Introduction
Antubia is located approximately 370km west-northwest of Accra, in the Sefwi gold belt and is ~90km southwest of the 16Moz Ahafo gold mine operated by Newmont.
Project Geology
The Antubia project area is located within the Sefwi gold belt, ~90km southwest of the 16Moz Ahafo gold mine operated by Newmont. The Antubia area is dominated by Dixcove suite granitoids to the north and Birimian meta-volcanic and meta-sedimentary rocks to the south. A fairly uniform regolith profile is observed at Antubia, generally including a veneer of transported gravel or soil, overlying a residual sequence of indurated laterite, mottled clays and saprolite. Due to the scarcity of outcrop within the licences, lithologies have been determined by a combination of regional mapping, aerial photography, aeromagnetic surveys and previous drilling data.
A significant north-northeast striking regional fault occurs just to the west of the Boizan Licence where it is juxtaposed to Dixcove suite and Cape Coast suite granitoid intrusions. Numerous subsidiary east-northeast striking faults appear to have a strong control on the location of the gold soil anomalies.
Gold mineralisation associated with the Antubia mine and at other small historic workings within the licence areas is associated with quartz veins containing finely disseminated gold and considerable accessory pyrite and arsenopyrite. In general, altered Birimian meta-sedimentary and meta-volcanic rocks host the auriferous quartz veins, except at Afere, where mineralisation is hosted in a small Dixcove suite granitoid pluton.
Antubia Licence Prospects
The Antubia Licence includes the Antubia, Juabeso East and Afere soil anomalies. The excised Antubia Small Scale Mining Licence (SSML) sits completely within the Antubia Licence. This SSML was originally held by Akiko, whose exploration also covered the Antubia and Afere workings and several alluvial prospects in the Bezibata river valley.
The Antubia SSML (excluded from the Antubia Licence) represents the most significant historic workings in the Antubia area, having reportedly produced 18,690oz between 1912 and 1939. The mineralisation is located 0.5km south of Juabeso and comprises a quartz vein up to 0.9m wide that strikes 040º and dips 50º to 70º to the northwest. It is hosted by Birimian meta-sedimentary and meta-volcanic rocks and occurs in a dilational zone within the fault. The vein contains finely disseminated gold accompanied by considerable accessory pyrite and arsenopyrite. A five-hole diamond drilling program completed by Antubia Resources Limited between 1990 and 1992 targeted mineralisation near the main shaft. The results were apparently disappointing as they were not reported. Preliminary reverse circulation (RC) drilling by Samax in 1995 and 1996 (13 holes for 948m) indicated a series of sub-parallel, northwest dipping quartz veins and quartz stockwork mineralisation over widths up to 25m. Best intercepts of 14m at 1.83g/t and 8m at 2.58g/t Au were reported by Samax.
The Antubia soil anomaly, defined by Akiko, is an east-northeast striking zone, 1400m x 600m, that passes through the villages of Antubia and Danyame, located about 2.5km to the southwest, and along strike from, the Antubia mine. The broad anomaly consists of smaller anomalies 25m to 200m wide with gold values in the range of 100ppb to 1,000ppb.
The Juabeso East soil anomaly is located about 1.5km northeast of Juabeso and has gold values in the range of 100ppb to 1,000ppb. The anomaly trends northeast and is about 1,100m long by 200m to 500m wide, and remains open to the southwest towards the Antubia mine. The anomaly is interpreted to represent an extension of the Antubia mine structure. It is centred on old workings located in an area where a major northeast trending fault is intersected by oblique structures. Quartz veins, grading up to 5.4g/t Au over 3m are exposed in a number of adits within the anomalous zone.
The Afere workings are situated about 1.6km northeast of the village of Afere and about 3km southwest of Juabeso. The workings consist of several historic pits excavated on quartz veins hosted in a K-feldspar rich Dixcove suite granitoid pluton. Samples of quartz veins from the Afere workings are reported to have returned 2.8g/t and 2.6g/t Au. This prospect is situated within the SSML and is currently excised from the Antubia Licence.
The Afere soil anomaly strikes northeast and is centred over the Afere workings located 1.5km to 2km east of Afere village. The anomaly is 1,100m long, 800m wide and comprises gold values ranging from 100ppb to above 1,000ppb. The anomaly coincides with the intersection of a northeast trending fault and subsidiary oblique faults. The anomaly remains open in several directions. Quartz vein samples from artisinal workings returned assay results up to 30g/t Au. This anomaly straddles the boundary between the excised SSML and the Antubia Licence.
Artisinal mining activity at Afere suggests that miners are targeting a 50cm wide quartz carbonate vein, which strikes ~060° and dips ~70° degrees to the northwest. A series of these veins, of unknown strike length, occur within the area.
Small Scale Miners on the Afere Prospect
Boizan Licence Prospects
The Boizan Licence includes the Boizano, Sumiakrom and Metsemano soil anomalies within its northern portion, and the Edukrom and Bokabo soil anomalies in the south. The Boizano Prospect consists of an adit and several pits located about 0.5km south-southwest of the village of Abrokofe and 1.5km west of Boizan town.
The Boizan Licence includes the Boizano, Sumiakrom and Metsemano soil anomalies within its northern portion, and the Edukrom and Bokabo soil anomalies in the south. The Boizano Prospect consists of an adit and several pits located about 0.5km south-southwest of the village of Abrokofe and 1.5km west of Boizan town.
The Sumiakrom Prospect is located 2.2km south-southwest of Boizan and comprises an adit and ancient artisanal pits. It is reported that a small amount of gold was historically
The Sumiakrom anomaly is situated within a very prominent ridge and is associated with a number of Ashanti and colonial shafts developed on quartz veins and silicified meta-sedimentary rocks that have the same north-easterly strike as the veins in the Afere workings.
Four grab samples of quartz veins from an adit at Sumiakrom yielded a maximum value of 213ppb Au.
The Metsemano Prospect is located about 0.6km south of the village of Elubo and about 3km south of Boizan. Two samples of colluvium from the old pits yielded a maximum of 110ppb Au. Results of the regional geochemical program indicate a +40ppb gold anomaly oriented north-south and extending over a distance of about 3.5km, with widths of 600m to 1,000m. At the northern end of the anomaly at least, values of 1,150ppb to 5,200ppb Au are associated with alluvial material.
The Edukrom Prospect is located in the south-western part of the licence area. Historic reports indicate that samples of pyritic quartz vein from the Edukrom shaft, located 3.2km west of Amoya town, yielded very little gold. Spirax carried out soil sampling over the prospect, identifying a significant anomaly with values up to 2,359ppb Au. The Edukrom anomaly is up to 3km in strike length, and is open in all directions outside of the initial 400m by 50m grid. Eleven samples of mostly quartz vein exposures yielded up to 0.9g/t Au. The Edukrom Prospect lies at the intersection of the east northeast-striking Antubia mine structure and the western margin of the Sefwi Belt.
Exploration Potential
The Antubia area has not been significant in terms of large-scale gold production in Ghana. However, the Antubia mine is one of the few historic mines in Ghana to have produced over 15,000oz of gold.
There are three untested gold soil anomalies within the Antubia licence at Antubia, Juabeso and Afere. The Antubia and Juabeso East soil anomalies represent extensions to mineralisation along the east-northeast striking Antubia mine structure, with a strike length of over 5km. This has never been systematically tested by trenching or drilling. It is not currently possible to systematically test this 5km strike as the central part of the anomaly lies within the SSML excised from the Castle holdings.
The Boizan Licence has three untested gold soil anomalies (Boizan, Metsemano and Edukrom). These targets are prospective for mineralisation associated with sheeted and stockwork quartz veining within Dixcove Suite granitoids and shear-hosted, low-grade, laterally extensive disseminated sulphide and quartz stockwork systems within the Birimian meta-sedimentary and meta-volcanic rocks.
The project area is adjacent to a major fault and has also been a small historical producer. In addition, a number of promising, untested gold soil anomalies occur within the licences. RSG Global therefore considers the Antubia Project to have moderate to strong potential to host economic gold mineralisation.
Exploration Results
A program of RC drilling was completed in February 2007 to follow previous encouraging results from the Boizan Prospect. This drilling intersected widespread gold mineralisation.
Drilling on 100m spaced sections to follow up the intercept in BZRC 06 (18m @ 2.74g/t from 24m) reported 11m @ 2.70 g/t, 7m @ 1.26g/t, 2m @ 5.53g/t, 1m @ 9.1g/t, 10m@ 0.60g/t and 10m @ 0.80g/t gold and confirmed a five kilometre long zone, largely untested by drilling, that represents a high priority target capable of hosting a substantial gold deposit.
Better geological understanding has evolved from this drilling with a ~100m wide black shale rich unit identified as a marker horizon. Gold mineralisation is best developed on the footwall (west) side of this unit. Importantly this black shale unit is interpreted to join up with the Sumiakrom Hill prospect 3km to the south. This entire 5km long footwall zone of the black shale unit has a coincident soil anomaly (except where obscured by transported cover) and is considered a highly prospective target. This target zone is open to the south and currently extends to the limit of sampling.
Infill sampling, pitting, trenching and geophysical interpretation has commenced, with further drilling to be undertaken following this work.
These results are considered very encouraging and have greatly enhanced the prospectivity of the area.
In late 2007 results from a program of trenching were received during the quarter and 15 reverse circulation drill holes were completed.
Six trenches were excavated (1,002m) being designed to test spot high soil anomalies and to provide structural and geological information for RC drilling.
The trenches reported wide zones of gold mineralisation including 50m @ 0.27g/t, 33m @ 0.18g/t, 17m @ 0.21g/t gold within the very large 5x2km Boizan soil anomaly.
The trench intercepts have identified a number of parallel zones additional to the two mineralized zones (Boizan and Sumiakrom Hill) that were drilled earlier this year.
Fifteen RC holes were drilled late in the September 2007 quarter testing the trench results and a number of soil anomalies throughout the project area. Initial composite sample results have returned low order gold intercepts hosted by felsic to intermediate rocks.
Soil sampling was completed south of Sumiakrom hill and defined several new discrete soil anomalies that require further investigation.