Overview

Prospecting in the region since the 1970s led to the discovery of about 50 mineralised veins in the Amesmessa area, with the main Amesmessa deposits found in 1978.
The Amesmessa goldfield is located approximately 60 km south of Tirek and is about 10 km north of the property boundary. The Amesmessa Vein deposits stretch over 12 km along a north-south direction. The area has been geographically broken down into a Southern, Central and Northern zone. The Central Zone includes the most important Veins 7 to 11 that extend over 3 km of strike length and contain about 70% of the resource estimate.

Most of these veins have been the focus of detailed exploration work including trenching and drilling. The major Veins 8 and 9 have been investigated by core and destructive drilling to a depth of -425 m. In addition, they were developed and sampled by underground workings totaling 516 m of lateral development drift (2.5  x 2.0 m) and 26 cross-cuts, at a depth of 80 m accessed via a vertical shaft.

The JORC-compliant Measured and Indicated Resources for Veins 8 and 9 stand at 1,043,000 tonnes grading 12.05 g/t Au representing 405,000 oz Au. Additional Resources in the Inferred category amount to 810,000 tonnes at 8.0 g/t Au, equivalent to 209,000 oz Au (Minproc, Sep. 2005; base case).

The Proven and Probable Reserves have been estimated at 748,000 tonnes grading 12.2 g/t Au representing 294,000 oz Au (Minproc, Sep. 2005 ; base case). An in-house study has shown that some additional feed in the amount of about 490,000 tonnes at 12.79 g/t for 210,200 oz Au can be sourced from veins excluded from Minproc’s base case.

The mineralised veins are hosted in felsic and mafic mylonites and, within the Central Zone, in one or several gabbro intrusive bodies. As exposed in the open pits, the gabbros are plunging, narrow, elongate bodies or lobes of a large intrusion emplaced obliquely to the schistosity. The rock is massive to weakly sheared and appears to be the least altered of the host rocks. Chilled margins are still recognizable.

The mylonite exhibits the typical geometry of a shear zone, with anastomosing patterns and corridors of higher-strain zones. Shallow, doubly-plunging lenses and numerous folds are present. The geometry of the host mylonite is complex as a result from transposition and interference of the early regional folds cut by the IODZ shear zone with the newly-formed folds related to the shear zone movements.

The major auriferous veins have a general north-south strike and 65 to 70º westerly dips. The veins are usually sinuous, anastomosing and en echelon. Two main subparallel veins are present over most of the Amesmessa area and they form a long sinuous and discontinuous line. The veins are clearly concentrated in a corridor located at the proximity of the western contact of the IODZ with the Archean. The veins closely parallel the curvature of the IODZ contact and generally trend N-NW in the Southern Zone, N-S in the Central Zone and N-NE in the northern Zone. An array of ENE-WSW veins (Zones 26 and 19) has been mapped to the east of the Central Zone. Faults of the E-W system have caused some offset of the veins over short distances.

The individual quartz veins consist of plunging lenses (shallow plunge to the north for Vein 9) and usually include shoots of higher gold grade material. The gold mineralization occurs in the quartz veins and the metasomatite, in zones that can be continuous for more than one km on strike and exhibit a width varying between 1 to 12.

The wallrocks in the mylonite have been moderately to intensely affected by hydrothermal alteration evidenced by silicification, sericitic, carbonate and potassic alteration to form a metasomatite (« beresite » of the Russian nomenclature).  The metasomatite development can reach widths of up to 12 m and usually is in sharp contacts with the unaltered country rock. The metasomatite has commonly low gold tenors but locally carries grades exceeding 10g/t Au. The metasomatite may contain quartz veinlets and 1 to 5% disseminated pyrite and is generally more strongly developed than at Tirek.

The auriferous quartz is typically glassy, white to dark grey, locally fractured, brecciated, and may contain angular country rock fragments. The quartz includes traces to about 3% euhedral pyrite, frequent visible gold, and galena has been observed locally. As noted on the rest of the property, the darker colour of the quartz is indicative of higher gold values, as is the presence of sulphides, particularly galena. The overall Au:Ag ratio is 3:1 and the trace-element suite of As, Bi, and Pb is typical of mesothermal lode gold deposits.

Sulphides are intensely oxidised at the surface but the oxidation process seldom reaches depths exceeding 10 to 15 m

The lenticular nature of the quartz-gold vein implies that the potential to find new blind veins cannot be ruled out. Considerable potential exists to find material of lower gold grade in the metasomatite associated with the quartz veins due to the fact that the previous workers regarded it as of little economic interest. Even at relatively low gold tenors, this metasomatite can presently be economic using the heap-leaching process introduced by ENOR.

It is interesting to note that the overall distribution of the N-S and E-W vein sets at Amesmessa is reminiscent of the arrangement of the veins in the gabbro at Tirek.