Introduction
The Akoko Project comprises two granted Prospecting Licence located ~10 km east of Adamus Resources’ Salman gold project and 30km south of Tarkwa. Adamus Resources has reported a Reserve for its Southern Ashanti Gold Project of 16.54MT @ 2.01 g/t gold for 1.068Moz.
The Akoko Prospecting Licence was granted in early 2007. During 2007 soil sampling was completed over the south west corner of the Licence adjacent to the Avrebo soil anomaly of Adamus Resources. This work reported a very strong soil anomaly, with an initial RC drilling program completed in October 2007 producing positive results. Further exploration during 2008 has produced further encouraging results.
Interpretation of aeromagnetic data suggests that the Avrebo soil anomaly will extend north along the western margin of a granite body that is crosscut by north east trending structures. The intersection of these NE structures, the granite contact and the interpreted northern extension of the Avrebo soil anomaly represents an excellent gold target.
Project Geology
The area covers part of the southwest portion of the Ashanti Belt within a broad succession of Birimian meta-volcanic and meta-sedimentary rocks, immediately south of the Tarkwaian sedimentary rocks and north of the large Prince’s Town Dixcove suite granitoid complex. The proposed licence area extends over the Prince’s Town granitoid complex and extends westward to cover its western contact with the meta-volcanic rocks.
The Birimian succession is dominated by meta-volcanic and meta-sedimentary rocks. Mafic sills and dykes are indicated on aeromagnetic images. The Prince’s Town granitoid complex has been mapped as mainly tonalite, however towards the west and southwest of Akoko, higher radiometric potassium signatures suggest a more K-feldspar rich igneous phase.
The structural geology in the area is poorly understood. A north-northeast striking regional shear zone has been interpreted to extend between Simpa and Akoko, and then northwards to join with a series of north-northeast striking structures that become the Damang fault.
Intense weathering has resulted in formation of a mature laterite profile that has been variously degraded to a latisol, and eroded and incised by recent drainages.
Exploration History
No significant modern exploration had been completed within the Akoko Project prior to Castle.
The area to the east of the Akoko Project area was probably a substantial gold producer in pre-colonial times. The Kanyankaw area, 9km east of the Akoko Project, was probably worked for a period by the Portuguese in the early 1600s. Shortly after the Gold Coast became an official British colony in the 1870s, numerous European groups prospected around many of the old artisanal mining sites. Numerous small adits and shafts were excavated. In the area immediately north and east of the Akoko Project are the prospects of Kanyankaw, Weew Bippo, Gogosu, Botokari, Kweku Esika, Appankram, Simpa, Adakaba, Cheriaman, Atinasi and Akoko. The latter five prospects are listed as they occur from north to south along an inferred north-northeast striking regional structure that possibly represents an extension of the Damang fault, responsible for mineralisation at Damang to the north.
The old Akoko mine is located only 1.5km north of the Akoko Project boundary and the Asheba/Atinasi prospects 3km further to the north. The Akoko mine is developed on a quartz vein. Exploration by Europeans probably started in the late 1890s and included very modest production in the period 1912 to 1928 of about 29,000oz derived from 35,600 tons of ore. Further exploration was carried out in the 1930s when the area was covered by numerous prospecting concessions. These included historic underground workings and nearby areas of extensive artisanal mining dating to pre-colonial times. At Akoko, one of the main shafts has been sunk to a depth of 229m. The veins at Akoko grade between 20g/t and 30g/t Au. The cost of mining the narrow veins was too high and the mine went bankrupt in 1926. Work in the 1930s did not apparently result in any new discoveries.
In the late 1980s, the area was held under a concession by Ghana Gold Pty Ltd who carried out soil sampling, along with the mapping and sampling of adits. The company later entered into joint venture agreement with the Glencar/Moydow group, which drilled eight holes into the Asheba Prospect to the north-northeast of Akoko. Between 2003 and 2005, Glencar drilled numerous RC holes into its Atinasi Prospect, just 2km northwest of Akoko. Results include 9m at 11.0g/t and 12m at 12.1g/t Au.
Exploration Results
The Akoko Prospecting Licence was granted in early 2007. During 2007 soil sampling was completed over the south west corner of the Licence adjacent to the Avrebo soil anomaly of Adamus Resources. This work reported a very strong soil anomaly, with an initial RC drilling program completed in October 2007 producing positive results including:
- 52m @ 1.16 g/t gold from surface
- 4m @ 4.09 g/t gold from 6m
- 20m @ 0.89 g/t gold from 57m
A further drill program was completed in January 2008 and reported further encouraging results, including:
- 35m @ 1.52 g/t gold from 5m (AKRC 41)
- 9m @ 14.9 g/t gold from 59m (AKRC 41)
- 7m @ 4.03 g/t gold from 47m (AKRC 39)
- 2m @ 12.1 g/t gold from 33m (AKRC 29)
- 16m @ 1.49 g/t gold from surface (AKRC 29)
- 72m @ 0.27 g/t gold from surface (AKRC 26),
includes 9m @ 1.02 g/t gold from 1m
In February 2008 soil sampling (200 x 50m spacing) confirmed a strong 3km long surface gold anomaly at Akoko North.
Within the larger anomaly is a higher tenor (+250ppb gold) continuous and well defined zone 1.5km long with a peak value of 1090ppb gold. The northern half of this zone contains numerous historic prospecting pits and shafts over a 600m x 75m area.
This high tenor zone is interpreted to overlie weathered pyritic basalt and is situated immediately west of a basalt/sediment contact, it is aligned north-south suggesting an underlying change to the regional north northeast strike.
This anomaly was drilled in March 2008 and intersected significant open ended shallow gold mineralisation over 1,000m of strike.
Five 200m-spaced drill fences were completed with significant gold mineralisation intersected on all lines. The mineralised zone is open in all directions.
- 2m @ 2.66 g/t gold from 15m (ANRC 04)
- 17m @ 2.29 g/t gold from 5m (ANRC 06)
- 18m @ 2.17 g/t gold from 3m (ANRC 07)
- 10m @ 1.11 g/t gold from 42m (ANRC 07)
- 11m @ 6.65 g/t gold from 50m (ANRC 08)
- 10m @ 1.50 g/t gold from 40m (ANRC 13)*
- 20m @ 0.80 g/t gold from 30m (ANRC 18)*
Twenty four new drill holes were completed in July 2008 with significant gold mineralisation intersected in most holes. The mineralised zone remains open along strike and at depth.
Intercepts of note include:
- 1m @ 84.5 g/t gold from 40m (ANRC 22)
- 18m @ 3.02 g/t gold from 7m (ANRC 32)
- 19m @ 2.02 g/t gold from 32m (ANRC 33)
- 19m @ 2.16 g/t gold from 6m (ANRC 37)
- 14m @ 2.26 g/t gold from 41m (ANRC 37)
- 13m @ 1.96 g/t gold from 22m (ANRC 43)
- 7m @ 7.11 g/t gold from 43m (ANRC 44)
- 11m @ 1.02 g/t gold from 3m (ANRC 28)
- 10m @ 1.15 g/t gold from 21m (ANRC 28)
- 13m @ 1.21 g/t gold from 36m (ANRC 28)
- 6m @ 2.29 g/t gold from 28m (ANRC 29)
Gold mineralisation occurs within near surface horizontal zones up to 150m wide. These zones are laterally continuous and can be traced along strike for at least one kilometre. The mineralised zones are typically hosted within weathered basalt and quartz veining is common.
Based on the results of the drilling programs a JORC Code compliant Resource Estimate was completed for Akoko North.
Runge Limited (Perth) undertook an independent resource estimate in March 2009 and estimated a total Indicated and Inferred Mineral Resource of 76,100 ounces.
| 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 |
A scoping study including open pit optimisation using Whittle4d software (optimised using US$800/oz gold price and incorporating mining dilution of 10% and mining recovery of 95%) captured 1.22mt @ 1.58g/t gold within a shallow open pit. The Whittle shell had a strip ratio of 3.8:1 and comprised 67% oxide mineralisation.
The US$800/ounce shell captures an Indicated and Inferred Resource Estimate totalling 1.22 million tonnes @ 1.58g/t gold containing 58,000 ounces.
Using a sales (revenue) price of US$950 per ounce and after allowing for an estimated toll milling fee, the optimisation generates a gross surplus of US$17 million ($A24 million).
The Akoko North deposit remains open in all directions and extensional, deeper and infill drilling is proposed.
![[some kind of table]](images/projects/akoko-table.gif)
Resource
Akoko North - Resource Statement and Parameters
A Mineral Resource estimate for the Akoko North Gold (Au) Deposit was completed during March 2009 by Runge Limited (Runge) for Castle Minerals Limited (Castle). 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