Overview

Gold deposits were discovered at Tirek in 1971 and the initial mine development commenced in 1998. Mining high-grade quartz veins by open cuts started in June 2001 and the run of mine was hauled to a processing facility built on site. More than 70 auriferous quartz veins have been identified at Tirek.

The Tirek goldfield is located approximately 60 km north of Amesmessa and is about 10 km south of the property boundary.

The veins occupy an area approximately 3 km wide and 12 km along the north-south orientation. This block has been broken down into the A, B and C Fields (« Champs ») on the basis of geography and geological setting.

Most of these veins have been the focus of detailed exploration work including trenching, drilling and actual mining in shallow open pits. Underground work at Tirek involved about 1,350 m of exploration drives at the -40-m level. Three shafts were sunk and drifts totalling 610 m were driven along Veins XIV, XIV-1 and XV (Shaft 1), 360 m on Vein II (Shaft 2) and 60 m on Vein III (Shaft 3).

The JORC-compliant Measured and Indicated Resources for Veins II, III, XIV and XV at Tirek have been estimated at 404,000 tonnes grading 16.96 g/t Au for 220,000 oz Au. Additional Resources in the Inferred category amount to 225,000 tonnes at 16.4 g/t Au, representing 179,000 oz Au (Minproc, Sep. 2005 ; base case).

The Proven and Probable Reserves have been estimated at 353,000 tonnes grading 11.0g/t Au representing 125,000 oz Au (Minproc, Sep. 2005 ; base case). An in-house study has shown that some additional  mill feed in the amount of about 26,000 tonnes at 18.0 g/t for 15,000 oz Au can be sourced from veins excluded from Minproc’s base case.

The gold mineralisation at Tirek is also associated with the north-south striking In Ouzzal east deformation zone. However, two distinct structural settings and two main vein orientations characterize the Tirek goldfield. The western portion of the area (Fields A and C) is comprised of N-S trending quartz veins situated within the mylonite and relatively close to the western IODZ contact, in a setting similar to Amesessa’s. In contrast, the eastern sector, designated as Field B, includes quartz veins in a tapered gabbro intrusive 12 km long and 2 km wide.

The mapped gabbro intrusive is a complex made up of medium-grained, generally massive but locally altered and foliated gabbro, enclosing units of pillow lava and xenoliths of granite-gneiss. The quartz veins in this area are represented by both a N-S and NE system. Most of the gold mineralization occurs in Field B in the gabbro host.

The N-S veins in the gabbro line up in the western sector, a couple of hundred meters to the east of the western contact. The dominant veins strike N to NNE and dip on average at 70º to the E and to the W, while the NE trending veins are more gently dipping at 45º to 70º to the north-west and display abrupt changes of attitude. No veins were found in the southern third of the gabbro intrusive.

Virtually all the NE trending veins are restricted to the gabbro host and to the east side of the N-S veins. No cross-cutting relationships have been observed between the N-S and NE sets, which strongly suggest the veins are coeval.

The gold mineralisation in the veins locked in the mylonite is represented by the quartz vein and the metasomatite halo, like is the case at Amesmessa. In contrast, the gabbro-hosted veins carry the high gold values but the selvages of wallrock alteration seldom contain economic gold grades. A fringe of schistose and hydrothermally-altered gabbro is usually visible along the vein contacts but only affects the host rock over a short distance.

The quartz is typically glassy, white to dark grey, is locally brecciated or encloses angular country rock fragments. The quartz contains traces to about 3% euhedral pyrite and visible gold and galena has been observed locally. As at Amesmessa, the darker colour of the quartz is indicative of higher gold values, as is the presence of sulphides, particularly galena. The average gold fineness for the whole deposit is 6.8 :1 and the trace-element suite of As, Bi, and Pb is typical of mesothermal lode gold deposits.

E-W and NE trending faults have caused apparent offsets of the veins up to 20 m. The map patterns indicate an oblique component of movement but the amount and sense of displacement along them is undetermined.