LOCAL GEOLOGY
The Blanket Mine is situated on the north-western limb of the Archaean Gwanda Greenstone Belt, along strike from several other gold deposits. It is one of the few remaining producing gold mines out of the approximately 268 mines that were once operational in this greenstone belt. The Gwanda Greenstone Belt is located in south-western Zimbabwe. It is approximately 70 km in length (west to east) and 15 km wide (north to south). The belt is typical of greenstone belts of the Zimbabwe Craton consisting of mafic to felsic volcanics with intercalated sedimentary units.

Repeated strong deformation affected all lithologies. Structurally, the Gwanda belt is dominated by a major periclinal synform, plunging approximately 60° to the northwest in the western half of the belt. It is flanked on both sides by two major deformation zones, namely the North West Gwanda Deformation Zone (“NWGDZ”) on the north-western limb and the South Gwanda Deformation Zone (“SGDZ”) along the southern limb. The SDGZ forms part of a regional structure bounding the southern margin of the belt. In the convergence zone of the NWGDZ and the SGDZ, the Colleen Bawn Deformation Zone (“CBDZ”) splays off the SGDZ eastwards, following the north-eastern arm of the belt.

The NWGDZ is approximately 2 km wide by 18 km long with a general northwest to north-northwest trend, from the town of Gwanda to the north-western extremity of the belt. Repetition of lithological units, particularly in the north-western arm of the greenstone belt, is interpreted as evidence of D1 thrusting. Wide zones of intense schistose deformation, considered to be associated with the gold mineralisation, are the product of the D2 event. The D1 thrust phase has a coincident trend and may be an early part of the D2 event.

The large fold structures of the D3 deformation event dominate the eastern and western ends of the greenstone belt and are easily identified on geological maps and in aerial imagery. The mineralisation at the Blanket Mine and Vubachikwe lies on the northern limb of the large western fold (the North West Mineralised Camp).

PROJECT GEOLOGY
At and near the Blanket Mine, the lithologies comprise felsic schists of either sedimentary or igneous origin, overlain by mafic to ultramafic rocks containing layers of BIF, in turn overlain by a thick sequence of mafic rocks. The mafic unit which hosts the gold mineralisation is mostly a metabasalt with some remnants of pillow basalts. Regionally, the rock is a fine-grained massive amphibolite with localised shear planes. The entire sequence is cut by a regional dolerite sill from the south, through the Blanket Mine, to the Smiler deposit which lies approximately 3 km north of the Blanket Mine. Mineralisation at Vubachikwe is hosted in BIF interlayers. The mineralisation at the Blanket Mine is located in the overlying mafic unit.

BLANKET MINE OREBODIES
JETHRO OREBODY
The Jethro orebody strikes north-south and dips near vertical in a westerly direction. It tends to roll over locally.

BLANKET SECTION
The Blanket Section orebodies are located approximately 400 m to the north of the Jethro orebody. Blanket orebodies 1 and 4 are parallel. They occupy north-south trending shear segments whereas orebodies 2 and 5, which are also parallel, strike northwest-southeast. Orebody 3 is cylindrical and lies in a shear segment parallel to the 2 and 5 orebodies. On average, the orebodies dip 80° southwest. On surface, the Blanket Quartz Reef lies in the footwall of the disseminated sulphide replacement type orebodies. The reef has a shallower dip than the disseminated sulphide replacement bodies, but plunges in the same direction so that it progressively advances towards them with depth, displacing orebodies 2, 3, 1, 4. Orebody 2 reappears on the footwall of the Blanket Quartz reef and is established on the 630 mL through to the 870 m Level.

AR OREBODIES
AR lies approximately 500 m to the north of the Blanket orebodies. It is a “Z”-shaped mineralised zone and consists of two separate orebodies that generally reach up to 30 m wide as a result of tectonic thickening from faulting and folding. Lateral diamond drillholes (250 m long) were drilled either side of the haulage every 50 m. The body has no known surface expression and appears to form a ‘peak’ under the regional dolerite sill just above 9 Level some 500 m north of the Blanket orebodies. From this point the body splits into two ore shoots: the AR Main and the AR South, plunging west at 55º and south-west at 58 º respectively.

AR MAIN
The AR Main is a DSR-type orebody occurring within a broad shear envelope in pillowed metabasalts. The envelope is generally irregular in plan and is bounded by shears which assist in defining the limits of the mineralisation. At the lowest level of development on 750 m Level, a shear disrupts the bodies causing the plunge to flatten to the west. The orebody strike is between 40 m and 60 m with an average width of 30 m at the centre of the envelope.

The ore is a silicified amphibolite consisting predominantly of quartz with minor carbonate and chlorite minerals. Gold mineralisation is associated with arsenopyrite and to a much lesser extent pyrrhotite and pyrite. The orebody is massive and is exploited using the long- hole open stoping method. It currently contributes 20% of the Blanket mine production.

AR SOUTH
The AR South orebody plunges southwest, trending towards the Blanket No 2 Orebody at depth. AR South is also developed within a broad shear zone and is more pipe-like than the main body. Its maximum thickness is approximately 50 m. High grade sections of this body are defined by silicification and arsenopyrite.

EROICA
The main Blanket underground workings are connected to Lima by a 2 km long haulage which follows the strike of the main fabric. It thus offered an opportunity to probe for lateral orebodies on either side which led to the discovery of the Eroica shoot. The Eroica orebody lies approximately 1,300 m north of the main Blanket Mineral Deposits. It dips at 65° to the west and has a strike length of 300 m in a northerly direction. The Eroica orebody is hosted in a high-strain area where the shear is up to 15 m wide. Brown carbonate alteration characterises the shear in strong association with biotite development. The orebody is defined by thin silicified stringers that develop into swells of up to 5 m in width.

LIMA
The Lima Section is situated 2 km north of the Blanket Section orebodies. The two mines are linked by an underground haulage. The main shoots are the Hanging wall and Interlimb. In the hanging wall limb, mineralisation exists in the form of pyrite with subordinate arsenopyrite in cleavage planes within the pervasive biotite/chlorite alteration. The Interlimb is characterised by a centrally silicified core with pyrite and arsenopyrite constituting the main sulphides.

Two main types of mineralisation are recognised at Blanket mine, namely disseminated sulphide replacement reefs (“DSR”) and quartz-filled reefs and shears.

Blanket Mine uses mining methods that are commonly employed and well-understood by greenstone belt miners who generally have to deal with steep shear- hosted to massive mineral deposits. Since the nature of the mineral deposits varies, the exact mining practices are tailored to suit the specific attributes of each particular mineral deposit.

The main mining methods utilised at Blanket are:-
- underhand stoping in the narrow mineral deposits; and
- long-hole stoping in the wider mineral deposits.

Stoping preparations in narrow orebodies (less than 3 m wide) begin by mining raises at 10 m intervals along the haulage. These are usually mined from the footwall of the orebody to 10 m above the haulage drive. The extreme end raises are equipped as ladder-ways while the rest have boxes constructed under them. In wider orebodies, draw points are mined instead of boxes.

The wider orebodies are mined using long-hole open stoping methods which produce bigger rock fragments than the conventional methods. At the end of these draw point crosscuts, draw point raises are pushed 10 m to the above coning level. The draw point cross cuts are also mined at 10 m intervals along the haulage.

Where the orebody widths are less than 12 m the haulage is mined in the footwall of the orebody with draw points mined at 10 m centre-to-centre intervals from the footwall Haulage to the hanging wall contact. Raises are then mined from the ends of these draw points to the coning level. The draw points are mined 3 m wide and 3 m high.

Just as in the narrower areas the extreme end raises are equipped as ladder-ways. In both cases, a sublevel drive is then mined off the central raise to connect all raises laterally. These raises, one central and two at the ends, are then mined from the cone drive connecting all levels above. Additional sublevels are cut between levels after which the orebody is fully developed and ready for stoping.

Stoping commences by slyping around the central raise, on the cone level to expose the footwall and hanging wall contacts and will continue in retreat fashion 5 m either side of this raise.

Coning will then commence by blasting into the slot taking the full width of the orebody. The cone progresses down to approximately 3 m above the main level. As soon as the coning retreats a safe distance from the slot raise, to ensure men are safe from the rocks falling from above, a new stope is commenced at the central raise on the level above. This process is repeated on the sublevels above until a sufficient number of stope faces are in production above the cones to provide the required production tonnage.

The crushing and milling circuits are designed to process RoM.

The plant consists of the following circuits:
- jaw crushing;
- cone crushing in closed circuit with a screen;
- primary rod mill in open circuit;
- ball mill in closed circuit with cyclones.

The skips automatically tip ore hoisted to surface into the Shaft Bins on the No4 Shaft headgear. Ore is gravity fed from the Shaft Bins onto the No1 belt which conveys the ore over the automated belt scale and to vibrating screens and 14" x 24" Telsmith jaw crushers. This crushing circuit reduces the ore to minus 50 mm and it is then deposited by the No 2 belt stockpile conveyor onto the coarse ore stockpile which has a live capacity of approximately 2,000 tonnes of material. Ore from the coarse ore stockpile is then fed onto the triple-deck vibrating screen with the oversize being crushed to minus 12 mm by one of two 38H Telsmith Gyrasphere crushers. The 12mm ore is then fed into the 600 tonne Mill Bin which feeds the two (of the three installed) 1.8 x 3.6 m rod mills where it is milled down to approximately 70% passing 75 microns, before being passed through two 30 inch continuous Knelson Concentrators where approximately 49% of total gold production is recovered.

Tramp iron magnets (located ahead of the crushers) remove scrap iron before it enters the cone crushers. This is important as any iron products from underground will cause major damage to the crushers if allowed to enter the crusher bowl. The crushed ore is stored on a 900 t open stockpile from where material is fed to the cone crushers.

The cone crushers were upgraded recently and replaced with two 38" hydraulically adjusted Nordberg crushers. The crushers can operate independently and feed Osborne vibrating screens. The screened product which is smaller than 10 mm is delivered to the mill feed bin. The equipment quality is good and good maintenance is applied (an observation made during the site visit).

There are three 6.5 ft. x 12 ft. rod mills which operate in parallel. Each feed belt has a mill feed mass meter which is used to control and measure the mill feed rate. The foundations of the previous mills were in the process of being demolished which leaves adequate space for future expansion.

The Knelson Concentrator tails are pumped through cyclones and into a 3.66 x 4.9 m x 750kW (1,000 HP) regrind ball mill.

The plant consists of the following circuits:
- gravity circuit;
- dewatering cyclones;
- CIL;
- combined elution and electrowinning;
- smelt house;
- carbon re-activation in a kiln;
- reagent make-up and dosing circuits; and
- water recycling and storage.

Approximately 45% to 50% of the gold production is recovered as gravity gold. Concentrate from the Knelson Concentrators is stored and re-concentrated on a Gemini table every 24 hours with the tailings recycled back into the circuit. Gemini table concentrates go for direct smelting whilst the tailings are pumped to the classifying hydro cyclone. The Knelson Concentrator tails are pumped through cyclones, the underflow of which reports to the open-circuit regrind ball mill.

The product from the Knelson tails cyclone overflow and the regrind mill discharge is pumped into the CIL plant. The CIL consists of one pre-aeration tank and eight leach tanks where alkaline-cya ........