken by Runge in March 2009.
- The RC sampling procedures were reviewed by Runge and are considered to be of industry standard.
- Samples were collected at 1m intervals via a riffle splitter at the time of drilling. These were used to prepare 5m composites which were submitted to the laboratory. If the 5m composite returned an assay greater than 0.1g/t Au, the individual 1m samples in the interval were assayed. The 1m riffle splits were samples prior to composite sampling.
- Samples were sent to Transworld laboratory in Tarkwa, Ghana for analysis. Au was assayed by 50g Fire Assay with an atomic absorption spectrometry (AAS) finish.
- Quality control samples were collected on a regular basis and the results have been reviewed by Runge. No bias is evident.
- Drillhole collars were located in UTM WGS84 Zone 30N coordinates by Coffey Mining using a DGPS system accurate to 10mm.
- The majority of drillholes have been downhole surveyed at 30m intervals using a single shot down hole camera.
- Wireframes were constructed using cross sectional interpretations based on a nominal 0.5g/t Au cut-off grade.
- Samples within the wireframes were composited to even 1.0m intervals. A 15g/t Au high grade cut was determined by statistical analysis and applied to the 1m composite values. A 10g/t Au cut was applied to one specific drill hole due to the extreme effect it produced in the grade interpolation.
- A Surpac block model was used for the estimate with a block size of 20m NS by 10m EW by 5m vertical with sub-cells of 10m by 5m by 2.5m.
- Inverse Distance Squared (ID²) was used for grade interpolation with an oriented search ellipse based on individual lode geometry. A first pass radius of 80m was used with a second pass radius of 200m. A third and final pass with a search radius of 250m was used to fill all remaining unestimated blocks. Greater than 93% of the blocks were filled in the first two passes. An 'ellipsoid' search method was used.
- No bulk density test work has been completed. However a bulk density of 2.0t/m³ was applied to the laterite, 2.1t/m³ to the oxide, 2.4t/m³ the transitional and 2.7t/m³ to the fresh material. These values were recommended by Castle with reference to similar style deposits in the area.
- The portion of the resource defined by 20m by 40m spaced drilling has been classified as Indicated Mineral Resource due to the demonstrated continuity of the mineralisation. The remainder of the deposit has been drilled on approximately 200m section spacings and has been classified as Inferred Mineral Resource.
Akoko South - Resource Statement and Parameters
| Measured | Indicated | Inferred | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Tonnes (t) | Au (g/t) | Au (ounces) | Tonnes (t) | Au (g/t) | Au (ounces) | Tonnes (t) | Au (g/t) | Au (ounces) | |
| Total | 610,300 | 1.3 | 25,900 | ||||||
The Akoko South resource estimate was completed using the following parameters:
- The resource has a 320m strike extent from 547,360mN to 547,680mN. The vertical extent of the resource is 142m from surface at 97mRL to -45mRL.
- Of the 45 RC drill holes in the database, 11 were used in the resource estimate for a total of 1,139m of drilling. Drilling density varied from 50m by 30m to 40m and 100m by 30m over the deposit. Drill holes are orientated at between 46° and 50° to the west (UTM grid), with the exception of AKRC034 which was drilled at 52° to the east.
- A site visit was undertaken by Runge in March 2009.
- The RC sampling procedures were reviewed by Runge and are considered to be of industry standard.
- Bulk samples were collected at 1m intervals below a free standing cyclone in large plastic retention bags. The 1m bulk samples were split using a riffle splitter at the time of drilling and then stored off site. Five metre composite 'spear' samples were prepared and submitted to the laboratory. If the 5m composite returned an assay greater than 0.1g/t Au, the individual 1m samples in the interval were assayed.
- Samples were sent to Transworld Laboratory in Tarkwa, Ghana for analysis. Samples were prepared by drying, crushing to -6mm and then pulverising to <75 microns (-200 mesh). Analysis for Au was by 50g Fire Assay with an atomic absorption spectrometry (AAS) finish.
- Quality control samples were collected on a regular basis and the results have been reviewed by Runge and are considered to be satisfactory.
- Drillhole collars have been surveyed by Coffey Mining (Coffey) using a Sokkia Stratus DGPS to an accuracy of 10mm.
- Down hole surveys were completed using a single shot Eastman camera.
- Wireframes were constructed using cross sectional interpretations based on a nominal 0.5g/t Au cut-off grade. Interpretations were based on those supplied in hard copy form by Castle.
- Samples within the wireframes were composited to even 1.0m intervals. A 20g/t Au high grade cut was determined by statistical analysis and applied to the 1m composite values.
- A Surpac block model was used for the estimate with a block size of 25m NS by 10m EW by 10m vertical with sub-cells of 12.5m by 2.5m by 2.5m.
- Inverse Distance (ID²) interpolation was used for grade interpolation with the search ellipse orientated to match the lode geometry. A first pass radius of 50m was used with a second pass radius of 70m. This was increased to 100m for the third pass to fill all remaining un-estimated blocks. Greater than 99% of blocks were filled in the first two passes.
- No bulk density test work has been completed. A bulk density value of 2.0t/m³ was assigned to the oxide material, 2.4t/m³ to the transitional material, and 2.7t/m³ assigned to the fresh material. These values were supplied by Castle and are considered reasonable for this style of mineralisation.
- The Mineral Resource was classified as Inferred Mineral Resource due to the uncertainty of structure and grade continuity.
Updated July 2009