Abstract

Matchless is one of a number of copper-zinc sulfide deposits associated with the Matchless amphibolite belt in the upper Proterozoic Damara orogen. Within the belt, amphibolite is interlayered with quartz-mica schist, believed to represent flysch-type sediment deposited during the initial opening of a Damaran ocean. Two major deformation events involving isoclinal folding and thrusting are recognized. D 1 produced a pronounced layering which is everywhere parallel to the bedding. F 2 folds deform the earlier S 1 cleavage and layering. The dominant structure is an S 2 -spaced cleavage which strikes east-northeast and dips to the northwest. Major porphyroblastic mineral growth took place subsequent to D 2 at lower amphibolite facies metamorphic grade. A minor D 3 deformation event produced crenulation and fracture cleavages.The copper-zinc deposits occur within a stratiform zone of sulfide-bearing rocks. Massive sulfide ore occupies three shoots plunging northwest parallel to the F 2 fold axes. The footwall to the ore shoots consists of pyrite-bearing quartz-muscovite schist with interlayered bands of massive pyrite-quartz-muscovite rock and a distinctive biotite-bearing marker schist. In the hanging wall are chloritic schists, with variable proportions of quartz, ankerite, and calcic amphibole, bands of magnetite quartzite, and amphibolite.

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