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 (Fig.3.3.1_1). 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.

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.

Ore from the Otjihase mine will be crushed underground through a jaw crusher to a nominal 150mm prior to being transported to surface, to a 3,200t receiving bin at the plant. Ore from Matchless mine is road hauled and similarly crushed at Otjihase ahead of the same receiving bin. The receiving bin has 14 off take points feeding a single conveyor.

The different ore types are stored separately in the receiving bin with no mention or plan of blending practice. The ore ratio is expected to be 35,000t:15,000t Otjihase: Matchless, and some consideration may be given to blending is based on the flotation response and the quantity of ores available.

The crusher plant consists of a primary grizzly with oversize being crushed in the 5½ft Standard Symons secondary crusher. The grizzly fines are screened on a vibrating screen to reduce the load on the tertiary crusher. The screen oversize and the secondary crusher product are conveyed to a surge bin then to the tertiary screen and tertiary crusher, a 5½ft Shorthead Symons. The screen undersize is directed to three fine ore silos whilst the screen oversize is crushed in the tertiary crusher and recycled back to the screens where the fines are removed. This is a very conventional crusher circuit. The final crusher product size will nominally be 100% passing 10mm.

Crushed product is conveyed to three mill feed silos each with 1,100t capacity. Crusher plant spares observed include mantles, bowls and screen parts. The condition of this circuit is considered to be reasonable but some maintenance and checking is necessary before commissioning. The dust extraction system at the crusher plant should be checked prior to the planned start-up, particularly all ducting.

Milling plant
The milling circuit consists of three closed circuits Vecor 10ft x 12ft ball mills with 20” hydrocyclones. Mill motors are 670Kw with 11Kv supply. Historically the grind was approximately 80% passing 250 micron. The milling circuit configuration is very conventional, and considered suitable for the type of ore to be processed. The three old Ramsey weightometers measuring mill feed tonnages will be replaced with new process control units which may be configured to give some degree of automation and control.

The ball mills operate with rubber liners and lifters with 56mm plus 64mm cylpebs as grinding media. While the mills have not been run over the past year, barring gear units have been used to turn the mills to ensure that bearings and lubrication are functional. As with other parts of the plant, all equipment should be checked, cleaned and motors turned before startup.

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 ........