Gwayi River Mine, Dete (Dett), Hwange District, Matabeleland North, Zimbabwei

Regional Level Types
Gwayi River Mine	Mine
Dete (Dett)	- not defined -
Hwange District	District
Matabeleland North	Province
Zimbabwe	Country

The Gwayi River Mine (formerly Gwaai River Mine) was operated by Messina (Transvaal) Development Corporation from 1970 until 1975, when the mine was closed for economic reasons.

The mine property which occupies an area of about 7km² immediately south of the confluence of the Gwaii and Siamakuli rivers, lies some 14km north of the main Victoria Falls road. There is a narrow tarmac connecting link.

The mineralized host rocks (metapsammites with stratabound chalcopyrite and pyrite mineralization, oxidized to malachite and azurite) are surrounded by amphibolites and calc-silicate-bearing marbles. The mineralized horizons are interpreted as interflow sedimentary rocks intercalated with mafic metavolcanic rocks (now represented by amphibolites).

There are three ore shoots (Adder, Puff Adder, and Gaboon Viper) in the form of flattened elongated cigar-shaped pods which are restricted to the noses of fold closures, and which plunge parallel to co-linear F1 and F3 deformation structures. There are two types of copper occurrences: in shears and fractures within tremolite and cummingtonite-anthophyllite amphibolites which are enclosed in hornblende amphibolites; and in siliceous and calc-silicate-rich interflow metasedimentary intercalations in the mafic sequence. The sulfides consist of chalcopyrite, pyrite, and pyrrhotite. At the Adder shoot at Gwayi River Mine, coarse sulfides occur together with vein quartz filling breccias in calc-silicate rocks in the nose of a fold. At the Puff Adder shaft, finely disseminated sulfide mineralization is localized within bands of vitreous grey quartzite grading outwards into cross-cutting veins and blows of quartz.

The orebody varies from 3 to 15m in width and has a strike length of 400m, and a down-dip extent of at least 470m. The ores appear to have been metamorphosed at high grades and then retrograded. Ore minerals are intergrown with metamorphic minerals like almandine garnet, cordierite, tremolite, cummingtonite, anthophyllite, and epidote. The ores predate regional granitic events, as they are cut by undeformed granitic intrusions. Bahnemann and Lockett (1979) attributed the origin of the Gwayi River Mine mineralization to “syngenetic volcanic exhalations next to fumarolic vents” or to a “final degassing of the lava pile”. These volcanogenic deposits were then metamorphosed, stretched and deformed into the shape seen today.

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References