The Gold Deposits of Ghana
The Proterozoic rocks that comprise most of the West African craton and host the major gold mineralization in Ghana are subdivided into metasedimentary and volcanic rocks of the Tarkwaian and Birimian sequences.
The Birimian is composed largely of phyllites, schists, greywackes volcanoclastics, and metavolcanic rocks (including lavas, pyroclastics, and some finer-grained metasedimentary rocks). Unconformably overlying the Birimian are the continental clastics of the Tarkwaian sequence. These clastics were derived from the weathering of Birimian rocks and granitic intrusions found within the Birimian.
The area is dominated by a major northeast-southwest trending structural fault zone referred to as the Ashanti Trend, which hosts the Prestea, Bogoso, Obuasi and Konongo gold deposits, among others. Parallel to the Ashanti Trend is the Akropong trend, which hosts the Ayanfuri deposit. The Akropong Trend is about 15 km west of the Ashanti Trend in the Bogoso region, and gradually converges with it, coalescing at Obuasi and forming the basis for the world class Obuasi deposit, owned and operated by AngloGold Ashanti Ltd.
Gold operations in the Tarkwaian sequence include the Teberebie, Abosso, Tarkwa and Iduapriem mines.
- AngloGold Ashanti (NYSE:AU; JSE:ANG) has three gold mines in Ghana, Iduapriem (open-pit), Obuasi (which comprises both surface and underground operations) and Bibiani (open-pit), producing 680 000 oz attributable gold in 2005. (Bibiani was subsequently sold to Central African Gold)
- Golden Star Resources Ltd ( US, AMEX:GSS; TSX:GSC, also active in Sierra Leone and Côte d'Ivoire) operates the Bogoso/Prestea open-pit mine which has measured and indicated reserves of 20,8 million t at a grade of 2,18 g/t Au or 2,48 million oz gold and is expected to produce betweeen 260 000 and 290 000 oz in 2007. In March, 2007,the company announced the commencement of mining on its Pampe gold project. The Pampe project is a satellite deposit on the Akropong Trend, west of Bogoso, where they have been exploring for a number of years and have identified a 219,500 oz mineral reserve, which was included in the year-end 2006 mineral reserve estimate for Bogoso/Prestea. Golden Star is also developing the Wassa deposit with proven and probable reserves of 21,9 million t at a grade of 1,34 g/t Au or 940 000 oz gold. In May, 2007, the company announced the development of the Hwini-Butre and Benso gold project, as a satellite source of feed for the Wassa gold mine and which is expected to have a significant impact on Wassa, resulting in an increase in processed grade, production profile and life for the combined operation as well as an improvement in the average cash operating cost per oz. Golden Star announced in January, 2008, an updated resource model for the Bondaye and Tuapim deposits located in the Prestea South area of the Bogoso/Prestea concession approximately 20 kilometers south of the Bogoso processing plants. New drill results and the application of an amended resource model yielded a total of 525,000 oz of gold in the Mineral Indicated Resource category. This corresponds to a net increase of 409,000 oz of gold in unconstrained Indicated Mineral Resources.
- Gold Fields (NYSE:GFI; JSE:GFIELDS) operates the Tarkwa (709 000 oz gold in 2006) and Damang (235 000 oz gold in 2006) mines.
- Newmont Mining Corporation (US, NYSE: NEM) is developing both the Ahafo and Akyem open-pit projects. In the Ahafo area, 11 orebodies have been identified. Newmont purchased both the Ahafo and the Akyem projects as part of their Normandy Mining acquisition in February of 2002. Reserves have grown from a combined 3,3 million oz in 2002 to 20,3 million oz at year end 2006.
The Ahafo mine poured its first gold on July 18, 2006 and commenced commercial production in August 2006. Ahafo sold 202,000 ounces of gold in 2006 and is expected to produce between 410,000 and 450,000 in 2007 as the mine enters its first full year of production. Revenue from the mine is expected to reach $250 million in 2007 based on a gold price of at least $600 per ounce. Ahafo has a 25-year life span.
- Adamus Resources Ltd (Australian) is exploring the Salman and Anwia deposits, with a combined measured , indicated and inferred resource of 22 million t at 2,1 g/t Au or 1,5 million oz gold ( 1,0 g/t Au cut-off). Adamus Resources announced further exploration success at its Ghana gold project in October, 2007, with positive results from drilling at its Avrebo prospect revealing high grade gold mineralisation at shallow depths. The company's Southern Ashanti project has a resource of 17-million tons at 2,2 g/t for 1,2-million ounces of measured and indicated, and 6,3-million tons at 1,9 g/t for 390 000 oz inferred.
- Resolute Mining Ltd (Australian, ASX:RSG, operates the Golden Pride mine in Tanzania, active in Mali) is exploring the Weststar/Blue River and Akoase concessions.
- Red Back Mining Inc (Canadian, RBI.TO, RBIFF.PK) operates the Chirano mine with proven and probable reserves of 17,8 million tonnes grading 1.9 g/t Au or approximately 1,09 million oz contained gold. Gold production is expected to average 123 000 oz gold per year over an initial 8,5 year mine life. The Chirano Project is within the Bibiani gold belt along strike from Ashanti Goldfields' Bibiani gold mine. The Company has additional exploration projects and significant landholdings in Ghana both in proximity and along strike from Chirano and elsewhere in Ghana.
- Crew Gold Corporation (UK, operates the Lefa mine in Guinea) has 4 prospecting licences in the Wa area, north-western Ghana, and is engaged in early stage exploration.
- Glencar Mining plc is exploring the the Asheba concession covering 45 square kilometers in southwest Ghana, 20 kilometres south of the Tarkwa gold producing area. The Asheba concession has numerous gold prospects and old colonial mine workings most notably the deposits at Cheriaman-Asheba towards the southern end of the concession. Cheriaman was the site of a significant producing gold mine in the first quarter of the 20th century. There was also colonial era mining at Bankarayo, Saghissi and Korokoseh towards the northern end of the concession. The Asheba concession was originally held by Glencar as the Asheba-Kanyankaw concession in a 50:50 joint venture with Moydow Mines International Inc. (“Moydow”). The original Asheba-Kanyankaw concession was subdivided into the Asheba and Kanyankaw concessions, the former held by Glencar and the latter by Moydow. Each of Moydow and Glencar has a right to buy back into a minority equity interest in the other’s concession.
- Pelangio Mines Inc (Canadian, TSX:PLG.TO) is doing early stage exploration on its Obuasi property consisting of four mining concessions covering more than 411 square kilometres. The Obuasi property is located on strike and adjacent to AngloGold Ashanti’s Obuasi gold mine.
- Central African Gold plc (AIM:CAN) announced its acquisition of the Bibiani gold mine and related assets and liabilities, including a prospecting licence in Ghana from AngloGold Ashanti in December, 2006. The mine, located 250 km northwest of Accra, is situated in the Sefwi-Bibiani Greenstone Belt. Since its discovery in 1902, Bibiani has yielded almost four million oz of gold from both underground and openpit mining operations. The company intends to increase Bibiani’s resource base from its stated inventory gold, as at December 31, 2005, of 100 000 oz of ore reserve and 900 000 oz of mineral resource (JORC compliant) as stated in AngloGold Ashanti's audited 2005 accounts. The Bibiani main zone underground ore reserve estimate increased to 9,18-million tons, at a grade of 3,57 g/t for 1,05-million ounces, at a cut-off grade of 2 g/t , in September, 2007.
The ore reserves have been estimated from within measured and indicated mineral resources totalling 13,32-million tons at 3,66 g/t for 1,57-million ounces at a cut-off grade of 2 g/t.
- Midlands Minerals Corporation (Canadian, MEX.V, also active in Tanzania) is exploring the Kaniago and Sian Esaase properties in Ghana. Kaniago is located on the Asankrangwa Gold Belt, approximately 33 kilometres east-southeast of AngloGold's Bibiani mine. The indicated gold resource on Esaase totals 1,232,340 metric tonnes at an average gold grade of 2,24 g/t Au (cut) and 2,62 g/t Au (uncut). The resource was calculated using a 0,5 g/t Au cut-off.
- Mwana Africa plc's Konongo property which was acquired in 2004 (70% interest through Owere Mines Ltd), covers 330 square kilometres located at the north eastern extent of the Ashanti gold belt in central Ghana. It covers an area that has been the site of mining activity since the 1930s, when underground mines exploited high-grade free milling gold within quartz veins at Obenamase. Total historic production before the closure of operations was 1,65 million oz at an average grade of 15,7 g/t. The indicated resource is 965,000 oz. A prospecting license, Kurofa, surrounding the Konongo lease was granted in June 2005. The Banka concession, acquired in 2004, lies 50 km to the south of the Konongo concession, adjacent to Newmont’s Akim deposit. The project vendors, Gulf Coast Resources Inc. are currently milling old 1930’s development stockpiles from the shaft 19 area near Banka village via a crushing and gravity circuit. Recoveries are variable, but appear to be better than 6,0 g/t Au. Mwana’s Ahanta project lies at the southern limit of the Ashanti gold belt. A joint venture was entered into in 2004 whereby Mwana can earn an 80% interest by staged exploration.
- Azumah Resources Ltd (Australian, A6Z.BE) is exploring the Wa-Lawra Gold Project based on a single Reconnaissance License covering 2,177 km² which includes an inferred resource of 225,000 ounces of gold at the Kunche Main deposit that is open along strike and at depth. Azumah Ghana has applied for a Prospecting License over the area including the Kunche Main deposit. In December, 2007, Azumah Resources completed a 53-hole RC and 5-hole combined RC/Diamond Drilling programme for a total of 6,402.6 metres at its main 500,000-ounce Kunche gold resource and the newly defined Kunche East and Bepkong target areas within its 100%-owned Wa-Lawra Gold Project in north-west Ghana. Assay results from this drilling were expected to be available in late January 2008. Additional drilling will commence in early February 2008 at these and several new targets generated from continuing truck-mounted auger sampling campaigns.
- Pan African Resources plc announced on June 28, 2007, that it had agreed to buy 90% of the rights to the Akrokerri exploration property in southern Ghana, situated near AngloGold Ashanti's Obuasi mine. Pan African Resources said it would pay £52,632 in cash and £720,000 in shares for the prospect. The company signed an agreement to acquire 90% of the Akrokerri Exploration Property, in southern Ghana, from Sems Exploration Services and Birim Goldfields. Birim continues to hold the remaining 10% interest in Akrokerri, but Pan African Resources has the right to acquire the interest from Birim once the project reaches the bankable feasibility stage.
The idea is to extend the Obuasi openpit mine and then the Akrokerri mine, which has produced 70 000 oz at 28 g/t. Pan African Resources is currently busy with three-dimensional modelling of the projects and will start drilling in 2008.
- Birim Goldfields Inc is exploring the following properties: The Bui Belt Properties
Birim was the first company to systematically explore the entire Bui Belt, recognizing its geological similarity to the Ashanti and Sefwi gold belts that host the world-class deposits of Ghana. Birim dominates the Bui Belt with 13 wholly owned properties and two additional properties under application. An extensive exploration program is underway; including drill testing multiple targets areas identified on many of the Bui Belt properties including the Chert Ridge Prospect and Tinga Far East Resource.The Sefwi Belt Properties. Birim owns the Bia Tano, Bando Ahenkro and Nkenkasu properties on the Sefwi Gold Belt and has an option to earn 100% of the Techimentia property, all within close proximity to Newmont's world class Ahafo Gold Mine. A total of 3.8 million oz of gold has been produced on the Sefwi Belt; at least 18.1 million oz/gold remain. Nkenkasu is being fast tracked for initial exploration, soil sampling and scout drilling. In August, 2007, the company announced that it had agreed to give Newmont an initial 49% stake in its Banda Ahenkro Property on the Sefwi Belt. Newmont will have the right to earn another 21% by spending US$1.5-million on exploration over four years, Birim said in a statement. Another 10% (up to 80%) can be achieved if Newmont elects to do a feasibility study on the property.The Government of Ghana retains a 10% free carried interest in all gold mining development projects in Ghana. Ashanti Belt Royalty Property. Birim sold the 125 sq. km. Dunkwa property on the Ashanti Gold Belt to Golden Star Resources for US$3.4 million and maintains a sliding scale royalty (NSR) currently equal to 3.5% on all production including the Mampon deposit (after the first 200,000 ounces). Production is scheduled to commence in 2008.
- PMI Gold Corporation acquired three former gold producing mines in Ghana: Nkran, Abore and Adubiaso. These mines were previously operated as the Obotan Gold Mine by Resolute Amansie Limited, a subsidiary of Resolute Mining of Australia.
Between 1997 and 2002, the Nkran pit at Obotan produced an average of 146,000 ounces of gold per year for a total of 590,000 ounces of gold at an average grade of 2.2 g/t. The Abore and Adubiaso pits located 12.5 km and 4.0 km northwest respectively of Nkran, together produced a further 140,000 ounces at similar grades.
In late 2002, after five consecutive years of low gold prices, which averaged approximately US$300 per ounce, Resolute decided to close operations and to commence the site rehabilitation process.
In 1997 a bankable feasibility study reported 38 million tonnes at 1.96 g/t for 2.823 million ounces of contained gold. Over the next six years 730,000 ounces of gold were recovered and the mine closed. PMI Gold believes there is an exploration target below the Nkran pit of one to two million ounces of gold grading from 3 to 6 g/t Au. This assumption is conceptual at this time, and it is uncertain if further exploration will result in the target being delineated as a mineral resource.
PMI Gold announced on 17 September, 2007, that it would buy the Kubi gold project, in Ghana, from Nevsun Africa (Barbados), a wholly-owned subsidiary of Canadian gold firm Nevsun Resources. The Kubi project is located 20 km south of AngloGold Ashanti’s Obuasi mine, and was first developed by local artisanal miners in the 1920s. PMI Gold would acquire all the shares of Nevsun Resources (Ghana), a Barbados registered company that owned the Kubi project, for nine-million shares in the firm, and an additional $3-million. n 1988, the then BHP outlined strong gold anomalies near the old workings and completed a programme of ground geophysics and drilling. Nevsun Resources (Ghana) optioned the property from BHP in 1993, and has subsequently completed extensive exploration, and defined gold mineralisation in a near vertical, between 1 m and 15 m thick,gold, garnet, and sulfide rich horizon. Drilling has defined the mineralised zone over an 1 800 m long by up to 700 m deep block contained within a northeast trending shear zone at the contact between the Birimian and Tarkwaiian metasediments. In 1999, Nevsun Resources (Ghana) transferred the property to Ashanti, which, in return for cash and royalty payments to the company, mined from two small pits 58 696 oz of gold in 500 230 t of oxide ore grading 3,65 g/t gold, with the recovered grade 28% higher than Ashanti's modelled grade. In 2006, Ashanti started the mine reclamation and said that it was returning the property interests to Nevsun Resources (Ghana).
- Etruscan Resources Inc is doing follow-up drilling on the Bole-Bolgatanga Gold Belt to ascertain the results of the sampling on historic trenches of the Bolgatanga Reconnaissance Licence, which gave intersections of 12 metres for 7.0 g/t, 10 metres for 5.0 g/t, eight metres for 5.7 g/t and 10 metres for 2.1 g/t
- General Metals Corporation (OTCBB: GNMT) (FRANKFURT: GMQ) owns 150 sq. km. of mining concessions for gold, diamonds and base metals and plans to commence exploration activities in 2008.