The Matchless Amphibolite Belt is a conspicuous narrow northeast-southwest trending sequence consisting of amphibolite, chlorite-amphibole schist, talc schist and metagabbro which extends over a distance of 350km in the Southern Tectonostratigraphic Zone of the Damara Orogen. The Matchless Belt represents a sequence of metamorphosed tholeiitic basalts, which are the product of submarine volcanism. Stratigraphically the Matchless Amphibolite Member occurs within the Kuiseb Formation (Khomas Subgroup) of the Damara Sequence, which is a metapelitic sequence of biotite schists, with subordinate calcsilicate rocks and carbonaceous schists.

The Matchless deposit comprises six echelon shoots namely the Eastern Prospect, East Shoot, West Shoot, River Shoot, Western Prospect and Western Extension, extending over a strike length of 2.5km from the east to the west in that order. The East Shoot, West Shoot and River Shoot form the old Matchless Mine. The mineralisation occurs in amphibolites and quartz-sericite schist lying between the Matchless Amphibolite and the Footwall Amphibolite, dipping at 30o , 350o towards the north and plunges to the northwest. The mineralised zones are distinct pyrite chalcopyrite occurring in a quartz mica schist. A slight angular discordance between the mineralised zone and the Matchless Amphibolite was mapped on outcrop. The mineralisation is strata-bound and is of a massive sulphide type containing mainly pyrite, pyrrhotite, chalcopyrite and minor sphalerite, gold and silver.

The Otjihase deposit comprises five sub parallel, spatula-shaped, mineralised zones namely Shoot A, Shoot B, Shoot 2, Shoot 3 and Shoot 4. Shoots A and B are known collectively as the Main Shoot in mine terminology because of their close proximity, but geologically they are separate entities. The shoots consist of massive sulphides composed primarily of chalcopyrite and pyrite, hosted in a magnetite rich quartzite. Of the five, only Shoot A is consistently mineralised and forms the bulk of the mineral resources.

With the exception of Shoot B, which is slightly elevated above the southern margin of Shoot A, the westerly-plunging mineralised shoots occur at approximately the same stratigraphic level and are separated by more than 150m of barren or weakly mineralised quartz-mica schists that dip north westerly at 16°.

The northern margins of the shoots are abrupt, whereas the southern margins are gradational, consisting of thin bands and lenses of mineralisation, or disseminated mineralisation, in the quartz-mica schist country rocks. The footwall contact between the lowermost mineralised band and the underlying quartz-mica schists is usually sharp. The hangingwall contact is often gradational due to the presence of zones of disseminated mineralisation.

Each of the shoots has a gossanous outcrop and extends down plunge for more than eight kilometres. The mineralised shoots are cut by a series of sub-vertical northerly trending normal faults that down-throw the shoots progressively deeper towards the west. The faults separate the deposit into a number of blocks (or compartments) named after the faults that occur along the western margin of each block.

The Otjihase deposit lies in quartz-biotite chlorite and quartz-biotite schists and consists of a shoot of massive and disseminated sulphides about 200m wide plunging to the west at about 6°. The deposit dips to the northwest at about 16°. The shoot thickness varies between 4m and 12m with an average between 6m and 8m. The hanging wall is a quartzbiotite chlorite schist with distinct schistosity which sometimes spalls. It is competent if supported. The declines and other development are usually excavated in competent quartzmica schists.

The mineralisation stretches from near surface to depths of 800m and more and is divided into compartments by north-south trending faults. These faults are water bearing and contain flowing material and are thus difficult to traverse.

A shoot called Matchless Western Extension, some 1,800m west of the old Matchless mine, was being mined by means of a decline that reached 11 Level. The shoot has a steep plunge to the northwest and the deposit dips at 35° to 45° which requires the decline to progress rapidly down dip.

Previously, the Matchless mine was operated successfully by a mining contractor using a cut and fill mining method. The planned mining method is a cut and fill method utilising 3.0m high lifts.

The Otjihase compartment extends from the surface down to a depth of approximately 260m below surface. The upper area, down to around 180m below surface was mined by JCI using a room and pillar system based on 5m by 5m square pillars with 15m wide rooms on dip and strike.

The ore is trucked to an underground crusher station immediately east of the Hoffnung East fault from where it is transported by means of 10 conveyor belt sections to a point where it is tipped into kibbles pulled by locomotives which take the ore the last 1.5km to the mill receiving bins on surface.

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The Otjihase concentrator is designed as a sequential flotation plant treating a base metal sulphide mineral deposit. The economic metals in the ore are copper and silver with pyrite and small amounts of gold.

During the last 20 years, the plant has been operated by TCL, Ongopolo and latterly Weatherly. No major plant modifications were implemented over the operating period other than a Maxwell cell which was installed in the pyrite circuit, the backfill plant, and some equipment refurbishment to ensure continuity of operations.

Copper flotation
The flotation circuit consists of three rougher and scavenger flotation banks with two banks of cells for the cleaning operation. Wemco flotation cells are installed. Rougher and cleaner concentrate report as final concentrate and the various froth products being recycled.

The use of the limited capacity within the cleaner circuit will result in improved recoveries but could tend to produce a lower quality ........