In September 2009, Stratex acquired a 5.6% interest in PLUS-quoted Sheba Exploration (UK) plc (Sheba) and signed a Binding Letter of Intent with Sheba with an option to earn-in to an initial 60% of the prospective Shehagne project.
The 50 sq km Shehagne Exclusive Exploration Licence (EEL) is located in a highly prospective area (the Arabian Numbian Shield, 'ANS') near the town of Adwa in northern Ethiopia (Fig.1).
Extensive gold anomalism in soil has already been identified in the Shehagne EEL by Sheba, with the main target to date being the Tsemmetti prospect in the south-eastern part of the EEL where the company has defined a large >100 p.p.b. gold-in-soil anomaly over a three kilometre strike.
Partnership with Sheba
Stratex has acquired a 5.6% interest in Sheba for £40,000 through a private placement at 0.75p and is also entitled to matching warrants at 0.75p exercisable for two years. Additionally, Stratex and Sheba have signed a Binding Letter of Intent giving Stratex the option to earn-in to an initial 60% of Sheba’s Shehagne EEL by expending £100,000 in the initial three months and a further £250,000 over the subsequent 18 months. It may also earn a further 20% (total 80%) by taking the project to completion of a feasibility study.
Stratex intends to undertake regional sediment sampling (minus 200 mesh stream) of the entire 50 sq km concession and complete systematic exploration of prospects already defined.
Additionally Stratex and Sheba have agreed a JV on a respective 70:30 basis, whereby the two companies will jointly identify and explore new prospective targets in northern Ethiopia. Potential licence areas that are currently under review are thought to have excellent potential for the discovery of gold (+/- copper) and massive sulphide deposits. Under the terms of the new JV, Sheba may earn up to 50% of the JV by reimbursing Stratex 20% of the total exploration costs.
Regional geology
The region is underlain by the southerly extension of the highly prospective Arabian-Nubian Shield (ANS). The rocks of the southern ANS are of Proterozoic age and host major economic mineral deposits, including Nevsun’s Bisha VMS deposit in Eritrea (1.61 M oz Au; 35.61 M oz Ag; 456,314 tonnes Cu; and 887,227 tonnes Zn), Sunridge’s Asmara VMS in Eritrea (955,000 oz Au; 31.2 M oz Ag; 580,598 tonnes Cu; 1,133,981 tonnes Zn), Centamin’s Sukari intrusion-hosted gold deposit in Egypt (12.9 Moz Au – open at depth and along strike), and MIDROC’s Legadembi gold deposit in southern Ethiopia (average annual production of 113,000 oz Au in the period 2000 to 2005).
The Proterozoic rocks of the southern ANS have typically undergone greenschist facies regional metamorphism. The Proterozoic units comprise mafic to felsic volcanics, marine sediments, and porphyritic intrusions. Cenozoic phonolitic plugs occur throughout the region and form steep-sided topographic highs. Hydrothermal alteration of the various rock types is widespread.
Potential exists for a wide variety of mineral deposits, such as volcanogenic massive sulphide (VMS), mesothermal lode gold quartz veins, intrusion-hosted mineralization, skarn, and epithermal-type mineralization. Rapid rift-related uplift and exhumation have increased levels of erosion, potentially exposing mineral deposits in deep crustal environments, including mesothermal quartz veins and mesozonal mineralized intrusions.
Prospect geology
Mineralization at Shehagne is typically hosted within fine- to medium-grained felsic volcanics largely interpreted to be tuffs. Small areas of volcaniclastic shale also occur, grading into fine quartzite and chert, with small andesitic intrusives locally. Conjugate fractures and associated shear zones trend SW-NE and SE-NW.
Gold is associated with quartz veins and stockwork veinlets hosted in felsic volcanics. Alteration is associated with the veining and is pervasive within the surrounding wallrocks, commonly occurring as broad zones of silicification. Gossans occur throughout the area as zones of intense oxidation and supergene enrichment of iron sulphides, typically pyrite. Quartz veining associated with the gossans is the key exploration target, and may represent gold-rich VMS-type mineralization.
Exploration
As part of an initial reconnaissance visit Stratex collected a total of 20 check rock chip samples, which were sent to OMAC laboratories in Ireland. Best results included 15.2 g/t Au and 6.12 g/t Au from narrow quartz veins.
This was followed by a prospect-wide regional stream sediment programme which was undertaken from Q3 - Q4 2009, and identified a number of targets. Several samples returned with gold values exceeding 100 ppb within the wider licence area; these anomalous catchments are currently being followed up.
Following the results from Road Cut (RC) channel sampling, follow-up channel-chip samples were taken across the Tsemmetti target, defining a series of sericite-altered zones within the tufaceous host rock. Within these zones the gold mineralization is associated with a series of sub-parallel quartz veins and is also disseminated within the host rock.
To date, RC and channel-chip sampling results include:
- RC1: 51 metres grading 0.88 g/t Au from (0 to 51 m), including 17 m grading 2.02 g/t Au;
- Channel 1B: 14 metres grading 0.44 g/t Au (13 to 27 m);
- Channel 2A: 40 metres grading 0.41 g/t Au (0 to 40 m);
- Channel 2B: 84 metres grading 1.04 g/t Au (0 to 84 m) including 40 metres grading 0.91 g/t Au (0 to 40 m) and 28 metres grading 1.76 g/t Au (56 to 84 m);
- Channel 3D: 108 metres grading 0.43 g/t Au (0 to 108 m), including 31 metres grading 0.82 g/t Au (0 to 31 m);
- Channel 3G: 104 metres grading 0.77 g/t Au (0 to 104 m), including 24 metres grading 0.96 g/t Au (3 to 27 m), and 11 metres grading 4.39 g/t Au (64 to 75 m);
- Channel 4C: 52 metres grading 0.29 g/t Au (232 to 284 m), and 9 metres grading 1.35 g/t Au (154 to 163 m)
NB: A top-cut of 10 g/t Au has been applied to all samples, with no lower cut-off applied. Sample intervals are between 1 and 6 metres.
Recent RC and channel-chip sample results, combined with work previously reported by Sheba, delineates an anomalous north-east trending zone of gold mineralization covering an area approximately 900 metres long by 200 metres wide. Furthermore, due to the steeply incised topography, the vertical extent of mineralization is approximately 70 metres, indicating significant potential for its downdip continuation. Mineralization remains open to the north-east and south-west.
History
The Shehagne EEL area was selected following a prospecting programme by Sheba on the 98 sq km Bhiza EPL in the period 2001-2004. Early prospecting involved the collection of stream sediment samples, geological mapping and follow-up soil sampling along regional traverse lines. The stream sediments contained anomalous gold in a number of drainage channels terminating at the watershed on the southern boundary of the licence area, thus proving the primary source is within the licence area on the south side – this was supported by the observation of hundreds of artisanal gold panning sites in the same river channels. Follow-up soil traverses turned up a strong gold anomaly (>1000 ppb) at Tsemetti locality and a number of weaker gold anomalies in other parts of the licence area. In September 2006 the Shehagne EEL was issued covering 50 square kilometres of the best gold anomalies encountered in the Bhiza prospecting programme. In 2006-2009 intensive soil and rock sampling was carried out at Tsemetti and further south to Hadush Adi along a 3 km gold trend. Regional soil and rock sampling continued in other parts of the licence area where minor gold was encountered, notably at Maichew, Kurren and Ashimina.
Systematic soil sampling of the Shehagne prospect on a 100 m x 100 m grid defined the gold soil anomaly to a high degree of confidence (537 soil samples), using a threshold of 100 ppb. Rock grab sampling located the source of the gold in bedding parallel and cross-cutting quartz veinlets – the average grade of 99 grab samples taken from the soil anomaly area was 3.2 g/t gold without cut-off, but most of these were selected as quartz samples. Continuous rock or saprolite sampling from channels along weathered outcrop and chips recovered from drill holes showed economically interesting grade x thickness, for example:
- Trench SA1: 17 m @ 0.70 g/t
- Trench SA2: 8 m @ 2.06 g/t
- Trench SA3: 20 m @ 3.15 g/t (inc. 17 g/t over 2 m)
- Trench SA5: 18 m @ 1.22 g/t
- Trench SA8: 12 m @ 0.62 g/t
Percussion drilling in 2008 was carried out in four vertical holes, for a total of 172 m. Results included:
- Hole SAP1: 12 m @ 1.14 g/t from surface
- Hole SAP3: 23 m @ 0.54 g/t from surface
- Hole SAP4: 19 m @ 0.62 g/t from surface
Gold and pyrite mineralization were identified over a vertical range of 45 m and a horizontal distance of 340 m, open in all directions. The vertical depths of the holes (max. 52 m) and the locations of the drill sites were limited by accessibility and lack of funds. Chip samples showed disseminated fine (0.1 - 0.2 mm) pyrite is often associated with the gold, suggesting, as do the channel samples, an impregnation style of mineralization related to fractures which is often, but not always, marked by quartz veinlets.
In 2009, Sheba undertook detailed channel sampling of fresh outcrop from scoured river beds which demonstrated that the gold occurs in numerous narrow quartz veinlets and also extends into the altered bedrock around the quartz veinlets. The gold occurs over narrow but often high grade intervals: at a cut-off of 0.1 g/t the average intersection from 33 channel samples from one locality (Mai Weyni) is 2.2 g/t over 0.6 m. The best intercept at this locality was 15.1 g/t over 0.9 m.
