Base Metals

Copper

Most of Namibia’s known copper and lead deposits are Tsumeb-type, Besshi-type or Red Bed-type (Base Metal Map (93KB)). Currently the only copper producer in Namibia is Ongopolo Mining and Processing Ltd. It mines Besshi-type cupriferous pyrite ore from the recently opened Matchless Mine Western Extension (1.35 Mt ore at 2.12% copper), situated some 30 km west of Windhoek, and from the Otjihase Mine (Resource of 12 Mt at a grade of 1.9% copper), situated 30 km east of Windhoek. Copper concentrate is transported via rail from the Otjihase Mine to the Tsumeb Smelter to produce blister copper. Other Tsumeb-type copper-lead deposits investigated during recent years include the new Tsumeb West Mine (grade/tonnage), Asis Far West Mine (Inferred mineral resource of 3 Mt at a grade of 2.5% copper), Khusib Springs Mine (245 000 t at a grade of 4.5% copper, 1.15% lead, 1.43% zinc and 350 ppm silver) and the Tschudi deposit (Resource of 43 Mt at a grade of 0.85% copper, stripping ratio 1:6) all situated on the carbonate platform of the Otavi Mountainland. The copper smelter in Tsumeb receives copper concentrate not only from Ongopolo-owned mines in Namibia, but from Zambia, Chile, South Africa and Zimbabwe. Potential exists to identify and develop new deposits as well as to re-evaluate known deposits.

Tsumeb Smelter

Examples of known deposit that could be re-evaluated include Ongombo (reserve of 3.29 Mt at 1.9% Cu), Onganja (300 000 t at 2% Cu), Klein Aub (7.5 Mt at 2% Cu and 50 ppm Ag) and the Witvlei copper deposits at Malachite Pan (2.98 Mt at 2.1% Cu; zone of supergene enrichment est. 280 000 t at 2.76% Cu) and Witvlei Pos (9.5 Mt at 1.5% Cu).

The Haib copper porphyry deposit has been evaluated by several exploration and mining companies; more recently MinTeck of South Africa have conducted tests on the ore to extract copper by chemical and bacteria leaching processes. The Haib deposit contains an ore reserve of some 400 Mt at an average copper grade of 0.33%.

Zinc

Economic deposits of zinc are mined in southern Namibia. The two zinc mines that are operational in southern Namibia are the Rosh Pinah Mine owned by Kumba Resources Pty Ltd (95%) and PE Minerals (5%), and the Skorpion Mine owned wholly by AMBASE (Namibia) (Pty) Ltd. Southern Namibia, in particular the Gariep Belt is highly prospective for Rosh Pinah-type massive sulphide deposits, as well as for Skorpion-type non-sulphide zinc deposits. Major exploration companies, such as BHP Billiton, Teck Cominco Ltd and AMBASE, are actively exploring in southern Namibia in order to delineate further economic zinc deposits.

The Rosh Pinah Mine has proven reserves of 6 Mt at an average grade of 8.68% zinc and 2.25% lead, and exploration is currently underway to delineate additional reserves. Rosh Pinah produces some 70,000 tonnes of zinc concentrate and approximately 28,000 tonnes of lead annually. The zinc concentrate is sent to ZINCOR’s electrolytical refinery in Springs, South Africa, for processing. The Skorpion deposit has a resource of 24.6 Mt at an average grade of about 10.6 % Zn, mineable by the conventional open pit method. It is anticipated that by the end of 2005 Skorpion will be producing some 150 000 tonnes of refined zinc per year.

Commodity in tonnes/year	2000	2001	2002	2003	2004
Cu Conc. 30% (t)	19,095	45,368	63,997	64,869	44,606
Cu blister 99% pure (t)	5,082	27,015	17,850	26,306
Cu contained metal (t)	-	12,594	-	-	-
Zn Conc. 52% (t)	73,535	70,610	77,587	107,920	123,272
Zn contained metal (t)	39,137	31,803	42,685	60,500	-
Refined Zn	-	-	35	47,436	119,205
Pb Conc. 30% (t)	20,665	26,182	24,140	31,453	27,188
Pb contained metal (t)	11,114	13,025	13,190	18,782	-
Pb refined (t)	-	-	-	-	-

Additional information on Base Metals

Rosh Pinah

Largely stratiform Zn-Pb (Cu-Ag) sulphide mineralization of the Rosh Pinah-type occurs in the continental Port Nolloth Zone of the Gariep Belt. The Rosh Pinah ore body shows substantial hydrothermal vent-related carbonatization and brecciation in the footwall, indicating a proximal position of the exhalative facies. Textural, isotopic and geochemical evidence indicates replacement of the host sediments during early diagenesis, during which feldspathic arenite was silicified and limestone dolomitized by an overall reducing, mineralizing fluid. Starvation of the Rosh Pinah graben during a climatically controlled Neoproterozoic sea level drop is proposed to have created the necessary redox barrier for massive sulphide precipitation to occur near the sediment-seawater interface. Rosh Pinah lies close to the vent system and later underwent upper greenschist facies metamorphism.

Skorpion

Skorpion Zinc is a non-sulphide zinc deposit owned by Ambase Exploration (Namibia) (Pty) Ltd, which is located in the southern part of the Namib Desert, approximately 40 km north of the Orange River. The so-called Skorpion belt of zinc-lead copper-barite prospects is hosted by volcano-sedimentary rocks of the Gariep Complex, northwest of Rosh Pinah. The Skorpion zinc deposit represents an initial rift phase with crustal extension and strong vertical tectonics, associated with subaqueous, mixed siliciclastic-carbonate sedimentation. It is a shallow subhorizontal body comprising secondary zinc silicate and carbonate minerals like smithsonite, hemimorphite, hydrozincite and sauconite.

Skorpion Open-Pit Mine

Supergene ore-forming processes at Skorpion appear to involve wallrock-replacement as well as saprolitic accumulations and minor in-situ replacement. Mining is open cast-type and the unusual zinc-silicate and carbonate ore is treated by direct acid leach, solid liquid separation, a unique zinc solvent extraction and electro-winning to produce high-purity zinc on site at low cost.

Haib copper porphyry

Porphyry copper mineralization is present at the Haib and Lorelei prospects in southern Namibia. The Haib copper porphyry-type deposit encompasses the three characteristic alteration assemblages typically associated with copper porphyry type deposits:

1) potassic zone – hydrothermal formed potassium feldspar,
2) phyllitic zone – plagioclase is completely replaced by sericite and quartz; pyrite is a major rock-forming mineral and
3) propylitic zone – mass chlorite, epidote and calcite – abundant pyrite. Sulphide minerals include chalcopyrite, bornite, chalcocite, covellite, tennantite, molybdenite, galena, sphalerite, pyrite, arsenopyrite and pyrrhotite. The supergene enrich cap has been eroded, leaving a relatively low grade copper deposit.

Haib Deposit