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Operations
Ghana
Overview
Chirano
Bolgatanga
Ahafo North
Bibiani North
Akyem
Enchi
Overview
Property Description and Location
Physiography and Accessibility
Geological Setting
Deposit Types
Exploration History
Bole
Mauritania
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EnchiOverview Enchi is Red Back's principal grassroots exploration project outside Chirano and has been the focus of regional exploration activity since mid 2004. Reconnaissance exploration at Enchi has resulted in the discovery of the Boin Valley East and Boin Valley West prospects where detailed exploration has included trenching, ground geophysics and drilling. Reconnaissance work throughout the holding continues. Property Description and Location The Enchi Project comprises nine Prospecting licences (including one application) and one Reconnaissance licence, totaling 706km2. The project covers a 50km strike length of the eastern margin of the Sefwi belt stretching from the Cote d'Ivoire border in the southwest to the southern margin of the Suhuma Forest Reserve, 25km south of the Chirano Mine.  click to enlarge Physiography and Accessibility The project is located in the Western Region of Ghana and is accessed from Accra on sealed roads via the regional port city of Takoradi and the mining centre of Tarkwa. The climate is hot and humid typical of lower elevation equatorial regions. Annual rainfall is 200cm, concentrated mainly between April and July. The project area comprises often steep topography, largely cleared of primary forest for the cultivation of cocoa. Geological Setting Most major gold deposits in Ghana occur in major shear zones on or close to belt/basin margins. The Enchi project area straddles the Bibiani Shear Zone, a major gold prospective, first order tectonic feature, trending northeast-southwest, juxtaposing Birimian mafics of the Sefwi Belt to the northwest against Birimian sediments and volcaniclastics of the Kumasi Basin to the southeast. The Bibiani Shear Zone hosts major gold mineralized systems including the Bibiani gold deposit (+5Moz) and Red Back's Chirano deposit (2.35Moz) to the northeast, and the Anuri Afema deposit (1.5Moz) in Cote D'Ivoire to the southwest. The Obuasi-Enchi lineament, a major east-west crustal scale feature deflects the Bibiani Shear zone between the Chirano and Enchi project areas. This lineament is associated with the major Obuasi (+40Moz) and Akyem (+10Moz) deposits in the Ashanti Belt, 100 to 200 kilometers to the east. In the Chirano area, the Bibiani Shear Zone swings in strike to north-northeast, bifurcates, and includes an enclave of Tarkwaian sediments. In the Enchi project area the Bibiani Shear Zone swings in strike to northeast, bifurcates in similar fashion, and includes structurally similar enclaves although not of Tarkwaian age. In both the Chirano and Enchi areas, these enclaves are bounded by second order structures evident in regional aeromagnetic, radiometric and digital terrain model data-sets. Gold occurrences are located close to third order structures, splays off the second order structures; sub parallel to the overall trend of the Bibiani shear zone. Deposit Types Several vein gold colonial and galamsey prospects have been located within the project area. Principal amongst these are the Tokosea and more significant Sewum Mines. Drilling at Sewum during the late 1990's showed the vein/shear to be erratic in width and tenor although reserves were said to have been blocked out prior to the mines closure in the 1940's. At Nyamebekyere, Leo Shield completed a large exploration programme delineating an unconfirmed and unreported inferred resource of 1.65Mt grading 1.4g/t Au (72,700oz). The Nyamebekyere lode strikes over a distance of 1600m, hosted by altered phyllite, 200 to 300m west of the interpreted position of the second order Nyamebekyere Shear. Initial soil anomalies were tested with 100m spaced trenches revealing generally weak lode intersections (best trench intersection was 4m grading 4.44g/t). Subsequent drilling tested mineralization over 1600m strike-length and up to 80m vertical depth. Shallow oxide and deeper sulphide associated gold mineralization were intersected on 28 sections at 40m intervals within an altered (carbonate-feldspar-pyrite) shear zone. An extensive envelope of weak gold mineralization (>0.25 g/t) dips sub-vertically and strikes 030º. Intersections of 10m to 40m width were recovered from nearly all holes testing the projected lode position. The general tenor of gold mineralization is low. Better grade (>1g/t Au) mineralization is less continuous, restricted to several shoots up to 200m in length within the low grade envelope. The drill pattern successfully defined the northern extent of better grade (>1g/t Au) mineralization but some potential exists at the southern end. There is potential for extensions and repetitions of better (>1g/t) gold mineralized zones and further drilling would be required to make a proper assessment of the resource. Exploration History Both alluvial and reef gold were prospected and exploited by several generations of galamsey workings to the present day. European companies explored, developed, and mined in several phases since 1900. The result is that erratic gold in vein quartz mineralization was "opened up" in a large number of pits, shafts, and drives, notably at the Sewum, Tokosea, Alatakrom, Achimfu, Nkwanta, and Kojina Hill prospects. Only the colonial Sewum and Tokosea mines appear to have any significant development and production history although this is poorly recorded. Available exploration records of any detail date from 1987 onwards recording renewed interest in gold exploration including: cleaning out accessible workings, extensive additional trenching, soil sampling, and drilling. Regionally focussed exploration was also commenced. Modest prospects were defined in limited catchments close to known gold-in-quartz vein deposits within the Sewum-Tokosea tenement. Geophysical techniques (aeromagnetics, EM) were applied at different times with varying success. Since 1995, regional soil geochemistry, in addition to redefining existing prospects, delineated some new areas of interest. Reconnaissance trenching, RAB, and RC drillling programs tested the gold-in-soil targets. Low grade, more consistently mineralized, oxide zone prospects were defined at Nyamebekyere and Kwakyekrom. The Nyamebekyere prospect was subsequently tested by further close spaced drilling and an unconfirmed resource was calculated by Leo Shield. Red Back has obtained considerable proprietary and public domain exploration data from a variety of sources including: vendors of multiclient geophysical survey data, previous tenement holders, the Ghana Geological survey, and the Ghana Mineral Commission. During the period January to July, 2003, the project was reviewed by Red Back Mining. The first objective was to assess the database: to determine the range, scope, and quality of the data available; to detect any important omissions; and to recommend any action to improve the quality and utility of the database. The second objective was to complete a desktop assessment: to research the exploration history; to assess the quality of the exploration programs completed; to evaluate the gold prospects of the area; and to define any potential targets for immediate attention. 2004 Exploration Program Exploration conducted by Red Back in 2004 comprised regional stream sediment sampling and the establishment of the first soil sampling grids in the Boin Valley area. At Boin Valley West this was based on elevated stream sediment sampling results from the 1990's confirmed in 2003 by Red Back. At Boin Valley East (5km to the east) two previous soil geochemistry programmes (1988 and 1997) had delineated significant gold in soil anomalies in the general area of the Sewum Mine. Red Back's grid sampling in this area was aimed at confirming and locating these anomalies. 2005 Exploration Program Soil sampling at Boin Valley West in late 2004 identified a 4.5km (+20 ppb contour), north east trending gold in soil anomaly with +100 ppb values over a 2.5km strike length and up to 300m in width. A Rotary Air Blast (RAB) drilling program (2,164m in 58 holes) was completed in June 2005 over a 1.40km section of the anomaly. The RAB program intersected two sub-parallel zones of mineralization, the Main and North zones, with intercepts up to 15m at 3.00g/t and 12m at 1.60g/t respectively. 10,203m of reverse circulation drilling where completed in 2005 and intersected mineralisation over a strike length of 3.6km. Mineralisation is hosted by shallow, westerly dipping mafic volcaniclastics in the hanging wall of a sheared, graphitic contact with phyllitic sediments to the east and is associated with quartz veining, fine grained disseminated pyrite and silicification. Click here to view Enchi Drill Results In 2005 at Boin Valley East the northern 2.2 km of the 4.5 km long +100ppb Boin Valley East gold in soil anomaly was tested with 10 trenches and 44 RAB drill holes to a maximum depth of 90 m. Based upon the limited amount of testing to date it is interpreted that two gold mineralized zones 500 metres apart have been identified, both dipping shallowly to the west in very heavily weathered Birimian volcanics and sediments:
In addition a trench located 800m south of the RAB drilling has returned very wide low grade intercepts (SSTR 1 - 249m @ 0.45g/t). 2006 Exploration Programme During early 2006 limited follow up drilling has been completed at Boin Valley West to test the continuity of the main zone and investigate possible extensions to the known mineralisation. Simultaneously a ground geophysical survey comprising magnetics and and Induced Polarisation (IP) surveys has been completed over the drilled area and the strike extensions 2km to the north and south. At Boin Valley East trenching continued on the Sewum South prospect following up on trench SSTR 1 - 249m @ 0.45g/t and was complimented by an IP survey. Further trenching continued to develop the prospect with wide low grade intercepts indicating a north north east strike whilst significant veining was seen orthogonal to the main trend. This veining comprises distinct veins up to 30cm as well as a strong fabric of stringer veinlets that carry grade, again over significant widths. First pass RC drilling was conducted on this prospect in late 2006 with additional holes drilled on the Hill Zone and Road zone. 2007 Exploration Programme Work continues to follow up on the Sewum South mineralised trend. IP surveys have confirmed a strong association with a major lithological contact and mapping and prospecting along this contact has located new areas of mineralisation that are being trenched in the second half of 2007. |
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