Otjihase, Matchless


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The Matchless & Otjihase deposits are two of a series of small and one larger Cu-Zn-Ag deposit hosted by the Matchless Amphibolite Belt on the south eastern margin of the main Damaran/Katangan Rift in Namibia.

These deposits are hosted by the Kuiseb Formation, a monotonous sequence of quartz-plagioclase-mica schists with lesser quartzites and minor graphitic schist and are found in close proximity to a conspicuous 0.5 to 3 km wide and 350 km long linear, composite amphibolite band extending in a general SW-NE direction from south of Walvis Bay near the Atlantic coastline to a point 110 km to the NE of Windhoek where it passes below the Kalahari sands.

All of the deposits and occurrences of the belt are found within several hundred metres below this amphibolitic horizon, the Matchless Amphibolite, within the 10 000 m thick Kuiseb Formation. The Kuiseb Formation occupies the upper portion of the Damara Supergroup which is of Neoproterozoic to Cambrian in age.

The more significant ore deposits are Otjihase (possible totalling up to 40 Mt @ 2.6% Cu, 10 g/t Ag, 21% S in a number of orebodies) and Matchless (4 Mt @ 2.2% Cu). Two smaller occurrences, Gorob and Hope are also known within the same belt, as are a number of other prospects and sub-economic accumulations.

The Otjihase deposit itself is located 18 km NE of Windhoek, the capital of Namibia. It comprises a series of parallel strongly elongated shoots, the chief of which is developed over a lateral extent of up to 7 km, is around 250 m wide and averages 5 m in thickness. This and the other parallel shoots, for their whole length, follow tight monoclinal flexures, which are parallel to regional F2 fold axes. The ore shoot terminates abruptly in the axial region of the monocline, while having a grade boundary on the other side. The sulphides, which comprises mainly pyrite and chalcopyrite with associated magnetite, exhibit structural remobilisation textures and occur as zones of magnetite-quartzite-sulphide, massive sulphide with lessser magnetite and semi-massive to disseminated sulphides across the narrow dimension of each lens.

The Matchless deposit is 30 km SW of Windhoek also occurs as three NW plunging elongate shoots which parallel F2 fold axes and are intimately associated with the Matchless Amphibolite. The ore lenses, which are around 3 m thick, have strike lengths of approximately 120 m and have been followed down plunge for at least 600 m, are developed within a conformable zone of sulphide bearing rocks. The footwall to the shoots consists of pyritic quartz-muscovite-schist with interlayered bands of massive pyrite-quartz-muscovite and a distinctive biotitic marker schist. The hangingwall contains chloritic schists with variable amounts of quartz, ankerite and calcic amphibole as well as bands of magnetite quartzite and amphibolite.

For more detail consult the reference(s) listed below.

The most recent source geological information used to prepare this summary was dated: 1992.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
   Selected References:
Adamson R G, Teichmann R F H  1986 - The Matchless cupreous pyrite deposit, south west Africa/Namibia: in Anhaeusser C R, Maske S, (Eds.), 1986 Mineral Deposits of South Africa Geol. Soc. South Africa, Johannesburg   v2 pp 1755-1760
Breitkopf J H, Maiden K J  1988 - Tectonic setting of the Matchless Belt Pyritic Copper deposits, Namibia: in    Econ. Geol.   v83 pp 710-723
Klemd R, Maiden K J, Okrusch M  1987 - The Matchless Copper deposit, South West Africa/Namibia: A deformed and metamorphosed massive Sulfide deposit: in    Econ. Geol.   v82 pp 587-599
Klemd R, Maiden K J, Okrusch M, Richter P  1989 - Geochemistry of the Matchless metamorphosed massive Sulfide deposit, South West Africa/Namibia: wall-rock alteration during submarine ore-forming processes: in    Econ. Geol.   v84 pp 603-617

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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